GB2514839B

GB2514839B - Clutch pedal torque limiting

Info

Publication number: GB2514839B
Application number: GB1310179.5A
Authority: GB
Inventors: Philemon Petridis Themi; Hesketh David; Halleron Ian; Dashwood Crisp Nicholas
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2013-06-07
Filing date: 2013-06-07
Publication date: 2019-06-12
Anticipated expiration: 2033-06-07
Also published as: CN104235343A; GB201310179D0; GB2514839A; CN104235343B; DE102014210540A1

Description

Clutch Pedal Torque Limiting

This invention relates to a method and/or system for adjusting the torque input to a clutch from an engine of a vehicle, and particularly but not exclusively, relates to a method for limiting the torque input to the clutch when it is determined that there is slippage between the clutch plates.

Background

Slippage between clutch plates causes heat to be generated. Prolonged slippage and excessive heat generation causes a reduction in clutch life and can cause damage to the clutch and/or flywheel resulting in reduced ability to transmit torque across the clutch and even failure of the clutch.

Resting a foot on the clutch pedal whilst driving (riding the clutch) reduces the clamp force at the clutch plates thereby reducing the torque capacity of the clutch. Clutch slip can be induced with a combination of reduced clamp force and sufficient engine torque, with the most severe conditions being high-speed, high-load driving scenarios. If slip occurs under these conditions, for example whilst driving up an incline and/or towing, a large amount of heat can be generated. If the heat generated exceeds the maximum operating temperature of the clutch for a prolonged period of time then permanent clutch damage will be caused.

Resting a foot on the clutch pedal also increases the wear rate of the thrust bearing. These consequences are undesirable for customers whilst manufacturers suffer in terms of both warranty costs and reputation.

Studies have shown that a significant number of drivers rest their foot on the clutch pedal whilst driving. Clutch slip is however a necessary part of operation during launches and gear changes. It is seen as advantageous, therefore, to provide a method of limiting the slippage of the clutch plates when it is determined that slippage is occurring as a result of the driver resting their foot on the clutch whilst driving.

Statement of invention

According to a first aspect of the present invention there is provided a method of adjusting the torque input to a clutch from a motor of a vehicle, wherein the method comprises adjusting the torque when: the position of the clutch is within a predetermined range of positions; the clutch is held within the predetermined range of positions for a first predetermined time; and the gearbox of the vehicle maintains a selected gear for a second predetermined time.

The method may further comprise providing a signal to adjust the torque input to the clutch from the motor upon: determining the position of the clutch and comparing the position of the clutch against the predetermined range of positions; determining a first time period for which the clutch is held at the position and comparing the first time period against the first predetermined time; and determining a second time period for which a gearbox of the vehicle maintains a selected gear and comparing the second time period against the second predetermined time.

The method may further comprise providing the signal to adjust the torque input to the clutch from the motor in the event that: the position of the clutch is outside the predetermined range of positions; the first time period is greater than the first predetermined time; and the second time period is greater than the second predetermined time.

The method may further comprise determining a set of operational variables for the clutch and comparing the set of operational variables to predetermined values for the set of operational variables. Determining the set of operational variables for the clutch and comparing the set of operational variables to threshold values may involve: determining the input torque to the clutch from the motor and comparing the input torque against a predetermined input torque; and/or computing a difference in rotational speeds across the clutch and comparing the difference in rotational speeds to a predetermined difference in rotational speeds.

The method may further comprise providing the signal to adjust the torque input to the clutch from the motor in the event that: the input torque to the clutch from the motor is greater than the predetermined input torque or difference in rotational speeds across the clutch is greater than the predetermined difference in rotational speeds. The difference in rotational speeds across the clutch may be computed by comparing the rotational speed of the engine to the rotational speed of the wheels, the gearbox input shaft or to the rotational speed of any other appropriate component of the vehicle. The rotational speed of the gearbox input shaft may be determined using a rotational speed sensor. The selected gear of the gearbox may be determined using a selected gear sensor and /or gearbox input shaft sensor.

The signal to adjust the torque input to the clutch may be configured to limit the torque input to the clutch from the motor.

