JP6017887B2 - Inner rotor manufacturing method and inner rotor - Google Patents

Description

  The present invention relates to a method for manufacturing an inner rotor, in which a tooth surface shape after assembly completion can be made very close to an ideal dimension value by assembling an inner rotor by press-fitting and fixing a shaft into a central hole of the inner rotor, and It relates to the inner rotor.

  2. Description of the Related Art Conventionally, in an internal gear type oil pump or the like, the inner rotor presses and fixes a shaft into the center hole of the inner rotor, and the inner rotor is also rotationally driven by rotating the shaft.

  There exists patent document 1 as this kind of thing. This patent document 1 is outlined. In addition, the code | symbol used in description uses what is used by patent document 1 as it is. In Patent Document 1, as shown in FIG. 1, the inner rotor 10 has four external teeth formed by a cycloid curve or the like, and has five internal teeth having a shape corresponding to the external teeth. The oil pump is configured by being incorporated in the outer rotor.

  The oil pump is driven by the rotation of the shaft 20 press-fitted into a hole 11 provided in the center of the inner rotor 10. FIG. 2 of Patent Document 1 shows the detailed shape of the tooth profile of the inner rotor 10. The solid line is the ideal tooth surface shape after press-fitting, and the dotted line is the tooth surface of the inner rotor 10 before press-fitting the shaft 20. Indicates the design shape.

  The design value (dotted line) of the tooth surface radius of the inner rotor 10 is configured to be smaller than the ideal value (solid line) and the difference from the ideal value gradually decreases from the tooth bottom to the tooth tip.

  Further, as described in paragraph [0019] in Patent Document 1, the shaft and the outer cylinder are press-fitted with a tightening margin from the formula (2) derived from the theoretical formula of a combined cylinder that has been widely used conventionally. In this case, the normal direction pressure (fit pressure) Pc at the contact surfaces of both members is expressed by the equation Pc = DD / 2 · Rm / (1 / EA + (Ro · Ro + Rm · Rm) / EB (Ro · Ro−Rm) * Rm) -NA / EA + NB + EB) It is described that it is obtained by (2).

  Further, as described in paragraph [0020] of Patent Document 1, the deformation amount (radius component) u of the outer cylinder outer diameter portion from the formula (3) derived from the theoretical formula of the combined cylinder that has been widely used conventionally. Is obtained by the formula u = 2 · Pc · Rm · Rm · Ro / EB / (Ro · Ro−Rm · Rm) (3).

  Further, as described in paragraph [0017] of Patent Document 1, the difference d3 between the design value R3 of the tooth surface radius before press-fitting the shaft and the ideal value r3 after press-fitting is expressed by the equation d3 = d1− (d1− d2) × d / (r2−r1) (1) is set.

  In other words, equation (1) can be expressed in an easy-to-understand manner. The amount of deformation caused by the press-fitting of the tooth surface shape of the inner rotor changes at a constant rate with respect to the difference in the size of the diameter. It is large on the side and small on the tooth tip side with a large diameter.

Japanese Patent No. 4118606

  The above configuration has the following problems. The above-described theoretical formula is a theoretical formula used on a cylinder, assuming a completely elastic body having no pores or the like inside the material. Therefore, there is a problem in applying the above-described theoretical formula as it is to a substantially gear-shaped object having a non-cylindrical shape such as an inner rotor that includes many pores and the like inside a sintered material. Also, depending on the number of teeth of the inner rotor, it may be unsuitable for applying the above theoretical formula.

  And even if it implements about invention of patent document 1, the tooth surface shape of the inner rotor after press-fit is not an ideal tooth surface shape, therefore, the efficiency (efficiency), silence, durability, etc. which were designed (expected) It is expected that it will be difficult to obtain. Further, as described in paragraph [0018] of Patent Document 1, when the inner rotor 10 is implemented, it is expected that a trial production cost and an additional confirmation time are required.

  An object (technical problem to be solved) of the present invention is to overcome the above-described problems and make the manufactured product based on the design value closer to the ideal value in the manufacture of the inner rotor.

