KR20030072832A - Pump of electronic control brake system - Google Patents

Abstract

PURPOSE: A pump of an electronic control type brake system is provided to reduce a sudden pressure change of a compression chamber and to properly maintain the maximum hydraulic pressure of the compression chamber in accordance with the intended pressure of the system. CONSTITUTION: A pump(40) of an electronic control type brake system has a piston installed in a bore(31a) formed in a modulator block(31); an outlet valve(45) installed to the open end of the bore and opened and shut by the reciprocating movement of the piston; and an inlet valve(42) opened and shut oppositely to the outlet valve to guide oil of a low-pressure accumulator to the compression chamber. The piston reciprocates by a spindle(35a) of a motor(35). A compression chamber(43) is formed between the front end of the piston and the outlet valve. The rear end of the piston is adjacent to the spindle, and the piston comprises a first piston(51) forming a suction passage within and having an inlet valve at the front end, and a second piston(52) disposed to the outer peripheral surface of the first piston. The second piston reciprocates together with the first piston.

Description

Pump of electronic control brake system

The present invention relates to an electronically controlled brake system, and more particularly, to a pump of an electronically controlled brake system for sucking low pressure oil on the low pressure accumulator or reciprocating hydraulic valve side and forcibly pumping it to the high pressure accumulator side.

In general, the electronically controlled brake system effectively prevents the slip of the vehicle and obtains a strong and stable braking force. The electronically controlled brake system uses an anti-lock brake system (ABS: Anti-Lock Brake) to prevent the wheel from slipping during braking. System), the brake traction control system (BTCS: Brake Traction Control System) which prevents slippage of the driving wheel during sudden start or acceleration of the vehicle, and anti-lock brake system and traction control in combination to control the brake hydraulic pressure A vehicle dynamic control system (VDC) has been developed to keep the vehicle stable.

The electronically controlled brake system includes a plurality of solenoid valves for controlling the braking hydraulic pressure delivered to the hydraulic brake side mounted on the wheel of the vehicle, a pair of low pressure accumulators and high pressure accumulators for temporarily storing oil discharged from the hydraulic brakes, It includes a motor and pump for forcibly pumping oil in the low pressure accumulator, and an ECU for controlling the solenoid valves and the operation of the motor. These components are compactly embedded in a modulator block made of aluminum.

Therefore, by the operation of the pump, the low pressure oil in the low pressure accumulator is pressurized and pumped to the high pressure accumulator, and the pressurized oil is transferred to the hydraulic brake or master cylinder assembly side. The pump is driven by a motor, which shows a conventional pump applied to an electronically controlled brake system.

Referring to FIG. 1, a conventional pump 10 is installed in a bore 5 formed in a modulator block 1 to reciprocate by an eccentric spindle 2a of a motor 2, and a suction flow path 6a therein. Is provided with a piston 6, an inlet valve 7 for opening and closing the outlet side of the suction passage 6a according to the position of the piston 6, and an inlet valve 7 with an open end of the bore 5. It is provided with an outlet valve (8) which operates in opposition.

The modulator block 1 has a suction port 3 for communicating the inlet side of the suction passage 6a formed in the piston 6 with the low pressure accumulator side, and the inlet side and the outlet of the high pressure accumulator (not shown). A discharge port 4 for communicating the outlet side of the valve 8 is formed.

An inlet valve 7 is provided at the tip of the piston 6, and a seal 9 is provided on the outer periphery of the piston 6 to prevent oil from leaking through a clearance with the inner wall of the bore 5. . The seal 9 has a ring shape and is disposed in the recess 6b recessed along the outer periphery of the piston 6.

The outlet valve 8 is seated on the valve cap 12 provided in the bore 5 of the modulator block 1 and the valve seat 11 embedded in the valve cap 12.

In the conventional pump 10 configured as described above, the piston 6 linearly reciprocates as the eccentric spindle 2a of the motor 2 rotates, and the inlet valve 7 is opposed to each other by the pressure change in the bore 5. And the outlet valve 8 open and close to pressurize the introduced oil to pump the high pressure accumulator.

