JP6343355B2 - Gear pump and manufacturing method thereof - Google Patents

Description

  The present disclosure relates to a gear pump including an inner rotor having a plurality of external teeth, and an outer rotor having a plurality of internal teeth and arranged to be eccentric with respect to the inner rotor, and a manufacturing method thereof.

  Conventionally, as a gear pump, one of the pump chambers defined by the external teeth of the external gear and the internal teeth of the internal gear communicates with a pump chamber (interdental chamber) whose volume is increased by the rotation of both gears. One having a suction port and two discharge ports communicating with a pump chamber whose volume is reduced by the rotation of both gears is known (for example, see Patent Document 1). This gear pump has a minimum clearance of 0.020 mm or more between the external teeth and the internal teeth located on the partition wall that divides the two discharge ports in a state where the external gear and the internal gear are pressed in opposite directions in the radial direction. And it is designed to be 0.110 mm or less.

Japanese Patent No. 5469875

  If the minimum gap between the external teeth and the internal teeth located on the partition wall that divides the two discharge ports is set as in the conventional gear pump, the pump chamber communicating with one discharge port on the high pressure side and the other on the low pressure side It would be possible to improve the volumetric efficiency of the pump by reducing the leakage of hydraulic oil to the pump chamber communicating with the discharge port. However, if the minimum clearance between the external teeth and the internal teeth located on the partition wall is reduced, cavitation occurs when fluid flows into the pump chamber communicating with the suction port, thereby reducing volumetric efficiency. There is a risk of noise or vibration.

  Accordingly, the main object of the present disclosure is to provide a gear pump capable of suppressing the occurrence of cavitation while improving volumetric efficiency, and a method for manufacturing the same.

  A gear pump of the present disclosure includes an inner rotor having a plurality of external teeth, an outer rotor having a plurality of internal teeth larger than the external teeth of the inner rotor and arranged to be eccentric with respect to the inner rotor, In the gear pump including a plurality of interdental chambers defined by two adjacent external teeth and two adjacent internal teeth, the teeth whose volume increases as the inner rotor and the outer rotor rotate. One suction port that communicates with the interchamber, and a first and a second that are partitioned by a partition wall and are independent of each other, and communicate with the interdental chamber that decreases in volume as the inner rotor and the outer rotor rotate. 2 discharge ports, communicating with the suction port and maximizing the amount of volume change when the inner rotor rotates by a unit angle. The minimum clearance between the external teeth and the internal teeth that define the interdental chamber is defined as a suction side clearance, and when the volume change amount per unit angle becomes maximum, the first and second discharge ports When the minimum clearance between the external teeth and the internal teeth defining the interdental space that at least partially overlaps the partition wall is defined as the discharge side clearance, the suction side clearance is more than the discharge side clearance. It is large.

  In this gear pump, the inner rotor communicates with the suction port and has a minimum clearance between the external teeth and the internal teeth that define the interdental space that maximizes the volume change when the inner rotor rotates by a unit angle. When the volume change amount per unit angle is maximized, the clearance is formed so as to be larger than the minimum clearance between the external teeth and the internal teeth that define the interdental chamber that at least partially overlaps the partition wall. Thus, taking into account the volume change of the interdental chamber communicating with the suction port, the volume is determined based on the minimum clearance between the external teeth and the internal teeth that define the interdental chamber that at least partially overlaps the partition wall. By forming the inner rotor so that the minimum value of the clearance in the interdental chamber where the amount of change is maximum is increased, the flow of fluid between the first and second discharge ports is regulated to improve volumetric efficiency. However, it is possible to suppress the occurrence of cavitation in the interdental chamber communicating with the suction port.

It is a schematic structure figure showing a gear pump of this indication. It is a schematic diagram which shows the creation procedure of the internal tooth of the outer rotor contained in the gear pump of this indication. It is a schematic block diagram which shows the external tooth of the inner rotor contained in the gear pump of this indication. It is a schematic diagram which shows the creation procedure of the external tooth of the inner rotor contained in the gear pump of this indication. It is a graph which illustrates the relationship between the rotation angle around the rotation center of an inner rotor, and the minimum value of the clearance of an external tooth and an internal tooth. It is a graph which illustrates the relationship between the rotation angle around the rotation center of an inner rotor, the volume of one interdental chamber, and the volume change rate. It is a schematic block diagram which illustrates the minimum value of the clearance between the external tooth and the internal tooth which defines the interdental chamber where the volume change rate becomes the maximum, and the minimum value of the clearance between the external tooth and the internal tooth which overlaps the partition wall.

  Next, embodiments for carrying out the invention of the present disclosure will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating a gear pump 1 according to an embodiment of the present disclosure. A gear pump 1 shown in the figure is configured as an oil pump mounted on a vehicle (not shown), for example, and sucks hydraulic oil (ATF) stored in an oil pan and pumps it to a hydraulic control device (both not shown). To do. The gear pump 1 is defined by, for example, a pump housing (both not shown) constituted by a pump body fixed to a transmission case of an automatic transmission and a pump cover fastened to the pump body, and the pump housing. An inner rotor (drive gear) 2 and an outer rotor (driven gear) 3 that are rotatably arranged in a gear housing chamber (not shown). The gear pump 1 may be configured as an in-vehicle pump (for example, an engine oil pump) other than an oil pump that pumps hydraulic oil for transmission, and may be applied to uses other than the in-vehicle pump.

  The inner rotor 2 is fixed to a rotating shaft 4 connected to a crankshaft (both not shown) of an engine mounted on the vehicle, and is rotated by power applied to the rotating shaft 4. A plurality of (for example, 11 teeth in this embodiment) external teeth 20 are formed on the outer periphery of the inner rotor 2. On the other hand, on the inner periphery of the outer rotor 3, the number of internal teeth 30 that is one more than the total number of external teeth 20 of the inner rotor 2 (for example, 12 teeth in this embodiment) is formed. The outer rotor 3 is rotatable in the gear housing chamber with a plurality of inner teeth 30 positioned on the lower side in FIG. 1 meshing with the corresponding outer teeth 20 of the inner rotor 2 and eccentric with respect to the inner rotor 2. Placed in. Further, a plurality of interdental chambers (pump chambers) 5 are formed between the inner rotor 2 and the outer rotor 3 by two adjacent external teeth 20 and two adjacent internal teeth 30.

