JP2014088807A - Oil pump for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil pump which is light and compact and which has a low energy loss.SOLUTION: An outer rotor 5 is driven by disposing a follower chain sprocket 13 at the outer circumference of an outer rotor 5. An inner rotor 3 can be small-sized, as compared with a crankshaft drive type so that the running torque can be reduced while making the entirety compact. Bearing portions 15 of housings 6 and 7 are disposed to about such one half of the outer circumferences of the bearing portions 15 as is opposed in a pushing direction by a chain 14. The outer rotor 5 is pushed onto the bearing portions 15 by a chain cover so that stability is excellent and so that the volumes of the housings 6 and 7 can be reduced to save the weight.

Description

  The present invention relates to an oil pump provided in an internal combustion engine.

  In general, an oil pump for an internal combustion engine uses a trochoid pump in which an inner rotor and an outer rotor are surrounded by a housing, and the inner rotor is often directly connected to a crankshaft. However, this configuration inevitably has a problem that the inner rotor has a larger diameter than the crankshaft, so that it is difficult to make the inner rotor compact and the driving torque increases.

  Also, the crankshaft and the oil pump of another shaft type are provided close to the sprocket around which the timing chain is wound, and the timing chain and the oil pump are covered with a chain cover. In order to enclose the pump, the distance between the chain cover and the cylinder block has to be increased, and the engine body may be increased in size.

  On the other hand, for example, Patent Document 1 describes that the outer rotor is rotationally driven by disposing an oil pump at a position different from the crankshaft and providing a sprocket or the like on the outer periphery of the outer rotor. Since this type can reduce the size of the inner rotor, the overall size can be reduced. In the method of Patent Document 1, the outer peripheral surface of the outer rotor is rotatably supported. Therefore, in Patent Document 1, both sides of the outer peripheral surface of the outer rotor sandwiching the sprocket are mounted on the housing. A pair of bearing portions that are rotatably supported are provided, and the bearing portions are formed in a perfect circle covering the entire circumference of the outer rotor.

Japanese Patent Laid-Open No. 1-110818

  Now, when driving the outer rotor with a chain or gear, the outer rotor is pressed against the bearing by the chain or gear, but the pressing force only acts in one direction perpendicular to the rotational axis. Only affects the half circumference of the bearing. For this reason, in patent document 1, it can be said that a housing has a useless part and the weight increases more than needed.

  In addition, since an oil film exists between the inner peripheral surface of the bearing portion and the outer peripheral surface of the outer rotor, frictional resistance is generated over the entire circumference between the bearing portion and the outer rotor via the oil film. For this reason, there was a possibility that the sliding resistance was increased and the energy loss was increased. Further, although the chain and gear need to be lubricated with oil, the configuration of Patent Document 1 may require a special device such as an oil jet to lubricate the chain.

  The present invention has been made in view of such a current situation, and the point of rotating the outer rotor is to solve the problem while following Patent Document 1.

  An oil pump according to the present invention has an inner rotor and an outer rotor that are meshed with each other in a state where the rotation axis is shifted, and a housing that holds the two rotors so that they cannot be displaced in the axial direction. A driven portion made of a sprocket, a gear, or a pulley is provided in a portion of the outer peripheral surface of the outer rotor that enters inside from both end surfaces. When power is transmitted to the driven portion by transmission means, the outer rotor has its axis centered. A pressing force directed in one direction perpendicular to the axis acts.

  On the other hand, in the housing, a pair of bearing portions that support a portion outside the driven portion of the outer peripheral surface of the outer rotor are positioned only on the side of the outer peripheral surface of the outer rotor facing the one direction. It is provided to do.

  In the trochoid pump, the space formed by the recesses of the inner rotor and the outer rotor expands in accordance with the rotation in a region where the suction port is present, and sucks oil. On the other hand, in a region where there is a discharge port, the oil is discharged because the space is reduced in accordance with the rotation. And the pressure in a discharge port becomes high with the resistance of the oil path in the back of an oil pump.

  In the present invention, as a preferable configuration utilizing the characteristics of such a trochoid pump, the suction port and the discharge port can be arranged so that the direction is the one direction from the suction port to the discharge port. That is, the outer rotor can be arranged such that the side on which the discharge port is provided hits the bearing portion.

  In addition, the housing may be configured by a pair of split members. In this case, the housing can be integrally formed with the cylinder block and the chain cover (of course, the housing can be formed with a cylinder block or a chain). It is possible to use a member different from the cover, or to provide only one of the pair of housings on the cylinder block or the chain cover.

