Clutch control method for vehicle

Abstract

The present invention relates to a clutch control method for a vehicle, comprising: when a predetermined first reference time period has passed in a micro-slip state of the clutch, the clutch torque is increased to a refilling execution torque at a predetermined first slope by a controller; when the clutch torque reaches the refilling execution torque, the clutch torque is increased to the refilling torque at a predetermined second slope by the controller to start refilling a pressure chamber of a hydraulically driven actuator with oil in an oil storage tank; and during a predetermined second reference time period, the clutch torque is maintained at the refilling torque by the controller.

Description

Technical Field

[0001] The present invention relates to a technology for controlling a clutch to selectively perform power transmission between an engine and a transmission. Background Art

[0002] The descriptions in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] The vehicle's transmission receives power from the engine, converts the received power into power suitable for driving the wheels, and outputs the converted power.

[0004] The transmission is connected to the engine via a clutch. When the clutch is in a disconnected state, the transmission performs a gear shift operation. When the gear shift operation is completed, the transmission is connected to the engine again.

[0005] A normally closed clutch that normally maintains power transmission from the engine to the transmission is mainly used. When an operating force is input to the clutch by the driver's operation of a clutch pedal or an operation of an actuator, the clutch is disconnected, and the power input to the transmission is interrupted.

[0006] Recently, a technology has been developed in which a controller operates the above clutch using an actuator or the like according to the running condition of a vehicle without the driver operating a clutch pedal, thereby improving driving convenience.

[0007] In order for a controller to control a clutch, it is desirable to accurately determine the actual torque transfer characteristics of the clutch according to the stroke of an actuator controlled by the controller.

[0008] That is, the controller stores data on a torque stroke curve (TS curve) showing the torque transfer characteristics of the clutch depending on the stroke of the actuator. The controller calculates the actuator stroke for achieving the desired clutch torque and controls the actuator based on this, thereby indirectly controlling the clutch.

[0009] However, the characteristics of the clutch tend to vary significantly depending on the temperature of the clutch. Therefore, it is desirable to frequently update the TS curve through learning in order to achieve a desired shift operation feel through appropriate operation of the clutch, thereby improving the driving performance of the vehicle.

[0010] In particular, in some cases, a hydraulic actuator is used to operate the clutch by the controller. When the oil generating the hydraulic pressure is continuously pressurized, the characteristics of the actuator change as the temperature of the oil increases, which causes the torque transmission characteristics of the clutch depending on the stroke of the actuator to change.

[0011] Hereinafter, the above-mentioned TS curve is referred to as "clutch characteristics". Summary of the invention

[0012] The present invention is directed to providing a clutch control method for a vehicle, which, in a structure in which a hydraulic actuator is used to control the clutch, reduces or minimizes changes in the physical properties of the oil used to generate hydraulic pressure (such as an increase in the temperature of the oil), thereby continuously maintaining and ensuring more precise control of the clutch.

[0013] In one form of the present invention, a clutch control method for a vehicle includes: when a predetermined first reference time period has passed in a micro-slip state of the clutch, increasing the clutch torque to a refilling execution torque at a predetermined first slope through a controller; when the clutch torque reaches the refilling execution torque, increasing the clutch torque to the refilling torque at a predetermined second slope through a controller to start refilling a pressure chamber of a hydraulically driven actuator with oil in an oil reservoir; and maintaining the clutch torque at the refilling torque during a predetermined second reference time period.

[0014] The controller may learn the clutch characteristics for a predetermined first reference period of time in which the micro-slip state is maintained.

[0015] The method also includes: after maintaining the clutch torque as a refill torque during a predetermined second reference time period, reducing the clutch torque through a controller to cause the clutch to form a micro-slip state; and while maintaining the micro-slip state after reducing the clutch torque, confirming the clutch characteristics learned during a predetermined first reference time period through a controller.

[0016] The method may further include: after confirming the learned clutch characteristics, increasing the clutch torque to the refilling execution torque again at a predetermined first slope by the controller; and increasing the clutch torque to the refilling torque at a predetermined second slope by the controller.

[0017] The predetermined first slope may be set to be smaller than the predetermined second slope, and the predetermined second slope may be set to a maximum possible value.

[0018] The refill actuation torque may be set to a clutch torque value corresponding to a position of the piston just before the pressure chamber is communicated with the reservoir, in which position the piston is arranged to generate pressure in the pressure chamber of the hydraulically driven actuator.

[0019] The refill torque may be set to a clutch torque value corresponding to a position of the piston where the piston fully opens the passage communicating with the reservoir.

[0020] Further areas of applicability will become apparent from the description provided herein.It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to make the present invention easier to understand, various embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0022] Figure 1 is a diagram showing an engagement state of a clutch in a clutch system of a vehicle according to one form of the present invention;

[0023] Figure 2 It is shown Figure 1 A diagram showing a disengaged state of a clutch in the clutch system shown;

[0024] Figure 3 is a flow chart showing a clutch control method for a vehicle according to another form of the present invention; and

[0025] Figure 4 is a graph showing a clutch control method for a vehicle according to one form of the present invention.

