Master cylinder

• US 20020124563A1
• Filed: 02/26/2002
• Published: 09/12/2002
• Est. Priority Date: 02/26/2001
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Hitachi Seisakusho (Hitachi, Ltd.)
• Original Assignee: Tokico Limited (Hitachi, Ltd.)
• Inventors: Sano, Kenji, Koshimizu, Naganori, Ando, Hiromi, Ogiwara, Takato
• Granted Patent: US 6,698,202 B2
• Time in Patent Office: Days
• US Class Current: 60/588
• CPC Class Codes: B60T 11/224 with pressure-varying means, e.g. with two stage operation provided by use of different piston diameters including continuous variation from one diameter to another
• CPC Class Codes: B60T 11/26 Reservoirs integral with master controls B60T11/22

Abstract

A master cylinder of the invention supplies a brake fluid from a large diameter pressurizing chamber 56 to a small diameter hydraulic chamber 49 by opening a reverse flow checking opening and closing portion 61 by sliding movement of a stepped piston 16 forwardly, that is, fast fill and when the hydraulic pressure of the large diameter pressurizing chamber 56 rises, a control valve 86 escapes the hydraulic pressure of the large diameter pressurizing chamber 56 to a reservoir 12 to gradually lower in accordance with rise of the hydraulic pressure of the small diameter hydraulic chamber 49, thereby capable of reducing a strange feeling in a pedal feeling caused by sudden pressure release of the large diameter pressuring chamber 56.

Claims

1. A master cylinder comprising

a stepped cylinder having a large diameter cylinder portion and a small diameter cylinder portion;

a stepped piston having a large diameter piston portion slidably inserted into the large diameter cylinder portion of the stepped cylinder and a small diameter piston portion slidably inserted into the small diameter cylinder portion; and

a reverse flow checking opening and closing portion for partitioning the inside of the stepped cylinder into a large diameter pressurizing chamber on the large diameter piston portion side and a small diameter hydraulic chamber on the small diameter piston portion side and permitting a brake fluid to flow only from the large diameter pressurizing chamber side to the small diameter hydraulic chamber side, the reverse flow checking opening and closing portion being opened by reducing a volume of the large diameter pressurizing chamber by sliding movement of the stepped piston toward the small diameter hydraulic chamber side to thereby supply the brake fluid from the large diameter pressurizing chamber side to the small diameter hydraulic chamber side; and

a control valve for gradually reducing a hydraulic pressure of the large diameter pressurizing chamber in accordance with the rise of the hydraulic pressure of the small diameter hydraulic chamber.

2. The master cylinder according to claim 1, wherein the control valve includes a valve piston and a valve spring for urging the valve piston within a valve cylinder;

and the valve piston reduces the hydraulic pressure of the large diameter pressurizing chamber when a total force of a propulsive force produced by the hydraulic pressure of the small diameter hydraulic chamber and a propulsive force produced by the hydraulic pressure of the large diameter pressurizing chamber exceeds an urging force by the valve spring.

3. The master cylinder according to claim 2, wherein the master cylinder includes a reservoir for storing the brake fluid;

the control valve is provided with at least two ring seals between the valve cylinder and the valve piston to partition the inside of the valve cylinder, and a chamber formed between the ring seals and the small diameter hydraulic chamber communicate with each other; and

the valve spring is provided at one side of the valve piston, and a relief chamber for communicating to the reservoir and the large diameter pressurizing chamber is provided at the other side of the valve piston, with an opening and closing valve mechanism for communicating and cutting between the relief chamber and the large diameter pressurizing chamber being provided.

4. The master cylinder according to claim 3, wherein the at least two ring seals are provided at the valve piston, and the diameter of the ring seal provided on the valve spring side is larger than that of the ring seal provided on the relief chamber side.