  In the present invention, since the outer rotor is supported not only by the entire circumference but by the bearing portion only partially, the housing can be made compact as compared with Patent Document 1, thereby contributing to the weight reduction of the internal combustion engine. . Moreover, since the frictional resistance between the outer rotor and the bearing portion can be significantly reduced, the power loss can be reduced and the fuel efficiency can be improved.

  And since the bearing part is provided in the position facing the direction where an outer rotor is pushed, an outer rotor is stably supported by a bearing part, without producing a backlash and center shift | offset | difference. Therefore, there is no problem with the bearing function. In particular, as described above, when the outer rotor is disposed such that the side on which the discharge port is provided contacts the bearing portion, the outer rotor is pushed against the bearing portion by the pressurized oil, so that the stability can be further improved.

  In addition, since the bearing portion of the housing is in a state where the front side is cut out in one direction, oil is allowed to ooze out between the housings 6 and 7 and the outer rotor 5. By transmitting the fluid to a driven part such as a driven chain sprocket, it is possible to lubricate the chain and gears without providing lubricating means such as an oil jet. This is also one of the great advantages of the present invention.

  Constructing the housing in a split system consisting of a pair of parts has the advantage of reducing the processing effort. Moreover, when the housing is integrally formed with the silicid block or the chain cover, the labor of member management can be reduced and the cost can be reduced.

It is a cross-sectional view of the first embodiment. It is the II-II sectional view taken on the line of FIG. It is a cross-sectional view of other embodiment.

  Next, an embodiment of the present invention will be described with reference to the drawings. First, the embodiment of FIG. 1 shown in FIGS. The oil pump 1 includes an inner rotor 3 having an outwardly uneven portion 2 on the outer periphery, an outer rotor 5 having an inwardly uneven portion 4 on the inner periphery, and first and second sandwiching both rotors 3 and 5 from the axial direction. And second housings 6 and 7. In the present embodiment, the first housing 6 is formed in an oil pump cover 8 that is provided separately or integrally with a chain cover that covers the valve drive mechanism drive chain, and the second housing 7 is integrated with the cylinder block 9. Is formed.

  The inner rotor 3 is rotatably held by the housings 3 and 5 by the inner shaft 10, while the outer rotor 5 is rotatably held by the housings 6 and 7. , 12 are offset by a certain dimension E.

  A driven chain sprocket 13 as an example of a driven portion is provided in an axially intermediate portion of the outer peripheral surface of the outer rotor 5, and a chain 14 as an example of a transmission means is wound around the chain sprocket 13. The chain 14 is also wound around a main drive chain sprocket provided on a crankshaft or the like. The driven chain sprocket 13 may be formed integrally with the outer rotor 5, or may be manufactured separately and fixed to the outer rotor 5 by an interference fit or the like.

  Both the housings 6 and 7 are formed in a circular shape when viewed from the direction of the rotational axis of the rotors 3 and 5, and are slightly spaced from the end surfaces of the rotors 3 and 5, and the inner shaft 10 is fixed in the shaft hole Has been. And the bearing parts 15 which support the one side which pinched | interposed the driven chain sprocket 13 among the outer peripheral surfaces of the outer rotor 5 are protrudingly provided in both the housings 6 and 7. FIG.

  In this embodiment, assuming that the tension direction of the chain 14 is the A direction and the slack direction is the B direction, and the alignment direction of the rotation axes 11 and 12 of the rotors 3 and 5 is the C direction, the A direction and the B direction are perpendicular to each other. The direction of the component force (the direction of the center line that symmetrically distributes the line in the A direction and the line in the B direction) is set so as to be substantially orthogonal to the C direction, and the bearing portion 15 is the outer periphery of the outer rotor 5. Of these, it is provided only in the range of a little less than a half circumference on the side facing the A direction. That is, assuming that the direction of the pressing force acting on the outer rotor 5 by the pulling action of the chain 14 is the D direction, the bearing portion 15 is formed so as to support only the portion of the outer rotor 5 facing the D direction. .

  In this embodiment, the bearing portion 15 is located between the tension side and the slack side of the chain 14 and is in a range smaller than 180 degrees. However, with this configuration, the bearing portion 15 is made to be a driven chain sprocket. 13 and the support stability can be improved. Of course, if the interference with the driven chain sprocket 13 is avoided, it can be formed in a range of 180 degrees.

  Since the shaft centers of the rotors 3 and 5 are arranged in the horizontal direction in FIG. 1, the suction port 16 and the discharge port 17 formed in the housings 6 and 7 are formed vertically symmetrically. The suction port 16 increases in width (cross-sectional area) from the start end toward the end, and the discharge port 17 decreases in width from the start end toward the end.

