Title: Clutch protection system
Abstract: A system for protecting the clutch of a vehicle from a harmful operating state. Included in the clutch protection system are means for monitoring the operating state of the clutch, along with means for estimating the amount of energy being dissipated by the clutch. A control unit compares the estimated amount of energy dissipated by the clutch to one or more predetermined threshold energy levels. One or more actions designed to reduce the amount of energy dissipated by the clutch are initiated when the estimated amount of energy dissipated by the clutch exceeds the one or more predetermined thresholds.
Patent Number: 6,943,676 Issued on 09/13/2005 to Mack
| Inventors:
|
Mack; William J. (Kalamazoo, MI)
|
| Assignee:
|
Eaton Corporation (Cleveland, OH)
|
| Appl. No.:
|
261741 |
| Filed:
|
October 1, 2002 |
| Current U.S. Class: |
340/453; 340/454; 340/456; 340/679; 477/76; 477/98; 477/125 |
| Intern'l Class: |
B60Q 001/00 |
| Field of Search: |
340/453,454,456,679
180/197,278
477/76,98,116,125,39,62,64,174
701/34,54,62,65
|
References Cited [Referenced By]
U.S. Patent Documents
| 4295551 | Oct., 1981 | Zimmermann et al.
| |
| 4502579 | Mar., 1985 | Makita.
| |
| 4651142 | Mar., 1987 | Klatt.
| |
| 4722426 | Feb., 1988 | Bellanger.
| |
| 5337866 | Aug., 1994 | Stürmer et al.
| |
| 5982280 | Nov., 1999 | Fahrbach et al.
| |
| 6040768 | Mar., 2000 | Drexl.
| |
| 6095946 | Aug., 2000 | Maguire et al.
| |
| Foreign Patent Documents |
| 100 32 906 | Mar., 2001 | DE.
| |
| 0 482 691 | Apr., 1992 | EP.
| |
| 0 493 840 | Jul., 1992 | EP.
| |
| 1 225 362 | Jul., 2002 | EP.
| |
| 2 327 248 | Jan., 1999 | GB.
| |
| WO 01/7254/6 | Oct., 2001 | WO.
| |
| WO02/25133 | Mar., 2002 | WO.
| |
Other References
International Search Report (3 pages—WO 02 25133 not included with this
IDS due to the fact that it was previously provided).
Derwent English Abstract for DE 100 32 906 A1.
Delphion English Abstract for EP 0 493 840 A2.
|
Primary Examiner: Nguyen; Hung
Attorney, Agent or Firm: Rader, Fishman & Grauer PLLC
Claims
1. A clutch protection system, comprising:
a monitor for monitoring an operating state of a clutch connecting a motor to
a system of gears;
an estimator for estimating an amount of energy dissipated by said clutch;
a comparator that compares said estimated amount of energy dissipated by said
clutch to at least one predetermined threshold energy level; and
a control unit wherein said control unit initiates one or more actions to automatically
reduce said amount of energy dissipated by said clutch when said estimated amount
of energy dissipated by said clutch exceeds said predetermined threshold energy
level, wherein the greater said estimated amount of energy dissipated by said clutch
exceeds said predetermined threshold energy level, the faster said control unit
initiates one or more actions.
2. The clutch protection system according to claim 1, wherein said one or more
actions initiated by said control unit comprise an issuance of a warning signal.
3. The clutch protection system according to claim 2, wherein said warning signal
comprises a visual warning.
4. The clutch protection system according to claim 2, wherein said warning signal
comprises an audible warning.
5. The clutch protection system according to claim 1, wherein said one or more
actions initiated by said control unit comprise reducing an amount of torque transmitted
through said clutch.
6. The clutch protection system according to claim 5, wherein said reduction
in torque continues at a predetermined rate until said estimated amount of energy
dissipated by said clutch falls below said predetermined threshold energy level.
7. The clutch protection system according to claim 1, wherein said one or more
actions initiated by said control unit comprise increasing a rate of clutch engagement.
