Brake system and vehicle

Abstract

To provide a brake system and a vehicle capable of using a mechanical vacuum pump even in a hybrid vehicle. [Solution] A brake system 17 for a hybrid vehicle having an internal combustion engine 12 and a motor 15 as power sources comprises a brake pedal 21, a master cylinder 25 that converts external force into hydraulic pressure, a mechanical vacuum pump 23 driven by the internal combustion engine 12, a brake booster 22 having a first chamber 22a connected to the mechanical vacuum pump 23 and a second chamber 22b connected to the atmosphere, and amplifying the force generated by operation of the brake pedal 21b by the pressure difference between the first chamber 22a and the second chamber 22b and transmitting it to the master cylinder 25, a pressure sensor 30 that detects the pressure in the first chamber 22a, and a control unit 18 that starts the internal combustion engine 12 when the internal combustion engine 12 is stopped at the start of deceleration operation and the pressure detected by the pressure sensor 30 is higher than a predetermined pressure.

Description

[Technical field]

[0001] The present invention relates to a brake system for a hybrid electric vehicle (HEV) and a vehicle equipped with the brake system. [Background technology]

[0002] In a braking system used in a vehicle, a technology is known in which the force generated by the operation of the brake pedal is amplified by a brake booster and transmitted to a master cylinder in order to ensure the necessary brake assist force. Such a brake booster amplifies the force generated by the operation of the brake pedal by the pressure difference between atmospheric pressure and negative pressure. For example, in a braking system of a vehicle powered by an internal combustion engine such as a diesel engine, negative pressure can be generated by a mechanical vacuum pump.

[0003] On the other hand, electric vehicles, which do not have an internal combustion engine, employ electric vacuum pumps.

[0004] Hybrid vehicles have an internal combustion engine, but the internal combustion engine may be stopped during driving depending on the driving mode. Therefore, in hybrid vehicles, since it may not be possible to drive a mechanical vacuum pump, an electric vacuum pump is used (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-100569 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, electric vacuum pumps are more expensive than mechanical vacuum pumps, and the cost of a vehicle increases when two electric vacuum pumps are installed to ensure redundancy.

[0007] SUMMARY OF THE PRESENT DISCLOSURE In view of the above, an object of the present invention is to provide a brake system and a vehicle that are capable of using a mechanical vacuum pump even in a hybrid vehicle. [Means for solving the problem]

[0008] According to one aspect of the present invention, a brake system is a brake system for a hybrid vehicle having an internal combustion engine and a motor as a power source, the brake system including a brake pedal, a master cylinder that converts an external force into a hydraulic pressure, a mechanical vacuum pump driven by the internal combustion engine, an electric vacuum pump driven by electricity; a brake booster having a first chamber connected to the mechanical vacuum pump and a second chamber connected to the atmosphere, amplifying a force generated by operation of the brake pedal by a pressure difference between the first chamber and the second chamber and transmitting the force to the master cylinder; a pressure sensor for detecting the pressure in the first chamber; and a brake booster for starting the internal combustion engine when the pressure detected by the pressure sensor is higher than a predetermined pressure when the internal combustion engine is stopped at the start of a deceleration operation. and driving the mechanical vacuum pump. A control unit. Effect of the Invention

[0009] According to the present invention, it is possible to provide a brake system and a vehicle that can use a mechanical vacuum pump even in a hybrid vehicle. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is an explanatory diagram showing a schematic configuration of a vehicle according to one embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram that shows a schematic configuration of a brake system for a vehicle according to one embodiment. [Diagram 3]FIG. 3 is a flow diagram illustrating an example of a deceleration operation using a brake system of a vehicle according to an embodiment. [Figure 4] FIG. 4 is a flow chart showing another example of a deceleration operation using a brake system of a vehicle according to another embodiment and an example of a failure determination of the first vacuum pump during the deceleration operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A vehicle 1 according to an embodiment of the present invention will be described below with reference to Figs. 1 to 3. Fig. 1 is an explanatory diagram that shows a schematic configuration of the vehicle 1. Fig. 2 is an explanatory diagram that shows a schematic configuration of a brake system 17 used in the vehicle 1. Fig. 3 is a flow chart showing an example of a deceleration operation using the brake system 17 of the vehicle 1. Note that in each figure, the configuration is enlarged, reduced, or omitted as appropriate.