  The suction port 18 communicates with the start end portion of the suction port 16, and the discharge port 19 communicates with the end portion of the discharge port 17. In the present embodiment, the suction port 18 is formed in the cylinder block 9 and the discharge port 19 is formed in the chain cover 8, but the arrangement may be reversed, or both may be provided only in the cylinder block 9 or only in the chain cover 8. It is also possible to do. The suction port 18 and the discharge port 19 are not limited to the illustrated positions. The suction port 18 may be anywhere as long as it communicates with the suction port 18, and the discharge port 19 may be anywhere as long as it communicates with the discharge port 17.

  In the above configuration, the inner rotor 3 is held in the housings 6 and 7 by the inner shaft 10 so as not to drop off, and the outer rotor 5 is fitted to the inner rotor 3 so that the dropping is prevented. The bearings 15 of both housings 6 and 7 are rotatably held.

  In this case, the outer rotor 5 is pressed against the bearing portion 15 by the pulling action (or pressing action) by the chain 14, and is also pressed against the bearing portion 15 by the pressure of the oil filled in the discharge port 17, For this reason, the bearing portion 15 is held in a stable state despite being supported only about a half circumference.

  Since the bearing portions 15 of the housings 6 and 7 are provided with a little less than half of the circumferential direction, the weight can be reduced and the sliding resistance can be suppressed, thereby contributing to the improvement of fuel consumption. In addition, there is a slight gap between the inner surface of the housings 6 and 7 and the end surfaces of the rotors 3 and 5, but the suction port 16 has a low hydraulic pressure, so that there is no leakage that affects the discharge capacity. . Even if oil oozes out between the outer rotor 5 and the housings 6 and 7, the oil is transmitted to the driven chain sprocket 13, so that the driven chain sprocket 13 does not take any special lubrication means. And the chain 14 can be circulated.

  The chain cover 8 is fixed to the cylinder block 9 with a large number of bolts. Since the chain cover 8 is formed with a large number of bosses that contact the cylinder block 9, a gap between the chain cover 8 and the cylinder block 9 is formed. Although the distance dimension is kept constant, the inner shaft 1 can also function as a spacer for maintaining the distance between the chain cover 8 and the cylinder block 9. Further, the inner shaft 10 can be integrally formed with the cylinder block 9 or the chain cover 8.

  In the embodiment shown in FIG. 3, the alignment direction (C direction) of the rotation axes 11 and 12 of both rotors 3 and 5 and the pushing direction (D direction) of the bearing portion 15 by the chain 14 are set to be the same direction. doing. Therefore, in this embodiment, the suction port 16 and the discharge port 17 are arranged symmetrically. In FIG. 3, the cross section of the inner rotor 3 is not shown.

  The outer rotor 5 can also be driven by a timing belt or a gear. In the case of gear driving, a portion of the outer peripheral surface of the outer rotor opposite to the main driving gear is supported by the bearing portion. In the case of gear drive, it is possible to make the outer peripheral surface of the driven gear stick inside the outer peripheral surface of the outer rotor. In this case, the bearing portion is not separated into the left and right, and extends over the entire length in the axial direction of the outer rotor. It is also possible to provide (that is, a state in which the driven gear is straddled across the driven gear).

  The present invention is actually applicable to an internal combustion engine. Therefore, it can be used industrially.

DESCRIPTION OF SYMBOLS 1 Oil pump 3 Inner rotor 5 Outer rotor 6, 7 Housing 8 Oil pump cover 9 Cylinder block 10 Inner shaft 11, 12 Shaft center 13 Driven chain sprocket 14 as an example of a driven part 15 Chain 15 as an example of a transmission means 15 Bearing part 16 Suction port 17 Discharge port 18 Suction port 19 Discharge port

Claims (1)

An inner rotor and an outer rotor that rotate in mesh with each other with the rotational axis shifted, and a housing that holds the two rotors so that they cannot be displaced in the axial direction.
A driven portion made of a sprocket, a gear, or a pulley is provided at a portion of the outer peripheral surface of the outer rotor that enters inside from both end surfaces. When power is transmitted to the driven portion by a transmission means, the outer rotor has a shaft thereof. While a pressing force directed in one direction perpendicular to the center is acting,
In the housing, a pair of bearing portions for supporting a portion outside the driven portion of the outer peripheral surface of the outer rotor is positioned only on a side of the outer peripheral surface of the outer rotor facing the one direction. Provided in the
Oil pump for internal combustion engine.

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