Hydraulic brake system

Abstract

To provide a hydraulic brake system having a new structure which does not include a master cylinder.SOLUTION: A hydraulic brake system comprises: a hydraulic brake which is arranged in each of a plurality of wheels; and an electric-driven cylinder device connected with a wheel cylinder in which one or more wheel cylinders are arranged to each of the plurality of hydraulic brakes. Each of the plurality of electric-driven cylinder devices of the hydraulic brake system includes: a housing; a piston which is fluid-tightly and slidably engaged with the housing; an electric motor as a driving source; a rotation linear motion conversion device which converts rotation of the electric motor into linear motion of the piston; and a volumetric change chamber which is arranged in front of the piston and connected with a hydraulic pressure chamber of the wheel cylinder of one or more hydraulic brakes. Therefore, the hydraulic brake system including the plurality of hydraulic brakes and the plurality of electric-driven cylinders is a novel one.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a hydraulic brake system that applies hydraulic braking force to a vehicle.

Background Art

[0002] Patent Document 1 describes a hydraulic brake system that does not include a master cylinder and includes a plurality of hydraulic brakes and pressure generating devices respectively connected to the wheel cylinders of the plurality of hydraulic brakes. However, the structure of the pressure generating device is not disclosed in Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a hydraulic brake system with a new structure that does not include a master cylinder. Means and effects for solving the problems

[0005] The hydraulic brake system according to the present invention includes hydraulic brakes respectively provided on a plurality of wheels, and electric cylinder devices respectively connected to wheel cylinders of one or more of the plurality of hydraulic brakes. The plurality of electric cylinder devices included in the present hydraulic brake system each include a housing, a piston that is liquid-tightly and slidably fitted into the housing, an electric motor as a drive source, a linear-rotary motion conversion device that performs conversion between the rotation of the electric motor and the linear movement of the piston, and a volume change chamber provided in front of the piston and connected to a hydraulic chamber of a wheel cylinder of one or more hydraulic brakes. Thus, the hydraulic brake system according to the present invention including a plurality of hydraulic brakes and a plurality of electric cylinder devices is not described in Patent Document 1. The hydraulic brake system according to the present invention is novel.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0007] Hereinafter, a hydraulic brake system which is an embodiment of the present invention will be described with reference to the drawings.

Examples

[0008] The hydraulic brake system according to this embodiment does not include a manual hydraulic source (for example, a master cylinder) that generates hydraulic pressure due to an operation of a brake operation member by a driver.

[0009] As shown in FIG. 3, this hydraulic brake system includes hydraulic brakes 10FL, 10FR, 10RL, 10RR provided for each of four wheels WFL, WFR, WRL, WRR located at the front, rear, left, and right of the vehicle, and electric cylinder devices 12FL, 12FR, 12RL, 12RR connected in a one-to-one correspondence to the hydraulic brakes 10FL, 10FR, 10RL, 10RR, respectively. Hereinafter, the subscripts FL, FR, RL, RR, F, R representing the wheel positions may be omitted when collectively referring, when explaining regardless of the wheel position, etc.

[0010] In this embodiment, as shown in FIG. 1, the hydraulic brake 10 includes a pair of friction engaging members, i.e., friction pads 21 and 22, which are located on both sides of a brake rotating body 20 rotatably provided integrally with a wheel W, and a pressing device 23 for pressing the friction pads 21 and 22 against the brake rotating body 20. The pressing device 23 includes a caliper 24 movably held in a direction parallel to the rotation axis N of the wheel (hereinafter referred to as the rotation axis direction) on a non-rotating member, and a wheel cylinder 25 provided on the caliper 24. The wheel cylinder 25 includes a piston (hereinafter referred to as the wheel-side piston) 27 fitted in a cylinder bore formed in the caliper 24 in a liquid-tight and slidable manner, and a hydraulic chamber 26 provided behind the wheel-side piston 27. Further, a piston seal 28 is attached to the caliper 24.

[0011] When hydraulic pressure is supplied to the hydraulic chamber 26 of the wheel cylinder 25, the wheel-side piston 27 is advanced and the caliper 24 is moved in the rotation axis direction. The pair of friction pads 21 and 22 are pressed against the brake rotating body 20 by a pressing force Fp corresponding to the hydraulic pressure P in the hydraulic chamber 26 and frictionally engaged therewith. Thereby, the rotation of the wheel is suppressed. Further, when the hydraulic pressure P in the hydraulic chamber 26 is increased or decreased, the pressing force Fp is increased or decreased.

[0012] The electric cylinder device 12 includes a housing 40, a piston member (hereinafter referred to as the electric piston member) 42 as a piston fitted in the housing 40 in a liquid-tight and slidable manner, an electric motor 44 as a drive source, a linear-rotary motion conversion device (hereinafter simply abbreviated as a linear motion conversion device) 48 for converting the rotation of the electric motor 44 into the linear movement of the electric piston member 42, and a reservoir 50. The electric piston member 42 is held in the housing 40 so as not to be rotatable around the axis M of the electric piston member 42 and to be movable in a direction parallel to the axis M.

[0013] The reservoir 50 stores the working fluid used in the hydraulic brake 10, and stores the working fluid for enabling constant braking even in the case of wear of the friction pads 21 and 22, change in the consumed fluid amount due to elastic deformation by pressurization, or after the working fluid has started to leak. Further, in the reservoir 50, the working fluid returned from the wheel cylinder 25 of the hydraulic brake 10 connected to the electric cylinder device 12 is stored.

[0014] In the present embodiment, the electric piston member 42 is composed of a piston portion 47 and a piston rod (hereinafter simply referred to as a rod) portion 46 that is fitted so as to be movable integrally with the piston portion 47. Note that the piston portion 47 and the rod portion 46 may be integrally manufactured. In the present embodiment, the piston described in the claims can be considered to correspond to the piston portion 47, or can be considered to correspond to the electric piston member 42, etc.

[0015] The housing 40 includes a rear housing 40r as a first housing that houses the electric motor 44, a front housing 40f as a second housing having a bottomed cylindrical shape, and an intermediate housing 40m located between the front housing 40f and the rear housing 40r. These rear housing 40r, intermediate housing 40m, and front housing 40f are separable from each other.

[0016] The electric motor 44 is provided coaxially with the electric piston member 42 on the outer peripheral side of the rod portion 46. Further, the electric motor 44 is mainly housed in the rear housing 40r, and includes a plurality of coils 52 as a stator held by the rear housing 40r and the intermediate housing 40m, and a rotor 54 having a generally cylindrical shape and provided with a plurality of magnets Z located on the inner peripheral side of the coil 52. The rotor 54 is rotatably held by a pair of bearings 56 and 57 provided at intervals in a direction parallel to the axis M between the rear housing 40r and the intermediate housing 40m. Note that in the rotor 54, the magnets Z may be provided on the outer peripheral surface or embedded inside.

[0017] Further, the linear motion conversion device 48 is provided between the inner peripheral portion of the rotor 54 and the outer peripheral portion of the rod portion 46. The linear motion conversion device 48 includes, in this embodiment, a ball screw mechanism, and includes a male screw portion 62 provided on the outer peripheral portion of the rod portion 46, a female screw portion 63 provided on the inner peripheral portion of the rotor 54, and a plurality of balls 64 interposed between the male screw portion 62 and the female screw portion 63.

[0018] A cylinder bore is formed in the front housing 40f, and an electric piston member 42 is held in the cylinder bore in a liquid-tight and slidable manner via a seal member 66. The front of the electric piston member 42 in the cylinder bore of the front housing 40f is a volume change chamber 67. A return spring 68 is provided between the electric piston member 42 and the bottom of the front housing 40f. An elastic force is applied to the electric piston member 42 in the retracting direction by the return spring 68.

[0019] A front port 70 and a rear port 72 are provided at portions spaced in a direction parallel to the axis M of the front housing 40f (the portion surrounding the volume change chamber 67 of the housing 40). The hydraulic chamber 26 of the wheel cylinder 25 is directly connected to the front port 70 via a liquid passage 74, and a reservoir 50 is connected to the rear port 72. The rear port 72 can be referred to as an idle port.

