Brake system and vehicle

Abstract

To provide a brake system and a vehicle that can use a mechanical vacuum pump, even in the case of a hybrid vehicle.SOLUTION: A brake system 17 for a hybrid vehicle which has an internal combustion engine 12 and a motor 15 as power sources comprises: a brake pedal 21; a master cylinder 25 which converts external force into hydraulic pressure; a mechanical vacuum pump 23 which is driven by the internal combustion engine 12; a brake booster 22 which has a first chamber 22a connected to the mechanical vacuum pump 23 and a second chamber 22b connected to the atmosphere, amplifies force generated by operation of the brake pedal 21b based on a pressure difference between the first chamber 22a and the second chamber 22b and transmits the amplified force to the master cylinder 25; a pressure sensor 30 which detects pressure in the first chamber 22a; and a control section 18 which starts the internal combustion engine 12 when the internal combustion engine 12 is stopped at the start of a deceleration operation and the pressure detected by the pressure sensor 30 is higher than a predetermined pressure.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] As a braking system used in a vehicle, in order to ensure necessary brake assist force, a technique is known in which the force generated by operating a brake pedal is amplified by a brake booster and transmitted to a master cylinder. Such a brake booster amplifies the force generated by operating 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, in an electric vehicle, since it does not have an internal combustion engine, an electric vacuum pump is adopted.

[0004] A hybrid vehicle has an internal combustion engine, but may stop the internal combustion engine during driving depending on the driving mode. Therefore, in a hybrid vehicle, since it may not be possible to drive a mechanical vacuum pump, an electric vacuum pump is adopted (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, an electric vacuum pump is more expensive than a mechanical vacuum pump. In particular, mounting two electric vacuum pumps to ensure redundancy increases the cost of the vehicle.

[0007] Therefore, an object of the present invention is to provide a braking system and a vehicle that can use a mechanical vacuum pump even in a hybrid vehicle.

Means for Solving the Problems

[0008] According to one aspect of the present invention, a braking system is a braking system for a hybrid vehicle having an internal combustion engine and a motor as power sources, and includes a brake pedal, a master cylinder that converts an external force into hydraulic pressure, a mechanical vacuum pump driven by the internal combustion engine, a first chamber connected to the mechanical vacuum pump, and a second chamber connected to the atmosphere. A brake booster that amplifies the force generated by the operation of the brake pedal by the pressure difference between the first chamber and the second chamber and transmits it to the master cylinder, a pressure sensor that detects the pressure in the first chamber, and a control unit that starts 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.

Advantages of the Invention

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

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

[0011] Hereinafter, a vehicle 1 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is an explanatory diagram schematically showing the configuration of the vehicle 1. FIG. 2 is an explanatory diagram schematically showing the configuration of a braking system 17 used in the vehicle 1. FIG. 3 is a flowchart showing an example of a deceleration operation using the braking system 17 of the vehicle 1. In each figure, the configuration is shown by appropriately enlarging, reducing, or omitting it.

[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 flat body vehicle, a wing vehicle, a vehicle with a hood, a unique vehicle, a vehicle-mounted vehicle, a tank truck, or the like. 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, or the like.

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

[0014] The battery 11 is a power source of the vehicle 1. The battery 11 is connected to the first motor 13 and the second motor 15 via an inverter, respectively. For example, as the battery 11, a lithium-ion battery, a solid lithium-ion battery, a graphene secondary battery, or the like is used. 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 a plurality of 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 operates to generate power (torque) that becomes driving force.

[0016] The internal combustion engine 12 is connected to the traveling unit 16 via a clutch 14, for example, and drives the traveling unit 16. Further, the internal combustion engine 12 is connected to the 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 pivotally supported by the motor case. For example, the first motor 13 is connected to the battery 11 via an inverter.

[0018] The 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. Further, 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 being supplied with electric power from the battery 11. Further, the first motor 13 may function as a starter that starts the internal combustion engine 12. That is, the first motor 13 can be a power source, a generator, or a starter of the vehicle 1 according to the operating state.

[0020] The inverter is provided between the battery 11 and the first motor 13 and between the battery 11 and the second motor 15, respectively, and has a power element, a capacitor, a control circuit, and the like. The inverter converts the DC voltage from the battery 11 into an AC voltage and supplies a three-phase current to the motors 13 and 15. Further, the inverter converts the AC voltage generated by the motor 13 into a DC voltage.

