JP2014114757A - Inscribed gear pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inscribed gear pump achieving high efficiency and low noise by becoming high-tooth.SOLUTION: A tooth form of an outer gear 2 is formed asymmetrically between a meshing side and a non-meshing side. A curve forming the tooth form of the outer gear 2 is, on the meshing side, a relatively gentle curve 11, in which the nearer it goes to a tooth root 4b, the larger the curvature gradually becomes, and on the non-meshing side, the curve is a relatively steep curve 12, in which the nearer it goes to a tooth root 4c, the smaller the curvature gradually becomes. The curve 11 on the meshing side and the curve 12 on the non-meshing side are continuously connected at a tooth tip 4a.

Description

  The present invention relates to an internal gear pump used for, for example, a pump for supplying hydraulic pressure to a transmission (transmission) of an automobile.

  As a hydraulic pump for an automobile transmission, an internal gear pump called a trochoid pump is often used.

  Trochoid pumps are usually formed with symmetrical tooth shapes so that they have the same shape for forward rotation and reverse rotation. However, Patent Document 1 discloses that the tooth shape is asymmetric between the positive rotation meshing side and the non-meshing side. It is disclosed that.

Japanese Examined Patent Publication No. 7-56268

  Since a hydraulic pump for an automobile transmission is mounted in a limited space of a vehicle body, it is required to be compact, and it is also required to satisfy both conflicting performances of high efficiency and low noise.

  For high efficiency, it is known that reduction of fluid friction loss by reducing the pump diameter is effective. That is, even with the same outer diameter, the internal gear pump has a larger discharge rate as the teeth are increased (the eccentric amount between the outer gear and the inner gear is increased). On the other hand, if the discharge amount is constant, the diameter can be reduced by increasing the teeth, thereby reducing the sliding resistance at the outer diameter portion and increasing the efficiency.

  In the conventional internal gear pump, when the teeth are increased, a cusp is generated in the tooth profile (trochoid interference), and the meshing condition is lost.

  An object of the present invention is to provide an internal gear pump that can achieve high efficiency and low noise by increasing the number of teeth.

  The internal gear pump according to the present invention is an internal gear pump having an inner gear and an outer gear, and the tooth shape of the outer gear is formed asymmetrically between the meshing side and the non-meshing side, and a curve forming the tooth profile Is a relatively gentle curve with a gradually increasing curvature on the meshing side, and a relatively steep curve with a gradually decreasing curvature on the non-meshing side, The meshing-side curve and the non-meshing-side curve are connected continuously at the tooth tip.

  In a general internal gear pump, the tooth profile of the outer gear is formed symmetrically on the meshing side and the non-meshing side, whereas in the internal gear pump of the present invention, the tooth profile of the outer gear is non-meshing with the meshing side. It is formed asymmetrically with the meshing side. Usually, the internal gear pump is used with a constant rotation direction. By defining the rotation direction, it is easy to obtain a tooth profile that prevents trochoidal interference. In addition, in the conventional trochoid pump, the tooth profile is formed using an arc, whereas in the internal gear pump of the present invention, the tooth profile is formed using a curve whose curvature gradually changes. Therefore, the occurrence of cusps is suppressed. Further, in the internal gear pump of the present invention, the meshing side is a relatively gentle curve with the curvature gradually increasing toward the tooth root, and the non-meshing side is a relatively steep curve with the curvature gradually decreasing toward the tooth root. Thus, it is possible to increase the teeth (large amount of eccentricity between the outer gear and the inner gear).

  The inner gear is created from the outer gear and has a smooth curve on the meshing side. In the inner gear, a cusp is generated, but the portion where the cusp is generated is on the non-engagement side, and no adverse effect is caused by the cusp.

  Thus, in the past, when the teeth were increased, cusps were generated and appropriate meshing conditions could not be obtained, but the increase in teeth was limited, whereas the internal gear pump according to the present invention increased the meshing rate. The occurrence of cusps can be suppressed, and the meshing does not collapse even when the teeth are increased, so that the rotational fluctuation and the accompanying torque fluctuation, hydraulic pulsation and vibration can be suppressed to increase the discharge amount.