[0020] The front port 70 is always in an open state, and the volume change chamber 67 and the hydraulic chamber 26 of the wheel cylinder 25 are always in a communicating state via the liquid passage 74. In this embodiment, no electromagnetic valve or the like is provided in the liquid passage 74.

[0021] The rear port 72 is in an open state when the electric piston member 42 is in the retracted end position, but is switched to a closed state by the forward movement of the electric piston member 42, and hydraulic pressure is generated in the volume change chamber 67. The retracted end position of the electric piston member 42 is a position where the electric piston member 42 abuts against a stopper (not shown) provided in the housing 40.

[0022] Further, in the electric cylinder device 12 according to the present embodiment, the diameter D (see FIG. 2) of the piston portion 47 of the electric piston member 42 is small, and the maximum stroke L of the electric piston member 42 is large. The maximum stroke L of the electric piston member 42 can be considered, for example, as the length L between the front end face of the piston portion 47 and the bottom face of the front housing 40f when the electric piston member 42 is in the retracted end position. Further, the full stroke which is the maximum stroke L includes the idle stroke Lp which is the stroke from the retracted end position of the electric piston member 42 until the idle port 72 is closed.

[0023] For example, in a master cylinder as a manual hydraulic source, a brake pedal operable by a driver is connected to the pressure piston, and the pressure piston is advanced as the brake pedal is depressed. On the other hand, since the brake pedal is depressed by the driver, the maximum stroke of the brake pedal is determined based on ergonomics etc., and the maximum stroke of the pressure piston is also determined by the maximum stroke of the brake pedal. Therefore, the maximum stroke of the pressure piston of the master cylinder is usually smaller than 50 mm.

[0024] On the other hand, in the electric cylinder device 12 according to the present embodiment, the electric piston member 42 is not moved by the operation of the brake operating member, but is moved by the electric motor 44. Therefore, there are no restrictions such as ergonomics, and the maximum stroke can be increased. And since the maximum stroke of the electric piston member 42 can be increased, even if the diameter D (pressure receiving area SA) of the electric piston member 42 is small, it is possible to supply the required amount of hydraulic fluid in the wheel cylinder 25. In other words, in order to supply the required amount of hydraulic fluid in the wheel cylinder 25, by increasing the maximum stroke of the electric piston member 42, the pressure receiving area SA (diameter D) of the piston portion 47 can be made small.

[0025] Thus, by reducing the pressure-receiving area SA of the electric piston member 42, the value obtained by dividing the pressure-receiving area SW of the wheel-side piston 27 of the wheel cylinder 25 of the hydraulic brake 10 by the pressure-receiving area SA of the electric piston member 42 (hereinafter abbreviated as the ratio of the pressure-receiving areas) SW / SA can be increased. Therefore, when the pressing force Fp required in the wheel cylinder 25 is the same, the axial force Fs applied to the rod portion 46 of the linear motion conversion device 48 can be reduced, and accordingly, the power consumption of the electric motor 44 can be reduced.

[0026] This will be described in detail below. (a) By increasing the ratio of the pressure-receiving areas SW / SA and reducing the axial force Fs applied to the rod portion 46, the gear ratio of the electric motor 44 (for example, which can be expressed as "the rotational speed of the electric motor 44 / the rotational speed of the rod portion 46") can be reduced, or the output of the electric motor 44 can be reduced.

[0027] If the axial force Fs applied to the rod portion 46 is large, it may be considered to provide a speed reducer between the electric motor 44 and the linear motion conversion device 48 and increase the reduction ratio. On the other hand, in a speed reducer, involute gears are usually used, but involute gears transmit force while the teeth slide against each other during meshing. Also, rotational resistance is generated due to the thrust load of the gears of the speed reducer and the friction caused by the pushing and pulling between the shafts, increasing the energy consumption in the speed reducer. Thus, when the reduction ratio is increased and the efficiency of the speed reducer is greatly reduced, the transmission efficiency of the electric motor 44 (for example, which can be expressed as "the energy transmitted to the piston portion 47 / the energy supplied to the electric motor 44") is greatly reduced.

[0028] In contrast, in this embodiment, since the axial force Fs is reduced, the reduction ratio can be reduced, the speed reducer can be eliminated, the output of the electric motor 44 can be reduced, etc., and accordingly, the transmission efficiency of the electric motor 44 can be increased. Note that FIGS. 1 and 2 show the case where no speed reducer is provided in the electric cylinder device 12.

[0029] (b) Since the axial force Fs applied to the rod portion 46 is reduced, the diameter of the rod portion 46 of the linear motion conversion device 48 can be reduced. Therefore, the lead angle can be increased while suppressing a decrease in the reduction ratio of the linear motion conversion device 48 (which can be represented, for example, by "feed speed / lead × input rotation speed of the linear motion conversion device 48"), and it becomes possible to increase the transmission efficiency of the electric motor 44.

[0030] If the axial force Fs is large, it is necessary to increase the balls 64 of the ball screw mechanism and increase the diameter of the rod portion 46. When the lead angle is the same, if the diameter of the rod portion 46 is increased, the lead increases, so the reduction ratio of the linear motion conversion device 48 decreases. Therefore, it is necessary to increase the gear ratio of the electric motor 44 or increase the output of the electric motor 44. Also, if the lead angle is decreased, the reduction ratio of the linear motion conversion device 48 increases, so the gear ratio of the electric motor 44 can be decreased. However, due to the decrease in the lead angle, the transmission efficiency of the electric motor 44 decreases.

[0031] On the other hand, in the electric cylinder device 12 according to the present embodiment, since the axial force Fs can be reduced, the diameter of the rod portion 46 can be reduced, and the lead angle can be increased while suppressing a decrease in the reduction ratio of the linear motion conversion device 48. Therefore, the transmission efficiency of the electric motor 44 can be increased. In other words, the position of the linear motion conversion device 48 in the electric cylinder device 12 is designed such that the axial force Fs applied to the linear motion conversion device 48 becomes as small as possible. For example, in the electric cylinder device 12, the electric motor 44, the linear motion conversion device 48, and the piston portion 47 are arranged in series, and the hydraulic brake 10 is connected to the variable volume chamber 67 in front of the piston portion 47. In this hydraulic brake system, since the ratio of the pressure receiving area is increased, the pressing force of the friction pads 21, 22 against the brake rotating body 20 can be increased with respect to the hydraulic pressure in the volume change chamber 67. Therefore, the linear motion conversion device 48 is arranged upstream of the piston portion 47 and downstream of the electric motor 44 or the speed reducer.

[0032] (c) The stroke of the electric piston member 42 is large, and the length of the cylinder bore formed in the front housing 40f is increased. However, the position of the idle port 72 in the housing 40 of the electric cylinder device 12 is the same regardless of the length of the cylinder bore formed in the front housing 40f. Therefore, the ratio (Lp / L) of the idle stroke Lp to the maximum stroke L of the electric piston member 42 decreases as the maximum stroke L becomes longer. As a result, the transmission efficiency of the electric motor 44 increases. From the above, it is possible to increase the transmission efficiency of the electric motor 44 and reduce the power consumption of the electric motor 44.

[0033] In addition, since it is possible to reduce the gear ratio of the electric motor 44, a speed reducer becomes unnecessary or the speed reducer can be miniaturized, and the electric cylinder device 12 can be miniaturized and lightened. Furthermore, the number of parts in the electric cylinder device 12 can be reduced.

[0034] Also, in the linear motion conversion device 48, since the lead angle θ can be increased, the forward and reverse efficiency, that is, the forward efficiency (wheel cylinder pressure / axial force) and the reverse efficiency (axial force / wheel cylinder pressure) can be increased.

