JP5771848B2 - Internal gear type oil pump rotor - Google Patents

Description

  The present invention relates to an internal gear type oil pump rotor that sucks oil by an inner rotor and an outer rotor and then discharges the oil.

  The internal gear type oil pump is driven by the inner rotor connected to the drive shaft and the inner rotor, and the volume of the pump chamber formed between the outer rotor having one tooth more than the inner rotor is increased or decreased. It is a pump which conveys oil by doing. Due to its simple structure, low noise and high efficiency, the internal gear type oil pump is used as an automobile part. For example, it is used as an oil pump for generating hydraulic pressure for an automatic transmission or an oil pump used for engine lubrication.

  As a tooth profile of this type of internal gear oil pump, a trochoid curve, a cycloid curve, a curve obtained by combining a cycloid curve and an involute curve, or a curve created by the method disclosed in Patent Document 1 is used.

  Conventionally, in this type of internal gear type oil pump, cavitation is generated during high-speed rotation, so that reduction in volumetric efficiency in a high rotation range and deterioration of a rotor, a pump case and the like have been problems. In order to solve this problem, a technique is known in which the tooth bottom portion of the outer rotor is deepened to create a pocket portion, and the area of the entrance / exit of the pump chamber is increased (Patent Document 2).

WO 2010/016473 A1 Japanese Patent Laid-Open No. 63-167087

  The technique disclosed in Patent Document 1 has a problem in that the tooth tip of the inner rotor enters the tooth bottom of the outer rotor, the binding gap of the pump chamber is widened, and the volumetric efficiency is reduced.

  Therefore, an object of the present invention is to prevent a decrease in pump performance even if a pocket portion is provided in the outer rotor tooth bottom.

  In order to solve the above problems, in the present invention, an internal gear type oil pump rotor including an inner rotor having external teeth and an outer rotor having internal teeth meshing with the external teeth, the outer rotor being a pocket An angle α formed by a tangent line of the tooth profile curve of the outer rotor and a straight line passing through the center of the outer rotor and the center of the root at the starting point of the pocket portion is 70 degrees or more, 70 The internal gear type oil pump rotor is less than the degree.

  In the oil pump rotor according to the present invention, an angle α formed by a tangent line of the tooth profile curve of the outer rotor and a straight line passing through the center of the outer rotor and the center of the tooth root at the starting point of the pocket portion provided in the outer rotor is 40 degrees. As mentioned above, it is set as 70 degrees or less. Since the inner rotor is supported by the tooth profile of the outer rotor when the inner rotor enters the tooth bottom of the outer rotor, the inner rotor can be prevented from excessively entering the outer rotor. Therefore, it is possible to prevent the volumetric efficiency from being lowered due to the expansion gap in the pump chamber.

  It is preferable that the pocket portion has a side wall portion and a tooth bottom portion, and an outline of the side wall portion is the tangent line and the tangent line in the end face view of the outer rotor.

  In the end view of the outer rotor, when the outline of the side wall portion of the pocket portion is formed by the tangent line, the contact area between the inner rotor 1 and the outer rotor 2 can be gained at the pocket portion starting point. The outer rotor 2 can be prevented from entering the inner rotor 1 excessively.

Depth P in the radial direction of the pocket portion,
P = {(D2-D1) / 2} -e
Here, D1 is the major axis (mm) of the inner rotor 1, D2 is the root diameter (mm) of the pocket portion 8, and e is the amount of eccentricity (mm) between the inner rotor 1 and the outer rotor 2. The depth P is preferably set to satisfy the following formula (a).
0.1 mm ≦ P ≦ 0.3 mm (a)

  As the size of the pocket portion in the radial direction increases, the thickness of the outer rotor outer shape decreases. If it does so, the oil which leaks from the said pocket part to the outer periphery of the said outer rotor will increase, and the fall of volumetric efficiency will occur. The oil pump rotor according to the present invention can prevent a decrease in volumetric efficiency by defining the size of the pocket portion in the radial direction.

  It is preferable that the pocket portion is formed by an arc concentric with the outer periphery of the outer rotor.

  Since the tooth bottom portion of the pocket portion is formed by an arc concentric with the outer periphery of the outer rotor, the thickness of the outer periphery of the outer rotor is constant, and oil leakage from the pocket portion to the outer periphery of the outer rotor is prevented. be able to.

  The oil pump rotor according to the present invention can prevent the pump performance from deteriorating even if the pocket portion is provided at the tooth bottom of the outer rotor.