  In view of this, the inventor has intensively and researched to solve the above-mentioned problems, and as a result, the invention of claim 1 includes an inner rotor made of an iron-based sintered material and a shaft press-fitted into the center hole of the inner rotor. The tooth surface radius of one tooth of the inner rotor is such that a design value before the shaft is press-fitted into the center hole is set smaller than an ideal value after the shaft is press-fitted, and the design value and the The above-mentioned problem was solved by adopting an inner rotor manufacturing method in which the difference from the ideal value is constant from the root of the inner rotor to the tooth tip.

  According to a second aspect of the present invention, in the first aspect, the difference between the design value of the tooth surface radius of one tooth of the inner rotor and the ideal value is the center of the press-fit tightening margin on one side of the shaft and the inner rotor. The above-described problems have been solved by using an inner rotor manufacturing method that is smaller than the value.

  In the first aspect of the present invention, the inner rotor is formed of an iron-based sintered material, and the tooth surface radius of one tooth of the inner rotor is the design value before the shaft is press-fitted into the center hole. It is set smaller than the ideal value after press-fitting and the difference between the design value and the ideal value is constant from the tooth bottom to the tooth tip of the inner rotor.

  In this way, the design value and the tooth surface shape of the ideal value of the inner rotor with the shaft, which is the target (target) value after press-fitting the shaft into the center hole of the inner rotor, can be formed as substantially the same shape. It becomes possible to design an inner rotor having high efficiency, high quietness, high durability, etc. according to a target (target).

  Further, when the material of the inner rotor is a general material having no pores, the thickness of the thinner tooth bottom is larger in the case of cylindrical theoretical calculation. On the other hand, in the present invention, the inner rotor is formed in a substantially gear shape made of a sintered material, and the deformation amount can be made substantially the same for both the tooth bottom and the tooth tip regardless of the thickness difference.

  Next, in the invention of claim 2, the actual tooth surface shape of the inner rotor after press-fitting the shaft is substantially equal to the ideal value of the inner rotor that is the target value after press-fitting the shaft into the center hole of the inner rotor. Therefore, it is possible to design a rotor having high efficiency, high quietness, high durability, etc. as intended in the oil pump characteristics.

  In addition, since it is possible to know in advance how much the inner rotor dimensions should be changed, actually make a prototype, press the shaft into the center hole of the inner rotor, and measure the swollen dimensions after the press-fitting. The troublesome work of determining design dimensions can be eliminated.

  If the inner rotor manufactured by the manufacturing method of the present invention is used, the actual tooth surface shape of the inner rotor after press-fitting the shaft is smaller than the ideal value of the inner rotor, which is the target (target) value after press-fitting the shaft. Since they can be formed in substantially the same shape, it is possible to design an inner rotor that has high efficiency, high quietness, high durability, etc. as desired (targeted) in oil pump characteristics.

(A) is a front view of an inner rotor, (B) is a side view in a state in which a shaft and an inner rotor having a cross section are separated, and (C) is a perspective view of an inner rotor with a shaft. (A) is a front view of the inner rotor describing the difference between the conventional design value and the present invention design value M when the same ideal value is aimed at in the prior art and the present invention, and (B) is the (A) part of (A). It is an enlarged view. (A) is a front view with a partial cross section of the inner rotor with shaft, (B) is an enlarged cross sectional view of the shaft, (C) is an enlarged cross sectional view of the center hole, and (D) is the median of the tightening margin on one side. It is an expanded sectional view which shows the shaft and center hole which are shown.

  Hereinafter, the present invention will be described with reference to the drawings. In the present invention, the inner rotor is used in an internal gear type oil pump or the like and is mounted together with the outer rotor. An outer rotor (not shown) is disposed outside the inner rotor and has a shape having one more inner tooth than the inner rotor (see FIGS. 1A and 1B).

  A shaft 2 is attached to the inner rotor 1 and attached to a housing of an oil pump (not shown). The inner rotor 1 has a plurality of external teeth 11, 11,... Formed by a normal trochoid curve or the like [see FIG. As an embodiment of the present invention, the external teeth 11 have a configuration of 8 sheets. However, the number of external teeth 11 is not limited to eight, and may be eight or more or less.