[0012] As shown in Fig. 1, the vehicle 1 is a hybrid electric vehicle (HEV) equipped with an internal combustion engine 12, a first motor 13, and a second motor 15 as power sources. The vehicle 1 is, for example, a truck. The vehicle 1 is, for example, a flatbed vehicle, a wing vehicle, a covered vehicle, a UNIC vehicle, an on-board vehicle, a tanker truck, etc. Note that the vehicle 1 is not limited to a truck as long as it is an HEV, and may be a bus, a passenger car, a special purpose vehicle, etc.

[0013] The vehicle 1 includes a battery 11, an internal combustion engine 12, a first motor 13, a clutch 14 serving as a switching device, a second motor 15, a driving unit 16, a brake system 17, and a control unit 18.

[0014] The battery 11 is a power source for the vehicle 1. The battery 11 is connected to the first motor 13 and the second motor 15 via an inverter. For example, a lithium ion battery, a solid lithium ion battery, a graphene secondary battery, or the like is used as the battery 11. For example, the battery 11 includes a battery module having a plurality of battery cells.

[0015] The internal combustion engine 12 is an engine such as a diesel engine or a gasoline engine. The internal combustion engine 12 is, for example, a multi-cylinder engine having multiple cylinders. The internal combustion engine 12 is connected to a fuel tank. The internal combustion engine 12 is supplied with fuel from the fuel tank, and when it operates, it generates power (torque) that serves as a driving force.

[0016] The internal combustion engine 12 is connected to a traveling unit 16 via a clutch 14, for example, and drives the traveling unit 16. The internal combustion engine 12 is also connected to a first motor 13, and drives the first motor 13 to generate electricity.

[0017] The first motor 13 includes, for example, a motor case, a stator fixed to the motor case, and a rotor fixed to a shaft supported by the motor case. For example, the first motor 13 is connected to the battery 11 via an inverter.

[0018] A main shaft of the first motor 13 is connected to the internal combustion engine 12. The first motor 13 is configured to be able to generate electricity using the power of the internal combustion engine 12. That is, the first motor 13 functions as a generator when a rotational force is input from the internal combustion engine 12 to the main shaft. In addition, the first motor 13 charges the battery 11 with the electric power generated by absorbing the torque of the internal combustion engine 12.

[0019] The first motor 13 may function as a drive motor that drives the traveling unit 16 by receiving power from the battery 11. Furthermore, the first motor 13 may function as a starter that starts the internal combustion engine 12. In other words, the first motor 13 can function as a power source, a generator, or a starter for the vehicle 1 depending on the driving state.

[0020] The inverters are provided between the battery 11 and the first motor 13 and between the battery 11 and the second motor 15, and each include a power element, a capacitor, a control circuit, etc. The inverter converts the DC voltage from the battery 11 into an AC voltage and supplies three-phase current to the motors 13 and 15. The inverter also converts the AC voltage generated by the motor 13 into a DC voltage.

[0021] The clutch 14 is, for example, a dry friction clutch provided on the output side of the internal combustion engine 12. The clutch 14 is configured to be able to connect and disconnect the power transmission path from the internal combustion engine 12 to the driving unit 16 under the control of the control unit 18.

[0022] The second motor 15 includes a motor case, a stator fixed to the motor case, and a rotor fixed to a shaft supported by the motor case. The second motor 15 is connected to the traveling unit 16. The second motor 15 is also connected to the battery 11 via an inverter. The second motor 15 receives power from the battery 11 and functions as a drive motor that rotates the shaft of the traveling unit 16. In other words, the second motor 15 serves as a power source for the vehicle 1.

