braking system

Abstract

Braking system with: a hydraulic brake device for generating a friction braking force comprising a pedal (16), at least one brake caliper (21a - 21d) a main pressure generating device (200) with a main cylinder (212) and a piston (251) which pressurizes the main cylinder (212), a wheel pressure generating device (300) for generating a hydraulic pressure in the at least one brake caliper (21a - 21d); and a regenerative braking device (18) and a brake control device (100) for calculating a braking force distribution between friction brakes and regenerative braking, wherein the braking system is configured to adjust a total braking force (Ft) based on a pedal reaction force and a displacement amount of the piston (251) that pressurizes the master cylinder (212), or adjust the total braking force (Ft) based on the pedal reaction force and the generated hydraulic pressure in the at least one brake caliper (21a - 21d) to keep the total braking force (Ft) at a constant level when transitioning from regenerative braking to friction braking in response to a reduction in vehicle speed.

Description

Technical area

[0001] The present invention relates to a braking system that controls deceleration of a vehicle by controlling an actuator that boosts a master cylinder. Background of the technology

[0002] A known example of a braking system that performs cooperative control of a hydraulic brake and a regenerative brake includes, as described in Patent Document 1, a BBW (Brake-By-Wire) in which a brake pedal is electrically connected to an actuator.

[0003] Such a braking system includes, for example, a control device for controlling a friction brake actuator, which generates braking force by pressurizing hydraulic oil, and a regenerative brake actuator, which generates braking force by regeneration. Based on a brake pedal stroke amount, vehicle speed, or the like, the control device determines the distribution of braking forces to be generated by the friction brake actuator and the regenerative brake actuator and outputs a control signal to each actuator.

[0004] Furthermore, Patent Document 2 describes an electrically operated brake boosting device used in a brake mechanism of an automobile, which uses an electrically operated actuator as a boosting device.

[0005] Patent Document 3 discloses a brake device including a master cylinder in which braking pressure is generated by the forward movement of a primary inner piston, and a pump disposed between the master cylinder and the wheel cylinders. The pressure generated by the pump is supplied to a control pressure chamber to act on a stage of a primary outer piston. The primary outer piston moves relative to the primary inner piston in such a way that the force generated by the pressure in the master cylinder, the force generated by the pump pressure, the spring force of a control spring, and the frictional force of the primary outer piston are balanced.

[0006] Patent Document 4 discloses a method for controlling a braking system of electric-powered vehicles, in which regenerative braking is performed via the vehicle's at least one drive motor and braking is performed via a friction brake. The driver's braking request is detected by a control unit, and in a first braking request range, the braking torque is applied primarily by the regenerative braking. The friction brake is controlled such that the pressure generated by the driver's brake pedal actuation in this first range does not produce any significant braking effect on the vehicle's drive wheels. Patent Document 1 JP Patent Laid-Open No. 2005-329740 A (2005) Patent Document 2 JP Patent Laid-Open No. 2007-191133 A (2007) Patent document 3 US 2002 / 0 014 379 A1 Patent document 4 DE 196 04 134 A1 Disclosure of the invention Problems to be solved by the invention

[0007] The electrical connection between the brake pedal and the actuator in the brake system described in Patent Document 1 prevents unnecessary reaction force or the like from being output to the brake pedal. However, the brake system according to Patent Document 1 has a higher manufacturing cost than a conventional brake system using a vacuum booster device and is of low reliability because the brake pedal and a hydraulic pressure generating mechanism are electrically connected.

[0008] The brake system described in Patent Document 2 discloses a brake pedal and a friction brake actuator that are mechanically connected to each other, and incorporates a conventional brake system structure using a vacuum booster device. Therefore, the brake system has lower manufacturing costs and higher reliability than the brake system according to Patent Document 1. However, since the brake pedal and the friction brake actuator in the brake system according to Patent Document 2 are mechanically connected to each other, the brake system is susceptible to changes in the hydraulic pressure of the friction brake actuator during regenerative cooperative control, and the reaction force of the brake pedal is prone to fluctuations. Given that many drivers operate a brake pedal using a pedal depression force, a fluctuation in the pedal reaction force is accompanied by a fluctuation in the pedal stroke amount.Since in Patent Document 2, an output of the friction brake actuator is determined based on a pedal depression force and an input plunger displacement amount, a fluctuation in deceleration occurs. Since such fluctuations in pedal reaction force and deceleration are completely unrelated to a driver's intentions, the respective fluctuations must be either reduced or suppressed.

[0009] The object of the present invention is to provide a brake control technique that enables the suppression of fluctuations in deceleration that are not intended by a driver. Means to solve the problems

[0010] The above-described object is achieved by the invention according to the subject matter of independent claim 1. Further preferred embodiments of the invention are described in the dependent claims. Advantage of the invention

