JP2009162106A - Rotor for internal gear pump, and manufacturing method for the rotor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent eccentric wearing of an engagement surface of an inner rotor and an outer rotor even when a pump rotor formed by a sintered alloy is used at a high pressure for enhancement of life of a rotor for an internal gear pump, suppression of performance deterioration and prevention of seizure. <P>SOLUTION: Teeth tips of the inner rotor 2 and/or the outer rotor 3 formed by the sintered alloy are made to an intermediate projection shape swelled in a radial direction on a central part in a rotor thickness direction. A right angle degree of the teeth tips 2a, 3a at end surface reference is made to it in which the displacement amount becomes 10 μm or less when it is represented by a displacement amount in a longitudinal right angle direction per 10 mm length together with this. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rotor for an internal gear pump configured by combining an inner rotor and an outer rotor, each formed of a sintered alloy, and a method for manufacturing the rotor.

  Internal gear pumps are widely used as oil pumps for car engines and automatic transmissions. As a conventional example of this type of internal gear pump, for example, there is one disclosed in Patent Document 1 below.

  The pump rotor employed in the internal gear pump is mainly composed of an inner rotor and an outer rotor having one tooth difference 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 tip may decrease due to the sizing. The squareness of the tooth tip referred to here is based on the end face, and the ideal angle with the end face is 90 °.

  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. The molding pressure is lowered. If there is a difference in molding pressure during sizing, there will also be a difference in the elastic restoration amount of the tooth surface after sizing at one end and the other end, which has a particularly large effect on the reduction of the squareness of the tooth tip. It is thought that there is.

  In any case, when the tooth tip is inclined with respect to the end face, the contact between the inner rotor and the outer rotor comes into contact with the local area, and the meshing between the rotors is not smooth, and the contact surface pressure due to the reduction of the contact face An increase also occurs.

  In general applications such as an engine oil pump and an AT (automatic transmission) oil pump, the discharge pressure is not so high, for example, about 2 to 3 MPa. For example, a CVT oil pump used at a high pressure, for example, a pressure of 4 MPa or more, may cause uneven wear on the meshing surface of the rotor due to local contact, and the uneven wear may trigger a part of the surface layer. It may come off. The uneven wear and peeling shorten the life of the pump rotor. In addition, the uneven wear powder and the release powder are bitten between the tooth surfaces, and the seizure of the rotor becomes a concern.

If the squareness of the tooth tip is poor, the above-described problems occur depending on the use conditions of the pump. However, in the rotor made of sintered alloy, the reduction of the squareness of the tooth tip due to the manufacturing method is inevitable. In Patent Document 2 below, the first engagement portion is not perpendicular to the end surface because the first engagement portion (tooth tip) 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

  Since the rotor of the internal gear pump makes the entire end surface flat without a step, the method of Patent Document 2 in which a part of the end surface is molded with a die together with the first engaging portion cannot be adopted. Further, since the difference in molding pressure due to the influence of the side resistance described above also occurs when a part of the end face is molded with a die, the method of Patent Document 2 uses the tip of the tooth due to the side resistance during powder molding or sizing. It is not effective in preventing the reduction of the perpendicularity.

  This invention prevents uneven wear of the meshing surfaces of the inner rotor and outer rotor even when the pump rotor made of sintered alloy is used at a high pressure to improve the life of the pump rotor and prevent seizure. The challenge is to make it.

  In order to solve the above problems, in the present invention, in the pump rotor of the internal gear pump in which the inner rotor and the outer rotor, each formed of a sintered alloy, are combined, the tooth tip of the inner rotor or the outer rotor is the rotor. A centrally convex shape bulging in the radial direction at the center in the thickness direction was used.

