Vehicle control system

Abstract

The present invention provides a vehicle control device that can improve acceleration response after temporary deceleration. [Solution] If it is necessary to avoid engine stall while the vehicle is decelerating (Yes in step S2) and responsiveness during re-acceleration is required (Yes in step S3), the engagement mechanism is set to the released state (step S4). If it is necessary to avoid engine stall while the vehicle is decelerating (Yes in step S2) and responsiveness during re-acceleration is not required (No in step S3), the lock-up clutch is released (step S5).

Description

Technical Field

[0001] The present invention relates to a vehicle control device comprising: a lock-up clutch that selectively connects an input-side rotating member and an output-side rotating member of a torque converter in a torque-transmittable manner; and an engagement mechanism that selectively connects the output-side rotating member of the torque converter and drive wheels in a torque-transmittable manner.

Background Art

[0002] Patent Document 1 describes a vehicle control device comprising a torque converter incorporating a lock-up clutch, and a stepped automatic transmission connected to an output side of the torque converter. This control device is configured to suppress a difference in deceleration feeling when the accelerator is off between a flat road and a downhill road when the driver's driving orientation is output orientation requiring large power. Specifically, when the driving orientation is output orientation and the vehicle is traveling while decelerating on a flat road, the lock-up clutch is released, so that the torque increasing action of the torque converter is utilized to increase driving torque during re-acceleration. On the other hand, when the driving orientation is output orientation and the vehicle is traveling while decelerating on a downhill road, the lock-up clutch is slipped, that is, half-engaged, so that deceleration provided by engine braking is increased compared to when the lock-up clutch is released.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] The control device described in Patent Document 1 is configured to allow acceleration after deceleration by utilizing the torque amplification effect of the torque converter by releasing the lock-up clutch when the driving orientation is output-oriented. However, the torque ratio of the torque converter increases as the speed ratio, which is the ratio of the output rotational speed to the input rotational speed, decreases. Therefore, in order to utilize the torque amplification effect during re-acceleration after releasing the lock-up clutch during deceleration, the engine speed must be increased to reduce the speed ratio, and then the lock-up clutch must be engaged by synchronizing the input and output rotational speeds. In other words, during the process of reducing the speed ratio, the torque amplification effect is small, and there is a possibility that torque generated by the engine will be used to increase the engine speed, so there was room for improvement in order to improve the acceleration responsiveness during re-acceleration.

[0005] This invention was made in view of the above-mentioned technical problems, and aims to provide a vehicle control device that can improve acceleration response after temporary deceleration. [Means for solving the problem]

[0006] To achieve the above objective, this invention provides a vehicle control device comprising: an engine; a torque converter that transmits the output torque of the engine via a fluid; a lock-up clutch that transmits torque by frictional force between an input-side rotating member and an output-side rotating member of the torque converter; and an engagement mechanism that can set an engaged state in which the output-side rotating member of the torque converter is connected to a drive wheel, and a released state in which the connection between the output-side rotating member and the drive wheel is released, wherein the device further comprises a controller that controls the lock-up clutch and the engagement mechanism, the controller having a rotation speed prediction unit that predicts the rotation speed of the engine will decrease to a predetermined rotation speed or less while the vehicle is decelerating, and a unit that, when accelerating the vehicle after deceleration, predicts from the request to accelerate the vehicle The system is characterized by comprising: an acceleration prediction unit that predicts that the torque transmitted to the drive wheels within a predetermined time frame will be equal to or greater than a predetermined torque; a clutch selection unit that sets the engagement mechanism to the released state when the rotational speed prediction unit predicts that the engine rotational speed will decrease to or below the predetermined rotational speed, and the acceleration prediction unit predicts that the required torque transmitted to the drive wheels within the predetermined time frame from the request to accelerate the vehicle will be equal to or greater than the predetermined torque; and a clutch selection unit that releases the lock-up clutch when the rotational speed prediction unit predicts that the engine rotational speed will decrease to or below the predetermined rotational speed, and the acceleration prediction unit does not predict that the torque transmitted to the drive wheels within the predetermined time frame from the request to accelerate the vehicle will be equal to or greater than the predetermined torque.