[0011] According to the present invention, since a braking force fluctuation and a deceleration fluctuation can be suppressed during a transition period from a regenerative brake to a hydraulic brake, braking operations of vehicles such as a hybrid vehicle incorporating a hydraulic brake and a regenerative brake, an electric car, and the like can be performed stably and easily. Short description of the drawings Fig. 1 is an explanatory diagram illustrating a configuration of a vehicle to which the present invention has been applied. Fig. 2 is an explanatory diagram illustrating a functional configuration of a brake system according to the present invention. Fig. 3 is an explanatory diagram illustrating a configuration of a main pressure generating device and a wheel pressure generating device according to the present invention. Fig. 4 is a flowchart illustrating basic operations of the braking system according to the present invention. Fig. 5 is a graph illustrating a maximum regenerative braking force output from a regenerative braking device based on a vehicle speed and a gear position in the braking system according to the present invention. Fig. 6 is a graph showing a limit of a regenerative braking force output from the regenerative braking device based on a vehicle speed in the braking system according to the present invention. Fig. 7 is a graph illustrating a frictional braking force output from the master pressure generating device based on an input plunger displacement amount in the braking system according to the present invention. Fig. 8 is a graph showing an ideal output during the execution of the Fig. 4 when a friction braking force and a regenerative braking device are approximately equal to each other in the braking system according to the present invention. Fig. 9 is a graph illustrating an actual output when a main pressure generating device 200 and a regenerative braking device 18 are connected according to the Fig. 4 in a case where a friction braking force and a regenerative braking device are approximately equal to each other in the braking system according to the present invention. Fig. 10 is a graph illustrating an actual output when a wheel pressure generating device 300 and the regenerative braking device 18 are operated according to the Fig. 4 in a case where a friction braking force and a regenerative braking device are approximately equal to each other in the braking system according to the present invention. Fig. 11 is a graph illustrating characteristics of a total braking force output from the braking system based on a pedal reaction force and a piston displacement amount used in the braking system according to the present invention. Fig. 12 is a flowchart illustrating operations of the braking system according to the present invention. Fig. 13 is a graph illustrating an actual output when the main pressure generating device 200 and the regenerative braking device 18 are operated according to the Fig. 11 illustrated total braking force characteristics and the Fig. 12 in a case where a friction braking force and a regenerative braking force are approximately equal to each other in the braking system according to the present invention. Fig. 14 is a graph illustrating characteristics of a total braking force output from the braking system based on a pedal reaction force and a hydraulic pressure increased / decreased by the wheel pressure generating device 300 used in the braking system according to the present invention. Fig. 15 is a graph illustrating an actual output when the wheel pressure generating device 300 and the regenerative braking device 18 are operated according to the Fig. 14 illustrated total braking force characteristics and the Fig. 12 in a case where the friction braking force and a regenerative braking device are approximately equal to each other in the braking system according to the present invention. Description of symbols 10 vehicles 15a, 15b, 15c, 15d Wheel 16 Brake pedal 17 electrical storage device 18 regenerative braking device 20a, 20b, 20c, 20d disc rotor 21a, 21b, 21c, 21d brake caliper 31 Brake sensor 100 brake control device 110 CPU 111 Brake force calculation device 112 Communication control device 200 Main pressure generating device 201 Main pressure control 210 Main pressure generating mechanism 300 wheel pressure generating device 301 Wheel pressure control 310 Wheel pressure generating mechanism Best mode for carrying out the invention

[0012] .Hereinafter, an embodiment according to the present invention will be described with reference to the Fig. 1 to 15 described.

[0013] Although the present embodiment is an example in which the present invention is applied to an FF (front-engine, front-wheel drive) vehicle, the example is not limitative, and the present invention can also be applied to vehicles such as a 4WD (four-wheel drive) and an FR (front-engine, rear-wheel drive) vehicle.

[0014] As in Fig. 1, a vehicle 10 according to a first embodiment includes an engine 11, a torque converter 12, a transmission 13, drive shafts 14 and 19, wheels 15a to 15d, a brake pedal 16, disc rotors 20a to 20d, brake calipers 21a to 21d, a brake control device 100, a master pressure generating device 200 that generates hydraulic pressure for actuating the brake calipers 21a to 21d, a wheel pressure generating device 300 that similarly generates hydraulic pressure for actuating the brake calipers 21a to 21d, an electric storage device 17, and a regenerative braking device 18 that applies braking force to the rear wheels 15c and 15d.

[0015] The engine 11 is an internal combustion engine that generates power by causing an explosion of an air / fuel mixture in a combustion chamber. The movement of a piston caused by the explosion is converted into rotational movement of a crankshaft via a connecting rod. The crankshaft transmits power to the front wheels 15a and 15b via the torque converter 12, the transmission 13, and the drive shaft 14.

[0016] The torque converter 12 is provided between the engine 11 and the transmission 13. By using a working fluid such as oil, the torque converter 12 functions as a clutch that intermittently transmits a rotational torque output from the engine 11 to the transmission and also amplifies the rotational torque before transmitting it to the transmission 13.

[0017] The transmission 13 is provided between the torque converter 12 and the drive shaft 14 and has a plurality of gears corresponding to respective gear stages, for example, five forward stages (first to fifth gear) and one reverse stage.

[0018] The drive shaft 14 is a rotary shaft that couples the transmission 13 to the front wheels 15a and 15b and transmits a rotational driving force of the engine 11 to the front wheels 15a and 15b.

[0019] The brake pedal 16 is to be depressed by a driver when the vehicle 10 is decelerated. The driver's depression force is transmitted via the brake pedal 16 to the main pressure generating device 200. Hydraulic pressure generated at the main pressure generating device 200 is transmitted to the brake calipers 21a to 21d via the wheel pressure generating device 300 and actuates the brake calipers 21a to 21d. The wheel pressure generating device 300 either transmits the hydraulic pressure generated at the main pressure generating device 200 to the brake calipers 21a to 21d without modification or transmits the hydraulic pressure to the brake calipers 21a to 21d after further pressurization.

[0020] The brake consists of disc rotors 20a to 20d and brake calipers 21a to 21d. The respective disc rotors 20a to 20d are attached to the respective wheels 15a to 15d and rotate integrally with the wheels 15a to 15d. Although not shown, each of the brake calipers 21a to 21d consists of a cylinder, a piston, a pad, and the like. The pistons in the cylinders are moved by hydraulic oil from the main pressure generating device 200 and the wheel pressure generating device 300, and press pads coupled to the pistons against the disc rotors 20a to 20d. When the pads press against the disc rotors 20a to 20d, a frictional force is generated between the pads and the disc rotors 20a to 20d. The friction force acts as a braking force on the respective wheels 15a to 15d and further generates a braking force between the respective wheels 15a to 15d and the road surface.

[0021] The regenerative braking device 18 is connected to the drive shafts 19 extending from the left and right rear wheels 15c and 15d, respectively, and generates electricity during braking according to rotation of the drive shafts 19 and supplies the generated electricity to the electric storage device 17. At the same time, a rotational resistance provides braking force to the left and right rear wheels 15c and 15d during electricity generation.

