Vane Pump

Abstract

A vane pump having two inner sidewalls of the housing, in which specified passages for pressure are provided in the walls, and, in addition, the vane may be provided with at least a radial slit on the radially inner part of the forward surface thereof, whereby the pressure pushing the vane outwardly against the circumferential wall of the cam ring is made about constant throughout the entire course of the vane including the sucking region and the exhausting region, and therefore, the pumpability is improved and the vibration and noise are minimized.

Description

This invention relates to improvements in a vane pump comprising a housing having an inlet and an outlet, a cam ring, and a rotor, in which the rotor is adapted to be rotated inside the cam ring and slid on two inner sidewalls of the housing and has a plurality of axial through-passages, which are radially outwardly extended into vane-guiding slots, in which vanes are adapted to be radially slidable, respectively.

It is well known that vanes are pushed against the inner circumferential wall of the cam ring for securing a high watertightness. It is also well known that a hydraulic pressure in the outlet is introduced into the axial through-passages for pushing the vanes which are radially outwardly slidable in vane-guiding slots extended from the axial through-passages. However, in accordance with this prior art, although a vane is strongly pushed by the pressure of liquid introduced in the axial through-passage during the vane is travelling in a sucking region of the cam ring, it is disadvantageous that the vane is not so sufficiently pushed as above when the vane arrives at the proximity of the close of an exhausting region of the cam ring, because of the fact that the hydraulic pressure acting on the vane from the interior inside the cam ring varies in accordance with the travelling of the vane from the sucking region to the exhausting region so that the two pressures are balanced with each other when the vane is travelling in the end portion of the exhausting region. By virtue of the variation in balancing the two pressures, the pumpability is deteriorated and vibration and noise are caused.

The primary object of this invention is to provide a vane pump of the class described, in which the variation in balancing the two pressures is minimized.

Another object of this invention is to provide a vane pump of the class described, of which the pumpability is remarkably improved.

Still another object of this invention is to provide a vane pump of the class described, which is well prevented from generation of vibration and noise.

Briefly stated in accordance with one aspect of this invention, there is provided a vane pump comprising a housing having at least a pair of an inlet and an outlet, a cam ring, and a rotor, the rotor being adapted to be rotated inside the cam ring and slid on two inner sidewalls of the housing and having a plurality of axial through-passages, which are radially outwardly extended into vane-guiding slots, in which vanes are adapted to be radially slidable, respectively. The vane is adapted to be radially outwardly pressured by liquid introduced into the axial through-passages from the outlet and radially inwardly pressured by an inner circumferential wall of the cam ring. An annular groove is formed in one of the two inner sidewalls, arranged in such a position as to always communicate with the outlet and with an end of the axial through-passages, and provided with throttles positioned on the same radii with both circumferential ends of the inlet. A segmental groove is formed in the other of the two inner sidewalls, arranged in such a position as to communicate with the inlet intermediate still another throttle and with the other end of the axial thorugh-passages, and circumferentially extended between points radially corresponding to the both circumferential ends of the inlet. In addition, the vane may be provided with a plurality of radial slits formed in the forward surface thereof, the slits being extended from the radially inner end thereof to points positioned somewhat radially outer than the periphery of the rotor when the vane is radially most outwardly positioned while being in contact with the cam ring.

The invention will be better understood and other objects and additional advantages of the invention will become apparent upon perusal of the following description taken in connection with the drawings, in which:

FIG. 1 is an axially sectional view of a vane pump embodying this invention;

FIG. 2 is a partly removed cross-sectional view thereof taken along the line 2-2 in FIG. 1;

FIG. 3 is another partly removed cross-sectional view thereof taken along the line 3-3 in FIG. 1;

FIG. 4 is an enlarged front view of a vane;

FIG. 5 is a side elevational view thereof;

FIG. 6 is an explanatory view of the exhausting stroke, in which the cross sections of a vane and arrangement of the annular groove are shown;

FIG. 7 is an explanatory view of the sucking stroke, in which the cross sections of a vane and arrangement of the segmental groove are shown; and

FIG. 8 shows the interrelation of pressure to the arrangement of the annular groove, the segmental groove, and the slit.

