JP2008247390A - Master cylinder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cup inner diameter slide type master cylinder having simple structure with high reliability and ensuring a sufficient suction property of a brake liquid relative to a pressure chamber during the returning of a piston and at the control of an automobile brake such as vehicle stability control. <P>SOLUTION: Annular walls 17, 18 integrally constituted of a cylinder body 1 are provided behind primary cups 13, 15. Inner diameters of the annular walls 17, 18 are made larger than an inner diameter of the cylinder, and annular passages 19, 20 are formed between the annular walls, a primary piston 2 and a secondary piston 5. Further, communication passages 23, 30 with reservoirs 10 having gaps with the pistons 2, 5 larger than the annular passages 19, 20 are formed at the rear side of the annular walls 17, 18. Piston ports 8, 9 are made to communicate with the reservoir 10 through the annular passages 19, 20 at non-operation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a master cylinder employed in a hydraulic brake device for a vehicle, and in particular, a master cylinder of a type in which a piston slides on the inner periphery of a cup held by a cylinder body to pressurize brake fluid in a pressure chamber (hereinafter referred to as this). Is referred to as a cup inner diameter sliding type master cylinder).

  In recent years, an increasing number of hydraulic brake devices for vehicles perform automatic brake control such as vehicle stability control at the judgment of an electronic control device when the driver is not performing a brake operation.

As a prior art of a cup inner diameter sliding master cylinder employed in this type of hydraulic brake device, for example, there is one disclosed in Patent Document 1 below.
JP 2000-71969 A

  In the master cylinder described in Patent Document 1, a spacer is arranged between a primary cup arranged on the outer periphery of a piston and a guide provided at the rear of the primary cup, and pressure is applied from a reservoir through a groove provided on the back side of the spacer. The brake fluid is supplied to the chamber.

  The cup inner diameter sliding master cylinder for automatic brake control not only has good suction performance of brake fluid from the reservoir to the pressure chamber when the advanced piston returns, but also from the reservoir when automatic brake control is executed. It is also required to ensure a good absorbability of brake fluid into the pressure chamber.

  The master cylinder of Patent Document 1 is provided with a thin spacer as described above in order to meet the demand and improve the operation feeling at the same time, and when the brake operation is not performed by the driver, that is, when the piston is in the initial position. In some cases, it is possible to bring the piston port that connects the pressure chamber to the reservoir closer to the primary cup.

  The brake fluid from the reservoir deforms the cup when returning to the piston and is sucked into the pressure chamber through the periphery of the cup. When automatic brake control is executed, the brake fluid passes through the piston port (port provided on the piston) into the pressure chamber. Inhaled.

  In the master cylinder of Patent Document 1 described above, the spacer receives pressure from the primary cup that has received the hydraulic pressure, and a large stress is generated in the spacer. For this reason, there is a concern that the spacer may cause fatigue failure.

  Also, if the brake fluid suction from the reservoir to the pressure chamber during automatic brake control is to be improved, the back surface of the spacer needs to be closer to the piston port. For this purpose, the spacer must be made thinner. However, since the spacer is supported by a plurality of protrusions in the relationship of providing a groove on the back side, it is difficult to meet the demand due to the problem of strength.

  Further, since there is a radial gap between the spacer and the cylinder body and between the spacer and the piston, the spacer is eccentric with respect to the cylinder body, and the flow of brake fluid from the gap is not uniform. there were. For this reason, the flow of brake fluid to the front of the primary cup at the time of piston return may be obstructed, and the brake fluid supply from the inner diameter of the spacer to the pressure chamber through the piston port at the time of non-operation is not sufficient. was there.

  Further, due to the eccentricity of the spacer, there is a portion where the gap between the spacer and the cylinder body and the gap between the spacer and the piston are partially increased, and the partially increased gap is subjected to hydraulic pressure. The primary cup could bite and be damaged.

  Further, since the spacer and the guide are assembled, it is necessary to provide a cover separately from the cylinder body and screw the cover after the spacer and the guide are assembled, resulting in problems of complicated structure and increased assembly man-hours.

  The present invention eliminates the above-mentioned problems found in the cup inner diameter sliding master cylinder, that is, a simple and reliable structure, and good brake fluid against the pressure chamber at the time of piston return and automatic brake control. The issue is to ensure the inhalability.

