Hydraulic pressure generating device

A hydraulic pressure generating device includes a base body, a master cylinder provided on the base body and configured to generate a brake hydraulic pressure by a first piston connected to a brake operating element, a housing attached to the base body, a control board contained in the housing, a stroke sensor configured to detect an amount of movement of the first piston; and a detection object member which is detected by the stroke sensor. The housing has a facing wall portion provided so as to face the base body. The stroke sensor is provided inside the housing on the opposite side of the facing wall portion to the base body, and is electrically connected to the control board.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2016-069579, filed Mar. 30, 2016. The contents of this application are incorporated herein by reference in their entirety.

The present invention relates to a hydraulic pressure generating device usable in a brake system for a vehicle.

In the related art, as a hydraulic pressure generating device usable in a brake system for a vehicle, a hydraulic pressure generating device including a master cylinder for generating a brake hydraulic pressure in response to the amount of operation on a brake operating element is known (see Japanese Patent Application Laid-Open No. 2012-210879 for instance).

In a master cylinder device (a hydraulic pressure generating device) disclosed in Japanese Patent Application Laid-Open No. 2012-210879, the brake operating element is connected to a stroke sensor. The stroke sensor detects an actual stroke amount (the amount of depression of the brake operating element from its origin position) as the amount of operation. The detected operation amount is converted into an electric signal, which is output to other devices such as a motor cylinder device (a slave cylinder) for generating a brake hydraulic pressure by a piston using a motor as its driving source.

In the above-described hydraulic pressure generating device disclosed in Japanese Patent Application Laid-Open No. 2012-210879, since the stroke sensor is connected to the brake operating element, it is required to secure a space for mounting the stroke sensor in a vehicle. Also, since the stroke sensor is installed outside the hydraulic pressure generating device, it is required to protect the stroke sensor from the outside such that it is possible to secure reliability.

The present invention was made in view of the above-described circumstances, and an object of the present invention is to provide a hydraulic pressure generating device making it easier to secure a space for mounting the hydraulic pressure generating device in a vehicle and capable of protecting a stroke sensor.

A hydraulic pressure generating device according to the present invention may include a base body, and a master cylinder provided on the base body and configured to generate a brake hydraulic pressure by a first piston connected to a brake operating element. Also, the hydraulic pressure generating device may include a housing attached to the base body, and a control board contained in the housing. Further, the hydraulic pressure generating device may include a stroke sensor configured to detect the amount of movement of the first piston, and a detection object member which is detected by the stroke sensor. Also, the housing has a facing wall portion may be provided so as to face the base body. The stroke sensor may be provided inside the housing on the opposite side of the facing wall portion to the base body, and is electrically connected to the control board.

The hydraulic pressure generating device can detect an input attributable to an operator's operation on a brake by the stroke sensor contained in the housing. Also, a signal detected by the stroke sensor is input directly to the control board. As described above, the stroke sensor is contained in the housing attached to the base body. Therefore, it becomes possible to reduce the size of the base body even though the stroke sensor is included, and it is possible to achieve an advantage that it is easy to secure a space for mounting the hydraulic pressure generating device on a vehicle.

Also, since a portion of the stroke sensor positioned on the base body side is covered by the facing wall portion, for example, during maintenance, when a worker attaches or detaches the housing to or from the base body, it is possible to suppress the fingers of the worker from touching the stroke sensor, other components, and so on. Further, it is possible to suppress entry of external foreign materials by the facing wall portion, and it is possible to provide a dust proofing function. Since the stroke sensor is protected by the facing wall portion as described above, it is possible to secure detection accuracy and durability, and it is possible to improve reliability.

In other words, according to this invention, it is possible to provide the hydraulic pressure generating device making it easier to secure a space for mounting the hydraulic pressure generating device on a vehicle and capable of protecting the stroke sensor.

Besides, since the hydraulic pressure generating device includes the stroke sensor, as compared to a case where the stroke sensor is configured separately from the hydraulic pressure generating device, it is unnecessary to separately provide the stroke sensor and form signal lines. For this reason, assembling man-hours when the hydraulic pressure generating device is mounted on a vehicle decrease, and the number of components decreases. Therefore, it is possible to reduce the manufacturing cost.

In the above-described hydraulic pressure generating device, the stroke sensor may include a detection element configured to detect the detection object member, and a sensor board having the detection element thereon, and inside the housing, a conductive member may be installed so as to connect the sensor board and the control board. Here, the sensor board may be fixed to the conductive member.

According to this configuration, since it is possible to fix the sensor board by the conductive member, the stroke sensor does not need to be contained, for example, inside a resin mold component, and also does not need connectors for connection. Therefore, the configuration of the stroke sensor is simplified, and the cost decreases.

In the above-described hydraulic pressure generating device, in a state where a male terminal provided on one of the sensor board and an end portion of the conductive member positioned on the sensor board side is inserted in a female terminal provided on the other, the sensor board may be fixed to the conductive member.

According to this configuration, since the male terminal is inserted into the female terminal, it is possible to fix the sensor board, for example, by pressing (for example, press fitting).

In the above-described hydraulic pressure generating device, a portion of the conductive member may be buried in the facing wall portion of the housing.

According to this configuration, it is possible to stably and securely fix the conductive member to the housing by the facing wall portion. As a result, the male terminal provided at the end portion of the conductive member is precisely positioned. Therefore, it becomes easier to connect the sensor board to the male terminal of the conductive member, and the electrical connection of the conductive member with the sensor board becomes securer.

In the above-described hydraulic pressure generating device, a plurality of solenoid valves may be attached to a surface of the base body to which the housing is attached, and the extension direction of an end portion of the conduction member positioned on the sensor board side may be disposed in parallel to the central axes of the solenoid valves.

According to this configuration, it is possible to move the sensor board of the stroke sensor in the same direction as the direction in which the solenoid valves V are attached to the base body, and connect the sensor board to the end portion of the conductive member positioned on the sensor board side. Therefore, it is possible to efficiently install the stroke sensor.

In the above-described hydraulic pressure generating device, the end portion of the conductive member positioned on the sensor board side may extend in a direction from the base body toward the control board and be connected to the sensor board.

According to this configuration, it is possible to move the sensor board of the stroke sensor in the same direction as a direction in which the control board is attached to the inside of the housing, and connect the sensor board to the end portion of the conductive member positioned on the sensor board side. Therefore, it is possible to efficiently install the stroke sensor.