[0021] The clutch 14 is a dry friction clutch provided, for example, on the output side of the internal combustion engine 12. The clutch 14 is configured to be able to disconnect and connect the power transmission path from the internal combustion engine 12 to the traveling 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 pivotally supported by the motor case. The second motor 15 is connected to the traveling unit 16. Further, the second motor 15 is connected to the battery 11 via an inverter. The second motor 15 functions as a drive motor that rotates the shaft of the traveling unit 16 when power is supplied from the battery 11. That is, the second motor 15 serves as a power source of the vehicle 1.

[0023] The traveling unit 16 includes a drive shaft, an automatic transmission, a power transmission device, front wheels, rear wheels, and the like. For example, an automatic transmission is disconnectably connected to the output shaft of the internal combustion engine 12 via the clutch 14, and left and right front wheels and rear wheels, which are drive 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, and the like. The traveling unit 16 shifts the power transmitted from the internal combustion engine 12 via the clutch 14 at a predetermined gear ratio by the automatic transmission and transmits the power to the front wheels and rear wheels via the power transmission device.

[0024] The brake system 17 is a foot brake. The brake system 17 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 disk 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, increases the operating force by the pedal ratio and transmits the force to the 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 inside. The first chamber 22a is set to a negative pressure lower than the atmospheric pressure by the first vacuum pump 23 and / or the second vacuum pump 24, and the second chamber 22b is set to the atmospheric pressure. The first chamber 22a is on the master cylinder 25 side, and the second chamber 22b is arranged on the brake pedal 21 side. The brake booster 22 amplifies the force generated by the operation of the brake pedal 21 due to the pressure difference between the first chamber 22a and the second chamber 22b and transmits it 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. By driving the first vacuum pump 23, the first chamber 22a is set to a predetermined pressure (negative pressure) lower than the atmospheric pressure.

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

[0029] The master cylinder 25 has, for example, a piston inside and converts the external force applied to the piston into hydraulic pressure. The master cylinder 25 is connected to the hydraulic circuit 26. The master cylinder 25 increases the hydraulic pressure of the hydraulic circuit 26 when the piston is driven by the force generated by the 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 the plurality of brake calipers 29, and drives the plurality of brake calipers 29 by hydraulic pressure. 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 plurality of disk rotors 27 are provided, for example, on the front wheels and the rear wheels of the traveling section 16, respectively. When the brake pad 28 is pressed against the disk rotor 27, a frictional force is generated between the brake pad 28 and the disk rotor 27. The brake caliper 29 moves the brake pad 28 relative to the disk rotor 27. The brake caliper 29 drives in response to the hydraulic pressure of the hydraulic circuit 26 to move the brake pad 28 between a position where the brake pad 28 is retracted from the disk rotor 27 and a position where the brake pad 28 is pressed against the disk rotor 27.

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

[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). By executing various programs, the control unit 18 functions as a traveling control device, a deceleration operation control device, a vehicle state detection device, and the like. The control unit 18 may be provided in the vehicle 1, or part or all of it may be provided in another external terminal. For example, the control unit 18 may be a part of the ECU that controls the internal combustion engine 12. Also, the control unit 18 that serves as the deceleration operation control device may be configured to be included in a part of the brake system 17.

[0035] A variety of sensors such as a pressure sensor 30 and a detection sensor 31 are connected to the control unit 18, and output signals from these devices are input. Further, the control unit 18 is 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 the accelerator operation information of the vehicle 1 and various detection values. That is, the control unit 18 transmits control signals to each part to perform various control processes necessary for driving, such as output control of the motors 13 and 15, control of the power generation amount of 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 torque and rotational speed generated by the internal combustion engine 12 by controlling the fuel injection amount of the internal combustion engine 12. Further, the control unit 18 switches the connection state of the power source and switches the driving mode by controlling the engagement and disengagement of the clutch 14. Also, the control unit 18 controls the outputs of the motors 13 and 15.