  Thereby, when the inner rotor 2 is rotated in the direction of the thick arrow in FIG. 1 by the power from the rotating shaft 4, the outer rotor 3 has a part of the plurality of inner teeth 30 meshed with a part of the plurality of outer teeth 20. Thus, it rotates in the same direction together with the inner rotor 2 around the rotation center 3c that is separated from the rotation center 2c of the inner rotor 2 by the eccentric amount e. When the inner rotor 2 and the outer rotor 3 are rotated, in the rear region in the rotation direction of the both (see the thick arrow in FIG. 1), that is, mainly in the right half region in FIG. Thus, the volume of each interdental chamber 5 increases (interdental chamber 5 expands). Further, when the inner rotor 2 and the outer rotor 3 rotate, in the front region in the rotation direction of the inner rotor 2 or the like, that is, mainly the left half region in FIG. The volume of the chamber 5 decreases (the interdental chamber 5 contracts).

  Further, the pump housing (not shown) of the gear pump 1 increases in volume as the inner rotor 2 and the outer rotor 3 among the plurality of interdental chambers 5 defined by the external teeth 20 and the internal teeth 30 rotate. The volume decreases with the rotation of the suction port 6 extending in a substantially arc shape so as to communicate (oppose) with the interdental chamber 5 and the inner rotor 2 and the outer rotor 3 of the plurality of interdental chambers 5 respectively. A first discharge port 7 and a second discharge port 8 extending in a substantially arc shape so as to communicate (oppose) with the interdental chamber 5 are formed. As illustrated, the first and second discharge ports 7 and 8 are partitioned by a partition wall 9 and are independent of each other. In the present embodiment, the first discharge port 7 located on the rear side in the rotation direction of the inner rotor 2 or the like is a low pressure port, and the second discharge port 8 located on the front side in the rotation direction is a high pressure port.

  In addition, the 1st and 2nd discharge ports 7 and 8 may be connected to a mutually different oil path, and may be connected to a common oil path. The suction port 6, the first and second discharge ports 7, 8 may be formed on both sides (both the pump body and the pump cover) in the axial direction of the inner rotor 2 and the outer rotor 3, The outer rotor 3 may be formed on one side (one of the pump body and the pump cover) in the axial direction. Further, for example, the suction port 6 may be formed on one side in the axial direction of the inner rotor 2 or the like, and the first and second discharge ports 7 and 8 are formed on the other side in the axial direction of the inner rotor 2 or the like. Also good. Further, the first discharge port 7 may be formed on one side in the axial direction of the inner rotor 2 or the like, and the second discharge port 8 may be formed on the other side in the axial direction of the inner rotor 2 or the like.

  FIG. 2 is a schematic diagram showing a procedure for creating the inner teeth 30 of the outer rotor 3 included in the gear pump 1. As shown in the figure, the tooth profile (outline) of the outer rotor 3 defined by the plurality of inner teeth 30 is a diameter 2 · e + t with the rotation center 2c of the inner rotor 2 being the center of the rotation center 3c of the outer rotor 3. And a plurality of tooth profile lines (inner rotors) obtained by rotating the inner rotor 2 by the rotation angle δ / N when the rotation center 2c revolves by the predetermined angle δ. 2 contours (refer to the two-dot chain line in FIG. 3). However, “t” indicates that the rotation center 2 c of the inner rotor 2, the rotation center 3 c of the outer rotor 3, the top portion 21 t of the tooth tip portion 21 of the external tooth 20, and the top portion of the tooth tip portion of the internal tooth 30 are aligned. This is the clearance (tip clearance) between the top 21t and the top of the internal teeth 30, for example, about 0.03 to 0.07 mm. As a result, it is possible to easily obtain the outer rotor 3 that can mesh properly with the inner rotor 2. However, the tooth profile (outline) of the outer rotor 3 may be the envelope itself or may be determined to be located outside the envelope. The inner teeth of the outer rotor 3 may be created using a gear cutting tool having substantially the same shape as the inner rotor 2.

  FIG. 3 is a schematic configuration diagram showing the external teeth 20 of the inner rotor 2, and FIG. 4 is a schematic diagram showing a procedure for creating the external teeth 20. As shown in these drawings, each external tooth 20 of the inner rotor 2 includes a convexly curved tooth tip portion 21, a concave curved tooth bottom portion 22, and the rotational direction of the inner rotor 2 relative to the tooth tip portion 21 ( The first intermediate portion 23 located between the tooth tip portion 21 and the tooth bottom portion 22 on the front side in the thick arrow in FIG. 3, and the tooth on the rear side in the rotational direction of the inner rotor 2 relative to the tooth tip portion 21. A second intermediate portion 24 located between the tip portion 21 and the tooth bottom portion 22 is included. As shown in the drawing, the external teeth 20 are formed asymmetrically with respect to a tooth profile center line Lc passing through the top portion 21t located on the outermost radial direction of the tooth tip portion 21 and the rotation center 2c of the inner rotor 2.

  As shown in FIG. 4, the tooth tip portion 21 has a trochoidal coefficient obtained by dividing the radius rde of the first drawing point by the radius re of the abduction circle Co, which is larger than 1 (for example, about 1.2). Value) A convex curved surface is formed by an epitrochoid curve. The epitrochoid curve forming the tooth tip portion 21 maintains the radius rde of the first drawing point at the first value Rde (constant value) and has an abduction circle Co having a radius re smaller than the first value Rde. Is rolled without slipping while circumscribing the base circle BCt having the rotation center 2c of the inner rotor 2 and the center O in common.

  The tooth bottom portion 22 is formed in a concave curved surface by a hypotrochoidal curve having a trochoidal coefficient larger than 1 obtained by dividing the radius rdh of the second drawing point by the radius rh of the inversion circle Ci. The hypotrochoid curve forming the tooth bottom portion 22 is the same as the epitrochoid curve forming the tooth tip portion 21 and the basic circle BCt. As shown in FIG. 4, the radius rdh of the second drawing point is set to the first value. It is obtained by rolling an inversion circle Ci having a radius Rh smaller than the second value Rdh while keeping the value Rdh (constant value) 2 without slipping while inscribed in the basic circle BCt.

  Further, the tooth bottom portion 22 is a front side in the rotational direction from the tooth profile center line Lc by a half (φ / 2) of an angle φ (360 ° / the number of teeth of the external teeth 20) corresponding to one tooth of the external teeth 20. Alternatively, the first tooth bottom portion 22a located on the front side in the rotation direction of the inner rotor 2 with respect to the tooth tip portion 21 and the tooth tip portion 21 with respect to the intersection portion 22x with the line segment Le rotated rearward. It is divided into a second tooth bottom portion 22b located on the rear side in the rotation direction of the inner rotor 2. In the inner rotor 2, as shown in FIGS. 3 and 4, a range between the two intersecting portions 22 x sandwiching the tooth profile center line Lc is a range corresponding to one tooth of the external teeth 20. As shown in FIGS. 3 and 4, the second tooth bottom portion 22 b is continuous with the rear first tooth bottom portion 22 a in the rotation direction of the inner rotor 2.