  Since the inner rotor is firmly assembled to the drive shaft, the degree of uneven wear due to the reduction in the squareness of the tooth tip becomes significant compared to the outer rotor that rotates freely. Therefore, although it is particularly effective to make the tooth tip of the inner rotor have the above-mentioned middle convex shape, it is also effective to make the tooth tip of the outer rotor the middle convex shape. In addition, there is an effect that the tooth tips of both the inner rotor and the outer rotor are formed in a middle convex shape.

  In the pump rotor according to the present invention, when the tooth tip has a center-convex shape, the right angle of the tooth tip with respect to the end face is also expressed as a displacement in the direction perpendicular to the longitudinal direction per 10 mm length and is 10 μm or less. A good effect can be expected.

  Next, an inner rotor and an outer rotor whose tooth tips are in a convex shape are manufactured by the following method. The method includes a sintered body obtained by sintering a green compact, a die, upper and lower punches, and a core, and a tooth surface molding portion is provided on the inner periphery or the outer periphery of the core, The tooth surface molding part is set in a sizing mold having a predetermined sizing allowance with respect to the tooth surface of the sintered body, pressure is applied to the sintered body with an upper punch, and then the first sizing is performed. The sintered body that has been subjected to the first sizing is once taken out from the die, turned over, and reset in the sizing mold to perform the second sizing.

  The present invention also provides such a manufacturing method. In this method, the second sizing is preferably performed by applying a molding pressure smaller than the molding pressure in the first sizing. In the production of the prototype rotor, about 80% of the first molding pressure was appropriate for the second molding pressure.

  In the pump rotor of the present invention, the tooth tip of the inner rotor or the outer rotor, or both, is formed in a middle convex shape, and the squareness of the tooth tip on the end surface reference is 10 mm along with the shape. Especially in the case of 10 μm or less in terms of displacement in the direction perpendicular to the longitudinal direction per length, the contact area between the tooth surfaces of the inner rotor and outer rotor is broadened compared to the conventional product, the surface pressure of the contact portion is reduced and the per-part The uneven wear of the meshing surface due to the above is suppressed, and the surface layer portion is hardly peeled off, thereby extending the life of the rotor. In addition, deterioration of pump performance is suppressed by suppressing wear, and further, wear powder and flaking powder are less likely to be generated, so that foreign matter is less likely to be caught in the meshing surface and seizure of the rotor is less likely to occur.

  Next, in the manufacturing method of the present invention, after the first sizing is completed, the rotor is turned over and the second sizing is performed, so that the molding pressure in the sizing applied to the one end side and the other end side of the rotor is averaged. The difference in the amount of elastic restoration after sizing caused by the difference in molding pressure between the one end side and the other end side is reduced, and the reduction in the squareness of the tooth tip is suppressed to be smaller than that of the conventional product.

  In the manufacturing method of the present invention, when the molding pressure in the second sizing is made smaller than the molding pressure in the first sizing, a better result is obtained than when the first and second molding pressures are made equal. Obtained. The molding pressure at the second sizing was about 80% of the molding pressure at the first time, but the appropriate value of the molding pressure is considered to vary depending on the molding conditions (such as the material and size of the rotor). .

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

  As the outer rotor 3, one having one more tooth than the inner rotor 2 is used. 3a is a tooth tip of the outer rotor.

  The pump rotor 1 is configured by combining the inner rotor 2 and the outer rotor 3 in an eccentric arrangement, and the pump rotor 1 is mounted on a housing 4 having a suction port 5 and a discharge port 6 as shown in FIGS. The internal gear pump 10 is housed. The internal gear pump 10 is engaged with the shaft hole 2 b of the inner rotor 2 through the drive shaft 7 shown in FIG. 2, and a driving force is transmitted from the drive shaft 7 to the inner rotor 2 to rotate the inner rotor 2. At this time, the outer rotor 3 is driven to rotate, and the volume of the chamber (pump chamber) 8 formed between the two rotors increases and decreases with the rotation of the inner rotor 2 and the outer rotor 3 to suck and discharge liquid such as oil. Is made.