In the above-described hydraulic pressure generating device, the housing may have a surrounding wall protruding from the facing wall portion and surrounding the stroke sensor.

According to this configuration, the stroke sensor is covered and protected by the facing wall portion and the surrounding wall. Therefore, it is possible to further improve the reliability of the stroke sensor.

In the above-described hydraulic pressure generating device, the stroke sensor may be fixed to the housing.

According to this configuration, it is possible to securely prevent the stroke sensor from unexpectedly moving. Therefore, it is possible to further improve the reliability of the stroke sensor.

In the above-described hydraulic pressure generating device, the stroke sensor may be buried in a resin fixed on the facing wall portion of the housing.

According to this configuration, it is possible to easily and securely fix the stroke sensor to the housing, and since the whole of the stroke sensor is covered by the resin, the stroke sensor is more securely protected.

The above-described hydraulic pressure generating device may further include a motor attached to the base body, and a slave cylinder provided on the base body and using the motor as its driving source and configured to generate a hydraulic pressure by a second piston. Here, the base body has a first cylinder bore with a bottom in which the first piston is inserted, and a second cylinder bore with a bottom in which the second piston is inserted. Also, the axial line of the first cylinder bore, the axial line of the second cylinder bore, and the axial line of an output shaft of the motor are disposed in parallel. Further, below the first cylinder bore, the second cylinder bore and the motor are disposed on the left and right of a vertical reference plane including the axial line of the first cylinder bore. Furthermore, the housing and the slave cylinder are disposed side by side in a vertical direction.

According to this configuration, since the master cylinder, the slave cylinder and the motor are disposed with good balance, it is possible to reduce the size of the hydraulic pressure generating device, and since the heavy motor is disposed at a lower portion, it is possible to improve the stability of the hydraulic pressure generating device. Also, since it is possible to dispose the housing while effectively using a space around the base body, it is possible to further reduce the size of the hydraulic pressure generating device. Therefore, it becomes easier to secure a space for mounting the hydraulic pressure generating device on a vehicle.

According to the present invention, it is possible to provide a hydraulic pressure generating device making it easier to secure a space for mounting the hydraulic pressure generating device in a vehicle and capable of protecting a stroke sensor.

An embodiment of the present invention will be described in detail, appropriately with reference to the accompanying drawings.

In the present embodiment, a case of applying a hydraulic pressure generating device of the present invention to a brake system for a vehicle will be described as an example.

As shown inFIG. 1, a brake system A for a vehicle includes both of a brake-by-wire type brake system configured to operate during activation of a power source (such as an engine or an electric motor) and a hydraulic type brake system configured to operate during stop of the power source or the like.

The brake system A for a vehicle can be mounted on a hybrid vehicle using both of an engine and a motor, an electric vehicle or a fuel cell vehicle using only a motor as a power source, or a vehicle using only an engine (an internal combustion engine) as a power source.

The brake system A for a vehicle includes a hydraulic pressure generating device1which generates a brake hydraulic pressure in response to the stroke amount (operation amount) of a brake pedal P (corresponding to a “brake operating element” of claims) and assists stabilization of motion of a vehicle.

The hydraulic pressure generating device1includes a base body100, a master cylinder10configured to generate a brake hydraulic pressure in response to the stroke amount of the brake pedal P, a stroke simulator40configured to apply a pseudo operation reaction force to the brake pedal P, and a slave cylinder20configured to use a motor24as a driving source and generate a brake hydraulic pressure. Further, the hydraulic pressure generating device1includes a hydraulic pressure control device30configured to control the hydraulic pressure of brake fluid to act on wheel cylinders W of wheel brakes BR, thereby assisting stabilization of motion of a vehicle, an electronic control device90, and a reservoir tank80.

Also, in the following description, directions are directions set in order to facilitate a description of the hydraulic pressure generating device1, and substantially coincide with the directions of the hydraulic pressure generating device1as seen in a state where it is mounted on a vehicle. In other words, a direction toward which a rod P1moves when the brake pedal P is depressed is referred to as the front side (the front end side), and a direction toward which the rod P1moves when the brake pedal P returns to its original position is referred to as the rear side (the rear end side) (seeFIG. 2). Further, a horizontal direction perpendicular to the movement direction (front-rear direction) of the rod P1is referred to as the left-right direction (seeFIG. 2).

The base body100is a metal block to be mounted on a vehicle (seeFIG. 3). In the base body100, three cylinder bores11,21, and41and a plurality of hydraulic passages2a,2b,3,4,5a,5b,73,74, and the like are formed. Also, on the base body100, various components such as the reservoir tank80and the motor24are attached.

In the base body100, as shown inFIG. 7, the first cylinder bore11, the second cylinder bore21, and the third cylinder bore41are formed in a cylindrical shape with a bottom. Each of the cylinder bores11,21, and41extends in the front-rear direction, and axial lines L1, L2, and L3of the cylinder bores11,21, and41are disposed side by side in parallel to one another. Also, the rear end portions of the cylinder bores11,21, and41are formed in rear surfaces101band102bof the base body100.

As shown inFIG. 1, the master cylinder10is a tandem piston type, and includes two first pistons12band12b(a secondary piston and a primary piston) inserted in the first cylinder bore11, and two coil springs17band17bcontained in the first cylinder bore11.

Between a bottom surface11aof the first cylinder bore11and the first piston12a(the secondary piston) positioned on the bottom side, a bottom side pressure chamber16ais formed. The bottom side pressure chamber16acontains the coil spring17a. If the first piston12amoves toward the bottom surface11a, the coil spring17apushes the first piston back toward an opening11b.

Between the first piston12apositioned on the bottom side and the first piston12b(the primary piston) positioned on the opening side, an opening side pressure chamber16bis formed. Also, the opening side pressure chamber16bcontains the coil spring17b. If the first piston12bmoves toward the bottom surface11a, the coil spring17bpushes the first piston back toward the opening11b.

The rod P1of the brake pedal P is inserted in the first cylinder bore11. The leading end portion of the rod P1is connected to the first piston12bpositioned on the opening side. As a result, the first piston12bpositioned on the opening side is connected to the brake pedal P by the rod P1.

The two first pistons12aand12bslide inside the first cylinder bore11in response to a depression force on the brake pedal P, thereby pressing the brake fluid contained in the bottom side pressure chamber16aand the opening side pressure chamber16b.

