Vehicle drive device control device

Abstract

To provide a vehicle drive system control device capable of expanding a lock-up region and improving fuel economy.SOLUTION: A control device is for a vehicle drive system which comprises: a torque converter provided with a lock-up clutch connected to an engine; a transmission mechanism which outputs rotation of the engine by changing a rotation speed; a shift clutch which is arranged between the torque converter and the transmission mechanism; and a clutch actuator which performs automatic clutch operation. A lock-up clutch control section controls the lock-up clutch so as to allow the same to be disengaged provided that a vehicle speed is equal to or less than a lock-up off speed. The lock-up off speed is changed depending on whether the shift clutch is in an engaged state or disengaged state.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a control device for a vehicle drive device. [Background technology]

[0002] Patent Document 1 discloses an automatic clutch control vehicle that has a fluid coupling with a built-in lockup clutch and a wet friction clutch between the engine and the transmission, in which only the lockup clutch is disengaged during gentle braking, and the wet friction clutch is disengaged in addition to the lockup clutch during sudden braking. With this automatic clutch control vehicle, the wet friction clutch is quickly disengaged, preventing engine stall. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-295669 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the vehicle described in Patent Document 1, the lock-up clutch is controlled to be disengaged during braking to prevent engine stall, so the lock-up region cannot be expanded and fuel economy cannot be improved.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a control device for a vehicle drive device that can expand the lock-up region and improve fuel efficiency. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a control device for a vehicle drive system including a torque converter with a lock-up clutch connected to an internal combustion engine, a speed change mechanism that changes the speed of the internal combustion engine at a speed ratio corresponding to a gear position and outputs the speed change clutch, a speed change clutch that is provided between the torque converter and the speed change mechanism and can be switched between an engaged state for transmitting power and a disconnected state for disconnecting power, and a clutch actuator that automatically operates the speed change clutch, the control device including a control unit that controls the engagement or release of the lock-up clutch, the control unit controlling the lock-up clutch to be released on the condition that the vehicle speed is equal to or lower than a predetermined vehicle speed, and the predetermined vehicle speed being changed depending on whether the speed change clutch is in the engaged state or the disconnected state. When the predetermined vehicle speed when the variable speed clutch is in the engaged state is defined as a first vehicle speed, and the predetermined vehicle speed when the variable speed clutch is in the disengaged state is defined as a second vehicle speed, the second vehicle speed is lower than the first vehicle speed. It has a configuration. Effect of the Invention

[0007] According to the present invention, it is possible to provide a control device for a vehicle drive device that can expand the lock-up region and improve fuel efficiency. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a vehicle equipped with a control device for a vehicle drive device according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a flowchart showing a flow of processing for lock-up maintenance control executed by the control device for a vehicle drive device according to one embodiment of the present invention. [Diagram 3] FIG. 3 is an example of a timing chart during a 1-2 gear shift in a vehicle according to a comparative example in which the lock-up off vehicle speed is not changed. [Figure 4] FIG. 4 is an example of a timing chart during a 1-2 shift in a vehicle equipped with a control device for a vehicle drive device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A control device for a vehicle drive device according to one embodiment of the present invention includes a torque converter with a lock-up clutch connected to an internal combustion engine, a speed change mechanism that changes the speed of the internal combustion engine at a speed ratio corresponding to a gear position and outputs the rotation, a speed change clutch that is provided between the torque converter and the speed change mechanism and can be switched between an engaged state for transmitting power and a disconnected state for disconnecting power, and a clutch actuator that automatically operates the speed change clutch, and further includes a control unit that controls the engagement or release of the lock-up clutch, the control unit controls the lock-up clutch to be released on the condition that the vehicle speed is equal to or lower than a predetermined vehicle speed, and the predetermined vehicle speed is changed depending on whether the speed change clutch is in the engaged state or the disconnected state. As a result, the control device for a vehicle drive device according to one embodiment of the present invention can expand the lock-up region and improve fuel efficiency. EXAMPLES

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle equipped with a control device for a vehicle drive device according to an embodiment of the present invention will now be described with reference to the drawings.

[0011] As shown in FIG. 1, a vehicle 1 includes an engine 2 as an internal combustion engine, an automatic transmission 3 as a vehicle drive device, drive wheels 4, and a control device 10.

[0012] The engine 2 is formed with a plurality of cylinders. In this embodiment, the engine 2 is configured to perform a series of four strokes, which are an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke, for each cylinder. The engine 2 is a power source for the vehicle 1.

