Abstract:
This invention relates to an oil pump apparatus which comprises an oil pump housing, a rotor rotatably located in the oil pump housing, the rotor forming a first set of pockets having a capacity increasing toward a rotating direction of the rotor and a second set of pockets having a capacity decreasing toward the rotating direction of the rotor, a plurality of suction ports connected with the first set of pockets, each of the suction ports being isolated from other adjacent suction ports, a discharge port connected with the second set of the pockets, and a control valve which includes a valve member, an urging member for urging the valve member and an urging member&#39;s chamber for disposing the urging member, the control valve being operatively positioned to control fluid flow through the plurality of the suction ports and the discharge port, and the control valve is operatively connected to select between a first condition in which the control valve connects with the suction ports and a second condition in which the control valve connects the discharge port with one of the suction ports and cuts off the other suction ports wherein the urging member&#39;s chamber is always communicated with one of the suction ports.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an oil pump apparatus for a vehicle, and more particularly, an oil pump apparatus which has a higher pressure when the revolution of a drive source, for example a crankshaft of an internal combustion engine, increases. 
     BACKGROUND OF THE INVENTION 
     In Unexamined Published Japanese Patent Application (Kokai) No. Hei 9-256969, for example, there is disclosed a conventional oil pump apparatus. The conventional oil pump apparatus comprises: an oil pump housing, a rotor rotatably located in the oil pump housing, the rotor forming a first set of pockets having a capacity or volume increasing toward a rotating direction of the rotor and a second set of pockets having a capacity or volume decreasing toward the rotating direction of the rotor, a plurality of suction ports connected with the first set of pockets, each of the suction ports being isolated from other adjacent suction ports, a discharge port connected with the second set of the pockets, and a control valve which includes a valve member, a spring for urging the valve member and a spring chamber for disposing the spring, the control valve being operatively positioned to control fluid flow through the plurality of the suction ports and the discharge port, and the control valve is operatively connected to select between a first condition in which the control valve connects with the suction ports and a second condition in which the control valve connects the discharge port with one of the suction ports and cuts off the other suction ports. 
     In the above conventional oil pump apparatus, when the revolving speed of the rotor is increased to obtain more discharged hydraulic pressure of the hydraulic oil than necessary, the surplus discharged hydraulic pressure is supplied to one of the suction ports by the control valve. As a result, the oil pump apparatus becomes more efficient. 
     Here, in the above conventional oil pump apparatus, since the volume of the spring chamber is varied with respect to the movement of the valve member, the spring chamber opens to the atmosphere such that the variation of the pressure of the spring chamber does not prevent the valve member from sliding. However, the opening of the spring chamber draws the air in the oil pump apparatus, when the oil pump apparatus is rotated. Thus, there is some concern that the air drawing makes the oil pump apparatus become inefficient and noisy. 
     SUMMARY OF THE INVENTION 
     The present invention provides an oil pump apparatus without the foregoing drawbacks. 
     In accordance with the present invention, an oil pump apparatus comprises an oil pump housing; a rotor rotatably located in the oil pump housing, the rotor forming a first set of pockets having a capacity increasing toward a rotating direction of the rotor and a second set of pockets having a capacity decreasing toward the rotating direction of the rotor; a plurality of suction ports connected with the first set of pockets, each of the suction ports being isolated from other adjacent suction ports; a discharge port connected with the second set of the pockets; and a control valve which includes a valve member, an urging member for urging the valve member and an urging member&#39;s chamber for disposing the urging member, the control valve being operatively positioned to control fluid flow through the plurality of the suction ports and the discharge port, and the control valve is operatively connected to select between a first condition in which the control valve connects with the suction ports and a second condition in which the control valve connects the discharge port with one of the suction ports and cuts off the other suction ports, wherein the urging member&#39;s chamber is always communicated with one of the suction ports. 
