Vehicle control system

Abstract

The aim is to curb the deterioration of the vehicle's energy consumption. [Solution] The control device 25 of the vehicle 1 includes: a pre-stop determination unit 26 that determines whether the negative pressure P of the negative pressure tank 9 at the time the stop request is received is less than a first threshold P1 when a stop request is received, a delay control unit 27 that delays stopping the engine 2 for a predetermined delay time DT from the time the stop request is received and secures intake negative pressure to be supplied to the negative pressure tank 9 when it is determined that the negative pressure P is less than the first threshold P1, a stop determination unit 28 that determines whether the negative pressure P of the negative pressure tank 9 is less than a second threshold P2 while the engine 2 is stopped, and a motoring control unit 29 that rotates the rotation shaft 2a of the engine 2 with an electric motor 4 and secures intake negative pressure to be supplied to the negative pressure tank 9 when it is determined that the negative pressure P is less than the second threshold P2. The second threshold P2 is smaller than the first threshold P1.

Description

Technical Field

[0001] This invention relates to a control device for a vehicle equipped with an engine.

Background Art

[0002] Conventionally, there is known a vehicle equipped with a booster device (master back, brake booster) that multiplies the depressing force of the brake pedal by utilizing the negative pressure generated in the intake system of the engine. Further, in such a vehicle control device, when the negative pressure that serves as the boosting source of the brake booster decreases during engine stoppage, the motor generator is operated as an electric motor, and an intake negative pressure is generated in the engine by a motor ring that rotationally drives the internal combustion engine by this motor generator to recover the negative pressure (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the recovery of negative pressure by motor ring as disclosed in Patent Document 1 is carried out by consuming the power of the in - vehicle battery, which leads to deterioration of the vehicle's electricity cost.

[0005] The vehicle control device of this invention was created in view of the above problems, and one of its purposes is to suppress deterioration of the vehicle's electricity cost. Note that, not limited to this purpose, it is also another purpose of this invention to achieve an operational effect that is led by each configuration shown in the embodiments for implementing the invention described later and that cannot be obtained by conventional techniques.

Means for Solving the Problems

[0006] The vehicle control device disclosed can be implemented in the following embodiments (examples of application) and solves at least some of the above-mentioned problems. Each of embodiments from Embodiment 2 onward is an additional embodiment that can be appropriately selected and is an embodiment that can be omitted. None of embodiments from Embodiment 2 onward disclose any embodiments or configurations that are essential to this case.

[0007] Embodiment 1. The vehicle control device disclosed is applicable to a vehicle comprising an engine, an electric motor connected to the rotating shaft of the engine, and a brake system having a negative pressure tank for accumulating intake negative pressure of the engine and a power booster for amplifying brake pedal force using the negative pressure of the negative pressure tank. The control device includes: a pre-stop determination unit that, upon receiving a stop request which is a request to stop the engine while it is running, determines whether the negative pressure in the negative pressure tank at the time the stop request is received is less than a first threshold; a delay control unit that, if the pre-stop determination unit determines that the negative pressure in the negative pressure tank is less than the first threshold, delays the stopping of the engine for a predetermined delay time from the time the stop request is received to secure intake negative pressure to be supplied to the negative pressure tank; a stop-in determination unit that, while the engine is stopped, determines whether the negative pressure in the negative pressure tank is less than a second threshold; and a motoring control unit that, if the stop-in determination unit determines that the negative pressure in the negative pressure tank is less than the second threshold, rotates the rotating shaft of the engine with the electric motor to secure intake negative pressure to be supplied to the negative pressure tank. The second threshold is smaller than the first threshold.

[0008] Embodiment 2. In Embodiment 1 described above, it is preferable that the second threshold includes a second driving threshold used while the vehicle is in motion and a second stopping threshold used while the vehicle is stopped. In this case, it is preferable that the second driving threshold is greater than the second stopping threshold.

[0009] Embodiment 3. In Embodiment 1 described above, it is preferable that the vehicle further comprises a drive motor separate from the electric motor. In this case, it is preferable that the second threshold value increases as the vehicle speed increases.

[0010] Embodiment 4. In any one of embodiments 1 to 3 above, it is preferable that the delay time is set to be longer the smaller the negative pressure in the negative pressure tank at the time the stop request is received.

[0011] Embodiment 5. In any one of embodiments 1 to 4 described above, it is preferable that the delay time is set to be longer the higher the vehicle speed at the time the stop request is received.

[0012] Embodiment 6. In any one of embodiments 1 to 5 above, it is preferable that the vehicle further comprises a drive motor separate from the electric motor. In this case, the control device comprises: an operating determination unit that determines whether the negative pressure in the negative pressure tank is less than a third threshold when the engine is operating in an optimal operating state in a situation where it is undesirable to reduce the output of the engine; and an interrupt control unit that, when the operating determination unit determines that the negative pressure in the negative pressure tank is less than the third threshold, temporarily switches the operating state of the engine from the optimal operating state to an idle operating state in which intake negative pressure to be supplied to the negative pressure tank can be secured, wherein it is preferable that the third threshold is smaller than the first threshold. [Effects of the Invention]

[0013] According to the disclosed vehicle control device, it is possible to suppress the deterioration of the vehicle's energy consumption. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram showing the front of a vehicle to which the control device according to the embodiment is applied. [Figure 2] Figure 1 is a block diagram of the various control devices installed in the vehicle. [Figure 3] Figure 1 is a flowchart illustrating the determination and control actions taken by the control unit when it receives a request to stop the engine. [Figure 4] Figure 1 is a flowchart illustrating the judgment and control processes performed by the control device while the engine is stopped. [Figure 5] Figure 1 is a flowchart illustrating the determination and control processes performed by the control device during engine operation in situations where reducing engine output is undesirable. [Modes for carrying out the invention]

[0015] The vehicle control device as an embodiment will be described with reference to the drawings. The embodiments shown below are merely illustrative, and there is no intention to exclude various modifications or applications of technologies not explicitly shown in the embodiments below. Each component of this embodiment can be modified in various ways without departing from its spirit. Furthermore, components can be selected or combined as needed.