8. The clutch protection system according to claim 7, wherein an amount of said
increase in rate of clutch engagement is dependent upon said estimated amount of
energy dissipated by said clutch.
9. The clutch protection system according to claim 7, wherein said one or more
actions initiated by said control unit further comprise an issuance of a warning signal.
10. The clutch protection system according to claim 1, wherein said one or more
actions initiated by said control unit comprise automatically shifting from a higher
gear to a lower gear within said system of gears.
11. The clutch protection system according to claim 10, wherein said shifting
from said higher gear to said lower gear is prevented if said shifting would cause
said motor to enter an over-speed condition.
12. The clutch protection system according to claim 1, further comprising a counter
for recording how many times said estimated amount of energy dissipated by said
clutch exceeds said predetermined threshold energy level.
13. The clutch protection system according to claim 1, wherein said control unit
tracks an amount of time that said estimated amount of energy dissipated by said
clutch exceeds said predetermined threshold energy level.
14. The clutch protection system according to claim 1, wherein said monitor,
estimator and comparator comprise part of said control unit.
15. The clutch protection system according to claim 1, further comprising at
least one datalink connecting said monitor to one or more sensors incorporated
into said clutch.
16. A method of protecting a clutch mechanism connecting a motor to a gear system,
comprising the steps of:
monitoring an operating state of said clutch mechanism;
estimating an amount of energy dissipated by said clutch mechanism;
determining when said estimated amount of energy dissipated by said clutch mechanism
exceeds a predetermined threshold energy level; and
initiating one or more actions designed to automatically lower said estimated
amount of energy dissipated by said clutch mechanism when it is determined that
said estimated amount of energy dissipated by said clutch mechanism exceeds said
predetermined threshold energy level, wherein the greater said estimated amount
of energy dissipated by said clutch exceeds said predetermined threshold energy
level, the faster said one or more actions are initiated.
17. The method according to claim 16, wherein said one or more actions include
issuing a warning signal.
18. The method according to claim 16, wherein said one or more actions include
decreasing an amount of torque applied to said clutch mechanism.
19. The method according to claim 18, wherein said torque is decreased at a predetermined
rate until said estimated amount of energy dissipated by said clutch mechanism
fails below said threshold energy level.
20. The method according to claim 16, wherein said one or more actions comprise
increasing a rate of clutch engagement.
21. The method according to claim 16, wherein said one or more actions comprise
automatically shifting from a higher gear to a lower gear within said gear system
when said gear system is under manual control.
22. A system for protecting a clutch of an automobile against damage when said
clutch is in an engaged to lockup state and an accelerator pedal is at least partially
depressed, comprising:
a monitor for monitoring said clutch and a motor of said automobile;
an estimator for estimating an amount of energy dissipated by said clutch;
a comparator that compares said estimated amount of energy dissipated by said
clutch to at least a first predetermined threshold energy level and a second predetermined
threshold energy level; and
a control unit that i) issues a warning signal when said estimated amount of
energy dissipated by said clutch exceeds said first predetermined threshold energy
level, and ii) automatically increases a rate at which said clutch engages said
motor when said estimated amount of energy dissipated by said clutch exceeds said
second predetermined threshold energy level, wherein said increase of said rate
of clutch engagement is determined by said estimated amount of energy dissipated
by said clutch, with a greater amount of exceedence of the second predetermined
threshold energy level by said clutch resulting in a greater rate of clutch engagement.
23. The system according to claim 22, wherein said warning signal continues to
be issued until at least one of the following occurs:
a) said estimated amount of energy dissipated by said clutch decreases below
said first predetermined threshold energy level by at least a predetermined amount;
b) said clutch is placed into a different operating state; and
c) said estimated amount of energy dissipated by said clutch decreases and continues
to decrease for at least a predetermined amount of time.
24. The system according to claim 22, wherein the greater said estimated amount
of energy dissipated by said clutch exceeds said second predetermined threshold
energy level, the faster said rate in which said clutch engages said motor.