  The material of the inner rotor 1 is a sintered material for machine structural parts, and the shaft 2 is made of a special steel bar. A shaft 2 is fixedly attached to the center hole 12 provided at the rotation center P of the inner rotor 1 by press fitting, and the inner rotor 1 also rotates together with the rotation of the shaft 2. In the present invention, a product in which the shaft 2 is mounted on the inner rotor 1 is a manufactured product, which is referred to as an inner rotor with a shaft.

  In the present invention, the tooth surface radius means a radius of curvature of a curve extending from the tip of the external tooth 11 to the bottom of the tooth. And the shape of the external tooth 11 of the inner rotor 1 is formed because the curve comprised by a curvature radius continues. In addition, an ideal value N and a design value M exist for manufacturing the inner rotor 1 [see FIG. 1 (A), FIG. 2 and FIG. 3 (A)].

  The ideal value N is a target dimensional value in the radial direction of the inner rotor with a shaft in which the shaft 2 is press-fitted into the center hole 12 of the inner rotor 1. The design value M is a dimension value in the radial direction in a state where the shaft 2 is not press-fitted into the center hole 12 of the inner rotor 1. That is, the design value M is a value in which various dimensions such as the tooth surface radius are set to be smaller than the ideal value N in anticipation of the ideal value N after the shaft 2 is press-fitted.

  Since the reference inner diameter H of the center hole 12 of the inner rotor 1 and the reference outer diameter D of the shaft 2 have a connection structure by press-fitting, a tightening margin is provided. The tightening allowance has a maximum value and a minimum value. The reference inner diameter H and the reference outer diameter D are dimensions having a tightening margin, and are shown below.

  At the reference inner diameter H of the center hole 12 in the inner rotor 1, the maximum value Δhmax of the tolerance is set and the minimum value is set to Δhmin (see FIGS. 1A, 1B, and 3C). Further, regarding the reference outer diameter D of the shaft 2, the maximum tolerance value is Δdmax and the minimum value is Δdmin (see FIGS. 1B and 3B).

となり、
最小で

となる。 Therefore, for the inner diameter of the center hole 12 of the inner rotor 1,
Max

And
At a minimum

It becomes.

となり、
最小で

となる。 Moreover, about the outer diameter of the shaft 2,
Max

And
At a minimum

It becomes.

  Here, regarding the minimum tolerance Δdmin of the shaft 2 and the maximum tolerance Δhmax of the center hole 12 of the inner rotor 1, the Δdmin of the shaft 2 is larger than the Δhmax of the inner rotor 1.

である。
すなわち、

である。 That is

It is.
That is,

It is.

となる。
ここで、中心孔１２の基準内径Ｈと、シャフト２の基準外径Ｄは等しく、

である。 For example, when the center hole 12 has a minimum tolerance Δhmin and the shaft 2 has a maximum tolerance Δdmax,

It becomes.
Here, the reference inner diameter H of the center hole 12 and the reference outer diameter D of the shaft 2 are equal,

It is.

となる。 Therefore, the maximum tightening allowance is

It becomes.

となり
したがって最小締め代量は、

となる。 When the center hole 12 has a maximum tolerance Δhmax and the shaft 2 has a minimum tolerance Δdmin,

Therefore, the minimum tightening allowance is

It becomes.

  The maximum tightening allowance and the minimum tightening allowance are the differences when the inner diameter of the center hole 12 and the outer diameter of the shaft 2 are viewed comprehensively. Actually, the inner diameter of the center hole 12 and the outer diameter of the shaft 2 are different. The amount that is equally halved when viewed from the press-fit tightening margin on one side in each diametrical direction, that is, the amount obtained by dividing the tightening margin amount by 2 is shown below.

である。
また、最小締め代量の片側半分は

である。 One half of the maximum tightening allowance is

It is.
One half of the minimum tightening allowance is

It is.

である。 Then, assuming that the average value of half of the maximum tightening allowance and half of the minimum tightening allowance is the median value Sb, the median value Sb is as follows.

It is.

  Further, the tooth surface radius of one tooth of the inner rotor 1 is set so that the design value M before the shaft 2 is press-fitted into the center hole 12 is smaller than the ideal value N. The difference between the design value M and the ideal value N is constant from the bottom to the top of the outer teeth 11 of the inner rotor 1. In addition to the above, the difference Sa between the design value M and the ideal value N of the tooth surface radius of any one tooth of the outer teeth 11 of the inner rotor 1 may be smaller than the median value Sb [ 2B and 3A].