  In the pump rotor 1 of FIG. 1, the inner rotor 2 is manufactured by the following method. As shown in FIG. 4, the tooth tip 2a of the inner rotor 2 swells radially outward at the central portion in the rotor thickness direction. Convex shape. This tooth tip 2a further has a perpendicularity with reference to the parallel end faces 2c and 2d, and the length L in FIG. 4 is 10 mm, and the longitudinal displacement amount δ per 10 mm length is 10 μm or less (gradient (% ) = 100 × δ / L, which is expressed by the gradient obtained by the formula: 0.1% or less).

A method of manufacturing the inner rotor 2 is shown in FIG. In this method, the die 11, the upper punch 12, the lower punch 13, and the core 14 are provided, and a tooth surface forming portion 11 a is provided on the inner periphery of the die 11, and the tooth surface forming portion 11 a is a tooth surface of the sintered body 9. In contrast, a sizing die having a predetermined sizing allowance, for example, a radial sizing allowance of about 0.02 to 0.1 mm is used. The sintered body 9 is pressed into the die 11 of the sizing die by applying pressure with the upper punch 12 to perform the first sizing. Thereafter, the sintered body 9 which has finished the first sizing is once taken out from the die, turned over, and set again in a sizing die, and the second sizing is performed. The first sizing by this method is performed by applying a load of 8 to 12 ton / cm ² (pressure of about 800 to 1200 MPa), for example. The second sizing is performed by applying a load of 6 to 10 ton / cm ² (pressure of about 600 to 1000 MPa), for example. The appropriate value of the second molding pressure is considered to vary depending on molding conditions (such as the material and size of the rotor), but better results are obtained when the molding pressure is smaller than the first molding pressure.

  In the first sizing, there is a difference in molding pressure between the one end side pressed against the upper punch 12 of the sintered body 9 and the other end side pressed against the lower punch 13 due to the side resistance, and the end surface 2d side is more than the end surface 2d side. As shown in FIG. 6, the amount of elastic recovery after sizing on the end face 2 c side where a large molding pressure acts increases, and as shown in FIG. 6, the outer diameter of the inner rotor 2 is tapered such that the tooth tip 2 a intersects the end face 2 c at an acute angle. I will. In the first sizing, the taper is added, and in the second sizing, the taper is inclined in the opposite direction. As a result, both ends of the tooth tip 2a are inclined in opposite directions, and the central portion of the tooth tip 2a in the rotor thickness direction swells outward to form an intermediate convex tooth tip. The mid-convex tooth tip has a better squareness on the end face reference than the tooth tip having the shape of FIG. 6 obtained by one-time sizing. Depending on the sizing conditions, a squareness is obtained such that the displacement δ in the direction perpendicular to the longitudinal direction per 10 mm length in FIG. 4 falls within 10 μm.

  The squareness of the tooth tip 3a of the outer rotor 3 can also be increased by the same method. When the perpendicularity of the tooth tip 3a of the outer rotor 3 is increased, a sizing mold in which a tooth surface molding portion (not shown, which also has a sizing allowance) is formed on the outer periphery of the core 14 is used. Using the sizing die, the rotor is turned over after the first sizing and the second sizing is performed.