[0035] Although the case where the linear motion conversion device 48 is a ball screw mechanism has been described above, the linear motion conversion device 48 can include a trapezoidal screw mechanism, and even in the case of including a trapezoidal screw mechanism, the same effects as in the above case can be obtained, that is, the transmission efficiency of the electric motor 44 can be increased and the power consumption can be reduced. In particular, in a trapezoidal screw mechanism, in order to reduce the frictional force acting between the male screw portion and the female screw portion, the role of grease as a lubricant is significant. Generally, the frictional force is greater when the surface pressure acting between the male screw portion and the female screw portion is large than when it is small. Also, when the surface pressure is smaller than the set value, good lubrication effect can be obtained between the male screw portion and the female screw portion by grease. However, when the surface pressure becomes equal to or greater than the set value, the temperature rises, the viscosity of the grease decreases, and the lubrication effect deteriorates. As a result, there are problems such as an increase in the frictional force acting between the male screw portion and the female screw portion, and abrasion of the male screw portion or the female screw portion (this state may be referred to as grease failure). On the other hand, by increasing the diameter of the rod portion 46, the sliding area between the male screw portion and the female screw portion can be increased, and by reducing the surface pressure acting between them, the frictional force can be reduced. However, other problems such as an increase in the size of the electric cylinder device 12 or a change in the reduction ratio of the linear motion conversion device 48 will occur.

[0036] In contrast, in this embodiment, since the axial force Fs applied to the rod portion 36 can be reduced, the surface pressure can be reduced, the decrease in the viscosity of the grease can be suppressed, and the reduction of the frictional force between the male screw portion and the female screw portion can be achieved satisfactorily. Also, by suppressing the overheating of the grease, the deterioration of the grease can be suppressed. Furthermore, generally, when the lead angle is small, grease failure is likely to occur. However, since the lead angle can be increased, grease failure is less likely to occur, and the reduction of the frictional force can be further achieved.

[0037] In addition, when the linear motion conversion device 48 includes a ball screw mechanism, in the ball screw mechanism, grease is used to reduce the sliding resistance between the ball 64 and the male screw portion 62 and the female screw portion 63. Even in that case, as described above, the same effect can be achieved by reducing the axial force Fs.

[0038] On the one hand, as shown in FIG. 2, the electric cylinder device 12 is easily disassemblable. Specifically, the rear housing 40r, the intermediate housing 40m, and the front housing 40f are coupled by a coupling device. The coupling device can include, for example, a plurality of screw members 80 extending in the axial direction and nut members 82 screwed onto the screw members 80.

[0039] Also, inside the rear housing 40r, the intermediate housing 40m, and the front housing 40f, bearings 56, 57, an electric motor 44 (coil 52, rotor 54), a rod portion 46, a piston portion 47, a seal member 66, a ball 64, etc. are respectively assembled so as to be easily separable. Therefore, by removing the nut member 82, the electric cylinder device 12 can be separated into the front housing 40f, the intermediate housing 40m, and the rear housing 40r, and each component of the electric cylinder device 12 can be removed.

[0040] The electric cylinder device 12 is not provided in the caliper 24, but is provided in a liquid passage 74 extending from the caliper 24. On the other hand, when an electric actuator of an electric brake for suppressing the rotation of the wheel W is provided in the caliper 24, it is necessary to seal or unitize the electric actuator in order to prevent mud and water from splashing on the electric actuator. In contrast, for the present electric cylinder device 12, compared with the electric actuator of the electric brake, since it is difficult for mud, water, etc. to splash on it, the necessity of unitizing or sealing the housing is reduced. Also, in the present embodiment, no electromagnetic valve is provided on the downstream side of the electric cylinder device 12. Therefore, when disassembling the electric cylinder device 12, there is no risk that foreign matter or the like will enter the orifice portion of the electromagnetic valve and cause a problem with the electromagnetic valve. As a result, the electric cylinder device 12 can be made into a structure that can be easily disassembled, and maintenance can be carried out individually for each of the components. For example, when a defect occurs in one of the plurality of components, it is not necessary to replace the entire electric cylinder device 12, and the defective component can be replaced or the like. As a result, it becomes possible for the user to reduce the maintenance cost of the vehicle and reduce waste. In addition, since the electric cylinder device 12 is provided near the wheel, the maintenance work becomes easier.

[0041] As shown in FIGS. 1 and 3, for each of the electric cylinder devices 12, a brake ECU 86 as a control unit mainly composed of a computer is provided in a one-to-one correspondence. The electric cylinder device 12 is controlled by the brake ECU 86 respectively. The brake ECU 86 includes a drive circuit 88 such as an inverter, and controls the supply current to the electric motor 44 by controlling the drive circuit 88 to control the operation of the electric motor 44. In addition, a liquid level height sensor 90, a stroke sensor 92, a rotation speed sensor 94, a wheel speed sensor 100 as a wheel speed detection device, a hydraulic pressure sensor 102, etc., which are components of the electric cylinder device 12, are connected to the brake ECU 86.

[0042] The liquid level height sensor 90 detects the position (liquid level height) of the working fluid contained in the reservoir 50. The liquid level height sensor 90 can be, for example, a sensor that detects the liquid level height using optics, magnetism, capacitance, ultrasonic waves, pressure, etc. In addition, it can be a contact type or non-contact type detector, or a detector using a float. The stroke sensor 92 detects the stroke of the electric piston member 42, and can detect the stroke, for example, by detecting the relative position of the rod portion 46 or the piston portion 47 with respect to the housing 40. The rotation speed sensor 94 detects the rotation speed of the electric motor 44. Also, based on the rotation speed of the electric motor 44, the stroke of the electric piston member 42 can be obtained.

[0043] The wheel speed sensors 100 are provided corresponding to each of the wheels W located at the front, rear, left, and right, and each detects the rotational speed of the wheel W. Based on the detection values of the four wheel speed sensors 100, the traveling speed of the vehicle is obtained, or the slip state of each of the wheels W is obtained.

[0044] The hydraulic pressure sensor 102 detects the hydraulic pressure in the hydraulic pressure chamber 26 of the wheel cylinder 25 of the hydraulic brake 10 provided for each of the wheels W located at the front, rear, left, and right (hereinafter sometimes simply referred to as the hydraulic pressure of the hydraulic brake 10 or the hydraulic pressure of the wheel cylinder 25). The hydraulic pressure sensor 102 is often provided in the liquid passage 74.

[0045] Also, as shown in FIG. 3, each of the electric cylinder devices 12 is provided with a power source V corresponding one-to-one. The power source V can be, for example, an ion lithium battery or a capacitor. The electric cylinder device 12, that is, the brake ECU 86, the drive circuit 88, the liquid level height sensor 90, the stroke sensor 92, the rotation speed sensor 94, the wheel speed sensor 100, the hydraulic pressure sensor 102, etc. are operable by an individual, in other words, a power source V dedicated to the electric cylinder device.

[0046] Further, a driving support ECU 96 mainly composed of a computer is connected to a brake ECU 86 (each of the brake ECUs 86FL, 86FR, 86RL, and 86RR provided for each of the front, rear, left, and right wheels WFL, WFR, WRL, and WRR) via a vehicle body communication network such as a CAN (Controller Area Network) 95. In this embodiment, communication is performed between the driving support ECU 96 and each of the brake ECUs 86 via the CAN 95, and communication is also performed between the four brake ECUs 86 with each other. The driving support ECU 96 outputs a braking request to each of the electric cylinder devices 12, or acquires and outputs a required braking force. An operation state detection device 104, a surrounding information acquisition device 106, etc. are connected to the driving support ECU 96.

[0047] The operation state detection device 104 detects the operation state (e.g., stroke, operating force) of a brake operation member (not shown) operable by the driver. The surrounding information acquisition device 106 includes a camera, a radar device, etc., acquires objects located around the host vehicle which is a vehicle, lane lines of the road around the host vehicle, the curved shape of the road, etc., and acquires the relative positional relationship between the object and the host vehicle.