That is, when the piston 6 moves to the top dead center, the pressure of the oil between the piston 6 and the outlet valve 8 increases, whereby the inlet valve 7 is closed and the outlet valve 8 is closed by the valve seat ( By opening away from 11, the oil is pumped through the discharge port 4 to the high pressure accumulator side.

On the other hand, when the piston 6 moves to the bottom dead center, a low pressure is formed in the space between the tip of the piston 6 and the outlet valve 8, which opens the inlet valve 7 and the outlet valve 8 ) Is seated on the valve seat 11 and closed so that the oil on the low pressure accumulator side passes between the piston 6 and the outlet valve 8 through the suction port 3, the suction flow path 6a and the inlet valve 7. Flows into space.

However, in the pump of the conventional electronically controlled brake system, a piston consisting of a single component is reciprocated at a high speed inside the bore by a high speed rotation of the motor to increase and discharge the pressure of oil introduced therein. Due to the suction and compression operation of the oil, the discharge pressure undergoes a drastic change, which leads to a severe pressure fluctuation, thereby increasing noise.

In addition, since the piston consisting of a single part simply repeats at the same speed between the top dead center and the bottom dead center, a maximum discharge pressure is formed that is relatively higher than the pressure inside the master cylinder in communication with the discharge port. Strong pressure pulsation is continuously transmitted to the brake pedal through the master cylinder, which causes the driver's dissatisfaction.

The present invention is to solve this problem, the object of the present invention is to configure the piston as the first piston and the second piston to reduce the sudden pressure fluctuations of the compression chamber, and at the same time the maximum hydraulic pressure of the compression chamber to the required pressure of the system It is to provide a pump of an electronically controlled brake system that can be properly maintained in accordance with.

1 is a cross-sectional view showing a pump configuration of a conventional electronically controlled brake system.

2 is a hydraulic system diagram of an anti-lock brake system to which the present invention is applied.

3 is a cross-sectional view showing the internal structure of the pump according to the first embodiment of the present invention.

4 is a cross-sectional view showing the internal structure of a pump according to a second embodiment of the present invention.

5 is a cross-sectional view showing the internal structure of a pump according to a third embodiment of the present invention.

6 is a cross-sectional view showing the internal structure of a pump according to a fourth embodiment of the present invention.

7 is a cross-sectional view showing the internal structure of a pump according to a fifth embodiment of the present invention.

Figure 8 is a graph comparing the pressure change in the compression chamber of the pump according to the prior art and the present invention.

* Description of symbols on the main parts of the drawings *

31 ... Modulator block 31a ... Bore

40 ... pump 43 ... compression chamber

50 ... piston 51 ... first piston

52.2nd piston 53 ... reverse spring

54 ... stopper

The present invention for achieving this object,

Outlet is installed in the bore formed in the modulator block and formed in the compression chamber between the piston reciprocating by the spindle of the motor and the open end of the bore and the opening of the piston by the reciprocating movement of the piston In the pump of the electronically controlled brake system having a valve and an inlet valve which opens and closes opposite to the outlet valve and guides the oil on the low pressure accumulator side to the compression chamber.

The piston may include a first piston having a rear end thereof in contact with the spindle, a suction flow path formed therein, and an inlet valve disposed at a distal end thereof; And a second piston disposed on an outer circumferential surface of the first piston in communication with the compression chamber and reciprocating together with the first piston.

A recess is provided on an outer circumferential surface of the first piston, and the recess is provided with a second spring and a reversing spring moving in association with the second piston so that the hydraulic pressure of the compression chamber reaches a constant pressure. The reverse spring is pushed toward the bottom dead center so that the second piston is reversed.

The rear end of the second piston is arranged to be spaced apart from the recess of the first piston in a steady state so as to form a reverse stroke of the second piston.

Seals in close contact with the outer circumferential surface of the first piston and the bore of the modulator block are disposed on the inner circumferential surface and the outer circumferential surface of the tip portion of the second piston to prevent leakage of oil.

