Method for evaluating and forming the tooth profile of an internal gear pump

Abstract

To make compatible both the prevention of interference in a position other than an engagement part of an inner rotor and an outer rotor, and the suppression of oil leakage.SOLUTION: A tooth shape evaluation method includes: preparation step S1 for arranging an inner rotor 2 and an outer rotor 3 in ideal center positions; inner rotor rotation step S2 for rotating the inner rotor up until the inner rotor is engaged with the outer rotor at a lower dead point, and the outer rotor and the inner rotor have first contact points 11; and outer rotor rotation step S3 for rotating the outer rotor in a direction which is the same as a rotation direction of the inner rotor in a state in which the inner rotor is fixed in the first contact point. In the outer rotor rotation step, a state whether or not the outer rotor and the inner rotor have second contact points while an external peripheral face 3b of the outer rotor 3 contacts with an internal peripheral face 4a of a casing 4 is made to be an index of an evaluation.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a method for evaluating the tooth profile and a method for forming the tooth profile of an internal gear pump.

Background Art

[0002] In a power mechanism such as an engine, a pump for lubricating lubrication parts with oil is provided. For example, an internal gear pump performs a pump operation by changing the volume of a plurality of confinement portions formed therebetween when the outer teeth of an inner rotor and the inner teeth of an outer rotor rotate while meshing with each other, thereby sucking and discharging oil.

[0003] In such an internal gear pump, the tooth profiles of the inner rotor and the outer rotor are designed so that a predetermined tooth clearance is provided between the tooth surfaces of the inner rotor and the outer rotor. However, during actual pump operation, due to the dimensional accuracy of the tooth profile, the tooth clearance between the inner rotor and the outer rotor deviates from the designed value, and the inner rotor and the outer rotor may have contact points other than the meshing portion, and may not rotate smoothly, resulting in an increase in driving torque.

[0004] Regarding such a problem, in Patent Document 1, it is proposed to repeatedly design the tooth profile of the outer rotor by largely offsetting the tooth surface of the inner rotor outward with respect to the center of the inner rotor by an amount corresponding to the tooth clearance so as to ensure a tooth clearance between the outer rotor and the outer rotor at a location other than the meshing portion.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Incidentally, oil leakage can be prevented by making the gap between the teeth of the inner rotor and the outer rotor as narrow as possible. However, if the gap between the teeth is designed to be too narrow, the above-mentioned interference is more likely to occur and the driving torque will increase. On the other hand, if the gap between the teeth is designed to be too wide, the above-mentioned interference is less likely to occur, but there is a risk that leakage will increase. In Patent Document 1, the offset amount at each position of the inner rotor's rotation angle is set to be larger than the machining error that can be tolerated for the rotor, so as to prevent interference at positions other than the meshing part of the inner rotor and the outer rotor even if machining errors occur. In a tooth profile forming method like that in Patent Document 1, there is a concern that leakage will increase due to the gap between the teeth being enlarged more than necessary, and there is a risk that two-point contact cannot be avoided.

[0007] The present invention has been made in view of the above, and its objective is to provide a tooth profile evaluation method and tooth profile forming method for an internal gear pump that simultaneously prevents interference at positions other than the meshing portion of the inner rotor and outer rotor, thereby preventing an increase in driving torque, and suppresses an increase in leakage by narrowing the inter-tooth gap as much as possible. [Means for solving the problem]

[0008] To achieve the above objective, this invention takes into account the body clearance between the outer rotor's outer surface and the casing's inner surface, thereby preventing interference at locations other than the meshing portion between the inner and outer rotors without unnecessarily enlarging the inter-tooth gap.

[0009] Specifically, in the first invention, An inner rotor having n external teeth, An outer rotor having n+1 internal teeth that mesh with the external teeth from the outer circumferential side, The casing comprises a body clearance between itself and the outer rotor and covering the outer circumference of the outer rotor, In an internal gear pump that transports fluid by drawing in or discharging fluid through volume changes in multiple enclosed portions formed between the tooth surfaces of the inner rotor and the outer rotor when the inner rotor and the outer rotor mesh and rotate, A preparation step to position the inner rotor and the outer rotor, respectively, at their ideal center positions, An inner rotor rotation step in which the inner rotor is rotated until it engages with the outer rotor at the bottom dead center and the outer rotor and the inner rotor have a first contact point, The process includes an outer rotor rotation step in which, with the inner rotor fixed at the first contact point, the outer rotor is rotated in the same direction as the rotation direction of the inner rotor, In the outer rotor rotation process, the evaluation criterion is whether or not the outer rotor and the inner rotor have a second contact point before the outer circumferential surface of the outer rotor comes into contact with the inner circumferential surface of the casing.

