CN110832230B

CN110832230B - Control device for automatic transmission

Info

Publication number: CN110832230B
Application number: CN201880029257.6A
Authority: CN
Inventors: 下泽智启; 高野谅
Original assignee: Isuzu Motors Ltd
Current assignee: Isuzu Motors Ltd
Priority date: 2017-05-19
Filing date: 2018-05-18
Publication date: 2021-05-28
Anticipated expiration: 2038-05-18
Also published as: WO2018212314A1; JP6932991B2; JP2018194133A; CN110832230A

Abstract

The present invention provides a control device for an automatic transmission capable of performing the following gear shift control: it is possible to prevent excessive heat generation of the friction engagement element when switching engagement of the friction engagement element, and to prevent a reduction in drivability. The control device is a control device for an automatic transmission of a vehicle, which executes a gear shift in accordance with engagement switching of a plurality of friction engagement elements, and includes: a requested acceleration determination unit that determines whether or not a vehicle acceleration requested by a driver at the start of gear shifting is equal to or less than a predetermined threshold value; and an execution unit that executes a shift for reducing an output torque of the automatic transmission, that is, a protection shift, before engagement switching of the plurality of friction engagement elements, when the requested acceleration determination unit determines that the vehicle acceleration is equal to or less than the threshold value.

Description

Control device for automatic transmission

Technical Field

The present invention relates to a control device for an automatic transmission.

Background

Conventionally, various automatic transmissions are known which shift gears in accordance with engagement switching of a plurality of frictional engagement elements. For example, a Dual Clutch Transmission (DCT) is known, which has: a first clutch (frictional engagement element) provided between the engine and the odd-numbered stage gear train; and a second clutch (frictional engagement element) that is provided between the engine and the even-numbered gear train, and transmits the driving force from the engine to the output side via the first clutch or the second clutch. In addition, an Automatic Transmission (AT) is known, which has: a clutch (frictional engagement element) that stops relative rotation between elements constituting the planetary gear; and a brake (frictional engagement element) that stops rotation of the element, and transmits a driving force from the engine to the output side via the planetary gear.

In these automatic transmissions, switching between engagement of a plurality of frictional engagement elements, that is, releasing one frictional engagement element and engaging the other frictional engagement element, is performed in parallel with each other, so that frictional heat is generated in each frictional engagement element. The generation of excessive frictional heat causes damage to the frictional engagement elements. Therefore, some countermeasure against heat is required. On the other hand, unexpected acceleration/deceleration feeling is given to the driver at the time of shifting, and drivability is degraded, which is not desirable.

As an invention relating to a friction heat countermeasure, patent document 1 describes "a control device for an automatic transmission configured to suppress heat generation of a clutch when a temperature of the clutch becomes equal to or higher than a predetermined temperature" (abstract).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-83318

Disclosure of Invention

Problems to be solved by the invention

The control device described in patent document 1 includes: a "clutch temperature deriving unit 23b that derives the temperature of the clutch 20; and a shift control unit 23a having a clutch temperature determination unit (S102) for determining whether or not the clutch temperature derived by the clutch temperature derivation unit is higher than a preset set temperature, and performing engagement control of the clutch in a first control mode in which the clutch is in a partially engaged state during shift control when the clutch temperature is determined to be equal to or lower than the set temperature, and performing engagement control of the clutch in a second control mode in which the amount of friction slip is smaller than that in the partially engaged state when the clutch temperature is determined to be equal to or higher than the set temperature (abstract).

However, the control device described in patent document 1 switches the control mode only according to the clutch temperature, and does not necessarily prevent a reduction in drivability during shifting.

An object of the present invention is to provide a control device for an automatic transmission capable of preventing excessive heat generation of a friction engagement element when switching engagement of the friction engagement element and preventing a reduction in drivability.

Means for solving the problems

A control device for an automatic transmission according to an aspect of the present invention is a control device for an automatic transmission for a vehicle, which executes a shift in accordance with engagement switching of a plurality of friction engagement elements, and includes: a requested acceleration determination unit that determines whether or not a vehicle acceleration requested by a driver at the start of gear shifting is equal to or less than a predetermined threshold value; and an execution unit that executes a protection shift, which is a shift for reducing an output torque of the automatic transmission before engagement switching of the plurality of friction engagement elements, when the requested acceleration determination unit determines that the vehicle acceleration is equal to or less than the threshold value, wherein the execution unit executes the protection shift without reducing a vehicle speed.