[0022] As in Fig. As shown in Figure 2, the electrical storage device 17 is provided with a voltmeter 36 for detecting a voltage of the electrical storage device. The voltmeter 36 is connected to an interface 101 of the brake control device 100 in the same manner as other sensors.

[0023] In the present embodiment, among the above-described components of the vehicle, a braking system is constituted by the brake pedal 16, the disc rotors 20a to 20d, the brake calipers 21a to 21d, the master pressure generating device 200, the wheel pressure generating device 300, the brake control device 100, a brake sensor to be described later, and the regenerative braking device 18.

[0024] As in Fig. 2, the brake control device 100 is a computer including a CPU that performs various arithmetic processing, the interface 101 that receives / sends signals from the outside, a ROM 102 that stores various programs to be executed by the CPU, various data, and the like in advance, and a RAM 103 to be used as a work space by the CPU.

[0025] Functionally, the CPU includes a braking force calculation unit 111 that calculates a target deceleration based on information from the various sensors, a communication control unit 112 that determines a braking force distribution between friction braking and regenerative braking based on the target deceleration calculated by the braking force calculation unit 111 and information from the various sensors, and a communication control unit that controls external communication. The respective functional units 111 and 112 are both activated when the CPU 110 executes programs stored in the ROM 102.

[0026] The various sensors include the brake sensor 31, a vehicle speed sensor 32 that detects the speed of the vehicle 10, a longitudinal acceleration sensor 33 that detects an acceleration generated in the longitudinal direction of the vehicle 10, a wheel speed sensor 34 that detects the speeds of the respective wheels 15a to 15d, and a gear position sensor 35 that detects a gear position of the transmission 13. The various sensors are all connected to the interface 101 of the brake control device 100.

[0027] The brake sensor 31, which detects a requested braking force of the driver, is, as shown in Fig. 3 illustrates a stroke sensor that detects the displacement amount of an input plunger 214 coupled to the brake pedal 16. Multiple stroke sensors can be combined to form the brake sensor 31. Accordingly, fail-safe operation can be ensured; even if a signal from one sensor stops, a driver's braking request can be detected and recognized by the remaining sensors. Furthermore, the brake sensor 31 can also be a depression force sensor that detects a depression force applied to the brake pedal 16, or a combination of the depression force sensor and a stroke sensor.

[0028] The main pressure generating device 200 includes a main pressure controller 201 that receives a drive control signal from the brake control device 100, and a main pressure generating mechanism 210 controlled by the main pressure controller 201.

[0029] In addition, the wheel pressure generating device 300 includes a wheel pressure controller 301 that receives a drive control signal from the brake control device 100, and a wheel pressure generating mechanism 310 controlled by the wheel pressure controller 301.

[0030] As in Fig. 3, the master pressure generating mechanism 210 includes a return spring storage cylinder 211, a master cylinder 212 internally filled with hydraulic oil, a reservoir tank 213 that stores hydraulic oil to be supplied to the interior of the master cylinder 212, the input rod 214 as first pressurizing means, one end of which is coupled to the brake pedal 16 and the other end of which faces the interior of the master cylinder 212, and a motor pressurizing mechanism 220 as second pressurizing means.

[0031] The interior of the reservoir tank 213 is divided by a partition wall, not shown, to provide the reservoir tank 213 with two fluid chambers. The respective fluid chambers are connected to respective fluid chambers 215 and 216, to be described later, in the master cylinder 212.

[0032] The motor pressurizing mechanism 220 includes a pressurizing motor 221 driven by a drive signal from the main pressure controller 201, a deceleration mechanism 230 that amplifies a rotational torque of the pressurizing motor 221, a rotation-to-translation conversion mechanism 240 that converts a rotational force into a translational force, a movable member 250 that moves linearly while in contact with the rotation-to-translation conversion mechanism 240, a primary piston 251 that is pushed by the movable member 250 and forms a primary fluid chamber 215 in the main cylinder 212, a secondary piston 252 that forms a secondary fluid chamber 216 in the main cylinder 212, and a return spring 255 that is arranged in the return spring storage cylinder 211 and which attempts toto return the movable member 250 pushed by the rotation-to-translation conversion mechanism 240 to its original position.

[0033] The deceleration mechanism 230 precisely amplifies a rotational torque of the pressurizing motor 221 through a deceleration ratio thereof. Suitable deceleration methods include gear deceleration and pulley deceleration. The present embodiment uses a pulley deceleration system including a drive-side pulley 231 attached to a rotational shaft of the pressurizing motor 221, a driven-side pulley 232, and a belt 233 bridging the drive-side pulley 231 and the driven-side pulley 232. If the pressurizing motor 221 has a sufficiently large rotational torque and does not require torque amplification by deceleration, the deceleration mechanism 230 can be omitted and the pressurizing motor 221 can be directly coupled to the rotation-to-translation conversion mechanism 240.Accordingly, various problems related to reliability, smoothness, assemblability, and the like, which arise due to the insertion of the deceleration mechanism 230, can be avoided.

[0034] The rotation-to-translation conversion mechanism 240 converts the rotational power of the pressurizing motor 221 into translational power and pushes the primary piston 251 via the movable member 250. Suitable conversion mechanisms include a rack and pinion and a ball screw. The present embodiment uses a ball screw system including a ball screw nut 241 rotated by the output side plate 232 and a ball screw shaft 242 whose translational movement is caused by the rotational movement of the ball screw nut 241.

[0035] One end of the input rod 214 is coupled to the brake pedal 16, and the other end faces the interior of the primary fluid chamber 215 in the master cylinder 212. When the brake pedal 16 is depressed and the input rod 214 performs a rectilinear movement, the hydraulic pressure in the primary fluid chamber 215 increases, and the secondary piston 252 is pushed, causing the hydraulic pressure in the secondary fluid chamber 216 to also increase. As a result, hydraulic oil is supplied to a first main pipe 261 connecting the primary fluid chamber 215 and the wheel pressure generating mechanism 310, and a second main pipe 262 connecting the secondary fluid chamber 216 and the wheel pressure generating mechanism 310. The hydraulic oil is then supplied to the respective brake calipers 21a to 21d via the wheel pressure generating device 300.Thereby, a predetermined braking force can be ensured even if the motor pressurizing mechanism 220 is unable to operate normally due to a failure or the like.

