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(11) | EP 1 024 282 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Control method and apparatus for variable discharge-type high pressure pumps |
| (57) A control valve (6a) and a check valve (4a) are provided from the upstream side in
the middle of a flow passage leading from a low pressure pump (P1) to a pressure chamber
(23a) which sucks low pressure fuel and pressure-feed it by its expansion and contraction
of displacement. A variable discharge-type high pressure pump sucks fuel into the
pressure chamber (23a) during a period until the control valve (6a) and the check
valve (4a) are closed, when the displacement of the pressure chamber (23a) expands.
The opening of the control valve (6a) is disabled if the pressure in an accumulation
chamber is higher than a target pressure by more than a tolerance, so that air admixed
in fuel from the low pressure pump (P1) is not allowed to flow into the upstream side
of the check valve (4a). Thus, fuel excess condition in the pressure chamber (23a)
which will be caused when the air expands due to lowering of pressure from a feed
pressure after closing of the control valve (6a) and forces out fuel into the pressure
chamber 23a is avoided, so that excessive pressure-feeding of fuel is prevented. |