It is a front view which shows an example of the pump housing which accommodated the rotor of this invention. It is an enlarged view which shows an example of the inner rotor tooth tip combined with the outer rotor tooth bottom of this invention. It is drawing explaining the creation method of the tooth profile curve described in patent document 1. FIG. It is a figure which shows the relationship between the angle of the pocket part in an Example, the enlargement amount of a chip clearance, and the area of a pocket part. It is a figure which shows the relationship between the angle of the pocket part in another Example, the enlarged amount of chip clearance, and the area of a pocket part.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. As shown in FIG. 1, the oil pump includes an inner rotor 1, an outer rotor 2, a pump housing 3, a drive shaft 4, and a pump cover (not shown). The inner rotor 1 and the outer rotor 2 are housed in a gear chamber 5 formed in the pump housing 3 in such a manner that the centers of the inner rotor 1 and the outer rotor 2 are combined at positions separated by an eccentric amount. A drive shaft 4 is fitted into the inner diameter of the inner rotor 1. Here, each part which comprises the oil pump is demonstrated in detail.

[Inner rotor]
The inner rotor 1 is made of a sintered alloy. As shown in FIG. 1, N outer teeth 6 are formed on the outer periphery of the inner rotor 1. The tooth profile of the external tooth 6 includes a trochoid curve, a cycloid curve, a curve that combines a cycloid curve and an involute curve, a curve that uses the locus of a point on the rotating circle, and the center of the rotating circle moves on the curve. Is used.

[Outer rotor]
The outer rotor 2 is manufactured from a sintered alloy. As shown in FIG. 1, N + 1 inner teeth 7 having one more tooth than the inner rotor 1 are formed on the inner periphery of the outer rotor 2.

  FIG. 2 is a view in which the tooth tip of the inner rotor 1 is pressed against the tooth bottom of the outer rotor 2. As shown in FIG. 2, a pocket portion 8 that does not contact the tooth tip of the inner rotor 1 is formed at the root of the outer tooth 6. The angle α formed by the tangent line 10 of the tooth profile curve of the outer rotor 2 and the straight line 11 passing through the center of the outer rotor 2 and the center of the root of the outer rotor 2 at the starting point 9 of the pocket portion 8 is 40 degrees. As described above, the angle is set to 70 degrees or less. For this reason, since the inner rotor 1 is supported by the inner teeth 7 of the outer rotor when the inner rotor 1 is pressed against the tooth bottom of the outer rotor 2, the inner rotor 1 is excessively supported by the outer rotor 2. It can prevent entry. Therefore, it is possible to prevent the volumetric efficiency from being lowered due to expansion of the binding gap CL of the pump chamber.

  If the angle α is less than 40 degrees, the support force of the inner rotor 1 to the outer teeth 6 by the inner teeth 7 is not sufficient, and the inner rotor 1 may excessively enter the outer rotor 2. . If the angle α is greater than 70 degrees, a sufficient volume of the pocket portion 8 cannot be secured, cavitation may occur, and volume efficiency may be reduced.

  The pocket portion has a side wall portion 12 and a tooth bottom portion 13. In the end view of the outer rotor 2, the outline of the side wall portion 12 is formed by the tangent line 10. When at least a portion of the side wall 12 of the pocket portion 8 extending from the start point 9 is the tangent line 10, the contact area between the inner rotor 1 and the outer rotor 2 can be increased at the pocket portion start point. Therefore, the outer rotor 2 can be prevented from entering the inner rotor 1 excessively.

Depth P in the radial direction of the pocket portion 8 is
P = {(D2-D1) / 2} -e
Here, D1 is the major axis of the inner rotor 1, D2 is the root diameter of the pocket portion D2 and D is the amount of eccentricity between the inner rotor 1 and the outer rotor 2, and the depth P is as follows: Is set to satisfy the formula (a).
0.1 mm ≦ P ≦ 0.3 mm (a)

  When the formula (a) is satisfied, the volume of the pocket portion 8 can be sufficiently secured, and the occurrence of cavitation can be prevented. Further, oil leakage from the outer periphery of the outer rotor 2 can be prevented.

  The pocket portion 8 is formed by the tangent line 10 that is the side wall portion 12 and the tooth bottom portion 13 of the pocket portion 8, and the tooth bottom portion 13 is an arc concentric with the center of the outer rotor 2.

  Since the arc is concentric with the center of the outer rotor 2 and the outer rotor outer periphery has a constant thickness, the outer rotor 2 cannot have a portion where the side seal width is reduced, and from the outer periphery of the outer rotor 2. Oil leakage can be prevented.

