Hydraulic pressure generator

Abstract

To suppress effect of axis deviation in a hydraulic pressure generator having a bottomed cylindrical-shaped piston.SOLUTION: A hydraulic pressure generator comprises: an electric motor that outputs a rotational power; a conversion mechanism (GH) that outputs the rotational power to be inputted to a rotary member (BK) as a linear power (Fn) of a linear motion member (BD), and in which the linear motion member (BD) is disposed to cover the rotary member (BK); a bottomed cylindrical-shaped piston that is inserted into a cylinder (CC) formed in a housing (HG) holding the conversion mechanism (GH), and increases a hydraulic pressure (Pc) of the cylinder (CC) by being moved with the linear power (Fn); a rotation stopping member that is fixed to the housing (HG) and prevents rotational motion of the linear motion member (BD); and an intermediate member (BE) that is located between the piston (NC) and the linear motion member (BD), and presses the piston (NC) in a slidable state.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a hydraulic pressure generating device. [Background technology]

[0002] Patent Document 1 describes that in order to ensure stable contact of the screw with the piston, "in an electric brake device that generates brake fluid pressure by driving a second slave piston 88a in the axial direction with the driving force of a motor, a driving force transmission mechanism 74 for transmitting the driving force of the motor includes a nut 80c that rotates by receiving the rotational driving force of the motor, and a ball screw shaft 80a that is engaged with the nut 80c and is provided so as to be movable in the axial direction and that contacts the second slave piston 88a, and a wear reduction means is provided for reducing wear at the contact portion between the ball screw shaft 80a and the second slave piston 88a." Specifically, the wear reduction means forms the contact surface of the piston with the screw in a flat shape, while forming the tip of the screw on the piston side in a convex curved shape.

[0003] Patent Document 2 describes the power transmission from the electric motor 2 to the piston 5 as follows: The planetary gear 3 rotates and drives the nut 8 of the worm gear 4, and the nut 8 displaces the spindle 9 of the worm gear 4. The end of the spindle 9 is connected in an axially fixed manner by a pin 10. The pin 10 is pressed into a hole in the piston bottom 11 of the piston 5. The pin 10 of the spindle 9 has a knurling including grooves parallel to the axial direction. The piston 5 displaces together with the spindle 9. A cylinder pin 13 is inserted into the cylinder 7 to prevent the piston 5 from rotating in the cylinder 7.

[0004] In the device of Patent Document 2, the piston 5 has a cup shape (one end of the cylindrical portion is open and the other end is closed at the bottom, also called a "bottomed cylindrical shape"). With this shape, the power transmission mechanism can be housed inside the cylindrical portion, so the axial dimension of the device can be shortened.

[0005] Incidentally, in order to convert the rotational power of an electric motor into linear power, the relative linear motion along the axial direction between the rotating member and the linear moving member is permitted, but the relative rotational motion around the axis must be constrained. Constraining the rotational motion is called "rotation stopper (rotation prevention)," and the member that performs this function is called "rotation stopper member." In the device of Patent Document 2, the spindle 9, which is a linear moving member, is disposed inside the nut 8, which is a rotating member. For this reason, the piston 5 and the spindle 9 are fixed so that they can move together, and the relative rotational motion of the piston 5 is constrained by the cylinder pin 13, which is a rotation stopper member.

[0006] The suppression of the effects of axial misalignment as described in Patent Document 1 is achieved by sliding between the piston and the linearly moving member. However, in the device of Patent Document 2, the piston and the linearly moving member are fixed, so it is not possible to provide a mechanism for suppressing the effects of axial misalignment between the piston and the linearly moving member. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-214068 A [Patent Document 2] US Patent Application Publication No. 2021 / 0122342 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above problems, an object of the present invention is to provide a hydraulic pressure generating device having a cylindrical piston with a bottom, in which the influence of axial misalignment can be suppressed. [Means for solving the problem]

[0009] The hydraulic pressure generating device (PS) of the present invention comprises an electric motor (MT) that outputs a rotational power (Tm), a conversion mechanism (GH) that outputs the rotational power (Tm) input to a rotating member (BK) as a linear power (Fn) of a linear moving member (BD) and is arranged so that the linear moving member (BD) covers the rotating member (BK), a piston (NC) having a bottomed cylindrical shape and inserted into a cylinder (CC) formed in a housing (HG) that holds the conversion mechanism (GH) and increases the hydraulic pressure (Pc) of the cylinder (CC) by moving due to the linear power (Fn), a rotation prevention member (MD) that is fixed to the housing (HG) and prevents the rotational motion of the linear moving member (BD), and an intermediate member (BE) that is positioned between the piston (NC) and the linear moving member (BD) and presses the piston (NC) in a slidable state. For example, the intermediate member (BE) presses the bottom surface (Mtn) of the piston (NC) with a convex pressing surface (Mpe), and the pressing surface (Mpe) can slide along the bottom surface (Mtn). Furthermore, the intermediate member (BE) is pressed by the linear motion member (BD) in a slidable state.

[0010] In the hydraulic pressure generating unit PS, the linear motion member BD is disposed outside the rotating member BK, and therefore the rotational motion of the linear motion member BD can be prevented by the anti-rotation member MD fixed to the housing HG. Even if a control piston NC having a cylindrical shape with a bottom is employed, the control piston NC and the linear motion member BD can be separated. Therefore, the influence of the axial misalignment is compensated for by the intermediate member BE provided between the control piston NC and the linear motion member BD. Furthermore, the end face Mqe of the intermediate member BE pressed by the linear motion member BD and the end face Mpd of the linear motion member BD pressing the intermediate member BE can slide against each other, improving the effect of compensating for the influence of the axial misalignment. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram for explaining the overall configuration of a braking control device SC. [Diagram 2] FIG. 2 is a partial cross-sectional view for explaining an embodiment of a liquid pressure generating unit PS. [Diagram 3]FIG. 11 is a partial cross-sectional view for explaining axial misalignment compensation by an intermediate member BE and the like. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <Symbols for components, etc. and suffixes at the end of the symbols> In the following description, components, calculation processes, signals, characteristics, and values ​​with the same symbol, such as "CW", have the same function. The suffixes "f" and "r" at the end of the symbol for each wheel are generic symbols that indicate whether it is related to the front or rear wheel system. For example, the wheel cylinder CW provided on each wheel is written as "front wheel cylinder CWf, rear wheel cylinder CWr". Furthermore, the suffixes "f" and "r" at the end of the symbol may be omitted. When the suffixes "f" and "r" are omitted, each symbol represents its generic name. For example, "CW" is a generic name for wheel cylinders provided on the front and rear wheels of a vehicle. Furthermore, "CW" as a generic name can also be written as "CW (= CWf, CWr)".

[0013] The first actuator YA of the first braking unit SA, the second actuator YB of the second braking unit SB, and the wheel cylinder CW are connected by a fluid path (communication path HS). Furthermore, in the first and second actuators YA and YB, various components (PS, etc.) are connected by fluid paths. Here, the "fluid path" is a path for moving the brake fluid BF (working fluid), and corresponds to piping, flow paths in the actuators, hoses, etc. In the following explanation, the communication path HS, reservoir path HR, input path HN, servo path HU, supply path HH, etc. are fluid paths.

[0014] <Vehicle Brake Control Device SC> The overall configuration of the brake control device SC including the hydraulic pressure generating unit PS will be described with reference to the schematic diagram of Figure 1. For example, the brake control device SC is applied to a hybrid vehicle equipped with an electric motor for driving, or an electric vehicle.

[0015] The vehicle is equipped with a regenerative device KG. The regenerative device KG is composed of a generator GN for energy regeneration (also called an "electric motor / generator" or a "regenerative generator"), a control unit EG for the regenerative device KG (also called a "regenerative controller"), and a regenerative storage battery (not shown). The regenerative generator GN also serves as an electric motor for driving. In regenerative braking, the electric motor / generator GN operates as a generator, and the generated electric power is stored in the regenerative storage battery via the regenerative controller EG. At this time, a regenerative braking force Fg acts on the wheels. For example, the regenerative device KG is provided on the front wheels WHf, and a regenerative braking force Fg is generated on the front wheels WHf.

