JP4801823B2 - Initial position setting method for electric cylinder for generating hydraulic pressure - Google Patents

Description

According to the present invention, a piston that is slidably fitted to a cylinder body in which a hydraulic chamber having an input port and an output port is formed is driven forward via a feed screw mechanism that is operated by an electric motor, and the piston is The present invention relates to an initial position setting method in an electric cylinder for generating hydraulic pressure, in which hydraulic pressure generated in the hydraulic pressure chamber by passing through an input port is output from the output port.

A so-called BBW (brake-by-wire) that converts a driver's braking operation into an electric signal, operates an electric hydraulic pressure generating means (slave cylinder), and operates a wheel cylinder with a brake hydraulic pressure generated by the slave cylinder. ) Type brake device is known from US Pat.
Japanese Patent Laid-Open No. 2007-230435

  By the way, the above-mentioned conventional BBW type brake device drives a piston of a slave cylinder through a ball screw mechanism with an electric motor, and brakes the hydraulic chamber at the moment when the piston passes through the input port of the hydraulic chamber. Hydraulic pressure is generated. Therefore, in order to increase the response of the brake fluid pressure generation, the piston is positioned at the initial position immediately after the input port when not operated, and immediately after the electric motor is activated and the piston starts moving forward, the fluid pressure chamber It is desirable to generate brake fluid pressure.

  However, the above conventional one regulates the backward limit of the piston biased in the backward direction by the return spring by bringing the rear end of the male screw member of the ball screw mechanism into contact with the inner wall surface of the housing. During operation, the piston could not be positioned in the initial position immediately after the input port. This is because the initial position of the piston also varies due to variations in the dimensions of each member of the slave cylinder, so the piston must be stopped with sufficient margin behind the input port when it is not in operation. This is because there is a possibility of blocking the input port.

The present invention has been made in view of the above circumstances, and in a hydraulic pressure generating electric cylinder that generates a hydraulic pressure in a hydraulic pressure chamber by driving a piston forward by an electric motor, the responsiveness of generating the hydraulic pressure is enhanced. Objective.

In order to achieve the above object, according to the first aspect of the present invention, the front piston and the rear piston that are aligned in the front-rear direction are slidably fitted in the cylinder body, and the front portion A front hydraulic chamber is defined on the front side of the piston, and a rear hydraulic chamber is defined between the front and rear pistons. The front input port and the output port open to the front hydraulic chamber, and the rear hydraulic pressure. A rear input port and an output port that open to the chamber are formed in the cylinder body. Between the cylinder body and the front piston, a front return spring that urges the front piston rearward, and a front and rear part Between the pistons, there is provided a rear return spring that connects between the pistons and urges the rear piston backward, and a male screw member whose front end abuts on the rear end of the rear piston, and a screw on the male screw member. A feed screw mechanism having a female screw member to be provided between the electric motor and the rear piston, and through the feed screw mechanism, the electric motor can drive the rear piston at the initial position forward, and according to the forward drive, a initial position setting method definitive a hydraulic generating electric cylinders to be output from the rear output port hydraulic pressure generated in the rear fluid pressure chamber by the rear piston passes the input port of the rear, the electric motor in the male screw member, until said predetermined limit position corresponding to the limit position of the backward direction of the rear piston is moved, first of Ru stops the operation of the electric motor and its externally threaded member (42) reaches a predetermined limit position a step, a second step of storing the rotational position of the electric motor after a predetermined time from deactivation of the electric motor has elapsed, after the lapse of the predetermined time, the By driving only setting rotational speed dynamic motor was previously set in the forward direction from the rotational position described above stored in that it comprises a third step of positioning the rear piston to the initial position immediately after the input port of the rear A characteristic initial position setting method in a hydraulic pressure generating electric cylinder is proposed.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the electric cylinder is used for a brake device of a vehicle, and the first to third steps are performed before the vehicle starts running. In this case, an initial position setting method is proposed in the hydraulic cylinder for generating hydraulic pressure , which is performed before the start of vehicle travel , which is performed every time it is detected that the driver has entered the vehicle .

Incidentally, the ball screw mechanism 35 of the embodiment the corresponding feed screw mechanism of the present invention.