[0013] The automatic transmission 3 is provided in a power transmission path between the engine 2 and drive wheels 4. The automatic transmission 3 has a torque converter 30, a speed change mechanism 31, a speed change clutch 32, and a clutch actuator 33.

[0014] The torque converter 30 is a so-called torque converter with a lock-up clutch, which has a lock-up clutch 35. The torque converter 30 is provided in a power transmission path between the engine 2 and the variable speed clutch 32, and transmits power via a fluid to output the power to a turbine shaft 36.

[0015] A variable speed clutch 32 is connected to the turbine shaft 36. The torque converter 30 amplifies the torque (driving force) input from the crankshaft 21 of the engine 2 by a rotation difference through a fluid, and outputs the amplified torque to the turbine shaft 36 and the variable speed clutch 32. The output of the torque converter 30 is then transmitted to the transmission mechanism 31 via the turbine shaft 36 and the variable speed clutch 32.

[0016] The inside of the torque converter 30 is divided into an apply chamber and a release chamber (not shown) by the lock-up clutch 35. Hydraulic oil is supplied to the apply chamber or the release chamber, and the operating state of the lock-up clutch 35 is switched depending on the hydraulic pressure (hydraulic oil pressure) of the supplied hydraulic oil.

[0017] The lock-up clutch 35 is provided within the torque converter 30, and its operating state can be switched between an engaged state in which the crankshaft 21 and the turbine shaft 36 of the engine 2 are connected (hereinafter referred to as "lock-up") so as to rotate integrally and transmit power, and a released state in which the lock-up between the crankshaft 21 and the turbine shaft 36 is released and the crankshaft 21 and the turbine shaft 36 transmit power via a fluid (hydraulic oil).

[0018] The lock-up clutch 35 is switched to the engaged state by supplying hydraulic pressure (hereinafter, this hydraulic pressure is referred to as "engagement hydraulic pressure") to the apply chamber and discharging hydraulic oil from the release chamber. Conversely, the lock-up clutch 35 is switched to the released state by supplying hydraulic pressure (hereinafter, this hydraulic pressure is referred to as "release hydraulic pressure") to the release chamber and discharging hydraulic oil from the apply chamber.

[0019] The transmission mechanism 31 is provided in a power transmission path between the transmission clutch 32 and the drive wheels 4, and has an input shaft 37 connected to the transmission clutch 32, and an output shaft 38 connected to the drive wheels 4 via a differential (not shown). The transmission mechanism 31 converts the driving force input from the transmission clutch 32 to the input shaft 37, changes the rotational speed, and outputs it from the output shaft 38.

[0020] The transmission mechanism 31 changes the rotation of the engine 2, which is output from the engine 2 and transmitted to an input shaft 37, at a gear ratio corresponding to one of a plurality of gears, which will be described later, selected, and outputs the changed rotation to an output shaft 38. The rotation and driving force output to the output shaft 38 are transmitted to the drive wheels 4 via a differential, not shown.

[0021] The transmission mechanism 31 is configured to be capable of forming a plurality of gear stages with different gear ratios by a plurality of gear pairs with different gear ratios. The gear stages in the transmission mechanism 31 are automatically switched by a shift actuator (not shown). In detail, the control device 10 judges whether a gear shift is necessary by referring to a gear shift map based on the vehicle speed and the depression amount of the accelerator pedal, and outputs a gear shift command to the shift actuator. Then, the shift actuator that receives the gear shift command operates to perform the gear shift.

[0022] The variable speed clutch 32 is provided in a power transmission path between the torque converter 30 and the transmission mechanism 31. The variable speed clutch 32 has a clutch wheel disc 32a connected to the turbine shaft 36 so as to rotate integrally therewith, and a clutch disc 32b connected to the input shaft 37 of the transmission mechanism 31 so as to rotate integrally therewith.

[0023] The variable speed clutch 32 is a dry single-plate clutch that can be switched between an engaged state in which the clutch disc 32b is pressed against the clutch wheel disc 32a to rotate together with the clutch wheel disc 32a to transmit power, and a disconnected state in which the clutch disc 32b is separated from the clutch wheel disc 32a to disconnect the power transmission between the clutch wheel disc 32a and the clutch disc 32b. In other words, the variable speed clutch 32 transmits power between the turbine shaft 36 and the input shaft 37 in the engaged state, and disconnects the power transmission between the turbine shaft 36 and the input shaft 37 in the disconnected state.

