| 摘要 |
PURPOSE:To improve reliability in a valve, by constituting it to operate only in case of less than the specified pressure including time of a failure in a front- wheel side brake hydraulic circuit ut in case of more than the specified pressure, to make its original operation securable. CONSTITUTION:If a brake hydraulic circuit is normal, a brake fluid in a front- wheel side fluid chamber 2b of a tandem type master cylinder 2 becomes more than the specified pressure, so that engagement of a dent part of a piston rod 25a is released and, after reaching a hydraulic pressure control starting point to be secured according to vehicle weight, the hydraulic pressure increment rate of an outflow port 5 is more decreased than that of an inflow port 3 according to a pressure receiving areal difference of a deformed spool 6, thereby preventing an early lock of rear wheels from occurring. However, at the time of a failure in a front-wheel side brake hydraulic circuit, the brake fluid in the front wheel side fluid chamber 2b becomes less than the specified pressure, whereby the piston rod 25a is being engaged in the dent part 6a of the deformed spool 6. Therefore, a fail-safe mechanism 23 will not function with only a pressure up of the brake fluid of a rear-wheel side fluid chamber 2a of the cylinder 2, so that braking force larger than normalcy is generated, braking the vehicle.
|