In order to solve the above problem, in the present invention, in the master cylinder of the type in which the piston slides on the inner periphery of the cup held by the cylinder body and pressurizes the brake fluid in the pressure chamber.
As the piston, a uniform piston is provided in each part in the longitudinal direction of the outer diameter, and
An annular wall having an inner diameter larger than the inner diameter of the cylinder body is provided integrally with the cylinder body behind the primary cup,
Forming an annular passage between the annular wall and the piston;
A communication path with the reservoir having a gap between the piston and the piston larger than the annular path is provided at the rear of the annular wall.

In addition, this master cylinder will become more preferable if the structure enumerated below is added.
1) The annular wall is thickened from the inner peripheral side toward the radially outer side.
2) A small radius R chamfer is provided at each of the front corner, the rear corner, and the front and rear corners on the inner peripheral side of the annular wall.
3) The piston is slidably guided by the inner diameter of the cylinder body at the front of the primary cup and the rear of the annular wall.
4) A piston port for communicating the pressure chamber with the communication path when the piston is in the initial position is disposed in the vicinity of the annular wall.
5) A plurality of axial grooves having a passage area equal to or larger than that of the annular passage for communicating the cup housing groove with the pressure chamber on the inner circumferential surface of the cylinder for slidingly guiding the piston in front of the primary cup. Provide.
6) The plurality of axial grooves are grooves having an arcuate cross section.

  The piston here refers to both a primary piston and a secondary piston for a tandem master cylinder.

  In the present invention, since the annular wall that receives pressure from the primary cup is formed integrally with the cylinder body, the strength of the annular wall can be sufficiently secured, and the reliability in terms of strength is increased.

  In addition, since an annular passage is formed between the annular wall and the piston, both the fluidity of the brake fluid sucked into the pressure chamber through the periphery of the cup and the brake fluid sucked into the pressure chamber through the piston port are improved. Therefore, it is possible to secure a good suction performance of the brake fluid into the pressure chamber at the time of piston return and automatic brake control.

  Furthermore, since the required functions are secured with a simple structure with a small number of parts, processing and assembly are easy and productivity is extremely high.

  In addition, what made the said annular wall thick from the inner peripheral side toward radial direction outward ensures the favorable communication property with a piston port by the expansion effect of an annular channel, and raises the intensity | strength of an annular wall further. be able to.

  In addition, when the front corner on the inner peripheral side of the annular wall is provided with a chamfered portion with a small radius, there is no fear that the edge of the corner bites into the cup, and the primary cup is hardly damaged. Moreover, what provided the chamfering part of the small radius in the rear part corner of the inner peripheral side of this cyclic | annular wall further strengthens the expansion effect of the above-mentioned cyclic | annular passage.

  When the piston is slidably guided by the inner diameter of the cylinder body at the front of the primary cup and the rear of the annular wall, the coaxiality between the annular wall and the piston is maintained with high accuracy, and smooth flow of brake fluid is ensured. And prevents damage to the primary cup.

  Further, in the case where a plurality of axial grooves communicating with the pressure chamber are provided in the inner periphery of the cylinder body in front of the primary cup, a brake fluid flow path corresponding to an annular passage between the annular wall and the piston is formed by the grooves. Then, the brake fluid that reaches the pressure chamber by bending the cup flows smoothly, and the return operation of the piston is performed smoothly.

  In addition, in the case where the plurality of axial grooves are formed into circular grooves, the grooves can be easily processed with a rotary tool or the like.

  Hereinafter, an embodiment of a master cylinder of the present invention will be described with reference to FIGS. In the figure, 1 is a cylinder body, 2 is a primary piston that is slidably guided by the cylinder body 1, 3 is a first pressure chamber that pressurizes internal brake fluid with the primary piston 2 and generates brake fluid pressure, and 4 is a primary piston. 2 is a return piston, 5 is a secondary piston disposed in front of the primary piston 2 (also slidingly guided by the cylinder body 1), and 6 is a brake fluid pressure generated by pressurizing internal brake fluid with the secondary piston 5. The second pressure chamber, 7 is the return spring of the secondary piston 5, 8 is the piston port provided in the primary piston 2, 9 is the piston port provided in the secondary piston 5, 10 is the reservoir, 11 is the output of the first pressure chamber 3. A port 12 is an output port of the second pressure chamber 6. A plurality of piston ports 8 and 9 are provided at appropriate intervals in the circumferential direction.