[0007] Furthermore, this invention further comprises an automatic transmission capable of changing the gear ratio between the output rotating member and the drive wheel, wherein the automatic transmission has a plurality of engagement mechanisms and is configured to set the gear ratio between the output rotating member and the drive wheel to a predetermined gear ratio by engaging at least two of the engagement mechanisms, and the engagement mechanism may include any one of the at least two engagement mechanisms that engage to set the gear ratio of the automatic transmission.

[0008] Furthermore, in this invention, the lock-up clutch and the engagement mechanism are configured to transmit torque corresponding to the supplied hydraulic pressure, and the clutch selection unit may slip or engage the lock-up clutch and set the engagement mechanism to the released state when the temperature of the oil supplied to the lock-up clutch and the clutch is below a predetermined temperature.

[0009] Furthermore, in this invention, the engagement mechanism is configured to connect a pair of engagement elements so as to be able to transmit torque by frictional force, and the released state of the engagement mechanism may include a slip state in which the pair of engagement elements rotate relative to each other while transmitting torque. [Effects of the Invention]

[0010] According to this invention, a lock-up clutch and an engagement mechanism are provided between the engine and the drive wheels. By releasing at least one of the lock-up clutch and the engagement mechanism, the engine can be rotated independently even when the vehicle decelerates and the rotational speed of the drive wheels drops to a low rotational speed. In other words, it is possible to suppress the engine speed from dropping below a predetermined rotational speed at which engine stall occurs. When the engine is rotated independently in this way to suppress the decrease in engine speed, it is anticipated that acceleration responsiveness will be necessary during re-acceleration. When acceleration responsiveness is anticipated to be necessary, the engagement mechanism with good engagement responsiveness is released. As a result, the acceleration during re-acceleration can be increased rapidly. On the other hand, when acceleration responsiveness during re-acceleration is not necessary, releasing the lock-up clutch allows the engine's output torque to be transmitted and increased via the torque converter, in other words, via the fluid, thereby gradually increasing the vehicle's acceleration. As a result, it is possible to suppress the occurrence of shocks associated with changes in acceleration during re-acceleration. [Brief explanation of the drawing]

[0011] [Figure 1]Figure 1 is a schematic diagram showing an example of a vehicle according to an embodiment of this invention. [Figure 2] Figure 2 is a block diagram illustrating the functional configuration of the control device in an embodiment of this invention. [Figure 3] Figure 3 is a flowchart illustrating an example of control performed by the control device in this embodiment of the invention. [Modes for carrying out the invention]

[0012] This invention will be described based on the embodiments shown in the figures. The embodiments described below are merely examples of how this invention can be implemented and do not limit it.

[0013] An example of a vehicle Ve in this embodiment of the present invention is schematically shown in Figure 1. The vehicle Ve shown in Figure 1 is equipped with an engine (ENG) 1 as a power source. This engine 1 is configured to generate power by burning a mixture of fuel, such as gasoline or diesel, and air, similar to conventional engines. Specifically, it is equipped with a throttle valve for controlling the amount of air drawn into the cylinder, a fuel injection device for injecting fuel into the cylinder, and a spark plug for igniting the mixture of air and fuel.

[0014] A torque converter 3 is connected to the output shaft 2 of engine 1. This torque converter 3 can be configured in the same way as a conventional torque converter provided in engine 1, and comprises a pump impeller 5 connected to the output shaft 2 of engine 1 via a front cover 4, and a turbine runner 6 provided opposite the pump impeller 5. A stator 7 for rectifying the exhaust flow from the turbine runner 6 is provided between the pump impeller 5 and the turbine runner 6. The stator 7 is connected to a fixed part 9 such as a housing via a one-way clutch 8.