According to the configuration of the first aspect, when setting the initial position in the hydraulic cylinder for generating hydraulic pressure, first , the male screw member of the feed screw mechanism is moved to the predetermined limit position corresponding to the limit position in the backward direction of the rear piston by the electric motor. Then, when the male screw member reaches the predetermined limit position, the operation of the electric motor is stopped, the rotation position of the electric motor is stored after a predetermined time has elapsed since the stop, and the electric motor is stored after the predetermined time has elapsed. the by driving only the set rotational speed set in advance in the forward direction from the rotational position described above storage, since the positioning to the initial position immediately after the rear side of the input port rear piston, a rear piston in an initial position by an electric motor The hydraulic pressure can be generated in the rear hydraulic pressure chamber only by a slight advance, and the response of the hydraulic pressure generation can be enhanced. In addition, since the initial position of the rear piston is set based on the limit position in the backward direction of the piston, the accuracy and reproducibility of the initial position can be improved.

According to the second aspect of the present invention, the electric cylinder generates hydraulic pressure during the first to third steps for positioning the rear piston at the initial position immediately after the rear input port. it is not possible, by performing the time for detecting that boarded the first to third steps in the vehicle Oite driver before the vehicle starts running, the electric cylinder actuating interruption during running of the vehicle Can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1 to 5 show an embodiment of the present invention. FIG. 1 is a hydraulic circuit diagram in a normal state of a vehicle brake device. FIG. 2 is a hydraulic circuit diagram in an abnormal state corresponding to FIG. 3 is a block diagram of the control system, FIG. 4 is a flowchart for explaining the action of setting the initial position of the piston, and FIG. 5 is a diagram showing the limit position on the backward side of the ball screw mechanism.

  As shown in FIG. 1, the tandem master cylinder 11 includes two hydraulic chambers 13A and 13B that output brake hydraulic pressure in accordance with the pedaling force of the driver stepping on the brake pedal 12, and one hydraulic pressure is provided. The chamber 13A is connected to the wheel cylinders 16 and 17 of the disc brake devices 14 and 15 of, for example, the left front wheel and the right rear wheel via liquid passages Pa, Pb, Pc, Pd, and Pe (first system). The hydraulic chamber 13B is connected to the wheel cylinders 20 and 21 of the disc brake devices 18 and 19 of the right front wheel and the left rear wheel, for example, via the fluid paths Qa, Qb, Qc, Qd, and Qe (second system).

  A shutoff valve 22A, which is a normally open solenoid valve, is disposed between the fluid paths Pa, Pb, and a shutoff valve 22B, which is a normally open solenoid valve, is disposed between the fluid paths Qa, Qb, and the fluid paths Pb, Qb and the fluid path. A slave cylinder 23 is disposed between Pc and Qc, and a VSA (vehicle stability assist) device 24 is disposed between the liquid paths Pc and Qc and the liquid paths Pd and Pe; Qd and Qe.

  A stroke simulator 26 is connected to the liquid paths Ra and Rb branched from the liquid path Qa via a reaction force permission valve 25 which is a normally closed solenoid valve. The stroke simulator 26 is a cylinder 27 slidably fitted with a piston 29 urged by a spring 28, and a hydraulic chamber 30 formed on the side opposite to the spring 28 of the piston 29 communicates with a liquid path Rb. To do.

  The actuator 31 of the slave cylinder 23 includes a drive bevel gear 33 provided on the output shaft of the electric motor 32, a driven bevel gear 34 that meshes with the drive bevel gear 33, and a ball screw mechanism 35 that is operated by the driven bevel gear 34. The ball screw mechanism 35 includes a male screw member 42 and a female screw member 43 that are screwed to each other, and a rear end surface 42 a of the male screw member 42 is capable of contacting an inner wall surface 44 a of a housing 44 that houses the actuator 31. opposite.

  A rear piston 38A and a front piston 38B, which are urged in a backward direction by return springs 37A and 37B, are slidably disposed on the rear and front portions of the cylinder body 36 of the slave cylinder 23, respectively. A rear hydraulic chamber 39A and a front hydraulic chamber 39B are defined on the front surface of the front piston 38B. The front end of the male screw member 42 of the ball screw mechanism 35 contacts the rear surface of the rear piston 38A.

  The rear hydraulic chamber 39A communicates with the fluid path Pb via the input port 40A, communicates with the fluid path Pc via the output port 41A, and the front hydraulic chamber 39B communicates with the fluid path Qb via the input port 40B. And the fluid channel Qc via the output port 41B.