  Inside the cylinder body 1, a primary cup 13 that seals the outer periphery of the primary piston 2, a secondary cup 14 that shuts off the cylinder and the atmosphere at the outer periphery of the primary piston 2, a primary cup 15 that seals the outer periphery of the secondary piston 5, and A pressure cup 16 that blocks between the first pressure chamber 3 and the reservoir 10 is disposed on the outer periphery of the secondary piston 5.

  Each of the primary cups 13 and 15, the secondary cup 14, and the pressure cup 16 is provided with an annular cup storage groove on the inner periphery of the cylinder body 1 and incorporated in the cup storage groove. In addition, annular walls 17 and 18 that individually receive and support the primary cups 13 and 15 are provided integrally with the cylinder body 1 behind the primary cups 13 and 15 (right side in the drawing).

  The inner diameters of the annular walls 17 and 18 are made larger than the inner diameter of the cylinder, and as shown in FIG. 3, the annular passages 19, 19 are respectively disposed between the annular wall 17 and the primary piston 2 and between the annular wall 18 and the secondary piston 5. 20 is further formed on the inner peripheral side of the annular walls 17 and 18 with a small radius R chamfering that eliminates the edges of the front and rear corners on the inner peripheral side. A chamfered portion formed in the corner is denoted by reference numeral 21 in FIG.

  An annular communication passage 30 having a larger gap with the primary piston 2 than the annular passage 19 is provided at the rear portion of the annular wall 17, and a gap between the secondary piston 5 is provided at the rear portion of the annular wall 18 with the annular passage 20. Larger annular communication passages 23, and the annular passages 19, 20 are connected to the reservoir 10 via these communication passages 30, 23 and communication passages 22, 24, 25 provided separately in the cylinder body 1. Communicates.

  Further, the piston port 8 is disposed in the vicinity immediately below the annular wall 17 and the piston port 9 is disposed in the vicinity immediately below the annular wall 18 (both when the master cylinder is in an inoperative state).

  The annular walls 17 and 18 have a structure in which the rear surfaces 17a and 18a shown in FIG. 3 are inclined and become thicker from the inner peripheral side toward the radially outer side. The passage area on the side close to the reservoir 10 is enlarged to form a flow path through which the brake fluid easily flows between the primary piston 2 and the secondary piston 5, and the strength of the annular walls 17 and 18 is increased. The annular walls 17, 18 are designed to withstand high pressures. The primary piston 2 is slidingly guided by the sliding guide portions 40 and 41, and the secondary piston 5 is slidingly guided by the sliding guide portions 42 and 43. In the present embodiment, the cylinder body 1 behind the pressure cup 16 is not a sliding guide, but may be a sliding guide similar to the front of the primary cups 13 and 15.

  A shaft that communicates the groove containing the primary cup 13 with the first pressure chamber 3 and the groove containing the primary cup 15 with the second pressure chamber 6 on the cylinder inner peripheral surface in front of the primary cups 13 and 15. A plurality of arc-shaped grooves 26 and 27 in the direction are provided. FIG. 2 shows a cross-sectional shape of the groove 26. The groove 27 has the same shape as the groove 26.

  The grooves 26 and 27 both have a passage area (total area) substantially equal to or greater than the passage area of the annular passages 19 and 20, and brake fluid that has passed through the annular passages 19 and 20 is first and second. 2 The fluid can smoothly flow into the pressure chambers 3 and 6.

  The size of the annular passages 19 and 20 (clearance dimension between the piston and the annular wall) is preferably about 0.2 mm to 0.4 mm from the viewpoint of durability and operation characteristics of the master cylinder.