[0016] [1. Overall Structure] Figure 1 is a schematic diagram showing the front of a vehicle 1 to which the control device 25 of this embodiment is applied. The vehicle 1 comprises an engine 2, a generator 4 (electric motor) connected to the rotating shaft 2a of the engine 2, and a brake system 8 having a negative pressure tank 9 (hereinafter referred to as "tank 9") that stores intake negative pressure of the engine 2, and a power booster 10 that uses the negative pressure of tank 9 to boost the brake pedal force. The control device 25 may be mounted on the vehicle 1 as shown in Figure 1, or it may be provided outside the vehicle 1 to remotely control the vehicle 1.

[0017] The control device 25 performs control to restore the negative pressure in tank 9 when the negative pressure in tank 9 decreases (hereinafter referred to as "negative pressure recovery control"). Here, the negative pressure in tank 9 does not mean the pressure value inside tank 9 itself, but rather the difference between atmospheric pressure and the pressure inside tank 9 which is lower than atmospheric pressure. A decrease in the negative pressure in tank 9 means that the difference between the pressure inside tank 9 and atmospheric pressure decreases, and restoring (increasing) the negative pressure in tank 9 means increasing the difference between the pressure inside tank 9 and atmospheric pressure. Hereafter, the control device 25 will also be referred to as the recovery control device 25.

[0018] As shown in FIG. 1 for example, the vehicle 1 may be a hybrid vehicle (Hybrid Electric Vehicle, HEV) or a plug-in hybrid vehicle (Plug-in Hybrid Electric Vehicle, PHEV) equipped with both an engine 2 and a motor 3 (a driving motor separate from the generator 4) as driving power sources and a generator 4 for power generation. A plug-in hybrid vehicle means a hybrid vehicle capable of external charging of the battery 7 or external power supply from the battery 7. A plug-in hybrid vehicle is provided with a charging port (inlet) for inserting a charging cable through which power is supplied from an external charging facility and a socket (outlet) for external power supply.

[0019] In the vehicle 1, the engine 2, the motor 3, and the generator 4 are selectively used or used in combination according to the driving state of the vehicle 1. For example, at the time of starting or low-speed driving, only the motor 3 with a large torque (driving force, rotational driving force) in the low rotation range is used (EV mode). On the other hand, when the charge rate of the battery 7 decreases or when the battery temperature is low and sufficient power cannot be drawn from the battery 7, power generation by the generator 4 using the driving force of the engine 2 is carried out while driving with the driving force of the motor 3 (series mode). Also, at the time of accelerating or high-speed driving with good engine efficiency, the driving force of the engine 2 is mainly used, and the driving force of the motor 3 is used subsidiarily (parallel mode). Each of these driving modes is appropriately selected and implemented by an integrated control device 21 described later.

[0020] The engine 2 is an internal combustion engine (gasoline engine, diesel engine) that uses gasoline or light oil as fuel. By burning a mixture of air and fuel in the combustion chamber 2c, the rotating shaft 2a is rotated to output a rotational driving force. Air is introduced into the combustion chamber 2c from an intake manifold 2i (intake manifold) located on the downstream side of the throttle valve (not shown) in the intake air flow direction. The combustion chamber 2c and the intake manifold 2i are provided with an injector (not shown) that injects fuel toward their interiors. Also, in the combustion chamber 2c, an ignition plug, intake valve, exhaust valve, etc. (all not shown) are provided. The engine 2 is connected, for example, such that the rotating shaft 2a is connected to the wheels 6 (drive wheels) via a transaxle 5, and the rotational driving force is transmitted to the wheels 6 via the transaxle 5.

[0021] The motor 3 is an electric generator (motor - generator) that combines the functions of an electric motor and a generator, and is electrically connected to the battery 7. The motor 3 mainly operates as an electric motor in the power running state, and its rotating shaft 3a rotates with the power of the battery 7 to output a rotational driving force to the wheels 6. The motor 3 operates as a generator in the regeneration state, and charges the battery 7 with regenerative power generated by using the inertial rotation of the wheels 6.

[0022] The motor 3 is connected, for example, such that the rotating shaft 3a is connected to the wheels 6 via a transaxle 5, and the rotational driving force is transmitted to the wheels 6 via the transaxle 5. The engine 2 and the motor 3 are connected in parallel to the wheels 6, and the respective rotational driving forces of the engine 2 and the motor 3 may be individually transmitted to the wheels 6 from different power transmission paths. The battery 7 is, for example, a lithium - ion secondary battery or a nickel - hydrogen secondary battery.