[0010] With the above configuration, considering that the outer rotor moves during actual pump operation and interferes with the inner circumferential surface of the casing, it is possible to evaluate whether the tooth profile prevents interference at positions other than the meshing area between the inner and outer rotors without unnecessarily enlarging the inter-tooth gap.

[0011] In the second invention, in the outer rotor rotation process of the first invention, If the outer rotor and the inner rotor do not have a second contact point, the tooth profiles of the outer rotor and the inner rotor are judged to be acceptable. If the outer rotor and the inner rotor have a second contact point, the tooth profiles of the outer rotor and the inner rotor are deemed unacceptable.

[0012] With the above configuration, it is possible to easily determine whether the tooth profile is suitable for preventing interference at positions other than the meshing area between the inner and outer rotors without unnecessarily widening the interdental gap.

[0013] The third invention is a method for forming the tooth profile of the inner rotor that was deemed unacceptable in the second invention, A meshing step in which the direction of the tooth tips of the inner rotor is aligned with the direction of the tooth roots of the outer rotor, and the inner rotor and the outer rotor are meshed together, An outer rotor setting step in which, at the tooth root of the outer rotor formed by the bottom and curved portions located on both sides of the bottom, the radius of curvature of the curved portion is virtually enlarged, and a virtual curved portion is set that bites inward from the tooth tip of the inner rotor, The process includes an inner rotor modification step of grinding away the portion of the tooth tip of the inner rotor that protrudes outward from the virtual curved portion.

[0014] The tooth surface of the inner rotor is designed so that the tip circle and root circle are connected. However, if the joint between the tip and root circles is angular, it is thought to affect interference with the outer rotor. With the above configuration, by modifying the tooth profile of the inner rotor based on the corner radius of the tooth root of the outer rotor, the joint between the tip and root circles is formed smoothly, preventing the gap between the inner and outer rotors from expanding unnecessarily. This makes it possible to prevent interference between the inner and outer rotors, suppress the increase in driving torque, and prevent oil leakage at the same time. [Effects of the Invention]

[0015] As described above, the technology disclosed herein makes it possible to provide a tooth profile evaluation method and tooth profile forming method for an internal gear pump that simultaneously prevents interference at positions other than the meshing portion of the inner rotor and outer rotor, thereby suppressing an increase in driving torque, and prevents an increase in leakage. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram showing an internal gear pump according to an embodiment of the present invention. [Figure 2]It is a schematic diagram for explaining a method of creating an inner rotor. [Figure 3] It is a schematic diagram for explaining a method of creating an outer rotor. [Figure 4] It is a partially enlarged view for explaining a method of creating an outer rotor. [Figure 5] It is a schematic diagram showing a state where an inner rotor and an outer rotor have a first contact point. [Figure 6] It is a schematic diagram showing a state where the outer rotor contacts the inner peripheral surface of the casing. [Figure 7] It is a schematic diagram for explaining a method of modifying the tooth profile of an inner rotor. [Figure 8] It is a partially enlarged view for explaining a method of modifying the tooth profile of an inner rotor. [Figure 9] It is a partially enlarged view for explaining a method of modifying the tooth profile of an inner rotor. [Figure 10] It is a partially enlarged view for explaining a method of modifying the tooth profile of an inner rotor. [Figure 11] It is a flowchart of a tooth profile evaluation method and a tooth profile forming method for an internal gear pump. [Figure 12] It is a schematic diagram for explaining the R size of the tooth profile after modifying the tooth profile of an inner rotor. [Figure 13] It is a schematic diagram showing the range affected by oil leakage.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0018] [Configuration of Gear Pump] Figure 1 is a schematic diagram showing a gear pump according to an embodiment of the present invention. As shown in Figure 1, this gear pump is an internal gear pump 1 and comprises an inner rotor 2, an outer rotor 3, and a casing 4. When the inner rotor 2 and outer rotor 3 mesh and rotate, the gear pump 1 transports fluid such as oil by drawing in or discharging fluid through the volume change of a plurality of enclosed portions 5 formed between the tooth surfaces of the inner rotor 2 and outer rotor 3.

[0019] The inner rotor 2 has n external teeth 2a on its outer circumferential surface, and a pump shaft (not shown) is inserted through its center. The external teeth 2a are formed continuously in the circumferential direction and mesh with the internal teeth 3a of the outer rotor 3. The external teeth 2a of the inner rotor 2 are formed one less than the internal teeth 3a of the outer rotor 3. In this embodiment, the inner rotor 2 has 6 external teeth 2a.