25. A system for protecting a clutch of an automobile against damage when said
clutch is in an engage to lockup state, an accelerator pedal is at least partially
depressed, and a transmission system of said automobile is in a manual mode of
operation, comprising:
a monitor for monitoring said clutch and a motor of said automobile;
an estimator for estimating an amount of energy dissipated by said clutch;
a comparator that compares said estimated amount of energy dissipated by said
clutch to at least a first predetermined threshold and a second predetermined threshold;
and
a control unit that i) issues a warning signal when said estimated amount of
energy dissipated by said clutch exceeds said first predetermined threshold level,
and ii) automatically downshifts said transmission system to a lower gear when
a) said estimated amount of energy dissipated by said clutch exceeds said second
predetermined threshold and b) said downshifting will not result in said motor
entering an over-speed condition.
26. The system according to claim 25, wherein said downshifting of said transmission
system also occurs when a) an acceleration of an input shaft of said transmission
system falls below a predetermined threshold for a predetermined amount of time,
and b) said downshifting will not result in said engine entering an over-speed condition.
27. The system according to claim 25, wherein said warning signal continues to
be issued until at least one of the following occurs:
a) said estimated amount of energy dissipated by said clutch decreases below
said first predetermined threshold level by at least a predetermined amount;
b) said clutch is placed into a different operating state; and
c) said estimated amount of energy dissipated by said clutch decreases and continues
to decrease for at least a predetermined amount of time.
28. The system according to claim 25, wherein the greater said estimated amount
of energy dissipated by said clutch exceeds said second predetermined threshold
energy level, the faster said control unit downshifts said transmission system
to a lower gear.
Description
FIELD OF THE INVENTION
The present invention relates to a clutch of a vehicle, and, more specifically,
a system and method for protecting the clutch from excessive wear and potential damage.
BACKGROUND OF THE INVENTION
A clutch is a mechanism designed to connect or disconnect power from one working
part to another. In terms of vehicles, the clutch is used to transmit power from
the motor to the drive train, and to disengage the motor and transmission when
shifting gears.
In its simplest form, the clutch can be considered as comprising two plates that
can be selectively placed up against one another. One plate (flywheel) is attached
to and rotated by a motor. A counterpart plate (clutch plate) attaches to a system
of gears that one wants to run with the power of the motor. To transfer the power
of the motor to the gears, the clutch plate is pushed up against the rotating flywheel.
Upon being pressed up against one another, the two plates don't initially spin
in synch. Instead, the driving plate (flywheel) rotates at a faster rate than the
receiving plate (clutch plate) as the receiving plate slips against the driving
plate as it rotates. This spinning of the two plates at different speeds is what
results in wear and damage to the clutch. However, if the two plates become fully
engaged, or locked together, frictional forces are strong enough to cause the two
plates to spin at the same speed and no wear occurs.
During the runnning of a vehicle, there are several operating states where
the clutch is neither fully engaged or disengaged. Instead, the clutch "slips"
excessively, resulting in premature wear and damage to the clutch. In response,
the Applicant has developed a clutch protector system that detects and resolves
these operating states, thereby reducing the amount of wear or damage subjected
upon the clutch.
SUMMARY OF THE INVENTION
The present invention relates to a vehicle clutch protection system, comprising
a monitor for monitoring an operating state of a clutch, an estimator for estimating
an amount of energy dissipated by the clutch, and a comparator that compares the
estimated amount of dissipated clutch energy to at least one predetermined threshold
energy levels. If the estimated amount of dissipated clutch energy exceeds a predetermined
threshold energy level, a control unit initiates one or more actions to reduce
the amount of energy dissipated by the clutch.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified illustration of a clutch protection system according
to one embodiment of the present invention.
FIG. 2 is a simplified flow chart depicting the basic steps taken by the clutch
protection system according to one embodiment while the clutch is in an urge to
move state.
FIG. 3 is a simplified flow chart depicting the basic steps taken by the clutch
protection system according to one embodiment while the clutch is in an engage
to lockup state.
FIG. 4 is a simplified flow chart depicting the basic steps taken by the clutch
protection system according to a second embodiment while the clutch is in an engage
to lockup state.
