Oil pump system
An oil pump system includes an oil pump, a first hydraulic passage, a second hydraulic passage, a return hydraulic passage, and a control valve. When a revolving speed of a rotor of the oil pump is low, and when a hydraulic pressure of a hydraulic oil, discharged out of a first outlet port of the oil pump to the first hydraulic passage, is lower than a predetermined value, a valve body of the control valve is placed at a first position, thereby joining the hydraulic oil, flowing in the first hydraulic passage, with the hydraulic oil, discharged out of a second outlet port of the oil pump to the second hydraulic passage, and delivering the thus joined hydraulic oil to a hydraulic oil receiving unit via a hydraulic-oil-delivery passage. When the revolving speed of the rotor is high, and when the hydraulic pressure of the hydraulic oil, discharged out of the first outlet port to the first hydraulic passage, is higher than the predetermined value, the valve body is placed at a second position, thereby inhibiting the hydraulic oil from joining, and delivering only the hydraulic oil, discharged out of the first outlet port to the first hydraulic passage, to the aforementioned destination. The oil pump system is downsized and lightweighted advantageously, and is improved in terms of work efficiency and on-boardability. The present invention has been developed in view of the aforementioned circumstances. It is therefore an object of the present invention to provide an oil pump system which employs means fop returning an excessive hydraulic oil to its inlet port without applying a large pressure to the discharged excessive hydraulic oil when the revolving speed of its rotor is increased to securely produce a specified hydraulic pressure. The returning means can return the excessive hydraulic oil directly to the inlet port, or it can return the hydraulic oil by way of a hydraulic oil reservoir. An oil pump system according to the present invention enables to improve work efficiency, and thereby it contributes to advantageously reducing driving horsepower of its oil pump. Moreover, the present oil pump system is downsized beneficially, and thereby it can be enhanced in terms of on-boardability when it is boarded on carriers like vehicle bodies.
Shanghai Kaida Pump Mfg. Co., Ltd.