JP5721521B2 - Internal gear type oil pump - Google Patents

Description

  The present invention relates to an internal gear type oil pump.

  Generally, automatic transmissions, continuously variable transmissions, etc. are provided with oil pumps for supplying hydraulic oil to hydraulic control devices, and among them, internal gear type oil pumps that can be made compact are widely used. . The internal gear type oil pump includes a pump housing (pump body and pump cover) having a cylindrical gear housing space, an outer gear having internal teeth rotatably disposed in the gear housing space, And an inner gear having external teeth meshing with the teeth, and a suction port and a discharge port are formed in the pump housing. As the inner gear rotates, the volume of the pump chamber formed between the outer teeth of the inner gear and the inner teeth of the outer gear changes, so that oil is sucked from the suction port and discharged from the discharge port. It has become.

  FIG. 7 is a front view of a conventional pump housing (pump gear omitted). In the pump body 100 constituting the pump housing, a concave gear storage space 101 is formed, and a substantially arc-shaped suction port 102 and discharge port 103 are formed on the bottom surface of the gear storage space 101. The suction port 102 and the discharge port 103 are formed so as to be substantially opposed to a pump chamber formed between the outer teeth of the inner gear, which is a pump gear, and the inner teeth of the outer gear. When the inner gear rotates, the outer gear also rotates, sucks oil from the suction port 102, compresses the oil in the rotation direction of the gear, and discharges oil from the discharge port 103.

  When the inner gear is driven, the outer peripheral surface of the outer gear comes into sliding contact with the inner peripheral surface of the pump body 100 (the inner peripheral surface of the gear storage space 101). A predetermined clearance is set between the side surface of the pump gear and the side surface of the pump body 100 (the bottom surface of the gear housing space 101), and oil leaking from the clearance prevents seizure between the outer gear and the pump body. . However, under certain conditions, seizure due to oil film breakage may occur at the contact portion S between the outer peripheral surface of the outer gear and the inner peripheral surface of the pump body 100 on the intermediate portion between the suction port 102 and the discharge port 103 or on the discharge port 103 side. There was a problem that it was likely to occur. In particular, seizure is likely to occur when the pump gear is reduced in diameter. The reason for this is that when the pump gear is reduced in diameter, the discharge amount is reduced, so that the gear width needs to be increased accordingly, and as a result, the oil does not sufficiently spread to the inner peripheral surface of the gear housing space 101. it is conceivable that.

  In Patent Document 1, an axial groove is formed in the inner peripheral surface of the housing so as to extend over the entire area in the axial direction with respect to the outer peripheral surface of the outer gear, and the inner peripheral surface of the housing immediately before finishing the expansion process is formed on the inner peripheral surface of the housing. A trochoidal oil pump having a circumferential groove formed so as to communicate with the axial groove is disclosed.

  In this case, it is possible to supply oil to a portion where seizure is most likely to occur, but since it is necessary to form an axial groove and a circumferential groove on the inner peripheral surface of the housing, complicated processing is required. I need. In addition, since the circularity of the cylindrical space is reduced by these grooves, the surface pressure of the inner peripheral surface of the housing that is in contact with the outer peripheral surface of the outer gear partially increases, which may cause uneven wear.

Japanese Patent No. 3810444

  An object of the present invention is to provide an internal gear type oil pump that can prevent seizure only by performing simple processing on a housing and can suppress an increase in surface pressure of an inner peripheral surface of the housing that is in contact with the outer peripheral surface of the outer gear. .

To achieve the above object, the present invention provides a pump housing having a cylindrical gear housing space, an outer gear having internal teeth rotatably accommodated in the gear housing space, and an inner tooth of the outer gear. An inner gear having meshing external teeth; a suction port and a discharge port opening on a side surface of the pump housing opposite to the side surfaces of the outer gear and the inner gear; In the internal gear type oil pump that sucks in and discharges oil from the discharge port, the inner peripheral end communicates with the suction port on the side surface of the pump housing facing the side surface of the outer gear, and the outer peripheral end is the outer gear An oil groove extending to or near the axial extension line of the inner peripheral surface of the pump housing that is in sliding contact with the outer peripheral surface of the pump housing Form, the inner peripheral end of the oil groove, characterized in that it communicates with the portion merges with the suction passage of the suction port, to provide internal gear oil pump.