Effects of the invention

According to the present invention, it is possible to provide a control device for an automatic transmission capable of preventing excessive heat generation of a friction engagement element when switching engagement of the friction engagement element and preventing a reduction in drivability.

Drawings

Fig. 1 is a schematic configuration diagram showing a vehicle to which a control device for an automatic transmission according to the present invention is applied.

Fig. 2 is a functional block diagram of a control device of an automatic transmission of the present invention.

Fig. 3 is a flowchart showing a flow of control performed by the control device of the automatic transmission according to the present invention.

Fig. 4 is a timing chart at the time of upshifting by the normal shift.

Fig. 5 is a timing chart when a downshift is performed by the normal shift.

Fig. 6 is a timing chart when upshifting is performed by the first protection shift or the second protection shift.

Fig. 7 is a timing chart when a downshift is performed by the first protection shift or the second protection shift.

Fig. 8 is a timing chart when control is performed by the control device of the automatic transmission of the present invention.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the drawings. The embodiments described below are examples, and the present invention is not limited to these embodiments.

First, the overall structure of the vehicle will be described with reference to fig. 1. As shown in fig. 1, a vehicle 1 includes: an engine 10; a DCT2 (automatic transmission) including the first clutch 20, the second clutch 30, the transmission portion 40, and the hydraulic circuit 90; and a control device 50. On the output side of the DCT2, drive wheels are coupled to enable power transmission via a propeller shaft and a differential gear, not shown.

The engine 10 is, for example, a diesel engine. The output rotation speed (hereinafter referred to as "engine rotation speed") and the output torque of the engine 10 are controlled based on the accelerator opening Acc of the accelerator pedal detected by the accelerator opening sensor 101. Further, an engine speed sensor 102 that detects the engine speed is provided on the engine output shaft 11.

The first clutch 20 is a hydraulically-operated wet multiple disc clutch having a plurality of first input-side clutch plates 21 and a plurality of first output-side clutch plates 22. The first input side clutch plate 21 rotates integrally with the engine output shaft 11 rotated by the engine 10. The first output clutch plate 22 rotates integrally with the first input shaft 41 of the transmission unit 40.

The first clutch 20 is biased in the disengagement direction by a return spring, not shown, and the first clutch 20 is engaged by moving the first piston 23 by the clutch operating hydraulic pressure supplied from the hydraulic circuit 90 to press-contact the first input-side clutch plate 21 and the first output-side clutch plate 22. By engaging the first clutch 20, the power of the engine 10 is transmitted to the first input shaft 41. The control device 50 controls the disengagement and engagement of the first clutch 20. The first clutch 20 may be a dry single-plate clutch.

The second clutch 30 is a hydraulically-operated wet multiple disc clutch having a plurality of second input-side clutch plates 31 and a plurality of second output-side clutch plates 32. The second input side clutch plate 31 rotates integrally with the engine output shaft 11. The second output side clutch plate 32 rotates integrally with the second input shaft 42 of the transmission unit 40.

The second clutch 30 is biased in the disengagement direction by a return spring, not shown, and the second clutch 30 is engaged by moving the second piston 33 by the clutch operating hydraulic pressure supplied from the hydraulic circuit 90 to press-contact the second input side clutch plates 31 and the second output side clutch plates 32. By engaging the second clutch 30, the power of the engine 10 is transmitted to the second input shaft 42. The control device 50 controls the disengagement and engagement of the second clutch 30. The second clutch 30 may be a dry single-plate clutch. Hereinafter, the first input side clutch plate 21, the second input side clutch plate 31, the first output side clutch plate 22, and the second output side clutch plate 32 will be referred to as "clutch plates" only as needed.

The second clutch 30 is disposed on the outer peripheral side of the first clutch 20. Further, the first input shaft 41 is provided with a not-shown lubricating oil passage constituted by an axial oil passage and one or more radial oil passages, and the first input shaft 41 is radially sprayed with lubricating oil, whereby the clutch plates of the first clutch 20 are cooled, and the clutch plates of the second clutch 30 are cooled. The lubricating oil that cools the clutch plates of the second clutch 30 flows out from the outer diameter side of the second clutch 30 and the like, and returns to an oil pan, not shown, provided in the hydraulic circuit 90. In the present embodiment, the case where the second clutch 30 is provided on the outer peripheral side of the first clutch 20 is described as an example, but the arrangement relationship between the first clutch 20 and the second clutch 30 is not limited to this. Specifically, for example, the second clutch 30 may be disposed on the rear side of the first clutch 20.