[0023] The running unit 16 includes a drive shaft, an automatic transmission, a power transmission device, front wheels, and rear wheels. For example, an automatic transmission is detachably connected to the output shaft of the internal combustion engine 12 via a clutch 14, and the left and right front wheels and rear wheels, which are driving wheels, are connected to the output shaft of the automatic transmission via a power transmission device including a propeller shaft, a differential gear, a transfer, etc. The running unit 16 changes the speed of the power generated by the rotation of the internal combustion engine 12 transmitted via the clutch 14 at a predetermined gear ratio by the automatic transmission, and transmits it to the front wheels and rear wheels via the power transmission device.

[0024] The brake system 17 is a foot brake and includes a brake pedal 21, a brake booster 22, a first vacuum pump 23, a second vacuum pump 24, a master cylinder 25, a hydraulic circuit 26, a plurality of disc rotors 27, a plurality of brake pads 28, a plurality of brake calipers 29, a pressure sensor 30, and a detection sensor 31.

[0025] The brake pedal 21 is an interface of the brake system 17, and when operated by the driver's foot, the operating force is increased according to a pedal ratio and the force is transmitted to a brake booster 22.

[0026] The brake booster 22 amplifies the force generated by the operation of the brake pedal 21. For example, the brake booster 22 has a first chamber 22a and a second chamber 22b therein. The first chamber 22a is set to a negative pressure lower than atmospheric pressure by a first vacuum pump 23 and / or a second vacuum pump 24, and the second chamber 22b is set to atmospheric pressure. The first chamber 22a is disposed on the master cylinder 25 side, and the second chamber 22b is disposed on the brake pedal 21 side. The brake booster 22 amplifies the force generated by the operation of the brake pedal 21 by the pressure difference between the first chamber 22a and the second chamber 22b, and transmits the force to the master cylinder 25.

[0027] The first vacuum pump 23 is a mechanical vacuum pump. The first vacuum pump 23 is driven by the internal combustion engine 12. The first vacuum pump 23 is fluidly connected to the first chamber 22a of the brake booster 22. When driven, the first vacuum pump 23 makes the first chamber 22a have a predetermined pressure (negative pressure) lower than atmospheric pressure.

[0028] The second vacuum pump 24 is, for example, an electric vacuum pump, and is driven by power supplied from the battery 11. The second vacuum pump 24 is fluidly connected to the first chamber 22a of the brake booster 22. When driven, the second vacuum pump 24 makes the first chamber 22a have a predetermined pressure (negative pressure) lower than atmospheric pressure.

[0029] The master cylinder 25, for example, has a piston therein and converts an external force applied to the piston into hydraulic pressure. The master cylinder 25 is connected to a hydraulic circuit 26. The master cylinder 25 boosts the hydraulic pressure in the hydraulic circuit 26 by driving the piston with a force generated by operation of the brake pedal 21 and amplified by the brake booster 22.

[0030] The hydraulic circuit 26 is connected to, for example, the master cylinder 25 and a plurality of brake calipers 29, and hydraulically drives the plurality of brake calipers 29. For example, the hydraulic circuit 26 includes a piping section 26a that fluidly connects the master cylinder 25 and the plurality of brake calipers 29, and a hydraulic control section 26b that includes a valve or the like for performing hydraulic control.

[0031] The multiple disc rotors 27 are provided, for example, on the front and rear wheels of the traveling part 16. The brake pads 28 are pressed against the disc rotors 27, thereby generating a frictional force between the brake pads 28 and the disc rotors 27. The brake caliper 29 moves the brake pads 28 relative to the disc rotor 27. The brake caliper 29 is driven in response to the hydraulic pressure of the hydraulic circuit 26, thereby moving the brake pads 28 between a position where the brake pads 28 are retracted from the disc rotor 27 and a position where the brake pads 28 are pressed against the disc rotor 27.

