JP2011052654A - Internal gear pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems of cost increase and variation of pump performances caused by installation of a notch by achieving reduction of delivery pulsation and improvement of cavitation characteristics of an internal gear pump employing pump rotors in which difference of number of teeth between an inner rotor and an outer rotor is one without providing the notch for introducing delivery port pressure to a pump chamber beforehand. <P>SOLUTION: An initial end 8s of a delivery port 8 is advanced in a rotor rotation direction from a delivery port side close part of a pump chamber 9 rotated to a position at which the same is separated from a suction port 7, and is set at a position where chip clearance g of the delivery port side close part is in a range of 0.3-0.7 mm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an internal gear pump that reduces discharge pulsation and improves cavitation characteristics without increasing manufacturing costs.

  Internal gear pumps are widely used as oil pumps for car engines and automatic transmissions (AT). As a conventional example of the internal gear pump, there is one in which an inner rotor having N teeth and an outer rotor having (N + 1) teeth are arranged in an eccentric arrangement. In this type of pump, a pump chamber (pumping chamber) whose volume is increased or decreased by rotation of the rotor is created between the inner rotor and outer rotor constituting the pump rotor, and the pump chamber is formed in a pump case and a suction port and a discharge port. The air is alternately opened and the fluid is sucked and discharged. Such an internal gear pump is disclosed in Patent Document 1 below.

The internal gear pump disclosed in Patent Document 1 is provided with a notch (groove) extending from the start end of the discharge port in the direction opposite to the rotor rotation direction in the pump case, and the pressure of the discharge port is supplied to the suction port via the notch. In this way, the pump chamber is separated from the pump chamber, so that sudden changes in the pressure in the pump chamber when the pump chamber opens to the discharge port are alleviated to reduce discharge pulsation and improve cavitation characteristics. ing.
A similar internal gear pump is also disclosed in Patent Document 2 below.

JP 2003-214356 A JP 2004-332696 A

  In the pump disclosed in Patent Document 1, the starting position of the notch (the start end position connected to the discharge port) varies due to the inevitable machining error (variation in machining allowance) of the discharge port start end position. In the case where the notch extends and becomes gradually shallower in the forward direction, the notch depth varies due to the variation of the starting position, which causes variations in pump performance.

  Further, the pump of the same document requires notching, which affects productivity and is expensive. The same applies to the pump of Patent Document 2.

  In order to improve productivity and reduce costs, the present invention aims to improve an internal gear pump adopting a pump rotor in which the difference in the number of teeth between the inner rotor and the outer rotor is one, and a pre-discharge port to the pump chamber It is an object to reduce discharge pulsation and improve cavitation characteristics by introducing pressure without providing a notch.

In order to solve the above-mentioned problem, in the present invention, a pump case having a suction port and a discharge port, a pump rotor in which an inner rotor with N teeth and an outer rotor with (N + 1) teeth are combined in an eccentric arrangement is provided. In the internal gear pump housed in
The starting end of the discharge port is advanced in the rotor rotation direction from the pump chamber closed position, and the tip clearance (minimum gap between teeth of the inner rotor and outer rotor) of the discharge port side closed portion is 0.3 to 0.7 mm. Was set to a position.

  The tip clearance at the discharge port side confined portion of the pump chamber separated from the suction port occurs between the teeth of the inner rotor and the teeth of the outer rotor on the rear side in the rotor rotation direction. The tip clearance is normally minimized at the position where the pump chamber is disconnected from the suction port, and thereafter gradually increases until the rotor rotates a predetermined amount.

  The present invention is applied to a pump whose tooth profile is designed such that the tip clearance of the discharge port side confinement portion of the pump chamber separated from the suction port exceeds 0.3 mm. The tip clearance may be intentionally expanded to 0.3 mm or more by correcting the tooth profile.

  In the pump of the present invention, the leading end of the discharge port is advanced forward from the discharge port side closing point at the position where the pump chamber is separated from the suction port, and the tip clearance of the discharge port side closing portion is increased. It is set to a position that extends from 0.3 to 0.7 mm, and the discharge port pressure is introduced into the pump chamber separated from the suction port without providing a notch to reduce discharge pulsation and improve cavitation characteristics. Can be planned.