The transmission unit 40 includes a first input shaft 41 connected to the output side of the first clutch 20, and a second input shaft 42 connected to the output side of the second clutch 30. The transmission unit 40 includes a counter shaft 43 disposed parallel to the first input shaft 41 and the second input shaft 42, and an output shaft 44 disposed coaxially with the first input shaft 41 and the second input shaft 42. A vehicle speed sensor 103 that detects a vehicle speed V, which is a speed of the vehicle 1, is provided on the rear end side of the output shaft 44.

The transmission unit 40 includes a first transmission unit 60, a second transmission unit 70, and a forward/backward movement switching unit 80. The first transmission unit 60 includes a first high-speed gear train 61, a first low-speed gear train 62, and a first link mechanism 63.

The first high-speed gear train 61 includes a first input gear 61a provided to be relatively rotatable with respect to the first input shaft 41, and a first counter gear 61b provided to mesh with the first input gear 61a and to rotate integrally with the counter shaft 43.

The first low-speed gear train 62 includes a second input gear 62a provided relatively rotatably with respect to the first input shaft 41, and a second counter gear 62b provided in mesh with the second input gear 62a and integrally rotatable with the counter shaft 43.

The first coupling mechanism 63 selectively rotates the first input gear 61a or the second input gear 62a integrally with the first input shaft 41 by moving the first sleeve 63a in the axial direction (the left-right direction in fig. 1) by a shift actuator (not shown).

The second transmission unit 70 includes a second high-speed gear train 71, a second low-speed gear train 72, and a second coupling mechanism 73. The second high-speed gear train 71 includes a third input gear 71a provided to be relatively rotatable with respect to the second input shaft 42, and a third counter gear 71b provided to mesh with the third input gear 71a and to rotate integrally with the counter shaft 43.

The second low-speed gear train 72 includes a 4 th input gear 72a provided to be relatively rotatable with respect to the second input shaft 42, and a 4 th counter gear 72b provided to mesh with the 4 th input gear 72a and to rotate integrally with the counter shaft 43.

The second coupling mechanism 73 alternatively rotates the third input gear 71a or the 4 th input gear 72a integrally with the second input shaft 42 by moving the second sleeve 73a in the axial direction by a shift actuator, not shown.

The forward/backward switching unit 80 includes a forward gear train 81, a backward gear train 82, and a third coupling mechanism 83. The forward gear train 81 includes a first output gear 81a provided to be relatively rotatable with respect to the output shaft 44, and a 5 th counter gear 81b provided to mesh with the first output gear 81a and to rotate integrally with the counter shaft 43.

The rear gear train 82 includes a second output gear 82a provided to be relatively rotatable with respect to the output shaft 44, and a 6 th sub-gear 82b provided to mesh with the second output gear 82a via an idle gear 82c and to rotate integrally with the counter shaft 43.

The third coupling mechanism 83 rotates the first output gear 81a or the second output gear 82a together with the output shaft 44 alternatively by moving the third sleeve 83a in the axial direction by a shift actuator, not shown.

Here, the power transmission path in the DCT2 will be briefly described. The 1 st speed is established by coupling the second input gear 62a and the first input shaft 41 with the first coupling mechanism 63, coupling the first output gear 81a and the output shaft 44 with the third coupling mechanism 83, and engaging the first clutch 20. Accordingly, the power of the engine 10 is transmitted from the first clutch 20 to the first input shaft 41, the first low-speed gear train 62, the counter shaft 43, the forward gear train 81, and the output shaft 44 in this order.

The 2-speed is established by coupling the 4 th input gear 72a and the second input shaft 42 with the second coupling mechanism 73, coupling the first output gear 81a and the output shaft 44 with the third coupling mechanism 83, and engaging the second clutch 30. Accordingly, the power of the engine 10 is transmitted from the second clutch 30 to the second input shaft 42, the second low-speed gear train 72, the counter shaft 43, the forward gear train 81, and the output shaft 44 in this order.

The 3-speed is established by coupling the first input gear 61a and the first input shaft 41 by the first coupling mechanism 63, coupling the first output gear 81a and the output shaft 44 by the third coupling mechanism 83, and engaging the first clutch 20. Accordingly, the power of the engine 10 is transmitted from the first clutch 20 to the first input shaft 41, the first high-speed gear train 61, the counter shaft 43, the forward gear train 81, and the output shaft 44 in this order.