[0023] Generator 4 is a motor-generator (motor-generator) that combines the functions of both an electric motor and a generator, and is electrically connected to battery 7. In the powered state, generator 4 operates as an electric motor, and its rotating shaft 4a rotates using the power from battery 7, outputting rotational driving force to engine 2. Generator 4 is in the powered state, for example, when starting engine 2 or when motoring control, described later, is performed as negative pressure recovery control. In the regenerative state, generator 4 operates as a generator, and charges battery 7 with regenerative power generated using the rotational driving force of engine 2.

[0024] The generator 4 has a rotating shaft 4a connected to the rotating shaft 2a of the engine 2, and transmits the rotational driving force of the generator 4 to the engine 2, or the rotational driving force of the engine 2 is transmitted to the generator 4. The generator 4 may be connected to the engine 2 by a power transmission path different from the power transmission path connecting the engine 2 and the wheels 6. In other words, the generator 4 may be connected to the engine 2 in parallel with the wheels 6, and the rotational driving force of the engine 2 may be transmitted to the generator 4 in addition to the wheels 6.

[0025] In Figure 1, the engine 2 and motor 3 are connected to the front wheels 6 of the vehicle 1 (hereinafter also referred to as "front wheels 6"), but the engine 2 and motor 3 may also be connected to the rear wheels of the vehicle 1 (hereinafter referred to as "rear wheels"), which are not shown. Alternatively, the engine 2 and motor 3 may be connected to both the front wheels 6 and the rear wheels. In other words, the vehicle 1 may be a so-called four-wheel drive vehicle that drives both the front and rear wheels of the vehicle 1.

[0026] The brake system 8 brakes the wheels 6 based on the amount of operation of the brake pedal 11, and as described above, it includes a tank 9 and a power assist device 10.

[0027] The power assist device 10 is a vacuum-type device that assists (enhances) the driver's braking force (brake pedal force) by using the negative pressure of the tank 9. It comprises a master back 12 that amplified the brake pedal force and a master cylinder 13 that generated brake hydraulic pressure. The inside of the master back 12 is divided into two chambers: an atmospheric pressure chamber that is maintained at the same pressure as atmospheric pressure and a vacuum chamber into which the negative pressure from the tank 9 is introduced in conjunction with the operation of the brake pedal 11. The master back 12 amplified the brake pedal force (the force directed from the brake pedal 11 to the master cylinder 13) by the pressure difference between these two chambers.

[0028] A piston (not shown) is inserted into the master cylinder 13, which moves in conjunction with the brake pedal 11. When the driver presses the brake pedal 11, the piston in the master cylinder 13 is driven by the brake pedal force amplified by the master booster 12, pushing out the brake fluid filled in the master cylinder 13. This generates brake hydraulic pressure in the master cylinder 13. The brake hydraulic pressure generated in the master cylinder 13 is transmitted to brake devices 15, such as brake calipers and wheel cylinders, via hydraulic piping 14, which is shown as dotted in Figure 1, and each wheel 6 is braked by the brake devices 15 (braking force is applied to the wheels 6). In Figure 1, the hydraulic piping 14 is connected to a brake device 15 attached to the front wheel 6 of the vehicle 1, but the hydraulic piping 14 may also be connected to a brake device attached to the rear wheel of the vehicle 1.

[0029] Tank 9 is configured to store (accumulate) the intake negative pressure of engine 2 and supply negative pressure to power assist device 10 (the negative pressure chamber of master back 12) in conjunction with the operation of the brake pedal 11. Tank 9 is connected to the negative pressure chamber of master back 12 via a negative pressure passage 16 and to the intake manifold 2i of engine 2 via a negative pressure passage 17. A check valve 18 is interposed in the negative pressure passage 17 to allow pressure release from tank 9 to intake manifold 2i (i.e., supply of negative pressure from intake manifold 2i to tank 9) and to prevent pressure release in the reverse direction.

[0030] As a result, while the negative pressure recovery control by the recovery control device 25 is in operation, if the pressure on the intake manifold 2i side becomes lower than the pressure on the tank 9 side, the intake negative pressure in the intake manifold 2i is supplied to the tank 9. On the other hand, if the pressure on the tank 9 side is lower than the pressure on the intake manifold 2i side, the check valve 18 prevents the supply of negative pressure from the tank 9 side to the intake manifold 2i side. The negative pressure stored in the tank 9 is consumed by being supplied to the power assist device 10 in response to the driver's operation of the brake pedal 11.

[0031] Vehicle 1 is equipped with a negative pressure sensor 19 and a vehicle speed sensor 20. The negative pressure sensor 19 is a sensor that detects the difference (absolute value of the difference) between the pressure inside tank 9 and atmospheric pressure as the negative pressure P of tank 9. The vehicle speed sensor 20 is a sensor that detects the vehicle speed V of vehicle 1 (or the wheel speed equivalent to the vehicle speed).

[0032] As shown in Figure 2, vehicle 1 may also be provided with an integrated control unit 21 in addition to the recovery control unit 25. Both of these control units 21 and 25 are electronic control units (computers) that incorporate a processor (central processing unit), memory (main memory), storage device (storage), interfaces, etc. The content of the control performed by each control unit 21 and 25 is recorded and stored in memory as firmware or application programs, and when a program is executed, the content of the program is expanded into the memory space and executed by the processor.

[0033] The integrated control unit 21 provides integrated control for various in-vehicle devices. For example, the integrated control unit 21 controls the engine 2, motor 3, and generator 4 based on vehicle information, including the vehicle speed V detected by the vehicle speed sensor 20 and the driver's operation information of the vehicle 1.

