Oil pump pressure control device

Abstract

A device for reducing friction in a variable flow rate oil pump in which two discharge ports are provided and which uses three rotors while maintaining characteristics identical to the pressure characteristics of a common oil pump. The device is configured from a first discharge passage to an engine, a return passage that returns to an intake side of an outer circumferential side rotor, a second discharge passage to the engine, a return passage that returns to an intake side of an inner circumferential side rotor, and a pressure control valve whose valve main body is provided between a discharge port from the inner circumferential side rotor and the first discharge passage. The first discharge passage and second discharge passage are coupled, and a flow passage control is executed in each of: a low revolution range in a state in which only the first discharge passage and the second discharge passage are open; an intermediate revolution range in a state in which the first discharge passage and second discharge passage are open and a first intake side of the return passage is closed while a second intake side of the return passage is open; and a high revolution range in a state in which the second discharge passage is closed while the first discharge passage and the return passage are open.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an oil pump pressure control device for a variable flow rate oil pump in which two discharge ports are provided and which uses three rotors as means for provision of the two discharge sources thereof that facilitates reduced friction while maintaining pressure (oil pressure) characteristics not in multi stage characteristics but in characteristics identical to the pressure characteristics of a common oil pump based on a newly devised method of switching oil passages.[0003]2. Description of the Related Art[0004]As disclosed in Japanese Unexamined Patent Application No. H11-280666, the use of three rotors that themselves serve as means for transporting oil to two locations is well known in the conventional art. Japanese Unexamined Patent Application No. H11-280666 refers only to means for transporting oil to two locations and makes no reference to the subsequent effects thereof.SUMMARY OF ...

AI Technical Summary

Benefits of technology

[0012]A significant merit of the invention of claim 1 is that, even in variable flow rate oil pumps that use three rotors, a pressure ratio determined at the design stage can eliminate the other pressure difference produced by the discharge passages and return passages and can prevent a middle rotor from which the inner circumferential side rotor is configured from being pressed to one side whereupon, in turn, friction on the teeth surface can be prevented and the durability thereof improved. A further effect thereof is that at times of high-speed revolution of the outer circumferential side rotor and the inner circumferential side rotor the second discharge passage of the inner circumferential side rotor is fully closed so as to form the inner circumferential side rotor as an independent circuit whereupon, even in the absence of the generation of a superfluous work pressure by the inner circumferential side rotor, there is no drop in overall pump pressure. In addition, because work=pressure×flow rate, the superfluous work can be reduced so long as the pressure is lowered and, because the outer circumferential side rotor pump (main pump) and the inner circumferential side rotor pump (sub pump) are not in communication, the sub pump pressure is significantly lowered.

[0013]In addition, because the inner circumferential side pump (sub pump) forms an independent circuit at times of high revolution, if the opened area return passage of the pump is increased more oil can be discharged and the pump pressure further reduced. Because a single discharge port is not partitioned into two for two discharge sources thereof and instead a single discharge port can be established for each, the flow rate is not partitioned. Accordingly, because the rotor diameter of the three rotors can be reduced and the slide area of the rotors decreased comparative to a common single rotor assembly, the friction (torque) can be reduced and the pump efficiency increased. An additional merit of the invention is that, because the three rotors can be configured as a rotor having a dual-rotor assembly, the superfluous work of one rotor can be reduced. The invention of claim 2 affords an identical effect to the effect afforded by the invention of claim 1.

[0014]In addition, as well as an effect identical to the effect afforded by the invention of claim 1, the invention of claim 3, based on the provision of a simple pressure control valve, affords a reduction in the number of component parts. In addition, the invention of claim 4, based on the provision of a 3-valve-type pressure control valve, facilitates a pressure control by which desired values can be better approximated.

Problems solved by technology

More particularly, a pressure difference is generated between the space between the inner-side teeth and the space between the outer-side teeth due to the characteristics of the inner-side tooth profile and the outer-side tooth profile which, as a result, there is a fear of the middle rotor being pressed against one side and, in turn, of the wear of the teeth surface thereof being accelerated.

In other words, a significant drawback inherent to this device pertains to the generation of biased wear on the middle rotor caused by pressure difference.

While the efficiency can be increased by the adoption of this kind of variable flow rate oil pump, the following problems are inherent thereto.

That is to say, there is a drawback inherent to this device in that, because the discharge port of the single rotor assembly thereof is partitioned into two, the opened area of the respective discharge passages thereof is reduced and the rotor diameter must be increased to compensate for this reduction, and this increase in rotor diameter results in increased friction (torque) and a drop in efficiency.

In addition, despite the aim of the device being increased efficiency based on a variable capacity specification for eliminating superfluous work, an undesirable drop in efficiency occurs.

Furthermore, because the discharge port of the single rotor assembly is simply partitioned into two, the rotor characteristics of the two discharge ports are of course equivalent and, accordingly, there is a limit to the degree of freedom available in terms of the distribution ratio of the two discharge amounts.

There is an additional drawback in that, because the two discharge sources constitute a discharge from the same rotor, overlapping of the discharge pulse timing occurs and an overlapping and magnification of the noise and vibration thereof occurs.

Another drawbacks pertains to the rotor being a single rotor assembly and, accordingly, to the fact that there is no means available for reducing superfluous work when it occurs.

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