[0024] The operation of switching the speed-change clutch 32 between an engaged state and a disengaged state (hereinafter referred to as “clutch operation”) is performed automatically by a clutch actuator 33.

[0025] The clutch actuator 33 is electrically connected to the control device 10, and performs clutch operation of the speed change clutch 32 based on a command from the control device 10. Specifically, the clutch actuator 33 moves a release bearing (neither of which is shown) in the axial direction of the input shaft 37 using a release fork or the like, and causes the release bearing to elastically deform a diaphragm spring of the clutch wheel disc 32a, thereby disengaging the speed change clutch 32. The clutch actuator 33 also moves the release bearing from the disengaged position in the opposite direction to that used for disengaging the clutch, thereby releasing the diaphragm spring from elastic deformation, thereby disengaging the speed change clutch 32.

[0026] The control device 10 is composed of a computer unit equipped with a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory for storing backup data, etc., an input port, and an output port.

[0027] The ROM of the computer unit stores various constants, various maps, and the like, as well as a program for causing the computer unit to function as the control device 10. That is, the CPU executes the program stored in the ROM using the RAM as a working area, whereby the computer unit functions as the control device 10 in this embodiment.

[0028] The control device 10 is connected to various devices such as the shift actuator, clutch actuator 33, and hydraulic control device 40 described above (not shown), as well as various sensors such as a crank angle sensor 50, a turbine rotation speed sensor 51, a clutch rotation speed sensor 52, a clutch position detection sensor 53, a lock-up hydraulic sensor 54, a vehicle speed sensor 55, and an accelerator sensor 56.

[0029] The hydraulic control device 40 controls the hydraulic pressure supplied to the lock-up clutch 35 and the clutch actuator 33 of the torque converter 30. The hydraulic control device 40 switches the lock-up clutch 35 between an engaged state and a released state by adjusting the magnitude of the hydraulic pressure supplied to the lock-up clutch 35 based on a command from the control device 10. The hydraulic control device 40 switches the variable speed clutch 32 between an engaged state and a released state by adjusting the magnitude of the hydraulic pressure supplied to the clutch actuator 33 based on a command from the control device 10.

[0030] The crank angle sensor 50 detects the rotation angle (hereinafter referred to as the "crank angle") of the crankshaft 21. The control device 10 calculates the engine speed, which is the rotation speed of the engine 2 (the rotation speed of the crankshaft 21), based on the information indicating the crank angle input from the crank angle sensor 50.

[0031] The turbine rotation speed sensor 51 detects the rotation speed (hereinafter referred to as "turbine rotation speed") of the turbine shaft 36. The clutch rotation speed sensor 52 detects the rotation speed (hereinafter referred to as "clutch rotation speed") of the clutch disc 32b and the input shaft 37.

[0032] The clutch position detection sensor 53 detects the position of the release bearing in the transmission clutch 32 or the position of a part such as a release fork that moves in relation to the moving state of the release bearing (hereinafter referred to as the "clutch position"). The clutch position indicates the state of the transmission clutch 32 (disengaged state / half-clutch state / engaged state), and can also be considered to indicate the magnitude of the torque transmitted by the transmission clutch 32. The lock-up oil pressure sensor 54 detects the hydraulic oil pressure supplied to the lock-up clutch 35. In this embodiment, at least the engagement oil pressure acting on the apply chamber is detected, but the oil pressure acting on the apply chamber may be estimated or detected based on the release oil pressure acting on the release chamber. The vehicle speed sensor 55 detects the vehicle speed, which is the speed of the vehicle 1. The accelerator sensor 56 detects the amount of depression of an accelerator pedal (not shown) by the driver. The accelerator sensor 56 may also detect the movement of a throttle valve that changes in conjunction with the amount of depression of the accelerator pedal.

[0033] The control device 10 functions as a clutch control unit 101 that controls the variable speed clutch 32 by referring to a map (not shown) that defines the relationship between the clutch torque, which is the torque transmitted by the variable speed clutch 32, and the clutch position, based on the clutch position detected by the clutch position detection sensor 53.

[0034] The control device 10 has a function as a lockup clutch control unit 102 that controls the engagement or release of the lockup clutch 35. For example, when a predetermined lockup condition is established, the control device 10 executes lockup control that controls the hydraulic control device 40 so as to switch the lockup clutch 35 from a released state to an engaged state. The lockup clutch control unit 102 in this embodiment constitutes a control unit.