  In FIG. 1, when the electric motor 32 is driven in one direction, the rear and front pistons 38A and 38B move forward through the drive bevel gear 33, the driven bevel gear 34, and the ball screw mechanism 35, and enter the liquid paths Pb and Qb. Brake fluid pressure is generated in the rear and front fluid pressure chambers 39A and 39B at the moment when the continuous input ports 40A and 40B are closed, and the brake fluid pressure is output to the fluid paths Pc and Qc via the output ports 41A and 41B. can do.

  The structure of the VSA device 24 is well known. The first brake actuator 51A for controlling the first system of the disc brake devices 14 and 15 for the left front wheel and the right rear wheel, the disc brake device 18 for the right front wheel and the left rear wheel, A second brake actuator 51B that controls the 19 second system is provided with the same structure.

  Hereinafter, as a representative example, the first brake actuator 51A of the first system of the disc brake devices 14 and 15 for the left front wheel and the right rear wheel will be described.

  The first brake actuator 51A includes a fluid path Pc that communicates with the output port 41A of the slave cylinder 23 located on the upstream side, and a fluid path Pd that communicates with the wheel cylinders 16 and 17 for the left front wheel and the right rear wheel located on the downstream side. It arrange | positions between Pe.

  The first brake actuator 51A has a common fluid path 52 and a fluid path 53 for the left front wheel and right rear wheel wheel cylinders 16 and 17, and a variable opening disposed between the fluid path Pc and the fluid path 52. A regulator valve 54 consisting of a normally open solenoid valve, a check valve 55 arranged in parallel to the regulator valve 54 and allowing the brake fluid to flow from the liquid passage Pc side to the liquid passage 52 side, and a liquid passage 52 And an in-valve 56 composed of a normally-open solenoid valve having a variable opening disposed between the liquid passage Pe and a brake fluid flowing from the liquid passage Pe side to the liquid passage 52 side in parallel with the in-valve 56. A check valve 57 that allows for this, an in-valve 58 that is a normally open solenoid valve with a variable opening disposed between the liquid passage 52 and the liquid passage Pd, A check valve 59 that is arranged in parallel with the fluid valve 58 and permits the flow of the brake fluid from the fluid path Pd side to the fluid path 52 side, and a variable opening constant that is disposed between the fluid path Pe and the fluid path 53. An out valve 60 comprising a closed solenoid valve; an out valve 61 comprising a normally closed solenoid valve having a variable opening disposed between the liquid passage Pd and the liquid passage 53; a reservoir 62 connected to the liquid passage 53; A check valve 63 disposed between the liquid passage 53 and the liquid passage 52 to allow the brake fluid to flow from the liquid passage 53 side to the liquid passage 52 side, and a check valve 63 disposed between the check valve 63 and the liquid passage 52. A pump 64 that supplies brake fluid from the 53 side to the fluid path 52 side, an electric motor 65 that drives the pump 64, and between the check valve 63 and the intermediate position of the pump 64 and the fluid path Pc And a suction valve 66 consisting arranged normally closed solenoid valve.

  The electric motor 65 is shared with the pumps 64 and 64 of the first and second brake actuators 51A and 51B. However, dedicated electric motors 65 and 65 are provided for the pumps 64 and 64, respectively. It is also possible to provide it.

  A fluid pressure sensor Sa is provided in the fluid passage Qa connected to the other fluid pressure chamber 13B of the master cylinder 11, and a fluid pressure sensor Sb is provided in the fluid passage Qc connected to the output port 41B of the slave cylinder 23. A wheel speed sensor Sc is provided, and a rotation angle sensor Sd is provided in the electric motor 32 of the slave cylinder 23.

  FIG. 3 is a block diagram of the control system of the brake device described in FIG. 1, and in addition to the hydraulic pressure sensor Sa, the hydraulic pressure sensor Sb, the wheel speed sensor Sc,. The electronic control unit U to which a signal from the door opening / closing switch Se that detects the opening / closing of the side door is input controls the operation of the shutoff valves 22A, 22B, the VSA device 24, the reaction force permission valve 25, and the electric motor 32.

  Next, the operation of the embodiment of the present invention having the above configuration will be described.

