JP2009209817A - Oil pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent erosion of an oil pump, such as, gear pump. <P>SOLUTION: A shallow bottom part 29a, a V-shaped trough part 29b and a vertical wall 29c are formed in an upstream-side end part of an oil delivery groove 29 formed in a pump casing 21. The shallow bottom part 29a is formed shallower than a downstream side part in the oil delivery groove 29, and is formed into a flat surface substantially parallel to a bottom surface of the pump casing 21. The V-shaped trough part 29b is positioned on the outer peripheral side of the shallow bottom part 29a, and is formed in a substantially V shape in a cross-sectional shape, when it is cut in the radial direction in an outer rotor 32, and in a shape that has the depth increase as well as the width widen, as going toward the downstream side from the upstream side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oil pump such as a gear pump provided in an automatic transmission of a vehicle.

  Conventionally, as an oil pump as described above, an inner rotor and an outer rotor that are meshed with each other are rotatably accommodated in a pump casing, a pump chamber is formed between contact points of both rotors, and both It is known that the rotation center of the rotor is decentered by a predetermined amount, and a drive shaft for rotating the inner rotor is connected to the inner rotor. In this type of oil pump, along with the synchronous rotation of the inner rotor and the outer rotor meshing with the inner rotor, oil is sucked into the pump chamber between the two rotors through a suction groove formed in the pump casing, and pressurized in the pump chamber. Then, it is discharged out of the pump through the discharge groove formed in the pump casing.

  In the oil pump as described above, when the opening area between the discharge groove and the pump chamber suddenly increases with the rotation of the two rotors, the oil pressure in the pump chamber changes rapidly, so that the cavitation is near the opening. Erosion due to the above occurs and damages the inner surface of the pump casing and the rotor.

  Therefore, on the side opposite to the rotor rotation direction of the discharge groove (discharge port), there is provided a shallow bottom portion having a substantially rectangular plane shape having a width substantially the same as the discharge groove and shallower than the discharge groove. A technique is known that attempts to prevent sudden changes in oil and erosion of the oil in the pump chamber by reducing the opening area between the pump chamber (working chamber) and the discharge groove by the amount. In addition, by forming a tip portion having a V-shaped planar shape and a shallower depth than the discharge groove on the side opposite to the rotor rotation direction of the discharge groove, the pump chamber is firstly connected with the rotation of both rotors. The pump reaches the top of the tip and communication with the discharge groove is started, and the opening area between the pump chamber and the discharge groove gradually increases in a nearly uniform state with the rotation of both rotors. A technique is known that suppresses a rapid change in indoor oil pressure and prevents erosion (see, for example, Patent Document 1).

In addition, for example, the shape of the discharge groove (discharge port) is such that the width of the bottom surface near the end on the opposite side of the rotor rotation direction gradually decreases toward the end, and the port side inclination angle decreases. By forming it, the oil flowing from the pump chamber to the discharge groove is concentrated near the center in the width direction near the end, and is smoothly discharged to maintain the oil pressure substantially constant and suppress the occurrence of cavitation. The technique to be performed is also known (for example, see Patent Document 2).
JP 2004-332696 A (paragraphs 0007, 0009, 0011, 0013, FIGS. 1 and 6) JP-A-1-273877 (second page, lower left column, lower right column, FIGS. 6 and 9 to 12)

  However, the above-mentioned conventional method can be considered to relieve a sudden change when the oil in the pump chamber flows into the discharge groove or smooth the oil flow. It has been difficult to reliably prevent the erosion.

  The inventors of the present application have found that as a result of repeating various experiments and simulations to find out the cause, the oil flow in the pump is not a static flow. When a high-speed flow having a vector collides with the wall surface on the outer peripheral side of the discharge groove, a reverse flow occurs. When this reverse flow collides with a forward flow near the start position of the discharge groove, a turbulent state occurs. In addition, since such a flow state changes dynamically, the action considered to be obtained by the conventional method is not always stably obtained. It is thought that erosion occurs due to a hammer phenomenon caused by cavitation. Therefore, the inventors have further focused on the direction of the oil flow during high-speed rotation and considered various dynamic oil behaviors. For example, it is effective to disperse the oil flow, When flowing into the discharge groove from the pump chamber, a flow in the direction returning to the pump chamber is also generated, and it is preferable to make the shape of the discharge groove in consideration of such a flow in the return direction. completed.

  The present invention has been made in view of such a point, and an object of the present invention is to more reliably prevent erosion by adding a device to the shape of the discharge groove.