The 4-speed is established by coupling the third input gear 71a and the second input shaft 42 with the second coupling mechanism 73, coupling the first output gear 81a and the output shaft 44 with the third coupling mechanism 83, and engaging the second clutch 30. Accordingly, the power of the engine 10 is transmitted from the second clutch 30 to the second input shaft 42, the second high-speed gear train 71, the counter shaft 43, the forward gear train 81, and the output shaft 44 in this order.

The control device 50 includes a CPU (Central Processing Unit) 51, a memory 52, and an interface (not shown) connected to various sensors and devices to transmit and receive signals. The CPU51 controls the engine 10 by executing programs stored in the memory 52 and controls the DCT2 by controlling the hydraulic circuit 90. Specifically, the CPU51 functions as the shift condition satisfaction determination unit 53, the requested acceleration determination unit 54, the vehicle acceleration determination unit 55, and the execution unit 56 by executing the program stored in the memory 52, as shown in fig. 2.

The shift condition satisfaction determination unit 53 determines whether or not a shift condition for upshift or downshift is satisfied based on the accelerator opening Acc, the vehicle speed V, and the shift map stored in the memory 52.

The requested acceleration determination unit 54 determines whether or not the requested acceleration, which is the acceleration of the vehicle 1 requested by the driver, is larger than a predetermined reference value, that is, a switching acceleration. The requested acceleration can be obtained by a known method based on the accelerator opening Acc, the vehicle speed V, and the like. The switching acceleration is determined based on an experiment, a method of using the vehicle 1, a vehicle type, and the like, and is stored in the memory 52.

The vehicle acceleration determination unit 55 determines whether or not the vehicle acceleration, which is the acceleration in the traveling direction of the vehicle 1, exceeds 0.

The actuator 56 performs the disconnection and engagement of the first clutch 20, the disconnection and engagement of the second clutch 30, and the movement of the first sleeve 63a, the second sleeve 73a, and the third sleeve 83a via the hydraulic circuit 90. Thus, the executing section 56 performs an upshift or a downshift through either one of the normal shift and the protection shift.

The ordinary shift refers to a shift as follows: the engaging switching step of the two clutches and the step of shifting the engine speed from one of the first input shaft 41 and the second input shaft 42 to the other are performed without reducing the output torque of the DCT2 by a predetermined amount from the value at the start of the gear shift.

The protection shift refers to a shift as follows: the engagement switching process of the two clutches and the process of shifting the engine speed from one of the first input shaft 41 and the second input shaft 42 to the other are performed in a state where the output torque of the DCT2 is reduced. Thus, when the protection shift is performed, the energy absorbed by each of the two clutches is reduced. That is, the friction heat generated by each of the two clutches is reduced. Thus, both clutches can be protected from frictional heat. The protection shift includes two kinds of first protection shift and second protection shift.

The first protection shift refers to a shift as follows: the engagement switching process of the two clutches and the process of shifting the engine speed from one of the first input shaft 41 and the second input shaft 42 to the other are performed in a state where the output torque of the DCT2 is reduced by a predetermined amount from the value at the start of the gear shift.

The second guard shift refers to a shift as follows: the engagement switching process of the two clutches and the process of shifting the engine speed from one of the first input shaft 41 and the second input shaft 42 to the other are performed in a state where the output torque of the DCT2 is reduced within a range in which the vehicle 1 is not decelerated.

It is not necessary that all of the above-described functional units be realized by the control device 50, and one or more of the above-described functional units may be realized by another control device different from the control device 50. For example, the control device 50 may be configured to function as the requested acceleration determination unit 54 and the execution unit 56. It is needless to say that any one of the above-described functional units may be configured to have the function of another functional unit.

Next, the shift control performed by the transmission control device according to the present embodiment will be described in detail with reference to the flowchart of fig. 3.

First, the shift condition satisfaction determination unit 53 determines whether or not the shift condition for upshift or downshift is satisfied (S1). While it is determined that the shift condition is not satisfied (no at S1), the determination as to whether the shift condition is satisfied is repeated until it is determined that the shift condition is satisfied (yes at S1).

When it is determined that the shift condition is satisfied, the requested acceleration determination unit 54 determines whether the requested acceleration is larger than the switching acceleration (S2).

When the requested acceleration determining unit 54 determines that the requested acceleration is greater than the switching acceleration (yes at S2), the executing unit 56 executes the normal shift (S3). When the ordinary shift is finished, the shift control is finished.

On the other hand, when the requested acceleration determining unit 54 determines that the requested acceleration is equal to or less than the switching acceleration (no at S2), the execution unit 56 executes the first protection shift (S4).