[0016] The front and rear wheels WHf, WHr of the vehicle are provided with braking devices SX (=SXf, SXr). The braking devices SX are composed of a brake caliper, a friction member (e.g., brake pad), and a rotating member KT (e.g., brake disc). The brake caliper (not shown) is provided with a wheel cylinder CW (=CWf, CWr). A hydraulic pressure Pw (referred to as "wheel pressure") in the wheel cylinder CW presses the friction member (not shown) against the rotating member KT (=KTf, KTr) fixed to each wheel WH, thereby applying a braking torque Tb to the wheel WH. As a result, a hydraulic braking force Fp is generated in the wheel WH.

[0017] The vehicle is equipped with a brake operating member BP and various sensors (SP, etc.). The brake operating member BP (e.g., a brake pedal) is an operating member for the driver to decelerate the vehicle. The vehicle is provided with an operation displacement sensor SP that detects an operation displacement Sp of the brake operating member BP. The operation displacement Sp is one of state quantities (state variables) that indicate the operation amount of the brake operating member BP. In addition to the operation displacement sensor SP, a hydraulic pressure Pn (referred to as "input pressure") in an input chamber Rn (described later) is adopted as another state quantity that indicates the braking operation amount. The input pressure Pn is detected by an input pressure sensor PN. The operation displacement Sp, the input pressure Pn, etc. are collectively referred to as the "braking operation amount Ba." Moreover, a sensor that detects the braking operation amount Ba, such as the operation displacement sensor SP or the input pressure sensor PN, is referred to as the "braking operation amount sensor BA."

[0018] The vehicle is equipped with a brake control device SC. The brake control device SC employs a so-called front and rear type (also called "type II") brake system as two systems. The brake control device SC adjusts the actual wheel pressure Pw of each wheel cylinder CW. The brake control device SC is composed of two brake units SA and SB.

[0019] <First braking unit SA> The first braking unit SA adjusts the hydraulic pressures Pwf, Pwr (front and rear wheel pressures) of the front and rear wheel cylinders CWf, CWr in response to the operation of a brake operating member BP (brake pedal). The first braking unit SA is composed of a first actuator YA and a first controller EA.

[0020] <First actuator YA> The first actuator YA is composed of an apply unit AP, a hydraulic pressure generating unit PS, and an input unit NR.

[0021] [Apply Unit AP] In response to the operation of the brake operating member BP, a supply pressure Pm is output from the apply unit AP. The apply unit AP is composed of a single-type master cylinder CM and a master piston NM.

[0022] A master piston NM is inserted into the single-type master cylinder CM. The interior of the master cylinder CM is divided into three hydraulic chambers Rm, Ru, and Rs by the master piston NM. The master chamber Rm is formed by the bottom of the master cylinder CM and the master piston NM. Furthermore, the interior of the master cylinder CM is divided into a servo chamber Ru and a reaction chamber Rs by a flange portion Tu of the master piston NM. Here, the pressure-receiving area rm of the master chamber Rm and the pressure-receiving area ru of the servo chamber Ru are set to be equal.

[0023] When braking is not being performed, the master piston NM is in the most retreated position (i.e., the position where the volume of the master chamber Rm is maximum). In this state, the master chamber Rm of the master cylinder CM is in communication with the master reservoir RV. Brake fluid BF is stored inside the master reservoir RV (also called the "atmospheric pressure reservoir"). When the brake operating member BP is operated, the master piston NM is moved in the forward direction Da (the direction in which the volume of the master chamber Rm decreases). This movement blocks communication between the master chamber Rm and the master reservoir RV. Then, when the master piston NM is further moved in the forward direction Da, the supply pressure Pm (the internal pressure of the master chamber Rm, also called the "master pressure") is increased from "0 (atmospheric pressure)". As a result, the brake fluid BF pressurized to the supply pressure Pm is output (pressurized and fed) from the master cylinder CM (particularly the master chamber Rm).

[0024] [Liquid pressure generating unit PS] The hydraulic pressure generating unit PS (also called the "hydraulic pressure generating device") uses an electric motor MT as its power source to generate front and rear wheel pressures Pwf, Pwr. The front and rear wheel pressures Pwf, Pwr are adjusted by a servo pressure Pc generated by the electric motor MT. Specifically, the hydraulic pressure generating unit PS and the servo chamber Ru are connected via a servo path HU (fluid path). The hydraulic pressure generating unit PS and the rear wheel cylinder CWr are connected via a rear wheel communication path HSR (fluid path). Furthermore, the hydraulic pressure generating unit PS is connected to a master reservoir RV via a supply path HH (fluid path) so that the brake fluid BF can be replenished when there is a shortage of brake fluid BF in the hydraulic pressure generating unit PS.

[0025] When the hydraulic pressure generating unit PS is operating (i.e., during braking), the supply path HH is cut off. This puts the hydraulic pressure generating unit PS and the master reservoir RV in a non-communicative state. In the front wheel braking system, the servo pressure Pc is supplied to the servo chamber Ru to generate a supply pressure Pm (master pressure). The supply pressure Pm generates a hydraulic pressure Pwf (front wheel pressure) in the front wheel cylinder CWf. Meanwhile, in the rear wheel braking system, the servo pressure Pc is directly supplied to the rear wheel cylinder CWr to generate a hydraulic pressure Pwr (rear wheel pressure) in the rear wheel cylinder CWr. The hydraulic pressure generating unit PS is provided with a servo pressure sensor PC to detect the servo pressure Pc. Details of the hydraulic pressure generating unit PS will be described later.

[0026] [Input unit NR] The input unit NR realizes regenerative cooperative control. "Regenerative cooperative control" cooperates hydraulic braking force Fp (braking force due to wheel pressure Pw) and regenerative braking force Fg (braking force due to regenerative generator GN) so that the kinetic energy of the vehicle can be efficiently recovered as electrical energy during braking. In regenerative cooperative control, the brake operating member BP is operated, but a state is created in which no wheel pressure Pw is generated. The input unit NR is composed of an input cylinder CN, an input piston NN, a first control valve VA, a second control valve VB, a stroke simulator SS, and an input pressure sensor PN.

[0027] The input cylinder CN is fixed to the master cylinder CM. An input piston NN is inserted into the input cylinder CN. The input piston NN is mechanically connected to a brake operating member BP (brake pedal) so as to move in conjunction with the movement of the brake operating member BP. There is a gap Ks (also called the "separation distance") between the end face of the input piston NN and the end face of the master piston NM. The separation distance Ks is adjusted by the servo pressure Pc, thereby achieving regenerative cooperative control.

[0028] The input chamber Rn of the input unit NR is connected to the reaction chamber Rs of the apply unit AP via an input path HN (fluid path). A normally closed first control valve VA is provided in the input path HN. The input path HN is connected to a master reservoir RV between the first control valve VA and the reaction chamber Rs via a reservoir path HR (fluid path). A normally open second control valve VB is provided in the reservoir path HR. An on-off type solenoid valve is used for the first and second control valves VA and VB. A stroke simulator SS is connected to the input path HN between the first control valve VA and the reaction chamber Rs.

[0029] When no power is supplied to the first and second control valves VA, VB, the first control valve VA is closed and the second control valve VB is open. When the first control valve VA is closed, the input chamber Rn is sealed and fluid locked. This causes the master piston NM to be displaced integrally with the brake operating member BP. When the second control valve VB is opened, the stroke simulator SS and the reaction chamber Rs are connected to the master reservoir RV.

[0030] When power is supplied (electricity is fed) to the first and second control valves VA, VB, the first control valve VA is opened and the second control valve VB is closed. This allows the master piston NM to be displaced separately from the brake operating member BP. At this time, the input chamber Rn is connected to the stroke simulator SS, so that the operating force of the brake operating member BP is generated by the stroke simulator SS. In order to detect the input pressure Pn, an input pressure sensor PN is provided in the input path HN between the input chamber Rn and the first control valve VA. The input pressure Pn is also the hydraulic pressure in the stroke simulator SS.

[0031] <First controller EA> The first actuator YA is controlled by a first controller EA. The first controller EA is composed of a microprocessor MP and a drive circuit DR. The first controller EA is connected to a communication bus BS so that signals (detection values, calculation values, control flags, etc.) can be shared between the first controller EA and other controllers (EB, EG, etc.).