[0037] For example, the control unit 18 drives the vehicle 1 in a plurality of different driving modes by appropriately combining a plurality of power sources of the first motor 13, the second motor 15, and the internal combustion engine 12 according to the driving state. For example, in addition to the first driving mode in which the internal combustion engine 12 is stopped and the second motor 15 is used as the power source, a driving mode in which both the first motor 13 and the second motor 15 are used as the power source, a driving mode in which either or both of the first motor 13 and the second motor 15 and the internal combustion engine 12 are used as the power source, a driving mode in which only the internal combustion engine 12 is used as the power source, etc., a plurality of different driving modes are switched according to the driving state to control the vehicle 1.

[0038] Further, 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 control unit 18 detects the operation of the brake pedal 21 by the detection sensor 31, the control unit 18 drives and controls 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 for driving the brake system 17.

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

[0040] Hereinafter, an example of the deceleration operation of the brake system 17 according to the embodiment will be described with reference to the flowchart 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. The control unit 18 detects the operation of the brake pedal 21 based on the output signal from the detection sensor 31 (step ST11), and determines the start of the deceleration operation. Next, the control unit 18 determines whether or not 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), the control unit 18 determines whether or not the pressure (negative pressure) in the first chamber 22a detected by the pressure sensor 30 is higher than the pressure (required negative pressure) required for driving the brake system 17 (step ST13). Here, the pressure (required negative pressure) required for driving the brake system 17 is the pressure (negative pressure) in 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 required pressure for driving the brake system 17 is preset and stored in the storage 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 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 when the piston of the master cylinder 25 is operated with a predetermined force, 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 disk rotor 27, and the deceleration operation of the vehicle 1 is performed.

[0042] During the deceleration operation, the driver operates the brake pedal 21 as braking until the vehicle 1 reaches the desired vehicle speed or stops. Therefore, the control unit 18 monitors based on the output signal of the detection sensor 31 for the release of the operation of the brake pedal 21 by the driver, and determines whether the 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 as the braking end determination based on the output signal from the detection sensor 31. 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). If 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 addition, in step ST12, when the internal combustion engine 12 is running (NO in step ST12), since the first vacuum pump 23 is running, 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 the processes after step ST15. Further, in step ST13, when the pressure detected by the pressure sensor 30 is equal to or lower than the required pressure, since the pressure in the first chamber 22a is the desired negative pressure, the control unit 18 does not start the internal combustion engine 12 (first vacuum pump), and performs the processes after step ST15.

[0044] Also, for example, the control unit 18 determines whether the internal combustion engine 12 has stopped at the start of the completed deceleration operation, that is, when the brake pedal 21 detected in ST11 is operated (step ST17). When the internal combustion engine 12 has stopped when the brake pedal 21 is operated (YES in step ST17), it is determined whether the current state of the vehicle 1 satisfies the stop condition of the internal combustion engine 12 (step ST18). When 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). When the internal combustion engine 12 is running when the brake pedal 21 is operated (NO in step ST17) or when the stop condition of the internal combustion engine 12 is not satisfied (NO in step ST18), the driving of the internal combustion engine 12 is continued. As described above, during the 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 stops. When the pressure difference is not the desired one, the control unit 18 starts the internal combustion engine 12 to drive the first vacuum pump 23 and make the first chamber 22a have a negative pressure.

[0045] According to the vehicle 1 having the braking system 17 configured as described above, even in a 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 negative pressure in the brake booster 22 that generates the necessary brake assist force. By using a mechanical vacuum pump that is more cost - advantageous than an electric vacuum pump for the braking system 17, the manufacturing cost of the vehicle 1 can be reduced. In particular, from the perspective of ensuring redundancy, it is assumed that two vacuum pumps are used for the vehicle 1. The vehicle 1 of the embodiment uses the first vacuum pump 23 as a mechanical vacuum pump and the second vacuum pump 24 as an electric vacuum pump, so that the cost can be reduced compared to a configuration in which two electric vacuum pumps are mounted. In addition, since the vehicle 1 can drive the second vacuum pump 24 with the power from the battery 11 when there is a problem with the first vacuum pump 23 or the internal combustion engine 12, it is possible to surely generate the negative pressure that generates the necessary brake assist force in the brake booster 22 during the deceleration operation of the braking system 17. Therefore, the braking system 17 can ensure safety and redundancy in addition to cost reduction.

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

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

[0048] Another example of an embodiment of the deceleration operation using the brake system 17 of such a vehicle 1 will be described with reference to the flowchart shown in FIG. 4.