  The pressure of the discharge port continues from the pump chamber opened ahead of the discharge port through the tip clearance behind the pump chamber in the rotor rotation direction (= tip clearance at the discharge port side confinement portion of the subsequent pump chamber). Introduced into the pump room. As a result, the subsequent pump chamber separated from the suction port is pressurized, and the subsequent pump chamber opens to the discharge port in this state.

  In this way, the same situation as when a notch for pressure introduction is provided can be created without a notch. Therefore, the pump performance variation and cost increase due to the installation of the notch are solved together, and the pump has a stable performance. Can be provided at low cost.

  It should be noted that a rapid change in internal pressure when the pump chamber opens to the discharge port can be mitigated by introducing the pressure of the discharge port into the pump chamber separated from the suction port in advance, but the tip clearance is too small. If the discharge port pressure is not sufficiently introduced, the effect of mitigating the change in internal pressure is not fully exhibited. Further, if the tip clearance is too large, the introduction of the discharge port pressure into the pump chamber separated from the suction port becomes excessive, and the purpose of suppressing a rapid change in internal pressure of the pump chamber is lost. In order to deal with this problem, upper and lower limits are set for the tip clearance at the location where the starting end of the discharge port is set.

  By arranging the start end of the discharge port at the above position where the tip clearance of the discharge port side confining part is 0.3 to 0.7 mm, the pressure of the discharge port is excessive or insufficient in the pump chamber separated from the suction port It is possible to avoid the above problems by introducing it without any problems.

  Further, the tip clearance of the discharge port side confining portion is normally set to be minimum at a position where the pump chamber is separated from the suction port and gradually increased until the rotor rotates by a predetermined amount. In the case of such a design, since the internal pressure of the pump chamber increases due to the volume reduction until the pump chamber separated from the suction port reaches the discharge port, the pressure when the pump chamber opens to the discharge port. The prevention of sudden changes is made more effective.

The front view which shows an example of the internal gear pump of this invention by removing the cover of the case Diagram showing the starting point of advance angle setting (position where the pump chamber with the largest volume is confined on the discharge port side) Figure showing enlarged tip clearance at the discharge port start end (A) An explanatory diagram of a method for creating a special tooth profile of an inner rotor, (b) An image diagram showing the movement of the center of a tooth creation circle by the same method as above Illustration of outer rotor tooth profile creation method

  Embodiments of the present invention will be described below with reference to FIGS. An internal gear pump 1 shown in FIG. 1 employs a pump rotor 4 in which an inner rotor 2 and an outer rotor 3 are combined in an eccentric arrangement, and the pump rotor 4 is accommodated in a rotor chamber 6 formed in a pump case 5. Configured. The pump case 5 includes a cover (not shown) that covers the rotor chamber 6.

  A suction port 7 and a discharge port 8 are formed on the side surface of the rotor chamber 6 provided in the pump case 5. A pump chamber 9 is formed between the inner rotor 2 and the outer rotor 3, and the pump chamber 9 opens alternately to the suction port 7 and the discharge port 8 as the rotor rotates, and the pump chamber is formed by the rotation of the rotor during the suction stroke. As the volume of 9 increases, fluid such as oil is sucked into the pump chamber 9 from the suction port 7.

  Further, in the discharge stroke, the volume of the pump chamber 9 decreases as the rotor rotates, and the fluid in the pump chamber 9 is sent out to the discharge port 8. Reference numeral 10 denotes a shaft hole formed in the inner rotor 2, and a drive shaft (not shown) for rotating the inner rotor 2 is passed through the shaft hole 10.

  The pump rotor 4 is used in which the number of teeth of the outer rotor 3 is one more than the number of teeth of the inner rotor 2. The tooth shape is not particularly limited, and a tip clearance g formed between the teeth of the inner rotor 2 and the outer rotor 3 is secured at 0.3 mm or more at a position where the pump chamber 9 moved to the discharge stroke is opened to the discharge port 8. Therefore, rather than a pump that uses a tooth profile of a trochoid curve or a cycloid curve, the pump of the above-mentioned Patent Document 1 having a tooth profile that uses both a cycloid curve and an involute curve, and a tooth profile of a special shape (creation of the tooth profile) A pump employing the method described later is preferred. These pumps have a degree of freedom in the tooth profile design, and can ensure a discharge port side tip clearance of 0.3 mm or more at a position where the pump chamber separated from the suction port reaches the discharge port.