[0048] In the hydraulic brake system configured as described above, in the driving support ECU 96, it is determined whether there is a braking request based on the operation state of the brake operation member detected by the operation state detection device 104, the relative positional relationship between the surrounding object and the host vehicle acquired by the surrounding information acquisition device 106, etc. When there is a braking request, the required braking force is acquired based on the operation state of those brake operation members, the relative positional relationship between the surrounding object and the host vehicle, etc., and is supplied to the electric cylinder devices 12 (brake ECU 86) respectively.

[0049] In the brake ECU 86, based on the required braking force, the target hydraulic pressure of the hydraulic brake 10 is acquired respectively, and the supply current to the electric motor 44 is controlled so that the actual hydraulic pressure which is the detected value of the hydraulic pressure sensor 102 approaches the target hydraulic pressure, and the electric piston member 42 is moved forward and backward. In the electric cylinder device 12, when the electric piston member 42 is advanced, the volume of the volume change chamber 67 decreases, hydraulic fluid is supplied to the hydraulic chamber 26 of the wheel cylinder 25, and the hydraulic pressure increases. When the electric piston member 42 is retracted in the electric cylinder device 12, the volume of the volume change chamber 67 increases, and the hydraulic fluid flows out from the hydraulic chamber 26 of the wheel cylinder 25, and the hydraulic pressure decreases. The electric piston member 42 is advanced and retracted so that the hydraulic pressure of the wheel cylinder 25 approaches the target hydraulic pressure, and the supply current to the electric motor 44 is controlled.

[0050] When the braking requirement disappears, in the electric cylinder device 12, the electric piston member 42 is returned. Thereby, the idle port 72 opens, and the hydraulic chamber 26 is communicated with the reservoir 50. The electric piston member 42 is returned until it abuts against the stopper. In the wheel cylinder 25, the wheel side piston 27 is returned by the piston seal 28, and the friction pads 21, 22 are separated from the brake rotating body 20. The hydraulic brake 10 becomes in an inoperative state.

[0051] Also, when the slip of the wheel W becomes excessive, slip suppression control is performed. In the slip suppression control, by controlling the supply current to the electric motor 44, the electric piston member 42 is retracted and advanced, so that the hydraulic pressure in the hydraulic chamber 26 of the wheel cylinder 25 is decreased and increased, and the slip ratio of the wheel W is set to an appropriate magnitude determined by the friction coefficient of the road surface.

[0052] The normal braking control program represented by the flowchart of FIG. 7 is executed at each cycle time predetermined in the driving support ECU 96. Here, the normal time means a case where no abnormality is detected in the electric cylinder device 12 or the like. In step 1 (hereinafter simply abbreviated as S1; the same applies to other steps), the operating state of the brake operating member detected by the operation state detection device 104 is acquired. In S2, information representing the relative positional relationship between the host vehicle and surrounding objects acquired by the surrounding information acquisition device 106 is acquired. In S3, based on these, it is determined whether there is a braking request. During braking, it is determined that there is a braking request. If the determination is YES, in S4, the required braking force is acquired, and in S5, it is supplied to the brake ECU 86 of the corresponding wheel W.

[0053] The motor control program represented by the flowchart of FIG. 8 is executed at each cycle time predetermined in the brake ECU 86. In S11, the target hydraulic pressure Pt is acquired according to the required braking force, and the actual hydraulic pressure Ps, which is the measured value of the hydraulic pressure sensor 102, is acquired. In S12, it is determined whether the target hydraulic pressure Pt is 0. When the required braking force is not acquired, it is determined that the target hydraulic pressure Pt is 0. If the determination in S13 is NO, in S15, it is determined whether the actual hydraulic pressure Ps is greater than the target hydraulic pressure Pt. If the determination is YES, in S16, by controlling the electric motor 44, the electric piston member 42 is retracted. As a result, the volume of the volume change chamber 67 increases, and the hydraulic pressure in the wheel cylinder 25 decreases.

[0054] On the contrary, if the determination in S13 is NO, in S15, it is determined whether the actual hydraulic pressure Ps is greater than the target hydraulic pressure Pt. If the determination is YES, in S16, by controlling the electric motor 44, the electric piston member 42 is advanced against the elastic force of the return spring 68. Thereby, the volume of the volume change chamber 67 decreases, and the hydraulic pressure in the wheel cylinder 25 increases.

[0055] When the difference between the target hydraulic pressure Pt and the actual hydraulic pressure Ps is small and substantially the same, in S17, the position of the electric piston member 42 is held and the hydraulic pressure is held. When the determination in S12 is YES and the target hydraulic pressure Pt is 0, the electric piston member 42 is retracted to the retracted end by the control of the electric motor 44.

[0056] Also, in each of the brake ECUs 86, a slip suppression control program is executed. In S21, the slip ratio of each wheel W is acquired. The slip ratio is acquired based on the vehicle body speed and the wheel speed. The vehicle body speed can be acquired, for example, by communication between the brake ECUs 86FL, 96FR, 96RL, and 96RR. For example, each brake ECU 86 acquires the vehicle body speed Vh based on the wheel speed Vwa detected by the wheel speed sensor 100 connected thereto and the wheel speeds Vwb, Vwc, and Vwd received via the CAN 95. Then, based on this vehicle body speed Vh and the wheel speed Vwa detected by the wheel speed sensor 100 connected thereto, the slip state of the wheel W can be acquired. Since the change in the vehicle body speed Vh is gentle compared to the wheel speed Vw, a value acquired based on the information received via the CAN 95 can be used.

[0057] In S22, it is determined whether or not slip suppression control is in progress. If the determination is NO, in S23, for example, it is determined whether or not start conditions including that the slip ratio is excessive are satisfied. If the determination is YES, in S24, slip suppression control is started. Next, when this program is executed, since slip suppression control is in progress, in S25, it is determined whether or not end conditions including that the slip ratio has been suppressed are satisfied. If the determination is NO, in S26, slip suppression control is continuously performed. The target hydraulic pressure is acquired so that the slip ratio is suppressed, and the electric motor 44 is controlled so that the actual hydraulic pressure approaches the target hydraulic pressure. When the determination in S25 becomes YES during the repeated execution of S2, 22, 25, and 26, the slip suppression control ends.

[0058] Thus, in this embodiment, in each of the brake ECUs 86, slip suppression control is performed independently, such as obtaining a target hydraulic pressure based on the slip state of the wheel W. However, it is not essential to perform the slip suppression control independently. In the driving support ECU 96, a required braking force can be obtained and supplied to each brake ECU 86.

[0059] Also, in this embodiment, the presence or absence of an abnormality in each of the electric cylinder devices 12 is detected. For example, as described above, each of the brake ECUs 86 outputs the acquired vehicle body speed Vha to the CAN 95, and in each of the brake ECUs 86, for example, based on four vehicle body speeds (Vha, Vhb, Vhc, Vhd), it is determined whether there is an abnormal value among them. Among the four vehicle body speeds (Vha, Vhb, Vhc, Vhd), the average value of these <vh>When there are significantly different values for [the relevant parameter], that value can be regarded as an abnormal value, and it can be determined that the brake ECU86 that obtained the abnormal value is abnormal. Then, based on each of the determination results in each brake ECU86, the abnormal brake ECU86 is finally determined by a majority vote or the like. The final determination of the brake ECU86 that is abnormal, that is, the determination of the abnormal electric cylinder device 12, can be made in the driving support ECU96, or can be made in one of the plurality of brake ECUs86, etc. Also, in the driving support ECU96, the vehicle body speeds (Vha, Vhb, Vhc, Vhd) obtained in each of the brake ECUs86 are received, and based on these four vehicle body speeds (Vha, Vhb, Vhc, Vhd), an abnormal value is detected, and it can also be determined that the brake ECU86 that output the abnormal value is abnormal.

