Internal gear pump

Abstract

To provide an internal gear pump which is adapted to a high-temperature use, and can be used in a wide range temperature.SOLUTION: A ring-shaped inner tooth gear 5 having inner teeth 5A is rotatably accommodated in an accommodation hole 2 of a pump housing 4, and an outer tooth gear 6 having outer teeth 6A internally engaged with the inner teeth 5A of the internal gear 5 is eccentrically accommodated in the inner tooth gear 5. Between both the gears 5, 6, a suction area space S is formed in a region in which an engagement clearance between both the teeth 5A, 6A is increased while communicating with a suction port 9, and a discharge area space P is formed in a region in which the engagement clearance between both the teeth 5A, 6A is reduced while communicating with a discharge port 11. The pump housing 4 is formed of an aluminum alloy, and both the gears 5, 6 are formed of thermosetting resins whose linear expansion coefficients are substantially the same with each other in a flow direction and an orthogonal direction at a glass transition point at 100°C or higher. In both the gears 5, 6, a difference of the linear expansion coefficient with the pump housing 4 is set within a range of zero to minus 9×10-6 / C.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an internal gear pump that accommodates an external gear eccentrically inside a ring-shaped internal gear and rotates both gears to suck in and discharge liquid. [Background technology]

[0002] This type of internal gear pump has a ring-shaped internal gear rotatably housed in a pump housing, and an external gear eccentrically housed inside the internal gear. The rotation of both gears draws liquid in through a suction port and discharges it from a discharge port. The pump housing has a linear expansion coefficient of 21×10 -6 The gears are made of aluminum alloy (ADC12) with a linear expansion coefficient of 25×10 -6 / ℃, and both gears are made of polyamide resin with a higher linear expansion coefficient than the aluminum alloy that makes up the housing. In this way, the difference in oil volume between the vehicle's normal driving range and at high temperatures, which was an issue with conventional general internal gear pumps in which both gears are made of iron-based sintered materials, is kept small. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-286970 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in such conventional internal gear pumps, both gears are made of polyamide resin, a thermoplastic resin, which is not suitable for use at high temperatures, limiting the temperature range in which the pump can be used.

[0005] An object of the present invention is to provide an internal gear pump which is suitable for use at high temperatures and can be applied over a wide range of temperatures. [Means for solving the problem]

[0006] In order to achieve this object, the present invention takes the following measures: A ring-shaped internal gear having internal teeth is rotatably accommodated in an accommodation hole of a pump housing, and an external gear having external teeth that mesh internally with the internal teeth of the internal gear is eccentrically accommodated inside the internal gear, and an intake area space is formed between both gears in a region where the meshing gap between both teeth increases as both gears rotate, and the intake area space is formed in communication with a intake port that draws in liquid, and a discharge area space is formed in communication with a discharge port that discharges liquid to a region where the meshing gap between both teeth decreases as both gears rotate, and a pump chamber is defined by the internal teeth of the internal gear and the external teeth of the external gear, and the pump chamber is provided such that the volume of the intake area space increases as both gears rotate, drawing in liquid from the intake port, and the volume of the discharge area space decreases, discharging liquid to the discharge port, and the pump housing is formed of an aluminum alloy, and both gears are formed of a thermosetting resin having a glass transition point of 100°C or higher and a linear expansion coefficient that is approximately the same in the direction perpendicular to the flow direction, and the difference in the linear expansion coefficient between both gears and the pump housing is between 0 and minus 9 x 10 -6 The internal gear pump is characterized by having a temperature range of 100 / °C. The flow direction refers to the direction in which the liquid thermosetting resin flows when forming the two gears, and the perpendicular direction refers to the direction perpendicular to the flow direction. The linear expansion coefficient being substantially the same in the flow direction and the perpendicular direction means that the difference in the linear expansion coefficient between the flow direction and the perpendicular direction is between 0 and 2×10 -6 / ℃ range. Effect of the Invention

[0007] As described above in detail, the invention described in claim 1 is characterized in that the pump housing is made of an aluminum alloy, and both gears are made of a thermosetting resin having a glass transition point of 100°C or higher and a linear expansion coefficient that is substantially the same in the flow direction and in the direction perpendicular to the flow direction, and the difference in the linear expansion coefficient between both gears and the pump housing is between 0 and minus 9 x 10 -6 / ℃ range. As a result, both gears can maintain their strength at high temperatures of over 100℃, making them suitable for use at high temperatures and applicable to a wide range of temperatures.