[0026] The drawings herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. DETAILED DESCRIPTION

[0027] The following description is merely exemplary in nature and is not intended to limit the invention, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate the same or corresponding parts and features.

[0028] Hereinafter, a clutch control method for a vehicle according to an exemplary form of the present invention will be described with reference to the accompanying drawings.

[0029] Reference Figure 1 and Figure 2 The clutch system of the vehicle applicable to the present invention is configured so that when the controller CLR receives the operating state of the shift lever TL and the operating state of the clutch pedal CP and controls the hydraulically driven actuator PD to generate hydraulic pressure, the generated hydraulic pressure is transmitted to the hydraulically driven actuator PP installed on the clutch CL to drive the clutch CL.

[0030] Alternatively, the controller CLR may be configured not to receive the operation state of the clutch pedal CP alone, but to control the clutch CL by determining the driving condition of the vehicle during the shift operation.

[0031] The clutch CL is a normally closed type, basically forming Figure 1 Therefore, the power from the engine is continuously input to the transmission through the clutch CL.

[0032] To disconnect the clutch CL, the controller CLR drives the hydraulic actuator PD so that the piston 3 in the pressure chamber 1 is Figure 2As a result, hydraulic pressure is generated in the oil in the pressure chamber 1, and the hydraulic pressure is transmitted to the hydraulically driven actuator PP through the pressure pipe 5, thereby opening the clutch CL.

[0033] Therefore, as the stroke of the piston 3 increases, the hydraulic pressure in the pressure chamber 1 increases, and accordingly, the clutch torque of the clutch CL decreases.

[0034] In order to reengage the open clutch CL, the piston 3 is returned, thereby reducing the pressure in the pressure chamber 1 .

[0035] When piston 3 returns to Figure 1 In the state shown, the pressure chamber 1 is communicated with the oil storage tank 7 , and the oil stored in the oil storage tank 7 enters the pressure chamber 1 and mixes with the oil in the pressure chamber 1 , thereby reducing the temperature of the oil in the pressure chamber 1 .

[0036] Reference Figure 3 and Figure 4 In one form of the present invention, a clutch control method for a vehicle includes: a step (S10) of increasing the clutch torque to a refilling execution torque at a predetermined first slope by a controller CLR when a predetermined first reference time period has passed in a micro-slip state of the clutch; a step (S20) of increasing the clutch torque to a refilling execution torque at a predetermined second slope by the controller CLR when the clutch torque reaches the refilling execution torque to start refilling a pressure chamber 1 of a hydraulically driven actuator PD with oil in an oil reservoir 7; and a step (S30) of maintaining the clutch torque at the refilling torque during a predetermined second reference time period.

[0037] That is, when the micro-slip state of the clutch CL is maintained for a predetermined time or longer, the controller CLR increases the clutch torque so as to refill the pressure chamber 1 with the oil in the oil tank 7, thereby lowering the temperature of the oil in the pressure chamber 1, and further reducing or minimizing the change in the clutch characteristics caused by the increase in the oil temperature.

[0038] Therefore, if the variation in clutch characteristics is reduced or minimized by appropriately lowering the temperature of oil generating hydraulic pressure, the controller CLR can control the clutch CL more accurately and stably.

[0039] The controller CLR determines a condition under which the micro slip can be performed. When determining that the micro slip can be performed, the controller CLR creates a micro slip state during a first reference period of time in which the micro slip state is maintained and learns clutch characteristics.

[0040] The condition under which micro-slip can be performed may be set in consideration of a state of the vehicle in which the engaged state of the clutch CL can be stably maintained for a predetermined period of time or longer, such as a state in which a shift operation is not performed or a state in which the vehicle does not start moving.

[0041] The micro-slip state is a state in which a slight slip of about 20 RPM occurs in the clutch CL. The slip is the speed difference between the opposite sides of the clutch CL, that is, between the engine and the input shaft of the transmission.

[0042] In the micro-slip state, the engine torque in this state can be considered to be substantially the same as the torque transmitted through the clutch. Therefore, in a vehicle where it is impossible to directly measure the clutch torque, learning is performed in a manner to form a micro-slip state of the clutch, using the engine torque in this state as the clutch torque, and applying the stroke of the actuator that forms the micro-slip state to the clutch torque.

[0043] Here, the actuator stroke can be considered as Figure 1 and Figure 2 The stroke of the piston 3 is shown.

[0044] It may be considered that a time period for learning the clutch characteristics through a large number of experiments is set as the first reference time period. For example, the first reference time period may be set to 30 ms.

[0045] The refilling execution torque is set to a clutch torque value corresponding to the position of the piston 3 at which pressure is generated in the pressure chamber 1 of the hydraulic drive actuator PD just before the pressure chamber 1 is communicated with the oil reservoir 7. The refilling torque is set to a clutch torque value corresponding to the position of the piston 3 at which the piston 3 fully opens the passage communicating with the oil reservoir 7.

