JP2010019205A - Rotor for internal gear pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize pulsation performances of a rotor for an internal gear pump manufactured by powder metallurgy process without correction of inclination of tooth surfaces of an inner rotor and an outer rotor. <P>SOLUTION: In the inner rotor 2 and the outer rotor 3 manufactured through at least sizing process, the inner rotor 2 and the outer rotor 3 are combined so that A surface of the inner rotor and A surface of the outer rotor are put at the same side when an end surface crossing the tooth surfaces 6, 7 of each rotor at acute angles is defined as A surface and an end surface crossing the same at obtuse angles is defined as B surface. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal gear pump rotor that employs a sintered inner rotor and outer rotor.

Internal gear pumps are widely used as oil pumps for car engines and automatic transmissions (AT). This internal gear pump is described, for example, in Patent Document 1 below.
The pump rotor employed in this internal gear pump is mainly composed of an inner rotor and an outer rotor having a number of teeth one more than that of the inner rotor in an eccentric arrangement. Further, the inner rotor and outer rotor constituting the pump rotor are mostly made of sintered alloy. Sintered alloy inner rotors and outer rotors are manufactured by powder metallurgy, and are provided to the market after sizing after powder compacting and compacting.

  Sizing for correcting the size and shape is performed using a die that combines a die, upper and lower punches, and a core. For the inner rotor, a method is used in which the tooth surface of the outer tooth is squeezed by the die forming hole, and for the outer rotor, the tooth surface of the inner tooth is squeezed by the outer peripheral surface of the core. However, the squareness of the tooth surface may decrease due to the sizing. The squareness of the tooth surface referred to here is based on the end face, and an ideal angle of 90 ° with the end face is assumed.

  In sizing, due to the influence of the side resistance generated between the die and the core, the other end side pressed by the lower punch rather than the one end side of the sintered body (rotated rotor) pressed by the upper punch. Molding pressure tends to be low. When the difference in the sizing molding pressure occurs, a difference also occurs in the elastic restoration amount of the tooth surface after sizing on one end side and the other end side of the rotor, and this has a particularly great influence on the reduction in squareness. it is conceivable that.

In addition, in the following Patent Document 2, the first engagement portion (tooth surface) is not perpendicular to the end surface because the first engagement portion and the end surface are formed by separate members (different mold elements). Considering that there is a cause, as a countermeasure against the problem, it is proposed that both the first engaging portion and the end surface (a part of the outer periphery of the surface) are formed by a die.
Japanese Patent Laid-Open No. 7-324683 JP 2004-27317 A

  In the gear pump rotor manufactured by the powder metallurgy method, the squareness of the tooth surfaces of the inner rotor and the outer rotor may be lowered by passing through the sizing process as described above.

  The reduction in the perpendicularity can be corrected by polishing the tooth surface after sizing, but if the correction step is included, the advantages of the powder metallurgy method (excellent mass productivity and cost reduction) are reduced. In addition, since the rotor for an internal gear pump makes the whole end surface flat without a step, the method of Patent Document 2 in which a part of the end surface is formed with a die together with the first engaging portion cannot be adopted. In addition, since the difference in molding pressure due to the influence of the side resistance described above also occurs when part of the end face is molded with a die, the method of Patent Document 2 is a squareness due to side resistance during powder molding or sizing. It is not effective in preventing the decrease in the number.

  For this reason, the pump rotor after sizing is used without correcting the tooth surface, but if the inner rotor and outer rotor whose tooth surfaces are inclined with respect to the ideal surface are combined, depending on the combination situation The tip clearance (gap between the teeth of the inner rotor and outer rotor at the confined part of the pump chamber) varies, and the liquid leakage from the tip clearance varies from product to product. Will cause a difference.

  This invention makes it the subject to stabilize the pulsation performance of the rotor for internal gear pumps manufactured by a powder metallurgy method, without correcting the inclination of the tooth surface of an inner rotor and an outer rotor.

  In order to solve the above-described problems, in the present invention, in an internal gear pump rotor that combines an inner rotor and an outer rotor that are manufactured through at least a sizing process, each of the inner and outer rotors is The end surface on the side that intersects the acute angle with respect to the tooth surface is the A surface, and the end surface on the side that intersects the obtuse angle is the B surface, so that the A surface of the inner rotor and the A surface of the outer rotor are placed on the same side. Combined with the rotor. Both inner and outer rotors are considered to have parallel end faces.