  In the present embodiment, the radius rde of the first drawing point for drawing the epitrochoid curve forming the tooth tip portion 21, that is, the first value Rde, and the hypotrochoid curve forming the tooth bottom portion 22 are drawn. For this reason, the radius rdh of the second drawing point, that is, the second value Rdh is set to the same value Rd. Similarly, the radius re of the abduction circle Co and the radius rh of the inversion circle Ci are set to the same value R. Therefore, in the inner rotor 2, the relationship Rde = Rdh = Rd, re = rh = R, and tooth height = Rde + re + Rdh + rh = 2 · e is established.

  As shown in FIGS. 3 and 4, the first intermediate portion 23 is formed between the tooth tip portion 21 and the first tooth bottom portion 22 a of the tooth bottom portion 22, and is located on the tooth tip portion 21 side. And an inner intermediate portion 23i located on the first tooth bottom portion 22a side. In the present embodiment, the outer intermediate portion 23o is such that the tangent at the front end 21f in the rotational direction of the inner rotor 2 of the tooth tip portion 21 is the same as the tangent of the epitrochoidal curve at the end 21f. It is formed by a defined involute curve. Thereby, the tip part 21 and the outer side intermediate part 23o can be smoothly continued in the edge part 21f. Further, the inner intermediate portion 23i is smoothly continuous with the first tooth bottom portion 22a at the rear end portion 22r in the rotation direction of the inner rotor 2 of the first tooth bottom portion 22a and is a boundary portion 23x with the outer intermediate portion 23o. The outer intermediate portion 23o is formed by a smooth curve (for example, an arc) that is smoothly continuous. As shown in the drawing, the curve forming the inner intermediate portion 23i may be selected to be as short as possible than the involute curve forming the outer intermediate portion 23o.

  The first intermediate portion 23 is formed by an involute curve (see Japanese Patent Application Laid-Open No. 2014-181620) obtained by using a basic circle having the center O in common with the basic circle BCt of the epitrochoid curve and the hypotrochoid curve. May be. In this case, the diameter of the base circle of the involute curve forming the first intermediate portion 23 is “Rbi”, and the diameter of the base circle BCt of the epitrochoid curve forming the tooth tip portion 21 and the hypotrochoid curve forming the tooth bottom portion 22 is set. Is set to “Rbt”, the diameters Rbt and Rbi may be selected so as to satisfy the relationship Rbi ≦ Rbt. In this case, the first intermediate portion 23 may include a relay surface formed by a smooth curve (for example, an arc) on the inner side (front side) and the outer side (rear side) of the portion formed by the involute curve.

  As shown in FIGS. 3 and 4, the second intermediate portion 24 is formed between the tooth tip portion 21 and the second tooth bottom portion 22 b of the tooth bottom portion 22, and has teeth more than the intersection portion 24 x with the basic circle BCt. The outer intermediate part 24o located in the front part 21 side and the inner intermediate part 24i located in the 2nd tooth bottom part 22b side rather than the cross | intersection part 24x are included. In the present embodiment, the range from the outer intermediate portion 24o, that is, the intersecting portion 24x to the rear end portion (boundary) 21r in the rotation direction of the inner rotor 2 of the tooth tip portion 21, as shown in FIG. It is formed by a first curve obtained by rolling an outer rotation circle Co circumscribing the base circle BCt without slipping while changing the radius of one drawing point (see the dotted line in the figure). Further, the range from the inner intermediate portion 24i, that is, the intersecting portion 24x to the front end portion (boundary) 22f in the rotation direction of the inner rotor 2 of the second tooth bottom portion 22b is the second drawing point as shown in FIG. Is formed by a second curve obtained by rolling the inversion circle Ci inscribed in the base circle BCt without slipping while changing the radius (see the two-dot chain line in the figure). For the procedure for changing the radius of the first or second drawing point of the abduction circle Co or the inversion circle Ci, refer to Japanese Patent Application Laid-Open No. 2014-181619.

  Here, in the gear pump 1 having the first and second discharge ports 7 and 8, in order to improve the volumetric efficiency by regulating the flow of the hydraulic oil between the first and second discharge ports 7 and 8, the gear pump 1 It is necessary to make the minimum value of the clearance between the external teeth 20 and the internal teeth 30 overlapping the partition wall 9 as small as possible from the axial direction of 1 as much as possible. On the other hand, with respect to the interdental chamber 5 communicating with the suction port 6, from the viewpoint of suppressing the occurrence of cavitation associated with the inflow (suction) of hydraulic oil from the suction port 6, the external teeth 20 and the internal teeth 30 It is necessary to increase the minimum value of the clearance to allow the hydraulic oil to flow between the interdental chambers 5 adjacent to each other, thereby reducing the flow velocity of the hydraulic oil flowing from the suction port 6. Therefore, the inventors have determined the minimum clearance between the external teeth 20 and the internal teeth 30 between the first and second discharge ports 7 and 8 and the clearance between the external teeth 20 and the internal teeth 30 on the suction port 6 side. We conducted intensive research to optimize the minimum value. As a result, the present inventors have found that the amount of change in the volume V of the interdental chamber 5 communicating with the suction port 6 when the inner rotor 2 rotates by a unit angle (volume change amount per unit angle, hereinafter referred to as “volume change”). It has come to focus on "rate ΔV").

  That is, in the interdental chamber 5 that communicates with the suction port 6 and has the maximum volume change rate ΔV, the internal pressure greatly decreases when the volume change rate ΔV becomes the maximum, and from the suction port 6 due to the decrease in the internal pressure. Cavitation tends to occur when hydraulic fluid flows at a high flow rate. The minimum value of the clearance between the external teeth 20 and the internal teeth 30 that define the interdental chamber 5 that communicates with the intake port 6 and has the maximum volume change rate ΔV (hereinafter referred to as “intake side clearance” as appropriate). The smaller the amount, the lower the amount of pressure in the interdental chamber 5 (negative pressure) becomes larger when the volume change rate ΔV becomes maximum.

  Based on this, the plurality of external teeth 20 of the inner rotor 2 are in the ideal center state, and the minimum clearance (the clearance between the external teeth 20 and the internal teeth 30 that overlap the partition wall 9 when the volume change rate ΔV amount becomes maximum ( In the following description, the suction side clearance is appropriately asymmetrical with respect to the tooth profile center line Lc so as to be larger than the “discharge side clearance”. In the “ideal center state”, the rotation center c of the inner rotor 2 coincides with the rotation center of the rotation shaft 4 fixed to the inner rotor 2, and the rotation center c of the outer rotor 3 and the outer rotor 3 are accommodated. The state where the center of the gear housing chamber matches.