     Other advantages of invention will become apparent during the following discussion of the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     The foregoing and additional features of the present invention will become more apparent from the following detailed description of a preferred embodiment thereof when considered with reference to the attached drawings, in which: 
     FIG. 1 is a diagrammatic illustration view of an oil pump apparatus in accordance with the present invention, when the revolving speed of the rotor is at low speed; 
     FIG. 2 is a sectional view of a control valve in accordance with the present invention, when the revolving speed of the rotor is from low speed to middle speed; 
     FIG. 3 is a sectional view of a control valve in accordance with the present invention, when the revolving speed of the rotor is from middle speed to high speed; 
     FIG. 4 is a sectional view of a control valve in accordance with the present invention, when the revolving speed of the rotor is at high speed; and 
     FIG. 5 is a graph illustrating an outlet-amount characteristic which is exhibited by the oil pump apparatus in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An oil pump apparatus in accordance with a preferred embodiment of the present invention will be described with reference to the attached drawings. 
     FIG. 1 is a diagrammatic illustration view of an oil pump apparatus. The oil pump apparatus is adapted for mounting on a vehicle and is actuated by a crankshaft of an internal combustion engine. An oil pump  1  of the oil pump apparatus is provided with an oil pump housing  1   a  which is made of metal, such as an aluminum-based alloy or an iron-based alloy. In the oil pump housing  1   a , a pump chamber  1   a   1  is formed. In the pump chamber  1   a   1 , an outer rotor  3  is rotatably disposed. The outer rotor  3  is provided with a plurality of internal gear teeth  11  so as to constitute a driven gear. Further, in the pump chamber  1   a   1 , an inner rotor  2  is rotatably disposed therein and is located inside the outer rotor  3 . An axis of the outer rotor  3  and an axis of the inner rotor  2  are placed within a predetermined distance. The inner rotor  2  is connected to the crankshaft of the internal combustion engine, and is rotated together with the crankshaft. In general, the inner rotor  2  is designed to rotate at a revolving speed of 600 to 7,000 rpm. 
     On an outer periphery of the inner rotor  2 , a plurality of external gear teeth  21  is provided so as to constitute a drive gear. The internal gear teeth  11  and the external gear teeth  21  are designed to be a trochoid curve or a cycloid curve. The inner rotor  2  is rotated in the direction of the arrow A 1  of FIG.  1 . As the inner rotor  2  is rotated, the external gear teeth  21  of the inner rotor  2  engage with the internal gear teeth  11  of the outer rotor  3  one after another. Accordingly, the outer rotor  3  is rotated in the same direction. Between the internal gear teeth  11  and the external gear teeth  21 , there is formed pump room which has eleven pockets  22   a  through  22   k  as shown in FIG.  1 . In FIG. 1, the pocket  22   a  has the largest volume of the pockets  22   a  through  22   k , and the pocket  22   f  has the smallest volume of the same. 
     The pockets  22   g  through  22   k , which are disposed in the upstream with respect to the pocket  22   a , produce an inlet pressure, because their volumes enlarge as the inner rotor  2  is rotated, and they act to suck the hydraulic oil. The pockets  22   b  through  22   f , which are disposed in the downstream with respect to the pocket  22   a , produce an outlet pressure, because their volumes diminish as the inner rotor  2  is rotated, and they act to discharge the hydraulic oil. 
     In the oil pump housing  1   a  of the oil pump  1 , a discharge port  33  is formed. The discharge port  33  is connected to the pockets  22   b  through  22   f , and is adapted to discharge the hydraulic oil out of the pump chamber  1   a   1  as the inner rotor  2  is rotated. In the oil pump housing  1   a , on the other hand, suction ports  31  are formed. The suction ports  31  consist of two suction ports  31   a  and  31   b . The suction port  31   a  is connected to the pockets  22   g  through  22   i  and the suction port  31   b  is connected to the pocket  22   k.    