While the first protection shift is being executed, it is determined by the vehicle acceleration determining portion 55 whether the vehicle acceleration exceeds 0 (S5). When the vehicle acceleration determination unit 55 determines that the vehicle acceleration exceeds 0 (yes in S5), that is, the vehicle 1 is accelerating, the first protection shift by the execution unit 56 is continued until the execution unit 56 determines that the first protection shift is ended (during the period of determination no in S6). When the execution unit 56 determines that the first protection shift is completed (yes at S6), the shift control is terminated.

Further, when the vehicle acceleration determination unit 55 determines that the vehicle acceleration is 0 or less (no in S5), that is, the vehicle 1 is traveling at a constant speed or decelerating while the first protection shift is being executed, the execution unit 56 executes the second protection shift instead of the first protection shift (S7). When the second protection shift is finished, the shift control is finished.

Next, various gear shifts executed by the execution unit 56 will be described in detail with reference to a timing chart showing a flow of the gear shift. First, a normal shift will be described with reference to fig. 4. Here, a case where an upshift from the 3-speed to the 4-speed is performed will be described as an example.

When the normal shift is started, first, as shown in the middle diagram, the executing portion 56 reduces the torque capacity (transmittable torque) of the first clutch 20 to the engine torque. Further, at this time, the engine torque coincides with the driver-requested engine torque.

Next, the execution unit 56 gradually decreases the torque capacity of the first clutch 20 and gradually increases the torque capacity of the second clutch 30. That is, the engagement switching of the clutch is performed.

As a result, as shown in the following figures, the first clutch system output torque, which is the torque transmitted to the output shaft 44 via the first clutch 20 and the first transmission unit 60, gradually decreases. Further, the second clutch system output torque, which is the torque transmitted to the output shaft 44 via the second clutch 30 and the second transmission unit 70, gradually increases. The torque output from the output shaft 44, i.e., the transmission output torque (output torque of the DCT 2), is the sum of the first clutch system output torque and the second clutch system output torque. When the ordinary shift is executed, the executing portion 56 controls the torque capacities of the clutches such that the transmission output torque and the driver-requested output torque always coincide before and after the engagement switching.

When the first clutch system output torque is 0 and the transmission output torque is equal to the second clutch system output torque, the execution unit 56 performs control as follows. That is, as shown in the middle diagram, the execution unit 56 reduces the engine torque by a predetermined amount while maintaining the torque capacity of the second clutch 30 at the same value as the engine torque when the engagement of the clutch is switched and for a predetermined time. As a result, as shown in the above-described graph, the engine speed is shifted from the speed of the first input shaft 41 to the speed of the second input shaft 42. When the engine speed matches the speed of the second input shaft 42, slip is not generated in any of the clutches.

When the engine speed matches the speed of the second input shaft 42, the execution unit 56 increases the torque capacity of the second clutch 30 by a predetermined amount so as not to generate slip, as shown in the middle graph. Thus, 4-speed is realized, and the ordinary speed change is completed.

Fig. 5 is a timing chart showing a case where a downshift from the 3-speed to the 2-speed is performed by a normal shift. In the case of downshift, a step of shifting the engine speed from the speed of rotation of the second input shaft 42 to the speed of rotation of the first input shaft 41 is performed, and then a step of switching engagement of the clutch is performed.

Further, in any of the cases of upshifting and downshifting, the transmission output torque coincides with the driver-requested output torque during the execution of the ordinary shift. Therefore, the driver is less likely to be given a sense of incongruity during the shifting execution. However, since the transmission output torque is high, when the slip occurs, the energy absorbed by each clutch is also large, and therefore the temperature of each clutch tends to be high.

Next, the first protection shift and the second protection shift will be described with reference to fig. 6. Here, a case where an upshift from the 3-speed to the 4-speed is performed will be described as an example.

When the first protection shift is executed, first, as shown in the above-described drawing, the execution unit 56 reduces the transmission output torque from the driver-requested output torque to a predetermined output torque. Specifically, the execution unit 56 reduces the engine torque to a predetermined value, and reduces the torque capacity of the first clutch 20, which is the clutch already engaged, to the predetermined value.

The predetermined output torque is determined in advance based on the experimental result, the method of using the vehicle 1, the vehicle type, and the like. The predetermined output torque may be determined based on a difference between a temperature at the start of the gear shift of the clutch to be engaged by the engagement switching or an estimated temperature at the completion of the gear shift of the clutch and a predetermined threshold value.