5. The master cylinder according to claim 3, wherein the valve cylinder is partitioned into three chambers, the relief chamber, the chamber formed between the ring seals and a damper chamber which stores the valve spring, by the two ring seals, and the valve piston is formed with a throttle path one end of which is opened to the relief chamber and the other end of which is opened to the damper chamber.

6. The master cylinder according to claim 1, further comprising

a reservoir for storing the brake fluid;

a cut-off portion on the large diameter pressurizing chamber side for cutting communication between the large diameter pressurizing chamber and the reservoir by being closed by the sliding movement of the stepped piston to the small diameter hydraulic chamber side; and

a cut-off portion on the small diameter hydraulic chamber side for cutting communication between the large diameter pressurizing chamber and the small diameter hydraulic chamber by being closed by the sliding movement of the stepped piston to the small diameter hydraulic chamber side, wherein

an ineffective stroke of the stepped piston until the cut-off portion on the small diameter hydraulic chamber side is brought into a closed state is made longer than an ineffective stroke of the stepped piston until the cut-off portion on the large diameter pressurizing chamber side is brought into a closed state.

7. The master cylinder according to claim 6, wherein the control valve includes a valve piston and a valve spring for urging the valve piston within a valve cylinder;

and the valve piston reduces the hydraulic pressure of the large diameter pressurizing chamber when a total force of a propulsive force produced by the hydraulic pressure of the small diameter hydraulic chamber and a propulsive force produced by the hydraulic pressure of the large diameter pressurizing chamber exceeds an urging force by the valve spring.

8. The master cylinder according to claim 7, wherein the control valve is provided with at least two ring seals between the valve cylinder and the valve piston to partition the inside of the valve cylinder, and a chamber formed between the ring seals and the small diameter hydraulic chamber communicate with each other;

and the valve spring is provided at one side of the valve piston, and a relief chamber for communicating to the reservoir and the large diameter pressurizing chamber is provided at the other side of the valve piston with an opening and closing valve mechanism for communicating and cutting between the relief chamber and the large diameter pressurizing chamber being provided.

9. The master cylinder according to claim 8, wherein the valve cylinder is partitioned into three chambers, the relief chamber, the chamber formed between the ring seals and a damper chamber which stores the valve spring, by the two ring seals, and the valve piston is formed with a throttle path one end of which is opened to the relief chamber and the other end of which is opened to the damper chamber.

10. A master cylinder comprising

a reservoir for storing a brake fluid;

a stepped cylinder having a large diameter cylinder portion and a small diameter cylinder portion;

a stepped piston having a large diameter piston portion slidably inserted into the large diameter cylinder portion of the stepped cylinder and a small diameter piston portion slidably inserted into the small cylinder portion;

a reverse flow checking opening and closing portion for partitioning the inside of the stepped cylinder into a large diameter pressurizing chamber on the large diameter piston portion side and a small diameter hydraulic chamber on the small diameter piston portion side and permitting a brake fluid to flow only from the large diameter pressurizing chamber side to the small diameter hydraulic chamber side;

a cut-off portion on the large diameter pressurizing chamber side for cutting communication between the large diameter pressurizing chamber and the reservoir by being closed by sliding movement of the stepped piston to the small diameter hydraulic chamber; and

a cut-off portion on the small diameter hydraulic chamber side for cutting communication between the large diameter pressurizing chamber and the small diameter hydraulic chamber by being closed by the sliding movement of the stepped piston to the small diameter hydraulic chamber side, the brake fluid being supplied from the large diameter pressurizing chamber side to the small diameter hydraulic chamber side by the opening operation of the reverse flow checking opening and closing portion by reducing a volume of the large diameter pressurizing chamber by the sliding movement of the stepped piston to the small diameter hydraulic chamber side, wherein

an ineffective stroke of the stepped piston until the cut-off portion on the small diameter hydraulic chamber side is brought into the closed state is made longer than an ineffective stroke of the stepped piston until the cut-off portion on the large diameter pressurizing chamber side is brought into a closed state.