[0032] The pressure sensor 30 detects the pressure in the first chamber 22a, and outputs to the control unit 18 a signal corresponding to the detected pressure value.

[0033] The detection sensor 31 detects the operation of the brake pedal 21, and outputs a signal corresponding to the detected information to the control unit 18.

[0034] The control unit 18 is a device that performs arithmetic processing, and includes various processing circuits such as an input / output device, a storage device (ROM, RAM, non-volatile RAM, etc.), and a central processing unit (CPU). The control unit 18 executes various programs to function as a driving control device, a deceleration operation control device, a vehicle state detection device, etc. The control unit 18 may be provided in the vehicle 1, or a part or the whole of the control unit 18 may be provided in another external terminal. For example, the control unit 18 may be part of an ECU that controls the internal combustion engine 12. Furthermore, the control unit 18, which serves as a deceleration operation control device, may be configured to be included in part of the brake system 17.

[0035] The control unit 18 is connected to various sensors such as a pressure sensor 30 and a detection sensor 31, and receives output signals from these devices. The control unit 18 is also connected to the internal combustion engine 12, the first motor 13, the clutch 14, the second motor 15, and the second vacuum pump 24, and controls the operations of these elements.

[0036] For example, the control unit 18 controls the driving of the vehicle 1 based on operation information such as accelerator operation information of the vehicle 1 and various detection values. That is, the control unit 18 transmits control signals to each unit to perform control processes required for various operations such as output control of the motors 13 and 15, control of the amount of power generated by the first motor 13, switching control of the clutch 14, and operation control of the internal combustion engine 12. For example, the control unit 18 controls the amount of fuel injection of the internal combustion engine 12 to control the torque and rotation speed generated by the internal combustion engine 12. The control unit 18 also controls the connection and disconnection of the clutch 14 to switch the connection state of the power source and switch the driving mode. The control unit 18 also controls the output of the motors 13 and 15.

[0037] For example, the control unit 18 drives the vehicle 1 in a plurality of different driving modes that appropriately combine the plurality of power sources, the first motor 13, the second motor 15, and the internal combustion engine 12, depending on the driving state. For example, in addition to a first driving mode in which the internal combustion engine 12 is stopped and the second motor 15 is used as a power source, the control unit 18 controls the vehicle 1 by switching among a plurality of different driving modes depending on the driving state, such as a driving mode in which both the first motor 13 and the second motor 15 are used as power sources, a driving mode in which either one or both of the first motor 13 and the second motor 15 and the internal combustion engine 12 are used as power sources, and a driving mode in which only the internal combustion engine 12 is used as a power source.

[0038] Furthermore, when the brake pedal 21 is operated, the control unit 18 controls the brake system 17 as a deceleration operation. As a specific example, when the detection sensor 31 detects the operation of the brake pedal 21, the control unit 18 controls the drive of the first vacuum pump 23 and / or the second vacuum pump 24 so that the pressure in the first chamber 22a of the brake booster 22 becomes a predetermined pressure (required negative pressure) lower than the atmospheric pressure, which is the pressure in the second chamber 22b. Here, the predetermined pressure is the pressure (required negative pressure) required to drive the brake system 17.

[0039] As an example of deceleration operation, when the control unit 18 detects operation of the brake pedal 21 by the detection sensor 31, and the pressure in the first chamber 22a detected by the pressure sensor 30 is higher than the required pressure, i.e., the detected negative pressure has not reached the required negative pressure, and when the internal combustion engine 12 is stopped, such as in the first driving mode in which the vehicle runs on the second motor 15, the control unit 18 starts the stopped internal combustion engine 12 and drives the first vacuum pump 23.