  The terminal end of the suction port 7 may be disposed at a basic design position (a position where the pump chamber having the maximum volume is confined), or as proposed in Patent Document 1 described above, the rotor is positioned more than the basic design position. You may arrange | position ahead in the rotation direction.

  The starting end 8 s of the discharge port 8 is located forward of the rotor rotation direction from the position (point Q in FIG. 2, where this is the starting point for setting the advance angle) where the pump chamber 9 having the maximum volume separated from the suction port 7 is confined on the discharge port side. The tip clearance g (see FIG. 3) at the discharge port side confinement portion of the pump chamber 9 is set to a position where the tip clearance g is expanded to 0.3 to 0.7 mm.

  As a result, before the pump chamber 9 separated from the suction port 7 opens to the discharge port 8, the discharge port pressure introduced into the preceding pump chamber 9 passes through the tip clearance g of the discharge port side confining portion. Introduced in the subsequent pump chamber 9, the pressure of the subsequent pump chamber 9 is increased, and the difference between the pump chamber pressure and the discharge port pressure when the subsequent pump chamber 9 opens to the discharge port 8 is reduced. A sudden change in pump chamber pressure can be effectively suppressed.

As for the tooth profile of the special shape, either or both of the tooth tip curve and the tooth bottom curve of the tooth profile of the inner rotor 2 are created by the method shown in FIGS. 4 (a) and 4 (b). Addendum curve and the tooth bottom curve in this way, the diameter Bd having the outer periphery of the points j overlaps with a reference point J on the base circle A of the inner rotor center O _I and concentric diameter Ad, creating a circle of Cd B, C Is constituted by a trajectory curve drawn by the point j when moving under the following conditions.
-Movement conditions for creation circles B and C-
· Creation circle B, C, the point j overlaps the reference point J on the reference circle A position (movement start point Spa, Spb) starts to move from the distance to the creation circle center from the inner rotor center O _I while changing the point j Gaha destination vertex T _T or moving end point Lpa located tooth bottom vertex T _B, moved to Lpb, and the distance R moved in the radial direction of the creation circle center reference circle a in the meantime, and The creation circles B and C of the tooth tip and the root rotate in the same direction as the movement direction of the circle at an angle θ at a constant angular velocity.

In this method, the tooth profile creation of the inner rotor 2 is performed by moving the tooth tip creation circle B in the range of the angle θ _T from the movement start point Spa to the movement end point Lpa while rotating at a constant angular velocity toward the straight line L ₂ . During this time, the distance R moves in the radial direction of the reference circle A. The tooth tip creation circle B rotates by the angle θ during the period from the movement start point Spa to the movement end point Lpa, and the point j on the creation circle is displaced by the angle θ and reaches the tooth tip vertex T _T. A half of the tooth profile of the tip of the inner rotor is drawn by the locus of the point j during this time.

At this time, the direction of rotation of the addendum creation circle B, the moving direction in the range of the angle theta _T are the same. That is, if the direction of rotation is clockwise, the direction of movement of the tooth creation circle B is also clockwise.

The tooth profile curve of the inner rotor 2 is completed by reversing the tooth profile curve drawn in this way with respect to the straight line L ₂ (making it symmetrical about the straight line L ₂ ).

The root curve can be similarly drawn. When the tooth creation circle C having the diameter φCd is moved in the range of the angle θ _B from the movement start point Spb to the movement end point Lpb while rotating at a constant angular velocity in the direction opposite to the direction in which the tooth tip creation circle B rotates, tooth profile of the dedendum of the inner rotor by the trace to a point j of the circumference of the bottom creating circle C has reached the tooth bottom vertex T _B from the position overlapping the reference point J is set on a straight line L ₃ on the reference circle a Half of is drawn.

