JP2008157210A - Inner rotor of oil pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inner rotor of an oil pump equipped with fine trochoidal teeth. <P>SOLUTION: In a trochoidal tooth profile 1 of the inner rotor A of a trochoid pump, both shoulders 111 in a width direction on an addendum 11 of the trochoidal tooth profile 1 are formed in a tertiary or higher-order curve. The tertiary or higher-order curve is formed in a Bezier curve. The higher-order curve is formed in a curve composed by properly combining the Bezier curve and the tertiary or higher-order curve. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inner rotor of an oil pump having good-quality trochoidal teeth.

As an oil pump for automobiles, an inner rotor and an outer equipped with a trochoid gear are representative of those in which the number of teeth difference between an internal gear and an external gear is 1 and both gears rotate while continuously contacting at multiple points. There are some that consist of a rotor. This is because a plurality of volume fluctuation spaces are always formed between the internal gears of the outer rotor and the external gears of the inner rotor. By providing a discharge port of the oil pump, the pump is established.
JP-A-6-280752

  In general, a rotor having a trochoidal tooth profile is formed by parameters such as a basic circle diameter, a rolling circle diameter, an eccentricity, and a locus circle diameter [see FIG. 6 (A)]. Then, the locus circle is moved by matching the center position with the trochoid curve, and the outer shape of the inner rotor is constituted by the envelope. That is, the tooth profile is uniquely determined by each parameter (specification). The greater the amount of eccentricity in the parameters, the higher the tooth height (bottom to tip) and the wider the interdental space, so the theoretical discharge rate can be increased.

  However, the numerical value of the parameter has a range where the rotor tooth profile can be established. If the above-described eccentric amount is too large, the tooth profile has a cusp k near the minimum curvature (rotor shoulder), and the tooth profile cannot be established [ See FIGS. 6B and 6C]. Therefore, in order to establish the tooth profile while securing the theoretical discharge amount, the tooth profile has been modified so that the vicinity of the minimum curvature having a cusp is a gentle arc m and is established as the tooth profile of the inner rotor.

  However, if the arc approximation as described above is performed, a part of the tooth profile is cut off from the original rotor curve, and there is no difference from the situation where wear or sag progressed at the time of a new product, and the pump is mischievous. It only reduced the performance. Further, in order to increase the theoretical discharge amount in the same size rotor, it is necessary to increase the eccentric amount. However, as the amount of eccentricity is increased, the tooth profile has a cusp near the minimum curvature, and the tooth profile is not established. Therefore, the theoretical discharge amount was increased by correcting the profile with an arc having the minimum allowable curvature. If the trochoid curve (race tooth profile curve) is approximated by an arc, there is inevitably a deviation between the theoretical tooth profile curve and the arc approximation curve.

  The distance (clearance) between the inner rotor tooth surface and the outer rotor tooth surface is the same at any point on the theoretical tooth profile curve, but if the tooth surface deviates from the theoretical tooth profile curve due to the arc approximation, the clearance between the tooth surfaces becomes the rotor shoulder. It differs from the clearance of other parts at the part. In the above example, since the arc approximation curve is lower than the theoretical tooth profile curve, the clearance is larger at the rotor shoulder. Therefore, vibrations are generated in the inner rotor and the outer rotor due to fluctuations in the clearance between the tooth surfaces during rotation. Further, since the rotors vibrate, an abnormal noise called a rattling noise is also generated.

Further, since the rotor causes unintended vibrations, wear of the rotor tooth surface is promoted and the life is shortened. As tooth surface wear progresses, vibration and noise increase.
As an example of a rotor using a trochoid curve that does not perform arc approximation, Japanese Patent Laid-Open No. 6-280752 is cited. However, this is simply a parameter region of the trochoid curve in which no cusp is generated. In the parameter region in Patent Document 1, the amount of eccentricity is reduced, the tooth height is lowered, and the theoretical discharge amount is It is a small area. The object of the present invention is to provide a tooth profile that eliminates vibration and noise generated at the time of circular arc approximation as much as possible even in a parameter region where a cusp is formed near the minimum curvature that can increase the theoretical discharge amount in a rotor using a trochoid curve. There is to do.

  In the trochoidal tooth profile of the inner rotor of the trochoid pump according to the first aspect of the present invention, there is provided an inner rotor of an oil pump in which both shoulder portions in the width direction at the tip portion of the trochoidal tooth shape are formed by a higher order curve of the third order or higher. As a result, the above problems were solved.