  In order to make the suction side clearance larger than the discharge side clearance, the length of the curve forming the first intermediate portion 23, that is, the length from the end portion 21f of the tooth tip portion 21 to the end portion 22r of the first tooth bottom portion 22a. The length is determined to be longer than the length of the curve forming the second intermediate portion 24, that is, the length from the end portion 21r of the tooth tip portion 21 to the end portion 22f of the second tooth bottom portion 22b. Furthermore, the length of the hypotrochoid curve forming the first tooth bottom portion 22a, that is, the length from the end 22r of the first tooth bottom portion 22a to the intersecting portion 22x is the length of the hypotrochoid curve forming the second tooth bottom portion 22b. That is, it is determined to be shorter than the length from the end portion 22f of the second tooth bottom portion 22b to the intersecting portion 22x. Thus, the length of the curve forming the first intermediate portion 23 is made longer than the length of the curve forming the second intermediate portion 24, and the length of the hypotrochoid curve forming the first tooth bottom portion 22a is set to the first length. By making it shorter than the length of the hypotrochoid curve forming the two tooth bottom portions 22b, the end portion 21r on the rear side in the rotational direction of the epitrochoid curve forming the tooth tip portion 21 is made the second tooth bottom portion as shown in FIG. 22b, and the end portion 21f on the front side in the rotational direction of the epitrochoid curve can be moved outward in the radial direction of the inner rotor 2.

  And the interdental chamber 5 connected to the 1st and 2nd discharge ports 7 and 8 by making the end part 21r on the back side in the rotation direction of the epitrochoid curve forming the tooth tip part 21 closer to the second tooth bottom part 22b. The minimum value of the clearance between the outer teeth 20 and the inner teeth 30 that define the above can be reduced as a whole. The outer teeth defining the interdental chamber 5 communicating with the suction port 6 by bringing the end portion 21f on the front side in the rotational direction of the epitrochoid curve forming the tooth tip portion 21 to the outside in the radial direction of the inner rotor 2 The minimum clearance between the teeth 20 and the internal teeth 30 can be increased as a whole. As a result, it is possible to improve the degree of freedom in determining the position of the partition wall 9 that partitions the first and second discharge ports 7, 8, that is, the distribution ratio of the discharge flow rate from the first and second discharge ports 7, 8. The minimum clearance (discharge-side clearance) between the external teeth 20 and the internal teeth 30 that overlap with each other is made smaller, and the minimum clearance (suction-side clearance) in the interdental chamber 5 where the volume change ΔV is maximum is sufficient. Therefore, the occurrence of cavitation in the interdental chamber 5 can be satisfactorily suppressed.

  In the gear pump 1, when the inner rotor 2 and the outer rotor 3 are rotated in an eccentric state from the ideal center state, the interdental chamber 5 that has reached the top dead center is positioned on the rear side in the rotation direction of the inner rotor 2. While any one external tooth 20 is in contact with the corresponding internal tooth 30, the external tooth 20 located on the one rear side in the rotation direction of the inner rotor 2 is located with respect to any one external tooth 20. A plurality of external teeth 20 of the inner rotor 2 are formed so as to contact the corresponding internal teeth 30. That is, the position where the tooth tip apex 21t of the external tooth 20 and the tooth top apex of the internal tooth 30 face each other in a straight line through the top dead center (refer to the position between the suction port 6 and the first discharge port 7 in FIG. 7). While one of the outer teeth 20 closest to () is in contact with the corresponding inner tooth 30, the outer teeth 30 are positioned one rear side in the rotational direction of the inner rotor 2 with respect to any one of the outer teeth 30. The external teeth 20 come into contact with the corresponding internal teeth 30. By defining the specifications of the tooth tip portion 21, the first and second tooth bottom portions 22 a and 22 b, and the first and second intermediate portions 23 and 24 so as to satisfy such conditions, the inner rotor 2 during operation of the gear pump 1 and It is possible to stabilize the behavior of the outer rotor 3 and reduce vibration and noise. The “top dead center” is a position where the volume of the interdental chamber 5 that increases with the rotation of the inner rotor 2 or the like is maximized (position between the suction port 6 and the first discharge port 7 in FIG. 1). Say. In addition, the “decentered state from the ideal center state” means a deviation between the rotation center c of the inner rotor 2 and the rotation center of the rotation shaft 4 and a deviation between the rotation center c of the outer rotor 3 and the center of the gear housing chamber. A state in which at least one of them has occurred.

  FIG. 5 illustrates the relationship between the rotation angle θ around the rotation center 2 c of the inner rotor 2 in the gear pump 1 and the minimum value of the clearance between the outer teeth 20 and the inner teeth 30, and FIG. 6 illustrates the rotation center of the inner rotor 2. The relationship between the rotation angle θ around 2c and the volume V and volume change rate ΔV of one interdental chamber 5 is illustrated.

  5 and 6, the diameter of the root circle of the inner rotor 2 is, for example, in the range of 20 to 80 mm, the diameter of the root circle of the outer rotor is in the range of, for example, 25 to 110 mm, and the eccentricity e is, for example, 1.05 to 5 The analysis results for the gear pump 1 in which the range is 0.000 mm, Rde = Rdh = Rd is selected from the range of 0.55 to 3.00 mm, and re = rh = R is selected from the range of 0.5 to 2.0 mm, for example. It is shown. The minimum value of the clearance between the external teeth 20 and the internal teeth 30 is measured in the direction of the normal to the tooth surfaces of the external teeth 20 and the internal teeth 30 that are closest to each other as shown in FIG. It is an interval. Further, the rotation angle θ around the rotation center 2c of the inner rotor 2 is a rotation angle around the rotation center 2c of the line portion connecting the bottommost portion (deepest portion) of the tooth bottom portion 22 of the external tooth 20 and the rotation center 2c. 7 is measured counterclockwise in FIG. 7 when the state where the bottom of the bottom 22 of the external tooth 20 is located directly below the center of rotation 2c of the inner rotor 2 is 0 °. Further, a range A in FIG. 5 indicates a range in which the bottom part of the bottom part 22 of the external tooth 20 overlaps the partition wall 9. Further, the volume V shown in FIG. 6 is an interdental space defined by two external teeth 20 that are adjacent to each other with a tooth bottom portion 22 that is a measurement target of the rotation angle θ and two internal teeth 30 corresponding thereto. The volume of the chamber 5. Furthermore, the volume change rate ΔV shown in FIG. 6 is a change amount of the volume V when the rotation angle θ changes (increases) by, for example, 5 °.