[0034] Regarding the control of engine 2, the integrated control unit 21 operates engine 2 when it determines, for example, that engine 2 needs to be operated based on vehicle information (for example, when series mode or parallel mode is selected).

[0035] In series mode and parallel mode, the engine 2 operates at optimal or near-optimal efficiency (i.e., near the best fuel consumption point), so sufficient intake negative pressure is not generated in the intake manifold 2i to ensure the negative pressure supplied to the tank 9. Hereafter, this operating state of the engine 2 near the best fuel consumption point will be referred to as the optimal operating state.

[0036] In this embodiment, when the integrated control device 21 determines that the engine 2 needs to be operated, it operates the engine 2 in an optimal operating state. At this time, if it is undesirable to reduce the output of the engine 2 (for example, when the temperature of the engine 2 is low and warm-up is required, or when the temperature of the battery 7 is low and it is necessary to increase the engine output above a predetermined level to compensate for the output), the integrated control device 21 may transmit an operating signal to the recovery control device 25 indicating that the engine 2 is operating under circumstances where a reduction in the output of the engine 2 is undesirable.

[0037] If the integrated control unit 21 determines that engine 2 does not need to be operated while it is running (for example, when switching from series mode or parallel mode to EV mode), it transmits a stop request to the recovery control unit 25, which is a request to stop the operating engine 2. Upon receiving the stop request, the recovery control unit 25 determines whether negative pressure recovery control is necessary and stops engine 2 according to the result of that determination. In addition, after stopping engine 2, the integrated control unit 21 may transmit a stop signal to the recovery control unit 25 indicating that engine 2 is stopped until it determines that engine 2 needs to be operated again.

[0038] In this embodiment, the operating signal is transmitted to the recovery control device 25 continuously (repeatedly) as long as it is determined that the engine 2 needs to be operated and the situation where a decrease in the output of the engine 2 is undesirable continues. The stopped signal is transmitted to the recovery control device 25 continuously after the engine 2 has stopped until it is determined that the engine 2 needs to be operated again. On the other hand, the stop request is transmitted to the recovery control device 25 only once when it is necessary to stop the operating engine 2.

[0039] The recovery control device 25 performs negative pressure recovery control to restore (increase) the negative pressure P in the tank 9 by controlling the engine 2 and the generator 4 respectively when the negative pressure P in the tank 9 decreases. Here, the negative pressure P in the tank 9 decreases (becomes smaller) when supplied to the power booster 10, but is maintained at a generally constant value if it is supplied by the intake negative pressure of the engine 2. However, when the engine 2 is stopped or operating in the optimal operating state, it is no longer supplied by the intake negative pressure, and a deficiency in the negative pressure of the tank 9 is likely to occur.

[0040] In particular, if vehicle 1 is a hybrid vehicle or a plug-in hybrid vehicle, an EV mode that allows driving with engine 2 stopped may be selected. Therefore, there is a higher possibility of insufficient negative pressure in tank 9 compared to a conventional engine vehicle. Insufficient negative pressure in tank 9 can lead to insufficient braking force when vehicle 1 is braking. To avoid insufficient negative pressure, it is conceivable to operate engine 2 immediately when (or just before) insufficient negative pressure occurs to restore the negative pressure using intake negative pressure. However, this negative pressure recovery control restores negative pressure while suppressing deterioration of energy efficiency.

[0041] For example, the recovery control device 25 has a negative pressure sensor 19, a vehicle speed sensor 20, and an integrated control device 21 connected to its input side. The negative pressure P detected by the negative pressure sensor 19, the vehicle speed V detected by the vehicle speed sensor 20, and signals and requests transmitted from the integrated control device 21 are input to the recovery control device 25. The engine 2 and the generator 4 are connected to the output side of the recovery control device 25.

[0042] [2. Control Configuration] The recovery control device 25 of the present embodiment performs three types of determinations regarding the necessity of negative pressure recovery control: determination before stop, determination during stop, and determination during operation. Further, the recovery control device 25 performs any one of three types of control as negative pressure recovery control: delay control, motor running control, and interrupt control, according to the results of these three types of determinations.

[0043] As shown in FIG. 2, the recovery control device 25 is provided with a pre-stop determination unit 26, a delay control unit 27, a determination unit 28 during stop, a motor running control unit 29, a determination unit 30 during operation, and an interrupt control unit 31 as functional elements for performing these determinations and controls. These elements may be realized by an electronic circuit (hardware), may be programmed as software, or may be provided with a part of these functions as hardware and the other part as software.

[0044] When the pre-stop determination unit 26 receives a stop request to stop the operating engine 2, the pre-stop determination is performed. Here, it is determined whether or not the negative pressure P at the time when the recovery control device 25 (pre-stop determination unit 26) receives the stop request from the integrated control device 21 is less than the first threshold value P1. The pre-stop determination unit 26 transmits a signal indicating the determination result (P < P1 or P ≧ P1) to the delay control unit 27. The first threshold value P1 may be a preset fixed value. The first threshold value P1 may be set, for example, to a lower limit value at which the negative pressure P in the tank 9 is considered sufficient (there is sufficient margin in the negative pressure P in the tank 9).