[0060] Note that the presence or absence of abnormality in each of the electric cylinder devices 12 can be detected based on the deviation between the actual hydraulic pressure, which is the hydraulic pressure detected by the hydraulic pressure sensor 102, and the target hydraulic pressure, or can be detected based on the relationship between the hydraulic pressure detected by the hydraulic pressure sensor 102 and the stroke of the electric piston member 42 obtained based on the detection value of the rotation speed sensor 94. Regardless of the detection method for the presence or absence of abnormality in the electric cylinder device 12, etc.

[0061] When it is detected that at least one of the four electric cylinder devices 12 is abnormal, the detected abnormal electric cylinder device 12 is stopped, and the normal electric cylinder device 12 is activated. Fig. 9 shows an example of a flowchart representing a braking control program in case of an abnormality. In S31, the presence or absence of any abnormality in each of the electric cylinder devices 12 is detected. In S32, it is determined whether or not at least one of the electric cylinder devices 12 is abnormal. If the determination is NO, then in S33, control of the normal electric cylinder device 12 is performed. As described above, it is controlled in accordance with the execution of the normal braking control program represented by the flowchart of Fig. 7 (for example, the electric motor 44 is controlled such that the hydraulic pressure detected by the hydraulic pressure sensor 102 approaches the target hydraulic pressure determined based on, for example, the relative positional relationship between a surrounding object and the host vehicle, the operation state of the brake operation member, etc.). Also, if the determination in S32 is YES, then in S34 and S35, the abnormal electric cylinder device 12 is stopped and the normal electric cylinder device 12 is controlled. For example, when it is detected that the electric cylinder device 12RL of the left rear wheel WRL is abnormal, the electric cylinder device 12RL of the left rear wheel WRL is stopped and the three normal electric cylinder devices, the electric cylinder devices 12FL, 12FR, and 12RR of the left front wheel WFL, the right front wheel WFR, and the right rear wheel WRR are actuated. For example, it is desirable that these electric cylinder devices 12FL, 12FR, and 12RR be controlled so as to suppress the yaw rate of the vehicle caused by the stop of the electric cylinder device 12 of the left rear wheel WRL. Also, the yaw rate can be suppressed by controlling the regenerative braking force by a regenerative braking device (not shown).

[0062] Thus, in this embodiment, since the first vehicle, which is a vehicle, is provided with four electric cylinder devices 12, even if an abnormality occurs in a part of the four electric cylinder devices 12, it is possible to generate hydraulic pressure in the wheel cylinder 25 by the operation of the remaining electric cylinder devices 12, and the hydraulic brake system can be continuously operated. Also, when a part of the four electric cylinder devices 12 fails, the hydraulic brake system can be continuously operated even if the brake operation member is not operated. Thus, the hydraulic brake system according to this embodiment is a fail-operable system.

[0063] For example, when the first vehicle is an autonomous vehicle, the driver may not be able to sense that a malfunction has occurred in a part of the electric cylinder device 12, and the part may malfunction, or the vehicle owner may neglect maintenance, resulting in a malfunction of a part of the electric cylinder device 12. Even in such cases, the present hydraulic brake system can continue to operate.

[0064] Moreover, since a power supply V is provided corresponding one-to-one to each of the electric cylinder devices 12, even when one of the four power supplies V malfunctions, the electric cylinder device 12 corresponding to the remaining power supply V can be operated.

[0065] Similarly, since a brake ECU 86 is provided corresponding one-to-one to each of the electric cylinder devices 12, even when one of the four brake ECUs 86 malfunctions, the remaining electric cylinder devices 12 can be operated. Note that the driving support ECU 96, the operation state detection device 104, the surrounding information acquisition device 106, etc. can also be configured redundantly.

[0066] As described above, even if an abnormality occurs in a part of the components of the hydraulic brake system, the hydraulic brake system that can continue to operate by other components is called a fail-operable hydraulic brake system. In that case, due to the probability of failure, etc., the hydraulic brake system is required to be provided with three or more mutually independent hydraulic sources (for example, including the electric cylinder device 12). On the other hand, in the present embodiment, since the hydraulic brake system includes the electric cylinder device 12 as four hydraulic sources, it can be said that the hydraulic brake system is fail-operable.

[0067] Further, in the hydraulic brake system according to the present embodiment, an electric cylinder device 12 is provided corresponding to each of the wheel cylinders 25, and the power consumption of each of the electric cylinder devices 12 is reduced. Therefore, although the number of electric motors 44 mounted on the vehicle increases, an increase in the overall power consumption of the vehicle can be suppressed, so that it becomes possible to mount four electric motors 44 on the first vehicle.

[0068] For example, in a vehicle (an example of the first vehicle) with a vehicle weight of 3.5 t to 8 t, a large braking force is required to stop the vehicle, and a large amount of working fluid is required for each of the wheel cylinders provided on the four wheels W on the front, rear, left, and right. Therefore, in the conventional hydraulic brake system, there have been problems such as the need to increase the size of the master cylinder, the electric booster, etc.

[0069] On the other hand, in the hydraulic brake system according to the present embodiment, an electric cylinder device 12 is provided corresponding to each of the wheel cylinders 25. In other words, in order to supply the required amount of working fluid in one wheel cylinder 25, it is not necessary to make each of the electric cylinder devices 12 large-sized. Further, as described above, the stroke of the electric piston member 42 can be increased (for example, 50 mm or more), and the pressure receiving area of the piston portion 47 can be decreased (for example, 30 mm or less). Therefore, the ratio of the pressure receiving area can be increased, and the axial force applied to the direct-acting conversion device 48 can be decreased, so that the power consumption of the electric motor 44 can be reduced. Therefore, four electric motors 44 can be provided without increasing the size of a battery (not shown) provided in the first vehicle.

[0070] Further, when the first vehicle is a commercial vehicle, in order to prevent defects in components of a hydraulic brake system such as a master cylinder, an electric booster, and a solenoid valve device including one or more solenoid valves, components were usually replaced regularly. In particular, since it was difficult to individually replace and assemble each solenoid valve of the solenoid valve device, etc., the entire solenoid valve device (in unit of a unit) might be replaced. Therefore, there were problems such as high maintenance costs and a large amount of waste being generated.

[0071] On the other hand, in this embodiment, instead of regularly replacing each entirety of the electric cylinder devices 12, they are disassembled, and parts that have become abnormal can be easily replaced. For example, rubber members such as the seal member 66 are more likely to deteriorate than other metal members, but only the seal member 66 can be replaced. As a result, the cost required for maintenance can be reduced, waste can be reduced, and effective use of resources can be achieved.

[0072] Also, when the vehicle is large and the capacity of the hydraulic brake 10 is large, since the initial hydraulic pressure is high and the diameter of the wheel side piston 27 is large, a large amount of working fluid needs to be supplied before it starts to work. On the other hand, if the diameter of the electric piston member 42 of the electric cylinder 12 is reduced, the stroke of the electric piston member 42 until it starts to work becomes longer, and a delay in operation occurs. In contrast, the electric motor 44 has a method called field weakening. By the method of field weakening, when supplying a current larger than the rated rotation speed to the electric motor 44 at the time of a weak reaction force until it starts to work, the rotation speed of the electric motor 44 is increased, and the forward speed of the electric piston member 42 is increased, so that the stroke can be immediately increased and the operation delay can be suppressed. Also, even when the electric cylinder device 12 has a structure (referred to as a fill-up structure) capable of supplying a large flow rate to the wheel cylinder 25 at the start of operation, similarly, the forward speed of the electric piston member 42 until it starts to work can be increased, and the operation delay can be suppressed.

[0073] As described above, in this embodiment, the hydraulic control device is configured by the wheel speed sensor 100, the hydraulic sensor 102, the operation state detection device 104, the surrounding information acquisition device 106, the driving support ECU 96, the brake ECU 86, and the like. The abnormality detection unit is configured by a part that stores S31 of the abnormal brake control program represented by the flowchart of FIG. 10 in the hydraulic control device, a part that executes it, and the like.

[0074] Note that the transmission and reception of information, the role sharing, etc. between the driving support ECU 96 and each brake ECU 86 are not limited to those in the above embodiment and can be arbitrarily set.