In order to solve the above problems, the present invention provides:
A casing having an oil suction groove and an oil discharge groove;
An inner gear-shaped outer rotor rotatably accommodated in the casing;
An inner rotor that forms an external gear that meshes with the outer rotor from the inside, is housed rotatably inside the outer rotor about an axis that is eccentric from the outer rotor, and forms a pump chamber with the outer rotor An oil pump comprising:
The oil suction groove and the oil discharge groove are formed on the bottom surface of the casing where the side surfaces of the outer rotor and the inner rotor are in sliding contact,
At the end of the oil discharge groove on the side opposite to the rotation direction of the outer rotor and the inner rotor,
A shallow bottom portion having a flat surface that is shallower than the rotational direction side portion of the oil discharge groove and substantially parallel to the bottom surface of the casing;
A V-shaped valley located on the outer peripheral side of the shallow bottom and having a substantially V-shaped cross-section when cut by a radial surface, and becomes deeper from the opposite direction side toward the rotational direction side and the width increases. And
Is formed.

  The apex on the opposite side in the V-shaped valley is preferably provided in the vicinity of the tip circle of the inner rotor.

  Furthermore, an outer peripheral side shallow bottom portion having the same depth as the shallow bottom portion may be formed on the outer peripheral side of the V-shaped valley portion.

  Moreover, you may make it the inclined surface which becomes deep toward the said rotation direction side from the said shallow bottom part and the said V-shaped valley part in the said opposite direction side edge part of the said oil discharge groove | channel.

Further, on the rotational direction side in the oil discharge groove,
The cross-sectional shape when cut by the radial surface of the outer rotor is substantially V-shaped,
You may make it form the rotation direction side V-shaped valley part which becomes deep toward the said opposite direction side from the said rotation direction side, and a width | variety spreads.

  As mentioned above, the oil flow direction in the oil discharge groove is dispersed by providing the shallow bottom portion and the V-shaped valley portion on the outer peripheral side at the end portion in the opposite direction of the oil discharge groove. This makes it difficult for a severe collision or turbulence to occur on the outer peripheral wall surface of the oil discharge groove. Further, the oil near the end portion on the opposite side of the oil discharge groove tends to flow back to the pump chamber through the shallow bottom portion. As a result, cavitation is less likely to occur, and erosion can be more reliably prevented.

  According to the present invention, erosion can be more reliably prevented by providing the shallow bottom portion and the V-shaped valley portion located on the outer peripheral side at the end of the oil discharge groove.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Configuration of essential parts of oil pump)
As shown in FIG. 1, the oil pump according to the embodiment of the present invention includes a pump casing 21, a trochoidal inner rotor 31 and an outer rotor 32, and a drive shaft 23 fitted to the inner rotor 31. is doing.

  An oil suction groove 28 and an oil discharge groove 29 are formed in the pump casing 21 on the bottom surface where the side surfaces of the rotors 31 and 32 are in sliding contact with each other. The oil suction groove 28 and the oil discharge groove 29 are communicated with a suction side connection port and a discharge side connection port provided at the peripheral edge of the pump casing 21 through an oil passage (not shown). The shape of the oil discharge groove 29 will be described in detail later.

  A circular rotor working chamber 30 is provided at the center of the pump casing 21, and the inner rotor 31 and the outer rotor 32 that are meshed with each other are inserted into the rotor working chamber 30.

  The inner rotor 31 and the central axis X1 of the drive shaft 23 and the outer rotor 32 and the central axis X2 of the rotor working chamber 30 are eccentric from each other, and the inner rotor 31 rotates around the central axis X1 (in FIG. With rotation in the clockwise direction), the outer rotor 32 rotates about the central axis X2 in the same direction.

  On the outer peripheral surface of the inner rotor 31 and the inner peripheral surface of the outer rotor 32, teeth that can mesh with each other (trochoidal teeth in the illustrated example) are formed, and in the meshed state, the rotors 31, 32 are in the rotor working chamber. 30 is rotatably accommodated. Between the contact points (seal points) of the rotors 31 and 32, pump chambers V1, V2,... Sandwiched between the pump casing 21 and a pump cover (not shown) are formed. In this embodiment, when the downstream seal point of a certain pump chamber (for example, pump chamber V2 shown in FIG. 1) reaches the vicinity of the partition end position of the oil discharge groove 29, the upstream side of the pump chamber V2 is located upstream. The position of each part is set so that the upstream seal point of the pump chamber V1 reaches the partition end position of the oil suction groove 28.

