JP2012052575A - Automatic transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device capable of reducing the frequency of forcible release of a friction clutch and starting acceleration promptly when an accelerator pedal is stepped down during deceleration or after deceleration.SOLUTION: An automatic transmission system includes: the friction clutch 2 disposed between an internal combustion engine 1 and an input shaft 5 of a transmission; and a transmission controller 31, which controls the engagement and release of the friction clutch 2. The transmission controller 31 performs: control of a slip which is caused by a difference in rotations between the input side and output side of the friction clutch 2 according to the driving conditions of a vehicle; and a clutch forcible release control, which forcibly releases the friction clutch 2 according to the deceleration speed of the vehicle to prevent engine stall. In this system, the transmission controller 31 eases a threshold value of the deceleration speed for determining whether the clutch forcible release control should be performed or not during the deceleration while the slip control is being performed than when the slip control is not performed.

Description

  The present invention relates to a control device that controls engagement / release of a friction clutch provided between an internal combustion engine and a transmission.

  2. Description of the Related Art A vehicle is known that includes a friction clutch between an internal combustion engine and a transmission, and controls the engagement / release operation of the friction clutch with a controller.

  For example, in Patent Document 1, the torque of the internal combustion engine is smoothly transmitted to the transmission by performing so-called slip control in which the friction clutch is slipped without being completely engaged at the time of starting, and according to the vehicle speed, deceleration, etc. at the time of deceleration. Control for avoiding engine stall by forcibly releasing the clutch is disclosed.

JP 05-126251 A

  By the way, even if the deceleration is the same magnitude, the engine stall may occur if the friction clutch is engaged, but the engine stall may not occur if slip control is being performed. However, in Patent Document 1, since the same control as that in the engaged state is performed even during slip control, the friction clutch may be forcibly released without engine stall.

  There is a delay time for switching the friction clutch from the disengaged state to the engaged state or the slip state, that is, the state capable of transmitting torque. Therefore, for example, when accelerating immediately after decelerating at such a speed that the friction clutch is forcibly released, the vehicle accelerates only by increasing the engine speed until the friction clutch is in a state where torque can be transmitted. do not do. In addition, if the increase in the engine speed is suppressed until the torque can be transmitted in order to prevent the engine speed from rising, the engine speed does not increase even though the accelerator pedal is depressed. It will give you a feeling of stickiness.

  That is, in the control of Patent Document 1, the friction clutch is forcibly released even though there is no possibility of engine stall, and when reacceleration is performed, the engine rotation speed increases or the driver feels tattered. There is a risk.

  In addition, the slip control may be executed not only for starting the vehicle but also for the purpose of expanding the fuel cut region or the like when decelerating from a state in which the friction clutch is engaged. Therefore, the situation in which the friction clutch is forcibly released even though there is no risk of engine stall may occur even during deceleration.

  Therefore, an object of the present invention is to provide a control device that can reduce the frequency of forced release of a friction clutch and start acceleration immediately when an accelerator pedal is depressed during or after deceleration.

  An automatic transmission system of the present invention includes a friction clutch interposed between an internal combustion engine and a transmission input shaft, and a transmission controller that controls engagement and release of the friction clutch. Then, the transmission controller forcibly releases the friction clutch according to the deceleration of the vehicle for slip control in which differential rotation occurs between the input side and the output side of the friction clutch according to the driving state of the vehicle and the engine stall prevention. The clutch forced release control is executed. Further, the transmission controller relaxes the deceleration threshold for determining whether or not to execute the forced clutch release control at the time of deceleration during the slip control, as compared to when the slip control is not executed according to the clutch capacity of the friction clutch. .

  According to the present invention, at the time of deceleration during slip control execution, the deceleration threshold value is relaxed compared to when slip control is not executed, so the chance that the clutch is forcibly released is reduced. Thus, when the accelerator pedal is depressed during or after deceleration, the vehicle can be accelerated quickly.