  An ellipse can be used as the curve whose curvature gradually changes. Specifically, in the curve forming the tooth profile, the meshing side and the non-meshing side are both formed by a part of an ellipse, and the short radius of the ellipse forming the meshing side and the ellipse forming the non-meshing side are formed. The major radius is preferably a common line segment.

  The curve for achieving higher teeth is not limited to an ellipse, but by using an ellipse, a curve having an appropriate tooth profile can be easily obtained.

  According to the internal gear pump of the present invention, as described above, since the meshing does not break even when the teeth are increased, the rotational fluctuation, the accompanying torque fluctuation, hydraulic pulsation and vibration are suppressed, and the discharge amount is increased. Can do. Therefore, the diameter of the inscribed gear pump can be reduced, and the efficiency of the inscribed gear pump can be increased.

FIG. 1 is a cross-sectional view of an internal gear pump showing one embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of the main part of the outer gear. FIG. 3 is an enlarged cross-sectional view of a main part for explaining a curved shape forming a tooth profile of the outer gear. FIG. 4 is an enlarged cross-sectional view of the main part of the inner gear.

  Hereinafter, an embodiment of an internal gear pump of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the internal gear pump (1) includes an outer gear (2) having a plurality of teeth (4) and a plurality of teeth (5) having one tooth fewer than the outer gear (2). An inner gear (3).

  The outer gear (2) is rotatably arranged in a casing having a suction port and a discharge port (not shown). The inner gear (3) is disposed in the outer gear (2) so as to have a rotation center at a position that is decentered by a predetermined amount E from the rotation center of the outer gear (2), and is arranged coaxially with the inner gear (3). It is rotationally driven by a drive shaft (not shown).

  By driving the inner gear (3), the inner gear (3) and the outer gear (2) rotate relative to each other. Here, both the gears (2) and (3) are assumed to rotate clockwise. The relative rotation of both gears (2) and (3) changes the volume of the gap formed between both gears (2) and (3), and as a result, fluid is sucked from the suction port when the gap increases. The sucked fluid is conveyed by the rotation of both gears (2) and (3), and further, the fluid is discharged from the discharge port when the gap is reduced.

  In FIG. 1, since both gears (2) and (3) are rotated clockwise, the counterclockwise portion of the teeth (4) of the outer gear (2) and the teeth (5) of the inner gear (3) The part of the outer gear (2) that comes into contact with the clock side part of the outer gear (2) contacts the time side part of the tooth (4) of the outer gear (2) and the counterclockwise part of the tooth (5) of the inner gear (3). The part to be engaged is the non-meshing side.

FIG. 1 shows a state in which the inner gear (3) is eccentric to the uppermost position. In this state, the pitch point (P) where the pitch circle (2p) of the outer gear (2) and the pitch circle (3p) of the inner gear (3) are in contact is the uppermost, and the meshing point (M) is , Near the pitch point (P). In the vicinity of the pitch point (P), the tooth root position of the outer gear (2) and the tooth tip position of the inner gear (3) coincide, and in the vicinity of the seal point (S) that is approximately 180 ° away from the pitch point (P). The tooth tip of the outer gear (2) is coincident with the tooth tip of the inner gear (3). From this, it can be seen that the tooth heights of the teeth (4) and (5) of both gears (2) and (3) are h = 2 × E. The radius ratio of the pitch circles (2p) (3p) of both gears (2) (3) is equal to the gear ratio. When the radius of the pitch circle (3p) of the inner gear (3) is ρ1 and the radius of the pitch circle (2p) of the outer gear (2) is ρ2, the eccentricity E can be defined as E = ρ2−ρ1. The distance to the mesh point (M) is equal to the radius ρ1 of the pitch circle (3p) of the inner gear (3), and the distance to the seal point (S) is the tooth tip radius ρ _t1 of the inner gear (3). Can be equal to