  From the analysis result shown in FIG. 5, in the gear pump 1, the minimum value of the clearance between the external teeth 20 and the internal teeth 30 that define the interdental chamber 5 that communicates with the first and second discharge ports 7 and 8 is reduced as a whole. In addition, it will be understood that the minimum clearance between the external teeth 20 and the internal teeth 30 defining the interdental chamber 5 communicating with the suction port 6 can be increased as a whole. Further, in the gear pump 1 having the above specifications, as shown in FIG. 6, when the rotational angle θ of the inner rotor 2 changes from 90 ° to 95 °, the volume change rate of the interdental chamber 5m shown in FIG. The smallest value CLi of the clearance between the external teeth 20i and the internal teeth 30i shown in FIG. 7 is the smaller of the clearances CLi and CLi ′ of the external teeth 20 and 30 that define the interdental chamber 5m. The suction side clearance. Further, when the volume change rate ΔV of the interdental chamber 5m is maximized, the minimum clearance CLd between the external teeth 20d and the internal teeth 30d overlapping the partition wall 9 is the discharge side clearance. As shown in FIG. 5, the minimum clearance CLi (suction side clearance) between the external teeth 20i and the internal teeth 30i is the minimum clearance CLd between the external teeth 20d and the internal teeth 30d overlapping the partition wall 9 (FIG. 5). 5), which is about 9 to 10 times larger. From this analysis result, in the gear pump 1, in the interdental chamber 5 where the minimum clearance (discharge-side clearance) between the external teeth 20 and the internal teeth 30 overlapping the partition wall 9 is made smaller and the volume change ΔV is maximum. It will be understood that the minimum value of the clearance (suction side clearance) can be sufficiently increased to satisfactorily suppress the occurrence of cavitation in the interdental chamber 5.

  The minimum clearance shown in FIG. 5 is a design value (analysis value) in an ideal center state, and the minimum clearance between the external teeth 20 and the internal teeth 30 in the gear pump 1 as a product is a manufacturing tolerance or the like. Varies depending on In this regard, according to experiments and analysis by the present inventors, if the suction side clearance (CLi) in the product is at least three times or more than the discharge side clearance (CLd), the external teeth 20 overlapping the partition wall 9 are obtained. It has been confirmed that the minimum value of the clearance in the interdental chamber 5 where the volume change rate ΔV is maximized can be made sufficiently large in practice, while the minimum value of the clearance between the teeth 30 and the internal teeth 30 is sufficiently small in practice. Yes. Then, while any one of the external teeth 20 closest to the top dead center is in contact with the corresponding internal tooth 30, the gear pump 1 is one rear side in the rotational direction of any one of the external teeth 20. The external teeth 20 positioned in the inner rotor 2 are configured to come into contact with the corresponding internal teeth 30. By designing the plurality of external teeth 20 of the inner rotor 2 so as to satisfy such conditions, the suction side clearance (CLi) is set. The upper limit of will be determined.

  Further, in the gear pump 1, when the volume change rate ΔV of the interdental chamber 5m shown in FIG. 7 is maximized, the pair of external teeth 20d and internal teeth 30d overlap with the partition wall 9. Therefore, the external teeth 20d and internal teeth The minimum clearance CLd with respect to 30d is set as the discharge-side clearance, but is not necessarily limited thereto. That is, the gear pump 1 may be configured such that the two sets of external teeth 20 and internal teeth 30 overlap the partition wall 9 when the volume change rate ΔV of the interdental chamber 5m is maximized. Of the minimum clearances of the outer teeth 20 and the inner teeth 30 in the set, the smaller one may be used as the discharge side clearance. In other words, the discharge-side clearance is defined by the external teeth 20 and the internal teeth that define the interdental chamber 5 that at least partially overlaps the partition wall between the first and second discharge ports 7 and 8 when the volume change rate ΔV becomes maximum. The minimum clearance with the teeth 30 may be set.

  Furthermore, when the inner rotor 2 and the outer rotor 3 are rotating in an eccentric state from the ideal center state, any one of the external teeth 20 closest to the top dead center is in contact with the corresponding internal tooth 30. In addition, in order to bring the external tooth 20 positioned one rear side in the rotational direction from any one of the external teeth 20 into contact with the corresponding internal tooth 30, the external tooth 30 at the top dead center in the ideal rotation state. The tip clearance CLx (see FIG. 7) between the outer teeth 30 and the inner teeth 20 is set to the driving tooth surface of the outer teeth 30 located one rear side in the rotational direction with respect to the outer teeth 30 on the top dead center and the corresponding inner teeth 30. It is preferable that the clearance with the driven tooth surface be equal to or greater than the minimum value CLy (see FIG. 7) in the ideal center state. Further, the tip clearance CLx between the outer teeth 30 and the inner teeth 20 at the top dead center in the ideal center state is preferably set to 200 μm or less. As a result, the discharge-side clearance is prevented from becoming large, and the leakage of hydraulic oil from the first discharge port 7 to the second discharge port 8 can be restricted to improve the volumetric efficiency. The lower limit value of the tip clearance CLx in the ideal center state may be set to 5 μm or more in consideration of manufacturing tolerances.

  As described above, in the gear pump 1, the volume change based on the minimum clearance between the external teeth 20 and the internal teeth 30 that overlap the partition wall 9 in consideration of the volume change of the interdental chamber 5 communicating with the suction port 6. Each external tooth 20 of the inner rotor 2 is asymmetrical so that the minimum value of the clearance in the interdental chamber 5 where the rate ΔV is maximum is increased. Thus, the flow of hydraulic oil between the first and second discharge ports 7 and 8 is restricted to improve the volumetric efficiency, and the occurrence of cavitation in the interdental chamber 5 communicating with the suction port 6 is suppressed. It becomes possible.

  Further, in the gear pump 1, the tooth tip portion 21 of each external tooth 20 of the inner rotor 2 is formed by a portion other than the loop portion of the epitrochoid curve having a trochoid coefficient larger than 1, and the tooth bottom portion 22 is formed by the epitrochoid. The curve and the base circle BCt are made common and formed by a portion other than the hypotrochoid curve loop in which the trochoid coefficient is larger than 1. As a result, the radii rde, rdh of the first and second drawing points, that is, the first and second radii are maintained while keeping the radii re, rh (radius / number of teeth of the heel base circle BCt) of the abduction circle Co and the inversion circle Ci. By increasing the second values Rde and Rdh, the shape of the tooth tip portion 21 and the tooth bottom portion 22 is determined using one basic circle BCt, and the outer diameter of the basic circle BCt, that is, the outer diameter of the inner rotor 2 is reduced. It is possible to easily increase the tooth height while maintaining it.