[0040] An example of the deceleration operation of the brake system 17 according to the embodiment will be described below with reference to the flow chart of FIG. 3. First, when the driver operates the brake pedal 21, the detection sensor 31 detects the operation of the brake pedal 21 and outputs a signal. When the control unit 18 detects the operation of the brake pedal 21 by the output signal from the detection sensor 31 (step ST11), it determines the start of the deceleration operation. Next, the control unit 18 determines whether the internal combustion engine 12 is stopped (step ST12). When the control unit 18 determines that the internal combustion engine 12 is stopped (YES in step ST12), it determines whether the pressure (negative pressure) of the first chamber 22a detected by the pressure sensor 30 is higher than the pressure (necessary negative pressure) required to drive the brake system 17 (step ST13). Here, the pressure (necessary negative pressure) required to drive the brake system 17 is the pressure (negative pressure) of the first chamber 22a that can amplify the force generated by the operation of the brake pedal 21 to a predetermined force by the brake booster 22. For example, the pressure required to activate the brake system 17 is preset and stored in a memory device of the control unit 18 .

[0041] When the pressure detected by the pressure sensor 30 is higher than the required pressure (YES in step ST13), the control unit 18 starts the stopped internal combustion engine 12 and starts the first vacuum pump 23 (step ST14). By driving the first vacuum pump 23, the pressure in the first chamber 22a drops to or below the required pressure (required negative pressure), and the pressure difference between the first chamber 22a and the second chamber 22b becomes the desired pressure difference. As a result, the force generated by the operation of the brake pedal 21 is amplified by the brake booster 22, and the piston of the master cylinder 25 is operated with a predetermined force, so that the hydraulic pressure in the hydraulic circuit 26 becomes the desired pressure. Therefore, the brake caliper 29 is driven by the hydraulic pressure in the hydraulic circuit 26, and the brake pad 28 is pressed against the disc rotor 27, and the vehicle 1 is decelerated.

[0042] During deceleration, the driver operates the brake pedal 21 as braking until the vehicle 1 reaches a desired vehicle speed or stops. Therefore, the control unit 18 monitors the release of the brake pedal 21 by the driver based on the output signal of the detection sensor 31, and determines whether braking has ended (step ST15). As a specific example, the control unit 18 determines whether the operation of the brake pedal 21 has been released based on the output signal from the detection sensor 31 as the braking end determination. When it is determined based on the output signal from the detection sensor 31 that the operation of the brake pedal 21 has been released (YES in step ST15), the control unit 18 determines the completion of the deceleration operation of the vehicle 1 (step ST16). Note that, when it cannot be determined based on the output signal from the detection sensor that the operation of the brake pedal 21 has been released (NO in step ST15), the control unit 18 continues to monitor the output signal from the detection sensor 31.

[0043] In step ST12, if the internal combustion engine 12 is operating (NO in step ST12), the first vacuum pump 23 is operating, so the control unit 18 determines that the pressure in the first chamber 22a is equal to or lower than the required pressure (required negative pressure), and performs processing from step ST15 onwards. In addition, in step ST13, if the pressure detected by the pressure sensor 30 is equal to or lower than the required pressure, the pressure in the first chamber 22a is the desired negative pressure, so the control unit 18 does not start the internal combustion engine 12 (first vacuum pump), and performs processing from step ST15 onwards.

[0044] Also, for example, the control unit 18 judges whether the internal combustion engine 12 was stopped at the start of the completed deceleration operation, that is, at the time of the actuation of the brake pedal 21 detected in ST11 (step ST17). If the internal combustion engine 12 was stopped when the brake pedal 21 was actuated (YES in step ST17), it is judged whether the current state of the vehicle 1 satisfies the stop condition of the internal combustion engine 12 (step ST18). If the state of the vehicle 1 satisfies the stop condition of the internal combustion engine 12 (YES in step ST18), the control unit 18 stops the internal combustion engine 12 (step ST19). Note that if the internal combustion engine 12 is operating when the brake pedal 21 is actuated (NO in step ST17) or if the stop condition of the internal combustion engine 12 is not satisfied (NO in step ST18), the operation of the internal combustion engine 12 is continued. In this way, during deceleration operation, the control unit 18 determines whether the first chamber 22a and the second chamber 22b of the brake booster 22 have the desired pressure difference when the internal combustion engine 12 is stopped, and if the desired pressure difference is not reached, the control unit 18 starts the internal combustion engine 12 to drive the first vacuum pump 23 and create negative pressure in the first chamber 22a.

