Master cylinder

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 pressurizing chamber 56.

1. A master cylinder comprising:
 a stepped cylinder comprising a large diameter cylinder portion and a small diameter cylinder portion;  
 a stepped piston comprising a large diameter piston portion slidably inserted into the large diameter cylinder portion and a small diameter piston portion slidably inserted into the small diameter cylinder portion;  
 a reservoir for storing a brake fluid; and  
 a reverse flow checking opening and closing portion for partitioning an inside of the stepped cylinder into a large diameter pressurizing chamber and a small diameter hydraulic chamber, and for permitting the brake fluid to flow from a large diameter pressurizing chamber side to a small diameter hydraulic chamber side, the reverse flow checking opening and closing portion being opened by a reduction in volume of the large diameter pressurizing chamber by sliding movement of the stepped piston toward 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 a rise in a hydraulic pressure of the small diameter hydraulic chamber; 
 wherein the control valve comprises 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 propulsive force produced by the hydraulic pressure of the small diameter hydraulic chamber and propulsive force produced by the hydraulic pressure of the large diameter pressurizing chamber exceed an urging force produced by the valve spring;  
 wherein the control valve comprises at least two ring seals between the valve cylinder and the valve piston to partition an inside of the valve cylinder, and a chamber formed between the at least two ring seals and the small diameter hydraulic chamber communicate with each other;  
 wherein the valve spring is at a first side of the valve piston, a relief chamber communicating the reservoir and the large diameter pressurizing chamber is at a second side of the valve piston, and the control valve comprises an opening and closing valve mechanism for establishing or cutting off communication between the relief chamber and the large diameter pressurizing chamber;  
 wherein the valve cylinder is partitioned by the two ring seals into a relief chamber, a chamber formed between the two ring seals, and a damper chamber that stores the valve spring; and  
 wherein the valve piston comprises a throttle path one end of which opens to the relief chamber and the other end of which opens to the damper chamber.  
 
 
     
     
       2. A master cylinder comprising:
 a stepped cylinder comprising  having a large diameter cylinder portion and a small diameter cylinder portion;  
 a stepped piston comprising  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;  
 a reservoir for storing a brake fluid; and  
 a reverse flow checking opening and closing portion for partitioning an inside of the stepped cylinder into a large diameter pressurizing chamber and a small diameter hydraulic chamber, and for permitting the brake fluid to flow from a large diameter pressurizing chamber side to a small diameter hydraulic chamber side, the reverse flow checking opening and closing portion being opened by a reduction in volume of the large diameter pressurizing chamber by sliding movement of the stepped piston toward 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 in response to a sliding movement of the stepped piston towards 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 in response to a sliding movement of the stepped piston 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 a rise in a hydraulic pressure of the small diameter hydraulic chamber; 
 wherein an ineffective stroke of the stepped piston to bring the cut-off portion on the small diameter hydraulic chamber side into a closed state is longer than an ineffective stroke of the stepped piston to bring the cut-off portion on the large diameter pressurizing chamber side into a closed state; 
 wherein the control valve comprises a valve cylinder integrally provided to the stepped cylinder, a valve piston received in the valve cylinder 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 propulsive  a total of a first force produced by the hydraulic pressure of the small diameter hydraulic chamber and propulsive  a second force produced by the hydraulic pressure of the large diameter pressurizing chamber exceed an urging force produced by the valve spring;  
 wherein the control valve comprises at least two ring seals between the valve cylinder and the valve piston to partition an inside of the valve cylinder, and a chamber formed between the two ring seals and the small diameter hydraulic chamber communicate with each other; and  
 wherein the valve spring is at a first side of the valve piston, a relief chamber communicating the reservoir and the large diameter pressurizing chamber  is at a second side of the valve piston, and the control valve comprises an opening and closing valve mechanism for  having a seal portion secured at the second side of the valve piston for opening or closing a port of the valve cylinder through which the relief chamber communicates with the large diameter pressurizing chamber, the opening and closing mechanism, by means of the seal portion, establishing or cutting off communication between the relief chamber and the large diameter pressurizing chamber. ; and  
   wherein the valve piston keeps the opening and closing valve mechanism open to thereby adjust the hydraulic pressure of the large diameter pressurizing chamber to that of the reservoir while the first force produced by the hydraulic pressure of the small diameter hydraulic chamber exceeds the urging force produced by the valve spring.   
 