[0046] That is, Figure 1 As shown, the clutch torque value corresponding to the position of the piston 3 in which the piston 3 fully opens the orifice 9, which is a passage connecting the pressure chamber 1 to the oil reservoir 7, is equal to the refilling torque. The clutch torque value corresponding to the position of the piston 3 just before opening the orifice 9 is equal to the refilling actuation torque. Figure 1 The position shown is slightly offset to the left.

[0047] In one form, the first slope of the clutch torque increase is set to be less than the second slope, and the second slope is set to a maximum possible value.

[0048] When the clutch torque increases to the refilling execution torque, the speed at which the clutch torque increases is relatively high. This is to quickly execute the control process of the present invention to prepare for the case where the driver operates the clutch pedal CP again. When the clutch torque reaches the refilling execution torque, the piston 3 returns at a second slope greater than the first slope so as to more smoothly refill the oil in the oil reservoir 7 into the pressure chamber 1.

[0049] In one form, the second slope may be set to a value for returning the piston 3 at the maximum possible speed of the hydraulically driven actuator PD.

[0050] The second reference time period may be set based on a time period for sufficiently lowering the temperature of the oil in the pressure chamber by the above-mentioned refilling operation. For example, the second reference time period may be set to 100 ms.

[0051] The clutch control method also includes: after maintaining the clutch torque as the refilling torque during the second reference time period, reducing the clutch torque through the controller CLR so that the clutch forms a micro-slip state again (S40); and while maintaining the micro-slip state after reducing the clutch torque, confirming the clutch characteristics learned during the first reference time period through the controller CLR (S50).

[0052] That is, the controller CLR determines whether the clutch characteristics learned during the first reference period are appropriate through the above steps.

[0053] The clutch control method further includes: after confirming the learned clutch characteristics, the step of increasing the clutch torque to the refilling execution torque again at the first slope by the controller CLR (S60); and the step of increasing the clutch torque to the refilling torque at the second slope by the controller CLR (S70).

[0054] When it is determined that the learned clutch characteristics are appropriate, the controller CLR increases the clutch torque to the refill torque again to continuously maintain the full engagement state of the clutch CL until a different situation occurs (such as the driver's operation of the clutch pedal CP), and terminates the control process of the present invention.

[0055] When it is determined that the clutch characteristics learned during the first reference period are not appropriate, the controller CLR maintains the second micro-slip state for a longer period of time and learns the clutch characteristics again.

[0056] As is apparent from the above description, according to the present invention, in the case of controlling the clutch using the hydraulic actuator, a pressure chamber configured in the actuator for generating hydraulic pressure is communicated with the oil reservoir so that the oil in the oil reservoir is refilled in the pressure chamber. Therefore, changes in the physical properties of the oil (such as an increase in the temperature of the oil) can be reduced or minimized, and thus more precise control of the clutch can be continuously maintained and ensured.

[0057] Although exemplary modes of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention.

Claims

1. A clutch control method for a vehicle, wherein include: When a predetermined first reference period of time has passed in a micro-slip state of the clutch, the clutch torque is increased to a refilling execution torque at a predetermined first slope by a controller; When the clutch torque reaches the refilling execution torque, the controller increases the clutch torque to the refilling torque at a predetermined second slope to start refilling the pressure chamber of the hydraulically driven actuator with the oil in the oil reservoir; During a predetermined second reference period, the clutch torque is maintained at the refill torque by the controller.

2. The clutch control method for a vehicle according to claim 1, further comprising: include: During a predetermined first reference period in which the micro-slip state is maintained, the clutch characteristics are learned by the controller.

3. The clutch control method for a vehicle according to claim 2, further comprising: include: After maintaining the clutch torque at the refill torque during a predetermined second reference period, reducing the clutch torque by a controller to bring the clutch into a micro-slip state; While maintaining the micro-slip state after reducing the clutch torque, the clutch characteristics learned during the predetermined first reference period are confirmed by the controller.

4. The clutch control method for a vehicle according to claim 3, further comprising: include: After confirming the learned clutch characteristics, the clutch torque is increased again to the refilling execution torque at a predetermined first slope by the controller; The clutch torque is increased by the controller to a refill torque at a predetermined second slope.

5. The clutch control method for a vehicle according to claim 1, in, The predetermined first slope is set to be smaller than the predetermined second slope; The predetermined second slope is set to a maximum possible value.

6. The clutch control method for a vehicle according to claim 1, in, The refill actuation torque is a clutch torque value corresponding to a position of the piston just before the pressure chamber is communicated with the reservoir, at which position the piston is arranged to generate pressure in the pressure chamber of the hydraulically driven actuator.

7. The clutch control method for a vehicle according to claim 6, in, The refill torque is a clutch torque value corresponding to a position of the piston at which the piston fully opens the passage communicating with the oil reservoir.

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