[0032] The first controller EA directly receives various signals such as the operation displacement Sp (detection value of the operation displacement sensor SP), the input pressure Pn (detection value of the input pressure sensor PN), the servo pressure Pc (detection value of the servo pressure sensor PC), and the motor rotation angle Ka (detection value of the rotation angle sensor KA). Furthermore, the first controller EA receives various signals such as the supply pressure Pm and the limit regenerative braking force Fx from the communication bus BS. The first controller EA also outputs a target regenerative braking force Fh (target value of the regenerative braking force Fg) to the communication bus BS. The regenerative controller EG controls the regenerative braking force Fg (actual value) based on the target regenerative braking force Fh (target value) acquired from the communication bus BS.

[0033] An algorithm for pressure regulation control is programmed in the first controller EA (particularly, the microprocessor MP). The "pressure regulation control" is a control for adjusting the wheel pressure Pw (=Pwf, Pwr) and includes regenerative cooperative control. The pressure regulation control is executed based on the above-mentioned various signals (Sp, Pc, etc.). Based on the pressure regulation control algorithm, the drive circuit DR drives the electric motor MT and various solenoid valves (VA, etc.). The drive circuit DR includes an H-bridge circuit (also called an "inverter circuit") formed of switching elements (e.g., MOS-FET) to drive the electric motor MT. The drive circuit DR also includes switching elements to drive the various solenoid valves. In addition, the drive circuit DR includes a motor current sensor (not shown) that detects a supply current Im (also called a "motor current") to the electric motor MT. The electric motor MT is provided with a rotation angle sensor KA to detect a position Ka (rotation angle) of the motor shaft SM.

[0034] In the first controller EA, the drive signals Va, Vb of the first and second control valves VA, VB and the drive signal Mt of the electric motor MT are calculated. Then, the switching elements are driven in response to various drive signals (Mt, etc.). Specifically, in the control of the solenoid valve, power is supplied to the first and second control valves VA, VB based on the drive signals Va, Vb. As a result, the first control valve VA is opened and the second control valve VB is closed. In the control of the electric motor MT, a target pressure Pt is calculated based on the operation displacement Sp, etc. The "target pressure Pt" is a target value corresponding to the servo pressure Pc (actual value). Then, in the first controller EA, in response to the target pressure Pt and the drive signal Mt calculated based on the servo pressure Pc, the electric motor MT is controlled so that the servo pressure Pc (actual value) approaches and coincides with the target pressure Pt (target value).

[0035] <Second braking unit SB> A second brake unit SB is provided between the first brake unit SA and the wheel cylinder CW. The second brake unit SB executes antilock brake control, traction control, anti-skid control, etc. In the brake system related to the front wheels WHf (i.e., the front wheel connecting path HSf), a supply pressure Pm is supplied from the master cylinder CM to the second brake unit SB. On the other hand, in the brake system related to the rear wheels WHr (i.e., the rear wheel connecting path HSr), a servo pressure Pc is directly supplied from the hydraulic pressure generating unit PS to the second brake unit SB. In the second brake unit SB, the supply pressure Pm and the servo pressure Pc are adjusted (increased or decreased) and output as hydraulic pressures Pwf, Pwr (front and rear wheel pressures) of the front and rear wheel cylinders CWf, CWr. The configuration of the second brake unit SB is well known, so a description thereof will be omitted.

[0036] Normally, when the regenerative cooperative control is executed, the operation of the second actuator YB (electric motor, fluid pump, solenoid valve, etc.) is stopped. Therefore, the supply pressure Pm is outputted from the second braking unit SB as the front wheel pressure Pwf, and the servo pressure Pc is outputted as the rear wheel pressure Pwr.

[0037] <Embodiment of the liquid pressure generating unit PS> An embodiment of the hydraulic pressure generating unit PS will be described with reference to the partial cross-sectional view of Fig. 2. In the hydraulic pressure generating unit PS (hydraulic pressure generating device), an electric motor MT is used as a pressure source (also called a "power source") to generate a servo pressure Pc. The wheel pressure Pw (=Pwf, Pwr) is adjusted by the servo pressure Pc.

[0038] <Shape and direction of movement of components> First, the directions related to the shapes, movements, etc. of the elements that constitute the hydraulic pressure generating unit PS are defined. In the hydraulic pressure generating unit PS, when no axial misalignment occurs, the rotation axis Jm of the electric motor MT (particularly the motor shaft SM), the rotation axis Jk of the rotating member BK, the central axis Jn of the control piston NC, the central axis Jc of the control cylinder CC, and the central axis Je of the intermediate member BE are aligned on a straight line. The direction along the axes Jm, Jk, Jn, Jc, and Je (i.e., the parallel direction) is referred to as the "axial direction Hj". In contrast, the direction perpendicular to the axes Jm, Jk, Jn, Jc, and Je is referred to as the "radial direction Hk". Therefore, the radial direction Hk is perpendicular to the axial direction Hj.

[0039] In a member (NC, BE, BD, etc.) that is movable along the axial direction Hj, the direction approaching the bottom surface Mbc of the control cylinder CC is called the "forward direction Ha." Conversely, the direction moving away from the bottom surface Mbc of the control cylinder CC is called the "reverse direction Hb." Therefore, when the control piston NC is moved in the forward direction Ha, the volume of the control chamber Rc is decreased and its internal pressure Pc (servo pressure) is increased. In contrast, when the control piston NC is moved in the reverse direction Hb, the volume of the control chamber Rc is increased and the servo pressure Pc is decreased.

[0040] In the relationship between the rotational motion of the electric motor MT and the linear motion of the linear member BD (and thus the control piston NC), the forward rotation direction Hs of the electric motor MT corresponds to the forward direction Ha of the linear member BD. Therefore, the rotational motion of the electric motor MT in the reverse direction Hg corresponds to the backward direction Hb of the linear member BD. In other words, when the electric motor MT rotates in the forward rotation direction Hs, the linear member BD moves in the forward direction Ha. This reduces the volume of the control chamber Rc and increases the servo pressure Pc. Conversely, when the electric motor MT rotates in the reverse direction Hg, the linear member BD moves in the backward direction Hb. This increases the volume of the control chamber Rc and decreases the servo pressure Pc.

[0041] <Configuration of the hydraulic pressure generating unit PS> The hydraulic pressure generating unit PS is made up of a housing HG, an electric motor MT, a rotation angle sensor KA, a reducer GS, a conversion mechanism GH, a rotation prevention member MD, a control piston NC, and an intermediate member BE.

[0042] The housing HG holds the components (MT, GS, etc.) that make up the hydraulic pressure generating unit PS. The housing HG is divided into multiple parts so that the components can be assembled. For example, the housing HG is divided into a cylinder housing HGc and a motor housing HGm. The motor housing HGm and the cylinder housing HGc are assembled together and ultimately integrated into the housing HG. In other words, the housing HG is a collective term for the cylinder housing HGc and the motor housing HGm.

[0043] Furthermore, the housing HG may be integrated with the first controller EA. Specifically, the first controller EA is composed of a control board on which the microprocessor MP and the drive circuit DR are mounted, and a controller housing (not shown) that houses the control board. The controller housing is then assembled and integrated with the housing HG. The housing HG (particularly, the cylinder housing HGc) holds the reducer GS and the conversion mechanism GH. The housing HG (particularly, the motor housing HGm) holds the electric motor MT.

[0044] A control cylinder CC (corresponding to a "cylinder") is formed in the housing HG (particularly, the cylinder housing HGc). A control piston NC (corresponding to a "piston") is inserted into the control cylinder CC. The control cylinder CC and the control piston NC form a control chamber Rc (hydraulic chamber). A discharge portion Au is provided in the control cylinder CC (particularly, the control chamber Rc). The discharge portion Au is connected to the servo path HU and the rear wheel communication path HSr. That is, the control chamber Rc is connected to the servo chamber Ru and the rear wheel cylinder CWr. As a result, the servo pressure Pc is supplied (output) to the servo chamber Ru and the rear wheel cylinder CWr.

[0045] The electric motor MT is a power source (pressurizing source) for generating the servo pressure Pc (hydraulic pressure in the control cylinder CC). Here, "power" refers to the energy required to move the movable members (BK, BD, etc.) in the hydraulic pressure generating unit PS. For example, power is defined as a physical quantity, namely, energy per unit time (also called "power"). The electric motor MT outputs a rotational power Tm (also called "first rotational power"). The rotational power Tm of the electric motor MT is obtained by multiplying the axial torque of the electric motor MT by the rotational speed of the electric motor MT (particularly, the motor shaft SM). The linear power Fn of the linearly moving member BD (described later) is obtained by multiplying the thrust of the linearly moving member BD (force acting in the axial direction Hj) by the linear speed of the linearly moving member BD (speed in the axial direction Hj).