1 is a configuration diagram of a system to which the present invention is applied. It is a figure which shows the relationship between an operation area | region and the control state of a 1st clutch. It is a figure which shows an example of the relationship between a vehicle speed and deceleration, and a deceleration threshold value. It is a flowchart which shows the change control routine of the deceleration threshold value which TCU performs in 1st Embodiment. It is a deceleration threshold value map stored in TCU. It is the table | surface which put together about the deceleration threshold value and cancellation | release delay time when TCU performs the control routine of 1st Embodiment. It is a time chart in case TCU does not ease a deceleration threshold value. It is a time chart when TCU relaxes the deceleration threshold. It is a flowchart which shows the change control routine of the deceleration threshold value which TCU performs in 2nd Embodiment. It is a characteristic view which shows the relationship between a friction coefficient and differential rotation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram schematically showing the configuration of a system to which the first embodiment of the present invention is applied.

  First, the configuration and control system of the automatic transmission 4 will be described.

  The automatic transmission 4 is a so-called twin clutch transmission having two paths from the input shaft 1a to the output shaft 11.

  One path includes the input shaft 1a of the internal combustion engine 1, the first transmission input shaft 5, the first clutch 2 that connects and disconnects the input shaft 1a and the first transmission input shaft 5, and the first transmission. A first gear train 8 interposed between the input shaft 5 and the transmission output shaft 9. The first gear train 8 has four sets of first speed, third speed, fifth speed, and reverse.

  The other path includes the input shaft 1a of the internal combustion engine 1, the second transmission input shaft 6, the second clutch 3 that connects and disconnects the input shaft 1a and the second transmission input shaft 6, and the second transmission. A second gear train 7 interposed between the input shaft 6 and the transmission output shaft 9. The second gear train 7 includes three sets of 2nd speed, 4th speed, and 6th speed.

  The output end of the transmission output shaft 9 is connected to the output shaft 11 via a final gear 10. Therefore, the rotation of the transmission output shaft 9 is changed to a rotation speed corresponding to the gear ratio of the final gear 10 and transmitted.

  The first clutch 2 and the second clutch 3 are operated by hydraulic pressure that is variably controlled by the transmission controller (TCU) 31 using the solenoid valve 20.

  The TCU 31 reads the engine rotation speed from the engine controller (ECM) 30 via the controller area network (CAN), and in addition, the brake switch 32, the range signal 33 of the transmission 4, and the hydraulic oil temperature sensor of the transmission 4 The information from 34 is also read. Then, based on these pieces of information, it is determined whether the first clutch 2 and the second clutch 3 are to be engaged or disengaged, and the solenoid valve 20 is actuated so as to obtain a corresponding hydraulic pressure.

  Each of the ECM 30 and the TCU 31 includes a microcomputer that includes a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). Note that the ECM 30 and the TCU 31 can be configured by a plurality of microcomputers.

  Next, the shifting operation of the automatic transmission 4 will be described.

  The automatic transmission 4 includes a first gear train 8 having first, third, and fifth gears on a first transmission input shaft 5 and second, fourth, and sixth gears on a second transmission input shaft 6. Since the second gear train 7 having the gears is provided, the first clutch 2 and the second clutch 3 are alternately engaged and released at the time of shifting. For example, when shifting from the first speed to the second speed, the first gear of the first gear train 8 is engaged, the first clutch 2 is engaged, and the second gear of the second gear train 7 is engaged. From the state in which the second clutch 3 is released, the first clutch 2 is released and the second clutch is engaged. When shifting from the second speed to the third speed, the third gear of the first gear train 8 is engaged and the first clutch 2 is released, and the second gear of the second gear train 7 is engaged and the second clutch 3 is engaged. From the state where is engaged, the second clutch 3 is released and the first clutch 2 is engaged. Thereafter, the first clutch 2 and the second clutch 3 are alternately engaged and disengaged alternately for each of the third to sixth gears.

  Since the gears of the adjacent gears are arranged in different gear trains, the gears of the next gear can be engaged in advance, so that the gear shift operation is performed by the first clutch 2 and the second clutch 3. Just switch between fastening and releasing. That is, with one gear train and one clutch, the steps of clutch release, gear disengagement at the current gear stage, gear engagement at the next gear stage, and clutch engagement are required. The time required for this can be greatly reduced.