  In this oil pump, when the drive shaft 23 rotates counterclockwise about the central axis X1 and the rotational force is transmitted to the inner rotor 31, the inner rotor 31 also rotates counterclockwise about the central axis X1. The outer rotor 32 that meshes with the inner rotor 31 rotates in the same direction at a slightly lower speed around the central axis X2. By these rotations, oil is supplied from the suction side connection port to the pump chamber through the oil passage and the oil suction groove 28, and from the time when the pump chamber is communicated to the oil discharge groove 29, the oil is supplied to the outside through the oil discharge groove 29. Oil is discharged (see, for example, pump chamber V2 shown in FIG. 1).

(Shape of oil discharge groove 29)
The oil discharge groove 29 formed in the pump casing 21 has a shallow bottom portion 29a and V at the end (upstream side) opposite to the rotation direction of the rotors 31 and 32, as shown in FIGS. A character valley portion 29b and a vertical wall 29c are formed. The shallow bottom portion 29 a is formed on a flat surface that is shallower than the rotation direction side (downstream side) portion of the rotors 31 and 32 in the oil discharge groove 29 and substantially parallel to the bottom surface of the pump casing 21. Further, the V-shaped valley portion 29b is located on the outer peripheral side of the shallow bottom portion 29a and has a substantially V-shaped cross section when cut along a radial surface, and becomes deeper from the upstream side toward the downstream side. It is formed in a shape that widens. The upstream apex of the V-shaped valley portion 29b is not particularly limited, but for example, providing it near the tip circle of the inner rotor 31 makes it easier to reduce abrupt changes in oil pressure. preferable.

(Oil behavior)
Next, the behavior of oil in the oil pump will be described in comparison with a comparative example. This comparative example is an example in which the V-shaped valley portion 29b as described above is not formed, that is, an example in which the shallow bottom portion 29a is formed from the inner peripheral side to the outer peripheral side at the end of the oil discharge groove 29. It is.

  6 to 8 show the flow direction and speed of the discharge groove oil 39 and the shallow bottom oil 39a filled in the oil discharge groove 29 in the case of the comparative example. 9 to 11 show the discharge groove oil 39, the shallow bottom oil 39a, and the V-shaped valley portion filled in the oil discharge groove 29 in the oil pump of the present embodiment in which the V-shaped valley portion 29b is formed. The flow direction and speed of the oil 39b are shown. Here, FIG. 6 and FIG. 9 are perspective views of the oil seen from obliquely upward near the downstream side, and FIG. 7 and FIG. 10 are cross-sectional views and views of the oil corresponding to the arrows BB shown in FIG. 8 and 11 are perspective views of the oil as viewed from an obliquely lower side near the upstream side. In these drawings, the shape of the details is shown in a simplified manner for convenience of modeling in the simulation.

  When the V-shaped valley portion 29 b is not formed, a high-speed flow is uniformly generated, and this high-speed oil collides with a wall surface or the like on the outer peripheral side of the oil discharge groove 29. In addition, this collision causes backflowing oil, and a turbulent state occurs when this backflowing oil collides with a forward flow near the start position of the discharge groove. Further, in the vicinity of the vertical wall 29c at the upstream end of the oil discharge groove 29, a vortex is generated by the stagnant oil, and there is a strong tendency for a turbulent state. For this reason, cavitation is likely to occur, and therefore erosion is likely to occur.

  On the other hand, when the V-shaped valley portion 29b is formed, the oil flowing into the oil discharge groove 29 moves along the bottom of the V-shaped valley portion 29b toward the center in the width direction of the oil discharge groove 29. Convergence and slightly downward flow occurs. And by this flow, in the vicinity of the upstream end portion of the oil discharge groove 29, the direction of the entire flow is easily dispersed, and severe collisions and turbulences to the wall surface on the outer peripheral side of the oil discharge groove 29 are unlikely to occur. It is thought that cavitation is less likely to occur. Further, the oil in the vicinity of the vertical wall 29c at the upstream end of the oil discharge groove 29 tends to flow back to the pump chamber via the shallow bottom portion 29a. If the amount of fine bubbles in the oil in the oil discharge groove 29 is reduced by this returning flow, cavitation is less likely to occur in the oil discharge groove 29. Therefore, erosion is more reliably prevented by these.