If the clearance is ignored, the number of teeth of the inner gear (3) is Z _n1 , the tooth width of the inner gear (3) (length in the pump width direction) w, and one of the internal gear pump (1) having the above specifications. The average discharge amount V for the rotation is approximately V = wπ {(ρ _t1 ² −E ² Z _n1 ² ) + 2EZ _n1 (ρ _t1 + EZ _n1 ) sin (π / Z _n1 ) / (π / Z _n1 ) } / (Z _n1 +1). According to this formula, the main influence factors on the average discharge amount are the number of teeth Z _{n1 of} the inner gear (3), the tooth width (length in the pump width direction) w of the inner gear (3), the inner gear (3) The tip circle radius ρ _t1 and the eccentric amount E are obtained.

Pump outer diameter of the inscribed gear pump (1) is constant for the influence of the number of teeth Z _n1 and the eccentric amount E of the inner gear in a case where (dedendum radius of the outer gear (2) is constant) was (3), the eccentric The larger the amount E, the larger the discharge amount, and the smaller the number of teeth Z _n1 (because the eccentric amount E is large), the larger the discharge amount. In other words, increasing teeth is an effective means for increasing the discharge rate.
Although not shown in the drawings, the conventional trochoid pump has an outer gear tooth profile with an arc having a constant radius, and the inner gear tooth profile that meshes is an epitrochoid parallel curve. The epitrochoid curve can be expressed as a locus drawn by one point in the rolling circle that rolls on the basic circle. In the trochoid curve, when the eccentric amount is increased to increase the discharge amount, a cusp is generated. Therefore, when the teeth are increased, cusps are generated and appropriate meshing conditions (conditions where the tooth profile normal of the meshing points passes through the contact points of the pitch points, that is, the pitch circles) cannot be obtained. It was.

  In FIG. 2 in which the main part of FIG. 1 is enlarged, the teeth (4) of the outer gear (2) are meshed with the meshing side on the counterclockwise side and the clockwise direction on the basis of the tooth tips (4a) of the outer gear (2). It is asymmetrical with the non-meshing side.

  As for the curve forming the tooth profile of the outer gear (2), the meshing side is the first curve (11), the non-meshing side is the second curve (12), and the first curve (11) and the second curve (12 ) And the tooth tip (4a) are continuously connected.

  In this embodiment, the first curve (11) is part of an ellipse (first ellipse), and the second curve (12) is also part of an ellipse (second ellipse). The first curve (part of the first ellipse) (11) is a relatively gentle curve, while the second curve (part of the second ellipse) (12) is It is a relatively steep curve. The first curve (engagement side curve) (11) has a shape in which the curvature increases toward the tooth root (4b), and the second curve (non-engagement side curve) (12) The curvature decreases with going to the root (4c). The first curve (11) and the second curve (12) are connected by a circular arc (13) on the tooth root (4b) (4c) side.

  As shown in FIG. 3, the short radius of the first ellipse (14) forming the first curve (11) and the long radius of the second ellipse (15) forming the second curve (12) are as follows. Common line segment (16). In order to obtain such a tooth profile of the outer gear (2), the first ellipse (14) having a required shape is selected, and the short radius of the first ellipse (14) is set between the meshing side and the non-meshing side. A curve (11) on the meshing side of the outer gear (2) is formed by a part of the first ellipse (14) so as to be a line segment (16), and the meshing side and the non-meshing side are separated. A line segment (16), that is, a second ellipse (15) whose major radius is the minor radius of the first ellipse (14) is selected, and the curve (12) on the non-engagement side is selected as the second ellipse (15). It may be formed with a part of.