In any case, the predetermined output torque is preferably a zero acceleration output torque that is a torque capable of maintaining the vehicle speed at the time of starting the first protection shift, or a torque larger than the zero acceleration output torque. With this configuration, even if the execution unit 56 reduces the transmission output torque, the vehicle 1 can travel without decelerating. For example, even when a protective shift is performed during traveling on a climbing road, the vehicle 1 can continue traveling without stalling. The zero acceleration output torque can be obtained from the following equation (1).

[ numerical formula 1]

In formula (1), T_0acc0Is zero acceleration output torque, r_wIs the radius of the tire, i_fIs a final drive ratio, with F marked_aeroIs an air resistance estimate, F marked ^_rollIs the rolling resistance estimate, g is the gravitational acceleration, m with the sign "^" is the vehicle weight, and θ with the sign "^" is the slope estimate. The parameters on the right side of the formula (1) may be determined in advance or may be determined by a known method at the time of application. Thus, detailed description is omitted.

Further, it is preferable that the transmission output torque is reduced from the driver-requested output torque to the predetermined output torque so as not to give a sense of discomfort to the driver. That is, it is preferable that the reduction of the transmission output torque before the engagement switching of the two clutches is performed at the following change rate: the jerk of the vehicle 1, which is reducing the transmission output torque, is set to a change speed that does not give the driver a sense of incongruity. For example, the execution unit 56 reduces the transmission output torque so as to satisfy the following expression (2). The jerk referred to herein is a forward jerk, which is a jerk in the traveling direction of the vehicle 1.

[ numerical formula 2]

In equation (2), the symbol "·" means 1-order time differential, and the symbol "·" means 2-order time differential. T is_oiIs the transmission output torque. Thus, T_oiThe 1 st order time differential value of (d) means the speed of change of the transmission output torque. In addition, v_xIs the front speed of the vehicle 1. Thus, the 2 nd order time differential value thereof means the forward jerk of the vehicle 1. Other symbols are common to equation 1.

As v_xThe range of the optimal value of the 2 nd order time differential value (forward jerk of the vehicle 1) is obtained in advance through experiments, and is stored in the memory 52. Therefore, by changing the transmission output torque at the change speed within the numerical range obtained by substituting such a value into expression (2), the transmission output torque can be reduced before the engagement switching of the clutch without giving a sense of incongruity to the driver.

Next, the execution unit 56 gradually decreases the torque capacity of the first clutch 20 and gradually increases the torque capacity of the second clutch 30. That is, the engagement switching of the clutch is performed. This step is hereinafter referred to as a "bonding switching step" as needed.

As a result, as shown in the above-described drawings, the first clutch system output torque, which is the torque transmitted to the output shaft 44 via the first clutch 20 and the first transmission unit 60, gradually decreases. Further, the second clutch system output torque, which is the torque transmitted to the output shaft 44 via the second clutch 30 and the second transmission unit 70, gradually increases. The torque output from the output shaft 44, i.e., the transmission output torque, is the sum of the first clutch system output torque and the second clutch system output torque. During execution of the first protective shift, the execution unit 56 controls the torque capacities of the clutches while always maintaining the state in which the transmission output torque is lower than the driver-requested output torque and equal to or higher than the zero-acceleration output torque before and after the engagement switching.

If the first clutch system output torque is 0 and the transmission output torque is equal to the second clutch system output torque, the executing section 56 controls the torque capacity of the second clutch 30 as follows. That is, the execution unit 56 maintains the torque capacity of the second clutch 30 at the engine torque at the time of switching the engagement of the clutch for a predetermined time, and reduces the engine torque by a predetermined amount. As a result, the engine speed is shifted from the speed of the first input shaft 41 to the speed of the second input shaft 42. This step is hereinafter referred to as an "engine speed transition step" as necessary. When the engine speed matches the speed of the second input shaft 42, slip is not generated in any of the clutches.

When the engine speed and the rotational speed of the second input shaft 42 coincide, the execution unit 56 returns the transmission output torque to the driver-requested output torque as shown in the above-described diagram. Specifically, the execution unit 56 increases the torque capacity of the second clutch 30 to be equal to the torque capacity of the first clutch 20 before the start of the shift, and restores the engine torque to the driver-requested engine torque. Thus, 4 speeds are achieved and the first protection shift is completed.

Further, when the transmission output torque is equal to or less than the zero acceleration output torque during execution of the first protection shift, the execution unit 56 switches the shift to be executed from the first protection shift to the second protection shift. In the lower diagram of fig. 6, at time t_xThe executed shift is switched from the first protection shift to the second protection shift.