  The oil sucked from the suction port flows into the oil groove and is supplied to the gap between the side surface of the outer gear and the side surface of the pump housing. Since the outer peripheral end of the oil groove extends to or near the extension line of the inner peripheral surface of the pump housing that is in sliding contact with the outer peripheral surface of the outer gear, a part of the oil entering the oil groove is in contact with the outer peripheral surface of the outer gear. It is also supplied to the gap with the inner peripheral surface of the pump housing. Since the oil supplied to the gap between the outer peripheral surface of the outer gear and the inner peripheral surface of the pump housing spreads almost all around as the outer gear rotates, seizure due to oil film breakage can be prevented. In the present invention, since it is not necessary to process the inner peripheral surface of the pump housing, the roundness of the gear housing space does not decrease, and the surface pressure of the inner peripheral surface of the housing in contact with the outer peripheral surface of the outer gear is partially reduced. Uneven wear can be suppressed without increasing.

  The inner peripheral end of the oil groove may communicate with any part of the suction port, but preferably communicates with a portion where the suction port merges with the suction passage. As the volume of the pump chamber formed between the inner teeth of the outer gear and the outer teeth of the inner gear changes, a negative pressure portion and a positive pressure portion are generated in the suction port. In particular, the suction port region joining the suction passage for supplying oil to the suction port often becomes a negative pressure portion. Although it is possible to connect the oil groove to the positive pressure part of the suction port, the oil compressed in the pump chamber is likely to leak into the gap between the pump gear and the pump housing via the oil groove, resulting in a decrease in the discharge amount. there is a possibility. On the other hand, when the inner peripheral end of the oil groove is connected to a portion that merges with the suction passage of the suction port, this portion is likely to be in a negative pressure state, so the oil pump is compared with the case where it is connected to the positive pressure portion. It is possible to suppress a decrease in the discharge amount per time.

  A groove for preventing cavitation called a notch is often formed on the upstream side in the rotation direction of the discharge port. This notch is generally formed by contouring. When processing the oil groove of the present invention so as to extend to the outer peripheral side of the suction port, it is possible to process the oil groove of the present invention using a tool used for notching contouring. Therefore, a new tool is not required and an increase in processing cost can be suppressed.

  As described above, according to the present invention, the inner peripheral end communicates with the suction port on the side surface of the pump housing facing the side surface of the outer gear, and the outer peripheral end is on the axial extension line of the inner peripheral surface of the pump housing or the Since the oil groove extending to the vicinity is formed, the oil sucked from the suction port can be supplied to the gap between the outer peripheral surface of the outer gear and the inner peripheral surface of the pump housing, and seizure due to oil film breakage can be prevented. Moreover, since the oil groove is formed on the side surface of the pump housing and does not affect the roundness of the inner peripheral surface of the pump housing, uneven wear can be prevented.

It is the front view which looked at the pump body side of the internal gear type oil pump concerning the present invention. It is the sectional view on the AA line of FIG. It is the BB sectional view taken on the line of FIG. It is an enlarged view of the C section of FIG. It is a front view of the state which accommodated the pump gear in the pump body. It is a front view of the state which removed the pump gear from the pump body. It is a front view of the conventional pump body (a pump gear is abbreviate | omitted).

  1 to 3 show a trochoid oil pump which is an example of an internal gear oil pump according to the present invention. The oil pump 1 includes a pump body 2 and a pump cover 3 that constitute a pump housing, and a cylindrical gear housing space 4 is formed therebetween. The gear housing space 4 of this embodiment is composed of a cylindrical recess 21 formed in the pump body 2 and an inner side surface 31 of the pump cover 3 that closes the recess. In this specification, the pump body 2 refers to a housing member in which a recess 21 for a gear storage space is formed, and the pump cover 3 refers to a housing member that closes the recess 21.