[0035] In this embodiment, the predetermined lock-up condition is, for example, when the vehicle speed is equal to or higher than a predetermined lock-up on vehicle speed. The predetermined lock-up on vehicle speed is a vehicle speed lower than the vehicle speed defined by the shift line (hereinafter referred to as the "1-2 shift line") on the above-mentioned shift map where an upshift from 1st gear to 2nd gear is performed, and is experimentally obtained in advance and stored in the ROM of the control device 10. Therefore, in this embodiment, an upshift from 1st gear to 2nd gear is performed after the engagement operation of the lock-up clutch 35 is started.

[0036] If a gear shift is performed with the lock-up clutch 35 released, it is necessary to calculate and control the turbine torque in order to prevent the gear shift clutch 32 from suddenly engaging due to the difference between the turbine rotation speed and the clutch rotation speed. However, in the control device 10 of this embodiment, although it is possible to command the engine torque, it is not possible to directly control the turbine torque. For this reason, if the turbine torque is to be controlled, it is necessary to convert the required turbine torque into engine torque and command the engine torque as a command value, which increases the complexity of the control.

[0037] Furthermore, if the lock-up clutch 35 is to be engaged during a gear shift, there are two objects to be controlled: the lock-up clutch 35 and the gear-change clutch 32. In this case, it is necessary to control both the lock-up clutch 35 and the gear-change clutch 32 simultaneously while taking into account their mutual interaction, which makes the control more complicated.

[0038] Therefore, in this embodiment, as described above, the vehicle speed defined by the 1-2 shift line is set to a vehicle speed higher than a predetermined lock-up on vehicle speed, thereby making it possible to perform gear shifting with the lock-up clutch 35 in a more stable engaged state. Also, if the gear shifting is performed when the lock-up clutch 35 is engaged, the difference between the turbine torque and the engine torque can be ignored, and as a result, the acceleration of the turbine rotation speed is determined by the engine torque and the clutch torque. Furthermore, there is no need to control two clutches at the same time. Therefore, in this embodiment, the control can be avoided from becoming complicated.

[0039] The predetermined lock-up condition is not limited to the above-mentioned conditions, but may be other conditions, and the state of the gear position and the vehicle speed may be set as the predetermined lock-up condition.

[0040] That is, the control device 10 controls the lock-up clutch 35 to lock up (engage) on the condition that the lock-up clutch 35 is disengaged and the vehicle speed has changed from below the lock-up on vehicle speed to above the lock-up on vehicle speed. Conversely, the control device 10 controls the lock-up clutch 35 to be disengaged on the condition that the lock-up clutch 35 is engaged and the vehicle speed has changed from above the lock-up off vehicle speed as a predetermined vehicle speed to below the lock-up off vehicle speed. The lock-up on vehicle speed is set to be higher than the lock-up off vehicle speed.

[0041] In this embodiment, the lock-up off vehicle speed is changed depending on whether the variable clutch 32 is in an engaged state or a disengaged state. Specifically, if the lock-up off vehicle speed when the variable clutch 32 is in an engaged state is defined as a first vehicle speed V1, and the lock-up off vehicle speed when the variable clutch 32 is in a disengaged state is defined as a second vehicle speed V2, the second vehicle speed V2 is set to a value lower than the first vehicle speed V1.

[0042] The first vehicle speed V1 is a vehicle speed equivalent to an engine speed obtained by adding a predetermined margin to the idle speed of the engine 2, and is experimentally obtained and stored in the ROM of the control device 10. The second vehicle speed V2 is a vehicle speed equivalent to an engine speed (for example, about idling speed - 300 [rpm]) at which engine stall can be avoided by torque converter slip even if the variable speed clutch 32 is in a fully engaged (directly connected) engaged state if the lock-up clutch 35 is released, and is experimentally obtained and stored in the ROM of the control device 10. The vehicle speed equivalent to the engine speed is a vehicle speed calculated from the engine speed (engine speed) and the gear ratio (speed ratio) of the power transmission path such as the transmission 3 and the dynamic radius of the drive wheels. By using the vehicle speed, even if the variable speed clutch 32 is in a disengaged state, a judgment can be easily made taking into account the engine speed (engine speed) when the lock-up clutch 35 and the variable speed clutch 32 are in an engaged state.

[0043] The lock-up off vehicle speed is set to gradually decrease from the first vehicle speed V1 to the second vehicle speed V2 when the shift clutch 32 starts to be switched from the engaged state to the disengaged state. The lock-up off vehicle speed may be set to decrease from the first vehicle speed V1 to the second vehicle speed V2 at the timing when the shift clutch 32 starts to be switched from the engaged state to the disengaged state.