FIG. 5 is a simplified flow chart depicting the basic steps taken by the clutch
protection system according to one embodiment while the clutch is under severe
abuse by an operator.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 depicts the vehicle clutch protection system
10 according to one
embodiment of the present invention. A transmission
32, such as an automatic
transmission, is selectively engaged to a motor
30 by means of clutch
20.
Transmission
32 may be any type of transmission typically found in a vehicle,
for example, the Autoshift™ system made by Eaton Corporation. Additionally,
transmission
32 may have the capability to be placed in a manual operating
mode, thereby allowing the operator of a vehicle to determine when transmission
32 will actually shift to another gear. Motor
30 can be any type
of motor used to propel a vehicle. Typically this will be an internal combustion
engine, although other types of motors, such as an electric motor, may just as
easily be used with the present invention. In the illustrated embodiment, clutch
20 is a wet clutch, which typically relies on oil not only as a lubricant
but also as a coolant. Of course, the clutch protection system can be adapted to
work with different types of clutches. A microprocessor-based control unit
40
is connected via data links
50 to motor
30, transmission
32
and clutch
20. Data links
50 may be comprised of a variety of types
of data communication methods. One example of a data link
50, provided for
illustrative purposes, is the J1939 link used for communication of data, such as
current motor speed and torque, between a motor and a transmission system. Additionally,
although only one control unit
40 is shown in FIG. 1, the invention is not
limited to this. For example, the system may be designed to include two controllers,
such as one in the interior of a vehicle allowing for operator input, while the
second is located with the transmission system for control over clutch functions.
In simple terms, the clutch protection system assess whether a vehicle clutch
may be subject to possible damage, due to excessive slipping of the clutch, by
calculating an estimated amount of energy dissipated by the clutch, and comparing
this estimated amount of energy to one or more predetermined thresholds. Once one
of these thresholds is surpassed by the estimated amount of energy being dissipated
by the clutch, the system initiates one or more actions designed to place the clutch
back into a safe operating state.
The detailed operation of the clutch protection system according to one embodiment
of the present invention will now be discussed. Based on various operating parameters,
control unit
40 is able to calculate an estimated amount of energy being
dissipated by clutch
20. For illustrative purposes, consider the following
equations, which provide one example of how to calculate an estimated amount of
energy dissipated by clutch
20 for every period of time delta T, such as,
for example, every 10 milliseconds.
Where:
- Speed unit is rpm
- Torque unit is lb-ft
- Clutch Power unit is BTU/sec
- Clutch Energy unit is BTU
- Cooling Rate=Predetermined rate at which clutch transfers energy to
its surroundings
- 7426=Constant based on the above units
Initially, clutch power=0 and clutch energy is set at a predetermined
default value. Subsequently, control unit 40 repeatedly calculates an estimated
clutch energy, for example, every 10 milliseconds, and updates the previous values
based on the most recent calculations.
The system continues to calculate and revise the estimated amount of energy dissipated
by the clutch as long as the clutch is in a state that allows for excessive slippage,
thereby leading to premature wear and possible damage to the clutch. This excessive
slippage of the clutch is characteristic of both an i) urge to move state, and
an ii) engage to lockup state. Except for transient conditions, the clutch at all
other times should be in either a fully engaged or fully disengaged state, thereby
precluding possible damage due to excessive slippage.
To illustrate an urge to move state, consider the following example. A driver
stops his or her vehicle, engages the parking brake, and then exits while leaving
the motor running. However, the driver forgets to place the transmission into neutral,
thereby disengaging the clutch from the engine. As such, the running motor
30
is constantly urging the vehicle to move forward by transferring its energy through
clutch
20 and the gears of transmission system
32, to ultimately
cause the tires to rotate. However, as the parking brake is engaged, the tires
are prevented from rolling. This prevents the gears of transmission system
32
from rotating. As a result, clutch
20 is placed in a constant state of slipping,
leading to excessive wear and damage.