Similar numerals refer to similar parts throughout the several views.

Referring more particularly to the drawings, the preferred embodiment of this invention will now be described; however, this description will be understood to be illustrative of the invention and not as limiting it to the particular construction as shown and described. There is a housing 11 having a cavity having an inlet 16 and an outlet 17. A pressure plate 19 and a wear plate 20 are arranged in opposition to each other in the cavity. A cam ring 12 is arranged between the pressure plate 19 and the wear plate 20 in the cavity. An inner periphery of the cam ring 12 constitutes a pumping chamber together with opposite inner sidewalls of the pressure plate 19 and the wear plate 20. The contour of the inner periphery of the cam ring 12 resembles an ellipse, but actually it is formed with a pair of larger circular parts, a pair of smaller circular parts, and two pairs of cam curve parts, each connecting the larger circular part with the smaller circular part, so that this vane pump is of two strokes, as shown in FIGS. 2 and 3.

A rotor 13 is arranged inside the pumping chamber. Both plane surfaces of the rotor 13 are adapted to be slid on the plane surfaces of the inner walls of the pressure plate 19 and the wear plate 20, respectively. The rotor 13 is provided with a plurality of axial through-passages 34 arranged on a coaxial cylinder, which are radially outwardly extended into vane-guiding slots 14, respectively. A vane 15 is adapted to be radially slidable in the vane-guiding slot 14 and to be circumferentially travelled in accordance with the contour of the inner periphery of the cam ring 12 when the rotor 13 is externally rotated as in the prior art.

The inlet 16 is divided into two sucking ports 116 and 216 formed through the pressure plate 19 and the wear plate 20 so as to communicate the inlet 16 with the pumping chamber as shown in FIGS. 2 and 3. The outlet 17 is divided into two exhausting ports 117 and 217 formed through the pressure plate 19 so as to communicate the outlet 17 with the pumping chamber as shown in FIG. 2. The pressure plate 19 is provided with an annular groove 18 formed in the inner sidewall thereof and arrange in such a position as to be always communicate with the outlet 17 through a pair of passages 22 and the exhausting ports 117 and 217 and with an end of the axial through-passage 34. The annular groove 18 is provided with a pair of first throttles 41 and a pair of second throttles 42, of which the positions are referred to in detail hereinafter.

In accordance with this invention, the wear plate 20 is provided with a pair of segmental grooves 21 formed in the inner sidewall thereof and arranged in such a position as to communicate with the inlet 16 through a pair of third throttles 45 and the sucking ports 116 and 216 and with the other end of the axial through-passage 34. The segmental groove 21 is circumferentially extended from a point 46 axially corresponding to the first throttle 41 to another point 47 axially corresponding to the second throttle 42, as shown in FIGS. 3, 7 and 8.

In the embodiment in accordance with this invention, the vane 15 is provided with a plurality of radial slits 24 formed in the forward surface thereof. The radial slit 24 is extended from the radially inner end of the vane 15 to a point 48 positioned radially outer than the periphery of the rotor 13 when the vane 15 is radially most outwardly positioned or in contact with the larger circular part of the cam ring 12.