[0045] According to the vehicle 1 having the brake system 17 configured in this manner, even if the vehicle 1 is an HEV powered by the internal combustion engine 12 and the second motor 15, a mechanical vacuum pump can be used for the first vacuum pump 23 that generates a negative pressure in the brake booster 22 that generates the necessary brake assist force. The brake system 17 can reduce the manufacturing cost of the vehicle 1 by using a mechanical vacuum pump that is more cost-effective than an electric vacuum pump. In particular, it is assumed that the vehicle 1 uses two vacuum pumps from the viewpoint of ensuring redundancy. In the vehicle 1 of the embodiment, the first vacuum pump 23 is a mechanical vacuum pump and the second vacuum pump 24 is an electric vacuum pump, thereby reducing costs compared to a configuration in which two electric vacuum pumps are installed. In addition, in the vehicle 1, when a malfunction occurs in the first vacuum pump 23 or the internal combustion engine 12, the second vacuum pump 24 can be driven by power from the battery 11, so that the brake booster 22 can reliably generate a negative pressure that generates the necessary brake assist force during the deceleration operation of the brake system 17. Therefore, the brake system 17 can ensure safety and redundancy in addition to reducing costs.

[0046] As described above, according to the brake system 17 and vehicle 1 of one embodiment of the present invention, when the internal combustion engine 12 is stopped during deceleration operation and the negative pressure is not the desired pressure, the internal combustion engine 12 is started, so that a mechanical vacuum pump can be used even in a hybrid vehicle.

[0047] The present invention is not limited to the above-described embodiment. For example, in the above-described example, the control unit 18 starts the internal combustion engine 12 and drives the first vacuum pump 23 to make the pressure in the first chamber 22a equal to or lower than the required pressure when the brake pedal 21 is operated. However, the brake system 17 may drive the first vacuum pump 23 and determine a failure of the first vacuum pump 23 from the pressure value in the first chamber 22a after the first vacuum pump 23 is driven, and may start the second vacuum pump 24 when the pressure in the first chamber 22a does not become equal to or lower than the required pressure by only driving the first vacuum pump 23.

[0048] Another embodiment of the deceleration operation using the brake system 17 of the vehicle 1 will be described with reference to the flow chart shown in FIG.

[0049] First, when the control unit 18 determines that the brake pedal 21 has been operated based on a signal output from the detection sensor 31 (step ST21), the control unit 18 starts the first vacuum pump 23 (step ST22). Note that the operations of steps ST21 and ST22 are the same as, for example, the operations of steps ST11 to ST14 described above.

[0050] Next, after starting the first vacuum pump 23, the control unit 18 detects the pressure in the first chamber 22a by the pressure sensor 30, and determines whether the pressure in the first chamber 22a is higher than the necessary pressure stored in the storage device (step ST23). For example, if it is determined that the pressure in the first chamber 22a is equal to or lower than the necessary pressure, that is, the necessary negative pressure (NO in step ST23), it determines that the negative pressure is maintained by driving the first vacuum pump 23, and that the first vacuum pump 23 is normal. Thereafter, the control unit 18 performs, for example, the above-mentioned processes from step ST15 onwards.

[0051] For example, when the pressure in the first chamber 22a is higher than the required pressure (YES in step ST23), the control unit 18 determines that the required pressure cannot be reached by driving the first vacuum pump 23, and starts the second vacuum pump 24 (step ST24). After starting the first vacuum pump 23, the control unit 18 counts the number of times the second vacuum pump 24 has been started without the pressure in the first chamber 22a decreasing to a predetermined pressure (required pressure, required negative pressure), and stores the number in the storage device. The control unit 18 also determines whether the number of times the second vacuum pump 24 has been started has reached a threshold value n previously stored in the storage device (step ST25).