[0075] In addition, the vehicle equipped with the hydraulic brake system may be an autonomous vehicle, a by-wire manual driving vehicle (a vehicle in which the operation state of the brake operation member is detected by the operation state detection device 104 and the electric cylinder device 12 is controlled based on it), or a vehicle in which the manual driving state and the autonomous driving state can be switched. Furthermore, it can also be applied to a vehicle having four or more wheels.

[0076] In the above embodiment, the case where the electric cylinder device 12 is mounted on the first vehicle has been described, but it can be mounted on a second vehicle that is lighter than the first vehicle. In this hydraulic brake system, as shown in FIG. 4, among the hydraulic brakes 10 of the front, rear, left, and right wheels provided in the second vehicle, the hydraulic brakes 10FL and 10FR of the left and right front wheels WFL and WFR are respectively provided with electric cylinder devices 12FL and 12FR corresponding one-to-one via the liquid passages 74FL and 74FR, and the hydraulic brakes 10RL and 10RR of the left and right rear wheels WRL and WRR are commonly provided with one electric cylinder device 12R. The wheel cylinders 25 of the hydraulic brakes 10RL and 10RR of the left and right rear wheels WRL and WRR are connected by the liquid passage 74R, and the electric cylinder device 12R is provided in this liquid passage 74R. In addition, power supplies VFL, VFR, and VR are respectively provided corresponding one-to-one to each of the electric cylinder devices 12FL, 12FR, and 12R, and brake ECUs 86FL, 86FR, and 86R are provided.

[0077] Also, in slip suppression control (e.g., anti-lock control, traction control when the rear wheels WRL and WRR are drive wheels, etc.), the electric cylinder device 12R similarly increases or decreases the hydraulic pressure of the wheel cylinders 25RL and 25RR based on the wheel with the lower wheel speed among the left and right rear wheels WRL and WRR, in other words, the wheel with the higher slip ratio. Such slip suppression control is referred to as low select control. Thus, since the hydraulic brake system mounted on the second vehicle includes three electric cylinder devices 12, it can be said to be fail-operable.

[0078] Also, as shown in FIG. 5, the electric cylinder device 12 can also be mounted on a third vehicle that is lighter than the second vehicle. In this hydraulic brake system, one electric cylinder device 12F is commonly provided for the hydraulic brakes 10FL and 10FR of the left and right front wheels WFL and WFR, and one electric cylinder device 12R is commonly provided for the hydraulic brakes 10RL and 10RR of the left and right rear wheels WRL and WRR. Specifically, the wheel cylinders 25 of the hydraulic brakes 10FL and 10FR provided for the left and right front wheels WFL and WFR are respectively connected to a device 200F such as a front-wheel side solenoid valve via liquid passages 74FL and 74FR, and the electric cylinder device 12F is connected to the device 200F such as a front-wheel side solenoid valve. Also, the wheel cylinders 25 of the hydraulic brakes 10RL and 10RR provided for the left and right rear wheels WRL and WRR are respectively connected to a device 200R such as a rear-wheel side solenoid valve via liquid passages 74RL and 74RR, and the electric cylinder device 12R is connected to the device 200R such as a rear-wheel side solenoid valve.

[0079] In this embodiment, devices such as the front-wheel side solenoid valve 200F and the rear-wheel side solenoid valve 200R are hydraulically independent of each other, and are structured such that the influence caused by an abnormality in one of the front-wheel side solenoid valve device 200F and the rear-wheel side solenoid valve device 200R does not affect the other. Also, the solenoid valve device 200 is constituted by devices such as the front-wheel side solenoid valve device 200F and the rear-wheel side solenoid valve device 200R, and the solenoid valve device 200 includes a hydraulic pressure generating device 203 and the like. The hydraulic pressure generating device 203 can include, for example, pumps respectively provided in the front-wheel side solenoid valve device 200F and the rear-wheel side solenoid valve device 200R, and a common electric motor for driving these pumps. Power sources VF and VR are individually provided one-to-one to the electric cylinder devices 12F and 12R respectively, and a power source VE is provided to the solenoid valve device 200. Similarly, brake ECUs 86F and 86R mainly composed of computers are provided one-to-one to each of the electric cylinder devices 12F and 12R respectively, and a solenoid valve ECU 202 is provided one-to-one to the solenoid valve device 200.

[0080] Thus, this hydraulic brake system is a two-system fail-operable type including two electric cylinder devices 12F and 12R and one or more hydraulic pressure generating devices 203.

[0081] Furthermore, as shown in FIG. 6, the electric cylinder device 12 can be mounted on a fourth vehicle that is lighter in weight than the third vehicle. In this hydraulic brake system, one electric cylinder device 12A is commonly provided for the hydraulic brakes 10FL, 10FR, 10RL, and 10RR of the front, rear, left, and right wheels WFL, WFR, WRL, and WRR. One electric cylinder device 12A is connected to a device 210 such as a solenoid valve, and the wheel cylinders 25 of the four hydraulic brakes 10FL, 10FR, 10RL, and 10RR are respectively connected to the device 210 such as a solenoid valve via liquid passages 74FL, 74FR, 74RL, and 74RR. The hydraulic pressure generated by the electric cylinder device 12A is supplied to the wheel cylinders 25 of the four hydraulic brakes 10 via the device 210 such as a solenoid valve, and the hydraulic pressure of the four wheel cylinders 25 is individually controlled by the control of the device 210 such as a solenoid valve. Power sources VA and VE are respectively provided for each of the electric cylinder device 12 and the device 210 such as a solenoid valve, and a brake ECU 86A and a solenoid valve ECU 212 are provided.

[0082] Also, when the fourth vehicle shown in FIG. 6 is a vehicle that can be manually operated, a manual hydraulic source (for example, a master cylinder) 220 can be provided in parallel with the electric cylinder device 12. For example, the device 210 such as a solenoid valve is connected to both the manual hydraulic source 220 and the electric cylinder device 12. In that case, when the electric cylinder device 12 fails, hydraulic pressure is generated in the manual hydraulic source 220 by the operation of the brake operation member 222 and supplied to the wheel cylinder 25, so that hydraulic pressure can be generated in the hydraulic brake 10. Thus, in this hydraulic brake system, when the electric cylinder device 12 fails, the electric cylinder device 12 can be stopped, and the vehicle can be stopped by the manual operation of the brake operation member 222 by the driver. Such a hydraulic brake system can be referred to as a fail-safe system (which means that when an abnormality occurs, the operation of the electric cylinder device 12 is stopped and the vehicle is stopped by manual operation).

[0083] In this way, by changing the number of units installed in vehicles with different weights such as the first vehicle, the second vehicle, the third vehicle, the fourth vehicle, etc., the same electric cylinder device 12 can be used. In other words, the braking force required for each of the first vehicle, the second vehicle, the third vehicle, and the fourth vehicle can be applied by one or more common electric cylinder devices 12. It becomes possible to commonly use the electric cylinder device 12 for various types of vehicles, and as a whole, cost reduction can be achieved. In particular, by applying it to vehicles with small production volumes, cost reduction can be further achieved. For example, according to the size of each vehicle, the number of units sold varies greatly. If dedicated parts are developed only for vehicles with a small number of units sold, the development costs, mold costs, etc. will be divided among a small number of units, resulting in an increase in component costs. However, if both vehicles with a large number of units sold and those with a small number of units sold use the same electric cylinder 12, although the number is different, the cost of each electric cylinder 12 can be suppressed, and as a result, the overall cost can be controlled. Furthermore, by changing the number of electric cylinders 12 according to the presence or absence of autonomous driving, the difference in the number of operating units, etc., it is possible to change to fail-operable or fail-safe, and there is no need to develop them dedicatedly, so it is possible to suppress new cost-increasing factors.