Reference is now made to FIG. 8 showing the interrelation of pressure to the construction. In the upper part of FIG. 8 the ordinate represents the differential pressure subjected to the unit area of the vane 15, while the abscissa represents time of the travelling vane. In the lower part of FIG. 8 arrangements of the annular groove 18 and the segmental groove 21 are shown relatively to positions of a vane 15, in which the annular groove 18 and the segmental groove 21 are deformed into rectilinear ones. The annular groove 18 comprises two pairs of throttles 41 and 42 as stated hereinbefore, which divide the annular groove 18 into a pair of longer parts 118 and a pair of shorter parts 218. The outlet 17 is communicated with the pair of exhausting ports 117 and 217, each of which is communicated with the longer part 118 intermediate the passage 22. The longer part 118 is communicated with a shorter part 218 intermediate the two throttles 41 and 42, so that, during the axial through-passage 34 is communicated with the longer part 118, the pressure of the liquid in the axial through-passage 34 introduced from the outlet 17 is higher than that during the axial through-passage is communicated with the shorter part 218 by virtue of the throttles 41 and 42. During the axial through-passage 34 is communicated with the longer part 118 from the throttle 42 to the throttle 41, the outer end of the vane 15 travels along a larger circular part, is pushed inwardly by a cam curve part, and again travels along a smaller circular part. During the axial through-passage 34 is communicated with the shorter part 218 from the first throttle 41 to the second throttle 42, the outer end of the vane 15 protrudes outwardly and travels along another cam curve part of the inner periphery of the cam ring 12, by which the protruded outer end is retained. During this period it is required to avoid a too high pressure subjected to the inner end of the vane 15, balancing with the low pressure subjected to the outer end of the vane 15, which becomes as low as 0 kg./cm.sup.2.

The segmental groove 21 is positioned axially correspondingly to the shorter part 216 of the annular groove 18 and communicated with the sucking port of the inlet 16 through the third throttle 45. An excessive liquid in the axial through-passage 34, which causes the too high pressure, is delivered to the segmental groove 21, whence the liquid is returned to the sucking port 116 and 216 through the third throttle 45. By virtue of the segmental grooves 21 arranged as above, the above-stated avoidance of the too high pressure subjected to the inner end of the vane 15 travelling along the cam curve part corresponding to the sucking port of the inlet 16 is secured.

In FIG. 6, the cam curve part of the inner periphery of the cam ring 12 and the annular groove 18 are shown as deformed into straight lines. It is to be understood that one of the vanes 15 and one of the axial through-passages 34 are travelling from left to right through three positions, D, E, and F. Although the outer end of the vane 15 is in contact with the larger circular part of the cam ring 12 at the position D, the outer end is subsequently pushed inwardly by the cam curve part of the cam ring 12 successively at the positions E and then F. During the above period, the axial through-passage 34 is communicated with the longer part 118 of the annular groove 18 so that the inner end of the vane 15 is directly affected by the high pressure of the liquid in the outlet 17 which balances with the inward pushing action rendered by the cam curve part.

In FIG. 7, another cam curve part of the inner periphery of the cam ring 12 and the segmental groove 21 are shown as deformed into straight lines. It is to be understood that one of the vanes 15 and one of the axial through-passages 34 are travelling from left to right through three positions, A, B, and C. The cam curve part of the cam ring 12 is gotten away from the rotor 13 as the rotor rotates and in accordance therewith the vane 15 is outwardly protruded as it travels from the position A to the position B. When the outer end of the vane 15 passes the boundary of the cam curve part with the larger circular part of the cam ring 12, the axial through-passage 34 passes the end point 47 of the segmental groove 21 and is disengaged from the latter so that the communication of the axial through-passage 34 with the segmental groove 21 is interrupted between the positions B and C.

In operation, when the rotor 13 is externally rotated, a liquid is transferred from the inlet 16 to the outlet 17 through the sucking ports 116 and 216, the pumping chamber, and the exhausting ports 117 and 217 as usual. The higher pressure of the liquid at the outlet 17 is transmitted therefrom to the liquid contained in the vane-guiding slots 14 through the exhausting ports 117 and 217, the annular groove 18 and the axial through-passages 34 so as to push the vane 15 radially outwardly against the inner periphery of the cam ring 12.

When the vane 15 is positioned at A and B, since the pressure pushing the vane 15 inwardly into the vane-guiding slot 14 becomes very low and rather zero, the pressure pushing the vane 15 outwardly against the cam ring 12 is made also appreciably low by virtue of the communication of the axial through-passage 34 with the segmental groove 21, the pressured liquid contained in the axial through-passage 34 being returned to the sucking ports 116 and 216 through the segmental groove 21 and the third throttle 45, so that the pressure acting on the vane 15 is balanced with the lowered inward pressure, and therefore, it is avoided that the vane 15 is pushed outwardly against the cam ring 12 by an excessively high pressure.