Similarly, clutch
20 is subject to excessive slipping when placed
in a typical engage to lockup state. For example, consider an operator of a truck
that is carrying a heavy load and is stopped on a steep incline. However, instead
of using the brakes, the driver prevents the truck from rolling back down the hill
by engaging the clutch
20 and throttling the engine
30 just enough
to prevent the truck from moving. This places the clutch
20 in a constant
state of slipping as it continuously attempts to engage and lockup with the engine
30.
According to the present embodiment, vehicle clutch
20 is protected
from residing in an urge to move state for to long, thereby minimizing the exposure
of clutch
20 to a potentially damaging operating state, by comparing the
estimated amount of energy dissipated by clutch
20 to a clutch abuse threshold.
FIG. 2 depicts a simple flow chart of the steps taken by clutch protection system
10 of the current embodiment. First, a monitor
42, typically associated
as a component of a control unit
40 with appropriate input being received
from the necessary components by way of data link
50, determines whether
clutch
20 is in an urge to move state
200. The system then uses an
estimator
44, also typically part of control unit
40, to estimate
the amount of energy being dissipated by clutch
20. A comparator
46,
also typically part of control unit
40, then determines whether the estimated
amount of energy being dissipated by clutch
20 is above a predetermined
abuse threshold level
210, indicating that there is potential for damage
to the clutch
20. If the estimated amount of energy is not above the threshold
level, the system ends its current line of inquiry and returns to the beginning
of the routine. However, if the estimated amount of clutch energy exceeds the clutch
abuse threshold
210, the protection system
10 will begin to decrease
the amount of "urge to move" torque
230 generated by motor
30 and
applied to clutch
20. According to the present embodiment, this decrease
in torque is carried out at a constant rate, such as, for example, 15 lb-ft/sec,
although other constant rates, or even variable rates, could also be readily used.
This decrease in torque continues until the estimated clutch energy dissipated
by clutch
20 no longer exceeds the clutch abuse threshold level
210.
Additionally, once the estimated amount of clutch energy initially
exceeds the predetermined clutch abuse threshold at step
210, an optional
clutch abuse counter (not shown in FIG. 1) may be incremented by one in order to
keep track of the number of times this situation occurs. An abuse timer (also not
shown in FIG. 1) may also be activated at step
220, allowing the clutch
protection system
10 to keep track of the amount of time clutch
20
resides in the potentially harmful urge to move state.
FIG. 3 depicts a simple flow chart depicting the steps taken by clutch protection
system
10 according to a first embodiment that deals with a vehicle whose
clutch is in an engage to lockup state. Unlike the analysis performed during the
urge to move state, both a clutch abuse threshold and clutch damage threshold are
utilized in the process of determining what actions, if any, need to be taken to
protect clutch
20 from damage. In accordance with the present embodiment,
the clutch abuse threshold is lower in value than the clutch damage threshold,
both of which are predetermined based on the specific type of clutch installed
in the vehicle.
Monitor
42 first determines whether clutch
20 is in an engage
to lockup state at step
300. In addition, monitor
42 determines whether
the acceleration pedal of the vehicle is at least partially depressed (step
302),
indicating that the driver of the vehicle is currently seeking to obtain more power
from motor
30 beyond that produced when in a basic idle state. If these
two requirements are satisfied, comparator
46 then determines whether the
estimated amount of energy dissipated by clutch
20 exceeds a predetermined
clutch abuse threshold (step
304). If any of the above steps result in a
negative answer, the current inquiry process is ended and allowed to start all
over. If it is determined that the estimated amount of energy dissipated by clutch
20 does exceed the clutch abuse threshold (step
304), it must be
determined whether the clutch damage threshold is also exceeded (step
306).
Assuming that the estimated amount of clutch energy exceeds the clutch abuse
threshold, but not the higher clutch damage threshold, the inquiry process continues
on with step
308. There an abuse counter is incremented, allowing the system
to keep track of the number of times the clutch
20 has been placed in a
potentially damaging state. The system also records, by means of a timer (not shown
in FIG.