The results of confirming the effect of the invention will be described below. An inner rotor with 6 teeth, each formed of an iron-based sintered alloy, and an outer rotor with 7 teeth were manufactured, and both were combined to produce a pump rotor with a rotor thickness of 15 mm. The tip diameter D1 of the inner rotor 2 shown in FIG. 1 is 45.1 mm, the root diameter D2 is 31.5 mm, the root diameter D3 of the outer rotor 3 is 51.9 mm, the tip diameter D4 is 38.3 mm, The eccentricity e of the inner rotor and outer rotor was set to 3.4 mm. This pump rotor was manufactured by the method of the present invention in which the inner rotor was sized twice. The inner rotor are those went under a load of 8 ton / cm ² a second sizing after the first sizing was performed by applying a load of 10ton / cm ² and (invention product 1), a first sizing The second sizing was performed by applying a load of 10 ton / cm ² (Invention 2). In both the inner rotors manufactured by either method, the tooth tip had a middle convex shape as shown in FIG. In addition, the squareness of the tooth tip of the inner rotor manufactured by the former method, that is, the amount of displacement δ in the longitudinal right direction per 10 mm length in FIG. 4 is 3 μm for Invention 1 and 6 μm for Invention 2 It was. These pump rotors were assembled in a housing to constitute an internal gear pump.
For comparison, an internal gear pump incorporating a conventional pump rotor (comparative example: the dimensions are the same as the invention product) in which the inner rotor is subjected to a single sizing by applying a load of 12 ton / cm ² to the housing. A comparison was made between the wear situation of the pump rotor after 200 hours of operation with these pumps operating under the same conditions and the change in pump discharge performance over time. The results are shown in Table 1.

    The amount of wear in Table 1 was determined by measuring the difference in tooth profile before and after the test with a three-dimensional measuring machine and using the difference as the amount of wear.

  As can be seen from the test results, the inventive products 1 and 2 have a smaller amount of wear than the comparative example, and the deterioration of the pump performance is also suppressed.

  Inventive product 1 in which the molding pressure in the second sizing is smaller than the molding pressure in the first sizing gives better results than the inventive product 2 in which the first and second molding pressures are the same. ing.

End view showing an example of the pump rotor of the present invention End view showing the internal gear pump using the pump rotor of FIG. 1 with the cover removed Sectional view along line XX in FIG. Explanatory drawing about perpendicularity of tooth tip Sectional drawing which shows an example of the metal mold | die for sizing The figure which exaggerates and shows the inclination state of the tooth tip of the rotor which performed the 1st sizing

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pump rotor 2 Inner rotor 2a Tooth tip 2b Shaft hole 2c, 2d End surface 3 Outer rotor 3a Tooth tip 4 Housing 5 Suction port 6 Discharge port 7 Drive shaft 8 Pump chamber 9 Sintered body 10 Internal gear pump 11 Die 11a Tooth surface Molding part 12 Upper punch 13 Lower punch 14 Core

Claims (5)

In the rotor of the internal gear pump that combines the inner rotor (2) and the outer rotor (3), each formed of a sintered alloy,
The tooth tip (2a) of the inner rotor (2) or the tooth tip (3a) of the outer rotor (3) has a middle convex shape that swells in the radial direction at the central portion in the rotor thickness direction. Rotor for internal gear pump. In the rotor of the internal gear pump in which the inner rotor (2) and the outer rotor (3) each formed of a sintered alloy are combined in an eccentric arrangement,
For the internal gear pump, wherein the tooth tips (2a, 3a) of the inner rotor (2) and the outer rotor (3) have a centrally convex shape bulging in the radial direction at the central portion in the rotor thickness direction. Rotor.   About the rotor whose tooth surface is an intermediate convex shape, the perpendicularity of the tooth tips (2a, 3a) with reference to the end surface is expressed as a displacement in the direction perpendicular to the longitudinal direction per 10 mm length and is 10 μm or less. The rotor for an internal gear pump according to claim 1 or 2. It is a manufacturing method of the inner rotor (2) or outer rotor (3) in any one of Claims 1-3, Comprising: The sintered compact (9) obtained by sintering a green compact,
A sizing having a die (11), upper and lower punches (12, 13), and a core (14), and a tooth surface forming portion (11a) is provided on the inner periphery of the die (11) or the outer periphery of the core (14). The first sizing is performed by the mold, and then the sintered body (9) after the first sizing is taken out from the die (11) and turned over, and is set again in the sizing mold and the second sizing. The manufacturing method of the rotor for internal gear pumps characterized by performing.   The method for manufacturing a rotor for an internal gear pump according to claim 4, wherein the second sizing is performed with a molding pressure smaller than the molding pressure in the first sizing.

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