  The created circles B and C by this method are a circle that moves from the movement start point to the movement end point while keeping the diameter constant, and a circle that moves from the movement start point to the movement end point while reducing the diameter by a certain amount per rotation angle. (Preferably a circle whose diameter at the movement end point does not become less than 0.2 times the diameter at the movement start point).

The trajectories AC ₁ and AC ₂ of the curves for moving the creation circles B and C are preferably such that the change rate ΔR of the distance from the inner rotor center O _I to the creation circle center becomes 0 at the movement end points Lpa and Lpb. It is also preferable that the trajectories AC ₁ and AC ₂ of the curves satisfy the following expression with respect to the rate of change ΔR of the distance from the inner rotor center O _I using a sine curve.
ΔR = R × sin (π / 2 × m / s)
Where s: number of steps, m = 0 → s
The orbits AC ₁ and AC ₂ may be a cosine curve, a higher order curve, an arc curve, an elliptic curve, or a curve created by combining these curves and a straight line having a certain slope.

Addendum vertex T _T and the tooth bottom vertex T _B is a straight line connecting the reference point J the inner rotor center O _I on the reference circle A as L _1, straight position rotated angle theta _T from the straight line L ₁ They are set on L _{2 and} on a straight line L ₃ at a position rotated by an angle θ _B from the straight line L ₁ . In addition, the angle θ _T between the straight line L ₁ and the straight line L ₂ and the angle θ _B between the straight line L ₁ and the straight line L ₃ are set in consideration of the number of teeth, the tip portion, the ratio of the installation region of the bottom portion, and the like. The

Addendum Creation circle B and dedendum creating circle C centered moving start point Spa of, Spb is located on the straight line _{L 1,} This also like a circle in the center of the moving end point Lpa, Lpb linearly _L 2, _{L 3} It's above.

  The root shape of the inner rotor 2 in which the curve created by the method of FIG. 4 is applied to the tooth tip may be created by the same method as the tooth tip using the tooth root creation circle C, or a known trochoidal curve. A tooth profile created using a tooth profile or a tooth profile of a cycloid curve may be employed. Similarly, the tooth tip shape of the inner rotor 2 in which the tooth profile curve created by the method of FIG. 4 is applied to the tooth bottom may be a tooth profile created using a trochoid curve or a tooth profile of a cycloid curve.

The outer rotor 3, as shown in FIG. 5, to revolve in a circle S having a diameter (2e + t) a center O _I of the inner rotor 2 at the center O _O around the outer rotor 3, the inner rotor center O _I is the circle The inner rotor 2 is rotated 1 / N times during one revolution of S, and the tooth profile is formed by an envelope of the tooth profile curve group of the inner rotor thus formed.
Where, e: the amount of eccentricity between the center of the inner rotor and the center of the outer rotor
t: Maximum gap between teeth of outer rotor and inner rotor pressed against it
N: Number of teeth of inner rotor

  The pump rotor that created the tooth profile in this way has a degree of freedom in setting the tooth profile of the inner rotor 2 and the outer rotor 3, and the tip clearance of the confined portion on the discharge port 8 side of the pump chamber 9 separated from the suction port 7 g can be secured to 0.3 mm or more.

An internal gear pump (invention) having a pump rotor with the following tooth profile was prototyped. The specifications of the prototype pump are shown below.
・ Number of inner rotor teeth N: 10
・ Outer rotor large diameter (bottom circle diameter): φ51.94mm
・ Outer rotor small diameter (bottom circle diameter): φ38.34mm
・ Inner rotor large diameter (tooth diameter): φ45.08mm
・ Inner rotor small diameter (tooth diameter): φ31.48mm
・ Eccentricity e: 3.4 mm
・ Diameter of reference circle: φ36.00mm
・ Diameter of tooth creation circle: φ1.98mm
-Diameter of root creation circle: φ1.62mm
-Theoretical discharge amount per 10 mm of rotor thickness: 8.52 cc / rev / cm
-Discharge port start end: Set to a position advanced from the basic design position to a position where the tip clearance g of the confined portion on the discharge port side is 0.5 mm.

  A performance evaluation test was conducted using the pump of the above specifications and a comparative pump of the same specification with the discharge port starting end at the basic design position and no advance angle setting.