[0045] When the delay control unit 27 receives a signal indicating P < P1 from the pre-stop determination unit 26, that is, when the pre-stop determination unit 26 determines that the negative pressure P is less than the first threshold value P1, the delay control unit 27 performs delay control. In the present embodiment, when the delay control unit 27 receives a signal indicating P < P1 from the pre-stop determination unit 26, after performing the delay control, the delay control unit 27 stops the engine 2 in response to a stop request. On the other hand, when the delay control unit 27 receives a signal indicating P ≥ P1 from the pre-stop determination unit 26, the delay control unit 27 does not perform the delay control and immediately stops the engine 2 (that is, at the time when the stop request is received).

[0046] The delay control is a control that delays the stop of the engine 2 (keeps the engine 2 running) until a predetermined delay time DT elapses from the time when the stop request is received, and secures the intake negative pressure supplied to the tank 9. In the delay control, the engine 2 is controlled in an idle state (idle operation state) in which the intake negative pressure supplied to the tank 9 can be secured within the intake manifold 2i. The delay control unit 27 ends the delay control and stops the engine 2 when the delay time DT elapses from the start time of the delay control.

[0047] The delay time DT may be a preset fixed value or a variable value. The delay time DT in the present embodiment is set according to the negative pressure P and the vehicle speed V at the time when the stop request is received (that is, it is a variable value). When the delay time DT is set according to the negative pressure P, the delay control unit 27 may set the delay time DT longer as the negative pressure P at the time when the stop request is received is smaller. Also, the delay control unit 27 may set the delay time DT shorter as the negative pressure P at the time when the stop request is received is larger.

[0048] As a result, the smaller the negative pressure P, the greater the increase (recovery) of negative pressure P during delay control, making it easier to suppress the motoring control described later, which is performed when the negative pressure P in tank 9 drops while engine 2 is stopped. Also, the larger the negative pressure P (the closer negative pressure P is to the first threshold P1), the shorter the execution time of delay control, thus suppressing unnecessary operation of engine 2.

[0049] When the delay time DT is set according to the vehicle speed V, the delay control unit 27 may set the delay time DT to be longer the higher the vehicle speed V is at the time the stop request is received. Conversely, the delay control unit 27 may set the delay time DT to be shorter the lower the vehicle speed V is at the time the stop request is received.

[0050] During braking, a greater braking force is required as the vehicle speed V increases. Therefore, the delay time DT is set to be longer as the vehicle speed V increases. This means that even if the negative pressure P at the time of receiving a stop request is the same, the amount of increase in negative pressure P during delay control increases when the vehicle speed V at that time is higher (for example, when vehicle 1 is moving rather than when vehicle 1 is stationary). Thus, an appropriate braking force corresponding to the vehicle speed V is applied to the wheels 6 during braking. In addition, the execution time of delay control is shorter as the vehicle speed V decreases, which suppresses unnecessary operation of the engine 2.

[0051] The delay time DT may be set to its upper limit, which is the maximum delay time DTu. The delay control unit 27 may, for example, set the delay time DT to the maximum delay time DTu if the negative pressure P at the time of receiving the stop request is greater than or equal to the boundary threshold Pb and less than the fourth threshold P4, which is smaller than the first threshold P1.

[0052] Here, the boundary threshold Pb is the lower limit of the range of negative pressure P that can ensure sufficient negative pressure is supplied to the power assist device 10 during braking, and may be a fixed value that is set in advance based on the performance of the brake system 8, for example. The boundary threshold Pb is set to a value that is at least smaller than the first threshold P1. The fourth threshold P4 is a value that is set in the range of greater than or equal to the boundary threshold Pb and less than the first threshold P1, and may be a fixed value that is set in advance or a variable value.

[0053] For example, when the negative pressure P is greater than or equal to the fourth threshold value P4, the delay control unit 27 may set the delay time DT to be shorter than the maximum delay time DTu as the negative pressure P is larger, and may also set the delay time DT to be shorter than the maximum delay time DTu as the vehicle speed V is lower. That is, when the negative pressure P is greater than or equal to the fourth threshold value P4, the delay control unit 27 may set the delay time DT to be longer as the negative pressure P is smaller and / or as the vehicle speed V is higher, within a range not exceeding the maximum delay time DTu.

[0054] The engine stop determination unit 28 performs an engine stop determination during the stop of the engine 2. In the engine stop determination, it is determined whether the negative pressure P is less than the second threshold value P2. For example, while the engine stop determination unit 28 is acquiring an engine stop signal from the integrated control device 21, it repeatedly performs the engine stop determination and transmits a signal indicating the determination result (P < P2 or P ≥ P2) to the motor running control unit 29 each time.

[0055] The second threshold value P2 is set to be smaller than the first threshold value P1 related to the implementation of delay control. In this way, since the first threshold value P1 is set larger than the second threshold value P2, it becomes easier to build up the negative pressure in the delay control before the stop of the engine 2, and it becomes less likely that the negative pressure P is determined to be less than the second threshold value P2 in the engine stop determination by the engine stop determination unit 28. Therefore, when it is determined in the engine stop determination that the negative pressure P is less than the second threshold value P2, the implementation of the motor running control performed by the motor running control unit 29 described later is suppressed. Also, since the second threshold value P2 is set smaller than the first threshold value P1, it becomes even less likely that the negative pressure P is determined to be less than the second threshold value P2 in the engine stop determination, and thus the implementation of the motor running control is minimized.