[0020] The outer rotor 3 has n+1 internal teeth 3a on its inner circumferential surface. In this embodiment, the outer rotor 3 has 7 external teeth 2a formed on it. The internal teeth 3a are formed continuously in the circumferential direction and mesh with the external teeth 2a of the inner rotor 2 from the outer circumferential side. The outer rotor 3 is positioned eccentrically with respect to the inner rotor 2. The outer rotor 3 rotates in accordance with the rotation of the inner rotor 2.

[0021] The casing 4 covers the outer circumference of the outer rotor 3. The casing 4 has a rotor housing space with a circular cross-section, and the outer rotor 3 and the inner rotor 2 are housed in this rotor housing space. The gear pump 1 has a predetermined body clearance 6 between the inner circumferential surface 4a that forms the rotor housing space and the outer circumferential surface 3b of the outer rotor.

[0022] [How to create an inner rotor] Figure 2 is a schematic diagram illustrating the method for creating the inner rotor. As shown in Figure 2, the inner rotor 2 of this embodiment is created using a general method based on the trochoid curve 20. That is, first, the base trochoid curve 20 is created.

[0023] When parameters A, B, and e are defined as follows, the coordinates (x,y) of the trochoid curve are expressed by equation (1) below, given the following parameters and the angle parameter θ. A: This is the diameter of the fixed circle (base circle) centered on the center point of the inner rotor. B: This is the diameter of a circle that rolls on the base circumference (a rolling circle). e: The trochoidal curve is drawn by the trajectory of a point located e away from the center of the rotating circle as it rolls. This corresponds to the eccentricity of the outer rotor.

[0024]

number

[0025] The tooth profile curve of the inner rotor 2 is designed by the envelope of the group of trajectory circles 21 centered on points on the trochoid curve 20 obtained by equation (1) above.

[0026] When C is the diameter of the locus circle 21 centered on a point on the trochoid curve 20, the coordinates (X,Y) of the envelope are expressed by the following equations (2) and (3), and of equations (2) and (3), (X 2 +Y 2 The smaller of the two values ​​(X,Y) is taken as the tooth profile curve of the inner rotor 2. Note that the parameter K in equations (2) and (3) is expressed in equation (4).

[0027]

number

[0028] [How to create an outer rotor] Figure 3 is a schematic diagram illustrating the method for creating the outer rotor. As shown in Figure 3, the outer rotor 3 of this embodiment is created using a general method for creating the outer rotor 3 relative to the inner rotor 2 which is created based on the trochoid curve 20. That is, first, a root circle 31 is created along the tooth root of the outer rotor 3. The diameter D of the root circle is expressed by the following equation (5) using the above parameters A to C and e. In the following equation (5), γ1 is an adjustment dimension set to provide an intertooth gap between the tooth profiles of the inner rotor 2 and the outer rotor 3. Using this parameter D, the root circle 31 expressed by the following equation (6) is created.

[0029] D = A + B + 4e - C + γ1 ... (5) X 2 +Y 2 =(D / 2) 2 ...(6) Next, an outside circle 32 is created along the tooth tips of the outer rotor 3. The parameter PCD of the outside circle 32 is defined as PCD = A + B + γ2, using the parameters A and B mentioned above and the adjustment dimension γ2 set to create an intertotal gap between the tooth surfaces of the inner rotor 2 and the outer rotor 3. Using such a PCD, the outside circle 32 of the outer rotor 3 is expressed by the following equation (7). In the following equation (7), C is the diameter of the outside circle 32 of the outer rotor 3, and is the same as the diameter of the trajectory circle 21 mentioned above.

[0030]

number

[0031] The outer rotor 3 is created by joining the root circle 31 represented by formula (6) and the tip circle 32 represented by formula (7) above. The tooth profile of the outer rotor 3 created in this way has a sharp shape at the joint between the root circle 31 and the tip circle 32, so it is necessary to make the joint R-shaped.

[0032] Figure 4 is a schematic diagram illustrating the method for creating the outer rotor, and is a magnified view of a portion of it. The joint between the root circle 31 and the tip circle 32 of the outer rotor 3 is formed in an R shape along the correction circle 33, which is the circle that circumscribes the tip circle 32 and is the circle that circumscribes the root circle 31.

[0033] [Method for evaluating tooth shape] It is preferable to inspect whether the tooth profiles of the inner rotor 2 and outer rotor 3, formed as described above, interfere with each other at positions other than the meshing portion when they are actually meshed and rotated.

[0034] The method for evaluating the tooth profiles of the inner rotor 2 and outer rotor 3 will be explained using the flowcharts in Figures 5 to 10 and Figure 11.

