Vehicle control device

Abstract

To provide a vehicle control device capable of ensuring acceleration response of a vehicle while suppressing a shock generated when switching from a driven state to a driving state.SOLUTION: A vehicle 10 comprises an engine 12, a pair of drive wheels 20, and a torque converter 14, with a lock-up clutch LU, which is installed in a power transmission path PT between the engine 12 and the pair of drive wheels 20. When a state is switched from accelerator off to accelerator on, an electronic control device 90 executes (a) chip-in control while increasing an engine rotation speed Ne by engaging the lock-up clutch LU if a differential rotation ΔN of the torque converter 14 is less than a threshold value ΔN_jdg or (b) the chip-in control while releasing the lock-up clutch LU if the differential rotation ΔN is equal to or greater than the threshold value ΔN_jdg.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device for a vehicle that has a torque converter with a lock-up clutch provided in a power transmission path between an engine and a pair of drive wheels. [Background technology]

[0002] There are known control devices for vehicles that include a torque converter with a lock-up clutch provided in a power transmission path between an engine and a pair of drive wheels, such as that described in Patent Document 1. In the control device described in Patent Document 1, when switching from an accelerator-off state to an accelerator-on state, engagement of the lock-up clutch is delayed for a predetermined time after the accelerator pedal is fully depressed in order to suppress shock that occurs when switching from a driven state to a driving state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-170724 Summary of the Invention [Problem to be solved by the invention]

[0004] Even with the control device described in Patent Document 1, if the engine output torque is increased abruptly in the driven state, there is a risk of a large shock occurring when switching from the driven state to the driving state. On the other hand, if the engine output torque is increased slowly in the driven state, the acceleration response of the vehicle cannot be ensured.

[0005] The present invention has been made against the background of the above circumstances, and its purpose is to provide a vehicle control device that can ensure the acceleration responsiveness of the vehicle while suppressing the shock that occurs when switching from a driven state to a driving state. [Means for solving the problem]

[0006] The gist of the present invention is a control device for a vehicle that includes an engine, a pair of drive wheels, and a torque converter with a lock-up clutch provided in a power transmission path between the engine and the pair of drive wheels, and when switching from an accelerator-off state to an accelerator-on state, (a) if the differential rotation speed between the input side rotation speed and the output side rotation speed of the torque converter is less than a predetermined judgment value, the lock-up clutch is controlled to an engaged state to increase the rotation speed of the engine while performing tip-in control, and (b) if the differential rotation speed is equal to or greater than the predetermined judgment value, the lock-up clutch is controlled to a released state while performing tip-in control. [Effects of the Invention]

[0007] According to the control device of the present invention, when switching from an accelerator-off state to an accelerator-on state, (a) if the differential rotation speed between the input side rotation speed and the output side rotation speed of the torque converter is less than a predetermined judgment value, the lockup clutch is controlled to an engaged state, and tip-in control is executed while increasing the rotation speed of the engine; and (b) if the differential rotation speed is equal to or greater than the predetermined judgment value, the lockup clutch is controlled to a disengaged state, and tip-in control is executed. In this way, if the differential rotation speed is less than the predetermined judgment value, the engine rotation speed is quickly increased by the driven force input from the pair of drive wheels in the driven state. Furthermore, if the engine rotation speed is increased and the differential rotation speed is equal to or greater than the predetermined judgment value, the lockup clutch is disengaged, and shock that occurs when switching from the driven state to the driving state is suppressed. This suppresses shock that occurs when switching from the driven state to the driving state while ensuring the acceleration responsiveness of the vehicle. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram of a vehicle equipped with an electronic control device according to an embodiment of the present invention, and is also a functional block diagram showing the main parts of control functions for various controls in the vehicle. [Figure 2] 2 is an example of a flowchart illustrating a main part of the control operation of the electronic control device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately. [Example]

[0010] FIG. 1 is a schematic diagram of a vehicle 10 equipped with an electronic control device 90 according to an embodiment of the present invention, and is also a functional block diagram showing the main parts of control functions for various controls in the vehicle 10.

[0011] The vehicle 10 is equipped with an engine 12, which is a power source for traveling, and the engine 12 has a well-known configuration. The vehicle 10 has a power transmission path PT between the engine 12 and a pair of drive wheels 20, which includes, in order from the engine 12 side, a crankshaft 30, a torque converter 14, a turbine shaft 32, an input shaft 34, an automatic transmission 16, an output shaft 36, a differential 18, and a pair of axles 38, all of which are well-known configurations. The vehicle 10 is also equipped with a hydraulic control circuit 50, an oil pump 60, and an electronic control device 90. The torque converter 14, the automatic transmission 16, the differential 18, and the hydraulic control circuit 50 are housed in a case 40, which is a non-rotating member.

[0012] The torque converter 14 is a well-known fluid-type power transmission device. A pump wheel 14p on the input side of the torque converter 14 is connected to the engine 12 via a crankshaft 30. A turbine shaft 32 on the output side of the torque converter 14 is connected to the automatic transmission 16 via an input shaft 34. A lock-up clutch LU is provided between the pump wheel 14p and the turbine wheel 14t. The torque converter 14 is a torque converter equipped with a lock-up clutch LU. A mechanical oil pump 60, for example, is connected to the pump wheel 14p. The oil pump 60 is driven to rotate by the engine 12, thereby pumping oil OIL to the hydraulic control circuit 50.