[0008] In addition, the linear expansion coefficients of both gears are made substantially the same in the flow direction and the perpendicular direction, so the linear expansion coefficients of both gears can be made without being restricted by the directionality of the flow direction and the perpendicular direction, making it easy to set the clearance between the pump housing.

[0009] Furthermore, the difference in linear expansion coefficient between the gears and the pump housing is from 0 to minus 9 x 10 -6 / ℃ range. Therefore, both gears can rotate smoothly while maintaining the appropriate clearance between them and the pump housing. The difference in linear expansion coefficient is minus 9×10 -6 If the difference is below 0 / ℃, it is equivalent to the iron-based sintered material used in conventional internal gear pumps, and has the disadvantage that the clearance with the pump housing is small at low temperatures, and the drive torque that rotates the two gears is large. Also, if the difference in linear expansion coefficient is above 0, the clearance between the two gears and the pump housing becomes too small at higher temperatures, and there is a risk of the two gears seizing up. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of an internal gear pump according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line BB in FIG. 2. [Figure 4] FIG. 11 is a characteristic diagram showing the relationship between side clearance and temperature, illustrating a comparison between the embodiment and a conventional example. [Diagram 5] FIG. 11 is a characteristic diagram showing the relationship between body clearance and temperature, illustrating a comparison between an embodiment and a conventional example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In Fig. 1 to Fig. 3, reference numeral 1 denotes a pump body forming a bottomed accommodation hole 2. Reference numeral 3 denotes a cover member attached to the pump body 1 so as to close the opening of the accommodation hole 2 with one end surface 3A. The pump body 1 and the cover member 3 have a linear expansion coefficient of 21 x 10 -6 The pump body 1 and the cover member 3 constitute a pump housing 4.

[0012] Reference numeral 5 denotes a ring-shaped internal gear having seven internal teeth 5A, which is rotatably housed in the housing hole 2. Reference numeral 6 denotes an external gear having six external teeth 6A that internally mesh with the internal teeth 5A, which is eccentrically housed inside the internal gear 5. Both gears 5 and 6 are formed of a thermosetting resin, and have a glass transition point of 220 to 300°C. In addition, both gears 5 and 6 have a linear expansion coefficient of 13×10 in the flow direction. -6 / °C, 14 x 10 at right angles -6 / °C, and is approximately the same in the direction perpendicular to the flow direction. The expansion coefficients of both gears 5 and 6 are 13×10 -6 / °C, 14 x 10 at right angles -6 / ℃, the difference in linear expansion coefficient with the pump housing 4 is 0 to minus 9 x 10 -6 The range is / ℃.

[0013] Reference numeral 7 denotes a through hole that passes through the axial direction at the radial center of the external gear 6 and is provided with a cross section that is approximately two-sided. Reference numeral 8 denotes a drive shaft that rotates the external gear 6 and has a tip end that is approximately two-sided and fits into the through hole 7 of the external gear 6. Reference numerals S and P denote the suction area space and discharge area space, respectively, that are provided between the gears 5 and 6. The suction area space S is formed in an area where the meshing gap between the teeth 5A and 6A increases as the gears 5 and 6 rotate. The discharge area space P is formed in an area where the meshing gap between the teeth 5A and 6A decreases as the gears 5 and 6 rotate. Reference numeral T denotes a pump chamber, which is divided into multiple spaces by the internal teeth 5A of the internal gear 5 and the external teeth 6A of the external gear 6 and is provided such that the volume of the suction area space S increases as the gears 5 and 6 rotate and the volume of the discharge area space P decreases.