[0046] A three-phase brushless motor is adopted as the electric motor MT. The electric motor MT is mounted in a motor housing HGm. The electric motor MT includes a motor coil CL, a motor shaft SM, and a rotation angle sensor KA. The motor coil CL (also simply referred to as a "coil (winding)") is fixed in the motor housing HGm. The motor coil CL is also referred to as a "stator." A motor line Lm is connected to the motor coil CL. Power is supplied to the motor coil CL from a first controller EA (particularly, a drive circuit DR) via the motor line Lm.

[0047] The motor shaft SM (also simply referred to as the "shaft") is rotatably supported relative to the motor housing HGm (i.e., the motor coil CL) by a bearing BB fixed within the motor housing HGm. A motor magnet Mm (permanent magnet) is fixed to the outer periphery of the shaft SM of the electric motor MT. For example, the motor magnet Mm is affixed to the motor shaft SM by adhesive or the like. The motor shaft SM is also referred to as the "rotor."

[0048] In the three-phase brushless motor MT, the magnetic pole position of the rotor SM (i.e., the rotation angle relative to the stator CL) is detected, and the current Im (motor current) flowing through the motor coil CL is switched. Here, the motor current Im is a general term for the currents flowing through the U phase, V phase, and W phase. The three-phase motor current Im relating to the U phase, V phase, and W phase is switched based on the rotation position Ka (also called the "rotation angle") of the motor shaft SM. In the first controller EA, the switching elements of the drive circuit DR (inverter circuit) are driven according to the rotation angle Ka. As a result, the motor current Im flowing through the motor coil CL is switched, and the electric motor MT is rotationally driven. Then, the rotational power Tm is output from the electric motor MT to the reducer GS.

[0049] A rotation angle sensor KA is provided on the electric motor MT (brushless motor) to detect a rotation angle Ka. The rotation angle sensor KA is composed of a sensor disk Ds, a sensor magnet Ms, a sensor board Kb, and a sensor wire Ls. The sensor disk Ds is fixed to the motor shaft SM to rotate integrally with the motor shaft SM. The sensor disk Ds is provided with a sensor magnet Ms. The sensor board Kb is fixed to the motor housing HGm. A hole is formed in the sensor board Kb so that the motor shaft SM passes through. A detection unit using a magnetic field detection element is provided around the hole to detect a change in the magnetic field generated when the motor shaft SM (i.e., the sensor magnet Ms) rotates. A signal detected by the magnetic field detection element is transmitted to the first controller EA (particularly, the microprocessor MP) by the sensor wire Ls.

[0050] The speed reducer GS reduces the speed of the first rotational power Tm output from the electric motor MT and outputs a second rotational power Tn. Specifically, the input shaft of the speed reducer GS and the motor shaft SM are fixed. Also, the output shaft of the speed reducer GS and the rotating member BK of the conversion mechanism GH are fixed. In the speed reducer GS, the speed input from the electric motor MT is reduced and the torque input from the electric motor MT is increased. Then, the second rotational power Tn is output from the speed reducer GS to the conversion mechanism GH.

[0051] For example, a planetary gear mechanism is used as the reducer GS. A "planetary gear mechanism" is a gear mechanism in which multiple planetary gears revolve around a sun gear while rotating on their own axes. The reducer GS is composed of a sun gear, planetary gears, an internal gear, and a planetary carrier. In a planetary gear mechanism, the planetary gears are supported by the planetary carrier, and orbital motion is extracted. For example, in the reducer GS, the internal gear (also called "inner gear") is fixed to the cylinder housing HGc. The sun gear (also called "sun gear") is fixed to the motor shaft SM, and a first rotational power Tm is input to the sun gear from the electric motor MT. Then, the planetary carrier of the reducer GS is fixed to a rotating member BK, and a second rotational power Tn is output from the planetary carrier to the conversion mechanism GH.

[0052] The conversion mechanism GH is composed of a rotating member BK that rotates and a linear motion member BD that moves linearly. In the conversion mechanism GH, a second rotational power Tn output from the reducer GS is input to the rotating member BK. The second rotational power Tn input to the rotating member BK is then converted into a linear power Fn of the linear motion member BD. The conversion mechanism GH is also called a "rotational-linear motion conversion mechanism."

[0053] For example, a "ball screw" is adopted as the conversion mechanism GH. Specifically, in the conversion mechanism GH, a rotating member BK, which is a shaft member, is fixed to the output shaft of the reducer GS. The rotating member BK is inserted into a linear motion member BD having a cylindrical shape. A ball screw groove Mzk is formed on the outer peripheral surface Mok of the rotating member BK. Similarly, a ball screw groove Mzd is also formed on the inner peripheral surface Mid of the linear motion member BD. A plurality of balls BL (steel balls) are fitted into the ball screw grooves Mzk and Mzd (see blow-out section XGH for the above).

[0054] In the conversion mechanism GH, the member having a screw groove on its outer circumferential surface is referred to as the "inner member." Also, the member having a screw groove on its inner circumferential surface is referred to as the "outer member." The outer member is disposed so as to cover the inner member, and the screw groove of the inner member and the screw groove of the outer member are meshed with each other. In detail, in the ball screw mechanism, the two screw grooves are meshed with each other via multiple balls BL.

[0055] In the ball screw mechanism employed as the conversion mechanism GH, a ball screw shaft (an inner member, also referred to as a "shaft member") is used as the rotating member BK, and a ball screw nut (an outer member, also referred to as a "nut member") is used as the linear motion member BD. In this configuration, a screw groove Mzk is formed on the outer circumferential surface Mok of the rotating member BK (inner member), and a screw groove Mzd is formed on the inner circumferential surface Mid of the linear motion member BD (outer member). The outer circumferential groove Mzk and the inner circumferential groove Mzd are engaged with each other via a ball BL.

[0056] A flange portion Fd is provided on the end of the linear motion member BD away from the control cylinder CC (particularly, the control chamber Rc). The flange portion Fd is formed by extending the end of the cylindrical linear motion member BD in the radial direction Hk in a flange shape. A notch is formed in the flange portion Fd. The anti-rotation member MD is fitted into the notch.

[0057] The anti-rotation member MD is fixed to the cylinder housing HGc. For example, the anti-rotation member MD is a long and thin rod-shaped member (e.g., a pin member). The housing HG has a plurality of holes on the outer side of the linear motion member BD (i.e., on the side away from the rotation axis Jk with respect to the linear motion member BD). The plurality of holes are evenly spaced around the rotation axis Jk. The anti-rotation member MD is inserted into each of the plurality of holes and fixed. A semicircular notch is provided in the flange portion Fd of the linear motion member BD. The notch and the anti-rotation member MD are engaged with each other, thereby preventing the linear motion member BD from rotating around the rotation axis Jk. As a result, when the rotating member BK is rotationally driven, the linear motion member BD moves along the axial direction Hj (forward direction Ha or backward direction Hb).

[0058] The control piston NC is inserted into a control cylinder CC formed in the cylinder housing HGc. In detail, the control piston NC is composed of a bottom part Btn (also called "first bottom part") and a cylindrical part Enn (also called "first cylindrical part"). That is, the control piston NC has a cylindrical shape (cup shape) having the bottom part Btn. A control chamber Rc (hydraulic chamber) is formed inside the control cylinder CC by the control piston NC (particularly, the first bottom part Btn) inserted into the control cylinder CC.

[0059] The outer peripheral surface Mon of the control piston NC and the inner peripheral surface Mic of the control cylinder CC are sealed by two seal members SL. The two seal members SL are fitted into seal grooves formed in the inner peripheral surface Mic of the control cylinder CC. Between the two seal grooves, the cylinder housing HGc is provided with a hole (not shown, also called a "housing hole") penetrating the control cylinder CC. The housing hole is connected to the master reservoir RV via a supply path HH. The control piston NC is provided with a hole (not shown, also called a "piston hole") penetrating from the outer peripheral surface Mon to the bottom Btn to connect the housing hole to the control chamber Rc.