[0044] The lock-up off vehicle speed is set to gradually increase from the second vehicle speed V2 to the first vehicle speed V1 as the clutch torque increases after the shift clutch 32 starts to switch from the disengaged state to the engaged state. In other words, the lock-up off vehicle speed is set to gradually increase from the second vehicle speed to the first vehicle speed when the clutch torque exceeds 0 [Nm]. In other words, when the torque transmission of the shift clutch 32 starts, the lock-up off vehicle speed gradually increases from the second vehicle speed to the first vehicle speed.

[0045] (Lock-up maintenance control) Next, the flow of processing for lock-up maintenance control executed by the control device 10 of this embodiment will be described with reference to FIG.

[0046] As shown in Fig. 2, the control device 10 determines whether or not the vehicle speed exceeds the vehicle speed defined by the 1-2 shift line (simply referred to as "1-2 shift line" in Fig. 2) (step S1). If the control device 10 determines in step S1 that the vehicle speed does not exceed the vehicle speed defined by the 1-2 shift line, it repeats the process of step S1.

[0047] When the control device 10 determines in step S1 that the vehicle speed exceeds the vehicle speed defined by the 1-2 shift line, it starts shifting (step S2). When the shifting starts, the shift clutch 32 starts to switch from the engaged state to the disengaged state. As a result, the clutch torque of the shift clutch 32 starts to decrease.

[0048] Next, the control device 10 reduces the lock-up off vehicle speed (step S3). At this time, the lock-up off vehicle speed gradually decreases from the first vehicle speed V1 to the second vehicle speed V2.

[0049] Thereafter, the control device 10 determines whether the clutch torque of the variable speed clutch 32 is 0 [Nm] or less (step S4). When the clutch torque becomes 0 [Nm] or less, the variable speed clutch 32 enters a disengaged state in which it is completely released.

[0050] When the control device 10 determines in step S4 that the clutch torque is not equal to or less than 0 [Nm], the control device 10 repeats the process of step S4.

[0051] When the control device 10 determines in step S4 that the clutch torque is 0 [Nm] or less, it maintains the lock-up off vehicle speed at the second vehicle speed V2 (step S5). In this embodiment, the second vehicle speed V2 is a predetermined specific value, but is not limited thereto. For example, the vehicle speed when the clutch torque is 0 [Nm] or less may be determined as the second vehicle speed V2. Even in this case, it is preferable that the second vehicle speed V2 is an engine speed (for example, about 300 [rpm] below the idle speed) at which engine stall can be avoided by releasing the lock-up clutch 35.

[0052] Next, the control device 10 starts switching the variable speed clutch 32 from a disengaged state to an engaged state, and determines whether or not the clutch torque exceeds 0 [Nm] (step S6). If the control device 10 determines in step S6 that the clutch torque does not exceed 0 [Nm], it repeats the process of step S6.

[0053] When the control device 10 determines that the clutch torque has exceeded 0 [Nm], it increases the lock-up off vehicle speed from the second vehicle speed V2 to the first vehicle speed V1 (step S7). At this time, the lock-up off vehicle speed gradually increases from the second vehicle speed V2 to the first vehicle speed V1 as the clutch torque increases.

[0054] Thereafter, the control device 10 completes the shift (step S8) and ends this lock-up maintenance control. When the shift is completed, that is, after the shift operation is completed and the shift clutch 32 is in the engaged state, the lock-up off vehicle speed becomes the first vehicle speed V1.

[0055] Next, with reference to Fig. 4, the transition of the lock-up off vehicle speed when an upshift from 1st gear to 2nd gear is performed in the vehicle 1 of this embodiment will be described in comparison with a comparative example in which the lock-up off vehicle speed is not changed as shown in Fig. 3. Figs. 3 and 4 are time charts showing the change in the state of a vehicle accelerating at a specified accelerator opening, and show the shift from 1st gear to 2nd gear from time t3 to time t6 including both before and after that.

[0056] 3 and 4, the "1-2 shift line" indicates the vehicle speed at which an upshift from 1st gear to 2nd gear is performed on the shift map. In addition, in Fig. 3 and Fig. 4, the transition of the lock-up off vehicle speed in the period from time t3 to time t6 is different between the comparative example and the embodiment, but the transition of the other parameters is assumed to be the same.