[0056] The second threshold value P2 may be set to be larger as the vehicle speed V is higher within a range that is, for example, not less than the boundary threshold value Pb and less than the first threshold value P1. During braking, as the vehicle speed V is higher, a larger braking force is required. Therefore, by setting the second threshold value P2 to be larger as the vehicle speed V is higher, the motor control is more likely to be implemented as the vehicle speed V is higher. Thus, an early recovery of the negative pressure P is achieved, and an appropriate braking force corresponding to the vehicle speed V during braking is applied to the wheel 6. The second threshold value P2 may be, for example, a variable value that increases as the vehicle speed V increases. The stopped state determination unit 28 acquires the vehicle speed V, sets the second threshold value P2 to be larger within a range where the vehicle speed V is higher and below the first threshold value P1, and performs the stopped state determination based on the set second threshold value P2.

[0057] When the motor control unit 29 receives a signal indicating that P < P2 from the stopped state determination unit 28, in other words, when the stopped state determination unit 28 determines that the negative pressure P is less than the second threshold value P2, the motor control unit 29 performs motor control. The motor control is a control for securing an intake negative pressure that rotates the rotary shaft 2a of the engine 2 and supplies it to the tank 9 by operating the generator 4 in the power running state when receiving a signal indicating that P < P2 from the stopped state determination unit 28.

[0058] The motor control unit 29 may, for example, end the motor control when receiving a signal indicating that P ≥ P2 from the stopped state determination unit 28 after the start of the motor control. In this case, the motor control unit 29 may return the control authority of the generator 4 to the integrated control device 21 as a process of not implementing (ending) the motor control. Alternatively, the motor control unit 29 may end the motor control after a lapse of a predetermined motor running time MT from the start of the motor control. The motor running time MT may be a fixed time set in advance, or may be a variable time set according to the negative pressure P and the vehicle speed V at the time when the stopped state determination is established, similar to the delay time DT.

[0059] During operation determination unit 30 performs the during operation determination during the operation of engine 2 in a situation where it is not preferable to reduce the output of engine 2. In the during operation determination, it is determined whether or not the negative pressure P is less than the third threshold value P3. For example, while acquiring the during operation signal from the integrated control device 21, the during operation determination unit 30 repeatedly performs the during operation determination and transmits to the interrupt control unit 31 each time a signal indicating the determination result (P < P3 or P ≧ P3). The third threshold value P3 is a value smaller than the first threshold value P1 related to the implementation of the delay control, and is set to, for example, the boundary threshold value Pb.

[0060] When the interrupt control unit 31 receives a signal indicating P < P3 from the during operation determination unit 30, in other words, when the during operation determination unit 30 determines that the negative pressure P is less than the third threshold value P3, the interrupt control unit 31 performs interrupt control. The interrupt control is a control that, when receiving a signal indicating P < P3 from the during operation determination unit 30, temporarily switches the operating state of engine 2 from the optimal operating state to the idle state and operates engine 2. In other words, the interrupt control interrupts the control of engine 2 (that is, the optimal operation control that operates engine 2 in the optimal operating state) performed by the integrated control device 21 in a situation where it is not preferable to reduce the output of engine 2, and controls engine 2 to operate in the idle state.

[0061] For example, after the start of the interrupt control, the interrupt control unit 31 may end the interrupt control when receiving a signal indicating P ≧ P3 from the during operation determination unit 30. In this case, as a process of not performing (ending) the interrupt control, the interrupt control unit 31 may return the control right of engine 2 to the integrated control device 21. Alternatively, the interrupt control unit 31 may end the interrupt control after a lapse of a predetermined interrupt time IT from the start of the interrupt control. The interrupt time IT may be a fixed time set in advance, or may be a variable time set according to the negative pressure P and the vehicle speed V at the time of the during operation determination, similar to the delay time DT.

[0062] [3. Flowchart] Figures 3 to 5 are flowcharts illustrating the determination and control processes performed by the recovery control device 25. In Figures 3 to 5, it is assumed that various pieces of information (negative pressure P, vehicle speed V) are input to the recovery control device 25 at the start of each flowchart (in each calculation cycle).

[0063] Figure 3 is a flowchart illustrating the determination and control procedures performed when a stop request is received from the integrated control device 21. In the flowchart of Figure 3, the timer T, which counts the elapsed time since the stop request was received, is initially set to 0.

[0064] In step S10 of the flow in Figure 3, a determination is made as to whether the negative pressure P is less than the first threshold P1, i.e., a pre-stop determination is made. If it is determined in step S10 that the negative pressure P is not less than the first threshold P1, it is determined that recovery of the negative pressure P by delay control is unnecessary, and the process proceeds to step S11, where the engine 2 is stopped and this flow ends.

[0065] On the other hand, if it is determined in step S10 that the negative pressure P is less than the first threshold P1, the timer T starts counting in step S12, and in step S13 it is determined whether the negative pressure P at this point (i.e., when the stop request is received) is less than the fourth threshold P4. If it is determined in step S13 that the negative pressure P is less than the fourth threshold P4, the delay time DT is set to the maximum delay time DTu in step S14. On the other hand, if it is determined in step S13 that the negative pressure P is not less than the fourth threshold P4, the delay time DT is set in step S15 according to the negative pressure P and the vehicle speed V.

[0066] In the following step S16, as part of the delay control implementation process, engine 2 is operated in an idle state. That is, the stopping of engine 2 based on the stop request is delayed, and engine 2 is operated in an idle state. Then, in step S17, it is determined whether the value (time) of timer T is longer than the set delay time DT. If, immediately after the start of delay control, it is determined in step S17 that the value of timer T is not longer than the delay time DT, the process returns to step S16, the delay control implementation process continues, and the determination in step S17 is performed again. Then, the processes of steps S16 and S17 are repeated until the delay time DT has elapsed.