1), a relative abuse time stamp for the current event, and also
accumulates the amount of time the clutch spends exceeding the clutch abuse threshold
but below the clutch damage threshold. A warning signal is also issued at step
310. The warning signal is directed to the operator of the vehicle, and
is intended to alert the operator to the fact that he or she is abusing the clutch
20. The warning signal can be either visual, auditory, or both. One example
of a warning signal, provided for illustrative purposes, is the sounding of a continuous
1 second alert followed by 1 second of silence. Furthermore, a display on the vehicle
dashboard can, for example, flash a letter "C" followed by the letter "A" to indicate
that a clutch abuse state is currently present.
The system
10 will continue to issue the warning signal until one of three
possible conditions occurs (step
312). First, the warning signal will subside
if the estimated clutch energy level falls below a clutch abuse signal-off threshold.
This threshold can be defined in numerous ways. For instance, the signal-off threshold
can simply be made equal to the clutch abuse threshold. However, this can result
in repeated warning signals if the average amount of energy dissipated by clutch
20 is close to the energy level that represents the clutch abuse threshold.
Expected fluctuations in the clutch energy level can lead to a frequent and repeated
triggering and silencing of the warning signal as the clutch energy level repeatedly
exceeds the threshold by a brief amount as the energy level routinely fluctuates.
To rectify this condition, the signal-off threshold level can be set at a lower
level than that of the clutch abuse threshold. Accordingly, the warning signal
will issue once the clutch energy level exceeds the abuse threshold, and it will
not subside until the clutch energy level drops below the abuse threshold by a
predetermined amount. Once subsided, the warning signal will not issue again until
the clutch energy level rises enough to once again exceed the clutch abuse threshold.
The second condition that will turn off the warning signal is a change in state
of clutch
20. For example, if the vehicle operator increases the speed of
the motor, thereby increasing the amount of torque applied to the clutch, or alternatively,
the transmission system
32 triggers a shift in gears.
The third condition that will terminate the clutch abuse warning signal is if
the system, by means of control unit
40, senses that the vehicle operator
has made a conscious effort to stop abusing the clutch
20. Various criteria
can be used to define this condition, for example, the control unit
40 detecting
a consecutive decrease in estimated clutch energy for a minimum duration of time,
such as, for illustrative purposes, 100 milliseconds.
If none of the above three conditions represented by step
312 are satisfied,
the warning signal will continue to be issued. Furthermore, the system also checks
on whether there has been an increase in the amount of estimated energy dissipated
by the clutch (step
313). If there has been an increase in the amount of
estimated energy, the system returns to step
306 to determine whether the
amount of estimated energy now exceeds the clutch damage threshold.
If any of the above three conditions represented by step
312 are satisfied,
the warning signal is turned off at step
314. However, the clutch protection
system
10 does not reset itself yet. Instead, the estimated amount of energy
dissipated by clutch
20 is once again calculated and compared to the clutch
abuse threshold at step
316. If the estimated clutch energy level exceeds
the abuse threshold level, and continues to consecutively increase for a predetermined
duration of time, the process will return to step
310 and the warning signal
will once again be issued. Alternatively, if the estimated clutch energy level
decreases below a clutch abuse reset threshold (step
318), for example,
a predetermined amount below the clutch abuse threshold, the inquiry process is
ended and the system resets.
If it is determined that clutch
20 is in an engage to lockup state (step
300), that the acceleration pedal is at least partially depressed (step
302), and the estimated clutch energy level exceeds not only the clutch
abuse threshold (step
304), but also exceeds the higher clutch damage threshold
(step
306), the system continues on to step
330. Note that steps
304 and
306 could be exchanged with one another, such that the system
determines whether an estimated amount of energy dissipated by clutch
20
exceeds the clutch damage threshold first before determining whether the clutch
abuse threshold is exceeded. Similar to step
308, step
330 involves
the incrementing of a clutch damage counter and the generation of a relative damage
time stamp that allows the system to determine how much time clutch
20 is
subject to damage.