[0035] First, as preparation step S1, the inner rotor 2 and outer rotor 3 are positioned at their respective ideal center positions. The ideal center position is a state in which the rotation center of the inner rotor 2 coincides with the rotation center of the rotation axis fixed to the inner rotor 2, and the rotation center of the outer rotor 3 coincides with the center of the rotor housing space in which the outer rotor 3 is housed. This is also called the theoretical eccentric position.

[0036] Next, as the inner rotor rotation process S2, as shown in Figure 5, the inner rotor 2 is rotated in the direction of the arrow in Figure 5 while the outer rotor 3 is fixed, until the inner rotor 2 meshes with the outer rotor 3 at the bottom dead center and the outer rotor 3 and inner rotor 2 have a first contact point 11. In Figure 5, a predetermined inter-tooth gap 10 exists between the outer rotor 3 and the inner rotor 2 in the area indicated by the dotted circle.

[0037] Next, as the outer rotor rotation process S3, as shown in Figure 6, with the inner rotor 2 fixed at the first contact point 11, the outer rotor 3 is rotated in the same direction as the rotation direction of the inner rotor 2 (in the direction of the arrow in Figure 6).

[0038] In the outer rotor rotation process S3, whether or not the outer rotor 3 and the inner rotor 2 have a second contact point before the outer circumferential surface 3b of the outer rotor 3 contacts the inner circumferential surface 4a of the casing 4 can be used as an evaluation indicator. For example, at the position marked with a star in Figure 6, the outer circumferential surface 3b of the outer rotor 3 contacts the inner circumferential surface 4a of the casing 4.

[0039] Specifically, in the evaluation of the tooth profile, if the outer rotor 3 and inner rotor 2 do not have a second contact point in the judgment step S4, the tooth profiles of the outer rotor 3 and inner rotor 2 are judged as acceptable, and the evaluation is terminated. If the outer rotor 3 and inner rotor 2 do have a second contact point in the judgment step S4, the tooth profiles of the outer rotor 3 and inner rotor 2 are judged as unacceptable, and the tooth profile of the inner rotor 2 is corrected.

[0040] [Inner rotor tooth profile modification] If the inner rotor 2 is deemed unacceptable in the judgment step S4, the tooth profile of the inner rotor 2 is modified. First, in the meshing step S5, as shown in Figure 7, the direction of the tooth tip 2b of the inner rotor 2 is aligned with the direction of the tooth root 7a of the virtual upper outer rotor 7, and the inner rotor 2 and the virtual upper outer rotor 7 are meshed together so that they have a common line of symmetry L.

[0041] Figure 8 is an enlarged view of section X in Figure 7, showing an enlarged view of the junction 2c between the tip circle and root circle of the inner rotor 2. The root 7a of the outer rotor 7 is formed by a bottom 70 that contacts the root circle and curved portions 71 located on both sides of the bottom 70. The curved portions 71 are the junction between the root circle and the tip circle, and are the parts where the angular shape was smoothed during the formation of the outer rotor 7. As the outer rotor setting step S6, as shown in Figure 8, the radius of curvature of the curved portion 71 at the root 7a of the outer rotor 7 is virtually enlarged, and a virtual curved portion 72 that bites inward from the tip of the inner rotor 2 is set.

[0042] Figure 9 is an enlarged view of section X in Figure 7, similar to Figure 8. Figure 9 shows the joint portion 2c between the tip circle and root circle of the inner rotor 2 and the virtual curved portion 72 of the outer rotor 7. As shown in Figure 9, the joint portion 2c between the tip circle and root circle of the inner rotor 2 is angular. This angular joint portion 2c protrudes outward beyond the virtual curved portion 72.

[0043] In the next inner rotor modification step S7, as shown in Figure 10, the joint portion 2c of the tooth tip of the inner rotor 2 that protrudes outward from the virtual curved portion 72 is machined away, and this joint portion 2c is made into a modified joint portion 2d that is aligned with the virtual curved portion 72.

[0044] Using the inner rotor 2 and outer rotor 3 formed as described above, the tooth profile is evaluated again in the following order: preparation step S1, inner rotor rotation step S2, and outer rotor rotation step S3.

[0045] In the second determination step S4, if the outer rotor 3 and inner rotor 2 do not have a second contact point, the tooth profiles of the outer rotor 3 and inner rotor 2 are judged as acceptable, and the evaluation is terminated. In the determination step S4, if the outer rotor 3 and inner rotor 2 do have a second contact point, the tooth profiles of the outer rotor 3 and inner rotor 2 are judged as unacceptable, and the tooth profile of the inner rotor 2 is corrected again in the order of meshing step S5, outer rotor setting step S6, and inner rotor correction step S7, until the determination step S4 no longer has a second contact point between the outer rotor 3 and inner rotor 2.