[0036] Furthermore, as described above, when the brake pedal 16 is depressed, the hydraulic pressure in the primary fluid chamber 215 increases, and the hydraulic pressure acts as a brake pedal reaction force. Therefore, by adopting the structure of the present embodiment, a mechanism such as a spindle for generating a brake pedal reaction force becomes unnecessary. Accordingly, a contribution can be made to reducing the size and weight of the brake system.

[0037] The pressurizing motor 221 is driven by a drive signal from the main pressure controller 201 and generates a desired torque. While a DC motor, a brushless DC motor, an AC motor, or the like is suitable as the pressurizing motor 221, a brushless DC motor is most preferable in terms of controllability, smoothness, and durability. The pressurizing motor 221 includes a position sensor and is configured such that a position signal from the position sensor is input to the main pressure controller 201. Accordingly, the main pressure controller 201 is capable of calculating a rotation angle of the pressurizing motor 221 based on the position signal from the position sensor and further calculating a translation amount of the rotation-to-translation conversion mechanism 240, or in other words, a displacement amount of the primary piston 251.

[0038] The rotational torque of the pressurizing motor 221 is amplified by the deceleration mechanism 230 and rotates the ball screw nut 241 of the rotation-to-translation conversion mechanism 240. The rotation of the ball screw nut 241 causes a translational movement of the ball screw shaft 242, which in turn presses against the primary piston 251 via the movable member 250.

[0039] In addition, one end of the return spring 255 is in contact with the movable member 250 on a side opposite to the ball screw shaft 242, and the other end of the return spring 255 is in contact with an inner wall of the return spring storage cylinder 211. Therefore, a force in the opposite direction of the thrust force of the ball screw shaft 242 acts on the ball screw shaft 242 via the movable member 250.Accordingly, in a state where the pressurizing motor 221 is driven, the primary piston 251 is pushed, and a master pressure (a pressure within the master cylinder 212) is pressurized. Even if the pressurizing motor 221 stops due to a failure or the like, and a return control applied to the ball screw shaft 242 is deactivated, the ball screw shaft 242 is returned to its original position by the urging force of the return spring 255, and the master cylinder pressure can be reduced to approximately zero. As a result, dragging of the braking force due to a failure of the pressurizing motor 221 can be avoided.

[0040] When the primary piston 251 is pushed, the hydraulic pressure in the primary fluid chamber 215 increases, which in turn pushes the secondary piston 252 and causes the hydraulic pressure in the secondary fluid chamber 216 to also increase. As a result, hydraulic oil is supplied to the first main pipe 261 connecting the primary fluid chamber 215 and the wheel pressure generating mechanism 310, and to the second main pipe 262 connecting the secondary fluid chamber 216 and the wheel pressure generating mechanism 310. The hydraulic oil is then supplied to the respective brake calipers 21a to 21d via the wheel pressure generating device 300. In other words, hydraulic oil is supplied to the respective brake calipers 21a to 21d via the main pipes 261 and 262 and the wheel pressure generating device 300 even when the input rod 214 is pushed by the driver's pushing force or when the primary piston 251 is pushed by the drive of the pressurizing motor 221.

[0041] The present embodiment adopts a tandem system provided with the primary piston 251 and the secondary piston 252. The reason for this is to ensure a certain master pressure level even if oil leaks from the master cylinder 212. For example, if an oil leak occurs in the primary fluid chamber 215, the primary piston 251 pushes due to the Fig. 3, the secondary piston 252 is directly actuated to ensure that the hydraulic pressure in the secondary fluid chamber 216 increases.

[0042] In the present embodiment, by displacing the primary piston 251 according to a displacement amount of the input rod 214 resulting from a driver's braking operation, the pressurization of the hydraulic pressure in the primary fluid chamber 215 due to the input rod 214 can be further amplified. The boost ratio (hereinafter referred to as "boost ratio") is determined by a ratio of a displacement amount of the input rod 214 to that of the primary piston 251, a ratio of a cross-sectional area of ​​the input rod 214 (hereinafter referred to as "AIR") to that of the primary piston 251 (hereinafter referred to as "APP"), or the like. Specifically, when the primary piston 251 is displaced by the same amount as the displacement amount of the input rod 214, the boost ratio is uniquely determined as (AIR + APP) / AIR.More specifically, by adjusting AIR and APP based on a required boost ratio and controlling the primary piston 60 so that its displacement amount is equal to the displacement amount of the input plunger 214, a constant boost ratio can always be obtained. A displacement amount of the input plunger 214 is detected by the brake sensor 31, and a displacement amount of the primary piston 251 is calculated by the main pressure controller 201 based on a signal from a position sensor of the pressurizing motor 221.

[0043] The wheel pressure generating mechanism 310 includes outlet passage valves 310a and 310b that control the supply of hydraulic oil from the main pressure generating mechanism 210 to the respective brake calipers 21a to 21d, inlet passage valves 311a and 311b that control the supply of hydraulic oil from the main pressure generating mechanism 210 to pumps to be described later, inlet valves 312a to 312d that control the supply of hydraulic oil that has flowed through the outlet passage valves 310a and 310b and hydraulic oil from the pumps to the respective brake calipers 21a to 21d, outlet valves 313a to 313d that control a pressure reduction of the hydraulic pressure to the brake calipers 21a to 21d, pumps 314a and 314b, which push up hydraulic oil supplied from the main pressure generating mechanism 210 via the inlet passage valves 311a and 311b, a pump motor 315 which drives the pumps 314a and 314b, a main pressure sensor 316 which detects a main pressure,and storage container 317a and 317b.,

[0044] A hydraulic pressure control device for anti-lock brake control, a hydraulic pressure control device for vehicle behavior stabilization control, a hydraulic pressure control device for brake-by-wire, or the like may be adopted as the wheel pressure generating mechanism 310 described above.