     In the preferred embodiment, the suction port  31   b  is disposed downstream with respect to the suction port  31   a  in the rotary direction of the inner rotor  2  designated at the arrow A 1 . The opening area of the suction port  31   a  is larger than the opening area of the suction port  31   b . As can be appreciated from FIG. 1, contact points E 1  and E 2  between the internal gear teeth  11  and the external gear teeth  21  are positioned between the suction port  31   a  and the suction port  31   b . Accordingly, the suction port  31   a  and the suction port  31   b  do not communicate with each other along the peripheral direction of the pump chamber  1   a   1  Thus, the suction port  31   a  and the suction port  31   b  are adapted to suck the hydraulic oil independently of each other. One end of a suction hydraulic passage  66  is connected to the suction port  31   a  and the other end of the suction hydraulic passage  66  is connected to an oil store member, such as an oil pan  69 , a reservoir, or an oil tank. The hydraulic oil is returned to the oil pan  69  from a hydraulic oil receiving unit  80 . 
     A hydraulic-oil-delivery passage  5  is a passage which is adapted for delivering a hydraulic pressure of the hydraulic oil to the hydraulic oil receiving unit  80 . The hydraulic-oil-delivery passage  5  has a branch passage  6 . The branch passage  6  is connected to a first valve port  71  of a control valve  7 . 
     The control valve  7  is located in the oil pump housing  1   a . The control valve  7  is provided with a valve chamber  78 , the first valve port  71 , a second valve port  74 , a third valve port  73 , a valve member  77  and a spring or urging member  79 . The first valve port  71  is communicated with the hydraulic-oil-delivery passage  5  via the branch passage  6 . The second valve port  74  is communicated with the suction port  31   b  via a first intermediate hydraulic passage  63 . The third valve port  73  is communicated with the suction port  31   a  via a second intermediate hydraulic passage  62 . Both the first intermediate hydraulic passage  63  and the second intermediate passage  62  are formed in the oil pump housing  1   a . In addition, the valve chamber  78  which is formed in the oil pump housing  1   a . The valve chamber  78  is provided with a side passage  74   a  and a side passage  73   a . The side passage  74   a  is disposed at the second valve port  74 , the side passage  73   a  is disposed at the third valve port  73 . Note that the valve member  77  is slidably fitted into the valve chamber  78 , and is urged by the spring  79  in the rightward direction of FIG.  1 . The valve member  77  includes a first land portion  77   b  and a second land portion  77   a . The valve chamber  78  is divided into three rooms which are a head room  75 , an intermediate room  76  and a spring room  79   a  by the land portions  77   a  and  77   b  as shown in FIG.  1 . The first valve port  71  is communicated with the head room  75 . The second valve port  74  with side passage  74   a  is controlled to communicate with the head room  75  and the intermediate room  76  by the first land portion  77   b  of the valve member  77 , according to the pressure in the head room  75 . The third port  73  with the side passage  73   a  is controlled to communicate with the head room  75  and the intermediate room  76  by the first land portion  77   b  of the valve member  77 , according to the pressure in the head room  75 . Here, as shown in FIG. 4, the axial length L 1  of the first land portion  77   b  in the direction of the valve chamber  78  is smaller than the axial length L 2  of the side passage  73   a , is also smaller than the axial length L 3  of the side passage  74   a . The second land portion  77   a  of the valve member  77  has a passage  77   c  which connects the intermediate room  76  and the spring room  79  to each other. Therefore, the spring room  79  is always connected with the third port  73 . 
     As a result, the control valve  7  is able to engage either a first condition where the second port  74  and the third port  73  communicate with each other so as to communicate the suction port  31   a  with the suction port  31   b  as shown in FIG. 1, a second condition where the first port  71  and the second port  74  communicate with each other via the head room  75  so as to communicate the branch passage  6  with the suction port  31   b  as shown in FIG. 3, and a third condition where the first port  71 , the second port  74  and the third port  73  communicate with each other via the head room  75  so as to communicate the branch passage  6  with the suction port  31   a  and the suction port  31   b  as shown in FIG.  4 . Since the axial length L 1  of the first land portion  77   b  is smaller than the axial length L 3  of the side passage  74 , the control valve  7  is controlled to communicate between the third port  73  and the second port  74  via the intermediate room  76 , and between the second port  74  and the first port  71  via the head room  75  in the transitional period from the first condition to the second condition. 