  As shown in FIG. 1, when the system functions normally, the shutoff valves 22A and 22B made of normally open solenoid valves are demagnetized and opened, and the reaction force permission valve 25 made of normally closed solenoid valves is excited. It is opened. In this state, when the hydraulic pressure sensor Sa provided in the liquid path Qa detects the depression of the brake pedal 12 by the driver, the actuator 31 of the slave cylinder 23 is operated and the rear and front pistons 38A and 38B move forward. Brake hydraulic pressure is generated in the rear and front hydraulic chambers 39A and 39B. This brake fluid pressure is transmitted to the wheel cylinders 16, 17, 20, and 21 of the disc brake devices 14, 15, 18, and 19 via the opened in valves 56, 56; Braking.

  When the rear and front pistons 38A and 38B of the slave cylinder 23 are slightly advanced, the communication between the fluid passages Pb and Qb and the rear and front hydraulic chambers 39A and 39B is cut off, so that the brake generated by the master cylinder 11 occurs. The hydraulic pressure is not transmitted to the disc brake devices 14, 15, 18, 19. At this time, the brake hydraulic pressure generated in the other hydraulic chamber 13B of the master cylinder 11 is transmitted to the hydraulic chamber 30 of the stroke simulator 26 via the opened reaction force permission valve 25, and the piston 29 is transferred to the spring 28. By moving it against, the stroke of the brake pedal 12 can be allowed and a pseudo pedal reaction force can be generated to eliminate the driver's uncomfortable feeling.

  The brake fluid pressure detected by the slave cylinder 23 detected by the fluid pressure sensor Sb provided in the fluid passage Qc becomes a magnitude corresponding to the brake fluid pressure detected by the master cylinder 11 detected by the fluid pressure sensor Sa provided in the fluid passage Qa. As described above, by controlling the operation of the actuator 31 of the slave cylinder 23, it is possible to cause the disc brake devices 14, 15, 18, and 19 to generate a braking force corresponding to the pedaling force input to the brake pedal 12 by the driver.

  Next, the operation of the VSA device 24 will be described.

  When the driver steps on the brake pedal 11 to perform braking, the electric motor 65 stops operating, the regulator valves 54 and 54 are demagnetized and opened, the suction valves 66 and 66 are demagnetized and closed, The in valves 56, 56; 58, 58 are demagnetized and opened, and the out valves 60, 60; 61, 61 are demagnetized and closed. Accordingly, the brake fluid pressure output from the output ports 41A and 41B of the slave cylinder 23 in operation passes from the regulator valves 54 and 54 to the in-valves 56 and 56; 20 and 21 can brake the four wheels.

  When the driver is not stepping on the brake pedal 11, if the pumps 64, 64 are driven by the electric motor 65 with the suction valves 66, 66 opened while being excited, they pass from the slave cylinder 23 through the suction valves 66, 66. The brake fluid sucked and pressurized by the pumps 64 and 64 is supplied to the regulator valves 54 and 54 and the in valves 56 and 56; 58 and 58. Accordingly, the regulator valves 54, 54 are excited to adjust the opening, thereby adjusting the brake fluid pressure in the fluid passages 52, 52, and the brake valve pressure is opened to a predetermined opening by excitation. 56; By selectively supplying the wheel cylinders 16, 17, 20, and 21 via 58 and 58, the braking force of the four wheels can be individually controlled even when the driver does not step on the brake pedal 11. Can do.

  Therefore, the braking force of the four wheels is individually controlled by the first and second brake actuators 51A and 51B, and the braking force of the inner turning wheel is increased to improve the turning performance, or the braking force of the outer turning wheel is increased to stabilize straight running. Performance can be improved.

  Further, when the driver steps on the brake pedal 11 suddenly to avoid a collision, the brake fluid pressure generated by the slave cylinder 23 is further increased by the pumps 64 and 64, and the wheel is driven by the increased brake fluid pressure. Maximum braking force is generated in the cylinders 16, 17, 20, and 21. That is, when the pumps 64 and 64 are driven by the electric motor 65 with the regulator valves 54 and 54 excited and closed, and the suction valves 66 and 66 excited and opened, the brake fluid generated by the slave cylinder 23 is generated. The pressure is sucked into the pumps 64 and 64 through the suction valves 66 and 66, and is supplied to the wheel cylinders 16, 17, 20 and 21 through the in-valves 56 and 56; Assisting the driver's braking operation can generate a large braking force for avoiding a collision.