  Furthermore, in the gear pump 1, the 1st intermediate part 23 located in the front side in the rotation direction of the inner rotor 2 of the tooth tip part 21 is formed of an involute curve. As a result, the outer teeth 20 of the inner rotor 2 and the inner teeth 30 of the outer rotor 3 can be meshed more smoothly and the rotational speed ratio between the inner rotor 2 and the outer rotor 3 can be made constant. However, the first intermediate unit 23 is an involute curve such as an n-order function (where “n” is an integer of 1 or more), an arc, an arbitrary polynomial, a trigonometric function, a relaxation curve, and a combination thereof. Needless to say, it may be formed by other curves.

  Further, in the gear pump 1, the range from the intersection 24x with the basic circle BCt of the second intermediate portion 24 to the end 21r of the tooth tip 21 changes to the basic circle BCt while changing the radius of the drawing point of the abduction circle Co. It is formed by a first curve obtained by rolling the circumscribed circle Co that circumscribes it without slipping. Further, the range from the intersection 24x of the second intermediate portion 24 with the basic circle BCt to the end 22f of the second tooth bottom portion 22b is inscribed in the basic circle BCt while changing the radius of the drawing point of the inversion circle Ci. It is formed by a second curve obtained by rolling the inward circle Ci without slipping. Accordingly, the second intermediate portion smoothly connecting the tooth tip portion 21 and the second tooth bottom portion 22b while bringing the rear end portion 21r of the tooth tip portion 21 in the rotation direction of the inner rotor as close as possible to the second tooth bottom portion 22b. The part 24 can be configured. However, the second intermediate portion 24 is also an involute curve such as an n-order function (where “n” is an integer equal to or greater than 1), an arc, an arbitrary polynomial, a trigonometric function, a relaxation curve, and a combination thereof. Needless to say, it may be formed by other curves.

  As described above, the gear pump according to the present disclosure has an inner rotor having a plurality of external teeth, a plurality of internal teeth that are larger than the external teeth of the inner rotor, and is arranged to be eccentric with respect to the inner rotor. And a plurality of interdental chambers defined by the two adjacent external teeth and the two adjacent internal teeth, with the rotation of the inner rotor and the outer rotor. One suction port that communicates with the interdental chamber that increases in volume, and the interdental chamber that is partitioned by a partition wall and independent from each other, and the volume decreases as the inner rotor and the outer rotor rotate. A first discharge port and a second discharge port that communicate with each other, communicate with the suction port, and rotate when the inner rotor rotates by a unit angle; The minimum clearance between the external teeth and the internal teeth defining the interdental chamber that maximizes the product change amount is defined as a suction side clearance, and the volume change amount per unit angle is maximized. The suction side clearance when the minimum clearance between the external teeth and the internal teeth that define an interdental chamber that at least partially overlaps the partition wall between the first and second discharge ports is the discharge side clearance. Is larger than the discharge-side clearance.

  This gear pump has one suction port and first and second discharge ports that are partitioned by a partition wall and independent from each other. In such a gear pump, the flow of fluid between the first and second discharge ports is reduced by further reducing the minimum clearance between the external teeth and the internal teeth that overlap the partition between the first and second discharge ports. Can be controlled to improve volumetric efficiency. On the other hand, with regard to the interdental chamber communicating with the suction port, the minimum clearance between the external teeth and the internal teeth is reduced from the viewpoint of suppressing the occurrence of cavitation due to the inflow (suction) of fluid from the suction port. It needs to be bigger. In particular, in the interdental chamber that communicates with the suction port and has the maximum volume change when the inner rotor rotates by a unit angle, the internal pressure greatly decreases when the volume change per unit angle becomes maximum. Cavitation is likely to occur due to the flow of fluid from the suction port at a high flow rate due to the decrease in the pressure. The minimum clearance between the external teeth and the internal teeth that define the interdental space that maximizes the volume change amount when the inner rotor rotates by a unit angle while communicating with the suction port, that is, the suction side clearance is small. As the amount of decrease in the pressure in the interdental chamber (negative pressure) increases, the volume change amount per unit angle becomes maximum. Based on this, the inner rotor of this gear pump has an external tooth and an internal tooth that define an interdental space that at least partially overlaps the partition wall when the suction side clearance has a maximum volume change per unit angle. The clearance is formed to be larger than the minimum value, that is, the discharge-side clearance. Thus, taking into account the volume change of the interdental chamber communicating with the suction port, the volume is determined based on the minimum clearance between the external teeth and the internal teeth that define the interdental chamber that at least partially overlaps the partition wall. By forming the inner rotor so that the minimum value of the clearance in the interdental chamber where the amount of change is maximum is increased, the flow of fluid between the first and second discharge ports is regulated to improve volumetric efficiency. However, it is possible to suppress the occurrence of cavitation in the interdental chamber communicating with the suction port.

  The plurality of external teeth may be formed asymmetrically with respect to the tooth profile center line. Thereby, the suction side clearance can be easily made larger than the discharge side clearance. The tooth profile center line may be a straight line connecting the top of the tooth tip and the rotation center of the inner rotor.

  Furthermore, the suction side clearance may be at least three times the discharge side clearance. Thus, if the external teeth are formed asymmetrically with respect to the tooth profile center line so that the suction side clearance is three times or more of the discharge side clearance, the minimum clearance between the external teeth and the internal teeth overlapping the partition wall can be reduced. The minimum value of the clearance in the interdental chamber where the volume change amount is maximized can be made sufficiently large in practice while being sufficiently small in practice. Thereby, it becomes possible to satisfactorily suppress the occurrence of cavitation in the interdental chamber communicating with the suction port while further improving the volumetric efficiency.

  Further, when the inner rotor and the outer rotor are rotating, any one of the external teeth closest to a position where the tooth tops of the external teeth and the tooth tops of the internal teeth face each other on a straight line While one of the external teeth is in contact with the corresponding internal tooth, the external tooth positioned one rearward in the rotational direction of the inner rotor is in contact with the corresponding internal tooth. May be. As a result, it is possible to stabilize the behavior of the inner rotor and the outer rotor during operation of the gear pump and reduce vibration and noise.