  As shown in FIG. 5, the gear housing space 4 houses an inner gear 5 and an outer gear 6 that are pump gears. The inner gear 5 has external teeth 51, and the inner periphery of the inner gear 5 is connected to the drive shaft 8 and is driven in the direction of the arrow in FIG. The outer gear 6 has inner teeth 61 that mesh with the outer teeth 51 of the inner gear 5, and the outer peripheral surface of the outer gear 6 is rotatably supported by the inner peripheral surface of the recess 21 (inner peripheral surface of the pump body 2). ing. The number of teeth of the inner tooth 61 is one more than that of the outer tooth 51, and the rotation center O <b> 1 of the outer gear 6 is eccentric upward with respect to the rotation center O <b> 2 of the inner gear 5.

  As shown in FIG. 6, an arcuate suction port 22 and a discharge port 23 are opened on the side surface (the bottom surface of the recess 21) of the pump body 2 facing the side surfaces of the inner gear 5 and the outer gear 6. The suction port 22 and the discharge port 23 are substantially opposed to the pump chamber 7 formed between the outer teeth 51 of the inner gear 5 and the inner teeth 61 of the outer gear 6. In this example, the suction port 22 and the discharge port 23 are formed in the pump body 2, but either or both of the ports can be formed in the pump cover 3. As shown in FIGS. 1 and 2, the suction port 22 is connected to a strainer (not shown) through a suction passage 24 formed in the pump body 2. The discharge port 23 is connected to a hydraulic control device (not shown) via a discharge passage 25 formed in the pump body 2.

  The suction passage 24 merges with the lower portion of the suction port 22, and negative pressure is likely to be generated in the merge portion 22a. As shown in FIG. 3, the suction port 22 is formed to be gradually shallower in accordance with the rotation direction of the pump gears 5 and 6. On the other hand, the discharge port 23 is formed to be gradually deeper in accordance with the rotation direction of the pump gear, and the discharge passage 25 is connected to the deepest lower portion 23a. A cavitation countermeasure groove 26 (see FIG. 6) called a notch is formed at the upstream end of the discharge port 23 in the rotation direction of the pump gear, that is, at the shallowest portion of the discharge port 23.

  As shown in FIGS. 4 and 6, the inner peripheral end communicates with the suction port 22 and the outer peripheral end is the inner side of the concave portion 21, as shown in FIGS. 4 and 6. An oil groove 27 is formed that extends to the axial extension line of the peripheral surface (inner peripheral surface of the pump body 2) or to the vicinity thereof. The position of the outer peripheral end of the oil groove 27 may be on the same line as the extension line of the inner peripheral surface of the recess 21 or may be slightly shifted to the inner diameter side. Any position may be used as long as the oil that has entered the oil groove 27 can be supplied to the gap δ between the outer peripheral surface of the outer gear 6 and the inner peripheral surface of the recess 21. The oil groove 27 of this embodiment is formed so as to extend in the outer peripheral direction from the lowermost portion, which is the joining portion 22a with the suction passage 24 of the suction port 22, and the outer peripheral end is along the arc of the inner peripheral surface of the recess 21. It extends. The oil groove 27 is a contouring groove shallower than the depth of the suction port 22 and can be machined with the same tool as that used in the contouring process of the notch 26.

  Here, the operation of the oil pump 1 according to the present invention will be described. When the inner gear 5 is driven in the direction of the arrow in FIG. 5, the volume of the pump chamber 7 formed between the outer gear 6 and the inner gear 5 changes, and oil is sucked from the suction port 22 and oil is sucked from the discharge port 23. It can be discharged. The outer peripheral surface of the outer gear 6 is always in sliding contact with the inner peripheral surface of the recess 21 (the inner peripheral surface of the pump body 2). However, the outer gear 6 is pushed outward in the radial direction by the pressure change of the oil trapped in the pump chamber 7. In addition, there is a problem that seizure occurs due to the oil film cutting between the outer peripheral surface of the outer gear 6 and the inner peripheral surface of the recess 21. As shown by a region S in FIG. 7, the portion where the burn-in is most likely to occur is often an intermediate region between the suction port 102 and the discharge port 103 or a position shifted to the discharge port 103 side.