  Next, the relationship between the control state of the first clutch 2 and the operation region will be described.

  FIG. 2 is a diagram illustrating a relationship between the operation region and the control state of the first clutch 2.

  Region A in FIG. 2 is a low-speed region including when the vehicle starts, and the TCU 31 can transmit the torque of the first clutch 2 but is not completely engaged, that is, in the input side and the output side of the first clutch 2. Slip control is performed so that differential rotation occurs. This prevents a sudden increase in the transmitted torque and realizes a smooth start.

  When the vehicle speed increases and enters the region B in FIG. 2, the TCU 31 gradually increases the torque capacity of the first clutch 2 until the first clutch 2 is fully engaged. Here too, the torque capacity is gradually increased to prevent a sudden increase in the transmission torque. Here, the completely engaged state refers to a state where there is no differential rotation of the first clutch 2, but may be included in the fully engaged state as long as the differential rotation is negligible.

  When the vehicle speed further rises and exceeds the forcible start vehicle speed of FIG. 2 and enters the C region, the TCU 31 immediately enters the fully engaged state even if the first clutch 2 is still slipping. The vehicle speed for forcibly leaving the vehicle is set to a level that does not give the driver a sense of incongruity due to a sudden change in the transmission torque when the first clutch 2 is switched to the fully engaged state. Therefore, the TCU 31 immediately enters the fully engaged state regardless of the magnitude of the differential rotation of the first clutch 2 when exceeding the start forcibly leaving vehicle speed line.

  When exceeding the 1-2 shift line, the first clutch 2 is released and the second clutch 3 is engaged for shifting from the first speed to the second speed.

  As described above, the first clutch 2 is in the slip state in the A region, is in the slip state or in the fully engaged state in the B region, depending on the engaged state, and is in the completely engaged state or the released state in the C region. In the following description, the A region and the B region are appropriately referred to as a start region, and the C region is referred to as a steady state or a shift region as appropriate.

  Although there are a 2-3 shift line, a 3-4 shift line, a 4-5 shift line, and a 5-6 shift line on the higher vehicle speed side than the 1-2 shift line, they are omitted in FIG.

  On the other hand, at the time of deceleration, if the brake pedal is not depressed, the TCU 31 performs slip control for gradually releasing the first clutch 2 when entering the A region. That is, the control opposite to the control at the time of starting described above is performed. When the brake pedal is depressed, the slip control is started from the higher vehicle speed side than the boundary line between the A region and the B region.

  This is because if the first clutch 2 is not released, the rotational speed of the internal combustion engine 1 is reduced due to the rotation of the drive wheels, and the engine stalls below the rotational speed at which autonomous driving is possible.

  Further, depending on the magnitude of the deceleration, the first clutch 2 or the second clutch 3 is forcibly released regardless of the operation region of FIG. As the deceleration increases, the engine speed decreases, and the first clutch 2 or the second clutch 3 driven by hydraulic control has a response delay from the input of the control signal until the hydraulic pressure changes. This is because if the release operation is not started, it will not be in time until the rotational speed becomes lower than the autonomous driving. The deceleration is calculated using the detection value of the vehicle speed sensor.

  The first clutch 2 is forcibly released under two conditions: the brake switch 32 is on, that is, the brake pedal is depressed by the driver, and the deceleration is equal to or greater than a preset deceleration threshold. Is the case. If these two conditions are met during deceleration, it is determined that the deceleration is rapid.

  If it is determined that the vehicle is suddenly decelerating, the TCU 31 maintains the disengaged state of the first clutch 2 until the state where the deceleration is smaller than a predetermined deceleration threshold value continues for a predetermined time or longer. Is called “release delay time”. Thus, it is possible to prevent the first clutch 2 from being frequently engaged and disengaged when the deceleration is near the deceleration threshold, thereby impairing drivability.

  Here, the deceleration threshold will be described.

  FIG. 3 is a diagram illustrating an example of the relationship between the vehicle speed and deceleration and the deceleration threshold when the first clutch 2 is in the fully engaged state. The deceleration on the vertical axis is larger as it goes downward in the figure, that is, it decelerates rapidly.