At this point, it can be determined that the clutch
20 is in a typical
engage to lockup state, such as when an operator has stopped his or her truck on
an incline and is using the clutch instead of the brakes to keep the truck from
rolling backwards. In this instance, the control unit
40 attempts to cause
clutch
20 to fully engage the motor
30, thereby preventing any more
damage caused by excess slipping of the clutch
20. This is accomplished
by increasing the rate at which clutch
20 engages motor
30 (step
334). As the rate of clutch engagement increases, the chance of clutch damage
due to slippage decreases. The end result is the full engagement of clutch
20,
leading the truck or vehicle to begin to accelerate.
According to a further embodiment, the increased rate of clutch engagement
is not a constant, but instead variable depending on how much energy is being dissipated
by clutch
20. The greater the amount of energy in clutch
20, the
farther the clutch damage threshold is exceeded, resulting in an increased rate
of damage to clutch
20. Accordingly, it would seem preferable to have clutch
20 fully engage the motor
30 as fast as possible, thereby minimizing
the amount of time that clutch
20 is excessively slipping and subject to
damage. However, in contrast, one would also prefer to have clutch
20 slowly
engage motor
30, thereby providing more time for the operator of the vehicle
or truck to react to the fact that their vehicle is beginning to accelerate.
To best satisfy both of the above requirements, the system is designed so that
the farther an estimated clutch energy exceeds the predetermined clutch damage
threshold level, the faster the rate of clutch engagement. Accordingly, if a clutch
energy level only mildly exceeds the clutch damage threshold, the rate of clutch
engagement will increase modestly. In contrast, if the clutch energy level significantly
exceeds the clutch damage threshold, rate of clutch engagement will be increased
significantly as well.
While the system is increasing the rate of clutch engagement in order to prevent
any further damage to the clutch
20 due to slippage, the control unit also
initiates a warning signal to the vehicle operator (step
336) to alert them
to the fact that the clutch is in the process of fully engaging motor
30.
Similar to before, the warning signal can be any type of auditory warning, visual
warning, or combination thereof, as long as it alerts the vehicle operator to the
clutch engagement and provides them with time to react properly.
The warning signal continues to sound and/or display until the estimated energy
being dissipated by clutch
20 drops below a damage signal-off threshold,
which is set at a predetermined amount below the clutch damage threshold. If the
clutch energy level does drop below this damage signal-off threshold, the warning
signal ceases, as indicated in step
362.
Similar to the abuse reset threshold of step
318, a damage reset threshold
is employed at step
364, keeping the current process active until the estimated
clutch energy level drops significantly enough to end the process (step
380)
and reset the system.
In another embodiment of the invention, the vehicle employing the clutch protection
system of the present invention may have a transmission system that allows an operator
to place it in a manual mode of operation. Thus, instead of the transmission system
32 automatically shifting gears without input from the vehicle operator,
the operator controls when a shift in gears is to occur. However, a disadvantage
of this manual shifting-based system is that it allows for another unique situation
where clutch
20 can be placed in a damaging operating state.
Some transmission systems
32 have the ability to be placed in a manual
mode of operation where the vehicle operator determines when the transmission system
32 shifts between gears. However, in this mode, the vehicle can be driven
in a manner as to place clutch
20 in another type of engage to lockup state.
In this situation, however, instead of an operator trying to hold a vehicle stationary
on an incline by means of the clutch
20, the vehicle is moving. Consider
the following example, provided for illustrative purposes. An operator has his
or her vehicle currently in a high gear and is approaching a red light. The operator
begins to slow the vehicle down without disengaging the clutch
20 or downshifting
the transmission system
32. Due to the slow speed, clutch
20 begins
to unlock or disengage. At this point in time, the light turns green and the operator
begins to accelerate their vehicle, still without shifting to a lower gear. This
causes the clutch to excessively slip. Unlike the previous engage to lockup situation,
one doesn't want to engage the clutch while the transmission system
32 remains
in a high gear as it can cause the motor
30 to stall. The clutch protection
system according to the current embodiment solves the above problem by temporarily
overriding the manual shift mode and causing the transmission system
32
to automatically shift to a lower gear.