The reservoir tank80is a reservoir for storing the brake fluid, and is attached to an upper surface101eof the base body100(seeFIG. 2). Two fluid supply parts protruding from the lower surface of the reservoir tank80are inserted in two reservoir union ports81and82formed in the upper surface101eof the base body100. The brake fluid is supplied from the reservoir tank80into the bottom side pressure chamber16aand the opening side pressure chamber16bthrough the reservoir union ports81and82.

The stroke simulator40includes a third piston42inserted in the third cylinder bore41, a lid member44configured to block an opening41bof the third cylinder bore41, and two coil springs43aand43bcontained between the third piston42and the lid member44.

Between a bottom surface41aof the third cylinder bore41and the third piston42, a pressure chamber45is formed. The pressure chamber45formed inside the third cylinder bore41is connected to the opening side pressure chamber16bof the first cylinder bore11by a hydraulic branch passage3and the second main hydraulic passage2bto be described below.

In the stroke simulator40, the brake hydraulic pressure generated in the opening side pressure chamber16bof the master cylinder10causes the third piston42of the stroke simulator40to move against the biasing forces of the coil springs43aand43b, whereby the biased third piston42applies a pseudo operation reaction force to the brake pedal P.

The slave cylinder20is a single piston type, and includes a second piston22inserted in the second cylinder bore21, a coil spring23contained in the second cylinder bore21, the motor24, and a drive transmission unit25.

Between a bottom surface21aof the second cylinder bore21and the second piston22, a pressure chamber26is formed. Also, the pressure chamber26contains the coil spring23. If the second piston22moves toward the bottom surface21a, the coil spring23pushes the second piston back toward an opening21b.

The motor24is an electric servo motor which is driven and controlled by the electronic control device90to be described below. From the central portion of the rear surface of the motor24, an output shaft24aprotrudes toward the rear side.

The motor24is attached to the front surface of a flange portion103of the base body100(seeFIG. 4). The output shaft24aprotrudes from the rear side of the flange portion103through a through-hole103cformed in the flange portion103. On the rear end portion of the output shaft24a, a driving pulley24bis fit.

The drive transmission unit25is a mechanism for converting a rotation drive force of the output shaft24aof the motor24into an axial force of a straight line direction.

The drive transmission unit25includes a rod25a, a cylindrical nut member25bfit on the rod25a, a driven pulley25cfit on the nut member25b, an endless belt25dsuspended between the driven pulley25cand the driving pulley24b, and a cover member25e.

The rod25ais inserted from the opening21bof the second cylinder bore21into the second cylinder bore21, such that the front end portion of the rod25acomes into contact with the second piston22. The rear portion of the rod25aprotrudes from the rear surface102bof the base body100toward the rear side.

Between the outer circumferential surface of the rear portion of the rod25aand the inner circumferential surface of the nut member25b, a ball screw mechanism is provided. Also, the nut member25bis supported on the base body100with a bearing interposed therebetween.

If the output shaft24arotates, the rotation drive force of the output shaft is input to the nut member25bby the driving pulley24b, the belt25d, and the driven pulley25c. Then, the ball screw mechanism provided between the nut member25band the rod25aapplies the axial force of the straight line direction to the rod25a, whereby the rod25amoves forward and backward in the front-rear direction.

When the rod25amoves forward, the second piston22slides inside the second cylinder bore21in response to the input from the rod25a, thereby pressing the brake fluid contained in the pressure chamber26.

Now, the hydraulic passages formed in the base body100will be described.

As shown inFIG. 1, two main hydraulic passages2aand2bare hydraulic passages starting from the first cylinder bore11of the master cylinder10.

The first main hydraulic passage2aextends from the bottom side pressure chamber16aof the master cylinder10to two wheel brakes BR and BR through the hydraulic pressure control device30.

The second main hydraulic passage2bextends from the opening side pressure chamber16bof the master cylinder10to the other two wheel brakes BR and BR through the hydraulic pressure control device30.

The hydraulic branch passage3is a hydraulic passage extending from the pressure chamber45of the stroke simulator40to the second main hydraulic passage2b. On the hydraulic branch passage3, a normally closed type solenoid valve8is provided. The normally closed type solenoid valve8is for opening or closing the hydraulic branch passage3.

Two connection passages5aand5bstart from the second cylinder bore21of the slave cylinder20. The two connection passages5aand5bare connected to the second cylinder bore21by a common hydraulic passage4.

The first connection passage5ais a flow passage extending from the pressure chamber26formed inside the second cylinder bore21to the first main hydraulic passage2a, and the second connection passage5bis a flow passage extending from the pressure chamber26to the second main hydraulic passage2b.

On the connection part of the first main hydraulic passage2aand the first connection passage5a, a first changeover valve51which is a three-way valve is provided. The first changeover valve51is a two-position three-port type solenoid valve.

When the first changeover valve51is at a first position shown inFIG. 1, the upstream side of the first main hydraulic passage2a(close to the master cylinder10) and the downstream side thereof (close to the wheel brakes BR) are connected, and the first main hydraulic passage2aand the first connection passage5aare disconnected.

When the first changeover valve51is at a second position, the upstream side and downstream side of the first main hydraulic passage2aare disconnected, and the first connection passage5aand the downstream side of the first main hydraulic passage2aare connected.

On the connection portion of the second main hydraulic passage2band the second connection passage5b, a second changeover valve52which is a three-way valve is provided. The second changeover valve52is a two-position three-port type solenoid valve.

When the second changeover valve52is at a first position shown inFIG. 1, the upstream side of the second main hydraulic passage2b(close to the master cylinder10) and the downstream side thereof (close to the wheel brakes BR) are connected, and the second main hydraulic passage2band the second connection passage5bare disconnected.

When the second changeover valve52is at a second position, the upstream side and downstream side of the second main hydraulic passage2bare disconnected, and the second connection passage5band the downstream side of the second main hydraulic passage2bare connected.

On the first connection passage5a, a first shutoff valve61is provided. The first shutoff valve61is a normally open type solenoid valve. If electric power is supplied to the first shutoff valve61, whereby the first shutoff valve is closed, the first connection passage5ais blocked by the first shutoff valve61.

On the second connection passage5b, a second shutoff valve62is provided. The second shutoff valve62is a normally open type solenoid valve. If electric power is supplied to the second shutoff valve62, whereby the second shutoff valve is closed, the second connection passage5bis blocked by the second shutoff valve62.

Two pressure sensors6and7are for detecting the magnitude of the brake hydraulic pressure, and information acquired by the two pressure sensors6and7is output to the electronic control device90.