[0013] The hydraulic control circuit 50 uses the hydraulic pressure of the oil OIL pumped from the oil pump 60 as the source pressure and supplies control hydraulic pressure to hydraulic actuators provided for performing, for example, engagement / disengagement control of the lock-up clutch LU and gear shift control of the automatic transmission 16.

[0014] The electronic control unit 90 includes, for example, a so-called microcomputer, and performs signal processing in accordance with pre-stored programs to execute various controls of the vehicle 10. The electronic control unit 90 corresponds to the "control unit" of the present invention.

[0015] The electronic control device 90 receives various signals (e.g., engine rotation speed Ne [rpm], which is the rotation speed of the engine 12; turbine rotation speed Nt [rpm], which is the rotation speed of the turbine shaft 32; and accelerator opening θacc [%], which is the driver's accelerator operation amount indicating the magnitude of the driver's acceleration operation) based on detection values ​​from various sensors (e.g., engine rotation speed sensor 80, turbine rotation speed sensor 82, and accelerator opening sensor 84) provided on the vehicle 10. The engine rotation speed Ne is equal to the pump rotation speed Np [rpm], which is the rotation speed of the pump impeller 14p, and the turbine rotation speed Nt is equal to the input shaft rotation speed Nin [rpm], which is the rotation speed of the input shaft 34. When the automatic transmission 16 has a gear ratio γat (=Nin / Nout), the input shaft rotation speed Nin is equal to the output shaft rotation speed Nout [rpm] multiplied by the gear ratio γat (=Nout × γat).

[0016] The electronic control device 90 outputs various command signals (e.g., an engine control signal Se for controlling the engine 12, a shift control signal Sat for controlling the shifting of the automatic transmission 16 via the hydraulic control circuit 50, and an LU control signal Slu for controlling the engagement and disengagement of the lock-up clutch LU) to each device (e.g., the engine 12 and the hydraulic control circuit 50) provided in the vehicle 10.

[0017] The electronic control unit 90 functionally comprises an engine control unit 90a, a gear change control unit 90b, an LU control unit 90c, an acceleration request determination unit 90d, and a rotation state determination unit 90e.

[0018] While the vehicle is traveling, the engine control unit 90a calculates a required driving torque Trdem [N·m], which is the amount of driving torque Tr [N·m] requested by the driver for the vehicle 10, for example, by applying the accelerator opening θacc and the vehicle speed V [km / h] to a required driving torque map. The required driving torque map is a relationship for calculating the required driving torque Trdem that is determined in advance experimentally or by design and stored. The engine control unit 90a controls the engine torque Te [N·m] so as to realize the required driving torque Trdem. The engine torque Te is the output torque of the engine 12. In this specification, unless otherwise distinguished, driving force, driving force, force (= power), and torque are synonymous.

[0019] The shift control unit 90b uses, for example, a shift map to determine whether to shift the automatic transmission 16 and executes shift control as necessary. The shift map is a predetermined relationship having shift lines for determining whether to shift the automatic transmission 16, on a two-dimensional coordinate system using, for example, the accelerator opening θacc and the vehicle speed V as variables.

[0020] The LU control unit 90c controls the engagement / disengagement state of the lock-up clutch LU of the torque converter 14. The LU control unit 90c controls the lock-up clutch LU to be in a released state when the vehicle speed is relatively low, such as when the vehicle starts, and controls the lock-up clutch LU to be in an engaged state when the vehicle speed is relatively high.

[0021] Next, we will explain the control when switching from the accelerator-off state to the accelerator-on state. The "accelerator-off state" refers to a state in which, for example, the accelerator pedal (not shown) is not depressed and the accelerator opening θacc is zero, and the "accelerator-on state" refers to a state in which, for example, the accelerator pedal is depressed and the accelerator opening θacc is a positive value. The driver's operation to put the accelerator into the on state, i.e., the driver's operation of depressing the accelerator pedal, is referred to as the "accelerator-on operation."

[0022] Here, the "driving state" of the vehicle 10 refers to a state in which torque is transmitted from the engine 12, which is the power source for traveling, to the pair of drive wheels 20 via the torque converter 14. The "driven state" of the vehicle 10 refers to a state in which torque is transmitted from the pair of drive wheels 20 to the engine 12 via the torque converter 14. In the "driving state", the differential speed ΔN (=Np-Nt) between the pump rotation speed Np and the turbine rotation speed Nt is equal to or greater than zero, i.e., the pump rotation speed Np is equal to or greater than the turbine rotation speed Nt. In the "driven state", the differential speed ΔN is a negative value, i.e., the turbine rotation speed Nt exceeds the pump rotation speed Np.

[0023] The acceleration request determining unit 90d determines whether or not the accelerator-off state has been switched to the accelerator-on state.