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

2 shows a hydraulic system diagram of an anti-lock brake system to which a pump according to the present invention is applied.

Referring to FIG. 2, the anti-lock brake system to which the present invention is applied includes a plurality of solenoid valves 33A and 33B for controlling the transmission of braking hydraulic pressure to the hydraulic brake 23 side installed on the front wheel and the rear wheel, and the pressure reducing braking system. A low pressure accumulator 34 in which oil escaping from the hydraulic brake 23 side is temporarily stored in operation, a pair of pumps 40 for pumping oil stored in the low pressure accumulator 34 in a boost / hold braking operation; And one motor 35 for simultaneously driving the pair of pumps 40, and an orifice 36a is disposed at the outlet side to reduce pressure pulsation of oil pressurized and discharged by the driving of the pump 40. It is equipped with a high-pressure accumulator 36, these components are compactly embedded in a cuboid-shaped modulator block 31 made of aluminum.

The plurality of solenoid valves 33A and 33B are associated with the upstream side of the hydraulic brake 23 and are normally connected with the NO type solenoid valve 33A that is kept open and the downstream side of the hydraulic brake 23 and normally It is distinguished by the NC type solenoid valve 33B which is kept closed. The opening and closing operations of the solenoid valves 33A and 33B are respectively controlled by the ECU 32 which detects the vehicle speed through the wheel sensors 24 disposed on the front wheels and the rear wheels. In addition, the NC type solenoid valve 33B is opened in response to the depressurizing braking action, and the oil discharged from the hydraulic brake 23 side is temporarily stored in the low pressure accumulator 34.

In addition, the pair of pumps 40 are driven while having a certain phase difference by one motor 35 to pressurize the oil stored in the low pressure accumulator 34 to pump the high pressure accumulator 36. The structure of the pump according to the present invention will be described with reference to FIGS. 3 to 7.

First, the structure and operation of the pump according to the first embodiment of the present invention will be described with reference to FIG. Here, since the pair of pumps 40 are symmetrical with respect to the eccentric spindle 35a of the motor 35, only one pump structure is enlarged in FIG. 3 for convenience (the same also in FIGS. 4 to 7). Applies).

First, one motor 35 is provided at the central portion of one side of the modulator block 31 so that the spindle 35a protrudes to drive a pair of pumps 40 disposed on the left and right sides. The spindle 35a of the motor 35 is integrally formed with the eccentric shaft 35b and disposed between the pistons 50 of the pumps 40 so that a pair of pumps 40 are connected to one motor 35. As a result, they are driven while having a phase difference of 180 degrees from each other.

The pump 40 includes a bore 31a formed to be open to the modulator block 31 in the lateral direction, a piston 50 disposed reciprocally from side to side within the bore 31a, and a bore 31a. It is coupled to seal the open end to form a compression chamber (43) between the front end of the piston 50, the valve housing 44 with the outlet valve 45 is built to prevent the back flow of oil, and the outlet valve ( 45 is operated in opposition to the inlet valve 42 to allow oil suction into the compression chamber 43 when the bottom dead center of the piston 50 moves.

The piston 50 has a substantially rod-like shape, a first piston 51 having a suction passage 51a formed therein, and a second piston 52 disposed on an outer circumferential surface of the first piston 51. Is done.

The first piston 51 is arranged such that the rear end thereof is in contact with the eccentric shaft 35b of the motor 35, and a valve seat 42b for seating the ball 42c of the inlet valve 42 is coupled to the front end thereof. have. The suction passage 51a of the first piston 51 communicates with the suction port 31b processed in the modulator block 31. Therefore, the oil flowing into the suction flow path 51a of the first piston 51 through the suction port 31b of the modulator block 31 has the ball 42c of the inlet valve 42 spaced apart from the valve seat 42b. Or it is transmitted or blocked to the compression chamber 43 by the close operation.

The second piston 52 is disposed in the recess 51c formed on the outer circumferential surface of the first piston 51 in a state where the tip thereof contacts the valve seat 42b. A step 52b is formed inside the second piston 52, and a reversing spring 53 is disposed between the step 52b and the rear end of the first piston 51.