The first pressure sensor6is disposed on the upstream side from the first changeover valve51, and detects the brake hydraulic pressure generated by the master cylinder10.

The second pressure sensor7is disposed on the downstream side from the second changeover valve52. When the two connection passages5aand5band the downstream sides of the two main hydraulic passages2aand2bare connected, the second pressure sensor detects the brake hydraulic pressure generated by the slave cylinder20.

A supply passage73for the slave cylinder is a fluid passage extending from the reservoir tank80to the slave cylinder20. Also, the supply passage73for the slave cylinder is connected to the common hydraulic passage4by a branch supply passage73a.

On the branch supply passage73a, a check valve75is provided to allow only a flow of the brake fluid from the reservoir tank80toward the common hydraulic passage4.

Normally, the brake fluid is supplied from the reservoir tank80to the slave cylinder20through the supply passage73for the slave cylinder.

Also, during fluid suction control, the brake fluid is sucked from the reservoir tank80into the slave cylinder20through the supply passage73for the slave cylinder, the branch supply passage73a, and the common hydraulic passage4.

A return fluid passage74is a fluid passage extending from the hydraulic pressure control device30to the reservoir tank80. The brake fluid released from the wheel cylinders W flows into the return fluid passage74through the hydraulic pressure control device30. The brake fluid released into the return fluid passage74returns to the reservoir tank80through the return fluid passage74.

The hydraulic pressure control device30is for appropriately controlling the hydraulic pressure of the brake fluid to act on the wheel cylinders W of the wheel brakes BR. The hydraulic pressure control device30has a configuration capable of performing antilock brake control. The wheel cylinders W are connected to outlet ports301of the base body100by pipes, respectively.

The hydraulic pressure control device30can increase, hold, or decrease the hydraulic pressure (hereinafter, referred to as the “wheel cylinder pressure”) to act on the wheel cylinders W. The hydraulic pressure control device30includes inlet valves31, outlet valves32, and check valves33.

The inlet valves31are disposed on two hydraulic passages extending from the first main hydraulic passage2ato two wheel brakes BR and BR and two hydraulic passages extending from the second main hydraulic passage2bto two wheel brakes BR and BR, on a one-to-one basis, respectively.

The inlet valves31are normally opened type proportional solenoid valves (linear solenoid valves), and are valves configured such that it is possible to adjust valve opening pressures of the inlet valves31according to the values of currents flowing in coils of the inlet valves31.

Normally, since the inlet valves31are open, they allow the hydraulic pressure to be applied from the slave cylinder20to the wheel cylinders W. Also, when the wheels are about to be locked, the inlet valves31are closed by control of the electronic control device90, whereby application of the hydraulic pressure to the wheel cylinders W is interrupted.

The outlet valves32are normally closed type solenoid valves disposed between the wheel cylinders W and the return fluid passage74.

Although the outlet valves32are normally closed, when the wheels are about to be locked, the outlet valves are opened by control of the electronic control device90.

The check valves33are connected in parallel to the inlet valves31, respectively. The check valves33are valves allowing only flows of the brake fluid from the wheel cylinders W toward the slave cylinder20(the master cylinder10). Therefore, even when the inlet valves31are closed, the check valves33allow flows of the brake fluid from the wheel cylinders W toward the slave cylinder20.

The electronic control device90includes a housing91which is a resin box, and a control board94(seeFIG. 10) contained in the housing91. As shown inFIG. 2, the housing91is attached to a right surface101dof the base body100.

As shown inFIG. 1, the electronic control device90controls an operation of the motor24and opening and closing of each valve, on the basis of information acquired from various sensors such as the two pressure sensors6and7and a stroke sensor77(seeFIG. 8), programs stored in advance, and so on.

Now, an operation of the brake system A for a vehicle will be described in brief.

In the brake system A for a vehicle shown inFIG. 1, if the system is activated, the two changeover valves51and52are excited, thereby being switched from the first positions to the second positions.

As a result, the downstream side of the first main hydraulic passage2ais connected to the first connection passage5a, and the downstream side of the second main hydraulic passage2bis connected to the second connection passage5b. Therefore, the master cylinder10and the wheel cylinders W are disconnected, and the slave cylinder20and the wheel cylinders W are connected.

Also, if the system is activated, the normally closed type solenoid valve8of the hydraulic branch passage3is opened. As a result, the hydraulic pressure generated by the master cylinder10in response to an operation on the brake pedal P is transmitted to the stroke simulator40, without being transmitted to the wheel cylinders W.

Therefore, the hydraulic pressure of the pressure chamber45of the stroke simulator40increases, whereby the third piston42moves toward the lid member44against the biasing forces of the coil springs43aand43b. In this way, a stroke on the brake pedal P is allowed, and a pseudo operation reaction force is applied to the brake pedal P.

Also, if the stroke sensor77(FIG. 8) detects depression of the brake pedal P, the electronic control device90drives the motor24of the slave cylinder20, whereby the second piston22of the slave cylinder20moves toward the bottom surface21a. As a result, the brake fluid contained in the pressure chamber26is pressed.

The electronic control device90compares the hydraulic pressure generated by the slave cylinder20(the hydraulic pressure detected by the second pressure sensor7) with a requirement hydraulic pressure corresponding to the amount of operation on the brake pedal P, and controls the rotation speed of the motor24on the basis of the comparison result.

In this way, the brake system A for a vehicle increases the hydraulic pressure in response to the amount of operation on the brake pedal P. Also, the hydraulic pressure generated by the slave cylinder20is applied to the hydraulic pressure control device30.

If depression of the brake pedal P is released, the electronic control device90reversely rotates the motor24of the slave cylinder20, whereby the second piston22is moved back toward the motor24by the coil spring23. As a result, the internal pressure of the pressure chamber26decreases.

Also, in a case where a detection value of the second pressure sensor7does not increase to a determination value although the motor24of the slave cylinder20rotates, the electronic control device90closes the two shutoff valves61and62, and drives the slave cylinder20such that the slave cylinder20increases the hydraulic pressure.

Even then, if the detection value of the second pressure sensor7does not increase, since there is a possibility that the brake fluid is leaking from any passage positioned on the slave cylinder20, the electronic control device90controls the individual valves such that the hydraulic pressure directly acts from the master cylinder10on the wheel cylinders W.