The position of the clutch may correlate to the position of a clutch pedal, a clutch slave cylinder and/or a pressure in a clutch line. The position of the clutch may correlate to a clutch static torque capacity and/or a clutch dynamic torque capacity. The predetermined range of positions of the clutch may correlate to a predetermined range of positions of the clutch pedal, a predetermined range of positions of the clutch slave cylinder and/or a predetermined range of pressures in the clutch line. The predetermined range of positions of the clutch pedal may be approximately 5 to 35 percent of the maximum travel of the clutch pedal from an un-depressed position.

The method may further comprise determining the amount of thermal energy generated by the clutch and the amount of thermal energy dissipated by the clutch.

The method may further comprise computing an operating temperature of the clutch, the operating temperature being equal to the amount of thermal energy generated by the clutch minus the thermal energy dissipated by the clutch and comparing the operating temperature to a predetermined operating temperature.

The method may further comprise providing the signal to adjust the torque input to the clutch from the motor when the operating temperature approaches, is greater than or is equal to the predetermined operating temperature.

The method may further comprise overriding the signal to limit the torque input to the clutch from the motor during scenarios that require a substantial input torque.

The method may further comprise providing an indication to an operator. The indication may comprise a visual, an aural, a vibrotactile and/or any similar mechanical-dynamic alert system. The indication may signal that the operator is resting a foot on the clutch pedal. A system, for example a controller, may be configured to carry out any of the above-mentioned methods.

List of Figures

For a better understanding of the present disclosure and to show more clearly how it may be carried into effect, reference will now be made by way of example to the accompanying drawing, in which:

Figure 1 is a flow chart detailing a method of adjusting the torque input to a clutch when it is determined that a driver is resting a foot on the clutch pedal.

Detailed description

Clutch slip may be moderated by adjusting the torque input to the clutch. A method of adjusting the torque input to the clutch from a motor of a vehicle is shown in figure 1. The torque input to the clutch is adjusted when: the position of the clutch is within a predetermined range of positions; the clutch is held within the predetermined range of positions for a first predetermined time; and the gearbox of the vehicle maintains a selected gear for a second predetermined time.

The method comprises three criteria that must be satisfied in order for the torque to be adjusted: criterion 1 relates to the position of the clutch; criterion 2 relates to the time period for which the clutch has been held at that position; and criterion 3 relates to the time period for which a gearbox of the vehicle has maintained a selected gear.

Specifically: criterion 1 comprises determining the position of the clutch and comparing the position of the clutch against the predetermined range of positions; criterion 2 comprises determining a first time period for which the clutch is held at the position and comparing the first time period against the first predetermined time; and criterion 3 comprises determining a second time period for which the gearbox of the vehicle maintains the selected gear and comparing the second time period against the second predetermined time. The selected gear of the gearbox may be determined using a selected gear sensor and /or gearbox input shaft sensor.

Depending on the outcomes of the comparisons, the method provides a signal A to adjust the torque input to the clutch from the motor. Signal A may be configured to limit the torque input to the clutch from the motor.

In a first embodiment of the present invention, signal A is provided to limit the torque input to the clutch from the motor in the event that criteria 1 to 3 are satisfied, wherein: for criterion 1, the position of the clutch is outside the predetermined time range of positions; for criterion 2, the first time period is greater than the first predetermined time; and for criterion 3, the second time period is greater than the second predetermined time.

Criteria 1, 2 and 3 may be satisfied in any order or in parallel with one another. Similarly, one or more of criteria 1, 2 and 3 may be monitored continuously or the determinations and/or comparisons may be made at an appropriate frequency.

The position of the clutch may correlate to the position of a clutch pedal, wherein the predetermined range of the clutch correlates to a predetermined range of positions of the clutch pedal. The predetermined range of positions of the clutch pedal may be approximately 5 to 35 percent of the maximum travel of the clutch pedal from an un-depressed position, which is indicative of a driver resting their foot on the clutch whilst driving.

The position of the clutch may correlate to the position of a clutch slave cylinder and/or a pressure in a clutch line, wherein the predetermined range of the clutch correlates to the, a predetermined range of positions of the clutch slave cylinder and/or a predetermined range of pressures in the clutch line. The position of the clutch may correlate to a clutch static torque capacity and/or a clutch dynamic torque capacity.

Signal A may be provided therefore when it has been determined that the driver is resting their foot on the clutch pedal for longer than the first predetermined period of time whilst driving in a single gear for longer than the second predetermined period of time.