[0060] An intermediate member BE is provided between the linear moving member BD and the control piston NC in the axial direction Hj. The intermediate member BE transmits power between the linear moving member BD and the control piston NC. A linear power Fn from the linear moving member BD is transmitted to the control piston NC via the intermediate member BE. This allows the linear moving member BD, intermediate member BE, and control piston NC to move integrally in the forward direction Ha. Note that the linear moving member BD and the control piston NC are retained by a retaining member ND so that the linear moving member BD, intermediate member BE, and control piston NC can move integrally when returning in the backward direction Hb.

[0061] The control piston NC is sealed against the control cylinder CC by a seal member SL, but if axial misalignment occurs (particularly, misalignment between the direction of the linear power Fn and the moving direction of the control piston NC), the contact between the outer circumferential surface Mon of the control piston NC and the seal member SL becomes non-uniform. This can cause a decrease in sealing performance, uneven wear of the seal member SL, etc. In order to suppress the effects of axial misalignment of the control piston NC, etc. (i.e., a decrease in sealing performance, uneven wear of the seal member SL, etc.), an intermediate member BE is provided in the power transmission path from the linear motion member BD to the control piston NC.

[0062] The intermediate member BE is composed of a bottom portion Bte (also referred to as the "second bottom portion") and a cylindrical portion Ene (also referred to as the "second cylindrical portion"). Like the control piston NC, the intermediate member BE has a cylindrical shape (i.e., a cup shape) with the second bottom portion Bte. The intermediate member BE is housed inside (inside) the control piston NC. In other words, the control piston NC and the intermediate member BE are nested. This structure is called a "nested structure." In the nested structure, the outer control piston NC slides against the seal member SL to seal the control chamber Rc, and the influence of axial misalignment is compensated for by the inner intermediate member BE.

[0063] <Adjusting servo pressure Pc> In the brake control device SC, the wheel pressure Pw is adjusted by the servo pressure Pc which is the output of the hydraulic pressure generating unit PS. In the hydraulic pressure generating unit PS, the rotational power Tm (i.e., shaft torque) of the electric motor MT is converted by the conversion mechanism GH into a linear power Fn (i.e., thrust) of a linearly moving member BD (resulting in a control piston NC). Then, the control piston NC is moved by the linear power Fn, thereby generating and adjusting the servo pressure Pc. Note that the hydraulic pressure generating unit PS is provided with a servo pressure sensor PC to detect the servo pressure Pc.

[0064] The conversion mechanism GH is capable of both converting rotary motion into linear motion and converting linear motion into rotary motion. In the operation of the conversion mechanism GH, the former is called "positive operation" and the latter is called "negative operation." Therefore, the movement of the control piston NC is determined by the magnitude relationship between the torque output from the electric motor MT (also called "positive operation torque Qmt") and the torque input to the electric motor MT by the servo pressure Pc (also called "negative operation torque Qpc"). Adjustment (increase / decrease) of the servo pressure Pc will be explained below.

[0065] <Increase in servo pressure Pc> In Fig. 2, above the rotation axis Jk, a state in which the hydraulic pressure generating unit PS is not generating servo pressure Pc is shown. In this state, the control chamber Rc is connected to the master reservoir RV via the housing hole and the piston hole, and the servo pressure Pc is "0 (atmospheric pressure)." The positions of the linear motion member BD, the control piston NC, etc. in this state are referred to as the "initial position." In the initial position, the control piston NC is displaced to the maximum in the backward direction Hb, and the volume of the control chamber Rc is maximum.

[0066] As described above, the control piston NC and the intermediate member BE have a bottomed cylindrical shape (cup shape) and are nested within each other, so that the intermediate member BE is housed inside the control piston NC. Furthermore, when the control piston NC is in the initial position, the rotating member BK is inserted inside the intermediate member BE. This structure reduces the size of the hydraulic pressure generating unit PS in the axial direction Hj.

[0067] When the braking demand value (a state quantity indicating a demand related to the braking force, for example, the operation displacement Sp of the brake operating member BP) is increased, the target pressure Pt is increased from "0". The target pressure Pt is a target value corresponding to the servo pressure Pc (actual value). The target pressure Pt is increased with an increase in the braking demand value. With an increase in the target pressure Pt, the forward operating torque Qmt becomes larger than the reverse operating torque Qpc, and the electric motor MT rotates in the forward rotation direction Hs. That is, the electric motor MT generates a rotational force Tm in the forward rotation direction Hs. The rotational force Tm is transmitted to the conversion mechanism GH via the reducer GS and is output as a linear force Fn of the linear moving member BD. Then, the linear moving member BD presses the intermediate member BE, and the intermediate member BE presses the control piston NC. As a result, the control piston NC is moved in the forward direction Ha (the direction in which the volume of the control chamber Rc is reduced). From the viewpoint of the intermediate member BE, the rotating member BK gradually moves out from the inside of the intermediate member BE.

[0068] Due to this movement, the piston hole opened in the control piston NC moves into the control chamber Rc, so first, communication between the control chamber Rc and the master reservoir RV is blocked. When the control piston NC is further moved in the forward direction Ha, the servo pressure Pc (internal pressure of the control chamber Rc) is increased from "0 (atmospheric pressure)". Brake fluid BF pressurized to the servo pressure Pc is output (pressurized) from the control chamber Rc of the control cylinder CC to the servo chamber Ru and the rear wheel cylinder CWr.

[0069] <Maintaining servo pressure Pc> When the braking demand value becomes constant, the target pressure Pt is maintained. The forward acting torque Qmt and the reverse acting torque Qpc become equal, and the electric motor MT stops rotating (i.e., the rotational speed of the electric motor MT becomes "0"). The movement of the control piston NC is stopped, and the servo pressure Pc is maintained constant (see the lower part of the rotation axis Jk in Figure 2).

[0070] <Decrease in servo pressure Pc> When the braking demand value is reduced, the target pressure Pt is reduced, thereby reducing the rotational power Tm of the electric motor MT. The reverse acting torque Qpc due to the servo pressure Pc becomes greater than the forward acting torque Qmt due to the electric motor MT, and the electric motor MT rotates in the reverse direction Hg. The control piston NC is moved in the backward direction Hb, and the volume of the control chamber Rc is increased. The brake fluid BF that had been moved to the servo chamber Ru and the rear wheel cylinder CWr is returned toward the control chamber Rc, thereby reducing the servo pressure Pc. In terms of the positional relationship between the intermediate member BE and the rotating member BK, the rotating member BK gradually penetrates into the intermediate member BE.

[0071] <Compensation for the effect of axial misalignment using intermediate member BE> The suppression of the effects of axial misalignment by the intermediate member BE will be described with reference to the partial cross-sectional view of Fig. 3. Here, suppression of the effects caused by axial misalignment is called "axial misalignment compensation". Fig. 3 shows a state in which no axial misalignment occurs, and the rotation axis Jk of the rotating member BK, the central axis Je of the intermediate member BE, the central axis Jn of the control piston NC, and the central axis Jc of the control cylinder CC are aligned in a straight line.

[0072] <Axis misalignment> First, we will explain axial misalignment. In power transmission, it is desirable for the axes Jk, Jn, and Jc to be in a straight line. However, because the conversion mechanism GH, control piston NC, control cylinder CC, etc. are individual components, their axes Jk, Jn, and Jc can deviate from the straight line and become misaligned. Misalignment of the axes Jk, Jn, and Jc is called "axial misalignment." Axial misalignment is eccentricity (misalignment) between the axes, and is also called "misalignment."

[0073] For example, there are cases where two axes intersect but have an angle between them (i.e., lack of parallelism). This type of axial misalignment is called "declination misalignment (or declination error)." There are also cases where the two axes are not parallel. This type of axial misalignment is called "parallelism misalignment (or parallelism error)." Usually, axial misalignment occurs as a combination of declination misalignment and parallel misalignment.

[0074] As described above, when axial misalignment (misalignment) occurs, the contact between the outer peripheral surface Mon of the control piston NC and the seal member SL becomes uneven, which may cause a decrease in the sealing performance of the seal member SL and uneven wear. In addition, the load on the conversion mechanism GH becomes uneven, which may cause uneven wear of the ball member BL, the screw grooves Mzk, Mzd, etc. The hydraulic pressure generating unit PS is provided with an intermediate member BE to compensate for the axial misalignment.