(Modification)
As described above, in order to prevent erosion, it is effective to provide the shallow bottom portion 29 a and the V-shaped valley portion 29 b on the outer peripheral side at the upstream end portion of the oil discharge groove 29. The detailed shape and dimensions for obtaining the same effect are not limited to those described above and illustrated. Specifically, for example, as shown in FIG. 12, a shallow bottom portion 29d having a flat portion extending toward the downstream side is provided on the further outer peripheral side of the V-shaped valley portion 29b, or as shown in FIG. Alternatively, a shallow bottom portion 29e having the same shape as the shallow bottom portion 29a may be provided. Further, for example, the vertical wall 29c is not formed on the downstream side of the V-shaped valley portion 29b, but a slope 29f that gradually becomes deeper toward the downstream side is formed as shown in FIG. May be.

  Further, the downstream end portion of the oil discharge groove 29 also has a substantially V-shaped cross section when cut along the radial surface of the outer rotor 32, similarly to the V-shaped valley portion 29b. Alternatively, a V-shaped valley portion having a shape that becomes deeper toward the upstream side and expands in width may be provided.

  The oil pump according to the present invention is useful as an oil pump or the like provided in an automatic transmission of a vehicle.

It is sectional drawing which shows the structure of the principal part of the oil pump which concerns on embodiment of this invention. It is the elements on larger scale which show the structure of the principal part of the pump casing 21 of the said oil pump. It is a perspective view which shows the structure of the upstream edge part of the oil discharge groove | channel 29 formed in the pump casing 21 of the said oil pump. It is IV-IV sectional drawing of FIG. It is VV sectional drawing of FIG. It is the perspective view seen from diagonally upward which shows the flow of the oil of a comparative example. It is sectional drawing which shows the flow of the oil of the said comparative example. It is the perspective view seen from diagonally downward which shows the flow of the oil of the said comparative example. It is the perspective view seen from diagonally upward which shows the flow of the oil of the said embodiment. It is sectional drawing which shows the flow of the oil of the said embodiment. It is the perspective view seen from diagonally downward which shows the flow of the oil of the said embodiment. It is a perspective view which shows the structure of the upstream edge part of the oil discharge groove | channel 29 of a modification. It is a perspective view which shows the structure of the upstream edge part of the oil discharge groove | channel 29 of another modification. It is sectional drawing which shows the structure of the upstream edge part of the oil discharge groove | channel 29 of another modification.

Explanation of symbols

21 Pump casing
23 Drive shaft
28 Oil suction groove
29 Oil discharge groove
29a shallow bottom
29b V-shaped valley
29c vertical wall
29d shallow bottom
29e Shallow bottom
29f slope
30 Rotor working chamber
31 Inner rotor
32 Outer rotor
39 Discharge groove oil
39a Shallow bottom oil
39b V-shaped valley oil
V1, V2 pump room
X1, X2 Center axis X

Claims (5)

A casing having an oil suction groove and an oil discharge groove;
An inner gear-shaped outer rotor rotatably accommodated in the casing;
An inner rotor that forms an external gear that meshes with the outer rotor from the inside, is housed rotatably inside the outer rotor about an axis that is eccentric from the outer rotor, and forms a pump chamber with the outer rotor An oil pump comprising:
The oil suction groove and the oil discharge groove are formed on the bottom surface of the casing where the side surfaces of the outer rotor and the inner rotor are in sliding contact,
At the end of the oil discharge groove on the side opposite to the rotation direction of the outer rotor and the inner rotor,
A shallow bottom portion having a flat surface that is shallower than the rotational direction side portion of the oil discharge groove and substantially parallel to the bottom surface of the casing;
A V-shaped valley located on the outer peripheral side of the shallow bottom and having a substantially V-shaped cross-section when cut by a radial surface, and becomes deeper from the opposite direction side toward the rotational direction side and the width increases. And
An oil pump characterized by being formed. The oil pump according to claim 1,
The oil pump, wherein a vertex of the opposite direction side in the V-shaped valley portion is provided in the vicinity of a tip circle of the inner rotor. The oil pump according to claim 1,
Furthermore, the outer peripheral side shallow bottom part of the same depth as the said shallow bottom part is formed in the outer peripheral side rather than the said V-shaped valley part, The oil pump characterized by the above-mentioned. The oil pump according to claim 1,
An oil pump, wherein an inclined surface that is deeper from the shallow bottom portion and the V-shaped valley portion toward the rotation direction side is formed at the opposite end portion of the oil discharge groove. The oil pump according to any one of claims 1 to 4,
Furthermore, on the rotation direction side in the oil discharge groove,
The cross-sectional shape when cut by the radial surface of the outer rotor is substantially V-shaped,
An oil pump characterized in that a rotation direction side V-shaped valley portion is formed which becomes deeper from the rotation direction side toward the opposite direction side and widens.

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