The method may further comprise criterion 4 (not shown) that may be used as a check to determine if the clutch is actually slipping upon satisfaction of criteria 1, 2 and 3. Criterion 4 involves determining a set of operational variables for the clutch and comparing the set of operational variables to predetermined values for the set of operational variables.

Specifically, criterion 4 comprises determining the input torque to the clutch from the motor and comparing the input torque against a predetermined input torque and/or computing a difference in rotational speeds across the clutch and comparing the difference in rotational speeds to a predetermined difference in rotational speeds. The clutch is determined to be slipping if the input torque to the clutch from the motor is greater than the predetermined input torque and/or the difference in rotational speeds across the clutch is greater than the predetermined difference in rotational speeds.

The difference in rotational speeds across the clutch may be computed by comparing the rotational speed of the engine to the rotational speed of another appropriate component of the vehicle. For example, rotational speeds across the clutch may be computed by comparing wheel speed and engine speed, since these signals are readily available in modern vehicles. Alternatively, rotational speeds across the clutch may be computed by comparing gearbox input shaft speed and engine speed, which may provide a more accurate difference in rotational speeds across the clutch if the appropriate sensors are fitted to the vehicle. The rotational speed of the gearbox input shaft may be determined using a rotational speed sensor.

Criterion 4 is satisfied if: the input torque to the clutch from the motor is greater than the predetermined input torque; and/or the difference in rotational speeds across the clutch is greater than the predetermined difference in rotational speeds.

In a second embodiment of the present invention, signal A is provided to limit the torque input to the clutch from the motor in the event that criteria 1 to 4 are satisfied.

The method may further comprise criterion 5 (not shown), which involves determining the amount of thermal energy generated by the clutch and the amount of thermal energy dissipated by the clutch. The operating temperature of the clutch is equal to the amount of thermal energy generated by the clutch minus the thermal energy dissipated by the clutch and comparing the operating temperature to a threshold value for the operating temperature.

Criterion 5 is satisfied if: the operating temperature approaches, is greater than or is equal to a predetermined operating temperature. in a third embodiment of the present invention, signal A is provided to limit the torque input to the clutch from the motor in the event that criteria 1 to 3 are satisfied; and criteria 4 and/or 5 are satisfied.

The method may further comprise criterion 6 (not shown) that determines if the clutch is slipping owing to necessary inputs from the driver, for example, when the accelerator pedal is substantially depressed, i.e. approximately 90 to 100 % of travel, during an overtaking manoeuvre. Limiting the torque under such circumstances may endanger the occupants of the vehicle.

In a fourth embodiment of the invention, if it is determined that the torque input to the clutch from the motor is due to any scenario that requires substantial input torque, then signal A may be overridden and the torque input to the dutch from the motor may not limited.

The method may further comprise, depending upon the outcomes of the comparison and/or determinations of criteria 1 to 6, providing an indication to the driver of the vehicle that the clutch is slipping. As part of the Human-Machine Interface (HMI) strategy, the indication may be given via duster messages and sounds, vibrations, or similar mechanical dynamic indicators induced at the dutch pedal. This may serve to alert the driver that they are resting a foot on the dutch pedal and may encourage them to take action in order to avoid damaging the dutch.

If it has been detected that a driver is resting their foot on the dutch pedal and the requisite above-motioned criteria have been satisfied, a potential implementation approach would be first to request that the driver fully releases their foot from the dutch pedal via the HMI. If this request is ignored the engine torque may be limited to protect the dutch. Additionally, this could be accompanied by appropriate HMI warnings. A dutch protection strategy may be implemented in a vehicle’s software using existing sensor sets that are available in modern vehicles. Such a solution may be utilised either to reduce warranty claims on existing dutches and/or to reduce manufacturing costs of the clutch due to reduced durability cycle requirements. Customers may benefit by experiencing fewer instances of reduced wheel torque due to premature dutch wear and also fewer dutch failures. Additionally, the wear rate of the thrust bearing may be reduced, which may benefit manufactures and/or suppliers with reduced warranty costs and improved quality reputation.

Additionally, a clutch protection strategy as disclosed in the present invention may help reduce clutch wear and failure rates during high torque manoeuvres, where the clutch clamp force may be at the upper limit and any reduction in clamp force due to resting on the clutch pedal during such manoeuvres may exacerbate clutch slip and wear issues.