[0075] <Configuration of intermediate parts BE, etc.> Next, detailed configurations of the conversion mechanism GH, the control piston NC, and the intermediate member BE will be described. The conversion mechanism GH is composed of a rotating member BK and a linear motion member BD. The translational motion (linear motion in the axial direction Hj) of the rotating member BK is constrained relative to the housing HG, but the rotational motion is held in a state in which it is possible. On the other hand, the rotational motion of the linear motion member BD is constrained relative to the housing HG, but the translational motion is held in a state in which it is possible. As a result, the conversion mechanism GH outputs the rotational power Tm input to the rotating member BK as a linear power Fn of the linear motion member BD. Here, in the conversion mechanism GH, the linear motion member BD is arranged so as to cover the rotating member BK. For example, in a configuration in which a ball screw mechanism is adopted as the conversion mechanism GH, the rotating member BK is a ball screw shaft, and the linear motion member BD is a ball screw nut.

[0076] A flange portion Fd is provided on an end of the linear motion member BD (more specifically, the end away from the bottom surface Mbc of the control cylinder CC or the bottom Btn of the control piston NC). A notch is formed on the outer periphery of the flange portion Fd. The notch engages with a rotation prevention member MD. The rotation prevention member MD is fixed to the housing HG. The rotation prevention member MD prevents the rotational motion of the linear motion member BD relative to the housing HG, so that the rotational motion of the rotating member BK can be converted into linear motion of the linear motion member BD.

[0077] The control piston NC is inserted into a control cylinder CC formed in the housing HG. The control piston NC has a bottomed cylindrical shape (cup shape) and is composed of a first bottom part Btn and a first cylindrical part Enn. Two seal grooves are formed in the inner circumferential surface Mic of the control cylinder CC. A seal member SL is fitted into each of the seal grooves. The outer circumferential surface Mon of the cylindrical part Enn and the inner circumferential surface Mic of the control cylinder CC are sealed by the seal member SL. The control piston NC (particularly, the bottom part Btn) forms a control chamber Rc (hydraulic pressure chamber) in the control cylinder CC. Note that a plane perpendicular to the central axis Jn of the control piston NC (i.e., the central axis of the first cylindrical part Enn) is formed on the inner bottom surface Mtn of the first bottom part Btn.

[0078] An annular groove is formed on the inner peripheral surface Min of the cylindrical portion Enn of the control piston NC. In addition, an annular groove is also formed on the outer peripheral surface Mod of the linear motion member BD. A retaining member ND (e.g., a snap ring) is fitted into these grooves. The retaining member ND limits the relative displacement between the control piston NC and the linear motion member BD so that the control piston NC and the linear motion member BD do not completely separate. The retaining member ND has a backlash (gap) with respect to the annular groove in the axial direction Hj and the radial direction Hk. Therefore, the control piston NC and the linear motion member BD can be displaced relative to each other within the range of the backlash in both the axial direction Hj and the radial direction Hk.

[0079] An intermediate member BE is provided between the control piston NC and the linear motion member BD. The intermediate member BE, like the control piston NC, has a bottomed cylindrical shape (cup shape) and is composed of a second bottom Bte and a second cylindrical portion Ene. In a nested structure (i.e., a structure in which the intermediate member BE is disposed inside the control piston NC), the bottom Btn (first bottom) of the control piston NC and the bottom Bte (second bottom) of the intermediate member BE are in contact with each other in a slidable state. Here, "sliding" refers to the action of two members moving while sliding in contact with each other.

[0080] In detail, slippage can occur between the outer bottom surface Mpe (also called the "pressing surface") of the intermediate member BE and the inner bottom surface Mtn (also called the "pressure receiving surface") of the control piston NC. A spherical convex portion with a radius Rq is formed on the pressing surface Mpe of the intermediate member BE. In addition, a round corner (also called the "corner") with a radius Rp is formed on the intermediate member BE at a portion (also called the "corner") where the pressing surface Mpe and the outer circumferential surface Moe of the cylindrical portion Ene are connected. That is, the corner of the bottom portion Bte of the intermediate member BE is rounded. Here, the radius Rq of the convex spherical surface is significantly larger than the radius Rp of the round corner. The portion where the pressing surface Mpe (outer bottom surface) of the intermediate member BE and the pressure receiving surface Mtn (inner bottom surface) of the control piston NC come into contact is called the "first sliding portion Sda".

[0081] An end surface Mqe (also referred to as the "middle end surface") of the cylindrical portion Ene of the intermediate member BE is in slidable contact with an end surface Mpd (also referred to as the "linear end surface") of the linear motion member BD. For example, the middle end surface Mqe is a plane perpendicular to the central axis Je (i.e., the central axis of the second cylindrical portion Ene) of the intermediate member BE. Furthermore, the linear motion end surface Mpd is a plane perpendicular to the rotation axis Jk. Therefore, the linear motion end surface Mpd and the middle end surface Mqe contact on a plane perpendicular to the axial direction Hj and parallel to the radial direction Hk. Here, the portion where the middle end surface Mqe of the intermediate member BE and the linear motion end surface Mpd of the linear motion member BD contact each other is referred to as the "second sliding portion Sdb."

[0082] The configurations of the conversion mechanism GH, the control piston NC, and the intermediate member BE can be summarized as follows. The intermediate member BE is accommodated inside the control piston NC. The intermediate member BE is located between the linear motion member BD (particularly, the linear motion end surface Mpd) and the control piston NC (particularly, the pressure receiving surface Mtn). When the servo pressure Pc increases, the linear motion end surface Mpd (flat surface) presses the intermediate end surface Mqe (flat surface) in the forward direction Ha, and the pressure receiving surface Mtn (flat surface) presses the pressure receiving surface Mtn (flat surface) in the forward direction Ha. As a result, the control piston NC, the intermediate member BE, and the linear motion member BD move in the forward direction Ha. Conversely, when the servo pressure Pc decreases, the pressure receiving surface Mpe presses the pressure receiving surface Mpe in the backward direction Hb, and the linear motion end surface Mpd is pressed in the backward direction Hb by the intermediate end surface Mqe. As a result, the control piston NC, the intermediate member BE, and the linear motion member BD move in the backward direction Hb. Here, the intermediate member BE has two portions (that is, first and second sliding portions Sda, Sdb) that can slide with the control piston NC and the linear motion member BD.

[0083] The rotating member BK can enter inside the cylindrical portion Ene of the intermediate member BE. In other words, the cylindrical portion Ene of the intermediate member BE can enter into the gap between the cylindrical portion Enn (particularly, the inner peripheral surface Min) of the control piston NC and the rotating member BK (particularly, the outer peripheral surface Mok). The intermediate member BE and the control piston NC move in response to the movement of the linearly moving member BD, but at least in the initial position (the position corresponding to "Pc = 0"), a part of the rotating member BK is housed inside the intermediate member BE. In the hydraulic pressure generating unit PS, the dimension in the axial direction Hj is shortened by "adopting a cup shape for the control piston NC and the intermediate member BE and forming them into a nested structure" and "housing the rotating member BK inside the intermediate member BE".

[0084] <Axis misalignment compensation> Finally, we will explain the compensation for axial misalignment. The effect of axial misalignment is compensated for by "allowing slippage in the radial direction Hk between the power transmission members (BD, BE, NC, etc.)" and "allowing the intermediate member BE to rotate when the control piston NC is in contact with the intermediate member BE." The power transmission members have gaps Ska, Skb between them in the radial direction Hk. The linear motion member BD, intermediate member BE, and linear motion member BD can move while sliding between the members due to the gaps Ska, Skb.

[0085] In the first sliding portion Sda, the pressure receiving surface Mtn of the control piston NC (for example, a plane perpendicular to the central axis Jn of the first cylindrical portion Enn) and the pressing surface Mpe of the intermediate member BE (for example, a convex surface) come into contact. The pressure receiving surface Mtn and the pressing surface Mpe can be displaced relative to each other in the radial direction Hk within the range of the gap Ska between the inner peripheral surface Min of the control piston NC and the outer peripheral surface Moe of the intermediate member BE, or within the range of the gap Skb between the inner peripheral surface Mie of the intermediate member BE and the outer peripheral surface Mok of the rotating member BK. In addition, since the pressing surface Mpe is a convex surface (for example, a spherical surface), they can be rotated relative to each other around the contact portion between the pressure receiving surface Mtn and the pressing surface Mpe. This rotational motion is called "swinging". The swinging and sliding (sliding) in the first sliding portion Sda suppress the influence of axial deviation (angle deviation and parallel deviation) of the control piston NC and the like. When the rotational displacement (i.e., the degree of swing) between the pressure-receiving surface Mtn and the pressing surface Mpe becomes large, the pressure-receiving surface Mtn comes into contact with a corner of the intermediate member BE. Because the corner is rounded (rounded), the contact pressure between the pressure-receiving surface Mtn and the pressing surface Mpe is suppressed even if the angular deviation becomes excessive.