[0015] Furthermore, a lock-up clutch 10 is provided to set the difference in rotational speed between the pump impeller 5 and the turbine runner 6 to a desired difference in rotational speed, and to rotate the pump impeller 5 and the turbine runner 6 together. In the example shown in Figure 1, the clutch disc 11 facing the inner surface of the front cover 4 is integrated with the turbine runner 6. An annular friction material 12 is attached to the side of the clutch disc 11 facing the front cover 4 to set the coefficient of friction between it and the front cover 4 to a predetermined coefficient of friction.

[0016] Therefore, by draining oil from between the front cover 4 and the clutch disc 11, the difference between the hydraulic pressure between the front cover 4 and the clutch disc 11 and the hydraulic pressure on the pump impeller 5 side of the clutch disc 11 becomes larger. As a result, the clutch disc 11 can be engaged with the front cover 4 to transmit torque.

[0017] Conversely, by supplying oil to increase the hydraulic pressure between the front cover 4 and the clutch disc 11, the difference between the hydraulic pressure between the front cover 4 and the clutch disc 11 and the hydraulic pressure on the pump impeller 5 side of the clutch disc 11 becomes smaller, or the hydraulic pressure between the front cover 4 and the clutch disc 11 becomes higher than the hydraulic pressure on the pump impeller 5 side of the clutch disc 11. As a result, the clutch disc 11 can be separated from the front cover 4, creating a released state in which torque transmission via the lock-up clutch 10 is interrupted.

[0018] Furthermore, by feeding back the difference between the input and output rotational speeds of the torque converter 3 and controlling the hydraulic pressure between the front cover 4 and the clutch disc 11, it is possible to maintain a slip state in which the pump impeller 5, which is the input side rotating member of the torque converter 3, and the turbine runner 6, which is the output side rotating member, are maintained at a predetermined difference in rotational speed.

[0019] An output shaft 13 of a torque converter 3 is connected to a turbine runner 6, and an automatic transmission 14 is connected to the output shaft 13. The automatic transmission 14 can be configured in the same manner as a conventionally known stepped automatic transmission. For example, it is configured to include a plurality of planetary gear mechanisms and a plurality of engagement mechanisms that connect two rotating elements among the plurality of planetary gear mechanisms or connect any one of the rotating elements to a fixed portion such as a housing, and by engaging the engagement mechanism corresponding to a set gear position, the gear ratio of the automatic transmission 14 can be set to a gear ratio corresponding to the gear position. The automatic transmission may also be configured such that by bringing at least two engagement mechanisms into an engaged state, a gear position corresponding to the engaged engagement mechanisms is set.

[0020] Further, the engagement mechanism 15 can be constituted by a frictional engagement mechanism that is coupled so as to be capable of transmitting torque by frictional force corresponding to the contact pressure of a pair of engagement elements, and furthermore, the engagement pressure can be configured to be controlled by a hydraulic actuator (not shown). In FIG. 1, only one engagement mechanism 15 is schematically shown for convenience.

[0021] Therefore, by releasing at least any one of the engagement mechanisms 15 that are engaged to set a predetermined gear position, torque transmission through the automatic transmission 14 can be interrupted, in other words, the connection between the input-side rotational speed and the output-side rotational speed of the automatic transmission 14 can be released to achieve a released state. Further, by slipping the engagement mechanism 15, that is, by relatively rotating the pair of engagement elements while transmitting torque corresponding to the contact pressure of the pair of engagement elements, the difference between the input-side rotational speed and the output-side rotational speed of the automatic transmission 14 can be appropriately changed.

[0022] A pair of drive wheels 18 is connected to an output shaft 16 of the automatic transmission 14 via a differential gear unit 17.

[0023] Furthermore, the automatic transmission 14 may be a continuously variable transmission mechanism such as a belt-type continuously variable transmission mechanism or a toroidal-type continuously variable transmission mechanism that continuously changes the gear ratio by changing the wrapping radius of a belt or changing the inclination angle of a power roller, and in the case of such a transmission mechanism, the automatic transmission 14 may be provided with an engagement mechanism 15 that can selectively cut off torque transmission between the automatic transmission 14 and the output shaft 13 of the torque converter 3.