[0084] Also, the electric cylinder device 12 has the same structure and can be commonly applied to various types of vehicles by changing its specifications, etc. It can be commonly applied to various types of vehicles without designing a new structure, that is, without having to design a new structural design. In other words, in this specification, commonly using the electric cylinder device 12 means "using the electric cylinder device 12 with the same structure", and the specifications such as the capacity of the electric motor 44, the shape of the electric piston member 42, the cylinder bore, etc. are not questioned.

[0085] For example, the magnitude of the axial force can be adjusted by changing the number of turns and the coil diameter of the coil of the electric motor 44 according to the size of the vehicle, the vehicle type, etc. Also, the maximum stroke of the electric piston member 42, etc. can be changed according to the capacity of the wheel cylinder 25 to which it is connected, etc.

[0086] In this way, by changing the specifications of the electric cylinder device 12, for example, in various types of vehicles, the hydraulic brake 10 and the electric cylinder device 12 can be provided in a one-to-one correspondence.

[0087] Further, the electric cylinder device 12 can be directly connected to the wheel cylinder 25 or connected to a device such as a solenoid valve. Furthermore, the electric cylinder device 12 can be provided in a one-to-one or many-to-one relationship with the wheel cylinder 25, and the number of electric cylinder devices 12 can be designed according to the required braking force. Also, since the electric cylinder device 12 can be connected to a liquid passage extending from the wheel cylinder of the hydraulic brake provided on the wheel W, the mounting position and the like can be determined relatively freely. Furthermore, the stroke of the electric piston member 42, the diameter of the electric piston member 42, etc. in each of the electric cylinder devices 12 can also be designed according to the required braking force. In this way, the electric cylinder device 12 has high versatility and is easy to use. Also, due to its high versatility, the electric cylinder device 12 or its components can be recycled, enabling effective utilization of resources.

[0088] Also, the structure of the electric cylinder device 12 is not limited. It is not essential to provide the electric motor 44 coaxially with the rod portion 46, and it can be provided in a parallel state. Furthermore, a speed reducer can also be provided between the electric motor 44 and the rod portion 46.

[0089] Furthermore, in the above embodiment, although the hydraulic control device includes the driving support ECU 96, the brake ECU 86 (, the solenoid valve ECUs 202, 210), etc., the structure of the hydraulic control device is not limited, and it can include one ECU, etc.

[0090] In addition, in the above-described embodiment, in this hydraulic brake system, although the control and slip suppression control in which the hydraulic pressure of the wheel cylinder 25 approaches the target hydraulic pressure determined based on the surrounding conditions and the operation state of the brake operation member have been described, the present invention is not limited to those controls, and various controls such as front-rear braking force distribution control can be performed.

[0091] In addition, the hydraulic brake 10 may be a disc brake or a drum brake, etc. The present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

Explanation of Reference Numerals

[0092] 10: Hydraulic brake 12: Electric cylinder device 25: Wheel cylinder 26: Hydraulic chamber 27: Wheel side piston 40: Housing 40f: Front housing 40r: Rear housing 42: Electric piston member 44: Electric motor 48: Linear motion conversion device 50: Reservoir 80: Screw member 82: Nut member 86: Brake ECU 96: Driving support ECU V: Power supply Patentable invention

[0093] (1) A hydraulic brake provided for each of a plurality of wheels of a vehicle, each of which suppresses the rotation of the wheel by the hydraulic pressure in the hydraulic chamber of the wheel cylinder, An electric cylinder device provided corresponding to one or more of the plurality of hydraulic brakes, respectively, A hydraulic brake system including: The plurality of electric cylinder devices each include a housing, a piston fitted to the housing in a liquid-tight and slidable manner, an electric motor as a drive source, a linear-rotary motion conversion device that performs conversion between the rotation of the electric motor and the linear movement of the piston, and a volume change chamber provided in front of the piston and connected to the hydraulic chamber of the wheel cylinder of the one or more hydraulic brakes.

[0094] The hydraulic brake and the electric cylinder device may be provided in a one-to-one correspondence or a two-to-one correspondence. However, in the hydraulic brake system described in this section, a plurality of electric cylinder devices are included.

[0095] (2) The hydraulic brake system according to item (1), wherein each of the plurality of electric cylinder devices includes a reservoir for storing the hydraulic fluid returned from the hydraulic chamber of the one or more wheel cylinders.

[0096] (3) In each of the plurality of electric cylinder devices, Two ports are provided in a portion of the housing surrounding the volume change chamber, spaced apart from each other in the axial direction of the piston. The reservoir is connected to a rear port located rearward in the direction in which the piston retracts, among the two ports. The hydraulic brake system according to item (2), wherein the rear port is in an open state when the piston is at the retracted end position, but is switched to a closed state as the piston advances.

[0097] The port is provided to open toward the volume change chamber.

[0098] (4) The hydraulic brake system according to item (3), wherein the hydraulic chamber of the wheel cylinder of the one or more hydraulic brakes is directly connected to a front port located forward in the direction in which the piston advances, among the two ports.

[0099] The front port is always in an open state, communicating the volume change chamber and the wheel cylinder. Also, the volume change chamber and the wheel cylinder are connected via a liquid passage, and there are cases where a solenoid valve or the like is provided in the liquid passage and cases where it is not provided.

[0100] (5) The hydraulic brake system includes a plurality of power sources. The hydraulic brake system according to any one of (1) to (4), wherein each of the plurality of power sources and each of the plurality of electric cylinder devices are provided in a one-to-one correspondence.

[0101] The plurality of power sources are preferably independent of each other.

[0102] (6) The hydraulic brake system includes a control unit mainly composed of a plurality of computers, The hydraulic brake system according to any one of (1) to (5), wherein each of the plurality of control units and each of the plurality of electric cylinder devices are provided in a one-to-one correspondence.

[0103] (7) The hydraulic brake system according to any one of (1) to (6), wherein each of the plurality of electric cylinder devices is provided in a one-to-one correspondence with each of the plurality of hydraulic brakes.

[0104] (8) The hydraulic brake system according to any one of (1) to (7), wherein the hydraulic brake system includes three or more electric cylinder devices as the plurality of electric cylinder devices.

[0105] For example, the vehicle includes four wheels as the plurality of wheels, The hydraulic brakes are respectively provided on the four wheels, One of the three or more electric cylinder devices as the plurality of electric cylinder devices is provided corresponding to one or two of the four hydraulic brakes, The hydraulic brake system can be such that two or more electric cylinder devices excluding the one electric cylinder device from the three or more electric cylinder devices are respectively provided in a one-to-one correspondence with three or two hydraulic brakes excluding the one or two hydraulic brakes connected to the one electric cylinder device from the four hydraulic brakes.

[0106] (9) The hydraulic brake system according to any one of items (1) to (8), including two electric cylinders as the plurality of electric cylinder devices and one or more hydraulic pressure generating devices having a structure different from that of the electric cylinder device.

[0107] The hydraulic pressure generating device can be, for example, a power type hydraulic pressure generating device such as a pump device (referring to a device that is not a manual hydraulic pressure generating device). The number of hydraulic pressure generating devices provided in the hydraulic brake system may be one or two.

[0108] For example, the vehicle includes four wheels located at the front, rear, left, and right. The hydraulic brakes are respectively provided corresponding to the four wheels located at the front, rear, left, and right. Each of the two electric cylinder devices as the plurality of electric cylinder devices is provided corresponding to one of the two hydraulic brakes provided for two of the four wheels respectively. A first electromagnetic valve, which is one or more electromagnetic valves, is provided between one of the two electric cylinder devices and the two hydraulic brakes provided corresponding thereto. A hydraulic brake system can be provided with one or more second electromagnetic valves different from the first electromagnetic valve between the other of the two electric cylinder devices and the two hydraulic brakes provided corresponding thereto. In the above embodiment, one of the front wheel side electromagnetic valve device and the rear wheel side electromagnetic valve device is constituted by one or more first electromagnetic valves, etc., and the other of the front wheel side electromagnetic valve device and the rear wheel side electromagnetic valve device is constituted by one or more second electromagnetic valves, etc.