Further, the rear end of the second piston 52 is spaced apart from the first piston 51 at regular intervals, that is, in a state in which no pressure is formed in the compression chamber 43, and the recess 51c of the first piston 51 is spaced apart. To form a reverse stroke (S). Therefore, when the hydraulic pressure of the compression chamber 43 rises above the predetermined pressure, the reverse spring 53 is pushed toward the bottom dead center, and the second piston 52 moves backward to reduce the pressure increase rate of the compression chamber 43, Allow the maximum pressure of (43) to be lowered.

A communication hole 52a is formed at the rear end of the second piston 52 so that oil of the suction port 31b can flow into the suction flow path 51a of the first piston 51, and the second piston 52 O-ring seals 47 and 48 are disposed on the inner circumferential surface and the outer circumferential surface thereof, respectively, so that the bore of the second piston 52 and the first piston 51, and the second piston 52 and the modulator block 31 is disposed. Do not allow oil to leak through the contact surface with 31a).

The piston 50 configured as described above presses and discharges oil while opening and closing the inlet valve 42 and the outlet valve 45 alternately by linearly reciprocating in the bore 31a of the modulator block 31. .

The inlet valve 42 is disposed at the inlet of the compression chamber 43 in communication with the suction port 31b, so that when the piston 50 moves to the top dead center, the compression chamber 43 communicates with the suction port 31b. Is a kind of check valve that allows the compression chamber 43 to communicate with the suction port 31b when the piston 50 moves to the bottom dead center.

That is, the suction port 31b has a modulator block in a direction orthogonal to the machining direction of the bore 31a so that one end thereof is connected to the low pressure accumulator 34 (see FIG. 2) and the other end thereof directly communicates with the compression chamber 43. It is processed to 31. The inlet valve 42 includes the above-described valve seat 42b coupled to the first piston 51, a valve housing 42a press-fitted to the valve seat 42b, and an orifice is formed at the inlet side, and the valve housing ( A ball 42c embedded in 42a and seated or spaced in the valve seat 42b to allow the compression chamber 43 to be blocked or communicated with the suction port 31b, and the ball 42c is provided with a valve seat 42b. And a compression spring 42d disposed between the valve housing 42a and the ball 42c to elastically support toward.

A return spring 46 is disposed between the rear end of the valve housing 42a of the inlet valve 42 and the front end of the compression chamber 43 so that the piston 50 reciprocates between the top dead center and the bottom dead center. ) Is applied to the bottom dead center.

When the piston 50 is moved to the bottom dead center by the inlet valve 42, the compression chamber 43 is brought into a low pressure state, and the ball 42c of the inlet valve 42 is compressed by the compression spring 42d and the valve seat ( The compression chamber 43 is in communication with the suction port 31b spaced apart from 42b). On the contrary, when the piston 50 moves to the top dead center, the compression chamber 43 becomes a high pressure state, and the ball 42c of the inlet valve 42 comes into close contact with the valve seat 42b to suck the compression chamber 43. It is blocked from the port 31b.

The outlet valve 45 operates in opposition to the inlet valve 42 according to the reciprocating motion of the piston 50, and functions to connect or block the discharge passage 44a to be described later with the compression chamber 43. An orifice 45b is formed and is disposed at the open end of the bore 31a, a ball 45c for opening and closing the orifice 45b of the valve seat 45a, and the ball 45c. A compression spring 45d for applying an elastic force to the valve seat 45a side is provided.

The compression spring 45d and the ball 45c of the outlet valve 45 are embedded in a valve housing 44 which seals the open end of the bore 31a, which is provided at the outlet of the outlet valve 45. A discharge flow path 44a for communicating the side with the discharge port 31c is formed. Here, the discharge port 31c is an oil passage processed in the modulator block 31 such that the outlet side of the pump 40 and the inlet side (see FIG. 2) of the high pressure accumulator 36 communicate with each other.