[0024] Further, the vehicle Ve shown in Fig. 1 is provided with: an engine speed sensor (crank angle sensor) 19 that detects an engine speed; a brake sensor 20 that detects the depression amount or depression force of an unillustrated brake pedal; an acceleration sensor 21 that detects the longitudinal acceleration of the vehicle Ve; a vehicle speed sensor 22 that detects a vehicle speed; an oil temperature sensor 23 that detects the temperature of oil supplied to the torque converter 3 including the aforementioned lock-up clutch 10, supplied to a hydraulic actuator that controls the engagement mechanism 15 provided in the automatic transmission 14, or supplied for lubricating or cooling the engagement mechanism 15; a camera 24 that captures images of the exterior of the vehicle Ve; a GPS receiving unit 25 for detecting the position of the vehicle Ve; and a switch 26 for selecting a driving mode.

[0025] Furthermore, an electronic control unit (hereinafter referred to as ECU) 27 for controlling the engine 1, the lock-up clutch 10, and the engagement mechanism 15 (specifically, the hydraulic actuator) provided in the automatic transmission 14 is provided. This ECU 27 is mainly configured with a microcomputer similarly to ECUs provided in conventional vehicles, and is configured such that signals are input from devices such as the aforementioned various sensors and the camera 24, and based on the input signals and prestored calculation formulas, maps, etc., command signals for controlling the engine 1, the lock-up clutch 10, and the automatic transmission 14 are output. Note that the ECU 27 corresponds to the "controller" in the embodiment of the present invention.

[0026] As described above, in the vehicle Ve configured as described above, when the lock-up clutch 10 is engaged and the automatic transmission 14 is set to a predetermined gear (i.e., the engagement mechanism 15 is engaged), the engine 1 and the drive wheels 18 are mechanically connected, and their rotational speed ratio becomes constant. Therefore, when the vehicle Ve decelerates, the engine speed decreases in accordance with the decrease in vehicle speed. As a result, if the vehicle speed decreases to below a predetermined vehicle speed, the engine speed may decrease to a predetermined rotational speed at which the engine stalls. For this reason, the control device in this embodiment of the invention is configured to suppress the decrease in engine speed in accordance with the decrease in vehicle speed by releasing or slipping at least one of the lock-up clutch 10 and the engagement mechanism 15 when it is predicted that the engine speed will decrease to below a predetermined rotational speed.

[0027] Figure 2 shows a block diagram illustrating the functional configuration of the ECU 27. In the example shown in Figure 2, the ECU includes a rotational speed prediction unit 28, an acceleration prediction unit 29, and a clutch selection unit 30. The rotational speed prediction unit 28 predicts that the engine speed will decrease to a predetermined rotational speed or lower while decelerating. Specifically, if the rate of change of the brake pedal depression is greater than a predetermined rate of change, if the brake pedal force is greater than a predetermined force, if the deceleration of the vehicle Ve is greater than a predetermined deceleration, or if the parking brake, including a handbrake (not shown), is operated, the engine speed will decrease rapidly in accordance with the vehicle speed. In such cases, with the lock-up clutch 10 engaged and the transmission mechanism 14 set to a predetermined gear, the engine speed may decrease to a predetermined rotational speed or lower in a very short time, so the rotational speed prediction unit 28 predicts that the engine speed will decrease to a predetermined rotational speed or lower during deceleration.

[0028] Furthermore, the engagement mechanism 15 has a relatively small gap between the opposing friction plates when it is released in order to improve responsiveness when engaging. In addition, lubricating oil is supplied to the friction plates to reduce frictional resistance when the engagement mechanism 15 is in a slipping state. Therefore, if the temperature of the lubricating oil is lower than the predetermined temperature, the high viscosity of the lubricating oil may cause dragging torque to occur between the friction plates, and torque may be transmitted. In such a case, even though the engagement mechanism 15 is in a released state, the engine speed may decrease as the vehicle speed decreases, and may fall below the predetermined speed at which the engine stalls. Therefore, the rotational speed prediction unit 28 predicts that the engine speed will fall below the predetermined speed during deceleration.