  The solid line in FIG. 3 is the deceleration threshold, and the one-dot chain line is the engine stall avoidable limit line calculated in consideration of the hydraulic response delay. The two-dot chain line in FIG. 3 is a clutch release threshold value for the low vehicle speed range obtained by adaptation based on the clutch release threshold value in the low vehicle speed range of the continuously variable transmission. According to the engine stall avoidance limit line, in the low vehicle speed range, the deceleration that becomes the clutch release threshold is also reduced, and the clutch is frequently released. Therefore, in order to avoid this, the vehicle speed is reduced in the low vehicle speed range. Regardless of the threshold value, a constant threshold is used. Specifically, as in the present embodiment, it is obtained by adaptation based on the clutch release threshold value of the continuously variable transmission where frequent clutch release is a problem in the low rotational speed range. Further, the hatched area in FIG. 3 is a deceleration of a magnitude that cannot theoretically occur.

  As shown in FIG. 3, the deceleration threshold includes a boundary line of a deceleration region that cannot theoretically occur, an engine stall avoidance limit line, and a clutch for preventing frequent clutch release in a low rotation speed region. This is a combination with the release threshold. That is, the deceleration threshold is the clutch release threshold for preventing frequent clutch release in the region where the vehicle speed is from zero to V1, the engine stall avoidance limit line is in the region from the vehicle speed V1 to V2, and the vehicle speed V2 or higher is theoretically generated. It becomes a boundary line with the deceleration area that cannot be done.

  When the deceleration is larger than the deceleration threshold as described above, the first clutch 2 is forcibly released. However, in FIG. 3, the first clutch 2 is not forcibly released when the vehicle speed is equal to or higher than the vehicle speed V2.

  Incidentally, FIG. 3 assumes that the first clutch 2 is in a completely engaged state. However, if slip control is being performed, even if the deceleration is greater than the deceleration threshold of FIG. 3, engine stall does not occur. There is also a possibility. This is because the rotational speed of the internal combustion engine 1 is less likely to be drawn into the rotation of the drive wheels as much as the first clutch 2 slips.

  However, in the past, whether or not to release the clutch was determined using the deceleration threshold based on the fully engaged state, regardless of whether or not the slip control is being performed. There was also a case of releasing. Then, once the clutch is released, a predetermined time is required until re-engagement as described above, and thus there is a problem that re-acceleration cannot be performed even if the accelerator pedal is depressed.

  Therefore, the TCU 31 changes the deceleration threshold value used for determining whether or not the first clutch 2 is forcibly released depending on whether the first clutch 2 is in a completely engaged state or a slip state.

  In addition, the equation of motion of the member on the internal combustion engine side of the first clutch 2 during the slip control is expressed as shown in Equation (1).

Ie × d (Ne) / dt = Te−Tcl (1)
Ie: Rotational moment of inertia of crankshaft of internal combustion engine 1 Ne: Rotational speed of internal combustion engine 1 Te: Torque of internal combustion engine 1 Tcl: Clutch capacity of first clutch 2

  That is, the force that reduces the rotational speed of the internal combustion engine 1 during slip control does not depend on the deceleration of the vehicle, but only depends on the clutch capacity. The smaller the clutch capacity, the smaller the force that decreases the rotational speed of the internal combustion engine 1. .

  Therefore, for example, in a region where the clutch capacity is small because the vehicle speed is low, such as a region surrounded by an ellipse in FIG. 3, the first clutch 2 is forcibly released to a greater deceleration than when fully engaged. Even if it is not, engine stall may not occur. In other words, engine stall may not occur even if the deceleration threshold for determining whether or not to forcibly release the clutch is relaxed as compared to when fully engaged.

  Therefore, as described below, it is determined whether or not the deceleration threshold for determining whether or not to forcibly release the clutch can be relaxed, and if it can be relaxed, changing the deceleration threshold is unnecessary. The forced release of the clutch is prevented, and the above-described problem that the reacceleration performance is deteriorated is solved.