  When the driver depresses the brake pedal 12 and detects, for example, that the left front wheel is in a locking tendency by stepping on the low friction coefficient road based on the output of the wheel speed sensor Sc. One brake valve 51A of the first brake actuator 51A is energized and closed, and one of the out valves 61 is excited and opened, so that the brake fluid pressure of the wheel cylinder 16 of the left front wheel is released to the reservoir 62 and predetermined. Then, the brake fluid pressure of the wheel cylinder 16 of the left front wheel is maintained by demagnetizing and closing the out valve 61. As a result, when the locking tendency of the wheel cylinder 16 on the left front wheel is resolved, the brake fluid pressure from the output port 41A of the slave cylinder 23 is opened to the wheel cylinder 16 on the left front wheel by demagnetizing the in-valve 58 and opening the valve. The braking force is increased by supplying and increasing the pressure to a predetermined pressure.

  When the left front wheel becomes locked again due to this pressure increase, by repeating the pressure reduction → holding → pressure increase, the ABS (anti-lock brake) that minimizes the braking distance while suppressing the lock on the left front wheel is repeated.・ System) Control can be performed.

  The ABS control when the left front wheel wheel cylinder 16 tends to lock has been described above. However, the right rear wheel wheel cylinder 17, the right front wheel wheel cylinder 20, and the left rear wheel wheel cylinder 21 tend to lock. The ABS control can be performed in the same manner.

  While the above-described VSA control (including ABS control) is being executed, the shutoff valves 22A and 22B are maintained in the closed state, so that the change in hydraulic pressure due to the operation of the VSA device 24 becomes a kickback and the master cylinder. Transmission from the brake pedal 12 to the brake pedal 12 can be prevented.

  When the power supply fails, as shown in FIG. 2, the shut-off valves 22A and 22B made of normally open solenoid valves are automatically opened, and the reaction force permission valve 25 made of normally closed solenoid valves is automatically turned on. The in-valves 56, 56; 58, 58 consisting of normally-open solenoid valves are automatically opened, and the out-valves 60, 60; 61, 61 consisting of normally-closed solenoid valves are automatically closed. To do. In this state, the brake hydraulic pressure generated in the two hydraulic chambers 13A and 13B of the master cylinder 11 is not absorbed by the stroke simulator 26, and the rear and front hydraulic pressures of the shutoff valves 22A and 22B and the slave cylinder 23 are detected. Passing through the chambers 39A, 39B and the in valves 56, 56; 58, 58, the wheel cylinders 16, 17, 20, 21 of the disc brake devices 14, 15, 18, 19 of each wheel are operated to generate braking force without any trouble. Can be made.

  Next, a method for setting the initial positions of the rear piston 38A and the front piston 38B will be described.

  When the rear piston 38A and the front piston 38B of the slave cylinder 23 are advanced by the actuator 31 operated by the electric motor 32, the hydraulic pressure is applied to the rear hydraulic chamber 39A at the moment when the rear piston 38A passes through the input port 40A and is closed. The hydraulic pressure is generated in the front hydraulic pressure chamber 39B at the moment when the front piston 38B passes through the input port 40B and closes. If the rear piston 38A and the front piston 38B are waiting immediately after the ports 40A and 40B, respectively, the electric motor 32 is driven, and at the same time, the loss stroke is minimized and the brake fluid pressure is generated with good responsiveness. Can do.

  In this case, since the position of the front piston 38B connected to the rear piston 38A via the return spring 37A is determined according to the position of the rear piston 38A, the rear piston 38A is accurately set to the initial position immediately after the input port 40A. Need to be positioned.

  Therefore, in the present embodiment, the following control is performed.

In the flowchart of FIG. 4, when it is first detected in step S1 that the driver's seat side door is opened by the door opening / closing switch Se and the driver gets on, the electric motor 32 of the slave cylinder 23 is moved to the rear piston 38A in step S2. Is driven in the reverse direction. As a result, when the end surface 42a of the male screw member 42 of the ball screw mechanism 35 contacts the inner wall surface 44a of the housing 44 (see FIG. 5), when the electric motor 32 stops rotating in step S3, the counter is incremented in step S4. To do.

  When the count value of the counter reaches a predetermined value in step S5, that is, when a predetermined time elapses after the electric motor 32 is forcibly stopped, the rotational position is detected by the rotational position sensor Sd of the electric motor 32 in step S6. Detect and store. In step S7, the electric motor 32 is driven forward until the rotational speed stored in advance is added to the stored rotational position to stop the rear piston 38A at a predetermined initial position.