Further, a seal 48 is disposed at the rear end of the first piston 51 to prevent oil from leaking to the eccentric shaft 35b of the motor 35 through the outer circumferential surface of the first piston 51. .

Next, the operation and effect of the anti-lock brake system to which the pump 40 according to the first embodiment of the present invention configured as described above is applied will be described.

Since the anti-lock brake system controls the braking state of the vehicle according to the braking pressure decompression mode, the boosting mode, and the holding mode to prevent slippage of the vehicle, each solenoid valve ( 33A) 33B is operated to open or close repeatedly with the operation of the pump 40. That is, when the braking pressure in the hydraulic brake 23 is greater than the frictional force of the road in a state where the driver presses the brake pedal 20 and the braking force is exerted by the braking hydraulic pressure formed through the power booster 21 and the master cylinder assembly 22. In this case, the ECU 32 closes the NO solenoid valve 33A and opens the NC solenoid valve 33B (see FIG. 2).

If the decompression state of the braking pressure is long or the vehicle moves to a place where the friction coefficient of the road surface is high, the friction force that may be generated on the tire and the road surface of the vehicle should be increased to increase the braking pressure. The ECU 32 determines the situation based on the signals input from the wheel sensors 24 and drives the pump 40 through the motor 35 to increase the braking pressure in the hydraulic brake 23. Accordingly, the oil stored in the low pressure accumulator 34 is pressurized and supplied to the high pressure accumulator 36, and the oil is continuously transferred to the hydraulic brake 23 through the open NO solenoid valve 33A. As a result, the braking hydraulic pressure is increased.

In this boost mode, the oil stored in the low pressure accumulator 34 is pressurized by the driving of the pump 40 and is supplied to the NO type solenoid valve 33A while passing through the high pressure accumulator 36 and the orifice 36a. The operation of the pump 40 according to the first embodiment of the present invention will be described in more detail.

As the eccentric spindle 35a of the motor 35 rotates, when the piston 50 slides to the top dead center in the bore 31a (arrow A direction), the return spring 46 is compressed by the piston 50. While the inlet valve 42 is seated on the valve seat 42b and closed, the outlet valve 45 is opened by the pressure of the compression chamber 43, so that the pressurized oil is discharged to the discharge passage 44a and the discharge port 31c. Through the discharge to the high pressure accumulator 36 side.

At this time, the second piston 52 moves along with the first piston 51 toward the compression chamber 43 to reduce the variable volume of the compression chamber 43, thereby reducing the amount of oil in the compression chamber 43. The pressure will increase.

As the pressure of the oil in the compression chamber 43 reaches a predetermined pressure while the piston 50 moves to the top dead center, the reverse spring 53 disposed on the outer circumferential surface of the first piston 51 together with the second piston 52. When the elastic force is exceeded, the second piston 52 moves in the opposite direction to the first piston 51 to reduce the reduction rate of the variable volume of the compression chamber 43 so that the maximum oil pressure of the compression chamber 43 is increased. As compared with the conventional pump 10 (refer FIG. 1), it is made to become slightly low and the rate of increase of the oil pressure in the compression chamber 43 is reduced.

That is, in the process of increasing the pressure of the compression chamber 43 during the initial movement of the piston 50 to the top dead center, the area of the bore 31a of the modulator block 31 corresponds to the diameter of the bore 31a. The two pistons 52 move forward at the same time to quickly increase the pressure in the compression chamber 43. When the pressure in the compression chamber 43 reaches a magnitude exceeding the elastic force of the reverse spring 53, the second piston ( 52 moves relatively to the rear end of the first piston 51 while moving in the direction of increasing the volume of the compression chamber 43 as opposed to the first piston 51.

By the operation of the second piston 52, the inclination of the pressure rise of the compression chamber 43 (the inclination 2 in FIG. 8) becomes smaller than the initial pressure increase inclination (the inclination 1 in FIG. 8). It is also possible to reduce the size of the maximum oil pressure of the compression chamber 43, so that the driver does not feel uncomfortable pressure pulsation when the pedal is pressed, giving a good braking feeling, and also reduces the noise caused by the pressure pulsation You can do it.