[0029] The acceleration prediction unit 29 predicts that acceleration responsiveness will be necessary after deceleration. Specifically, when accelerating the vehicle Ve after deceleration, it predicts that the required torque to be transmitted to the drive wheels 18 within a predetermined time from the request to accelerate the vehicle Ve will be equal to or greater than a predetermined torque. For example, the acceleration prediction unit 29 predicts that acceleration responsiveness will be necessary when a sport driving mode is selected in which the rate of increase of driving force in relation to the accelerator input is set to be high. Also, for example, when avoiding an obstacle in front of the vehicle Ve, it may be necessary to change lanes and accelerate after deceleration. In such cases, it is required to quickly achieve relatively high acceleration during or after the process of changing lanes. In other words, it is possible to predict that acceleration responsiveness will be necessary depending on the driving environment of the vehicle Ve. Therefore, the acceleration prediction unit 29 may also predict that acceleration responsiveness will be necessary during re-acceleration based on information received by the camera 24 and the GPS receiver 25.

[0030] When the rotational speed prediction unit 28 predicts that the engine speed will drop to a predetermined rotational speed or lower, the clutch selection unit 30 selects whether to release the lock-up clutch 10 or the engagement mechanism 15 in order to prevent the engine 1 from stalling. Specifically, if the acceleration prediction unit 29 predicts that acceleration responsiveness will be necessary after deceleration, the clutch selection unit 30 selects to release the engagement mechanism 15. If the acceleration prediction unit 29 does not predict that acceleration responsiveness will be necessary after deceleration, that is, if it predicts that acceleration responsiveness will not be necessary during re-acceleration, the clutch selection unit 30 selects to release the lock-up clutch 10.

[0031] This is because, when decelerating, releasing the engagement mechanism 15 and then engaging it results in a shorter time from the time the engagement command is output until the transmitted torque exceeds a predetermined torque, compared to releasing the lock-up clutch 10 and then engaging the lock-up clutch 10. In other words, the engagement response is better. The responsiveness during re-engagement depends on the structure of the lock-up clutch 10 and the engagement mechanism 15, as well as the characteristics of the actuators that perform the engagement operation.

[0032] Figure 3 shows a flowchart illustrating an example of control performed by the ECU 27 described above. The control example shown in Figure 3 is performed when the lock-up clutch 10 and the engagement mechanism 15 are engaged, that is, when the vehicle Ve is traveling at a predetermined speed or higher. In the example shown in Figure 3, first, it is determined whether or not the brakes have been applied (step S1). This step S1 can be determined based on the signal from a sensor that detects the amount of pressure applied to the brake pedal. Note that step S1 is not limited to the operation of the brake pedal; it may also determine whether or not a parking brake such as a handbrake has been applied.

[0033] If step S1 is negatively determined because the brakes have not been applied, this routine is terminated. Conversely, if step S1 is positively determined because the brakes have been applied, a determination is made as to whether or not it is necessary to prevent engine 1 from stalling (step S2). That is, the rotational speed prediction unit 28 predicts whether or not the engine speed will drop below a predetermined rotational speed at which engine stalling occurs when decelerating. Specifically, as described above, a positive determination is made in step S2 when the rate of change of the amount of pressure applied to the brake pedal is greater than a predetermined rate of change, when the force applied to the brake pedal is greater than a predetermined force, when the deceleration of the vehicle Ve is greater than a predetermined deceleration, or when the braking force is high or the deceleration is high, such as when the parking brake is applied. Alternatively, a positive determination is made in step S2 if the temperature of the lubricating oil is lower than a predetermined temperature.