[0086] At the second sliding portion Sdb, the linear end surface Mpd of the linear member BD (e.g., a plane perpendicular to the rotation axis Jk of the rotating member BK) and the intermediate end surface Mqe of the intermediate member BE (e.g., a plane perpendicular to the central axis Je of the second cylindrical portion Ene) come into contact. In this contact, the linear end surface Mpd and the intermediate end surface Mqe can slide relative to each other. Therefore, the linear end surface Mpd and the intermediate end surface Mqe can be displaced relative to each other in the radial direction Hk "within the range of the gap Ska between the inner circumferential surface Min of the control piston NC and the outer circumferential surface Moe of the intermediate member BE" or "within the range of the gap Skb between the inner circumferential surface Mie of the intermediate member BE and the outer circumferential surface Mok of the rotating member BK".

[0087] The control piston NC is held in the housing HG by a seal member SL. The conversion mechanism GH (particularly, the linear motion member BD) is held in the housing HG by a bearing. The intermediate member BE is not directly held in the housing HG, but serves as a floating joint. Specifically, the intermediate member BE can slide and move in parallel in the radial direction Hk with respect to both the control piston NC and the linear motion member BD. This suitably suppresses the influence of parallel deviation. Furthermore, since the intermediate member BE can oscillate with respect to the control piston NC, the influence of the angular deviation is suitably suppressed. In addition, the existence of the second sliding part Sdb does not prevent the sliding and oscillating at the first sliding part Sda. That is, the sliding and oscillating are made easy to occur, and the compensation effect of the angular deviation is improved. In the hydraulic pressure generating unit PS, the intermediate member BE is provided with two sliding parts Sda and Sdb, so that not only the influence of parallel deviation is suppressed, but also the influence of the angular deviation is suitably compensated.

[0088] It is desirable to set the distance Lbe between the first sliding part Sda and the second sliding part Sdb (i.e., the length of the axial direction Hj of the intermediate member BE) longer than the interval between the two seal members SL. This is because the effect of compensating for axial misalignment is higher when the first and second sliding parts Sda and Sdb are spaced apart to a certain extent.

[0089] <Other embodiments of the hydraulic pressure generating unit PS> Other embodiments of the hydraulic pressure generating unit PS will be described below. In the other embodiments, the hydraulic pressure generating unit PS also provides the same effects (axis misalignment compensation, etc.) as described above.

[0090] In the embodiment of the hydraulic pressure generating unit PS described above, a ball screw is used as the conversion mechanism GH. Alternatively, a sliding screw (e.g., a trapezoidal screw) may be used as the conversion mechanism GH. In a configuration in which a sliding screw mechanism is used, a male thread is formed as a screw groove on the inner member. Also, a female thread is formed as a screw groove on the outer member. The male thread and the female thread are directly engaged with each other. Reverse operation occurs even in a conversion mechanism GH in which a sliding screw is used.

[0091] In the embodiment of the hydraulic pressure generating unit PS described above, a configuration is adopted in which the axis Jm and the axes Jc, Jn, and Jk are aligned in a straight line. This configuration is called a "coaxial configuration (or single-shaft configuration)" because the axis Jm and the axis Jc, etc. are coaxial. In the coaxial configuration, a reducer GS in which the rotation axis of the input shaft and the rotation axis of the output shaft are coaxial (for example, a planetary gear mechanism) is used. Instead of this configuration, a "separate-shaft configuration (or two-shaft configuration)" in which the axis Jm and the axis Jc, Jn, and Jk are on different axes may be used. In the separate-shaft configuration, a reducer GS in which the rotation axis of the input shaft and the rotation axis of the output shaft are different (for example, a gear train) is used. In the separate-shaft configuration, the axis Jm and the axis Jc, Jn, and Jk are separate axes but are arranged in parallel. Even in the separate shaft configuration, the axes Jc, Jn, and Jk are in the same straight line.

[0092] In the above-described embodiment of the hydraulic pressure generating unit PS, the intermediate member BE can slide relative to the linearly moving member BD. In contrast, the intermediate member BE may be fixed so as not to slide relative to the linearly moving member BD. Alternatively, the intermediate member BE may not be provided, and the pressing surface Mpe may be formed directly on the linearly moving member BD (i.e., a configuration in which the linearly moving member BD and the intermediate member BE are integrated). In this configuration, the linear force Fn from the linearly moving member BD is directly transmitted to the control piston NC. Even in these configurations, the pressure receiving surface Mtn of the control piston NC and the pressing surface Mpe of the intermediate member BE (or the linearly moving member BD) have the effect of compensating for the axial misalignment. However, the effect of compensating for the axial misalignment can be improved by making the intermediate member BE and the linearly moving member BD slidable at the second sliding portion Sdb.

[0093] The above-mentioned braking control device SC is applied to a vehicle in which the front wheels WHf are provided with a regenerative device KG and in which regenerative cooperative control is executed. In a vehicle in which regenerative cooperative control is executed, the regenerative device KG may be provided in at least one of the front wheels WHf and the rear wheels WHr. The braking control device SC may also be applied to a vehicle in which the regenerative device KG is power-saving and in which regenerative cooperative control is not executed. In other words, the braking control device SC may be applied to various vehicles, regardless of whether or not regenerative cooperative control is executed.

[0094] In the above-mentioned example of the configuration of the brake control device SC, a single-type master cylinder CM is used. A tandem-type master cylinder CM may be used in the brake control device SC. In this configuration, two master chambers Rm are formed inside the CM. Then, the servo pressure Pc is supplied from the hydraulic pressure generating unit PS to the servo chamber Ru, and the wheel pressure Pw is supplied from the master chamber Rm to the wheel cylinder CW. In this configuration, the brake control device SC may adopt not only a front-rear type but also a diagonal type (also called "X type") as the two-system brake system. In the diagonal type brake control device SC, one of the two master chambers Rm is connected to the right front wheel cylinder and the left rear wheel cylinder. Also, the other of the two master chambers Rm is connected to the left front wheel cylinder and the right rear wheel cylinder.

[0095] In the above-mentioned configuration example of the brake control device SC, in the first brake unit SA, the supply pressure Pm is outputted via the master cylinder CM. That is, the apply unit AP and the hydraulic pressure generating unit PS are arranged in series in the hydraulic pressure transmission path, and the servo pressure Pc supplied from the hydraulic pressure generating unit PS is transmitted as the supply pressure Pm via the master piston NM. Alternatively, the apply unit AP and the hydraulic pressure generating unit PS may be arranged in parallel. Specifically, the apply unit AP (particularly, the master cylinder CM) and the hydraulic pressure generating unit PS are each directly connected to the second actuator YB. Then, either one of "connection between the hydraulic pressure generating unit PS and the second actuator YB" and "connection between the apply unit AP and the second actuator YB" is selected by an on-off solenoid valve (referred to as a "switching valve"). When the former is selected, the servo pressure Pc generated in the hydraulic pressure generating unit PS is directly outputted as the supply pressure Pm without passing through the apply unit AP. At this time, the apply unit AP is connected to the stroke simulator SS, and the operating force of the brake operating member BP is generated by the stroke simulator SS. On the other hand, when the latter is selected, the hydraulic pressure in the master chamber Rm generated by the operation of the brake operating member BP is output as the supply pressure Pm. At this time, the apply unit AP is disconnected from the simulator SS.

[0096] In the above-mentioned example of the configuration of the brake control device SC, in the apply unit AP, the pressure receiving area rm (master area) of the master chamber Rm and the pressure receiving area ru (servo area) of the servo chamber Ru are set to be equal. The master area rm and the servo area ru do not have to be equal. In a configuration in which the master area rm and the servo area ru are different, it is possible to perform a conversion calculation between the supply pressure Pm (master pressure) and the servo pressure Pc based on the ratio between the servo area ru and the master area rm (i.e., conversion based on "Pm·rm=Pc·ru").