[Tooth profile curve]
The tooth profile curve used for the inner rotor 1 is a trochoid curve, a cycloid curve, a curve combining a cycloid curve and an involute curve, or a curve created by the method described in Patent Document 1 (hereinafter referred to as the curve of Patent Document 1). )

The method described in Patent Document 1 shown in FIG. 3 is as follows.
Following creation circle B or C movement conditions of (1) to (3) meet by moving the created circle B or C, overlaps the reference point J on the base circle A is an inner rotor center O _I concentrically between them A trajectory curve drawn by one point j on the creation circle B or C is obtained on the creation circle. Then, from the reference circle center O _I addendum curve of the tooth profile drawn symmetrically with respect to the straight line L ₂ or L ₃ reaching the addendum vertex T _T or tooth bottom vertex T _B, at least one of the tooth bottom curved.

(1) When the creation circle B or C is arranged so that the point j on the creation circle overlaps the reference point J on the reference circle A, the position of the creation circle center pa or pb is moved to the starting point Let it be Spa or Spb. Then, the position of the created circle center pa or pb when the point j on the creation circle was placed the creation circle B or C, as located at the tooth tip apex T _T or the tooth root apex T _B Is the movement end point Lpa or Lpb. The creation circle center pa or pb moves on the creation circle center movement curve AC ₁ or AC ₂ from the movement start point Spa or Spb to the movement end point Lpa or Lpb, and the creation circle B or C is the circle of the circle It rotates at a constant angular velocity in the same direction as the moving direction.
(2) The creation circle center movement curve AC ₁ or AC ₂ is a distance in the reference circle diameter direction from the inner rotor center O _I to the creation circle center pa or pb, and the movement start point Spa or Spb to the movement end point. While reaching Lpa or Lpb, the distance is increased in the tooth tip curve, or the distance is decreased in the tooth bottom curve.
(3) the radius of the addendum apex T _T is the radius of the reference circle longer or the tooth root apex than the length obtained by adding the creation diameter at moving start point to the radius of A T _B from the radius of the reference circle A It is shorter than the length minus the creation circle diameter at the movement start point.

Here, when the creation circle center pa or pb moves from the movement start point Spa or Spb on the creation circle center movement curve AC ₁ or AC ₂ , the movement amount ΔR moved in the radial direction of the reference circle A is: The following formula is satisfied.
ΔR = R × sin ((π / 2) × (m / S))
R is (distance R ₁ from the inner rotor center O _I to the movement end point Lpa) − (distance R ₀ from the inner rotor center O _I to the movement start point Spa), or (from the inner rotor center O _I Distance r ₀ ) to the movement start point Spb) − (distance r ₁ from the inner rotor center O _I to the movement end point Lpb), S is the number of steps, m = 0 → S, and the number of steps S is , The angle θ _T formed by the movement start point Spa or Spb, the inner rotor center O _I and the movement end point Lpa or Lpb: ∠Spa, O _I , Lpa or θ _B : ∠Spb, O _I , Lpb at equal intervals Say the number divided.

  The tooth profile curve of the outer rotor 2 is formed by revolving the center of the inner rotor 1 as a circle having a diameter (2e + t) around the center of the outer rotor 2 after creating the curve of the inner rotor 1. The inner rotor 1 was rotated 1 / N times while the circle revolved once, and the circle was created by the envelope curve group of the inner rotor 1 thus created. Here, t is a clearance between the inner rotor 1 and the outer rotor, and N is the number of teeth of the inner rotor 1.

[Pump housing]
The pump housing 3 is manufactured from cast iron or aluminum alloy. As shown in FIG. 1, a cylindrical gear chamber 5 is formed on one end surface of the pump housing 3. A shaft hole into which the drive shaft is inserted, a suction port that is an oil introduction port, and a discharge port that is an oil discharge port are formed on the bottom surface of the gear chamber.

  The shapes of the suction port and the discharge port are designed according to the gear tooth profile. In the gear chamber 5, a crescent-shaped protrusion called a crescent may be formed depending on the tooth profile of the rotor. This embodiment is also effective for an oil pump in which a crescent is formed.

Using the following tooth profile, the relationship between the angle α and the amount of increase in the tip clearance was determined.
Number of inner rotor teeth: 8 Number of outer rotor teeth: 9 Tooth profile curve used: Curved inner rotor tooth profile inversion circle diameter: 3.6 mm combined with cycloid curve and involute curve
Inner rotor tooth profile abduction circle diameter: 3.1 mm
Eccentricity: 3.6
Maximum pump chamber area: 150mm ²

  The dimensions of the pocket portion 8 are shown in Table 1 below. FIG. 4 shows the relationship between the angle α, the amount of enlargement of the binding gap CL, and the area of the pocket portion in each sample.

