Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2002-08-08
2004-06-15
Butler, Douglas C. (Department: 3683)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S010000, C418S135000, C418S171000
Reexamination Certificate
active
06749272
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority of Japanese Patent Application No. 2001-242672 filed on Aug. 9, 2001, the content of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotary pump, in particular, an internal gear pump such as a trochoid pump with higher discharge pressure and a brake apparatus having the same.
2. Description of Related Art
JP-A-2000-179466 shows a rotary pump, as an internal gear pump such as a trochoid pump or the like. The rotary pump is comprised of a drive shaft, an inner rotor having outer teeth portions and an outer rotor having inner teeth portions and a casing for containing the inner and outer rotors. The inner and outer rotors contained in the casing form a plurality of teeth gap portions surrounded by inner teeth portions of the outer rotor and outer teeth portions of the inner rotor which are in mesh with each other.
An intake port and a discharge port are separately disposed on opposite sides of a pump center line passing through the respective rotation axes of the inner and outer rotors. When the drive shaft is rotated for driving the pump, the inner rotor is rotated by the drive shaft on an axis of the drive shaft and, according to the rotation of the inner rotor, the outer rotor is rotated in the same direction. As the respective volumes of the teeth gap portions between the inner and outer teeth portions are varied every turn of the rotating inner and outer rotors, fluid is sucked from the intake port and discharged to the discharge port.
In the conventional rotary pump mentioned above, there is provided two side sealing members one of which seals an upper side clearance between the axial end surfaces of the rotors and the casing and the other of which seals a lower side clearance therebetween. Each of the side sealing members is composed of a resin member and an elastic member such as rubber which urges the resin member toward the outer and inner rotors.
It is not preferable from a cost standpoint to apply two pieces of the side sealing member, which are relatively expensive, to the rotary pump. Accordingly, it is contemplated that one of the upper and lower side clearances is sealed by the conventional resin side sealing member and the other of the upper and lower side clearances is sealed with mechanical sealing due to a direct contact between the axial end surfaces of the rotors and the casing.
For a purpose of assuring the mechanical sealing, it is necessary for the axial end surfaces of the rotors that are made of metal to be strongly pressed against the axial end surface of the casing that is also made of metal. If the contact frictional resistance is larger and, thus, torque loss is larger, a body of the rotary pump has to be larger to secure a given discharge output of the pump.
Further, if the sliding contact surface between the axial end surfaces of the rotors and the casing has a portion where the torque loss is relatively larger and another portion where the torque loss is not so large, frictional heat generated at the portion where the torque loss is large causes to expand metal material of the rotors and the casing, when the pump is rotated at high speed for a long time, so that the discharge output of the pump is damaged and deteriorated.
In the conventional rotary pump, the axial end surfaces of the outer and inner rotors and the axial end surface of a side plate, which are opposed to each other, are provided with parallel straight line gliding stripes formed by flat face grinding. If the axial end surfaces of outer and inner rotors and the side plate having the parallel straight line grinding stripes are in pressurized direct contact with each other for the mechanical sealing, there exist local portions of the sliding contact surface therebetween where the frictional resistance are larger and the torque loss are larger.
In a case as a typical example, as shown in
FIG. 9
, that an entire axial end surface of the side plate is provided with parallel straight line grinding stripes extending straight in parallel in a direction of connecting an intake port and a discharge port and entire axial end surfaces of the outer and inner rotors are also provided with parallel straight line grinding stripes, at a pair of arch shaped portions of the side plate positioned above a maximum volume closed teeth gap portion and below a minimum volume closed teeth gap portion in
FIG. 9
, lines of the parallel straight line grinding stripes extend straight in parallel without crossing the teeth gap portions formed by the outer and inner rotors in mech. Accordingly, fluid hardly flows from the teeth gap portions to these arch shaped portions through extremely slight gaps formed by slight concave and convex of the sliding stripes of the side plate.
On the other hand, there also exist a pair of arch shaped portions of the outer rotor where lines of the parallel straight line grinding stripes extend straight in parallel without crossing the teeth gap portions. Accordingly, when the lines of the parallel straight line grinding stripes of the side plate coincide with the lines of the parallel straight line grinding stripes according to the rotation of the rotors, that is, when the arch shaped portions of the side plate and the outer rotor are completely overlapped with each other, fluid lubrication is very poor at the arch shaped portions overlapped, since the extremely slight gaps formed by the sliding stripes of the side plate and the outer rotor do not communicate with the teeth gap portions. As the outer rotor rotate, the lines of the parallel straight line grinding stripes of the side plate and the outer rotor come to cross each other. However, the lines of the parallel straight line grinding stripes of the outer rotor that extend so as to cross the teeth gap portions gradually cross the lines of the parallel straight line grinding stripes on the arch shaped portion of the side plate. Therefore, fluid lubrication on the arch shaped portion of the side pate is inherently poor and the torque loss at the arch shaped portion is larger as shown in FIG.
9
.
Torque loss is relatively small, as shown in
FIG. 9
, at contact surface portions of the side plate other than the arch shaped portions thereof, that is, at portions radially outside the teeth gap portions and perpendicular to a line of connecting the arch shaped portions, since the lines of the parallel straight line grinding stripes extend so as to always cross the teeth gap portions at these portions, irrelevant to the rotation angle of the outer rotor.
Further, if the axial end surfaces of the side plate and the outer rotor are provided with circumferential line grinding stripes, majority lines of the circumferential line grinding stripes at the contact surface between the side plate and the outer rotor do not extend to cross the teeth gap portions so that the fluid lubrication is very poor and the torque loss is larger on the contact surface therebetween.
The portions where the torque loss is larger are confirmed by extensive experimental tests of the present inventors from standpoints that larger torque results in larger heat generation and smaller torque in smaller heat generation, when the outer and inner rotors rotate, since, if the contact surfaces between the side plate and the outer and inner rotors are well lubricated by the fluid, the frictional resistance of the contact surfaces is smaller with less frictional heat and, if the contact surfaces are not well lubricated, the frictional resistance thereof is larger with more frictional heat.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a rotary pump in which axial end surfaces of outer and inner rotors are in direct contact with an axial end surface of side plate (inner side surface of a casing) with less and/or uniform torque loss.
It is another object of the present invention to provide a brake apparatus having a hydraulic circuit in which the rotary pump
Hakamada Naoki
Satou Takashi
Uchiyama Kazunori
Yamaguchi Takahiro
Butler Douglas C.
Denso Corporation
King Bradley
Posz & Bethards, PLC
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