Also, when the two shutoff valves61and62are closed, and the slave cylinder20operates to increase the hydraulic pressure, if the detection value of the second pressure sensor7increases, the electronic control device90closes the first shutoff valve61, and opens the second shutoff valve62, and drives the slave cylinder20such that the slave cylinder increases the hydraulic pressure.

As a result, if the detection value of the second pressure sensor7increases, since there is a possibility that the brake fluid would be leaking from the first main hydraulic passage2a, the electronic control device90keeps on driving the slave cylinder20such that the hydraulic pressure in the second main hydraulic passage2bincreases.

Meanwhile, even if the first shutoff valve61is closed and the second shutoff valve62is opened and the slave cylinder20operates to increase the hydraulic pressure, if the detection value of the second pressure sensor7does not increase, the electronic control device90opens the first shutoff valve61, and closes the second shutoff valve62, and drives the slave cylinder20such that the hydraulic pressure increases.

As a result, in a case where the detection value of the second pressure sensor7increases, since there is a possibility that the brake fluid is leaking from the second main hydraulic passage2b, the electronic control device90keeps on driving the slave cylinder20such that the hydraulic pressure in the first main hydraulic passage2aincreases.

In the hydraulic pressure control device30, the electronic control device90controls the open/closed states of the inlet valves31and the outlet valves32, whereby the wheel cylinder pressure of the wheel cylinders W are adjusted.

For example, in a normal state in which the inlet valves31are open and the outlet valves32are closed, if the brake pedal P is depressed, the hydraulic pressure generated by the slave cylinder20is transmitted to the wheel cylinders W without change, whereby the wheel cylinder pressure increases.

Meanwhile, in a state in which the inlet valves31are closed and the outlet valves32are open, the brake fluid flows from the wheel cylinders W toward the return fluid passage74, whereby the wheel cylinder pressure decreases, whereby the hydraulic pressure decreases.

Also, in a state in which all of the inlet valves31and the outlet valves32are closed, the wheel cylinder pressure is held.

Also, in a state where the slave cylinder20does not operate (for example, in a case where an ignition is in an OFF state or electric power is not supplied), the first changeover valve51, the second changeover valve52, and the normally closed type solenoid valve8return to their initial states. As a result, the upstream side and downstream side of each of the main hydraulic passages2aand2bare connected. In this state, the hydraulic pressure generated by the master cylinder10is transmitted to the wheel cylinders W through the hydraulic pressure control device30.

Now, the arrangement of the master cylinder10, the slave cylinder20, the stroke simulator40, the hydraulic pressure control device30, and the electronic control device90included in the hydraulic pressure generating device1will be described.

Also, in the following description, the arrangement of those devices in a state where the hydraulic pressure generating device1is mounted on a vehicle will be described.

An upper portion101of the base body100is formed substantially in a cuboid shape as shown inFIGS. 2 and 3. In the upper portion10, the first cylinder bore11and the third cylinder bore41are formed as shown inFIG. 7. On the upper surface101eof the upper portion101, the reservoir tank80is attached as shown inFIG. 2.

At the central portion of the upper portion101of the base body100in a vertical direction and the left-right direction, as shown inFIG. 5, the first cylinder bore11of the master cylinder10is formed (seeFIG. 6).

The first cylinder bore11is a cylindrical bore with a bottom. The axial line L1of the first cylinder bore11extends in the front-rear direction as shown inFIG. 7. The rear end portion of the first cylinder bore11is formed in the rear surface101bof the upper portion101. In other words, the first cylinder bore11is open toward the rear side.

The rear surface101bof the upper portion101of the base body100has a vehicle contact surface104as shown inFIG. 4. The vehicle contact surface104is a portion to be attached to the front surface of a dashboard B partitioning an engine room and the interior of the vehicle.

At the central portion of the vehicle contact surface104, the opening11bof the first cylinder bore11is formed as shown inFIG. 5. Also, from four corners of the vehicle contact surface104, that is, the upper, lower, left, and right thereof, four stud bolts105protrude.

When the base body100is attached to the dashboard B, as shown inFIG. 4, the stud bolts105are inserted from the engine side (the left side ofFIG. 4) into mounting holes (not shown in the drawings) of the dashboard B. Further, inside the vehicle (the right side ofFIG. 4), the leading end portions of the stud bolts105are attached to the vehicle frame (not shown in the drawings). In this way, it is possible to fix the base body100to the front surface of the dashboard B.

In a portion of the upper portion101of the base body100positioned on the left side from the first cylinder bore11, as shown inFIG. 5, the third cylinder bore41of the stroke simulator40is formed (seeFIG. 6).

The third cylinder bore41is a cylindrical bore with a bottom. As shown inFIG. 7, the axial line L3of the third cylinder bore41extends in the front-rear direction.

The axial line L3of the third cylinder bore41is parallel to the axial line L1of the first cylinder bore11. Like this, the first cylinder bore11and the third cylinder bore41are disposed side by side in parallel.

As shown inFIG. 6, the axial line L3of the third cylinder bore41and the axial line L1of the first cylinder bore11are arranged side by side in the left-right direction on a horizontal reference plane S1(a virtual plane).

The third cylinder bore41is formed in the rear surface101bof the upper portion101of the base body100. In other words, the third cylinder bore41is open toward the rear side.

An almost half left portion of the peripheral wall portion of the third cylinder bore41protrudes from a left surface101cof the upper portion101toward the left side as shown inFIG. 3.

As shown inFIG. 6, a lower portion102of the base body100is formed to be connected to the upper portion101and protrude toward the right side from the right surface101dof the upper portion101. Also, the left surface101cof the lower portion102is positioned on the right side from the left surface101cof the upper portion101with an offset.

The rear surface102bof the lower portion102is positioned on the front side from the rear surface101b(the vehicle contact surface104) of the upper portion101with an offset as shown inFIG. 7. Also, a front portion102aof the lower portion102protrudes from a front surface101aof the upper portion101toward the front side.

In the lower portion102of the base body100, as shown inFIG. 5, the second cylinder bore21of the slave cylinder20is formed (seeFIG. 6).

The second cylinder bore21is a cylindrical bore with a bottom. As shown in FIG.7, the axial line L2of the second cylinder bore21extends in the front-rear direction.

As shown inFIG. 6, the second cylinder bore21is disposed on the lower side from the first cylinder bore11and the third cylinder bore41, and the second cylinder bore21is disposed on the diagonally right lower side.