[0034] If step S2 is negatively determined because there is no need to avoid engine 1 stalling, in other words, if the likelihood of engine 1 stalling is low, this routine is terminated. Conversely, if step S2 is positively determined because there is a need to avoid engine 1 stalling, it is determined whether responsiveness during re-acceleration is necessary (step S3). This step S3 can be determined by the acceleration prediction unit 29. Specifically, step S3 is positively determined when sport driving mode is selected or when the driving environment requires rapid high torque during re-acceleration.

[0035] If it is determined in step S3 that responsiveness during re-acceleration is required, the engagement mechanism 15 is released (step S4), and this routine is terminated. Conversely, if it is determined in step S3 that responsiveness during re-acceleration is not required, the lock-up clutch 10 is released (step S5), and this routine is terminated. Note that "release" in steps S4 and S5 includes a state in which the input side rotating member and the output side rotating member are slipping.

[0036] As described above, a lock-up clutch 10 and an engagement mechanism 15 are provided between the engine 1 and the drive wheels 18. By releasing at least one of the lock-up clutch 10 and the engagement mechanism 15, the engine 1 can be rotated independently even if the vehicle Ve decelerates and the rotational speed of the drive wheels 18 drops to a low rotational speed. In other words, it is possible to prevent the engine speed from dropping below a predetermined rotational speed at which engine stall occurs.

[0037] When the engine 1 is rotated independently in this manner to suppress a decrease in engine speed, it is anticipated that acceleration responsiveness will be necessary during re-acceleration. When acceleration responsiveness is anticipated, the engagement mechanism 15, which has good engagement responsiveness, is set to a release state including a slip state. As a result, acceleration during re-acceleration can be increased rapidly. On the other hand, when acceleration responsiveness during re-acceleration is not necessary, the lock-up clutch 10 is released, and the output torque of the engine 1 is transmitted and increased via the torque converter 3, in other words, via the fluid, thereby gradually increasing the acceleration of the vehicle Ve. As a result, shocks associated with changes in acceleration during re-acceleration can be suppressed.

[0038] As described above, the automatic transmission 14, which is configured to set a gear ratio according to the engaged engagement mechanism by engaging at least two engagement mechanisms, can interrupt the transmission of torque between the engine 1 and the drive wheels 18 by disengaging at least one of the engagement mechanisms used to set the gear ratio. Therefore, in step S4 described above, it may be any one of the engagement mechanisms that is engaged to set the gear ratio at that time.

[0039] In that case, for example, an engagement mechanism to be released may be selected according to the structure of the automatic transmission 14, such as releasing a highly durable engagement mechanism. If the gear position to be set during re-acceleration may change due to deceleration, an engagement mechanism to be released may be selected according to the gear position to be set at the present time or after deceleration, such as releasing an engagement mechanism that is different from the engagement mechanism that is engaged to set the current gear position and is engaged to set the gear position that is expected to be set during re-acceleration. Alternatively, an engagement mechanism to be released may be selected according to the magnitude of the input torque expected during re-acceleration, or an engagement mechanism to be released may be selected according to the external conditions and driving conditions of the vehicle Ve.

[0040] Furthermore, if releasing the lock-up clutch 10 or the engagement mechanism 15 increases the rotational speed of the engine 1 to a predetermined upper limit, affecting the shifting performance, or if a high load is expected to be applied when engaging the engagement mechanism 15, reducing its durability, a negative decision may be made in step S2 of the control example described above. In other words, the protection of the components of the engagement mechanism 15 may be prioritized over preventing engine stall.

[0041] Furthermore, as described above, the lock-up clutch 10 and the engagement mechanism 15 are configured to switch between an engaged state and a released state (slip state) by hydraulic pressure. Therefore, when the oil temperature is low, the time from the engagement instruction to the start of the engagement operation, or until the system switches to the engaged state, becomes longer depending on the viscosity of the oil. As a result, if the engagement mechanism 15 is in the released state, it may not be possible to satisfy the responsiveness required during re-engagement, given the need for responsiveness during re-acceleration.