[0057] 4, at time t1, the vehicle 1 of this embodiment is accelerating in first gear and the variable speed clutch 32 is in an engaged state. Since the vehicle 1 is accelerating, the engine speed Ne, the turbine speed Nt, and the clutch speed Nc are increasing over time.

[0058] Thereafter, at time t2, when the vehicle speed reaches or exceeds the lock-up on vehicle speed, the lock-up clutch 35 starts to engage, and the lock-up clutch 35 is switched from the released state to the engaged state. Note that until the lock-up clutch 35 is engaged, the torque converter 30 transmits the rotation of the engine 2 via fluid, so that a differential speed actually occurs between the engine speed Ne and the turbine speed Nt, but this differential speed is omitted in Figures 3 and 4. After the lock-up clutch 35 is engaged, the engine speed Ne and the turbine speed Nt are synchronized.

[0059] Next, at time t3, when the vehicle speed exceeds the vehicle speed defined by the 1-2 shift line, a gear change, i.e., an upshift from 1st gear to 2nd gear, is initiated. When the upshift from 1st gear to 2nd gear is initiated, the shift clutch 32 starts to switch from the engaged state to the disengaged state. As a result, the clutch torque of the shift clutch 32 starts to decrease.

[0060] Furthermore, at time t3, when an upshift from 1st gear to 2nd gear is initiated, the lock-up off vehicle speed gradually decreases from the first vehicle speed V1 to the second vehicle speed V2.

[0061] Thereafter, at time t4, the clutch torque of the shift clutch 32 becomes 0 [Nm] or less, and the shift clutch 32 enters a completely disengaged state, and thereafter the lock-up-off vehicle speed is maintained at the second vehicle speed V2. Note that it is preferable that the timing at which the lock-up-off vehicle speed becomes the second vehicle speed V2 occurs before the clutch torque of the shift clutch 32 becomes 0 [Nm]. In other words, the timing at which the lock-up-off vehicle speed is reduced is when the shift clutch 32 switches from an engaged state to a disengaged state, and the lock-up-off vehicle speed is reduced by the time the shift clutch 32 enters a completely disengaged state where it is completely released.

[0062] After time t4, the gear pair inside the transmission mechanism 31 is switched, and the transmission is switched from 1st gear to 2nd gear. As the synchronizer operates to achieve 2nd gear, the clutch rotation speed Nc starts to decrease so that the rotation speed corresponds to the vehicle speed. At this time, the transmission clutch 32 is in a disengaged state, so that the driving force of the vehicle 1 disappears and the speed of the vehicle 1 also decreases. The engine rotation speed Ne and the turbine rotation speed Nt are controlled to decrease so as to be synchronized with the clutch rotation speed Nc corresponding to 2nd gear.

[0063] At this time, for example, if the vehicle 1 is traveling on an uphill road or a road surface that may cause a decrease in vehicle speed, during the upshift from 1st gear to 2nd gear, the vehicle speed may begin to decrease significantly after time t4, as shown in Figure 4.

[0064] 3, when such a decrease in vehicle speed occurs, the lock-up off vehicle speed remains at the first vehicle speed V1 even when an upshift from 1st gear to 2nd gear is initiated at time t3, so there is a risk that the vehicle speed will fall below the lock-up off vehicle speed after time t4 when the shift clutch 32 is disengaged. In this case, the lock-up clutch 35 is unnecessarily released in the comparative example, making it impossible to expand the lock-up region.

[0065] 3, it is possible to set the 1-2 shift line high so that the vehicle speed is less likely to fall below the lock-up off speed in order to avoid unnecessary release of the lock-up clutch 35 as described above. However, in this case, the engine speed will be high while the vehicle is traveling in 1st gear, and the fuel consumption of the engine 2 will increase.

[0066] In contrast, in this embodiment, the lock-up off vehicle speed is reduced from the first vehicle speed V1 to the second vehicle speed V2 at least after time t4 when the variable speed clutch 32 is disengaged. Therefore, even if the vehicle speed is reduced because the vehicle 1 is traveling on an uphill road or a road surface that may cause a reduction in vehicle speed, the vehicle speed can be prevented from falling below the lock-up off vehicle speed after time t4. Therefore, in this embodiment, the lock-up clutch 35 is not released during an upshift from the 1st gear to the 2nd gear, and the lock-up region can be expanded. Furthermore, since there is no need to set the 1-2 shift line higher, it is possible to prevent the fuel consumption of the engine 2 from increasing.