As shown inFIG. 7, the axial line L2of the second cylinder bore21is parallel to the axial line L1of the first cylinder bore11and the axial line L3of the third cylinder bore41. Like this, the first cylinder bore11, the second cylinder bore21, and the third pattern area23are arranged side by side in parallel.

The second cylinder bore21is formed in the rear surface102bof the lower portion102of the base body100. In other words, the second cylinder bore21is open toward the rear side.

In the rear end portion of the lower portion102of the base body100, as shown inFIG. 6, the flange portion103is formed so as to protrude toward the left side. The flange portion103is a plate-like portion perpendicularly protruding from a left surface102cof the lower portion102.

As shown inFIG. 4, the front surface of the flange portion103is a motor mounting surface103afor mounting the motor24. Also, the rear surface of the flange portion103is a drive-transmission-unit mounting surface103bfor mounting the drive transmission unit25.

The drive-transmission-unit mounting surface103bof the flange portion103is formed so as to be connected to the rear surface102bof the lower portion102on the same plane. Further, similarly to the rear surface102bof the lower portion102, the drive-transmission-unit mounting surface103bis disposed on the front side from the rear surface101bof the upper portion101with an offset. In other words, the drive-transmission-unit mounting surface103bis disposed on the front side from the vehicle contact surface104of the upper portion101.

On the motor mounting surface103aof the flange portion103, the motor24is attached. The front end surface of the motor24is disposed on the rear side from the front surface101aof the upper portion101of the base body100. The motor24is disposed at a position close to the center of the base body100in the front-rear direction and the left-right direction.

In the flange portion103, an insertion hole103cis formed in the front-rear direction. The output shaft24aprotruding from the rear surface of the motor24toward the rear side is inserted into the insertion hole103cso as to protrude from the drive-transmission-unit mounting surface103btoward the rear side through the insertion hole103c.

As shown inFIG. 6, the insertion hole103cof the flange portion103is disposed on the lower side from the first cylinder bore11and the third cylinder bore41and on the diagonally left lower side from the first cylinder bore11.

Therefore, if the motor24is attached to the flange portion103, as shown inFIG. 5, the output shaft24ais disposed on the lower side from the first cylinder bore11and the third cylinder bore41and on the diagonally left lower side from the first cylinder bore11.

In a state where the motor24is mounted on the flange portion103, as shown inFIG. 4, an axial line L4of the output shaft24aextends in the front-rear direction.

The axial line L4of the output shaft24ais parallel to the axial lines L1, L2, and L3of the cylinder bores11,21, and41. Like this, the cylinder bores11,21, and41and the output shaft24aare disposed side by side in parallel.

Also, as shown inFIG. 5, the axial line L4of the output shaft24aand the axial line L2of the second cylinder bore21are disposed side by side in the left-right direction.

As shown inFIG. 1, on the rear surface102bof the lower portion102of the base body100and the drive-transmission-unit mounting surface103bof the flange portion103, components of the drive transmission unit25are assembled.

As shown inFIG. 4, the offsets of the rear surface102bof the lower portion102and from the drive-transmission-unit mounting surface103bof the flange portion103from the vehicle contact surface104toward the front side are set such that the rear end portion of the cover member25eof the drive transmission unit25does not protrude from the vehicle contact surface104of the upper portion101toward the rear side.

Therefore, when the vehicle contact surface104of the base body100is mounted on the dashboard B, the drive transmission unit25is positioned between the front surface of the dashboard B and the drive-transmission-unit mounting surface103bof the flange portion103of the base body100.

In the right surface101dof the upper portion101of the base body100, as shown inFIG. 7, a plurality of mounting holes110for mounting the various solenoid valves51,52,61,62,8,31, and32(seeFIG. 1) and the two pressure sensors6and7(seeFIG. 1) is formed. However,FIG. 7schematically shows the positions and sizes of the mounting holes110.

On the right surface101dof the upper portion101, the housing91of the electronic control device90is attached as shown inFIG. 2. The various solenoid valves51,52,61,62,8,31, and32(seeFIG. 1) and the two pressure sensors6and7(seeFIG. 1) mounted in the mounting holes110(seeFIG. 7) are covered by the housing91.

The housing91is disposed on the second cylinder bore21. Like this, the housing91and the slave cylinder20are disposed on the right side of the upper portion101of the base body100, side by side in the vertical direction (seeFIG. 5).

As shown inFIG. 3, the front end portion of the housing91protrudes toward the front side from the front surface101aof the upper portion101of the base body100. On the right surface of the front portion of the housing91, an external connection connector92and a motor connection connector93are provided.

The external connection connector92is a part to be connected with a connector provided at an end portion of an external wiring cable (not shown in the drawings). The external connection connector92extends toward the front side from the front surface101aof the upper portion101.

The motor connection connector93is disposed below the external connection connector92. The motor connection connector93is a part to be connected with a motor connector24cof the motor24by a cable (not shown in the drawings).

In the hydraulic pressure generating device1of the present embodiment, as shown inFIG. 5, the second cylinder bore21and the motor24(the output shaft24a) are disposed below the horizontal reference plane S1(the virtual plane) including the axial line L1of the first cylinder bore11and the axial line L3of the third cylinder bore41.

Also, the third cylinder bore41and the motor24(the output shaft24a) are disposed on the left side from a vertical reference plane S2(a virtual plane) including the axial line L1of the first cylinder bore11. Further, the second cylinder bore21is disposed on the right side from the vertical reference plane S2including the axial line L1of the first cylinder bore11.

As described above, in the hydraulic pressure generating device1, below the first cylinder bore11, the second cylinder bore21and the motor24are disposed on the right and left of the vertical reference plane S2including the axial line L1of the first cylinder bore11, respectively.

Therefore, as the hydraulic pressure generating device1is seen from the front-rear direction, the center point of the first cylinder bore11(the axial line L1), the center point of the second cylinder bore21(the axial line L2), and the center point of the output shaft24a(the axial line L4) are disposed such that a line connecting them forms a triangle. In other words, as the hydraulic pressure generating device1is seen from the front-rear direction, the first cylinder bore11(the master cylinder10) is disposed at the apex of the triangle, and the second cylinder bore21(the slave cylinder20) and the output shaft24a(the motor24) are disposed at the left and right ends of the base of the triangle.

In the hydraulic pressure generating device1configured as described above, as shown inFIG. 4, the axial lines L1, L2, and L3of the cylinder bores11,21, and41and the axial line L4of the output shaft24aof the motor24are disposed in parallel, such that the cylinder bores11,21, and41and the motor24are disposed with good balance. As a result, the size of the hydraulic pressure generating device1decreases.