  FIG. 4 is a flowchart showing a deceleration threshold value change control routine executed by the TCU 31. This control routine is repeatedly executed at regular intervals, for example, at intervals of 10 milliseconds.

  In step S110, the TCU 31 reads the operating state. The driving state referred to here is the vehicle speed, the accelerator opening, the gear position of the automatic transmission 4, and the differential rotation of the first clutch 2.

  In step S120, the TCU 31 determines whether slip control is currently being performed based on the vehicle speed, the accelerator opening, and the differential rotation. Specifically, based on the vehicle speed and the accelerator opening, it is determined which region in FIG. 2 is currently in, and if it is the A region, it is determined that the vehicle is in the slip state. In the case of the B region, it is further determined whether or not the slip control is being performed based on the differential rotation of the first clutch 2. In the case of the C region, it is determined that the slip control is not being performed.

  In step S130, the TCU 31 determines whether or not the current vehicle speed is equal to or higher than a predetermined speed set in advance. The predetermined speed used here is a vehicle speed that is a boundary between the A region and the B region in FIG. 2, for example, the vehicle speed when the internal combustion engine 1 is operating at an idle rotation speed. That is, the TCU 31 determines whether it is the A region having a lower rotational speed than the current idle rotational speed or the B region having an idle rotational speed or higher. In the case of the B area, the process of step S140 is executed, and in the case of the A area, the process of step S170 is executed. Whether or not the internal combustion engine 1 is at the idling rotational speed is determined from the vehicle speed in the same manner as when setting a shift line of a general automatic transmission.

  In step S140, the TCU 31 determines whether or not the change rate of the clutch capacity of the first clutch 2 is equal to or less than a threshold value. The change rate of the clutch capacity is obtained by time-differentiating the clutch hydraulic pressure instruction value set by the TCU 31 according to the rotational speed of the internal combustion engine 1. The clutch hydraulic pressure instruction value uses the rotational speed of the internal combustion engine 1 as a parameter, and increases as the rotational speed increases.

  The threshold value is set based on the actual overshoot amount of the clutch engagement hydraulic pressure when the change in the rotational speed of the internal combustion engine 1 changes from increase to decrease and the clutch hydraulic pressure instruction value also changes from increase to decrease. That is, the change rate of the clutch capacity that does not cause the first clutch 2 to be completely engaged even if overshoot is set as the threshold value.

  If the result of determination in step S140 is that the clutch capacity is smaller than the threshold, the TCU 31 relaxes the deceleration threshold in step S150, which will be described later, and if it is greater, the TCU 31 prohibits relaxation of the deceleration threshold in step S160, which will be described later.

  In other words, when the clutch hydraulic pressure indication value is large and starts to change from a rising state to a lowering state, for example, when sudden deceleration is started during acceleration in a high rotational speed range, the actual clutch engagement hydraulic pressure overshoots. The first clutch 2 may be in a completely engaged state. When the engine is completely engaged due to overshoot, the rotational speed of the internal combustion engine 1 may be drawn into the rotation of the driving wheel that rapidly decelerates, leading to engine stall. Therefore, relaxation of the deceleration threshold value is permitted only when the clutch capacity change speed is smaller than the threshold value, that is, there is no possibility of engine stall even if the actual clutch engagement hydraulic pressure overshoots.

  In step S150, the TCU 31 relaxes the deceleration threshold, which is a threshold for determining whether or not the first clutch 2 is forcibly released, based on the map shown in FIG. Furthermore, the release delay time is shortened compared with the case of the complete fastening state.

  FIG. 5 is a deceleration threshold map stored in the TCU 31. The horizontal axis represents the clutch capacity change amount, and the vertical axis represents the deceleration threshold. As shown in FIG. 5, the deceleration threshold increases as the clutch capacity change speed decreases. That is, as the clutch capacity change speed decreases, the first clutch 2 is not forcibly released until a larger deceleration.

  In step S160, the TCU 31 prohibits relaxation of the deceleration threshold. That is, the TCU 31 determines whether or not the first clutch 2 is forcibly released based on the same deceleration threshold as that when the first clutch 2 is in the fully engaged state. Also, shortening of the release delay time is prohibited.