[0049] First, when the control unit 18 determines that the brake pedal 21 has been actuated based on the 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 in steps ST21 and ST22 are the same as the operations in steps ST11 to ST14 described above, for example.

[0050] Subsequently, 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 required pressure stored in the storage device (step ST23). For example, when it is determined that the pressure in the first chamber 22a is equal to or lower than the required pressure, that is, a required negative pressure (NO in step ST23), it is determined that the negative pressure is maintained by driving the first vacuum pump 23 and the first vacuum pump 23 is normal. Thereafter, the control unit 18 performs the processes after step ST15 described above, for example.

[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 is started when the pressure in the first chamber 22a does not decrease to a predetermined pressure (required pressure, required negative pressure), and stores it in the storage device. Further, the control unit 18 determines whether the number of times the second vacuum pump 24 is started has reached a threshold value n stored in advance in the storage device (step ST25).

[0052] Here, the threshold value n is the number of times it can be determined that the function of the first vacuum pump 23 has deteriorated or stopped due to the repetition of the situation where the desired negative pressure cannot be achieved even by driving the first vacuum pump 23.

[0053] When the number of times the second vacuum pump 24 is started is less 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 processing after step ST15. When the number of times the second vacuum pump 24 is started 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 when the control unit 18 determines that the first vacuum pump 23 is faulty, for example, in subsequent deceleration operations, instead of the first vacuum pump 23, the second vacuum pump 24 is started. Further, the control unit 18 may store information that the first vacuum pump 23 is faulty in the storage device, and may also display information that the first vacuum pump 23 is faulty on a display device of an instrument panel provided in the cabin of the vehicle 1. Further, the control unit 18 may transmit information that the first vacuum pump 23 is faulty to the driver's mobile terminal or a maintenance management terminal by wireless communication.

[0055] Thus, when the first vacuum pump 23 fails to reach a desired negative pressure after starting, the control unit 18 starts the second vacuum pump 24 to assist the second vacuum pump 24, and may determine a failure of the first vacuum pump 23 each time the second vacuum pump 24 is repeatedly started.

[0056] Furthermore, the present invention is not limited to these embodiments. For example, the brake system 17 may be configured without 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 performances. 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 started to assist 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. Also, the brake system 17 may be configured to drive the first vacuum pump 23 and the second vacuum pump 24 alternately, or may be configured to selectively start one of the first vacuum pump 23 and the second vacuum pump 24 according to various factors such as the remaining amount of fuel in the internal combustion engine 12.

[0057] Also, in the above-described example, the brake system 17 has been described as an example of a disc brake system, but is not limited thereto, and may be applied to a drum brake system or the like. That is, any configuration can be applied as long as it is a brake system 17 for an HEV that increases the operating force of the brake pedal 21 by negative pressure to generate a brake assist force.

[0058] Note that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof at the implementation stage. Also, the respective embodiments may be implemented in appropriate combination, and in that case, the combined effects can be obtained. Furthermore, the above embodiments include various inventions, and various inventions can be extracted by combinations selected from the plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiments, if the problem can be solved and the effects can be obtained, the configuration from which these constituent elements are deleted can be extracted as an invention.

Explanation of Reference Numerals

[0059] 1... vehicle, 11... battery, 12... internal combustion engine, 13... first motor, 13... motor, 14... clutch, 15... second motor, 15... motor, 16... running section, 17... brake system, 18... control unit, 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 section, 26b... hydraulic control unit, 27... disk rotor, 28... brake pad, 29... brake caliper, 30... pressure sensor, 31... detection sensor.

Claims

1. A braking system for a hybrid vehicle having an internal combustion engine and a motor as power sources, comprising: a brake pedal; a master cylinder that converts an 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, and amplifying a force generated by an operation of the brake pedal by a pressure difference between the first chamber and the second chamber and transmitting the amplified 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 braking system comprising the above components.

2. The braking system according to claim 1, further comprising a detection sensor that detects an operation of the brake pedal, wherein the control unit determines the start of the deceleration operation when the detection sensor detects an operation of the brake pedal.

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

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

5. The braking system according to claim 1, wherein the control unit stops the internal combustion engine when the deceleration operation is completed and the state of the vehicle equipped with the internal combustion engine satisfies the stop condition of the internal combustion engine.

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

7. The braking system according to claim 1, further comprising an electric vacuum pump.

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

Images