In the hydraulic pressure generating device1of the present embodiment, as shown inFIG. 5, the slave cylinder20and the motor24are disposed below the master cylinder10, and the slave cylinder20and the motor24are disposed on the right and left of the master cylinder10, respectively. Therefore, the gravity center of the hydraulic pressure generating device1is low. Especially, since the motor24is a heavy component, the motor is disposed at a lowest portion of the hydraulic pressure generating device1, whereby it is possible to stabilize the weight balance of the master cylinder10, the slave cylinder20, and the motor24, and it is possible to effectively improve the stability of the hydraulic pressure generating device1.

In the hydraulic pressure generating device1of the present embodiment, the housing91and the slave cylinder20are disposed side by side in the vertical direction, and a space around the base body100is effectively used. Therefore, the hydraulic pressure generating device1has a smaller size.

In the hydraulic pressure generating device1of the present embodiment, since the first cylinder bore11and the third cylinder bore41are adjacent to each other in the left-right direction, it is easy to connect the master cylinder10to the stroke simulator40. Also, since the master cylinder10and the stroke simulator40are disposed compactly, it is possible to further reduce the size of the hydraulic pressure generating device1.

Now, the stroke sensor77of the present embodiment will be described.

FIG. 8is a right side view illustrating the hydraulic pressure generating device1without a cover95and the control board94.FIG. 9is an enlarged view of a portion ofFIG. 8including the stroke sensor77.FIG. 10is a cross-sectional view taken along a line IX-IX ofFIG. 8. However, inFIG. 10, the cover95and the control board94are also shown.

As shown inFIG. 10, the housing91is attached to the right surface101dof the base body100with a sealing member106interposed therebetween. The housing91has a peripheral wall portion91awhich surrounds various components such as the control board94functioning as the electronic control device90and the solenoid valves V (a general term for the valves51,52,61,62,8,31, and32(seeFIG. 1)).

On the right edge of an opening of the peripheral wall portion91a, the cover95is attached with a sealing member107interposed therebetween. The cover95is made of a metal member, for example, an aluminum member.

As shown inFIG. 8, the inner surface of the front side of the peripheral wall portion91ais connected to a mounting wall portion91d, and on the mounting wall portion91d, various components such as a noise removal coil901and a capacitor902are attached.

As shown inFIG. 10, on the front side of the first piston12b, a hole12cis formed. Inside the hole12c, a magnet78is contained as a detection object member. The magnet78has a columnar shape. However, the present invention is not limited thereto. For example, the magnet may have a cylindrical shape. The magnet78is pushed toward the rear side by the coil spring17b, with a retainer interposed therebetween. In other words, the magnet78is held inside the hole12c. Therefore, as the first piston12bslides, the magnet78moves in the front-rear direction along the axial line L1of the first cylinder bore11.

As shown inFIGS. 8 to 10, the inner surface of the rear side of the peripheral wall portion91aof the housing91is connected to a facing wall portion91bformed in parallel to the right surface101dof the base body100. The facing wall portion91bfaces the right surface101dof the base body100.

In order to bring the left edge of the opening of the peripheral wall portion91ainto close contact with the right surface101dof the base body100, it is preferable to form a slight gap between the facing wall portion91band the right surface101d. However, the facing wall portion91bmay be in contact with the right surface101d. Alternatively, the facing wall portion91band the right surface101dmay be separated as long as the stroke sensor77can detect the magnet78.

The stroke sensor77is installed inside the housing91. Between the stroke sensor77and the base body100, the facing wall portion91bis disposed. Further, the stroke sensor77is electrically connected to the control board94. Also, from the facing wall portion91b, a surrounding wall91cfor surrounding the stroke sensor77protrudes.

The stroke sensor77faces the magnet78with the facing wall portion91band the peripheral walls of the base body100and the first piston12binterposed therebetween. The stroke sensor77is close to the right surface101dof the base body100, and is closest to the magnet78inside the housing91. Therefore, the stroke sensor77has a shortest distance from the magnet78inside the housing91.

This stroke sensor77detects a stroke for sliding the first piston12b(the amount of movement of the first piston) by detecting the magnet78. The amount of movement of the first piston12bcorresponds to the amount of operation on the brake pedal P. Specifically, if the magnet78moves along the axial line L1in tandem with the rod P1of the brake pedal P, the stroke sensor77detects change in magnetic field lines of the magnet78.

Also, although the stroke sensor77partially faces the magnet78with the facing wall portion91band the peripheral walls of the base body100and the first piston12binterposed therebetween (seeFIG. 10), the present invention is not limited thereto. For example, when the brake pedal P is at its origin position, that is, when the master cylinder10is at its initial position, the stroke sensor77may not face the magnet78with the facing wall portion91band the like interposed therebetween.

The stroke sensor77includes a detection element77afor detecting the magnet78, and a sensor board77bhaving the detection element77athereon. As the detection element77a, for example, a Hall IC can be used.

In the housing91, a plurality of (in the present embodiment, four) bus bars96is installed as conductive members for connecting the sensor board77band the control board94(seeFIG. 9). A portion of each bus bar96is buried in the facing wall portion91bof the housing91. In other words, the housing91is formed integrally with the bus bars96.

Both end portions of each bus bar96have male terminals96aand96b, respectively. The male terminals96aprovided at the end portions of the bus bars96positioned close to the sensor board77bare inserted into female terminals77c(seeFIG. 9) provided on the sensor board77bby pressing (for example, press fitting). The sensor board77bis fixed to the male terminals96a. Meanwhile, the male terminals96bprovided at the end portions of the bus bars96positioned close to the control board94are inserted into female terminals provided on the control board94. The control board94is fixed to the male terminals96b.

On the right surface101dof the base body100, the plurality of solenoid valves V and the housing91are attached. The extension direction of the male terminals96aof the bus bars96positioned close to the sensor board77bis parallel to the central axes of the solenoid valves V. Also, the male terminals96aof the bus bars96positioned close to the sensor board77bextend in a direction from the base body100toward the control board94, and are connected to the female terminals77cof the sensor board77b.

The male terminals96aof the plurality of bus bars96are distributed substantially uniformly around the sensor board77b. Therefore, the sensor board77bis stably held by the plurality of male terminals96a.

