| 摘要 |
<p>A vehicle brake system includes a check valve (24) having an input port coupled to a fluid pump outlet (14) and an output port coupled to hydraulically deactuated spring brakes (50) through brake lines. A pilot check valve (30) has a pilot port, an inlet port coupled to the input port of the check valve (24) and a return port coupled to the fluid reservoir (12). The pilot port is coupled to the output port of the check valve so the pilot check valve opens only when the output port is pressurized. This allows hydraulic fluid to flow from the pump (6), through the pilot check valve (30) and to the reservoir. To set the brakes when stopped or in emergency situations the operator actuates a valve (72) which dumps the fluid in the brake lines into the reservoir. A second pilot check valve has its pilot port connected to a brake pedal actuated master cylinder, its inlet connected to the brake line and its outlet connected to the reservoir. Pressing on the brake pedal connects the brake line to the reservoir through a variable restriction so to allow the spring brakes to be applied in the modulated manner of service brakes.</p> |