[0067] Subsequently, if, after the delay time DT has elapsed since the stop request was received, step S17 determines that the value of timer T is longer than the delay time DT (i.e., the delay time DT has elapsed since the start of delay control), then, as a termination process for delay control, step S18 stops engine 2 and resets timer T (set to T=0), ending this flow. The recovery control device 25 then performs the flow shown in Figure 4.

[0068] Figure 4 is a flowchart illustrating the determination and control procedures performed when a stop signal is transmitted from the integrated control device 21 (i.e., when the engine 2 is stopped). The flow in Figure 4 is repeatedly performed at a predetermined calculation cycle when a stop signal is transmitted.

[0069] In step S20 of the flow in Figure 4, the second threshold P2 is set to be larger the higher the vehicle speed V at that time, within the range where the second threshold P2 is smaller than the first threshold P1. In the following step S21, a determination is made as to whether the negative pressure P is less than the set second threshold P2, i.e., a stop condition is checked.

[0070] If it is determined in step S21 that the negative pressure P is less than the second threshold P2, the process proceeds to step S22, where the generator 4 is operated in the powered state as part of the motoring control process, and this flow is returned. As a result, the generator 4 rotates the rotation shaft 2a of the engine 2, ensuring that the engine 2 has intake negative pressure to supply to the tank 9, and the negative pressure P in the tank 9 increases.

[0071] Then, in the next calculation cycle and beyond, if the negative pressure P of the tank 9 recovers and it is determined in step S21 that the negative pressure P is not less than the second threshold P2, the process proceeds to step S23, where, as a motor control non-implementation process (termination process), for example, the generator 4 is stopped and control of the generator 4 is returned to the integrated control device 21, and this flow returns.

[0072] Figure 5 is a flowchart illustrating the determination and control procedures performed when the integrated control device 21 transmits an operating signal (i.e., when the engine 2 is operating in its optimal operating state in a situation where it is undesirable to reduce the output of the engine 2). The flow in Figure 5 is repeated at a predetermined calculation cycle when the operating signal is transmitted.

[0073] In step S30 of the flow in Figure 5, a determination is made as to whether the negative pressure P is less than the third threshold P3, i.e., whether the system is operating. If it is determined in step S30 that the negative pressure P is less than the third threshold P3, the process proceeds to step S31, and as an interrupt control process, the operating state of the engine 2 is temporarily switched from the optimal operating state to the idle state, and this flow is returned. In the engine 2, this ensures that intake negative pressure is supplied to the tank 9, and the negative pressure P in the tank 9 increases.

[0074] Then, in the next calculation cycle and beyond, if the negative pressure P in tank 9 recovers and it is determined in step S30 that the negative pressure P is not less than the third threshold P3, the process proceeds to step S32, where, as an interrupt control non-implementation process (termination process), control of engine 2 is returned to the integrated control device 21, and this flow returns. As a result, engine 2 returns to its optimal operating state.

[0075] [4. Effects] (1) In the recovery control device 25 described above, the second threshold P2 for the implementation of motoring control is set to be smaller than the first threshold P1 for the implementation of delay control. This makes it easier to generate negative pressure with delay control before stopping the engine 2, thus making it less likely for motoring control to be implemented while the engine 2 is stopped. Therefore, it is possible to suppress the power consumption of the battery 7 associated with the implementation of motoring control, and to suppress the deterioration of the vehicle's energy efficiency.

[0076] (2) In the recovery control device 25 described above, the second threshold P2 increases as the vehicle speed V increases. As a result, as the vehicle speed V increases, it becomes easier for the negative pressure P to be determined to be less than the second threshold P2 during the stop condition check, thus enabling early recovery of the negative pressure P. Therefore, when braking while the vehicle 1 is in motion, where the braking force required during braking is relatively large (for example, when the vehicle 1 is in EV mode without the engine 2 operating), an appropriate braking force corresponding to the vehicle speed V can be applied to the wheels 6. Furthermore, when the vehicle 1 is stopped or driving at a low speed, where the braking force required during braking is relatively small, it becomes less likely for the negative pressure P to be determined to be less than the second threshold P2 during the stop condition check, thus enabling more appropriate suppression of deterioration in energy consumption.

[0077] (3) If the delay time DT is set to be longer the smaller the negative pressure P at the time the stop request is received, the amount of increase (recovery) of the negative pressure P corresponding to the negative pressure P at the time the stop request is received can be obtained by the delay control, making it easier to more appropriately suppress the implementation of motoring control while the engine 2 is stopped.

[0078] (4) If the delay time DT is set to be longer the higher the vehicle speed V at the time the stop request is received, the amount of increase in negative pressure P due to delay control can be increased as the vehicle speed V increases. Therefore, when braking a vehicle 1 that requires a relatively large braking force during braking is in motion, an appropriate braking force can be applied to the wheels 6.

[0079] (5) In the recovery control device 25 described above, interrupt control is performed if the negative pressure P is determined to be less than the third threshold P3 in an operating condition determination performed when the engine 2 is operating in a situation where it is undesirable to reduce the output of the engine 2. Furthermore, the third threshold P3 for the implementation of the interrupt control is set to be smaller than the first threshold P1 for the implementation of the delay control. This makes it possible to minimize the implementation of interrupt control when the engine 2 is operating in an optimal operating state (for example, when the charge level of the battery 7 is low or when the vehicle 1 is running in series mode when the battery temperature is low), while applying appropriate braking force to the wheels 6 when braking.