Here, the reverse operation of the second piston 52 is made only as much as the structure corresponding to the reverse stroke (S) so that the pressure generated in the compression chamber 43 does not fall below the appropriate pressure.

On the other hand, when the piston 50 reaches the top dead center, the first piston 51 is slid to the bottom dead center by the reaction force of the return spring 46 (arrow B direction) while the second piston 52 is again It retracts with the first piston 51 and returns to the state shown in FIG. 3, so that the second piston 52 is spaced apart from the first piston 51 by the reverse stroke S. FIG. In addition, by the backward operation of the piston 50, the compression chamber 43 is brought into a low pressure state, the inlet valve 42 is opened and the outlet valve 45 is closed, so that the oil on the low pressure accumulator 34 side is suction port. It is sucked into the compression chamber 43 through 31b.

4 shows the structure of a pump 40A according to a second embodiment of the present invention. As shown therein, the pump 40A according to the second embodiment has a stopper 54 installed between the step 52b of the second piston 52 and the tip of the reverse spring 53 so that the seal 47 In addition to being able to be installed on the inner circumferential surface of the second piston 52, the reverse spring 53 is more reliably supported and operated between the outer circumferential surface of the first piston 51 and the inner circumferential surface of the second piston 52. will be. Except for the stopper 54 and the seal 47 described above, the pump 40A according to the second embodiment has the same structure as the pump 40 according to the first embodiment described above, Further description of the pump 40A is omitted.

5 shows a structure of a pump 40B according to a third embodiment of the present invention. The pump 40B according to this third embodiment also has a structure very similar to that of the pump 40 of the first embodiment described above, and therefore the same parts will be described with the same reference numerals.

As shown in FIG. 5, the pump 40B according to the third embodiment is installed at the tip of the first piston 51 in the pump 40 of the first embodiment so that the ball 42c of the inlet valve 42 is provided. Instead of removing the valve seat 42b to be seated, the seat part 51b is integrally formed at the tip of the first piston 51 to function as the valve seat 42b.

As the seat portion 51b formed on the first piston 51 functions as the valve seat 42b in the first embodiment, the tip portion of the second piston 52 is in communication with the compression chamber 43. It comes in direct contact with the tip of the recess 51c of the first piston 51.

3, in the pump 40 according to the first embodiment, the valve seat 42b is inserted into the front end of the first piston 51 so that a flow path having a smaller size than the suction flow path 51a is provided. The flow rate of the oil is increased by the formed valve seat 42b, which delays the discharge of the oil and reduces the discharge amount. In particular, at low temperatures, the viscosity of the oil is increased, such a phenomenon becomes more prominent.

Therefore, the pump 40B of the third embodiment has proposed a structure for solving the disadvantages of the pump 40 of the first embodiment. That is, the pump 40B according to the third embodiment integrally forms the seat portion 51b at the tip of the first piston 51 so that the oil can flow into the compression chamber 43 through the suction flow passage 51a only. As a result, the flow resistance of the oil is reduced, and thus the discharge of the oil can be made quickly without delay, as well as the number of parts can be reduced, thereby reducing manufacturing costs and assembly time.

Except for the structure described above, the pump 40B of the third embodiment functions and functions the same as the pump 40 of the first embodiment, and thus, further description thereof will be omitted.

6 shows a pump 40C according to a fourth embodiment of the invention. In the pump 40C of the fourth embodiment, like the pump 40A of the second embodiment, a stopper 54 is provided between the step 52b of the second piston 52 and the tip of the reverse spring 53 to seal the seal. While allowing 47 to be installed on the inner circumferential surface of the second piston 52, the reverse spring 53 is more reliably supported between the outer circumferential surface of the first piston 51 and the inner circumferential surface of the second piston 52. To make it work. Except for the stopper 54 and the seal 47, the pump 40C according to the fourth embodiment has the same structure as the pump 40B according to the third embodiment described above, Further description of the pump 40C is omitted.