  The invention according to claim 2 is the trochoidal tooth profile of the inner rotor of the trochoid pump, wherein the both shoulders in the width direction of the tip portion of the trochoidal tooth profile are formed by Bezier curves. Solved the problem. In the trochoidal tooth profile of the inner rotor of the trochoid pump, the invention according to claim 3 is a curve in which both the shoulders in the width direction of the tip portion of the trochoidal tooth profile are combined with a higher order curve and a Bezier curve as appropriate. By solving the above problem, the above-described problem was solved.

  According to the first aspect of the present invention, the amount of change in clearance between the tooth surfaces is reduced, so that the rotor rotates smoothly, and hence vibration and noise can be reduced as compared with the circular arc approximate rotor. Further, since the vibration of the rotor is reduced, the tooth surface wear is reduced, so that the durability can be increased. In addition, in approximation by arc, it is necessary to find a better approximation curve only with two items of the outer diameter of the circle, which is a component of the circle, and the center position of the circle.

  On the other hand, in higher order curves, a better approximation can be searched and the order and coefficient of the mathematical formula can be freely selected. As a result, a better approximation than the circular arc can be obtained. Further, the shape approximates to an ideal trochoid which is generally better as the order is increased. As a result, the amount of change in clearance between the inner rotor tooth surface and the outer rotor tooth surface due to the rotor rotation can be reduced, so that vibration and noise can be reduced and durability can be improved by reducing tooth surface wear. In the invention of claim 2, the Bezier curve is a high-order curve, and an effect substantially the same as that of claim 1 is achieved. The invention of claim 3 is a composite of a higher order curve and a Bezier curve, and can be an ideal inner rotor that approximates a trochoid curve.

  Hereinafter, the present invention will be described with reference to the drawings. The present invention relates to an inner rotor constituting an oil pump. In the oil pump, an inner rotor A and an outer rotor are housed in a rotor chamber in a pump housing. A trochoidal tooth profile 1 is formed on the outer peripheral side of the inner rotor A. The trochoid tooth profile 1 is formed by alternately forming a tooth tip portion 11 and a tooth bottom portion 12 alternately.

  For forming the trochoidal tooth profile 1 of the inner rotor A, as shown in FIG. 5A, first, a basic circle a, a rolling circle b, and a drawing circle c are set. Here, the molding of the trochoidal tooth profile 1 does not mean that the material is actually machined and is a machine, but a stage of numerical input of a shape in the design, which is a stage before the machine.

  First, in the rolling circle b, an eccentric point bt is set at a position separated from the diameter center bp by an appropriate amount. A distance between the diameter center bp and the eccentric point bt is referred to as an eccentricity bs. Then, the trochoid curve d is set by rolling the circle b around the outer circumference of the basic circle a.

  The position of the center cp of the drawing circle c moves along the trochoidal curve d, and the envelope of the movement locus of the drawing circle c forms the trochoidal tooth profile 1 as shown in FIG. . By increasing the amount of eccentricity bs of the rolling circle b, the recess of the tooth bottom portion 12 is increased, and the pump flow rate can be increased. However, when the amount of eccentricity bs is increased, shoulder portions on both sides in the width direction of the tip portion of the tooth tip portion 11 of the formed trochoid tooth profile 1 as shown by the two-dot chain line portions in FIGS. In the portion 111, a portion where the curve does not continue smoothly occurs. The shoulder portion 111 becomes a minimum curvature radius portion, is a substantially square portion, and has a sharp shape.

  This part is referred to as a cusp k. The cusp k is a very inconvenient part in the pump operation. Therefore, the shape correction is performed around the cusp k by the following means, and the shoulder portion 111 in which the trochoid curve is approximated to the theoretical tooth profile curve is formed. As described above, the cusp k is a minimum curvature portion, and the shoulder 111 near the cusp k is modified and formed into an optimum shape by a high-dimensional curve or a Bezier curve. This correction formed area is referred to as a correction formation area S.

  Next, a process of forming the correction formation region S by the Bezier curve and approximating the cusp k of the shoulder 111 to an ideal theoretical tooth profile curve will be described with reference to FIG. The Bezier curve has a minimum of two control points P. A curve is set around the control point P, and an arbitrary curve can be drawn between the adjacent control points P and P. In an arbitrary region, an ideal curve can be further drawn by arranging three or more control points P between continuous curves.

  (1) First, a control point P for drawing a Bezier curve is arranged. However, the control point P at the end of the curve is arranged on both outer ends of the planned formation area of the correction formation region S [see FIG. 2 (A)]. (2) The number of remaining control points P is arbitrarily set and arranged. Then, the control points P, P,... Are appropriately moved to set an optimal shape. As a specific example of movement, an arrow is set. (3) The inner rotor A having the shape set for the movement of the control point P is combined with the outer rotor to check the variation of the tip clearance. If the fluctuation of the tip clearance is excessive, the control point P is changed and the process is performed again.