 
     
     
       3. The master cylinder of  claim 2 , wherein the valve cylinder is partitioned by the two ring seals into a relief chamber, a chamber formed between the two ring seals, and a damper chamber that stores the valve spring; and
 wherein the valve piston comprises a throttle path one end of which opens to the relief chamber and the other end of which opens to the damper chamber.  
 
     
     
       4. The master cylinder according to  claim 2 ,
   wherein 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 in response to a sliding movement of the stepped piston toward the small diameter hydraulic chamber side.     
     
     
       5. The master cylinder according to  claim 4 ,
   wherein an ineffective stroke of the stepped piston to bring the cut - off portion on the small diameter hydraulic chamber side into a closed state is longer than an ineffective stroke of the stepped piston to bring the cut - off portion on the large diameter pressurizing chamber side into a closed state.     
     
     
       6. The master cylinder according to  claim 2 ,
   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.     
     
     
       7. A master cylinder comprising:
   a stepped cylinder having a large diameter bore and a small diameter bore;        a stepped piston having a large diameter piston slidably inserted into the large diameter bore of the stepped cylinder and a small diameter piston slidably inserted into the small diameter bore;        a reservoir for storing a brake fluid;        a reverse flow checking valve configured to partition an inside of the stepped cylinder into a large diameter pressurizing chamber and a small diameter hydraulic chamber,        wherein the reverse flow checking valve is opened by a reduction in a volume of the large diameter pressurizing chamber caused by a sliding movement of the stepped piston toward the small diameter hydraulic chamber, thereby permitting the brake fluid to flow from the large diameter pressurizing chamber to the small diameter hydraulic chamber; and        a control valve configured to gradually reduce a hydraulic pressure in the large diameter pressurizing chamber as a hydraulic pressure in the small diameter hydraulic chamber rises, the control valve comprising:      a valve cylinder integrally provided to the stepped cylinder;        a valve piston slidably inserted into the valve cylinder;        a valve spring configured to urge the valve piston at one side thereof in a first direction within the valve cylinder;        at least two ring seals provided between the valve cylinder and the valve piston to partition an inside of the valve cylinder;        a chamber formed between the at least two ring seals, wherein the chamber is in communication with the small diameter hydraulic chamber, and the hydraulic pressure of the small diameter hydraulic chamber imposes a first force on the valve piston in a direction opposite to the first direction;        a relief chamber that is in communication with the reservoir, wherein the hydraulic pressure of the large diameter pressurizing chamber imposes a second force on the valve piston in a direction opposite to the first direction via a port of the valve cylinder which communicates between the relief chamber and the large diameter pressurizing chamber; and        a valve mechanism comprising a seal portion secured to the other side of the valve piston for opening and closing the port of the valve cylinder to thereby establish and cut off communication between the relief chamber and the large diameter pressurizing chamber, wherein:      the valve piston moves against the valve spring to open the valve mechanism to establish communication between the relief chamber and the large diameter pressurizing chamber, thereby reducing the hydraulic pressure of the large diameter pressurizing chamber, when a total of the first force produced by the hydraulic pressure of the small diameter hydraulic chamber and the second force produced by the hydraulic pressure of the large diameter pressurizing chamber exceeds an urging force by the valve spring; and        the valve piston keeps the valve mechanism open to thereby adjust the hydraulic pressure of the large diameter pressurizing chamber to that of the reservoir while the first force produced by the hydraulic pressure of the small diameter hydraulic chamber is greater than the urging force by the valve spring.         
     
     
       8. The master cylinder according to  claim 7 ,
   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.     
     
     
       9. The master cylinder according to  claim 1 ,
   wherein the valve piston keeps the opening and closing valve mechanism open to thereby adjust the hydraulic pressure of the large diameter pressurizing chamber to that of the reservoir while the first force produced by the hydraulic pressure of the small diameter hydraulic chamber exceeds the urging force produced by the valve spring.     
     
     
       10. The master cylinder according to  claim 1 ,
   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.