  On the other hand, in step S170, the TCU 31 determines whether or not the clutch capacity change speed is equal to or less than the threshold value as in step S140. If the clutch capacity change speed is equal to or less than the threshold value, the process of step S180 is executed. Execute the process.

  In step S180, the TCU 31 relaxes the deceleration threshold of the first clutch 2 and shortens the release delay time as in step S150.

  In step S180, the deceleration threshold value may be cleared so as not to be forcibly released. This is because steps S170 and S180 are always executed when slip control is performed and the clutch hydraulic pressure command value is small in the A region, so that engine stall does not occur even if forced release is not performed. For the same reason, step S170 may be omitted, and the deceleration threshold value may always be relaxed or cleared in the A region.

  FIG. 6 summarizes the deceleration threshold and the release delay time after execution of the control routine. FIG. 6 shows a case where hysteresis is provided at each boundary portion of the slip control region, and processing is not performed there.

  As shown in FIG. 6, when slip control is being performed, if the clutch capacity change speed is smaller than the threshold, the deceleration threshold is relaxed and the release delay time is shortened. In this case, the deceleration threshold and the release delay time remain in the fully engaged state.

  Next, the effect when the control routine is executed to relax the deceleration threshold will be described.

  FIG. 7 is a time chart when the deceleration threshold is not relaxed, and FIG. 8 is a term chart when the deceleration threshold is relaxed by the control routine.

  In either case, the brake pedal is depressed at time t1 to start deceleration, the brake pedal is released at time t3, and the accelerator pedal is depressed at time t4.

  In FIG. 7, when the brake pedal is depressed at time t1, the rotational speed and vehicle speed of the first clutch 2 begin to decrease, and at time t2 when the condition of forced clutch release that the brake switch is on and the deceleration is equal to or greater than a predetermined value is satisfied. 1 Clutch 2 is forcibly released. Thereafter, even when the brake switch is turned off at time t3 and the deceleration decreases, the first clutch 2 remains released until the release delay time elapses. For this reason, even if the accelerator pedal is depressed at time t4 during the release delay time, the clutch rotational speed and the vehicle speed continue to decrease, and acceleration starts after the release delay time has elapsed.

  On the other hand, in FIG. 8, the first clutch 2 is not forcibly released at time t2 because the deceleration threshold is relaxed. Therefore, if the accelerator pedal is depressed at time t4, acceleration is started immediately.

  As described above, when the engine stall does not occur even if the clutch is not forcibly released, the deceleration threshold value is relaxed, so that the acceleration can be started promptly when shifting from the deceleration state to the acceleration state.

  As described above, according to the present embodiment, the following effects can be obtained.

  (1) The TCU 31 relaxes the deceleration threshold for determining whether or not to execute the forced clutch release control during deceleration during slip control execution, or prohibits forced clutch release when the slip control is not executed. The opportunity to forcibly release the clutch unnecessarily can be reduced. As a result, acceleration can be quickly started when the accelerator is depressed.

  (2) The TCU 31 relaxes the deceleration threshold according to the clutch capacity of the first clutch 2. Since the force that reduces the rotational speed of the internal combustion engine 1 during the slip control depends only on the clutch capacity, an appropriate deceleration threshold can be set by relaxing the deceleration threshold according to the clutch capacity.

  (3) Since the TCU 31 relaxes the deceleration threshold in the region where the slip control is always executed when the rotation speed of the first clutch 2 is equal to or less than the idle rotation speed of the internal combustion engine 1, the first clutch 2 is forced unnecessarily. Opportunities for release can be reliably reduced.

  (4) The TCU 31 detects the rotational speed of the first clutch 2 based on the vehicle speed. Specifically, the rotational speed of the first clutch 2 is estimated from the vehicle speed based on the same concept as the shift line used for the shift control of the automatic transmission 4. Thereby, the rotational speed of the first clutch 2 can be detected by a simple method.

(Second Embodiment)
In this embodiment, the system to be applied is the same as that of the first embodiment, and the same applies to the case where the deceleration threshold value is relaxed when there is no possibility of engine stall without forcibly releasing the clutch. However, a part of the control routine for determining whether or not to reduce the deceleration threshold value is different. Hereinafter, specific description will be given with reference to a flowchart.