[0052] Here, the threshold value n is the number of times that the desired negative pressure is not achieved even when the first vacuum pump 23 is driven, and thus it can be determined that the function of the first vacuum pump 23 has deteriorated or stopped.

[0053] If the number of starts of the second vacuum pump 24 is smaller than the threshold value n (NO in step ST25), the control unit 18 determines that the first vacuum pump 23 is normal, and performs, for example, the process after step ST15. If the number of starts of the second vacuum pump 24 is the threshold value n (YES in step ST25), the control unit 18 determines that the first vacuum pump 23 is faulty (step ST26).

[0054] Note that, for example, when the control unit 18 determines that the first vacuum pump 23 has failed, the control unit 18 starts the second vacuum pump 24 instead of the first vacuum pump 23 during subsequent deceleration operations. The control unit 18 may store information that the first vacuum pump 23 has failed in a storage device, and may display information that the first vacuum pump 23 has failed on a display device of an instrument panel provided in the cabin of the vehicle 1. The control unit 18 may transmit information that the first vacuum pump 23 has failed to a driver's mobile terminal or a management terminal for maintenance by wireless communication.

[0055] In this way, if the desired negative pressure is not reached after the first vacuum pump 23 is started, the control unit 18 may start the second vacuum pump 24 to use the second vacuum pump 24 as an auxiliary pump, and may determine that the first vacuum pump 23 has failed when the second vacuum pump 24 is started repeatedly.

[0056] Furthermore, the present invention is not limited to these embodiments. For example, the brake system 17 may be configured not to have the second vacuum pump 24 for redundancy. Also, the second vacuum pump 24 for redundancy may be a mechanical vacuum pump instead of an electric vacuum pump. Also, the first vacuum pump 23 and the second vacuum pump 24 may have different performance. For example, when the first vacuum pump 23 is a mechanical vacuum pump and the second vacuum pump 24 is an electric vacuum pump, the first vacuum pump 23 may have a smaller output than the second vacuum pump 24 in order to reduce the influence of friction. Also, when the second vacuum pump 24 is configured to start when assisting the first vacuum pump 23 or when the first vacuum pump 23 fails, the second vacuum pump 24 may have a smaller output than the first vacuum pump 23. In addition, the brake system 17 may be configured to alternately drive the first vacuum pump 23 and the second vacuum pump 24, or may be configured to selectively start one of the first vacuum pump 23 and the second vacuum pump 24 depending on various factors such as the remaining amount of fuel in the internal combustion engine 12.

[0057] In the above example, the brake system 17 is a disc brake system, but the present invention is not limited to this and may be applied to a drum brake system, etc. In other words, various configurations can be applied to the brake system 17 for an HEV that generates a brake assist force by increasing the operating force of the brake pedal 21 by negative pressure.