[0045] The wheel pressure generating mechanism 310 is constituted by two systems, namely a first braking system that controls the supply of hydraulic pressure to the VL (front left) brake caliper 21a and the HR (rear right) brake caliper 21d, and a second braking system that controls the supply of hydraulic pressure to the VR (front right) brake caliper 21b and the HL (rear left) brake caliper 21c.

[0046] The first braking system consists of the exhaust passage valve 310a, the inlet passage valve 311a, the inlet valves 312a and 312d, the exhaust valves 313a and 313d, and the reservoir 317a. In addition, the second braking system consists of the exhaust passage valve 310b, the inlet passage valve 311b, the inlet valves 312b and 312c, the exhaust valves 313b and 313c, and the reservoir 317b. The first main pipe 261 connected to the primary fluid chamber 215 of the main pressure generating mechanism 210 is connected to the outlet passage valve 310a and the inlet passage valve 311a of the first braking system, and the second main pipe 262 connected to the secondary fluid chamber 216 of the main pressure generating mechanism 210 is connected to the outlet passage valve 310b and the inlet passage valve 311b of the second braking system.

[0047] By providing two braking systems in this way, even if one of the braking systems fails, braking force of two wheels at diagonally opposite corners can be ensured by the other normally operating braking system and the behavior of the vehicle can be kept stable.

[0048] The exhaust passage valves 310a and 310b, the intake passage valves 311a and 311b, the intake valves 312a to 312d, and the exhaust valves 313a to 313d are all electromagnetic valves that include an electromagnet and are opened and closed by applying a current to the electromagnet. The opening / closing of each valve is controlled by the wheel pressure controller 301. The exhaust port valves 310a and 310b and the intake valves 312a to 312d are valves that enter an open state when flows to the valves are interrupted and enter a closed state when the flows flow through the valves, whereas the intake port valves 311a and 311b and the exhaust valves 313a to 313d are valves that enter a closed state when flows to the valves are interrupted and enter an open state when the flows flow through the valves.

[0049] While a plunger pump, a trochoid pump, a gear pump, or the like is suitable for pumps 314a and 314b, a gear pump is most desirable in terms of quietness. The pump motor 315 is actuated by a drive signal from the wheel pressure controller 301 and drives the pumps 314a and 314b, which are coupled to the pump motor 315. While a DC motor, a brushless DC motor, an AC motor, or the like is suitable for the pump motor 315, a brushless DC motor is most preferred in terms of controllability, quietness, and durability.

[0050] The master pressure sensor 316 is connected to the second master pipe 262, which is connected to the secondary fluid chamber 216 of the master pressure generating mechanism 210. A master pressure detected by the master pressure sensor 316 is sent to the wheel pressure controller 301. Furthermore, the number of master pressure sensors 316 and their installation positions should be appropriately determined from the perspective of controllability, fail-safe, and the like.

[0051] Next, operations of the wheel pressure generating mechanism 310 will be described. Only operations of the first braking system will be described below. Since operations of the second braking system are the same as those of the first braking system, their description will be omitted.

[0052] First, a case will be described where hydraulic pressure boosted by the main pressure generating mechanism 210 is supplied as is to the front brake caliper 21a and the rear brake caliper 21d without further boosting. In this case, the inlet port valve 311a and the outlet valves 313a and 313d are in a closed state, and the outlet port valve 310a and the inlet valves 312a and 312d are in an open state.

[0053] Hydraulic oil from the main pressure generating mechanism 210 via the first main pipe 261 is sent to the brake calipers 21a and 21d via the outlet passage valve 310a and the inlet valves 312a and 312d. In other words, hydraulic oil is supplied from the main pressure generating mechanism 210 to the brake calipers 21a and 21d without being boosted by the pump 314a.

[0054] As described above, the exhaust passage valves 310a and 310b and the intake valves 312a to 312d enter an open state when flows to the valves are cut off, while the intake passage valves 311a and 311b and the exhaust valves 313a to 313d enter a closed state when flows to the valves are cut off in the present embodiment. The states of the respective valves during the current cutoff are the same as the states of the respective valves when hydraulic oil is supplied from the master pressure generating mechanism 210 as is to the brake calipers 21a and 21d without being boosted by the pump 314a. Therefore, hydraulic oil from the main pressure generating mechanism 210 can be supplied to the brake calipers 21a and 21d even if the power supply system fails and no flows can be supplied to the respective valves.In other words, even in the event of failure of the wheel pressure generating mechanism 310, the pressure of the hydraulic oil sent to the brake calipers 21a and 21d can be controlled by the main pressure generating mechanism 210.

[0055] Next, a case will be described where hydraulic pressure boosted by the main pressure generating mechanism 210 is supplied to the front brake caliper 21a and the rear brake caliper 21d after being further boosted by the pump 314a. In this case, the intake port valve 311a and the intake valves 312a and 312d are in an open state, and the exhaust port valve 310a and the exhaust valves 313a and 313d are in a closed state.

[0056] Hydraulic oil supplied from the main pressure generating mechanism 210 via the first main pipe 261 is sent to the pump 314a via the inlet passage valve 311a for boosting. The hydraulic oil boosted by the pump 314a is sent to the brake calipers 21a and 21d via the inlet valves 312a and 312d. Furthermore, even if the main pressure generating mechanism 210 fails and hydraulic oil cannot be supplied from the main pressure generating mechanism 210, hydraulic oil can be sent from the pump 314a to the brake calipers 21a and 21d. In this case, the inlet passage valve 311a and the outlet passage valve 310a enter a closed state.

[0057] As described above, the present embodiment adopts a configuration in which, even if one of the main pressure generating device 200 and the wheel pressure generating device 300 becomes defective, the output from the other is not prevented.