  The example master cylinder configured as described above has the first pressure chamber 3 and the second master cylinder in the rapid return stroke in which the primary piston 2 and the secondary piston 5 are rapidly returned from the positions where the primary piston 2 and the secondary piston 5 are moved forward with the release of braking by the driver. Since the pressure chamber 6 becomes negative pressure, the inner peripheral side of the primary cups 13 and 15 is deformed by the difference in pressure received between the front and back surfaces, and the brake fluid from the reservoir 10 flows from the annular passages 19 and 20 to the primary cups 13 and 15. It passes through the inner side, passes through the grooves 26 and 27, and is sucked into the first pressure chamber 3 and the second pressure chamber 6 smoothly. For this reason, the primary piston 2 and the secondary piston 5 return smoothly, and the responsiveness to release of the brake or sudden loosening is improved.

  On the other hand, when the brake fluid is requested from the hydraulic system connected to the output ports 11 and 12 when automatic brake control such as vehicle stability control is executed when the master cylinder is not operated, braking through the communication passages 30 and 23 is performed. The liquid flows into the annular passages 19 and 20 whose inlet side is enlarged by inclining the back surfaces 17a and 18a of the annular walls 17 and 18, and the piston ports 8 and 9 opened in the annular passages 19 and 20 are passed through. Thus, the fluid is smoothly supplied to the hydraulic system via the first pressure chamber 3 and the second pressure chamber 6. Accordingly, the responsiveness of the automatic brake control is also improved.

  In addition, since the annular walls 17 and 18 are made thicker radially outward from the inner peripheral side, each annular wall 17 and 18 is simultaneously secured with good communication with the piston ports 8 and 9. It is also possible to ensure sufficient strength.

  In addition, since the front corner and the rear corner on the inner peripheral side of the annular wall are rounded with a small radius, the effect of preventing damage to the primary cup and the effect of expanding the annular passage can be obtained.

  Further, since the grooves 26 and 27 are formed into arc-shaped cross sections, the grooves 26 and 27 can be easily processed with a rotary tool or the like.

  In addition, the required functions are ensured with a simple structure with a small number of parts, making it easy to process and assemble, and excellent productivity.

Sectional drawing which shows an example of the master cylinder of this invention Sectional view taken along line II-II in FIG. The figure which expands and shows the principal part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder body 2 Primary piston 3 1st pressure chamber 4, 7 Return spring 5 Secondary piston 6 2nd pressure chamber 8, 9 Piston port 10 Reservoir 11, 12 Output port 13, 15 Primary cup 14 Secondary cup 16 Pressure cups 17, 18 Annular walls 19, 20 Annular passage 21 Chamfered portions 22-25, 30 Communication passages 26, 27 Grooves 40-43 Piston sliding guide portion

Claims (7)

In the master cylinder of the type in which the piston slides on the inner circumference of the cup held by the cylinder body and pressurizes the brake fluid in the pressure chamber,
As the piston, a uniform piston is provided in each part in the longitudinal direction of the outer diameter, and
An annular wall having an inner diameter larger than the inner diameter of the cylinder body is provided integrally with the cylinder body behind the primary cup,
Forming an annular passage between the annular wall and the piston;
A master cylinder according to claim 1, wherein a communication passage with a reservoir having a gap between the piston and the piston larger than the annular passage is provided at a rear portion of the annular wall.   The master cylinder according to claim 1, wherein the annular wall is thickened from the inner peripheral side toward the radially outer side.   3. The master cylinder according to claim 1, wherein an R-chamfered portion having a small radius is provided at each of the front corner, the rear corner, and the front and rear corners on the inner peripheral side of the annular wall.   The master cylinder according to any one of claims 1 to 3, wherein a piston is slidably guided by an inner diameter of a cylinder body at a front side of the primary cup and a rear side of the annular wall.   5. The master cylinder according to claim 1, wherein a piston port for communicating the pressure chamber with the communication passage when not in operation is disposed in the vicinity of the annular wall.   The piston is slidably guided by the cylinder body, and the primary cup is stored in a cup storage groove provided on the inner peripheral surface of the cylinder, and the cup storage groove is inserted into the cylinder inner peripheral surface in front of the primary cup. 6. A master cylinder according to claim 1, wherein a plurality of axial grooves having a passage area equal to or larger than the annular passage communicating with the pressure chamber are provided.   The master cylinder according to claim 6, wherein the plurality of axial grooves are grooves having a circular arc cross section.

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