     In the above preferred embodiment, the volume of the spring room  79   a  is varied according to the movement of the valve member  77 . However, the spring room  79  is always communicated with the third port  73  via the intermediate room  76  such that the pressure in the spring room  79  is the same as the pressure at the third port  73 . Therefore, the valve member  77  is able to slide smoothly. In addition, since the axial length L 1  of the first land portion  77   b  is smaller than the axial length L 2  of the side passage  73 , the third port  73  is not closed by the first land portion  77   b  on the transitional period from the second condition to the third condition. Thus, the spring room  79   a  is able to communicate with the third port  73  on the transitional period from the second condition to the third condition such that the valve member  77  is able to slide smoothly. Here, the spring room  79   a  is communicated with the suction port  31   a  such that there is no need to make an independent passage on the oil pump housing  1   a . As a result, the oil pump apparatus of the preferred embodiment becomes smaller and it becomes possible to make the oil pump apparatus at relatively low cost. 
     An operation of the above preferred embodiment of the present oil pump apparatus will be hereinafter described. 
     When the revolving speed of the crankshaft of the internal combustion engine is low (the first condition), the pressure of the hydraulic-oil-delivery passage  5  and the branch passage  6  does not slide the valve member  77  against the spring  79  so that the suction port  31   a  and the suction port  31   b  communicate with each other. This means that the pockets  22   g  though  22   k  are able to suck the hydraulic oil, as shown in FIG.  1 . Therefore, in the oil pump  1 , the pockets  22   g  though  22   k  suck the hydraulic oil from the oil pan  69  via the suction ports  31   a  and  31   b , and the pockets  22   b  though  22   e  discharge the hydraulic oil to the hydraulic-oil-delivery passage  5  via the discharge  77  port  33 . The discharged hydraulic oil is delivered to the hydraulic oil receiving unit  80 . 
     In this case, the characteristic of the total outlet amounts, whose revolving speed is low (revolving speed N, 0&lt;N&lt;N), is obtained as shown in FIG.  5 . FIG. 5 is a graph, which schematically illustrates the relationships between the revolving speeds of the internal combustion engine and the output amounts of the above preferred embodiment of the oil pump apparatus. The dotted line “_” of the drawing specifies that the characteristic of the total outlet amounts, which are sucked from both of the suction ports  31   a  and  31   b . The alternate-long-and-short dash line “- - - ” of the drawing specifies that the characteristic of the total outlet amounts, which are sucked from either the suction ports  31   a  or the suction port  31   b . The characteristic of the total outlet amounts, whose revolving speed is low, is consistent with the dotted line “- - - ”. Therefore, the required amount of the discharged hydraulic oil is obtained. 
     On the other hand, when the revolving speed of the internal combustion engine is from N 1  to N 2 , for instance from 1,500 rpm to 2,500 rpm, the revolving speed of the inner rotor  2  is increased accordingly. Under these circumstances, the amount of the hydraulic oil discharged out of the discharge port  33  is increased, and thereby the hydraulic pressure is increased to more than a predetermined pressure (PN 1 ) in the hydraulic-oil-delivery passage  5 . Eventually, the actuating force in the head room  75  to the valve member  77  (the actuating force which occurs due to the pressure (PN 1 ) in the hydraulic-oil-delivery passage  5 ), is increased to overcome the urging force of the spring  79 , and accordingly, as can be understood from FIG. 2, the valve member  77  is slid in the leftward direction contracting the spring  79  elastically. Thus, when the valve member  77  of the control valve  7  is placed at the transition condition, the land portion  77   b  communicates the second port  74  with the intermediate room  76  and the head room  75 . In this condition, the suction port  31   a  (the pockets  22   g  through  22   i ) sucks the hydraulic oil from the oil pan  69 , and the suction port  31   b  (the pocket  22   k ) sucks the hydraulic oil from the suction port  31   a  via the second intermediate hydraulic passage  62 , the third port  73 , the intermediate room  76 , a part of the second port  74  and the first intermediate hydraulic passage  63 . At the same time, the suction port  31   b  sucks the hydraulic oil from the hydraulic-oil-delivery passage  5  via the branch passage  6 , the first port  71 , the head room  75 , a part of the second port  74  and the first intermediate hydraulic passage  63 . In this case, the characteristic of the total outlet amounts, whose revolving speed area is in the transition condition (N 1 &lt;N&lt;N 2 ), is obtained as shown in FIG.  5 . Here, when the valve member  77  is slid from the position described in FIG. 1 to that described in FIG. 2, the volume of the spring room  79   a  becomes accordingly small. The spring room  79   a  is communicated with the suction port  31  via the passage  77   c , the intermediate room  76 , the third port  73  and the second intermediate hydraulic passage  62  such that the valve member  77  is able to slide smoothly. 