[0058] Next, a case will be described where hydraulic pressure applied to the brake calipers 21a and 21d is reduced. In this case, the intake valves 312a and 312d are substantially closed, while the exhaust valves 313a and 313d are open, and the other valves are either open or closed, as required by the situation.

[0059] Hydraulic oil retained in the brake calipers 21a and 21d flows into the reservoir tank 317a via the outlet valves 313a and 313d, respectively. The hydraulic oil in the reservoir tank 317a is to be used when the hydraulic oil from the main pressure generating mechanism 210 is boosted to the pump 314a.

[0060] Now, operations of the brake control device 100 according to the Fig. 4 illustrated flowchart.

[0061] In step S1, the communication controller 112 of the brake control device 100 obtains various vehicle environment information from the respective sensors and the like at predetermined time intervals and stores the information in the RAM 103. In this case, the predetermined time interval is set to one millisecond. The respective sensors and the like include, in addition to the above-mentioned brake sensor 31, the vehicle speed sensor 32, the longitudinal acceleration sensor 33, the wheel speed sensor 34, the gear position sensor 35, the voltmeter 36, the master pressure controller 201, and the wheel pressure controller 301. Essentially, the respective sensors 31 to 36 constantly output detected values ​​when the ignition is turned on, and the interface 101 receives an output from the respective sensors 31 to 36 at predetermined time intervals.In addition, the master pressure controller 201 substantially constantly detects a hydraulic pressure in the master cylinder and a displacement amount of the primary piston 251 when the ignition is turned on, and the interface 101 receives the values ​​of the fluid pressure and the displacement amount. Furthermore, various vehicle environment information from the respective sensors 31 to 36, which have been obtained a predetermined number of times, is stored in the RAM 103 to detect changes in the vehicle environment information.

[0062] Next, in step S2, the braking force calculation device 111 calculates a maximum regenerative braking force Fr_max based on a vehicle speed and a gear position obtained in step S1. The maximum regenerative braking force is the largest regenerative braking force that can be generated by the regenerative braking device 18 and is determined based on a vehicle speed and a gear position. Methods for determining the maximum regenerative braking force include pre-storing table data stored in Fig. 5, in the ROM 102 and referencing the table data.

[0063] Next, in step S3, a regenerative braking force limit Fr_limit is calculated based on the vehicle speed obtained in step S1. Power generation efficiency of the regenerative braking device 18 decreases significantly as the wheels 15c and 15d decelerate. Therefore, regenerative braking force is limited to or below a vehicle speed at which power generation efficiency decreases.

[0064] Methods for determining the regenerative braking force limit Fr_limit include pre-storing in Fig. 6 illustrated table data in ROM 102 and referencing the table data. Fig. 6 illustrates that the regenerative braking force limit is gradually lowered from a vehicle speed Vs to a vehicle speed Ve, and is set to 0 at the vehicle speed Ve. The period from the vehicle speed Vs to the vehicle speed Ve is a period during which switching occurs from a regenerative braking force to a friction braking force to be described later. Furthermore, the vehicle speed Vs and the vehicle speed Ve are determined based on the performance of the regenerative braking device 18.

[0065] In addition, the regenerative braking force Fr_limit is set to 0 regardless of a vehicle speed V when a voltage value displayed on the voltmeter 36 reaches a predetermined voltage value, or in other words, when the amount of electricity stored in the electric storage device 17 reaches a predetermined amount, because power generated by the regenerative braking device 18 can no longer be stored. However, depending on the type of the electric storage device 17, the above-described method may shorten the service life of the electric storage device 17. Therefore, a method may alternatively be adopted in which the regenerative braking force Fr_limit is gradually reduced from a predetermined amount of stored electricity to 0.

[0066] Next, in step S4, the magnitudes of the maximum regenerative braking force Fr_max and the regenerative braking force limit Fr_limit are compared. If the maximum regenerative braking force Fr_max is equal to or greater than the regenerative braking force limit Fr_limit, in step S5, Fr_limit is substituted into the regenerative braking force Fr, so that a braking force equal to or lower than the regenerative braking force limit is output. If the maximum regenerative braking force Fr_max is lower than the regenerative braking force limit Fr_limit, in step S6, Fr_max is substituted into the regenerative braking force Fr, since the maximum regenerative braking force is equal to or lower than the regenerative braking force limit.

[0067] Next, in step S7, a friction braking force Ff is calculated based on the displacement amount of the input plunger 214 obtained in step S1. The friction braking force is a braking force acting on the respective wheels 15a to 15d when the main pressure generating device 200 and the wheel pressure generating device 300 are operating. Methods for determining a friction braking force include pre-storing Fig. 7 illustrates table data in ROM 102 and referencing the table data. Fig. Figure 7 illustrates characteristics measured on a dry asphalt road (road surface µ = 0.9).

[0068] Next, in step S8, the magnitudes of the friction braking force Ff and the regenerative braking force Fr are compared. When the friction braking force Ff is greater than the regenerative braking force Fr, the driver-requested braking force (friction braking force) exceeds the regenerative braking force. Therefore, in step S9, Ff - Fr is substituted into a friction braking force output command value Ffo to be sent to the main pressure controller 201 and the wheel pressure controller 301, while Fr is substituted into a regenerative braking force output value Fro to be sent to the regenerative braking device 18.

[0069] When the friction braking force Ff is equal to or less than the regenerative braking force Fr, since a braking force equivalent to the friction braking force Ff can be output by the regenerative braking force Fr alone, 0 is substituted into the friction braking force output error value Ffo in step S10, and Ff is substituted into the regenerative braking force output value Fro. Subsequently, in step S11, the communication controller 112 outputs a braking force signal corresponding to an existing braking force to the main pressure generating device 200, the wheel pressure generating device 300, and the regenerative braking device 18. The friction braking force output error value Ffo is output to one of the main pressure generating device 200 and the wheel pressure generating device 300, but mainly to the main pressure generating device 200. The regenerative braking force output value Fro is output to the regenerative braking device 18.