When the vane 15 is travelling from the position B to the position C, the outer end of the vane 15 is transferred from a state in contact with the cam curve part of the cam ring 12 to another state in contact with the larger circular part thereof. Since the axial through-passage 34 has been disengaged from the segmental groove 21, it is communicated only with the annular groove 18, and particularly with the longer part 118 thereof, and therefore, the vane 15 is pushed outwardly by the high pressure introduced from the outlet 17. However, when the axial through-passage 34 has been disengaged from the segmental groove 21, the vane 15 is protruded outwardly to the point 48 out of the periphery 49 of the rotor 13 so that the outer end of the radial slits 24 is exposed in the pumping chamber and the axial through-passage 34 is communicated with the pumping chamber through the radial slits 24, and therefore, the high pressure in the axial through-passage 34 is leaked from it to the pumping chamber little by little so as to relieve the pressure subjected to the vane 15.

When the vane 15 arrives at the position D, the contact of the outer end thereof with the larger circular part of the cam ring 12 is transferred to that with another cam curve part thereof, so that the vane 15 is pushed inwardly by the cam curve part. About at the position E, the radial slits 24 are hidden inside the periphery 49 of the rotor 13 so that the communication from the axial through-passage 34 to the pumping chamber is interrupted. Thus at the position F, the pressure subjected to the inner end of the vane 15 is made appreciably high so as to balance with the inward pressure rendered by the cam curve part.

In the upper part of FIG. 8, a variation in the differential pressure acting on the vane 15 is shown by a full line, which represents a case where the segmental groove 21 is provided but the radial slits 24 are not. By virtue of the provision of the radial slits 24, the full line stepped at the position corresponding to the end 47 of the segmental groove 21 is smoothed as shown by a broken line.

By virtue of this invention, the differential pressure acting on the vane 15 for protruding it is made about constant throughout the entire round travelling course of the vane 15, not concerning with variation in pressure in the pumping chamber.

It is to be understood that the positions of the throttles 41 and 42, the degree of throttling thereof, and the number, form and length of the radial slits 24 may be selected depending upon the characteristics of a pump.

While particular embodiment of this invention has been illustrated and described, modifications thereof will readily occur to those skilled in the art. It should be understood therefore that the invention is not limited to the particular construction disclosed but that the appended claims are intended to cover all modifications which do not depart from the true spirit and scope of the invention.

Claims

What I claim as new and desire to be secured by Letters Patent of the United States is:

1. In a vane pump comprising a housing having at least a pair of inlets and a pair of outlets, a cam ring, and a rotor,

said rotor being adapted to be rotated inside said cam ring and slidable on two inner sidewalls of the housing and having a plurality of axial through-passages,

each axial through-passage being radially outwardly extended into a vane-guiding slot, in which a vane is adapted to be radially slidable,

said vane being adapted to be radially outwardly pressured by liquid introduced into said axial through-passage from said outlets and radially inwardly pressured by an inner circumferential wall of said cam ring,

an annular groove formed in one of said two inner sidewalls, arranged in such a position as to always communicate with said outlets and with an end of said axial through-passage, and provided with two throttles positioned on the same radii with both circumferential ends of each inlet, respectively, and

segmental grooves formed in the other of said two inner sidewalls, each segmental groove arranged in such a position as to communicate with each inlet through still another throttle and with the other end of said axial through-passage, and circumferentially extended between two points corresponding to said both circumferential ends of each inlet.

2. The combination of claim 1 and wherein

said vane is provided with a plurality of radial slits formed in the forward surface thereof,

said slit being extended from the radially inner end thereof to a point positioned radially outwardly of the periphery of said rotor when said vane is in contact with said cam ring and said segmental groove is disengaged from said axial through-passage.

3. The combination of claim 1 and wherein

the contour of the inner periphery of said cam ring comprises a pair of larger circular parts, a pair of smaller circular parts, and two pairs of cam curve parts, each connecting the larger circular part with the smaller circular part, so that the vane pump is of two strokes.