  Furthermore, the tip clearance between the external teeth and the internal teeth when any one of the external teeth and the corresponding tooth tops of the internal teeth are positioned in a straight line is greater than that of any one of the external teeth. Alternatively, the clearance may be equal to or greater than the minimum value of the clearance between the driving tooth surface of the external tooth positioned on the rear side in the rotation direction of the inner rotor and the driven tooth surface of the internal tooth corresponding thereto. As a result, when the inner rotor and the outer rotor rotate, any one of the outer teeth closest to the position where the tooth tops of the external teeth and the tooth tops of the internal teeth face each other in a straight line corresponds to the corresponding internal teeth. While in contact, it is possible to bring the external tooth located one more rear side in the rotational direction than any one of the external teeth into contact with the corresponding internal tooth.

  Further, the tip clearance between any one of the external teeth and the corresponding internal teeth may be 200 μm or less. Thereby, it is possible to suppress the increase in the discharge-side clearance and to regulate the fluid flow between the first and second discharge ports and to improve the volume efficiency.

  Further, each of the outer teeth of the inner rotor is a tooth tip formed by an epitrochoid curve obtained by rolling an outer rotation circle having a radius smaller than the drawing point radius without slipping while circumscribing the base circle. And a hypotrochoid curve obtained by rolling an inversion circle having a radius smaller than the radius of the drawing point without slipping while inscribed in the basic circle common to the epitrochoid curve, and A first tooth bottom portion located on the front side in the rotation direction of the inner rotor with respect to the tooth tip portion, and a hypotrochoid curve obtained by rolling the inner rotation circle without slipping while inscribed in the basic circle. And a second tooth bottom portion continuous to the first tooth bottom portion on the rear side in the rotation direction, and an arbitrary curve, and the tooth tip portion and the first tooth bottom portion. A first intermediate portion positioned between the first tip portion and the second intermediate portion formed between the tooth tip portion and the second tooth bottom portion. The length of the curve forming the part may be longer than the length of the curve forming the second intermediate part.

  By configuring the outer teeth of the inner rotor in this way, the minimum value of the clearance between the external teeth and the internal teeth that overlap the partition wall is made smaller, while the minimum clearance value in the interdental chamber that maximizes the volume change amount is reduced. It becomes possible to make it larger. That is, by making the length of the curve forming the first intermediate portion longer than the length of the curve forming the second intermediate portion, the end portion on the rear side in the rotation direction of the epitrochoid curve forming the tooth tip portion is The two tooth bottoms can be brought closer to each other, and the end portion on the front side in the rotational direction of the epitrochoid curve can be moved outward in the radial direction of the inner rotor. Then, by bringing the end portion on the rear side in the rotation direction of the epitrochoid curve forming the tooth tip portion closer to the second tooth bottom portion, external teeth defining an interdental chamber communicating with the first and second discharge ports; The minimum value of clearance with the internal teeth can be reduced overall. In addition, by bringing the end portion of the epitrochoid curve forming the tooth tip portion on the front side in the rotational direction toward the outside in the radial direction of the inner rotor, the outer teeth and the inner teeth that define the interdental chamber communicating with the suction port The minimum clearance can be increased overall. As a result, while improving the degree of freedom in determining the position of the partition wall that partitions the first and second discharge ports, that is, the distribution ratio of the discharge flow rate from the first and second discharge ports, the external teeth and internal teeth that overlap the partition wall It is possible to reduce the cavitation in the interdental chamber satisfactorily by making the minimum clearance value smaller and sufficiently increasing the minimum clearance value in the interdental chamber where the volume change is maximum. Become. In addition, one basic circle is used by increasing the radius of the epitrochoid curve and hypotrochoid curve while keeping the radius of the abduction circle and adduction circle (the radius of the basic circle / the number of teeth) small. Thus, the shape of the tip portion and the bottom portion of the tooth can be determined, and the tooth height of the outer teeth can be easily increased while keeping the outer diameter of the basic circle, that is, the outer diameter of the inner rotor, small.

  The first intermediate part may be formed by at least an involute curve. As a result, the external teeth and the internal teeth can be meshed more smoothly, and the rotational speed ratio between the inner rotor and the outer rotor can be made constant.

  Further, the range from the intersection of the second intermediate portion with the basic circle to the boundary with the tooth tip portion is the outer circumference circumscribing the basic circle while changing the radius of the drawing point of the abduction circle. It may be formed by a first curve obtained by rolling a rolling circle without slipping, and the range from the intersection of the second intermediate part with the basic circle to the boundary with the second tooth bottom is It may be formed by a second curve obtained by rolling the inversion circle inscribed in the basic circle without slipping while changing the radius of the drawing point of the inversion circle. Accordingly, the second intermediate portion that smoothly connects the tooth tip portion and the second tooth bottom portion while making the rear end portion of the tooth tip portion in the rotation direction of the inner rotor as close as possible to the second tooth bottom portion is configured. Is possible.

  Further, the tooth profile of the outer rotor defined by the plurality of inner teeth has an eccentricity amount of the rotation center of the outer rotor with respect to the rotation center of the inner rotor as “e”, and the rotation center of the inner rotor and the outer rotor Clearance between the tooth tip of the external tooth and the tooth tip of the internal tooth when the rotation center of the rotor, the top of the tooth tip of the external tooth and the top of the tooth tip of the internal tooth are positioned on a straight line Is set to “t”, the rotation center of the inner rotor is revolved by a predetermined angle on the circumference of the diameter 2 · e + t centering on the rotation center of the outer rotor, and the rotation center of the inner rotor is A package drawn for a plurality of tooth profile lines obtained by rotating the inner rotor by the predetermined angle and the rotation angle corresponding to the number of teeth of the inner rotor when revolving by an angle. It may be determined based on the line. This makes it possible to easily obtain an outer rotor that can be properly meshed with the inner rotor as described above.

  A manufacturing method of a gear pump according to the present disclosure includes an inner rotor having a plurality of external teeth, and an outer rotor having a plurality of inner teeth larger than the outer teeth of the inner rotor and arranged eccentric to the inner rotor. A plurality of interdental chambers defined by the rotor, the two adjacent external teeth and the two adjacent internal teeth, and the interdental space whose volume increases as the inner rotor and the outer rotor rotate. A suction port that communicates with the chamber, and a first and a second that are partitioned by a partition wall and are independent of each other, and communicate with the interdental chamber that decreases in volume as the inner rotor and the outer rotor rotate. A method for manufacturing a gear pump having a discharge port, the volume when communicating with the suction port and rotating the inner rotor by a unit angle The minimum clearance between the external teeth and the internal teeth defining the interdental chamber that maximizes the amount of conversion is defined as the suction side clearance, and the first volume change when the volume change amount per unit angle is maximum. When the minimum clearance between the external teeth and the internal teeth defining the interdental chamber at least partially overlapping the partition wall between the second discharge ports is the discharge side clearance, the suction side clearance is A step of forming the inner rotor so as to be larger than the discharge-side clearance;

  In the gear pump manufactured by this method, the flow of fluid between the first and second discharge ports is restricted to improve the volumetric efficiency, and the occurrence of cavitation in the interdental chamber communicating with the suction port is suppressed. It becomes possible.