[0058] The present invention is not limited to the above-mentioned embodiment, and can be modified in various ways without departing from the gist of the present invention. The embodiments may be combined as appropriate, and in that case, the combined effect can be obtained. Furthermore, the above-mentioned embodiment includes various inventions, and various inventions can be extracted by combinations selected from the multiple components disclosed. For example, if the problem can be solved and the effect can be obtained even if some components are deleted from all the components shown in the embodiment, the configuration from which the components are deleted can be extracted as an invention. The following provides a description equivalent to the invention described in the original claims of this application. [1] A brake system for a hybrid vehicle having an internal combustion engine and a motor as a power source, Brake pedal and A master cylinder that converts external force into hydraulic pressure; a mechanical vacuum pump driven by the internal combustion engine; a brake booster having a first chamber connected to the mechanical vacuum pump and a second chamber connected to the atmosphere, amplifying a force generated by operation of the brake pedal by a pressure difference between the first chamber and the second chamber and transmitting the force to the master cylinder; a pressure sensor that detects the pressure in the first chamber; a control unit that starts the internal combustion engine when the pressure detected by the pressure sensor is higher than a predetermined pressure in a case where the internal combustion engine is stopped at the start of a deceleration operation; A brake system comprising: [2] A detection sensor is provided to detect the operation of the brake pedal, The control unit determines the start of the deceleration operation when the detection sensor detects operation of the brake pedal. [3] The brake system described in [2], wherein the control unit determines that the deceleration operation is completed when the detection sensor detects that the brake pedal has been released. [4] The control unit of the brake system described in [1] stops the internal combustion engine when the deceleration operation is completed and when the internal combustion engine was stopped when the deceleration operation started. [5] The control unit stops the internal combustion engine when the deceleration operation is completed and the state of the vehicle in which the internal combustion engine is installed satisfies a stop condition for the internal combustion engine. [6] The control unit of the brake system described in [1] does not start the internal combustion engine when the pressure in the first chamber at the start of the deceleration operation is equal to or lower than the predetermined pressure, even if the internal combustion engine is stopped. [7] The brake system described in [1], further comprising an electric vacuum pump. [8] A vehicle, being a hybrid vehicle, comprising a brake system as described in any one of [1] to [7]. [Explanation of symbols]

[0059] 1...vehicle, 11...battery, 12...internal combustion engine, 13...first motor, 13...motor, 14...clutch, 15...second motor, 15...motor, 16...running part, 17...brake system, 18...control part, 21...brake pedal, 21b...brake pedal, 22...brake booster, 22a...first chamber, 22b...second chamber, 23...first vacuum pump (mechanical vacuum pump), 24...second vacuum pump, 25...master cylinder, 26...hydraulic circuit, 26a...piping part, 26b...hydraulic control part, 27...disc rotor, 28...brake pad, 29...brake caliper, 30...pressure sensor, 31...detection sensor.

Claims

1. A brake system for a hybrid vehicle having an internal combustion engine and a motor as a power source, Brake pedal and A master cylinder that converts external force into hydraulic pressure; a mechanical vacuum pump driven by the internal combustion engine; an electric vacuum pump driven by electricity; a brake booster having a first chamber connected to the mechanical vacuum pump and a second chamber connected to the atmosphere, amplifying a force generated by operation of the brake pedal by a pressure difference between the first chamber and the second chamber and transmitting the force to the master cylinder; a pressure sensor that detects the pressure in the first chamber; a control unit that starts the internal combustion engine and drives the mechanical vacuum pump when the pressure detected by the pressure sensor is higher than a predetermined pressure in a case where the internal combustion engine is stopped at the start of a deceleration operation; A brake system comprising:

2. A detection sensor for detecting the operation of the brake pedal is provided. The brake system according to claim 1 , wherein the control unit determines the start of the deceleration operation when the detection sensor detects the actuation of the brake pedal.

3. The brake system according to claim 2 , wherein the control unit determines that the deceleration operation is completed when the detection sensor detects that the brake pedal has been released.

4. The brake system according to claim 1 , wherein the control unit stops the internal combustion engine when the deceleration operation is completed and when the internal combustion engine was stopped at the start of the deceleration operation.

5. 2. The brake system according to claim 1, wherein the control unit stops the internal combustion engine when the deceleration operation is completed and when a state of the vehicle in which the internal combustion engine is mounted satisfies a stop condition for the internal combustion engine.

6. 2. The brake system according to claim 1, wherein the control unit does not start the internal combustion engine when the pressure in the first chamber at the start of the deceleration operation is equal to or lower than the predetermined pressure, even if the internal combustion engine is stopped.

7. A vehicle, which is a hybrid vehicle, comprising the brake system according to any one of claims 1 to 6.

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