| 摘要 |
The vacuum pump (5) to supply low pressure air to a vehicle brake booster, is powered by an electric motor (6) and is mounted in series in a low pressure pipe (2) between the brake booster (1) and the vehicle engine suction tube (13). A branch pipe (8) by-passes the vacuum pump (5) and is provided with a non-return valve (9) so that the pump motor (6) can be switched on or off. When the engine is running, the reduced pressure in the suction tube (13) is controlled by a butterfly valve (14) and provides sufficient vacuum to operate the brake booster (1) through the branch pipe (8). If the vacuum in the suction tube (13) becomes insufficient, the vacuum pump (5) is switched on by a sensor, to provide sufficient vacuum to operate the brake booster.
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