  In this rotor for pump, the inclination angle at the tooth tip portion of the tooth surface of the inner rotor is θi, and the rotor radial displacement based on the measurement start point per 10 mm of rotor thickness of the tooth surface at the inclination angle θi (rotor thickness 10 mm) The rotor radial displacement (rotor) based on the measurement start point per 10 mm of rotor thickness of the tooth surface at the inclination angle θo, and the inclination angle at the tooth tip portion of the tooth surface of the outer rotor as S1 It is preferable to satisfy the condition of 10 ≦ S1 + S2 ≦ 30 μm, where S2 is a squareness per 10 mm thickness. The inclination angle of the tooth surface referred to here is an angle based on a surface perpendicular to the end surface.

  In the pump rotor according to the present invention, since the A surface of the inner rotor and the A surface of the outer rotor are placed on the same side, there is no variation in the tip clearance due to the mismatch of the inclination directions of the tooth surfaces of the two rotors. As a result, the amount of liquid leakage from the tip clearance portion does not vary greatly depending on the product, and the pulsation value of the pump of the same specification is stabilized.

  Embodiments of a pump rotor according to the present invention will be described below with reference to FIGS. A pump rotor 1 shown in FIG. 1 is configured by combining an inner rotor 2 and an outer rotor 3 each formed of a sintered alloy. The inner rotor 2 has a shaft hole 4 at the center. 2a is a tooth of the inner rotor 2, and 3a is a tooth of the outer rotor 3.

  The inner rotor 2 has a tooth profile formed with a trochoidal curve, a tooth shape formed with a cycloid curve, a tooth bottom portion with an inversion cycloid curve, and a meshing portion with an outer rotor with an involute curve. It is known that the portion is formed by an abduction cycloid (epicycloid) curve or any other arbitrary curve, and such a tooth profile can be arbitrarily selected and employed.

  As the outer rotor 3, one having one more tooth than the inner rotor 2 is used. The outer rotor 3 is known to have a tooth profile formed with a trochoid curve, a tooth shape formed with a cycloid curve, or one created by the method described in Japanese Patent Application Laid-Open No. 2005-36735. Any tooth profile can be selected and adopted.

  The inner rotor 2 and the outer rotor 3 are combined in an eccentric arrangement to constitute a pump rotor 1, and the pump rotor 1 is housed in a pump case (not shown) having a suction port and a discharge port to be inscribed. Configure the gear pump. The internal gear pump engages the shaft hole 4 of the inner rotor 2 through a drive shaft (also not shown), and transmits the driving force from the drive shaft to rotate the inner rotor 2. At this time, the outer rotor 3 is driven to rotate, and the volume of the pump chamber (pumping chamber) 5 formed between the two rotors is increased or decreased by this rotation, and a liquid such as oil is sucked and discharged.

  As shown in FIG. 2, the illustrated pump rotor 1 has an angle θi and a state in which the tooth surfaces 6 and 7 of the inner rotor 2 and the outer rotor 3 intersect at an acute angle with respect to one end surface of each rotor. It is tilted by θo. For each of the inner rotor 2 and the outer rotor 3, when one end face is considered to be an A face and the other end face is considered to be a B face, the tooth faces 6 and 7 of both rotors are at an acute angle with respect to the A face, Is inclined in an obtuse angle direction. The pump rotor of FIG. 1 is configured by combining the inner rotor 2 and the outer rotor 3 having such tooth surfaces so that the A surface of the inner rotor 2 and the A surface of the outer rotor 3 are placed on the same side. Yes. 3 is a tip clearance formed between the tooth tips of the inner rotor 2 and the outer rotor 3.

  In the inner rotor 2 and the outer rotor 3, the sum of the inclination angles θi and θo at the tooth tip portions of the tooth surfaces 6 and 7 of the respective rotors is the rotor radial displacement S1 per 10 mm of the rotor thickness of the tooth surface shown in FIG. What is represented by the sum of S2 and within a range of 10 to 30 μm is combined. For this reason, the fluctuation width of the tip clearance t formed between the tooth surfaces 6 and 7 of the meshing portion is, for example, 10 mm thick. In the rotor, it is suppressed to 25 μm or less, and the variation width of the liquid leakage amount from the chip clearance portion is reduced. The amount of liquid leakage from the tip clearance portion decreases as the sum of the displacements S1 and S2 in the meshing portion decreases. However, since the squareness of the tooth surface obtained by sizing is limited, the inner rotor and the outer As for the combination of the squareness of the tooth surfaces of the rotor, it is preferable to satisfy the previously described condition of 10 ≦ S1 + S2 ≦ 30 μm.