As a result, while the discharge pulsation width of the comparative product was 586 kPa, the discharge pulsation width of the invention product in which the start end of the discharge port was set to the position where the discharge port side chip clearance was 0.5 mm was 269 kPa. In addition, the effect of reducing the discharge pulsation without the notch was confirmed.
Note that the discharge pulsation width in this test is that the discharge pressure is 2.5 MPa, the rotation speed is 5000 rpm, the oil type is ATF, and the oil temperature is 80 ° C., and the maximum pressure and the minimum pressure at this time are The difference (pulsation width) was determined.

DESCRIPTION OF SYMBOLS 1 Internal gear pump 2 Inner rotor 3 Outer rotor 4 Pump rotor 5 Pump case 6 Rotor chamber 7 Suction port 8 Discharge port 8s Discharge port start end 9 Pump chamber 10 Shaft hole g Tip clearance Q Position A to be confined by Reference circle Ad Diameter B of reference circle A Diameter of tooth tip creation circle φBd Diameter of tooth tip creation circle B Spa Movement start point L of tooth tip creation circle B Movement end point C of tooth tip creation circle B Tooth creation circle φCd Tooth The diameter Spb of the bottom creation circle C The movement start point Lpb of the root creation circle C The movement end point AC of the root creation circle C The curved path AC in which the center of the _one tooth creation circle B moves ₂ The center of the tooth creation circle C moves and orbital J reference circle dedendum vertex L ₁ inner rotor center point T _T inner rotor tooth tip apex T _B the inner rotor of the reference point j creation circle on a O _I and the reference point J of curve Rotation angle from the straight line theta _T straight line _{L 1} connecting the straight line _{L 3} inner rotor center _{O I} and the tooth bottom vertex _{T B} connecting straight line _{L 2} inner rotor center _{O I} and the tooth tip apex _{T T} connecting to the straight line _{L 2} (∠SpaO _I T _T )
θ _B Rotation angle from straight line L ₁ to straight line L ₃ (∠SpbO _I T _B )
The number of teeth O _I inner rotor center of the eccentric amount t tip clearance N inner rotor in the radial direction moving distance ΔR range rate pa creation circle R around e the inner rotor center and the outer rotor center of R creation circle O _O outer rotor center S 2e + t Circle with a diameter of

Claims (2)

A pump in which an inner rotor (2) with N teeth and an outer rotor (3) with (N + 1) teeth are arranged eccentrically to create a pump chamber (9) between which the volume increases and decreases as the rotor rotates. In the internal gear pump configured by housing the rotor (4) in a pump case (5) having a suction port (7) and a discharge port (8),
The start end (8s) of the discharge port was set to a position where the tip clearance (g) of the discharge port side confinement part of the pump chamber (9) separated from the suction port (7) was 0.3 to 0.7 mm. An internal gear pump characterized by that. As the pump rotor (4),
The diameter at which at least one of the tooth tip curve and the tooth bottom curve overlaps with the reference point (J) on the reference circle (A) of the diameter (Ad) concentric with the inner rotor center (O _I ) on the outer periphery An inner rotor (2) formed by a locus curve drawn by the point (j) when the creation circle (B, C) of (Bd, Cd) moves satisfying the following conditions, and the inner rotor (2 The center (O _I ) of the outer rotor (3) is revolved by drawing a circle (S) with a diameter (2e + t) around the center (O _O ) of the outer rotor (3), and the inner rotor center (O _I ) The inner rotor (2) is rotated 1 / N times during one revolution, and the outer rotor (3) having a tooth profile formed by an envelope of the tooth profile curve group of the inner rotor thus formed is used. The internal gear pump according to claim 1.
-Movement conditions for creation circles B and C-
· Creation circle B, C, the point j overlaps the reference point J on the reference circle A position (movement start point Spa, Spb) starts to move from the distance to the creation circle center from the inner rotor center O _I while changing the point j Gaha destination vertex T _T or moving end point Lpa located tooth bottom vertex T _B, moved to Lpb, and the distance R moved in the radial direction of the creation circle center reference circle a in the meantime, and The creation circles B and C rotate at an angle θ at a constant angular velocity in the same direction as the movement direction of the circles.

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