[0067] After time t4, when the shifting of the gear pair from the first gear to the second gear is completed inside the transmission mechanism 31 and the clutch rotation speed Nc becomes a rotation speed corresponding to the vehicle speed at the second gear, the shift clutch 32 starts to be switched from the disengaged state to the engaged state, and at time t5, the clutch torque of the shift clutch 32 exceeds 0 [Nm]. When the shift clutch 32 starts to transmit torque, the lock-up off vehicle speed starts to increase. After time t5, the lock-up off vehicle speed gradually increases from the second vehicle speed V2 to the first vehicle speed V1. Also, the vehicle speed starts to increase from time t5.

[0068] After that, at time t6, when the variable speed clutch 32 is in an engaged state, the engine speed Ne and the turbine speed Nt are synchronized with the clutch speed Nc corresponding to the second gear, and the upshift from the first gear to the second gear is completed. When the upshift from the first gear to the second gear is completed at time t6, the lockup-off vehicle speed is restored to the first vehicle speed V1. The restored lockup-off vehicle speed does not have to be restored to the first vehicle speed V1, and may be set corresponding to the second gear. It is also preferable that the return of the lockup-off vehicle speed to the first vehicle speed V1 is completed at approximately the same timing as the completion of the engagement of the variable speed clutch 32. In other words, if the variable speed clutch 32 is being controlled, the reduction in engine speed caused by the vehicle speed can be handled by the control of the variable speed clutch 32 without the release of the lockup clutch 35, so the release of the lockup clutch 35 is suppressed until the completion of the engagement of the variable speed clutch 32 (end of control).

[0069] As described above, the control device for a vehicle drive device according to this embodiment is configured to control the lock-up clutch 35 to be released on the condition that the vehicle speed is equal to or lower than the lock-up off vehicle speed. In the control device for a vehicle drive device according to this embodiment, the lock-up off vehicle speed is configured to be changed depending on whether the variable speed clutch 32 is in the engaged state or the disengaged state.

[0070] With this configuration, the control device for a vehicle drive device according to this embodiment can increase or decrease the lock-up off vehicle speed according to the state of the variable speed clutch 32, so that, for example, the lock-up off vehicle speed can be lowered when the variable speed clutch 32 is in a disengaged state, and the vehicle speed can be prevented from falling below the lock-up off vehicle speed even if the vehicle speed is reduced. This makes it possible to prevent unnecessary release of the lock-up clutch 35 and expand the lock-up region. As a result, the control device for a vehicle drive device according to this embodiment can improve fuel efficiency.

[0071] Furthermore, when the shift-change clutch 32 is in a disengaged state during an upshift from 1st to 2nd gear, the lock-up clutch 35 can be maintained in an engaged state, thereby suppressing large fluctuations in the torque input to the shift-change clutch 32 and preventing the control when engaging the shift-change clutch 32 from becoming complicated.

[0072] In addition, in the control device for a vehicle drive device of this embodiment, when the lock-up off vehicle speed when the shift clutch 32 is in an engaged state is set to a first vehicle speed V1, and the lock-up off vehicle speed when the shift clutch 32 is in a disengaged state is set to a second vehicle speed V2, the second vehicle speed V2 is set to a value lower than the first vehicle speed V1.

[0073] With this configuration, the control device for a vehicle drive system according to this embodiment can prevent the vehicle speed from dropping below the lock-up off speed even if the vehicle 1 is traveling uphill or on a road surface that may cause a decrease in vehicle speed during an upshift from 1st gear to 2nd gear. This makes it possible to prevent unnecessary release of the lock-up clutch 35, and furthermore, since there is no need to set the 1-2 shift line higher, it is also possible to prevent an increase in fuel consumption of the engine 2.

[0074] Furthermore, in the control device for a vehicle drive device of this embodiment, the lock-up off vehicle speed is configured to gradually decrease from the first vehicle speed V1 to the second vehicle speed V2 when the shift clutch 32 begins to switch from the engaged state to the disengaged state.

[0075] With this configuration, the control device for a vehicle drive device according to this embodiment can prevent the lock-up off vehicle speed from being lowered too much when the clutch torque is large and the shift clutch 32 starts to be switched from the engaged state to the disengaged state. Also, the lock-up off vehicle speed can be lowered in accordance with the reduction in clutch torque. This makes it possible to prevent engine stall from occurring when the clutch torque is large and the shift clutch 32 starts to be switched from the engaged state to the disengaged state.