7 shows a pump 40D according to a fifth embodiment of the present invention. The pump 40D of this fifth embodiment uses a single seal 48a between the tip of the second piston 52 provided in the recess 51c of the first piston 51 and the tip of the first piston 51. Although the seal 48a is configured to have an X-shaped cross section, the seal structure is simplified compared with the above-described embodiments, and the structure and operation of the seal 48a are different from those of the fourth embodiment shown in FIG. Since it is the same as the pump 40C, further description is abbreviate | omitted.

Figure 8 is a graph comparing the pressure change in the compression chamber of the prior art and the pump according to the present invention, the curve shown by the dashed-dotted line shows the pressure change in the compression chamber by the pump of the prior art, a solid line The curve shown represents the pressure change in the compression chamber by the pump of the present invention.

As shown in the drawing, the pressure change in the compression chamber by the conventional pump rapidly increases the pressure until reaching the top dead center P1, and also corresponds to the pressure at the top dead center P1. The maximum pressure of R is relatively large compared to the present invention. Accordingly, the discharge pressure of the conventional pump increases noise due to a sudden increase in pressure, and a strong pressure pulsation is transmitted to the brake pedal through the master cylinder by a high maximum discharge pressure, thereby causing a dissatisfaction of the driver.

However, the pressure change in the compression chamber by the pump of the present invention is a rapid pressure rise is made in the section (indicated by the slope 1) in which the first piston and the second piston move toward the top dead center integrally, In the section in which the second piston moves in the opposite direction to the first piston (indicated by the slope 2), the pressure rise rate is lowered, so that the maximum pressure of the compression chamber corresponding to the pressure at the top dead center P2 is relatively lower than in the prior art. You lose. Accordingly, the pump according to the present invention is to reduce the noise due to the rapid pressure rise, the pressure pulsation is not large by the discharge pressure of the properly adjusted oil can provide a good braking feeling to the driver.

Claims (10)

Outlet is installed in the bore formed in the modulator block and formed in the compression chamber between the piston reciprocating by the spindle of the motor and the open end of the bore and the opening of the piston by the reciprocating movement of the piston In the pump of the electronically controlled brake system having a valve and an inlet valve which opens and closes opposite to the outlet valve and guides the oil on the low pressure accumulator side to the compression chamber. The piston may include a first piston having a rear end thereof in contact with the spindle, a suction flow path formed therein, and an inlet valve disposed at a distal end thereof; And a second piston disposed on an outer circumferential surface of the first piston in communication with the compression chamber and configured to reciprocate with the first piston. The method of claim 1, A recess is provided on an outer circumferential surface of the first piston, and the recess is provided with a second spring and a reversing spring moving in association with the second piston so that the hydraulic pressure of the compression chamber reaches a constant pressure. The pump of the electronically controlled brake system, characterized in that the second spring is reversed while the reverse spring is pushed toward the bottom dead center. The method of claim 2, The second piston is a pump of the electronically controlled brake system, characterized in that the stepped end is formed on the inner peripheral surface so that one end of the reverse spring is supported. The method of claim 3, wherein And a stopper disposed between the stepped portion and the reverse spring. The method of claim 2, And the rear end of the second piston is arranged to be spaced apart from the recess of the first piston in a steady state so as to form a reverse stroke of the second piston. The method of claim 2, The inner circumferential surface and the outer circumferential surface of the distal end of the second piston is disposed in close contact with the outer circumferential surface of the first piston and the bore of the modulator block to prevent leakage of oil. The method of claim 6, The cross section of the seal is the pump of the electronically controlled brake system, characterized in that forming an O shape. The method of claim 6, The cross section of the seal is the pump of the electronically controlled brake system, characterized in that forming an X shape. The method of claim 1, The pump of the electronically controlled brake system, characterized in that the valve seat for mounting the inlet valve is installed at the front end of the first piston. The method of claim 9, The valve seat is a pump of the electronically controlled brake system, characterized in that the through-hole is formed in communication with the suction flow path of the first piston.