[0014] Reference numeral 9 denotes a first suction port communicating with the suction area space S, which opens as a semicircular recess formed in one end surface 3A of the cover member 3 constituting the pump housing 4. Reference numeral 9A denotes a second suction port communicating with the suction area space S, which opens as a semicircular recess formed in the bottom surface of the accommodation hole 2 of the pump body 1 constituting the pump housing 4, and is disposed opposite the first suction port 9 in the axial direction via the suction area space S. Reference numeral 10 denotes an intake passage connected to the first suction port 9, which is formed in the cover member 3 and passes liquid sucked from the low pressure side. Reference numeral 11 denotes a first discharge port communicating with the discharge area space P, which is formed as a semicircular recess formed in one end surface 3A of the cover member 3 constituting the pump housing 4, and which opens at a position radially symmetrical to the first suction port 9. A second discharge port (not shown) is disposed axially opposite the first discharge port 11 via a discharge area space P, and the second discharge port opens by forming a semicircular recess in the bottom surface of the accommodation hole 2 of the pump body 1 that constitutes the pump housing 4. Reference numeral 12 denotes a discharge flow passage connected to the first discharge port 11, which is formed in the cover member 3 and through which the liquid to be discharged to the load side flows.

[0015] Next, the operation of this configuration will be described. When the external gear 6 is rotated by the drive shaft 8, the internal gear 5, which is in inscribed mesh with the external gear 6, is rotated, and liquid flows from the low pressure side through the suction passage 10, is sucked into the suction area space S from the first suction port 9, is transported to the discharge area space P, and is discharged through the discharge passage 12 from the first discharge port 11. At this time, the acting forces based on the pressure of the liquid act axially in balance at both suction ports 9, 9A and both discharge ports 11 on both gears 5, 6, and are not pressed in the axial direction.

[0016] In this operation, the pump housing 4 is made of an aluminum alloy, and the gears 5 and 6 are made of a thermosetting resin having a glass transition point of 100° C. or higher and a linear expansion coefficient that is substantially the same in the flow direction and in the direction perpendicular to the flow direction. The difference in linear expansion coefficient between the gears 5 and 6 and the pump housing 4 is 0 to minus 9×10 -6 / °C. Therefore, both gears 5 and 6 can maintain their strength at high temperatures of 100°C or higher, and are therefore suitable for use at high temperatures and can be applied to a wide range of temperatures.

[0017] Furthermore, the linear expansion coefficients of both gears 5, 6 are made substantially the same in the flow direction and the direction perpendicular to the flow direction. Therefore, both gears 5, 6 can be made without being restricted by the directionality of the linear expansion coefficient in the flow direction and the direction perpendicular to the flow direction, so that the clearance between them and the pump housing 4 can be easily set. The clearance between them and the pump housing 4 refers to the side clearances between the side surfaces of both gears 5, 6 and the bottom surface of the accommodating hole 2 and between one end surface 3A of the cover member 3, and the body clearance between the outer peripheral surface of the internal gear 5 and the inner peripheral surface of the accommodating hole 2.

[0018] Furthermore, the difference in linear expansion coefficient between the gears 5 and 6 and the pump housing 4 is from 0 to minus 9 x 10 -6 / °C. Therefore, the gears 5 and 6 can be rotated smoothly while maintaining an appropriate clearance between them and the pump housing 4. The difference in linear expansion coefficient is set to minus 9×10 -6 If the difference in linear expansion coefficient is below 0, the clearance between the gears 5, 6 and the pump housing 4 becomes too small at high temperatures, which is a drawback of the material being equivalent to the iron-based sintered material used in conventional internal gear pumps, and the drive torque for rotating the gears 5, 6 becomes large. Also, if the difference in linear expansion coefficient is above 0, the clearance between the gears 5, 6 and the pump housing 4 becomes too small at high temperatures, which may cause the gears 5, 6 to seize.

[0019] In the embodiment described above, the pump housing 4 is composed of the pump body 1 and the cover member 3, but the pump housing may also be composed of three members: a first member that penetrates and forms an accommodation hole that accommodates both gears, a second member that is attached to one side of the first member with which one end faces of both gears slide, and a third member that is attached to the other side of the first member with which the other end faces of both gears slide. Furthermore, the through hole 7 into which the drive shaft 8 that rotates and drives the external gear 6 is fitted is formed to have a substantially two-face shape in vertical cross section, but it goes without saying that the through hole may be formed to have a substantially D-shape or spline shape in vertical cross section.