[0076] Furthermore, in the control device for a vehicle drive device of this embodiment, the lock-up off vehicle speed is configured to gradually increase from the second vehicle speed V2 to the first vehicle speed V1 as the clutch torque increases after the shift clutch 32 begins to switch from the disengaged state to the engaged state.

[0077] With this configuration, the control device for a vehicle drive device in this embodiment can prevent the vehicle speed from falling below the lock-up off vehicle speed even in cases where the vehicle speed is still below the first vehicle speed V1 even when the vehicle speed increases with an increase in clutch torque.

[0078] Furthermore, the control device for a vehicle drive device according to this embodiment is configured so that when the shift clutch 32 enters an engaged state after the shift operation is completed, the lock-up off vehicle speed returns to the first vehicle speed V1.

[0079] With this configuration, the control device for a vehicle drive device in this embodiment can more reliably prevent engine stall by returning the vehicle speed to normal lock-up off speed in situations where unnecessary release of the lock-up clutch 35 does not occur.

[0080] In this embodiment, when the shift clutch 32 begins to switch from the engaged state to the disengaged state, the lock-up off vehicle speed is set to gradually decrease from the first vehicle speed V1 to the second vehicle speed V2. However, this is not limited to the above, and the lock-up off vehicle speed may be configured to decrease from the first vehicle speed V1 to the second vehicle speed V2 at the timing when the shift clutch 32 enters the disengaged state (for example, time t4 in FIG. 4).

[0081] Further, in this embodiment, the vehicle speed is detected by the vehicle speed sensor 55, but this is not limited thereto, and the vehicle speed may be calculated by the control device 10 based on the detection results of rotation speed sensors such as the turbine rotation speed sensor 51 and the clutch rotation speed sensor 52.

[0082] Although an embodiment of the invention has been disclosed, it will be apparent to one of ordinary skill in the art that modifications may be made thereto without departing from the scope of the invention, and it is intended that all such modifications and equivalents be included in the following claims. [Explanation of symbols]

[0083] 1 vehicle 2. Engine (internal combustion engine) 3 Automatic transmission (vehicle drive system) 4 Drive wheels 10 Control device 21 Crankshaft 30 Torque converter 31 Transmission mechanism 32 Shift clutch 32a clutch wheel disc 32b clutch disc 33 Clutch actuator 35 Lock-up clutch 36 Turbine shaft 37 Input shaft 38 Output shaft 40 Hydraulic control device 50 Crank angle sensor 51 Turbine speed sensor 52 Clutch rotation speed sensor 53 Clutch position detection sensor 54 Lockup oil pressure sensor 55 Vehicle speed sensor 56 Accelerator Sensor 101 Clutch control unit 102 Lock-up clutch control unit (control unit) V1 First vehicle speed V2 Second vehicle speed

Claims

1. a torque converter with a lock-up clutch connected to the internal combustion engine; a speed change mechanism that changes the rotation of the internal combustion engine at a speed change ratio corresponding to a speed change stage and outputs the rotation; a variable speed clutch that is provided between the torque converter and the speed change mechanism and that can be switched between an engaged state in which power is transmitted and a disconnected state in which power is disconnected; A clutch actuator that automatically operates the speed change clutch; A control device for a vehicle drive device comprising: A control unit is provided for controlling engagement or release of the lock-up clutch, The control unit controls the lock-up clutch to be released on the condition that the vehicle speed is equal to or lower than a predetermined vehicle speed, The predetermined vehicle speed is changed depending on whether the variable speed clutch is in the engaged state or the disengaged state, When the predetermined vehicle speed when the variable speed clutch is in the engaged state is defined as a first vehicle speed, and the predetermined vehicle speed when the variable speed clutch is in the disengaged state is defined as a second vehicle speed, A control device for a vehicle drive device, wherein the second vehicle speed is lower than the first vehicle speed.

2. 2. The control device for a vehicle drive device according to claim 1, wherein the predetermined vehicle speed is gradually decreased from the first vehicle speed to the second vehicle speed when switching of the variable speed clutch from the engaged state to the disengaged state is started.

3. 3. The control device for a vehicle drive device according to claim 1, wherein the predetermined vehicle speed gradually increases from the second vehicle speed to the first vehicle speed as the torque transmitted by the variable speed clutch increases after the variable speed clutch starts to switch from the disengaged state to the engaged state.

4. 4. The control device for a vehicle drive device according to claim 1, wherein when the shift clutch is in the engaged state after a shift operation for switching the gear stage of the transmission mechanism is completed, the predetermined vehicle speed becomes the first vehicle speed.

Images