  The ellipse (14) (15) has a small curvature in the vicinity of the part forming the short radius (large curvature radius), and a large curvature in the vicinity of the part forming the long radius (the curvature radius is Small) and the curve gradually changes in curvature. Therefore, the first curve (11) is a relatively gentle curve with the curvature gradually increasing as the tooth root (4b), and the second curve (12) is gradually curved with the tooth root (4c). It becomes a relatively steep curve that becomes smaller.

  The inner gear (3) is created from the outer gear (2) in the same manner as before. As a result, as shown in FIG. 4, the inner gear (3) has an asymmetric shape between the counterclockwise meshing side and the clockwise meshing side, and the meshing side has a smooth curve. In the inner gear (3), between the convex curve (17) toward the radially inner side on the tooth root (5b) side and the convex curve (18) toward the radially outer side on the tooth tip (5a) side. Although the cusp (T) occurs at the point, the portion where the cusp (T) occurs is on the non-engagement side, and no adverse effect is caused by the cusp (T).

  In this manner, the trochoidal interference of cusp generation on the meshing side is avoided by gently relaxing the curve (11) of the meshing side tooth profile (decreasing the inclination).

  As an example of specific dimensions in the above embodiment, the radius of the outer gear (2) is 13.95 mm, the number of teeth is the inner gear (3) / outer gear (2) = 7/8, and the eccentricity E is 1.6 mm, long radius / short radius of the first ellipse (14) = 5.10 mm / 3.80 mm, long radius / short radius of the second ellipse (15) = 3.80 mm / 2.50 mm, both ellipses (14) The pitch circle radius at the center of (15) is 14.55 mm.

  In FIG. 1, the pitch circles (2p) and (3p) of both gears (2) and (3) are located near the center of the tooth height, but the pitch circles of both gears (2) and (3) are It may be positioned near the outermost diameter of the tooth height, or may be larger than the outermost diameter beyond the tooth height. Even when the pitch circles of both gears (2) and (3) are positioned near the outermost diameter of the tooth height, the locus of the meshing point (M) almost passes through the pitch point (P). The deviation from the meshing condition, that is, the rotational fluctuation is small.

  In the above, the ellipses (14) and (15) are examples of curves in which the curvature gradually changes, and the first and second curves (11) and (12) are curves in which the curvature gradually changes. It is not limited to the ellipse (14) (15).

  The curves (11) and (12) that form the tooth profile of the outer gear (2) are the ellipses (14) and (15), and the ellipse (14) that forms the meshing side and the ellipse that forms the non-meshing side (14). By matching the major radius of 15) (with a common line segment), it is possible to easily obtain a curve having an appropriate tooth profile in order to achieve higher teeth. For example, while maintaining the short radius of the first ellipse (14) (and hence the long radius of the second ellipse) (16) as well, the long radius of the first ellipse (14) and the second ellipse (15) By adjusting the ratio to the short radius, it is possible to prevent cusps from occurring on the meshing side of the inner gear (3). In the above example, the major radius of the first ellipse (14) / the minor radius of the second ellipse (15) = about 5.10 mm / 2.50 mm, which is about twice, for example, It can be appropriately changed within the range of 5.

(1): Internal gear pump, (2): Outer gear, (3): Inner gear, (4a): Tooth tip, (4b) (4c): Tooth base

Claims (2)

  An internal gear pump having an inner gear and an outer gear, wherein the tooth shape of the outer gear is formed asymmetrically on the meshing side and the non-meshing side, and the curve forming the tooth profile is a tooth on the meshing side. It is a relatively gentle curve where the curvature gradually increases as the original, and on the non-engagement side, it is a relatively steep curve where the curvature gradually decreases as the tooth roots, and the engagement side curve and the non-engagement side The internal gear pump is characterized in that the curve is continuously connected with the tooth tip.   In the curve forming the tooth profile, the meshing side and the non-meshing side are both formed by a part of an ellipse, and the short radius of the ellipse forming the meshing side and the long radius of the ellipse forming the non-meshing side are common. 2. The internal gear pump according to claim 1, wherein the internal gear pump is a line segment.

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