[0024] The rotation state determination unit 90e determines whether the differential rotation speed ΔN is less than a determination value ΔN_jdg (<0). The pump rotation speed Np corresponds to the "input side rotation speed" in this invention, and the turbine rotation speed Nt corresponds to the "output side rotation speed" in this invention. The determination value ΔN_jdg is a determination value of the differential rotation speed ΔN that is determined in advance through experimentation or design, and that allows tip-in control to be performed while controlling the lock-up clutch LU to an engaged state so that the shock that occurs when switching from a driven state to a driving state is within an acceptable range. The determination value ΔN_jdg corresponds to the "predetermined determination value" in this invention. "Tip-in control" refers to acceleration control based on switching from an accelerator-off state to an accelerator-on state, specifically, control that switches from a driven state to a driving state in accordance with the driver's acceleration request to accelerate the vehicle 10. In tip-in control, the engine rotation speed Ne is increased and the engine torque Te is increased so that the torque transmitted to the pair of drive wheels 20 achieves the required drive torque Trdem.

[0025] When it is determined that the accelerator has been switched from an off state to an on state and that the differential rotation speed ΔN is less than the determination value ΔN_jdg, the LU control unit 90c controls the lockup clutch LU to an engaged state. Compared to when the lockup clutch LU is controlled to a disengaged state, when the lockup clutch LU is controlled to an engaged state, the engine rotation speed Ne increases more quickly due to the driven force input from the pair of drive wheels 20 in the driven state. When it is determined that the accelerator has been switched from an off state to an on state and that the differential rotation speed ΔN is equal to or greater than the determination value ΔN_jdg, the LU control unit 90c controls the lockup clutch LU to a disengaged state. Compared to when the lockup clutch LU is controlled to an engaged state, when the lockup clutch LU is controlled to a disengaged state, shock that occurs when switching from the driven state to the driving state is suppressed. When it is determined that the accelerator has been switched from an off state to an on state, the engine control unit 90a executes increase control to increase the engine torque Te. When the lock-up clutch LU is controlled to be in the engaged state and the engine rotation speed Ne is increased quickly, the engine torque Te is also increased quickly.

[0026] Fig. 2 is an example of a flowchart illustrating the control operation of the electronic control device 90 shown in Fig. 1. The flowchart in Fig. 2 is repeatedly executed while the vehicle is running, for example, in an accelerator-off state (i.e., an idle-on state in which the engine 12 is idling).

[0027] First, in step S10 (hereinafter, "step" will be omitted), it is determined whether or not an accelerator-on operation has been performed to switch to an accelerator-on state. If the determination in S10 is YES, control to increase engine torque Te is started in S20, and it is determined in S30 whether or not the differential rotation speed ΔN is less than a determination value ΔN_jdg. If the determination in S30 is YES, a control instruction to switch lockup clutch LU to an engaged state is issued in S40, and it is determined in S50 whether or not the differential rotation speed ΔN is equal to or greater than the determination value ΔN_jdg. If the determination in S50 is NO, S50 is executed again. If the determination in S50 is YES, a control instruction to switch lockup clutch LU to a released state is issued in S60. If the determination in S10 is NO, if the determination in S30 is NO, or after execution of S60, the process returns.

[0028] According to this embodiment, when switching from an accelerator-off state to an accelerator-on state, (a) if the differential rotation speed ΔN is less than the reference value ΔN_jdg, the lockup clutch LU is engaged, the engine rotation speed is increased, and tip-in control is performed. (b) If the differential rotation speed ΔN is equal to or greater than the reference value ΔN_jdg, the lockup clutch LU is disengaged, and tip-in control is performed. In this manner, if the differential rotation speed ΔN is less than the reference value ΔN_jdg, the engine rotation speed Ne is quickly increased by the driven force input from the pair of drive wheels 20 in the driven state. Furthermore, if the engine rotation speed Ne is increased and the differential rotation speed ΔN is equal to or greater than the reference value ΔN_jdg, the lockup clutch LU is disengaged, and shock occurring when switching from the driven state to the drive state is suppressed. This ensures the acceleration responsiveness of the vehicle 10 while suppressing shock occurring when switching from the driven state to the drive state.

[0029] The above-described embodiments of the present invention are merely illustrative, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the present invention. [Explanation of symbols]

[0030] 10: vehicle, 12: engine, 14: torque converter, 20: pair of drive wheels, 90: electronic control device (control device), LU: lock-up clutch, Np: pump rotation speed (input side rotation speed), Nt: turbine rotation speed (output side rotation speed), PT: power transmission path, ΔN: differential rotation, ΔN_jdg: judgment value (predetermined judgment value)

Claims

[Claim 1] A control device for a vehicle including an engine, a pair of drive wheels, and a torque converter with a lock-up clutch provided in a power transmission path between the engine and the pair of drive wheels, When the accelerator is switched from an off state to an on state, (a) if the differential rotation speed between the input side rotation speed and the output side rotation speed of the torque converter is less than a predetermined judgment value, the lockup clutch is controlled to an engaged state to increase the rotation speed of the engine and execute tip-in control, and (b) if the differential rotation speed is equal to or greater than the predetermined judgment value, the lockup clutch is controlled to a released state and execute tip-in control. A vehicle control device characterized by:

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