Rotary expansible chamber devices – Positively actuated vane – Fluid biased
Reexamination Certificate
1999-12-09
2001-03-20
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
Positively actuated vane
Fluid biased
C418S081000, C418S082000, C418S268000
Reexamination Certificate
active
06203303
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vane pump used as a hydraulic source of a power steering apparatus, more particularly, to such a vane pump in which ability in projection of vanes is enhanced when a rotation of a rotor of the pump is started.
2. Description of the Related Art
Conventionally, there is of such a vane pump described in Japanese Patent Publication (Kokai) No. 9-32740 (1997).
In such a conventional vane pump, it is composed of a rotor rotatably disposed in a cam ring, plural vanes projectably provided in corresponding slits formed in the rotor, and a pair of sidewall members (an end surface of a body and a side plate) provided to close both side portion of the cam ring. With this configuration, a pump operation is performed with rotation of the rotor as the vane slidably contacts its top portion and its side surfaces with an inner surface of the cam ring and with surfaces of the side wall members facing with the vane.
In such a vane pump, it is appeared such a phenomenon that the pump operation is not started immediately when the rotation of the rotor of the pump is started, because the vane is not sufficiently projected from the slit of the rotor.
After the pump has been driven, the vane is projected until its top portion contacts the inner surface of the cam ring by discharged pressure of the pump that is introduced into a backpressure groove formed in each of the sidewall members. However, just after the rotation of the rotor of the pump is started in a condition that the pumping operation is not started, only a centrifugal force upon rotation of the rotor contributes on the projection of the vane, so that the projection thereof cannot sufficiently performed in such a condition.
As a result of an analysis of this phenomenon in the applicant, when a vane
60
in slit
510
formed in a rotor
50
is rotated with the rotor
50
, pressing force “F” that presses the vane
60
onto one of inside walls of the slit
510
(backward in a rotational direction of the rotor
50
) acts on the vane
60
, as shown in FIG.
1
. Therefore, the projection of the vane
60
is prevented by this pressing force “F”. As a result of further analysis, it is discovered such that the phenomenon that the vane
60
is pressed onto the inside wall of the slit
510
is caused by slide resistances of the side surface of the vane
60
with inside surface of the both sidewall members.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a vane pump in which projection of vanes is improved by reducing slide resistance that is caused with side surfaces of the vane contacting inside walls of sidewall members just when a rotation of a rotor of the pump is started.
Briefly, a vane pump according to the present invention is composed of a rotor that is rotatably disposed in a cam ring attached to a housing, a plurality of vanes that are slidably disposed in corresponding slits formed in the rotor in which the vane is projected from the slit upon rotation of the rotor, a pair of sidewall members that close both side portions of the cam ring to form a cavity defined by the cam ring and the sidewall members, a plurality of annular backpressure grooves that are depressively formed on contact surfaces of the sidewall members with the rotor in which adjacent two of the backpressure grooves are communicated with each other through a communication passage to introduce discharged pressure into an inside end portion of each of the slits, and depressions that are formed on at least one of the contact surfaces of the rotor with the sidewall members in which the depressions are not contacted with a part of side surfaces of each of the vanes.
With this configuration, a slide resistance in the contact area of the side surface of the vane with the both sidewall members is reduced, so that pressing force that presses the vane onto an inside surface of the slit (backward in the rotational direction of the rotor) is diminished. Namely, the pressing force that prevents the vane from projecting when the rotation of the rotor of the conventional vane pump is started is diminished, so that a pump operation is smoothly started just when the pumping operation is initiated.
Further, the vane pump according to the present invention includes such a construction that each of the depressions is formed radially outside of the backpressure groove within a range at least where the backpressure groove is formed in a circumferential direction of the rotor. According to this configuration, it can be obtained such an effect similar to that in the prior configuration.
Furthermore, the vane pump according to the present invention provides such a configuration that each of the depressions is formed in an entire circumferential area from a pre-compression area of the pump to a discharge area in a rotational direction of the rotor. In this situation, the depression is formed in an area where the vane is most efficiently projected, so that the additional machining to the sidewall members can be performed in minimum.
The depression is continuously formed in the circumferential direction, so that it continuously can be machined by a cutting tool such as an end-mill. Therefore, the machining time can be diminished compared with that of the conventional pump. According to this configuration, it can be also obtained such an effect similar to that in the prior two configurations.
Moreover, the depression is formed so as to be communicated with the backpressure groove or the communication passage. With this configuration, a radial width of a portion that remains as a flat portion radially outside of the depression in a contact area of the rotor with each of the sidewall members can be formed to be larger than a case that the depression is formed independently of the backpressure groove and the communication passage. Therefore, ability in seal of the depression in the radial direction can be maintained sufficiently, and also the feature similar to all of the prior configuration can be obtained.
REFERENCES:
patent: 4386891 (1983-06-01), Riefel et al.
patent: 4610614 (1986-09-01), Haga et al.
patent: 4611977 (1986-09-01), Shibuya et al.
patent: 5154593 (1992-10-01), Konishi et al.
patent: 5188522 (1993-02-01), Hara
patent: 5226802 (1993-07-01), Nakamura et al.
patent: 5490770 (1996-02-01), Oogushi
patent: 4119207 (1991-12-01), None
patent: 2315815 (1998-11-01), None
patent: 60-256580 (1985-12-01), None
patent: 63-147980 (1988-06-01), None
patent: 63-167089 (1988-07-01), None
patent: 64-080784 (1989-03-01), None
patent: 2-108881 (1990-04-01), None
patent: 7-29261 (1995-07-01), None
patent: 7-217548 (1995-08-01), None
patent: 9-32740 (1997-02-01), None
Fujiwara Hidetoshi
Yamamori Motoyasu
Yamauchi Kentaro
Denion Thomas
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Toyoda Koki Kabushiki Kaisha
Trieu Theresa
LandOfFree
Vane pump does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vane pump, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vane pump will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2524339