[0109] (10) The hydraulic brake system includes a hydraulic control device that controls the hydraulic pressure in the hydraulic chambers of the wheel cylinders of the plurality of hydraulic brakes by respectively controlling the supply current to the electric motors of each of the plurality of electric cylinder devices. The hydraulic control device controls the supply current to the electric motor in each of the plurality of electric cylinder devices, moves the piston forward and backward, decreases and increases the volume of the volume change chamber, thereby increasing and decreasing the hydraulic pressure in the hydraulic chambers of the plurality of wheel cylinders. The hydraulic brake system according to any one of items (1) to (9).

[0110] (11) The hydraulic brake system includes a peripheral information acquisition device that acquires information on the periphery of the vehicle, and a wheel speed detection device provided corresponding to each of the plurality of wheels for detecting the rotational speed of each wheel and includes The hydraulic control device controls the supply current to the plurality of electric motors so that the hydraulic pressure of each of the plurality of wheel cylinders approaches a target hydraulic pressure determined based on at least the information on the periphery of the vehicle acquired by the peripheral information acquisition device, and controls the supply current to the plurality of electric motors so that the slip state of each of the plurality of wheels acquired based on the wheel speed of each of the plurality of wheels detected by the plurality of wheel speed detection devices is within an appropriate range determined by the friction coefficient of the road surface. The hydraulic brake system according to item (10).

[0111] (12) The hydraulic brake system includes an operation state detection device that detects the operation state of a brake operation member operable by a driver, a peripheral information acquisition device that acquires information on the periphery of the vehicle, and a wheel speed detection device provided corresponding to each of the plurality of wheels for detecting the rotational speed of each wheel and includes The hydraulic control device Based on at least one of the information around the vehicle acquired by the surrounding information acquisition device and the operation state of the brake operation member detected by the operation state detection device, the supply currents to the plurality of electric motors are respectively controlled so that the hydraulic pressure of each of the plurality of wheel cylinders approaches the target hydraulic pressure, and The hydraulic brake system according to item (10), wherein the supply currents to the plurality of electric motors are respectively controlled so that the slip state of each of the plurality of wheels acquired based on the wheel speed of each of the plurality of wheels detected by the plurality of wheel speed detection devices is within an appropriate range determined by the friction coefficient of the road surface.

[0112] When the vehicle is an autonomous vehicle and does not include a brake operation member operable by a driver, the target hydraulic pressure is determined based on the surrounding information acquired by the surrounding information acquisition device. However, when the vehicle includes a brake operation member, the target hydraulic pressure is acquired in consideration of the operation state of the brake operation member. For example, the target hydraulic pressure can be acquired based on at least one of the brake operation state and the surrounding information.

[0113] (12) The hydraulic pressure control device includes an abnormality detection unit that detects the presence or absence of an abnormality in each of the plurality of electric cylinder devices. When the abnormality detection unit detects that one or more of the plurality of electric cylinder devices are abnormal, the one or more electric cylinder devices detected as abnormal are stopped, and the one or more electric cylinder devices excluding the one or more electric cylinder devices detected as abnormal from the plurality of electric cylinder devices are controlled. The hydraulic brake system according to item (10) or (11).

[0114] In the hydraulic brake system described in this item, each of the one or more electric cylinder devices excluding the one or more electric cylinder devices detected as abnormal from the plurality of electric cylinder devices can be controlled in an independent state from each other.

[0115] (13) The housing includes a first housing that houses the electric motor, and a second housing in which the piston is fitted in a liquid-tight and slidable manner. The hydraulic brake system according to any one of items (1) to (12) in which the first housing and the second housing are separably assembled.

[0116] The first housing and the second housing can be coupled by a coupling device including, for example, a screw member and a nut member. Therefore, by removing the nut member, the housing can be separated into the first housing and the second housing, and the electric motor, the piston, the linear-rotary motion conversion device, etc. can be removed respectively. The first housing corresponds to the rear housing 40r, and the second housing corresponds to the front housing 40f. The first housing 40r and the second housing 40f are coupled by a coupling device including, for example, a screw member 80 and a nut member 82.

[0117] Further, a cylinder bore is provided in the second housing, and the cylinder bore can have an elongated shape. For example, the ratio of the diameter to the length (diameter / length) can be made smaller than 0.6.

[0118] (14) The hydraulic brake system does not include a manual hydraulic source that generates hydraulic pressure due to the operation of a brake operation member by the driver, and a pump-type hydraulic source that includes a pump device and generates hydraulic pressure due to the operation of the pump device. The hydraulic brake system according to any one of items (1) to (13).

[0119] No manual hydraulic source, pump-type hydraulic source, etc. are connected to the electric cylinder device.

[0120] (15) The hydraulic brake system according to any one of items (1) to (14) in which no solenoid valve that is operated by applying a voltage to the solenoid is provided between the electric cylinder device and the hydraulic brake.< / vh>

Claims

【Claim 1】 A hydraulic brake provided for each of a plurality of vehicle wheels, and configured to suppress rotation of the wheel by hydraulic pressure in a hydraulic chamber of a wheel cylinder, respectively; A hydraulic brake system including electric cylinder devices respectively provided corresponding to each of the plurality of hydraulic brakes, and power supplies respectively provided corresponding to each of the plurality of electric cylinder devices, wherein each of the plurality of electric cylinder devices includes a housing, a piston fitted to the housing in a liquid-tight and slidable manner, an electric motor as a drive source, a linear-rotary motion conversion device configured to convert rotation of the electric motor into linear movement of the piston, and a volume change chamber provided in front of the piston and connected to the hydraulic chamber of the wheel cylinder of the hydraulic brake, wherein four or more electric cylinder devices are provided, and four or more power supplies are provided, wherein each of the four or more electric cylinder devices is provided corresponding to each of four or more of the hydraulic brakes in a one-to-one correspondence, wherein no electromagnetic valve that is actuated by application of voltage to a solenoid is provided on the downstream side of each of the four or more electric cylinder devices, wherein the four or more electric cylinder devices are hydraulically independent of each other, the hydraulic brake system does not include a manual hydraulic source configured to generate hydraulic pressure due to an operation of a brake operation member by a driver and supply the hydraulic pressure to one or more of the four or more wheel cylinders, but includes an operation state detection device configured to detect an operation state of a brake operation member operable by the driver, a peripheral information acquisition device configured to acquire information around the vehicle, wheel speed detection devices respectively provided corresponding to each of the four or more wheels and configured to detect a rotational speed of the wheel, and a hydraulic pressure control device configured to control hydraulic pressure in the hydraulic chambers of the wheel cylinders of the four or more hydraulic brakes by controlling supply currents to the electric motors of each of the four or more electric cylinder devices, respectively, comprising wherein the hydraulic pressure control device (a) controls supply currents to each of the four or more electric motors such that hydraulic pressure in each of the four or more wheel cylinders approaches a target hydraulic pressure determined based on at least one of the information around the vehicle acquired by the peripheral information acquisition device and the operation state of the brake operation member detected by the operation state detection device, and Means for controlling the supply current to each of the four or more electric motors such that the slip state of each of the four or more wheels, obtained based on the wheel speed of each of the four or more wheels detected by the four or more wheel speed detection devices, is within an appropriate range determined by the friction coefficient of the road surface, respectively. (b) A hydraulic brake system including an abnormality detection unit that detects the presence or absence of an abnormality in each of the four or more electric cylinder devices, and when the abnormality detection unit detects that one or more of the four or more electric cylinder devices are abnormal, stopping the one or more electric cylinder devices detected as being abnormal, and controlling one or more electric cylinder devices excluding the one or more electric cylinder devices detected as being abnormal from the four or more electric cylinder devices. **Claim 2** The hydraulic brake system according to claim 1, wherein each of the four or more electric cylinder devices includes a reservoir for storing the hydraulic fluid returned from the hydraulic chamber of the wheel cylinder.

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