  FIG. 9 is a flowchart showing a deceleration threshold value change control routine executed by the TCU 31 in this embodiment.

  Since steps other than step S240 and step S270 are the same as those in the flowchart of FIG.

  In step S240 and step S270, it is determined whether or not the difference in rotational speed between the input side and the output side of the first clutch 2, that is, whether the differential rotation is larger than a preset threshold value. However, if it is smaller than the threshold value, relaxation of the deceleration threshold value is prohibited. The threshold value used here is set within a range in which the friction coefficient of the first clutch 2 is constant regardless of the differential rotation. FIG. 10 is a diagram showing the relationship between the friction coefficient and the differential rotation, where the vertical axis represents the friction coefficient and the horizontal axis represents the differential rotation. The friction coefficient increases in proportion to the differential rotation in a region where the differential rotation is small, but has a characteristic that becomes substantially constant regardless of the differential rotation when exceeding a predetermined differential rotation. Therefore, for example, a value near the lower limit of the differential rotation at which the friction coefficient is substantially constant is set as the threshold value.

  Since the clutch capacity depends on the friction coefficient, and the friction coefficient changes according to the differential rotation as shown in FIG. 10, it is determined using the differential rotation instead of the clutch capacity changing speed in steps S140 and S170 of FIG. However, the same effect can be obtained.

  Note that when the determination is made using the change rate of the clutch capacity, it is necessary to calculate the change amount of the clutch hydraulic pressure command value and to further differentiate it with respect to time, which may complicate the calculation. On the other hand, when the determination is made using the differential rotation, it is only necessary to detect the rotational speeds of the input side and the output side of the first clutch 2 and obtain the difference therebetween, thereby simplifying the calculation.

  As described above, in the present embodiment, in addition to the same effects as those of the first embodiment, further, using the differential rotation of the first clutch 2, it is determined whether to reduce the deceleration determination threshold and the amount of relaxation. There is also an effect that the calculation load can be reduced.

  In the above description, the automatic transmission 4 has been described as a so-called twin clutch transmission, but is not limited thereto. The present invention is applicable as long as the clutch connecting / disconnecting operation is performed using a hydraulic actuator or the like.

  The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 1st clutch 3 2nd clutch 4 Automatic transmission 5 1st transmission input shaft 6 2nd transmission input shaft 7 2nd gear train 8 1st gear train 9 Transmission output shaft 10 Final gear 11 Output shaft 20 Solenoid valve 30 Engine controller (ECM)
31 Transmission controller (TCU)

Claims (6)

A friction clutch interposed between the internal combustion engine and the transmission input shaft;
A transmission controller for controlling engagement and disengagement of the friction clutch;
With
The transmission controller forcibly releases the friction clutch according to the deceleration of the vehicle to prevent slippage control that causes differential rotation between the input side and the output side of the friction clutch according to the driving state of the vehicle, and engine stall prevention. In an automatic transmission system that executes forced clutch release control,
The transmission controller sets a deceleration threshold value for determining whether or not to execute the clutch forced release control during deceleration during the slip control execution according to the clutch capacity of the friction clutch when the slip control is not executed. Automatic transmission system characterized by being more relaxed.   The automatic transmission system according to claim 1, wherein the transmission controller prohibits the clutch forced release control by relaxing the deceleration threshold.   The automatic transmission system according to claim 1, wherein the transmission controller relaxes the deceleration threshold according to a clutch capacity of the friction clutch.   The automatic transmission system according to claim 1, wherein the transmission controller relaxes the deceleration threshold according to a differential rotation of the friction clutch.   5. The transmission controller according to claim 1, wherein the transmission controller relaxes the deceleration threshold in a region where the slip control is always executed when the rotational speed of the friction clutch is equal to or lower than an idle rotational speed of an internal combustion engine. Automatic transmission system.   The automatic transmission system according to claim 5, wherein the transmission controller detects a rotational speed of the friction clutch based on a vehicle speed.

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