When the second protective shift is started, the executing portion 56 controls the respective torque capacities of the first clutch 20 and the second clutch 30 so that the transmission output torque does not fall below the zero acceleration output torque. The other control contents are the same as the first protection shift.

Fig. 7 is a timing chart showing a case where a downshift from the 3-speed to the 2-speed is performed by the first guard shift or the second guard shift. In the case of a downshift, the engine speed shift step is performed, and then the engagement switching step of the clutch is performed, as in the case of a normal shift.

In either of the upshift and the downshift, slip occurs in both the first clutch 20 and the second clutch 30 in the engagement switching process. In the engine speed transition process, slip occurs in the second clutch 30 or the first clutch 20. Frictional heat is generated as long as sliding friction is generated. However, when the first protection shift or the second protection shift is executed, the torque capacity of each clutch is reduced during the execution of these steps, as compared with when the normal shift is executed. Therefore, the energy absorbed by each clutch is reduced, and the amount of heat generated by each clutch is reduced. That is, excessive heat generation in each clutch can be prevented by performing the first protection shift or the second protection shift. Further, since the engagement switching step and the engine speed shifting step are performed in a state where the transmission output torque, which is the output torque of the DCT2, is reduced, the amount of heat generation in each clutch can be more reliably reduced.

In addition, in either of the upshift and the downshift, the transmission output torque does not fall below the zero acceleration output torque during the execution of the second protective shift. That is, the vehicle 1 does not decelerate. Therefore, even if a gear change is performed during traveling on an uphill road, the vehicle 1 can continue traveling without stalling.

Next, a specific example of the gear shift performed by the control device 50 of the present embodiment will be described with reference to fig. 8. Fig. 8 shows a timing chart when the control device 50 performs control. The upper part of fig. 8 shows a graph of acceleration, and the lower part shows a graph of output torque.

At time t₀The vehicle 1 travels at 1 speed. In addition, at time t₁The throttle is stepped up. Therefore, the driver-requested output torque increases (see the lower graph), the requested acceleration, which is the vehicle acceleration requested by the driver, and the vehicle acceleration, which is the acceleration in the traveling direction of the vehicle 1, increase (see the upper graph).

At time t₂If it is determined that the shift condition is satisfied, the control device 50 executes an upshift from the 1-speed to the 2-speed. At this time, as shown in the above-described diagram, the requested acceleration exceeds the switching acceleration. Thus, the ordinary shift is performed. Furthermore, at time t₃The upshift from speed 1 to speed 2 ends.

At time t₁Thereafter, the accelerator depression is fixed. On the other hand, the vehicle speed gradually increases, and therefore the air resistance of the vehicle 1 gradually increases. Thus, the requested acceleration gradually decreases (refer to the upper graph). The zero acceleration output torque gradually increases (see the next diagram).

At time t₄If it is determined that the shift condition is satisfied, the control device 50 executes an upshift from the 2-speed to the 3-speed. At this time, please show in the above-mentioned paragraphThe acceleration is lower than the switching acceleration. Thus, the first protection shift is performed. During execution of the first protection shift, the transmission output torque does not become equal to or less than the zero acceleration output torque (see the lower graph). Thus, the shift from the first protection shift to the second protection shift is not made. Furthermore, at time t₅The upshift from speed 2 to speed 3 ends.

At time t₆The throttle is stepped up. Therefore, the driver request output torque increases (see the lower graph), and the request acceleration and the vehicle acceleration increase (see the upper graph).

At time t₇If it is determined that the shift condition is satisfied, the control device 50 executes an upshift from the 3-speed to the 4-speed. At this time, as shown in the above-described diagram, the requested acceleration exceeds the switching acceleration. Thus, the ordinary shift is performed. Furthermore, at time t₈The upshift from speed 3 to speed 4 ends.

At time t₉And the vehicle 1 enters the climbing road. That is, the gradient estimation value rises sharply. Therefore, as can be seen from equation (1), the zero acceleration output torque rises sharply (see the lower graph). In addition, the vehicle acceleration drops sharply. Further, since the accelerator is not stepped on, the acceleration requested by the driver is rapidly decreased together with the vehicle acceleration (see the upper graph).

At time t₁₀If it is determined that the shift condition is satisfied, the control device 50 performs a downshift from the 4-speed to the 3-speed. At this time, as shown in the above-described diagram, the requested acceleration is lower than the switching acceleration. Thus, the first protection shift is performed.