  This initial position is a position where the front end of the rear piston 38A is located immediately after the input port 40A, and the input piston 40A is closed by the slight advance of the rear piston 38A from the initial position, and the rear hydraulic pressure chamber 39A is braked. Since the hydraulic pressure is generated, the response of the brake hydraulic pressure can be improved. Since the rotational speed of the electric motor 32 from the backward limit of the rear piston 38A to the initial position differs depending on the individual slave cylinder 23, it is measured for each product before factory shipment and stored in advance.

  When the rear piston 38A is accurately positioned at the initial position in this manner, the front piston 38B that moves forward and backward in conjunction with the rear piston 38A is also automatically positioned at the initial position with high accuracy.

  Further, since the rotational position of the electric motor 32 is detected by the rotational position sensor Sd after a predetermined time has elapsed since the electric motor 32 was forcibly stopped, the rotational position can be detected with high accuracy.

  Further, if the positioning of the rear piston 38A described above is performed while the vehicle is running, there is a problem that the slave cylinder 23 cannot generate brake fluid pressure during that time, but every time the driver gets into the vehicle, that is, the vehicle starts running. By positioning the rear piston 38A before starting, it is possible not only to prevent the braking operation while the vehicle is traveling, but also to position the rear piston 38A periodically, that is, every time the vehicle travels. Since this is done, the initial position of the rear piston 38A can always be properly maintained.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

For example, the slave cylinder 23 of the embodiment have been used to brake system of a vehicle, the present invention is Ru can be applied to an electric cylinder of any other application.

Hydraulic circuit diagram for a normal brake system for vehicles Hydraulic circuit diagram at the time of abnormality corresponding to FIG. Block diagram of control system Flowchart for explaining the operation of setting the initial position of the piston The figure which shows the limit position of the backward side of the ball screw mechanism

32 Electric motor 35 Ball screw mechanism (feed screw mechanism)
36 Cylinder body
37A rear return spring
37B front return spring 38A rear piston
38B rear piston 39A rear fluid pressure chamber
39B front hydraulic chamber 40A rear input port
40B front input port 41A rear output port
41B front output port
42 male screw member
43 female thread member
39B front hydraulic chamber

Claims (2)

A front piston (38B) and a rear piston (38A) aligned in the front-rear direction are slidably fitted in the cylinder body (36), and a front hydraulic pressure is placed on the front side of the front piston (38B). A front hydraulic chamber (39A) is defined between the chamber (39B) and the front and rear pistons (38B, 39A), respectively, and a front input port (40B) opened to the front hydraulic chamber (39B). ) And an output port (41B) and a rear input port (40A) and an output port (41A) that open to the rear hydraulic chamber (39A) are formed in the cylinder body (36), and the cylinder body (36) Between the front and rear pistons (38B), a front return spring (37B) that urges the front piston (38B) rearward, and between the front and rear pistons (38B, 39A). And a rear return spring (37A) for urging the rear piston (39A) rearward, and a male screw member (42) whose front end is in contact with the rear end of the rear piston (38A), and the male screw member (42). A feed screw mechanism (35) including a female screw member (43) to be screwed is provided between the electric motor (32) and the rear piston (38A), and the electric motor (32) is provided via the feed screw mechanism (35). Can drive the rear piston (38A) at the initial position forward, and the rear piston (38A) passes through the input port (40A) on the rear side in response to the forward drive to enter the rear hydraulic chamber (39A). a initial position setting method definitive a hydraulic generating electric cylinders to be output from the output port of the generated rear hydraulic side (41A),
The electric motor (32) moves the male screw member (42) to a predetermined limit position corresponding to the limit position in the backward direction of the rear piston (38A) , and the male screw member (42) reaches the predetermined limit position. Then a first step of Ru to stop operation of the electric motor (32),
A second step of storing the rotational position of the electric motor (32) after a predetermined time has elapsed since the operation of the electric motor (32) was stopped ;
After elapse of the predetermined time, the electric motor (32) is to be driven by the set rotational speed set in advance in the forward direction from the rotational position described above stored, said rear piston (38A) of the rear side of the input port ( A third step of positioning at the initial position immediately after 40A);
The initial position setting method in an electric cylinder characterized by including. The electric cylinder is used to brake system of a vehicle, the first to third steps is characterized in that Oite driver before the vehicle starts running is performed every time to detect that got into the vehicle The initial position setting method in the hydraulic cylinder for generating hydraulic pressure according to claim 1.

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