As depicted in FIG. 4, if the clutch is in an engage to lockup state (step
400),
and the accelerator pedal of the vehicle is at least partially depressed (step
402), the system then determines whether the acceleration of the vehicle
corresponds to the amount of acceleration that should correspond to the current
position of the depressed accelerator pedal (step
404). Additionally, the
system also checks to see if the amount of estimated energy dissipated by the clutch
exceeds the clutch damage threshold (step
404). If the vehicles actual acceleration
does not correspond to the acceleration expected, or if the estimated clutch energy
does exceed the clutch damage threshold, the system increments a counter and generates
a time stamp (step
430) as done in previous embodiments. It must also check
to confirm that the transmission system
32 has been placed in a manual operating
mode (step
432). Upon confirmation of this condition, the control unit
40
determines whether the current gear the vehicle is in is the gear used to start
the vehicle (step
442). This check is necessary to assure that a lower gear
is available to shift down into. Assuming that the vehicle is not in one of the
lower starting gears, the control unit
40 causes the transmission system
32 to down shift. At the same time, a warning signal similar to that of
step
336 is initiated. Steps
460-
480 are then repeated in
the same fashion as they were carried out in the engage to lockup situation involving
a transmission system
32 not placed into a manual operating mode.
According to another embodiment of the present invention, the clutch protection
system
10 will attempt to prevent damage to clutch
20 caused by a
vehicle operator severely abusing the clutch
20. As depicted in the flow
chart of FIG. 5, this mode of operation requires three conditions. First, the clutch
protection system
10, by means of the control unit
40, must detect
the accelerator pedal being at least partially depressed (step
500), indicating
that the vehicle operator is seeking increased power from motor
30. Additionally,
it must also determine that a braking system of the vehicle, such as, for example,
the service brakes or parking brakes, are currently engaged (step
502),
indicating that the operator is accelerating and braking the vehicle at the same
time. Upon meeting these two conditions, the system assesses whether the estimated
amount of energy dissipated by clutch
20 exceeds the clutch damage threshold.
The system then proceeds to increase the rate of clutch engagement just as it did
in step
334 of FIG. 3, except in this embodiment, an additional predetermined
amount, for example, 30 lb-ft/sec, is added upon to the prior amount that the rate
of clutch engagement was increased by in the prior embodiment. Thus, if the rate
of clutch engagement was increased by 20 lb-ft/sec at step
334, the rate
of clutch engagement in this embodiment would be increased by 50 lb-ft/sec. All
further steps depicted in FIG. 5 are the same as those that follow step
334
of FIG. 3, and will not be discussed in any further detail.
In a further embodiment of the Applicant's invention, the clutch protection system
10 is designed to provide limited functions in the event of a data link
failure. For example, if the J1939 data link between the control unit
40
and motor
30 were to fail, the system will continue to estimate the amount
of energy dissipated by the clutch
20, initiate warning signals when appropriate,
and record abuse/damage information provided by the appropriate counters and timers.
However, as the clutch protection system
10 can no longer deliver control
data to motor
30, activities such as decreasing the amount of torque applied
to clutch
20 will any longer be capable.
In many of the embodiments disclosed above, the clutch protection system issues
a warning signal as one type of action designed to reduce the amount of energy
dissipated by clutch
20. It was previously emphasized that these warning
signals (i.e. steps
314,
336,
446 and
508) can be either
auditory, visual, or a combination thereof. Furthermore, these warning signals
can all be of the same type of alert, or, if desired, they can be different so
as to be distinguishable from one another. For example, it may be desirable to
have the warning signal (step
310) issued upon a clutch energy exceeding
the clutch abuse threshold to be audibly or visually different than the warning
signal (step
336) issued when the system is increasing the rate of clutch engagement.
While the invention has been specifically described in connection with certain
specific embodiments thereof, it is to be understood that this is by way of illustration
and not of limitation, and the scope of the appended claims should be construed
as broadly as the prior art will permit.
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