During the execution of the first protection shift, as shown in the above-described diagram, at time t₁₁The vehicle acceleration is 0. Thus, at time t₁₁The control device 50 switches the control to be executed from the first protection shift to the second protection shift. When the second guard shift is executed, the transmission output torque is set to the zero acceleration output torque as shown in the following paragraphs. Thus, the vehicle acceleration is maintained in a state of 0. That is, the vehicle 1 can continue traveling without stalling. Furthermore, at time t₁₂The downshift from 4-speed to 3-speed ends. Thereafter, the vehicle 1 is at a constant speed, i.e.The vehicle was driven with the acceleration of 0.

As described above, when the requested acceleration exceeds the switching acceleration, that is, when the driver has an idea of accelerating the vehicle 1, or when the idea is strong, the normal shift is performed without reducing the transmission output torque. Therefore, according to the control device 50 of the automatic transmission of the present embodiment, it is possible to perform a shift with good drivability in accordance with the driver's mind.

On the other hand, when the requested acceleration is equal to or less than the switching acceleration, that is, when the driver does not have an idea of accelerating the vehicle 1 or the idea is weak, the first protection shift or the second protection shift for reducing the transmission output torque is performed. Therefore, according to the control device 50 of the automatic transmission of the present embodiment, the frictional heat generated in the two clutches can be reduced, and the durability of the two clutches can be improved.

Further, in the case where the vehicle acceleration becomes 0 or less during the execution of the first protection shift, the executed shift is switched to the second protection shift. Thus, the vehicle 1 can be reliably prevented from stalling during the shifting execution.

That is, according to the control device 50 of the automatic transmission of the present embodiment, it is possible to perform a shift in which the balance between drivability and protection of the frictional engagement element is well grasped.

The automatic transmission may be a DCT that has more gear trains and can perform more-stage gear changes, or may be an automatic transmission that includes a clutch that stops relative rotation between elements constituting the planetary gear and a brake that stops rotation of the elements.

The present application is based on japanese patent application published on 5/19/2017 (japanese patent application 2017-099987), the contents of which are incorporated herein by reference.

Industrial applicability

According to the present invention, it is possible to provide a control device for an automatic transmission capable of preventing excessive heat generation of a friction engagement element when switching engagement of the friction engagement element and preventing a reduction in drivability. Thus, its industrial applicability is large.

Description of the reference numerals

1 vehicle

2 DCT

10 engines

11 output shaft of engine

20 first clutch

21 first input side clutch plate

22 first output side clutch plate

23 first piston

30 second clutch

31 second input side clutch plate

32 second output side clutch plate

33 second piston

40 speed changing part

41 first input shaft

42 second input shaft

43 auxiliary shaft

44 output shaft

50 control device

51 CPU

52 memory

53 Gear Change Condition satisfaction judging section

54 requested acceleration determination unit

55 vehicle acceleration determination unit

56 executive part

60 first transmission part

61 first high speed gear train

61a first input gear

61b first pinion

62 first Low speed Gear train

62a second input gear

62b second pinion

63 first connecting mechanism

63a first sleeve

70 second transmission part

71 second high speed gear train

71a third input gear

71b third pinion

72 second Low speed Gear train

72a 4 th input gear

72b 4 th pinion

73 second connecting mechanism

73a second sleeve

80 forward and backward switching part

81 forward gear train

81a first output gear

81b 5 th pinion

82 rear-wheel gear train

82a second output gear

82b 6 th pinion

82c idler

83 third connecting mechanism

83a third sleeve

101 accelerator opening sensor

102 engine speed sensor

103 vehicle speed sensor

90 hydraulic circuit

Claims

1. A control device for an automatic transmission of a vehicle, which executes a shift in accordance with engagement switching of a plurality of friction engagement elements, includes:

a requested acceleration determination unit that determines whether or not a vehicle acceleration requested by a driver at the start of gear shifting is equal to or less than a predetermined threshold value; and

an execution unit that executes a protection shift, which is a shift for reducing an output torque of the automatic transmission before engagement switching of the plurality of friction engagement elements, when the requested acceleration determination unit determines that the vehicle acceleration is equal to or less than the threshold value,

the executing section executes the protection shift without reducing a vehicle speed.

2. The control apparatus of an automatic transmission according to claim 1,

the executing portion executes the protection shift without reducing a vehicle speed by maintaining an output torque of the automatic transmission at a torque that can maintain the vehicle speed at the time of starting the protection shift or more.