     When the revolving speed of the internal combustion engine is 15 from N 2  to N 3 , for instance, from 2,500 rpm to 4,000 rpm, the revolving speed of the inner rotor  2  is further increased accordingly. As can be understood from FIG. 3, the actuating force in the head room  75  to the valve member  77  (the actuating force which occurs due to the pressure (PN 2 ) in the hydraulic-oil-delivery passage  5 ), is increased to overcome the urging force of the spring  79 , and accordingly, the valve member  77  is slid in the leftward direction contracting the spring  79  elastically. Thus, the valve member  77  of the control valve  7  is placed at the second condition, whose revolving speed is at middle speed. In the second condition, the land portion  77   b  closes the communication between the second port  74  and the third port  73 . The suction port  31   a  (the pockets  22   g  through  22   i ) sucks the hydraulic oil from the oil pan  69 . At the same time, the suction port  31   b  (the pocket  22   k ) sucks the hydraulic oil from the hydraulic-oil-delivery passage  5  via the branch passage  6 , the first port  71 , the head room  75 , the second port  74  and the first intermediate hydraulic passage  63 . In this case, the characteristic of the total outlet amounts, whose revolving speed area is the second condition (N 2 &lt;N&lt;N 3 ), is obtained as shown in FIG.  5 . As also shown in FIG. 5, the characteristic of the total outlet amounts of the second condition is the difference of the characteristic of the suction port  31   b  subtracted from the characteristic of the total outlet amounts whose revolving speed area is low. Here, when the valve member  77  is slid from the position described in FIG. 2 to that described in FIG. 3, the volume of the spring room  79   a  becomes accordingly small. The spring room  79   a  is communicated with the suction port  31  via the passage  77   c , the intermediate room  76 , the third port  73  and the second intermediate hydraulic passage  62  such that the valve member  77  is able to slide smoothly. 
     Furthermore, when the revolving speed of the internal combustion engine is increased, for instance, to more than 4,000 rpm, the revolving speed of the inner rotor  2  is increased accordingly. As can be understood from FIG. 4, the actuating force in the head room  75  to the valve member  77  (the actuating force which occurs due to the pressure (PN 3 ) in the hydraulic-oil-delivery passage  5 ) is increased to overcome the urging force of the spring  79 , and accordingly, the valve member  77  is further slid in the leftward direction contracting the spring  79  elastically. Thus, the valve member  77  of the control valve  7  is placed at the third condition, whose revolving speed is high. In the third condition, the land portion  77   b  communicates the third port  73  with the head room  75 . Therefore, both the suction ports  31   a  and  31   b  suck the hydraulic oil from the hydraulic-oil-delivery passage  5 . The characteristic of the total outlet amounts, whose revolving speed area is the third condition (N 3 &lt;N), is obtained as shown in FIG.  5 . Here, when the valve member  77  is slid from the position described in FIG. 3 to that described in FIG. 4, the volume of the spring room  79   a  become accordingly small and the land portion  77   b  does not close the third port  73 . 
     Therefore, the spring room  79   a  is communicated with the suction port  31   a  via the passage  77   c , the intermediate room  76 , the third port  73  and the second intermediate hydraulic passage  62  such that the valve member  77  is able to slide smoothly.