[0020] FIG. 4 shows the relationship between side clearance and temperature, and FIG. 5 shows the relationship between body clearance and temperature, each comparing one embodiment with a conventional example. And the linear expansion coefficient is 21 x 10 -6 Gears 5 and 6 with a tooth width of 7.5 mm are housed in a pump housing 4 made of an aluminum alloy (ADC12) at 100°C. The internal gear 5 has an outer diameter of 31 mm. In Figure 4, the side clearance at a temperature of 120°C is set as the standard at 42 μm, and the side clearance at temperatures of 80°C, 25°C, and -40°C were calculated. Linear expansion coefficient is 13 x 10 -6 In a pump corresponding to one embodiment using both gears 5 and 6 made of a thermosetting resin of 100 / °C, the difference in linear expansion coefficient between the pump housing 4 and the gears 5 and 6 is −8×10 -6 / ℃, and as shown by the solid line L1, the side clearance was 40 μm at a temperature of 80°C, 37 μm at a temperature of 25°C, and 33 μm at a temperature of -40°C. In contrast, the linear expansion coefficient is 25×10 -6 In a pump corresponding to the conventional example, both gears 5 and 6 are made of a thermoplastic polyamide resin (PA66) with a temperature of 100 °C or more, the difference in linear expansion coefficient between the pump housing 4 and the gears 5 and 6 is 4 × 10 -6 / ℃, as shown by dashed line L2, the side clearance was 43 μm at a temperature of 80°C, 45 μm at a temperature of 25°C, and 47 μm at a temperature of -40°C.

[0021] In Figure 5, the body clearance at a temperature of 120°C is set as the standard at 128 μm, and the body clearance at temperatures of 80°C, 25°C, and -40°C were calculated. In a pump corresponding to one embodiment using both gears 5 and 6 formed from the same thermosetting resin as in Figure 4, as shown by the solid line L11, the body clearance was 120 μm at a temperature of 80°C, 107 μm at a temperature of 25°C, and 91 μm at a temperature of -40°C. In contrast, in a pump corresponding to the conventional example in which both gears 5 and 6 are formed from the same thermoplastic resin polyamide resin (PA66) as in Figure 4, the body clearance was 133 μm at a temperature of 80°C, 140 μm at a temperature of 25°C, and 148 μm at a temperature of -40°C, as shown by the dashed line L21.

[0022] Thus, in the pump corresponding to one embodiment shown by the solid lines L1 and L11, as the temperature changes from -40°C to 25°C, 80°C, and 120°C, both the side clearance and the body clearance increase, so that at temperatures higher than 120°C the clearance between the gears 5, 6 and the pump housing 4 does not become too small, preventing the gears 5, 6 from seizing. In contrast, in the pump corresponding to the conventional example shown by dashed lines L2 and L21, as the temperature changes from -40°C to 25°C, 80°C, and 120°C, both the side clearance and the body clearance decrease, so that at temperatures higher than 120°C the clearance between the gears 5, 6 and the pump housing 4 becomes too small, and there is a risk that the gears 5, 6 will seize. [Explanation of symbols]

[0023] 2: Storage hole 4: Pump housing 5: Internal gear 5A: Internal teeth 6: External gear 6A: External teeth 9, 9A: Intake port 11: Discharge port S: Suction area space P:Discharge area space T: Pump room

Claims

【Request 1】 A ring-shaped internal gear having internal teeth is rotatably accommodated in an accommodation hole of a pump housing, and an external gear having external teeth that mesh internally with the internal teeth of the internal gear is eccentrically accommodated inside the internal gear, and an intake area space is formed between both gears in a region where the meshing gap between both teeth increases as both gears rotate, and the intake area space is formed in communication with a intake port that draws in liquid, and a discharge area space is formed in communication with a discharge port that discharges liquid to a region where the meshing gap between both teeth decreases as both gears rotate, and a pump chamber is defined by the internal teeth of the internal gear and the external teeth of the external gear, and the pump chamber is provided such that the volume of the intake area space increases as both gears rotate, drawing in liquid from the intake port, and the volume of the discharge area space decreases, discharging liquid to the discharge port, and the pump housing is formed of an aluminum alloy, and both gears are formed of a thermosetting resin having a glass transition point of 100° C. or higher and a linear expansion coefficient that is approximately the same in a direction perpendicular to the flow direction, and the difference in the linear expansion coefficient between both gears and the pump housing is between 0 and minus 9×10 －６ / °C range of the internal gear pump.

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