Claims

1. A method of adjusting the torque input to a clutch from a motor of a vehicle, wherein the method comprises adjusting the torque when: the position of the clutch is within a predetermined range of positions; the clutch is held within the predetermined range of positions for a first predetermined time; and the gearbox of the vehicle maintains a selected gear for a second predetermined time.

2. A method according to claim 1, wherein the method further comprises providing a signal to adjust the torque input to the clutch from the motor upon: determining the position of the clutch and comparing the position of the clutch against the predetermined range of positions; determining a first time period for which the clutch is held at the position and comparing the first time period against the first predetermined time; and determining a second time period for which a gearbox of the vehicle maintains a selected gear and comparing the second time period against the second predetermined time.

3. A method according to claim 2, wherein the method further comprises, providing the signal to adjust the torque input to the clutch from the motor in the event that: the position of the clutch is outside the predetermined range of positions; the first time period is greater than the first predetermined time; and the second time period is greater than the second predetermined time.

4. A method according to claim 3, wherein the method further comprises determining a set of operational variables for the clutch and comparing the set of operational variables to predetermined values for the set of operational variables.

5. A method according to claim 4, wherein determining the set of operational variables for the clutch and comparing the set of operational variables to predetermined values involves: determining the input torque to the clutch from the motor and comparing the input torque against a predetermined input torque.

6. A method according to claim 4 or 5, wherein determining the set of operational variables for the clutch and comparing the set of operational variables to predetermined values involves: computing a difference in rotational speeds across the clutch and comparing the difference in rotational speeds to a predetermined difference in rotational speeds.

7. A method according to claim 5 or 6, wherein the method further comprises, providing the signal to adjust the torque input to the clutch from the motor in the event that: the input torque to the clutch from the motor is greater than the predetermined input torque or difference in rotational speeds across the clutch is greater than the predetermined difference in rotational speeds.

8. A method according to claim 7, wherein the difference in rotational speeds across the clutch is computed by comparing the rotational speed of the engine to the rotational speed of the wheels, the gearbox input shaft or to the rotational speed of any other appropriate component of the vehicle.

9. A method according to any of the preceding claims, wherein the signal is configured to limit the torque input to the clutch from the motor.

10. A method according to any of the preceding claims, wherein the position of the clutch correlates to one or more selected from: the position of a clutch pedal; the position of a clutch slave cylinder; and a pressure in a clutch line.

11. A method according to any of the preceding claims, wherein the position of the clutch correlates to one or more selected from: a clutch static torque capacity; and a clutch dynamic torque capacity.

12. A method according to claim 11, wherein the predetermined range of positions of the clutch correlates to one or more selected from: a predetermined range of positions of the clutch pedal; a predetermined range of positions of the clutch slave cylinder; a predetermined range of pressures in the clutch line; a predetermined range of the clutch static torque capacity; and a predetermined range of the clutch dynamic torque capacity.

13. A method according to claim 12, wherein the predetermined range of positions of the clutch pedal is approximately 5 to 35 percent of the maximum travel of the clutch pedal from an un-depressed position.

14. A method according to any of the preceding claims, the method further comprising, determining the amount of thermal energy generated by the clutch and the amount of thermal energy dissipated by the clutch.

15. A method according to claim 14, the method further comprising computing an operating temperature of the clutch, the operating temperature being equal to the amount of thermal energy generated by the clutch minus the thermal energy dissipated by the clutch and comparing the operating temperature to a predetermined operating temperature.

16. A method according to claim 15, the method further comprising providing the signal to adjust the torque input to the clutch from the motor when the operating temperature approaches, is greater than or is equal to the predetermined operating temperature.

17. A method according to any of the preceding claims, the method further comprising, overriding the signal to limit the torque input to the clutch from the motor during scenarios that require a substantial input torque.

18. A method according to any of the preceding claims, the method further comprising, providing an indication to an operator.

19. A method according to claim 18, wherein the indication comprises one or more selected from: a visual alert; an aural alert; a vibrotactile alert and a mechanical-dynamic alert.

20. A method according to claim 18 or 19, wherein the indication signals that the operator is resting a foot on the clutch pedal.

21. A system configured to carry out a method according to any of the preceding claims.