[0080] [5. Others] The configuration of the recovery control device 25 and vehicle 1 described above is an example. Furthermore, the control performed by the recovery control device 25 described above is an example. For example, vehicle 1 may be a series hybrid vehicle in which the engine 2 is used only for power generation. In other words, the engine 2 provided in vehicle 1 does not have to be the driving source for vehicle 1. The "electric motor" described in the claims may be at least an electric motor connected to the rotating shaft 2a of the engine 2, and does not have to be a generator 4 that combines the functions of an electric motor and a generator. Also, vehicle 1 may be an engine-powered vehicle equipped only with the engine 2 as the driving source, that is, without a motor 3.

[0081] The second threshold P2 for motoring control does not have to be a variable value that increases with increasing vehicle speed V. Alternatively, the second threshold P2 may include a second driving threshold P2a used when vehicle 1 is in motion and a second stopping threshold P2b used when vehicle 1 is stopped, and the second driving threshold P2a may be set to be larger than the second stopping threshold P2b, within the range where it is smaller than the first threshold P1. With such a configuration, the frequency at which the negative pressure P is determined to be less than the second threshold P2 in the stopping condition can be changed between when vehicle 1 is in motion, where the braking force required during braking is relatively large, and when vehicle 1 is stopped, where the braking force required during braking is relatively small. This makes it possible to achieve both the application of appropriate braking force and the appropriate suppression of deterioration in energy consumption. Note that when vehicle 1 is an engine vehicle, the second driving threshold P2a is used, for example, during coasting.

[0082] If the brake system 8 of the vehicle 1 is equipped with a device that secures a negative pressure separate from the intake negative pressure of the engine 2, the operation determination and interrupt control performed by the recovery control device 25 may be omitted. In this case, the recovery control device 25 does not need to be equipped with an operation determination unit 30 and an interrupt control unit 31.

[0083] The delay time DT does not have to be a variable time set according to the negative pressure P, nor does it have to be a variable time set according to the vehicle speed V. A maximum delay time DTu does not have to be set for the delay time DT. The third threshold P3 only needs to be at least smaller than the first threshold P1, and does not have to be the boundary threshold Pb. [Industrial applicability]

[0084] This invention is applicable to the manufacturing industry of vehicle control systems, and also to the manufacturing industry of vehicles to which such control systems are applied. [Explanation of symbols]

[0085] 1 vehicle 2 engines 2a Rotation axis 3. Motor (Motor for driving) 4. Generator (electric motor) 8 Brake System 9. Tank (Vacuum Tank) 10 booster 25 Recovery control device (control device) 26 Pre-stop judgment section 27 Delay Control Unit 28 Stopping determination section 29 Motoring Control Unit 30 Operation determination unit 31 Interrupt Control Unit DT Delay Time P Negative pressure P1 First threshold P2 Second threshold P2a Second driving threshold P2b Second stopping threshold P3 (Third Threshold) V Vehicle speed

Claims

1. The engine and An electric motor connected to the rotating shaft of the aforementioned engine, A control device for a vehicle comprising a vacuum tank for accumulating intake vacuum pressure of the engine and a brake system having a power booster that uses the vacuum pressure of the vacuum tank to boost the brake pedal force, A pre-stop determination unit, which determines whether the negative pressure in the negative pressure tank at the time the stop request is received is below a first threshold, when a stop request is received which is a request to stop the engine that is in operation, If the pre-stop determination unit determines that the negative pressure in the negative pressure tank is below the first threshold, the delay control unit delays the stopping of the engine for a predetermined delay time from the time the stop request is received to secure intake negative pressure to be supplied to the negative pressure tank, A stop determination unit that determines whether the negative pressure in the negative pressure tank is below a second threshold while the engine is stopped, The engine includes a motoring control unit that, when the stop determination unit determines that the negative pressure in the negative pressure tank is less than the second threshold, rotates the rotating shaft of the engine with the electric motor to secure intake negative pressure to be supplied to the negative pressure tank, The second threshold is smaller than the first threshold. A vehicle control device characterized by the following features.

2. The second threshold includes a second driving threshold used while the vehicle is in motion and a second stopping threshold used while the vehicle is stopped. The second driving threshold is greater than the second stopping threshold. A vehicle control device according to claim 1, characterized in that

3. The vehicle further comprises a separate traction motor from the electric motor, The second threshold increases as the vehicle speed increases. A vehicle control device according to claim 1, characterized in that

4. The delay time is set to be longer the lower the negative pressure in the negative pressure tank at the time the stop request is received. A vehicle control device according to any one of claims 1 to 3, characterized in that

5. The delay time is set to be longer the higher the vehicle speed at the time the stop request is received. A vehicle control device according to any one of claims 1 to 3, characterized in that

6. The vehicle further comprises a separate traction motor from the electric motor, The control device is An operating determination unit that determines whether the negative pressure in the negative pressure tank is below a third threshold while the engine is operating in its optimal operating state in a situation where it is undesirable to reduce the output of the engine, The engine includes an interrupt control unit that, when the operating determination unit determines that the negative pressure in the negative pressure tank is below the third threshold, temporarily switches the engine's operating state from the optimal operating state to an idle operating state that can secure intake negative pressure to be supplied to the negative pressure tank. The third threshold is smaller than the first threshold. A vehicle control device according to any one of claims 1 to 3, characterized in that

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