[0070] A case will be described below in which the friction braking force output error value Ffo is output to the master pressure generating device 200 and the regenerative braking force output value Fro is output to the regenerative braking device 18.

[0071] An execution of the Fig. 4, for example, leads to the Fig. 8 illustrated edition. Fig. Figure 8 illustrates an output in a case where the magnitudes of a friction braking force and a regenerative braking force are equal to each other and an input plunger displacement amount does not fluctuate. The regenerative braking force decreases from a vehicle speed Vs to a vehicle speed Ve as the regenerative braking force limit decreases, whereas the friction braking force increases to compensate for the decrease in the regenerative braking force. In the Fig. In the case illustrated in Fig. 8, a total braking force combining the friction braking force and the regenerative braking force is constant in all areas because the input plunger displacement amount, or in other words, the command value, does not fluctuate.

[0072] However, in reality, fluctuations occur, such as those seen in the Fig. 9 and Fig. 10 when the main pressure generating device 200 and the regenerative braking device 18 or the wheel pressure generating device 300 and the regenerative braking device 18 are arranged according to the Fig. 4 illustrated flowchart. Fig. Fig. 9 illustrates a result of controlling the main pressure generating device 200 and the regenerative braking device 18 according to the Fig. 4 illustrated flowchart and Fig. Fig. 10 illustrates a result of controlling the wheel pressure generating device 300 and the regenerative braking device 18 according to the Fig. 4. Such fluctuations are caused by a fluctuation in a reaction force of the brake pedal, which accompanies fluctuations in a hydraulic pressure in the master cylinder, which is generated when a friction braking force, a spring reaction force, or a sliding resistance is generated.

[0073] The Fig. 9 and Fig. The examples illustrated in Figure 10 are both cases where the brake pedal is depressed with a constant depression force. Fig. In the example illustrated in Figure 9, during the transition from regenerative braking to friction braking, the pedal reaction force decreases, the pedal displacement amount increases, the input plunger displacement amount increases, and the friction braking force command value increases. As a result, fluctuations in the total braking force and deceleration occur.

[0074] In addition, in the Fig. In the example illustrated in Figure 10, during the transition from regenerative braking to friction braking, a pedal reaction force increases, a pedal displacement amount increases, an input plunger displacement amount decreases, and a friction braking force command value decreases. As a result, fluctuations in the total braking force and deceleration occur.

[0075] Now, a method for addressing the above-described problem by controlling the master pressure generating device 200 and the regenerative braking device 18 will be described.

[0076] For example, one method includes first determining a total braking force, which is the sum of a friction braking force and a regenerative braking force, from which Fig. 11 based on a relationship between an input plunger displacement amount Xir and a primary piston displacement amount Xpp. The method considers fluctuations in a pedal reaction force and a primary piston displacement amount during a switching period from regenerative braking to friction braking. While a change in characteristics in which the total braking force increases occurs when the primary piston is displaced to output a friction braking force, such a displacement of the primary piston causes a decrease in the pedal reaction force and lowers the total braking force.

[0077] As a result, the total braking force does not fluctuate, for example, when the regenerative braking force is approximately equal to the total braking force during regenerative braking, despite fluctuations in the primary piston displacement and the pedal reaction force after the switching period from regenerative braking to friction braking. As a result, fluctuation in deceleration can be suppressed. Furthermore, although in the present embodiment, a total braking force is calculated using the Fig. 11, methods for determining a total braking force are not limited thereto, and may alternatively be determined using a mathematical expression.

[0078] Next, operations of the brake control device 100 are now performed using the Fig. 11 illustrated total braking force characteristics according to a Fig. 12 illustrated flowchart.

[0079] In the Fig. 12, the operations in steps S1 to S6 and S11 are essentially the same as in the flowchart shown in Fig. 4 illustrated flowchart.

[0080] In step S12, a total braking force Ft is determined, which is a braking force of the entire system and which combines a friction braking force and a regenerative braking force.

[0081] Methods for determining the total braking force Ft include pre-storing in Fig. 11 illustrated table data in ROM 102 and referencing the table data.

[0082] Fig. 11 illustrates a total braking force to be output with respect to a pedal reaction force. Several characteristics exist depending on a relationship between the input plunger displacement amount Xir and the primary piston displacement amount Xpp. In the same manner as in the first embodiment, since a pedal reaction force varies depending on a hydraulic pressure in the master cylinder, a sliding resistance, or the like, a spring reaction force can be determined from F = P Air + Fk + Fo, where P denotes a hydraulic pressure in the master cylinder, Air denotes a cross-sectional area of ​​the input plunger, Fk denotes a spring reaction force, and Fo denotes a reaction force such as a sliding resistance. The cross-sectional area of ​​the input plunger Air, the spring reaction force Fk, and the reaction force such as a sliding resistance, Fo, are all determined according to a specification of the braking system.In addition, during friction braking in which regenerative braking is not applied, a characteristic Xir = Xpp, in which the input plunger displacement amount Xir and the primary piston displacement amount Xpp are approximately equal to each other, is used as an initial characteristic, so that a boost ratio of hydraulic pressure generated by displacements of the input plunger and the primary piston is always constant. The characteristic shown in . Fig. The ratio illustrated in Figure 11 is a characteristic curve measured on a dry asphalt road (road surface µ = 0.9).

[0083] Next, in step S13, in the Fig. 12, the magnitudes of the total braking force Ft and the regenerative braking force Fr are compared. When the total braking force Ft is greater than the regenerative braking force Fr, a braking force that cannot be output by a regenerative braking force must be output by a friction braking force. Therefore, in step S14, Ft - Fr is substituted into a friction braking force output command value Ffo to be sent to the main pressure controller 201, and Fr is substituted into a regenerative braking force output value Fro to be sent to the regenerative braking device 18.

[0084] Conversely, when the total braking force Ft is equal to or smaller than the regenerative braking force Fr, 0 is substituted into the friction braking force output command value Ffo in step S15, and Ft is substituted into the regenerative braking force output value Fro, since a braking force equivalent to the total braking force Ft can be output by the regenerative braking force Fr alone.