[0042] Therefore, when the oil temperature is low, the engagement mechanism 15 may be in a slip state, allowing the lock-up clutch 10 to slip or disengage while ensuring responsiveness during re-engagement. By configuring it in this way, when the oil temperature is low, the time from when re-acceleration is required until acceleration is generated or the acceleration reaches a predetermined acceleration level can be shortened compared to when the engagement mechanism 15 is completely disengaged and then re-engaged. [Explanation of symbols]

[0043] 1 Engine 2, 13, 16 Output shafts 3 Torque converter 4 Front cover 5 Pump impeller 6 Turbine Runner 7 Status 8 One-way clutch 9 Fixed part 10 Lock-up clutch 11. Clutch disc 12 Friction material 14 Automatic transmission 15 Engagement mechanism 17 Differential Gear Unit 18 drive wheels 19. Engine speed sensor 20 Brake Sensor 21 Accelerometer 22 Vehicle speed sensor 23 Oil temperature sensor 24 cameras 25 Receiving section 26 switches 27 Electronic Control Unit (ECU) 28. Rotational speed prediction unit 29 Acceleration prediction unit 30 Clutch selection section Vehicle

Claims

1. A vehicle control device comprising: an engine; a torque converter that transmits the output torque of the engine via a fluid; a lock-up clutch that transmits torque by friction between an input-side rotating member and an output-side rotating member of the torque converter; and an engagement mechanism that can set an engaged state in which the output-side rotating member of the torque converter is connected to a drive wheel, and a released state in which the connection between the output-side rotating member and the drive wheel is released, The system further includes a controller that controls the lock-up clutch and the engagement mechanism, The aforementioned controller, A rotation speed prediction unit that predicts that the rotation speed of the engine will decrease to a predetermined rotation speed or less while the vehicle is decelerating, An acceleration prediction unit predicts that, when the vehicle is accelerated after decelerating, the torque transmitted to the drive wheels within a predetermined time from the request to accelerate the vehicle will be equal to or greater than a predetermined torque. The system includes a clutch selection unit that, when the rotational speed prediction unit predicts that the engine speed will decrease to or below a predetermined rotational speed, and the acceleration prediction unit predicts that the required torque to be transmitted to the drive wheels within a predetermined time from the request to accelerate the vehicle will be equal to or greater than the predetermined torque, sets the engagement mechanism to the released state; and when the rotational speed prediction unit predicts that the engine speed will decrease to or below a predetermined rotational speed, and the acceleration prediction unit does not predict that the torque to be transmitted to the drive wheels within a predetermined time from the request to accelerate the vehicle will be equal to or greater than the predetermined torque, releases the lock-up clutch. A vehicle control device characterized by the following features.

2. A vehicle control device according to claim 1, The system further includes an automatic transmission capable of changing the gear ratio between the output rotating member and the drive wheel, The automatic transmission has a plurality of engagement mechanisms and is configured to set the gear ratio between the output rotating member and the drive wheel to a predetermined gear ratio by engaging at least two of the engagement mechanisms. The engagement mechanism includes one of at least two engagement mechanisms that engage to set the gear ratio of the automatic transmission. A vehicle control device characterized by the following features.

3. A vehicle control device according to claim 1, The lock-up clutch and the engagement mechanism are configured to transmit torque corresponding to the supplied hydraulic pressure. The clutch selection unit slips or engages the lock-up clutch and sets the engagement mechanism to the disengaged state when the temperature of the lock-up clutch and the oil supplied to the clutch is below a predetermined temperature. A vehicle control device characterized by the following features.

4. A vehicle control device according to any one of claims 1 to 3, The engagement mechanism is configured to connect a pair of engagement elements so as to transmit torque by frictional force, The disengaged state of the engagement mechanism includes a slip state in which the pair of engagement elements rotate relative to each other while transmitting torque. A vehicle control device characterized by the following features.

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