  And the invention of this indication is not limited to the above-mentioned embodiment at all, and it cannot be overemphasized that various changes can be made within the range of the extension of this indication. Furthermore, the mode for carrying out the invention described above is merely a specific form of the invention described in the Summary of Invention column, and does not limit the elements of the invention described in the Summary of Invention column. Absent.

  The invention of the present disclosure can be used in the gear pump manufacturing industry.

Claims (11)

An inner rotor having a plurality of outer teeth, an outer rotor having a plurality of inner teeth larger than the outer teeth of the inner rotor and arranged to be eccentric with respect to the inner rotor, and two adjacent outer In a gear pump including a plurality of interdental chambers defined by two internal teeth adjacent to a tooth,
One suction port communicating with the interdental chamber, the volume of which increases with the rotation of the inner rotor and the outer rotor;
First and second discharge ports that are partitioned by a partition wall and are independent of each other, each communicating with the interdental chamber, the volume of which decreases as the inner rotor and the outer rotor rotate.
The suction side clearance is defined as the minimum clearance between the external teeth and the internal teeth that define the interdental chamber that communicates with the suction port and that has a maximum volume change when the inner rotor rotates by a unit angle. The external teeth and the internal teeth defining an interdental chamber at least partially overlapping the partition wall between the first and second discharge ports when the volume change amount per unit angle is maximized. A gear pump in which the suction side clearance is larger than the discharge side clearance when the minimum clearance is the discharge side clearance.   The gear pump according to claim 1, wherein the plurality of external teeth are formed asymmetrically with respect to a tooth profile center line. The gear pump according to claim 1 or 2,
The gear pump, wherein the suction side clearance is at least three times the discharge side clearance. The gear pump according to any one of claims 1 to 3,
When the inner rotor and the outer rotor are rotating, any one of the outer teeth closest to the position where the tooth tops of the external teeth and the tooth tops of the internal teeth face each other in a straight line corresponds. A gear pump in which the external tooth positioned one rear side in the rotation direction of the inner rotor comes into contact with the corresponding internal tooth while being in contact with the internal tooth. In the gear pump according to any one of claims 1 to 4,
The tip clearance between the external teeth and the internal teeth when the tooth tops of the external teeth and the internal teeth corresponding to the external teeth are aligned in a straight line is more than that of the external teeth. A gear pump that is equal to or greater than a minimum clearance between the drive tooth surface of the external tooth and the corresponding driven tooth surface of the internal tooth that are located on the rear side in the rotation direction of the inner rotor. The gear pump according to claim 5,
A gear pump in which the tip clearance between any one of the outer teeth and the corresponding inner teeth is 200 μm or less. The gear pump according to any one of claims 1 to 6,
Each of the outer teeth of the inner rotor is
A tooth tip formed by an epitrochoid curve obtained by rolling without rolling while an outer circle having a radius smaller than the radius of the drawing point is circumscribed to the base circle;
The addendum circle having a radius smaller than the radius of the drawing point is formed by a hypotrochoid curve obtained by rolling without slipping while inscribed in the basic circle common to the epitrochoid curve, and the tooth tip portion Than the first tooth bottom portion located on the front side in the rotational direction of the inner rotor,
A second tooth bottom formed by a hypotrochoid curve obtained by rolling the inward circle with the base circle without slipping, and continuing to the first tooth bottom on the rear side in the rotation direction; ,
A first intermediate part formed by an arbitrary curve and located between the tooth tip part and the first tooth bottom part;
A second intermediate portion formed by an arbitrary curve and positioned between the tooth tip portion and the second tooth bottom portion;
The length of the curve that forms the first intermediate portion is longer than the length of the curve that forms the second intermediate portion.   The gear pump according to claim 7, wherein the first intermediate portion is formed by at least an involute curve. The gear pump according to claim 7 or 8,
The range from the intersection of the second intermediate portion with the basic circle to the boundary with the tooth tip portion is the abduction circle circumscribing the basic circle while changing the radius of the drawing point of the abduction circle. Is formed by a first curve obtained by rolling without slipping, and the range from the intersection of the second intermediate portion with the base circle to the boundary with the second tooth bottom is the inward circle. A gear pump formed by a second curve obtained by rolling the inversion circle inscribed in the basic circle without slipping while changing the radius of the drawing point. The gear pump according to any one of claims 1 to 9,
The tooth profile of the outer rotor defined by the plurality of internal teeth is “e” as the amount of eccentricity of the rotation center of the outer rotor with respect to the rotation center of the inner rotor, and the rotation center of the inner rotor and the outer rotor The clearance between the rotation tip, the top of the tooth tip of the external tooth, and the top of the tooth tip of the internal tooth is aligned with the tooth tip of the external tooth and the tooth tip of the internal tooth. t ″, the center of rotation of the inner rotor is revolved by a predetermined angle on the circumference of the diameter 2 · e + t centered on the center of rotation of the outer rotor, and the center of rotation of the inner rotor is rotated by a predetermined angle. Envelopes drawn for a plurality of tooth profile lines obtained by rotating the inner rotor by the predetermined angle and the rotation angle corresponding to the number of teeth of the inner rotor when revolving Gear pump that is determined Zui. An inner rotor having a plurality of outer teeth, an outer rotor having a plurality of inner teeth larger than the outer teeth of the inner rotor and arranged to be eccentric with respect to the inner rotor, and two adjacent outer A plurality of interdental chambers defined by the two internal teeth adjacent to the teeth, and one suction port communicating with the interdental chambers that increase in volume as the inner rotor and the outer rotor rotate Manufacturing a gear pump including first and second discharge ports that are partitioned by a partition wall and are independent of each other, and each communicates with the interdental chamber that decreases in volume as the inner rotor and the outer rotor rotate. A method,
The suction side clearance is defined as the minimum clearance between the external teeth and the internal teeth that define the interdental chamber that communicates with the suction port and that has a maximum volume change when the inner rotor rotates by a unit angle. The external teeth and the internal teeth defining an interdental chamber at least partially overlapping the partition wall between the first and second discharge ports when the volume change amount per unit angle is maximized. A method of manufacturing a gear pump including the step of forming the inner rotor so that the suction side clearance is larger than the discharge side clearance when the minimum clearance is the discharge side clearance.

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