As described above, in the hydraulic pressure generating device1of the present embodiment, the stroke sensor77is installed inside the housing91on the opposite side of the facing wall portion91bto the base body100, and is electrically connected to the control board94. Therefore, an input attributable to an operator's operation on the brake can be detected by the stroke sensor77contained in the housing91. Also, a signal detected by the stroke sensor77is input directly to the control board94. As described above, the stroke sensor77is contained in the housing91attached to the base body100. Therefore, it becomes possible to reduce the size of the base body100even though the stroke sensor77is included, and it is possible to achieve an advantage that it is easy to secure a space for mounting the hydraulic pressure generating device on a vehicle.

Also, a portion of the stroke sensor77positioned close to the base body100is covered by the facing wall portion91b. Therefore, for example, during maintenance, when a worker attaches or detaches the housing91to or from the base body100, it is possible to suppress the fingers of the worker from touching the stroke sensor77, other components, and so on. Further, it is possible to suppress entry of external foreign materials by the facing wall portion91b, and it is possible to provide a dust proofing function. Since the stroke sensor77is protected by the facing wall portion91bas described above, it is possible to secure detection accuracy and durability, and it is possible to improve reliability.

In other words, according to the present embodiment, it is possible to provide the hydraulic pressure generating device1making it easier to secure a space for mounting the hydraulic pressure generating device on a vehicle and capable of protecting the stroke sensor77.

Further, since the hydraulic pressure generating device1includes the stroke sensor77, as compared to a case where the stroke sensor77is configured separately from the hydraulic pressure generating device1, it is unnecessary to separately provide the stroke sensor77and form signal lines. For this reason, assembling man-hours when the hydraulic pressure generating device1is mounted on a vehicle decrease, and the number of components decreases. Therefore, it is possible to reduce the manufacturing cost.

Also, in the present embodiment, the sensor board77bis fixed to the bus bars96. According to this configuration, since the sensor board77bis fixed by the bus bars96, the stroke sensor77does not need to be contained, for example, inside a resin mold component, and also does not need connectors for connection. Therefore, the configuration of the stroke sensor77is simplified, and the cost decreases.

Also, in the present embodiment, in a state where the male terminals96aof the bus bars96are inserted in the female terminals77cprovided on the sensor board77b, the sensor board77bis fixed to the bus bars96. According to this configuration, since the male terminals96aare inserted into the female terminals77c, it is possible to fix the sensor board77bby pressing (for example, press fitting).

However, male terminals provided on the sensor board77bmay be inserted into female terminals provided at the end portions of the bus bars96positioned close to the sensor board77b.

Also, in the present embodiment, a portion of each bus bar96is buried in the facing wall portion91bof the housing91. Therefore, it is possible to stably and securely fix the bus bars96to the housing91by the facing wall portion91b. As a result, the male terminals96aprovided at the end portions of the bus bars96are precisely positioned. Therefore, it becomes easier to connect the sensor board77bto the male terminals96aof the bus bars96, and the electrical connection of the bus bars96with the sensor board77bbecomes securer.

Also, in the present embodiment, the extension direction of the male terminals96aof the bus bars96is disposed in parallel to the central axes of the solenoid valves V. Therefore, it is possible to move the sensor board77bof the stroke sensor77in the same direction as the direction in which the solenoid valves V are attached to the base body100, and connect the sensor board to the male terminals96aof the bus bars96. Therefore, it is possible to efficiently install the stroke sensor77.

Also, in the present embodiment, the male terminals96aof the bus bars96extend in the direction from the base body100toward the control board94, and are connected to the female terminals of the sensor board77b. For this reason, it is possible to move the sensor board77bof the stroke sensor77in the same direction as the direction in which the control board94is attached to the inside of the housing91, and connect the sensor board to the male terminals96aof the bus bars96. Therefore, it is possible to efficiently install the stroke sensor77.

Also, in the present embodiment, the housing91has the surrounding wall91cprotruding from the facing wall portion91band surrounding the stroke sensor77. According to this configuration, the stroke sensor77is covered and protected by the facing wall portion91band the surrounding wall91c. Therefore, it is possible to further improve the reliability of the stroke sensor77.

Although the present invention has been described above on the basis of the embodiment, the present invention is not limited to the components described with respect to the embodiment, and it is possible to appropriately modify the components without departing from the gist of the present invention. Also, with respect to some of the components of the embodiment, it is possible to make additions, omissions, and replacements.

For example, the stroke sensor77may be fixed to the housing91. According to this configuration, it is possible to securely prevent the stroke sensor77from unexpectedly moving. Therefore, it is possible to further improve the reliability of the stroke sensor77.

In a case of fixing the stroke sensor77to the housing91, the stroke sensor77may be buried in a resin fixed on the facing wall portion91bof the housing91. In this case, in a space surrounded by the facing wall portion91band the surrounding wall91c, for example, a bonding adhesive composed of a resin material may be filled and hardened. According to this configuration, it is possible to easily and securely the stroke sensor77to the housing91, and since the whole of the stroke sensor77is covered by the resin, the stroke sensor is more securely protected.

Also, in a case of fixing the stroke sensor77to the housing91, for example, the sensor board77bmay be fastened to the housing91by screws. Also, the connection of the bus bars96and the sensor board77bis not limited to press fitting. For example, they may be connected by wire bonding or the like.

Also, the second cylinder bore21and the output shaft24amay be disposed above the first cylinder bore11. Also, the motor24may be disposed such that the output shaft24aprotrudes from the motor24toward the front side. Also, the housing91may be disposed below the second cylinder bore21. Also, the master cylinder10may be configured by a single piston type cylinder. Also, the slave cylinder20may be configured by a tandem piston type cylinder. Also, from among the master cylinder10, the stroke simulator40, the slave cylinder20, and the hydraulic pressure control device30, only two devices, that is, the master cylinder10and the slave cylinder20may be provided on the base body100.

Also, in the above-described embodiment, the axial lines L1, L2, and L3of the cylinder bores11,21, and41and the axial line L4of the output shaft24aof the motor24are disposed in parallel. However, the present invention is not limited thereto. For example, the axial lines L1, L2, L3, and L4may be disposed in parallel. Here, when axial lines are referred to as being parallel to each other, the axial lines may be strictly parallel to each other, or the axial lines may be almost parallel to each other. Further, the present invention can be applied, for example, even to a case where the axial line L1of the first cylinder bore11and the axial line L2of the second cylinder bore21are perpendicular to each other.