[0097] <Summary of the embodiment> The following summarizes an embodiment of the hydraulic pressure generating unit PS (hydraulic pressure generating device): The hydraulic pressure generating unit PS is applied to a brake control device SC that adjusts the wheel pressure Pw of the wheel cylinder CW to control the braking force of the wheel WH.

[0098] The hydraulic pressure generating unit PS includes an electric motor MT, a conversion mechanism GH, a control piston NC, a rotation-stop member MD, and an intermediate member BE. The electric motor MT outputs a rotational power Tm. The conversion mechanism GH outputs the rotational power Tm input to the rotating member BK as a linear power Fn of the linear moving member BD. In the conversion mechanism GH, the linear moving member BD is disposed so as to cover the rotating member BK. In other words, the rotating member BK is the inner member, and the linear moving member BD is the outer member.

[0099] The control piston NC has a bottomed cylindrical shape and is inserted into a control cylinder CC formed in a housing HG that holds the conversion mechanism GH. The control piston NC increases the hydraulic pressure Pc (servo pressure) in the control cylinder CC by moving due to linear power Fn. Specifically, the servo pressure Pc increases as the control piston NC moves in a direction Ha (forward direction) toward the bottom surface Mbc of the control cylinder CC. The anti-rotation member MD is fixed to the housing HG. The anti-rotation member MD prevents (restrains) the rotational motion of the linear motion member BD. This allows the linear motion member BD to move in the axial direction Hj.

[0100] For example, the anti-rotation member MD is a pin member with a circular cross section. A portion of the housing HG that is farther from the rotation axis Jk than the linear motion member BD (i.e., a portion of the housing HG outside the linear motion member BD) is provided with a number of circular holes. The anti-rotation member MD is fixed to these circular holes. A number of semicircular cutouts are formed in the flange portion Fd of the linear motion member BD. The cutouts are fitted into the anti-rotation member MD to restrain (restrict) the rotational motion of the linear motion member BD.

[0101] The intermediate member BE is located between the linear member BD and the control piston NC. The intermediate member BE presses the control piston NC by being pressed by the linear member BD. The intermediate member BE comes into contact with the control piston NC in a slidable state. For example, the pressing surface Mpe (one end surface pressing the control piston NC) of the intermediate member BE is formed as a convex surface. Also, the bottom surface Mtn of the control piston NC is formed as a plane perpendicular to the central axis Jc. The intermediate member BE presses the bottom surface Mtn of the control piston NC with the pressing surface Mpe. At this time, the pressing surface Mpe can slide along the bottom surface Mtn of the control piston NC. Specifically, the slide occurs in the radial direction Hk (see the first sliding portion Sda). In the first sliding portion Sda, the pressing surface Mpe and the pressure receiving surface Mtn can slide against each other.

[0102] In the hydraulic pressure generating unit PS, the linear motion member BD is disposed outside the rotating member BK. Therefore, the rotational motion of the linear motion member BD can be prevented by the rotation prevention member MD fixed to the housing HG. That is, in order to prevent the rotation, it is not necessary to fix the control piston NC and the linear motion member BD so that they rotate together. Even if a cup-shaped (cylindrical with a bottom) control piston NC is adopted, the control piston NC and the linear motion member BD can be separated, so that in the hydraulic pressure generating unit PS, an intermediate member BE is provided between the control piston NC and the linear motion member BD. And, since the intermediate member BE and the control piston NC can slide against each other, the influence of the axial deviation is compensated. In addition, since the pressing surface Mpe is a convex surface, the intermediate member BE can oscillate around the contact part between the convex surface Mpe and the bottom surface Mtn (flat surface). That is, the intermediate member BE can easily rotate in addition to translational motion (sliding in the radial direction Hk) with respect to the control piston NC. This suitably suppresses the influence of the axial deviation.

[0103] In the hydraulic pressure generating unit PS, the intermediate member BE is pressed by the linear moving member BD in a slidable state. For example, the end face Mpd of the linear moving member BD that presses the intermediate member BE is formed as a plane perpendicular to the rotation axis Jk. The end face Mqe of the intermediate member BE (located opposite to the one-side end face Mpe and the other-side end face pressed by the linear moving member BD) can slide in the radial direction Hk along the plane Mpd (see the second sliding portion Sdb). In the second sliding portion Sdb, the linear moving end face Mpd and the intermediate end face Mqe can slide against each other.

[0104] The axial misalignment is compensated for by sliding and rocking between the control piston NC and the intermediate member BE. At this time, if the intermediate member BE is firmly fixed to the linearly moving member BD, these are less likely to occur. In the above configuration, the end face Mqe of the intermediate member BE can slide along the end face Mpd of the linearly moving member BD, so that sliding and rocking between the control piston NC and the intermediate member BE can be easily generated. This can improve the effect of compensating for the influence of the axial misalignment.

[0105] The intermediate member BE has a bottomed cylindrical shape and is disposed inside the control piston NC (i.e., a nested structure). Furthermore, the rotating member BK of the conversion mechanism GH can enter inside the intermediate member BE. In detail, at least when the servo pressure Pc is "0", a portion of the rotating member BK is contained inside the intermediate member BE. If an additional intermediate member BE is provided between the conversion mechanism GH (particularly the linear member BD) and the control piston NC to compensate for the axial misalignment, there is a concern that the device will become larger in size in terms of the axial dimension (axial length). With this configuration, even if the intermediate member BE is provided, the hydraulic pressure generating unit PS can be prevented from becoming larger. [Explanation of symbols]

[0106] SC...Brake control device, SX...Brake device, BP...Brake operating member (brake pedal), BF...Brake fluid (hydraulic fluid), SA, SB...First and second brake units, YA, YB...First and second actuators, EA, EB...First and second controllers, BS...Communication bus, CM...Master cylinder, CW...Wheel cylinder, AP...Apply unit, NR...Input unit, PS...Hydraulic pressure generating unit (Hydraulic pressure generator), MT...Electric motor, VA, VB...First and second control valves, SP...Operation displacement sensor, Sp...Operation displacement (detected value of SP), PC...Servo pressure sensor, Pc...Servo pressure (internal pressure of Rc, detected value of PC), Pm...Supply pressure (internal pressure of Rm), Pwf, Pwr...Front and rear wheel pressure, HG...Housing (generic term for HGm and HGc), HGm...Motor housing (part of HG), HGc...Cylinder housing (part of HG) part), GS... reducer, GH... conversion mechanism, BK... rotating member, BD... linear member, NC... control piston, BE... intermediate member, CC... control cylinder, MD... anti-rotation member, ND... retaining member, Rc... control chamber (hydraulic chamber of CC), Fd... flange part of BD, Tm... first rotating power (output from MT, input to GS), Tn... second rotating power (output from GS, input to BK), Fn... linear power (BD output), Mtn...pressure-receiving surface of NC (inner bottom surface of Btn), Mpe...pressure surface of BE (outer bottom surface of Bte), Mqe...end face of BE (middle end face), Mpd...end face of BD (linear end face), Jm...rotation axis of MT, Jk...rotation axis of BK, Jn...central axis of NC, Jc...central axis of CC, Je...central axis of BE, Sda...first sliding part (sliding part between NC and BE), Sdb...second sliding part (sliding part between BE and BD).

Claims

1. an electric motor that outputs rotational power; a conversion mechanism that outputs the rotational power input to a rotational member as linear power of a linear motion member, the linear motion member being disposed so as to cover the rotational member; a piston having a bottomed cylindrical shape, inserted into a cylinder formed in a housing that holds the conversion mechanism, and moved by the linear power to increase the hydraulic pressure in the cylinder; a rotation prevention member fixed to the housing and configured to prevent rotational motion of the linear motion member; an intermediate member that is located between the piston and the linear motion member and presses the piston in a slidable state; A hydraulic pressure generating device comprising:

2. 2. The hydraulic pressure generating device according to claim 1, The intermediate member has a convex pressing surface that presses against a bottom surface of the piston, and the pressing surface can slide along the bottom surface.

3. The hydraulic pressure generating device according to claim 1 or 2, The intermediate member is pressed in a slidable state by the linear motion member.

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