[0046] As shown in Figure 12, the R size of the tooth profile of the inner rotor 2 modified in this way is expressed by the following equation (8), where the parameters Δb, Δt, R1, and R2 are defined as follows. For example, in this embodiment, α = 0.0036. Δb: This is the gap (body clearance 6) between the inner circumferential surface 4a of the casing 4 and the outer circumferential surface 3b of the outer rotor 3. Δt is the gap (intertooth gap 10) between the tooth surface of the inner rotor 2 and the tooth surface of the outer rotor 3. R1: This is the outer diameter of the outer rotor 3. R2: This is the diameter of the circle (pitch circle 8) connecting the positions where interdental gaps 10 occur.

[0047]

number

[0048] As described above, the tooth profile evaluation method for the internal gear pump of this embodiment can evaluate whether the tooth profile prevents interference at positions other than the meshing portion between the inner rotor 2 and the outer rotor 3 without unnecessarily enlarging the inter-tooth gap, taking into account that the outer rotor 3 moves during actual pump operation and its outer circumferential surface 3b interferes with the inner circumferential surface 4a of the casing 4.

[0049] If the gap between the inner rotor 2 and the outer rotor 3 is too wide, it will affect oil leakage on both sides of the circumferential direction of the enclosed portion 5, as shown by the shaded area in Figure 13. However, the tooth profile forming method of the internal gear pump in this embodiment modifies the tooth profile of the inner rotor 2 based on the shape of the corner radius of the tooth root of the outer rotor 3, so that the connection between the tip circle and the root circle is formed smoothly and the gap between the inner rotor 2 and the outer rotor 3 is not expanded unnecessarily. This method makes it possible to prevent interference at positions other than the meshing portion between the inner rotor 2 and the outer rotor 3, thereby preventing an increase in driving torque, and to suppress an increase in oil leakage.

[0050] The embodiments described above are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or uses. [Explanation of symbols]

[0051] 1. Gear pump 2 Inner rotor 2a external teeth 3 Outer rotor 3a external teeth 3b Outer surface 4. Casing 4a Inner surface 5. Enclosure 6. Body clearance 7. Virtual outer rotor 7a Root 10 Interdental gaps 11. First Contact Point 70 bottom 71 Curved section 72 Virtual curved section

Claims

1. An inner rotor having n external teeth, An outer rotor having n+1 internal teeth that mesh with the external teeth from the outer circumferential side, The casing comprises a body clearance between itself and the outer rotor and covering the outer circumference of the outer rotor, In an internal gear pump that transports fluid by drawing in or discharging fluid through volume changes in multiple enclosed portions formed between the tooth surfaces of the inner rotor and the outer rotor when the inner rotor and the outer rotor mesh and rotate, A preparation step to position the inner rotor and the outer rotor, respectively, at their ideal center positions, An inner rotor rotation step in which the inner rotor is rotated until it engages with the outer rotor at the bottom dead center and the outer rotor and the inner rotor have a first contact point, The process includes an outer rotor rotation step in which, with the inner rotor fixed at the first contact point, the outer rotor is rotated in the same direction as the rotation direction of the inner rotor, A method for evaluating the tooth profile of an internal gear pump, wherein, in the outer rotor rotation process, the evaluation criterion is whether or not the outer rotor and the inner rotor have a second contact point before the outer circumferential surface of the outer rotor comes into contact with the inner circumferential surface of the casing.

2. In the outer rotor rotation process, If the outer rotor and the inner rotor do not have a second contact point, the tooth profiles of the outer rotor and the inner rotor are judged to be acceptable. A method for evaluating the tooth profile of an internal gear pump according to claim 1, wherein the tooth profiles of the outer rotor and the inner rotor are deemed unacceptable when the outer rotor and the inner rotor have a second contact point.

3. A method for evaluating the tooth profile of an internal gear pump according to claim 2, wherein the tooth profile of the inner rotor is determined to be unacceptable, A meshing step in which the direction of the tooth tips of the inner rotor is aligned with the direction of the tooth roots of the outer rotor, and the inner rotor and the outer rotor are meshed together, An outer rotor setting step in which, at the tooth root of the outer rotor formed by the bottom and curved portions located on both sides of the bottom, the radius of curvature of the curved portion is virtually enlarged, and a virtual curved portion is set that bites inward from the tooth tip of the inner rotor, A method for forming the tooth profile of an internal gear pump, comprising an inner rotor modification step of grinding off the portion of the tooth tip of the inner rotor that protrudes outward from the virtual curved portion.

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