GB1533774A - Adaptive braking modulator - Google Patents

Abstract

1533774 Pressure reducing valves; valves BENDIX CORP 20 Feb 1976 [10 March 1975] 06854/76 Headings F2F and F2V An adaptive braking modulator 32, for reducing brake pressure in response to an electrical signal, comprises a piston 64 acted on by a high pressure, communicated from a booster via inlet 48, valve 94 and passage 86 during normal brake application, to maintain valve 66 in an open condition allowing unrestricted flow between an inlet port 36 from a master cylinder and an outlet 38 to the brakes, the modulator also comprising a solenoid to operate valve 94 such that communication between inlet 48 and passage 86 is closed by rod 120 when an incipient skid signal is detected and communication is simultaneously opened between passage 86 and a low pressure outlet 44 causing rightward movement of piston 64 under the action of spring 78 resulting in the closure of valve 66 to isolate inlet 36 from outlet 38. Continued operation of the solenoid results in the expansion of chamber 54 under the action of the pressure therein to further reduce brake pressure. The inlet 48 is also permanently communicated with a chamber 104, the pressure therein acting on a piston 70 to maintain a valve 72 in a closed position unless there is a failure causing a drop in booster pressure whereupon spring 78 will open valve 72 to allow unrestricted flow from inlet 36 to outlet 38 regardless of the position of valve 66. The pressure at inlet 48 is communicated to the hollow inside of piston 122 housing rod 120 through passage 102, 131, splines 133 and passages 134 so that the solenoid valve need not overcome any pressure differential across rod 120 and thus may be operated by a relatively small current. In a second embodiment a first valve, being normally open to connect the inlet from the master cylinder to the brakes, is operated by a piston normally acted on by low pressure and a second valve controlling the expansible chamber to reduce brake pressure is operated by a piston normally acted on by high booster pressure. Operation of the solenoid moves a spool valve to connect the piston operating the first valve to high pressure to close it while simultaneously connecting the piston operating the second valve to low pressure to open it. Two valves as described above are incorporated into a split front/rear braking circuit, one in each circuit, the system also including power steering run off the same pump as the brakes.