| 摘要 |
PROBLEM TO BE SOLVED: To provide a positive displacement type pump equipped with a means driving a pump plunger to the direction of return. SOLUTION: A high pressure positive displacement type pump suitable for feeding fuel to a fuel injection system, includes one or more than one of pump assemblies 2, 3 and 4. Each pump assembly is equipped with a cylinder block 1 partitioning a pump cylinder 12. In the inside of the pump cylinder 12, a pump plunger 13 is provided in such a way that it can be moved while being slid. The respective pump plungers 13 are connected with each tappet assembly 20. Each tappet assembly 20 includes a tappet shell 21 provided in such a way that it can be moved while being slid in the inside of a hole 22. When it use, each tappet assembly 20 is engaged with a cam 6 so as to allow the pump planger 13 to be driven to the pump feeding direction. Each working fluid chamber 30 is partitioned at the opposite side of the cam 6 in the respective tappet assemblies 20. When in use, pressurized working fluid is fed to each working fluid chamber 30 so as to allow each tappet and each pump planger to be driven to the direction of return. In this constitution, any return spring for the pump planger is not required.
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