  FIG. 5 shows a state in which the A surface of the inner rotor 2 and the B surface of the outer rotor 3 are combined on the same side. In the conventional internal gear pump, the combination state of FIG. 2 and the combination state of FIG. 5 are mixed, and the amount of liquid leakage from the tip clearance portion (that is, the pump discharge amount) varies, which makes the pulsation value unstable. However, if the pump rotor of the present invention is used, the combination direction of the inner rotor 2 and the outer rotor 3 is unified, and the combination of FIG. 5 is eliminated. The fluctuation range of the leakage amount is reduced, and the pump performance is stabilized.

-Example-
The pump rotor of the present invention was prototyped and an evaluation test related to discharge performance was performed. An inner rotor with 10 teeth each formed of a sintered alloy and an outer rotor with 11 teeth were manufactured by powder metallurgy, and both were combined to produce a rotor for an oil pump with a rotor thickness of 10 mm. . The inner rotor is formed by a combination of an involute curve and an abduction cycloid curve at the tooth tip part, and the tooth bottom part is formed by an inversion cycloid curve. The outer rotor has a diameter around the center of the outer rotor 2 at the center of the inner rotor 2. (2e + t) (where e is the amount of eccentricity between the center Oi of the inner rotor 2 and the center Oo of the outer rotor 3 shown in FIG. 1, and t is the tip clearance of FIG. 3). While Oi makes one round revolution of the circle, the inner rotor rotates 1 / n times, and the tooth profile is formed by the envelope of the tooth profile curve group of the inner rotor thus formed. The outer diameter of the outer rotor was φ85 mm, and the eccentricity e between the inner rotor and the outer rotor was 3.2 mm. With this specification, pump rotors were prepared in which the combinations of the inclination angles of the tooth surfaces of the inner rotor and outer rotor were changed as shown in Table 1, and each pump rotor was assembled in a pump case to constitute an internal gear pump. The discharge pulsation width of the prototype pump was examined. This test was performed under the conditions of pump rotation speed: 4000 rpm, discharge pressure: 3 MPa, oil type: ATF, oil temperature: 80 ° C.

  The results of this test are shown in Table 1. From this test result, when the combination of the inclination directions of the tooth surfaces of the inner rotor and outer rotor can be made freely (when it is not guaranteed which of sample No. 1 to No. 6), the discharge pressure depends on the product. It can be seen that the variation width (discharge pulsation width) increases. Sample Nos. 2 to 5 (invention products) in which the direction of inclination of the tooth surface of the inner rotor and the direction of inclination of the tooth surface of the outer rotor are reversed are small in variation.

End view showing an example of the pump rotor of the present invention The figure which exaggerates the inclination of the tooth surface of a rotor same as the above Figure showing enlarged tip clearance Explanatory drawing regarding the definition of perpendicularity of the tooth surface (rotor radial direction displacement S1, S2 per 10 mm of rotor thickness) The figure which shows the state which aligned the inclination direction of the tooth surface of the inner rotor and the outer rotor in a meshing part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pump rotor 2 Inner rotor 2a Teeth 3 Outer rotor 3a Teeth 4 Shaft hole 5 Pump chamber 6, 7 Tooth surface t Chip clearance A, B End face of rotor Oi Inner rotor center Oo Outer rotor center e Eccentricity

Claims (2)

In an internal gear pump rotor that combines an inner rotor (2) and an outer rotor (3) manufactured through at least a sizing process,
For the inner rotor (2) and the outer rotor (3), an end surface on the side that intersects an acute angle with respect to the tooth surface (6, 7) of each rotor is an A surface, and an end surface that intersects an obtuse angle is a B surface. A rotor for an internal gear pump, wherein the inner rotor (2) and the outer rotor (3) are combined so that the A surface of the outer rotor and the A surface of the outer rotor are placed on the same side.   The inclination angle at the tooth tip of the tooth surface (6) of the inner rotor is θi, the displacement of the tooth surface in the tooth angle at the inclination angle θi per rotor thickness of 10 mm is S1, and the tooth tip of the tooth surface (7) of the outer rotor 2. The condition of 10 ≦ S1 + S2 ≦ 30 μm is satisfied, where θ0 is an inclination angle at the portion and S2 is a rotor radial displacement per 10 mm of the tooth surface at the inclination angle θo. Rotor for contact gear pump.

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