となる。 That is

It becomes.

  Thereby, the actual tooth surface shape of the inner rotor 1 after press-fitting into the center hole 12 of the shaft 2 can be formed to be substantially equal to the ideal value N of the inner rotor 1, and the target ( It is possible to design a rotor having high efficiency, high quietness, high durability and the like as intended.

  Furthermore, when the inner rotor 1 is made of a general material having no pores, the thickness of the thinner tooth bottom is larger in the case of cylindrical theoretical calculation. On the other hand, the inner rotor has a substantially gear shape made of a sintered material, and the deformation amount can be made substantially equal for both the root and the tooth tip regardless of the thickness difference.

  In addition, since it is possible to know in advance how much the dimensions of the inner rotor 1 should be changed, a prototype was actually made, and the shaft 2 was press-fitted into the center hole 12 of the inner rotor 1, and the swelled after the press-fitting The troublesome work of measuring the dimensions and determining the design dimensions can be eliminated.

  Hereinafter, specific numerical values will be applied as examples of the present invention. The outer diameter of the shaft 2 is φ12.045 mm to φ12.053 mm, which is obtained by adding the reference outer diameter D, the minimum tolerance Δdmin, and the maximum tolerance Δdmax. The material is special steel bar.

  The shaft 1 is fixed to the center hole 12 of the inner rotor 1 by press fitting, and the outer diameter of the shaft 2 is slightly larger than the inner diameter of the center hole 12 of the inner rotor 1. There are eight external teeth 11 of the inner rotor 1. The inner rotor 1 has an inner diameter of φ12.00 to φ12.03 mm, which is obtained by adding a reference inner diameter H, a minimum tolerance Δhmin, and a maximum tolerance Δhmax.

  Accordingly, the minimum press-fit tightening amount is φ12.045−φ12.03 = 0.015 mm = 15 μm, and the maximum press-fit tightening amount is φ12.053−φ12.00 = 0.053 mm = 53 μm. The press-fitting allowance on one side obtained by dividing these numerical values by 2 is 7.5 μm to 26.5 μm. The median value of the press-fitting allowance on one side is 17 μm.

  In this embodiment, the design value M before press-fitting of the shaft 2 is uniformly in the radial direction (from the center to the radial direction) with respect to the ideal value N (target value) after the shaft 2 is press-fitted into the center hole 12 of the inner rotor 1. The size was reduced by 10 μm. This 10 μm is smaller than the median value of 17 μm of the press-fitting allowance on one side.

  Since it is only necessary to uniformly reduce the tooth surface shape of the inner rotor 1 by 10 μm, it is not necessary to design the correction amount of the tooth profile gradually for each location of the outer teeth 11 as in the prior art. There is an advantage that the design of the system becomes easy. FIG. 2 is a diagram showing a dimensional difference between the ideal value N after the press-fitting of the shaft 2 and the tooth surface shape of the inner rotor 1 after the press-fitting of the actual shaft 2.

  By applying the present invention, the difference from the ideal value N is within ± 5 μm, and the tooth surface shape of the inner rotor after the shaft press-fitting can be designed with high accuracy.

DESCRIPTION OF SYMBOLS 1 ... Inner rotor 1, 11 ... External tooth, 11a ... Tooth tip, 11b ... Bottom of tooth, 12 ... Center hole,
2 ... shaft, M ... design value, N ... ideal value.

Claims (2)

  An inner rotor made of an iron-based sintered material and a shaft that is press-fitted into the center hole of the inner rotor, and a tooth surface radius of one tooth of the inner rotor is a value before the shaft is press-fitted into the center hole. The design value is set smaller than the ideal value after press-fitting of the shaft, and the difference between the design value and the ideal value is constant from the tooth bottom to the tooth tip of the inner rotor. A method for manufacturing a rotor.   2. The difference between the design value of the tooth surface radius of one tooth of the inner rotor and the ideal value according to claim 1 is smaller than a median value of press-fitting allowances on one side of the shaft and the inner rotor. An inner rotor manufacturing method characterized by the above.

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