As can be seen from FIG. 4, in the case of the sample 1 in which the angle α is less than 40 degrees, the amount of enlargement of the binding gap CL exceeds 0.05, and a decrease in volume efficiency can be expected. In the case of the sample 5 in which the angle α is more than 70 degrees, the area of the pocket portion is as small as 0.3% (0.45 mm ² ) or less of the maximum area of the pump chamber, and the effect of preventing cavitation during high-speed rotation cannot be obtained.

Next, the relationship between the angle α and the amount of expansion of the tip clearance was determined using the following tooth profile.
Inner rotor tooth number: 5 Outer rotor tooth number: 6 Tooth profile curve used: Curved inner rotor tooth profile inversion circle diameter: 3.6 mm combining cycloid curve and involute curve
Inner rotor tooth profile abduction circle diameter: 9.8 mm
Eccentricity: 3.35
Maximum pump chamber area: 125mm ²

  The dimensions of the pocket portion 8 are shown in Table 2 below. FIG. 5 shows the relationship between the angle α, the amount of chip clearance expansion, and the pocket area in each sample.

As can be seen from FIG. 5, in the case of the sample 6 in which the angle α is less than 40 degrees, the enlargement amount of the binding gap CL exceeds 0.05, and a decrease in volume efficiency can be expected. In the case of the sample 10 in which the angle α is more than 70 degrees, the area of the pocket portion is as small as 0.3% (0.36 mm ² ) or less of the maximum area of the pump chamber, and the effect of preventing cavitation during high-speed rotation cannot be obtained.

  Next, using the inner rotor of Example 1 and the outer rotor having the pocket portions having the dimensions shown in Table 3, the relationship between the depth P of the pocket portion 8 and the cavitation preventing effect was examined.

The conditions of the pump test are
Pressure: 1.0 MPa
Temperature: 120 ° C
Rotation speed: 1500rpm, 5000rpm
Oil type: ATF
It is. Table 3 shows the volumetric efficiency at each rotational speed.

  From Table 3, when the depth P is less than 0.1 mm, the volumetric efficiency at the time of high rotation is lowered, and it is expected that cavitation occurs. Therefore, it can be seen that the effect of preventing cavitation by the pocket portion is not obtained. When the depth P is larger than 0.3 mm, the volume efficiency at the time of low rotation is low, so that oil is expected to leak to the outer periphery of the outer rotor.

  The internal gear pump of the present invention can be suitably used as an oil pump for lubricating a car engine or an automatic transmission (AT).

DESCRIPTION OF SYMBOLS 1 Inner rotor 2 Outer rotor 3 Pump housing 4 Drive shaft 5 Gear chamber 6 Outer tooth of inner rotor 7 Inner tooth of outer rotor 8 Pocket part 9 Starting point of pocket part 10 Tangent line of outer rotor tooth profile curve at starting point of pocket part A straight line passing through the center of the outer rotor and the center of the root of the outer rotor 12 Side wall portion of the pocket portion 13 Tooth bottom portion of the pocket portion

Claims (4)

An internal gear type oil pump rotor including an inner rotor having external teeth and an outer rotor having internal teeth meshing with the external teeth,
The outer rotor has a pocket portion at the tooth bottom,
An internal gear type in which an angle α formed by a tangent line of the tooth profile curve of the outer rotor and a straight line passing through the center of the outer rotor and the center of the root at the starting point of the pocket portion is 40 degrees or more and 70 degrees or less. Oil pump rotor. The internal gear type oil pump rotor according to claim 1, wherein the pocket portion has a side wall portion and a tooth bottom portion, and an outline of the side wall portion is the tangent line in an end view of the outer rotor. . Depth P in the radial direction of the pocket portion,
P = {(D2-D1) / 2} -e
Here, D1 is the major axis (mm) of the inner rotor, D2 is the root diameter (mm) of the pocket portion, and e is the amount of eccentricity (mm) between the inner rotor and the outer rotor. The internal gear type oil pump rotor according to claim 1 or 2, wherein P satisfies the following formula (a).
0.1 mm ≦ P ≦ 0.3 mm (a)   The internal gear type oil pump rotor according to claim 2 or 3, wherein the pocket portion is formed by an arc whose tooth bottom is concentric with the outer periphery of the outer rotor.

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