  Next, the case where the correction formation region S is performed by a higher order curve will be described with reference to FIG. First, when the higher-order curve of the correction formation region S is a quadratic curve, two fixed points Q are set on both sides of the cusp k of the shoulder 111, and the two fixed points Q, Q are spanned. A line is formed. The correction formation region S that is a quadratic curve can be brought closer to a higher-order curve that is close to an ideal by further correcting. Next, when the higher order curve of the correction formation region S is a cubic curve, three fixed points Q are set around the cusp k of the shoulder 111, and the fixed points Q, Q, ... The correction formation region S is formed between them, and a high-order curve close to the ideal is formed. Even in the modified formation region S having the cubic curve, it is possible to approach a higher-order curve that is close to an ideal by further modifying.

  Next, when the correction formation region S is formed by a quintic curve, as shown in FIG. 4, five fixed points Q are set around the cusp k of the shoulder 111, and the five fixed points are set. A correction formation region S is formed between Q, Q,..., And a theoretical tooth profile curve having a higher-order curve close to ideal is formed. Here, in order to draw a higher-order curve in the correction formation region S, the fixed point Q is arranged in the correction formation range in the vicinity of the two fixed points Q at the outermost ends thereof, and is further approximately at the center of the correction formation range. A fixed point Q is set at.

  Then, with these five fixed points Q, the slopes of the correction curve and the trochoid curve can be made to coincide at the end portion. Higher order curves can be approximated to ideal trochoidal curves as the dimension increases. As described above, the correction formation region S is formed at the cusp k of the shoulder 111 by the higher-order curve or the Bezier curve, and the correction formation region S can be made closer to the theoretical tooth profile curve.

  As described above, the correction formation region S at the cusp k is theoretically determined by using a higher order curve (third order or higher) having a higher order than the circular arc or a Bezier curve in the vicinity of the minimum tooth profile curvature (shoulder portion 111). By mathematically obtaining an approximate expression closer to the tooth profile point sequence data, an approximate curve closer to the theoretical tooth profile curve is obtained, and the amount of clearance change between the tooth surfaces in the shoulder 111 can be reduced.

  Next, in the trochoid tooth profile 1 of the inner rotor A, the shoulders 111 in the width direction of the tooth tip portion 11 of the trochoid tooth profile 1 are combined into a curve in which a higher order curve of 3rd order or higher and a Bezier curve are appropriately combined. Thus, the modified formation region S is formed and the embodiment exists. In this embodiment, the correction formation region S is first set by a higher-order curve of 3rd order or higher, and shape correction is performed by a Bezier curve in order to bring it closer to the ideal curve in more detail.

(A) is a front view of the inner rotor of the present invention, (B) is an enlarged view of part A of (A), and (C) is an enlarged view of part A of (B). (A) is a drawing example in which the correction formation region is corrected and formed by a Bezier curve, and (B) is a drawing example in which correction correction is formed by a Bezier curve when the correction formation region is inappropriate. (A) is a drawing example in which the correction formation region is corrected and formed by a high-dimensional curve, and (B) is a drawing example in which the correction formation region is corrected and formed by a higher-dimensional curve. It is an example of drawing in which a correction formation area is corrected and formed by a five-dimensional curve. (A), (B) is the drawing example which shows the shaping | molding process to the stage before the correction formation area | region of an inner rotor is shape | molded. (A) is a front view of the inner rotor of a prior art, (B) is an enlarged view of a section of (A), and (C) is an enlarged view of a section of (B).

Explanation of symbols

Inner rotor ... A, trochoid tooth profile ... 1, tooth tip part ... 11, shoulder part ... 111.

Claims (3)

  A trochoid tooth profile of an inner rotor of a trochoid pump, wherein both shoulder portions in the width direction of the tip portion of the trochoid tooth profile are formed by a higher order curve of a third order or higher.   An inner rotor of an oil pump, characterized in that in the trochoid tooth profile of the inner rotor of the trochoid pump, both shoulders in the width direction of the tip portion of the trochoid tooth shape are formed by Bezier curves.   In the trochoid tooth profile of the inner rotor of the trochoid pump, the shoulders in the width direction of the tip portion of the trochoid tooth profile are formed by a curve in which a higher order curve of the third order or higher and a Bezier curve are appropriately combined. An oil pump inner rotor.

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