  In the present invention, the inner peripheral end communicates with the suction port 22 on the side surface of the pump body 2 (the bottom surface of the recess 21) facing the side surface of the outer gear 6, and the outer peripheral end extends in the axial direction of the inner peripheral surface of the pump body 2. Since the oil groove 27 extending to or near the line is formed, the oil sucked into the suction port 22 from the suction passage 24 and the outer peripheral surface of the outer gear 6 and the inner peripheral surface of the pump body 2 are indicated by arrows in FIG. It can be supplied to the gap δ with respect to the inner peripheral surface of the recess 21. Since the oil supplied to the gap δ spreads over almost the entire circumference of the inner peripheral surface of the recess 21 as the outer gear 6 rotates, seizure due to oil film breakage can be prevented.

  Furthermore, in the present invention, the oil groove 27 is formed only on the bottom surface of the recess 21 (side surface of the pump body 2), and no groove is formed on the inner peripheral surface, so that the roundness of the inner peripheral surface of the recess 21 is lost. There is nothing. Therefore, the surface pressure of the inner peripheral surface of the recess 21 that contacts the outer peripheral surface of the outer gear 6 does not increase locally, and uneven wear of the inner peripheral surface can be prevented.

  In the above-described embodiment, the oil groove 27 communicates with the joining portion 22a of the suction port 22 with the suction passage 24. However, the oil groove 27 may communicate with a position other than the joining portion 22a of the suction port 22. For example, it may communicate with the upper region of the suction port 22 that is a positive pressure part, or may communicate with the negative pressure part and the positive pressure part. When the oil groove 27 communicates with the positive pressure portion of the suction port 22 (when communicated with the upper region of the suction port), the oil groove 27 can be provided near the place where the seizure is most likely to occur. , Oil can be effectively supplied to that part.

  If the oil groove 27 is formed in the upper region (positive pressure portion) of the suction port 22, the oil pushed out from the pump chamber 7 between the outer gear 6 and the inner gear 5 leaks from the oil groove 27. There is a possibility that the discharge amount may be reduced. On the other hand, when the oil groove 27 is formed in the joining portion 22a with the suction passage 24 of the suction port 22 as in the embodiment, the joining portion 22a is likely to be negative pressure and is pushed out from the pump chamber 7. Therefore, the oil does not leak through the oil groove 27, and a decrease in the discharge amount per one rotation can be suppressed. Therefore, there exists an advantage which can suppress the efficiency fall of an oil pump.

  The shape of the oil groove 27 is not limited to one concave portion formed in a planar shape over a predetermined region of the suction port 22 as shown in FIG. 6, and the shape thereof is arbitrary. For example, a plurality of notch grooves extending in the outer peripheral direction from the suction port 22 may be used, or the inner peripheral end communicating with the suction port 22 may be a narrow groove and the outer peripheral end may be a wide groove.

  In the above embodiment, the trochoidal oil pump is shown as an example of the internal gear type oil pump. However, it is not limited to the trochoid type, and any type of internal gear type oil pump may be used.

  In the above embodiment, the suction port is formed on the pump body side, but it may be formed on the pump cover side. In this case, an oil groove may be formed not on the bottom surface of the recess 21 but on the inner surface of the pump cover facing the side surface of the outer gear.

1 Oil pump 2 Pump body (pump housing)
21 recess (gear storage space)
22 Suction port 23 Discharge port 24 Suction passage 25 Discharge passage 27 Oil groove 3 Pump cover (pump housing)
31 inner surface 4 gear storage space 5 inner gear 51 outer tooth 6 outer gear 61 inner tooth 7 pump chamber 8 drive shaft

Claims (1)

A pump housing having a cylindrical gear storage space, an outer gear having internal teeth rotatably accommodated in the gear storage space, an inner gear having external teeth meshing with the internal teeth of the outer gear, and the outer gear A suction port and a discharge port that are opened on the side surface of the pump housing opposite to the side surfaces of the gear and the inner gear, and driving the inner gear sucks oil from the suction port and discharges oil from the discharge port; In the contact gear type oil pump,
On the side surface of the pump housing opposite to the side surface of the outer gear, the inner peripheral end communicates with the suction port and the outer peripheral end slides on the outer peripheral surface of the outer gear on the axial extension line of the inner peripheral surface of the pump housing or An internal gear type oil pump characterized in that an oil groove extending to the vicinity thereof is formed, and an inner peripheral end of the oil groove communicates with a portion that merges with a suction passage of the suction port .

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