[0085] In a case where the main pressure generating device 200 and the regenerative braking device 18 are arranged according to the Fig. 11 illustrated total braking force characteristics and the Fig. 12, for example, while an initially selected characteristic curve in Fig. 11 In step S12, in which a total braking force is determined when a regenerative braking force and a total braking force are approximately equal to each other during regenerative braking, the above-mentioned characteristic expressed as Xir = Xpp is used. Since the friction braking force must be set to 0 when the regenerative braking force is greater than the total braking force, Xpp inevitably becomes smaller than Xir. Therefore, when the regenerative braking force and the total braking force are approximately equal to each other during regenerative braking, as is the case in the present example, a characteristic expressed as Xpp = 0 should be selected.

[0086] When entering the switching period from regenerative braking to friction braking, since the regenerative braking force becomes smaller than the total braking force and a friction braking force must be generated, Xpp becomes greater than 0, and a characteristic curve closer to Xir = Xpp than to Xpp = 0 is used. At this point, the total braking force remains unchanged before and after the switching period from regenerative braking to friction braking, although the total braking force increases in a case where a pedal reaction force does not change, and as a result, fluctuations in deceleration can be suppressed, as shown in Fig. 13 illustrates.

[0087] Next, as another method for suppressing fluctuations in a total braking force and a deceleration as shown in Fig. 10, a method for controlling the wheel pressure generating device 300 and the regenerative braking device 18 will be described.

[0088] In controlling the wheel pressure generating device 300, a method includes, for example, determining a total braking force which is a sum of a friction braking force and a regenerative braking force from which Fig. 14 based on a hydraulic pressure Px increased or decreased by the wheel pressure generating device 300. The method takes into account fluctuations in the pedal reaction force and the hydraulic pressure Px increased or decreased by the wheel pressure generating device 300 during the switching period from regenerative braking to friction braking. While a characteristic change in which the total braking force decreases occurs when the wheel pressure generating device 300 increases pressure to output a friction braking force, such an increase in pressure by the wheel pressure generating device 300 causes an increase in the pedal reaction force, resulting in an increase in the total braking force.

[0089] As a result, for example, when the regenerative braking force is approximately equal to the total braking force during regenerative braking, the total braking force does not fluctuate despite fluctuations in the hydraulic pressure increased or decreased by the wheel pressure generating device 300 or in the pedal reaction force after the switching period from regenerative braking to friction braking. As a result, fluctuation in deceleration can be suppressed. Although in the present embodiment, a total braking force using the Fig. 14, methods for determining the total braking force are not limited to such tables, and it may alternatively be determined using a mathematical expression.

[0090] Furthermore, the method for controlling the wheel pressure generating device 300 differs from the method for controlling the main pressure generating device 200 only in the manner in which a total braking force is determined, and otherwise essentially follows the method described in Fig. 12 illustrated flowchart.

[0091] By controlling the wheel pressure generating device 300 and the regenerative braking device 18 using the Fig. 14 illustrated total braking force characteristics according to the Fig. 12, fluctuations in a total braking force and a deceleration can be suppressed even if a pedal reaction force fluctuates, as shown in Fig. 15 illustrates.

[0092] While a braking force generating device in the present embodiment consists of the main pressure generating device 200, the wheel pressure generating device 300, and the regenerative braking device 18, the main pressure generating device 200 may be a negative pressure boosting device using a negative pressure of the engine 11, and the wheel pressure generating device 300 may simply be a hydraulic pipe or an ABS (Anti-lock Brake System) that prevents the wheels from locking.

Claims

[1] Braking system with: a hydraulic brake device for generating a friction braking force comprising a pedal (16), at least one brake caliper (21a - 21d) a main pressure generating device (200) with a main cylinder (212) and a piston (251) which pressurizes the main cylinder (212), a wheel pressure generating device (300) for generating a hydraulic pressure in the at least one brake caliper (21a - 21d); and a regenerative braking device (18) and a brake control device (100) for calculating a braking force distribution between friction brakes and regenerative braking, wherein the braking system is configured to adjust a total braking force (Ft) based on a pedal reaction force and a displacement amount of the piston (251) that pressurizes the master cylinder (212), or adjust the total braking force (Ft) based on the pedal reaction force and the generated hydraulic pressure in the at least one brake caliper (21a - 21d) to keep the total braking force (Ft) at a constant level when transitioning from regenerative braking to friction braking in response to a reduction in vehicle speed. [2] A brake system according to claim 1, wherein the brake control device (100) is adapted to store braking force characteristics based on the pedal reaction force and the displacement amount of the piston (251). [3] A braking system according to claim 1, wherein the braking control device (100) is configured to store braking force characteristic data based on the pedal reaction force and the generated hydraulic pressure in the at least one brake caliper (21a - 21d). [4] Braking system according to one of the preceding claims, wherein the brake control device (100) is configured to calculate a maximum regenerative braking force (Fr_max) based on a vehicle speed and / or a gear position; and to calculate a regenerative braking force limit (Fr_limit) based on the vehicle speed, and where the brake control device (100) is configured to set the regenerative braking force limit (Fr_limit) as the regenerative braking force (Fr) when the maximum regenerative braking force (Fr_max) is greater than the regenerative braking force limit (Fr_limit), and to set the maximum regenerative braking force (Fr_max) as the regenerative braking force (Fr) when the maximum regenerative braking force (Fr_max) is less than the regenerative braking force limit (Fr_limit), and the brake control device (100) is configured to output the regenerative braking force to the regenerative braking device (18), and to output a difference between the total braking force (Ft) and the regenerative braking force (Fr) to the at least one brake caliper (21a - 21d) when the total braking force (Ft) is greater than the regenerative braking force (Fr), and to output the total braking force (Ft) to the regenerative braking device (18) when the total braking force (Ft) is less than the regenerative braking force (Fr). [5] Motor vehicle in which the braking system according to claim 1 is installed.

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