JP7623824B2 - Internal Gear Pump - Google Patents

Description

The present invention relates to an internal gear pump that houses an external gear eccentrically inside a ring-shaped internal gear and rotates both gears to suck in and discharge liquid.

This type of internal gear pump houses an external gear eccentrically inside a ring-shaped internal gear, and the rotation of both gears draws in liquid through a suction port and discharges it from a discharge port. The external gear has both sides recessed in the axial direction to form annular recesses, making it lighter.

JP 2011-122548 A

However, in such conventional internal gear pumps, the annular recess is sealed at the outer edge of the recess to prevent communication between the suction port and discharge port formed in an arc shape in the pump housing. Because the outer edge is thin, the seal between the two ports and the recess is not satisfactory, and there is a risk of increased leakage from the discharge port through the recess to the suction port, reducing volumetric efficiency.

The objective of the present invention is to provide an internal gear pump that can reduce leakage from the discharge port to the suction port and suppress a decrease in volumetric efficiency.

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 suction area space is formed between both gears in a region where the meshing gap between both teeth increases as both gears rotate, and the suction area space is formed in a region where the meshing gap between both teeth decreases as both gears rotate, and the discharge area space is formed in a region where the meshing gap between both teeth decreases as both gears rotate, and the discharge area space is formed in a region where the meshing gap between both teeth decreases as both gears rotate, and the discharge area space is formed in a region where the meshing gap between both teeth decreases This internal gear pump is characterized in that a plurality of beams are formed with gaps in the circumferential direction, each beam divides the annular recess in the circumferential direction, one side of each of the two gears is formed flat on the opposing side, the pump housing forms a flat sliding surface where one side of each of the two gears slides in contact, and an suction port and a discharge port are opened in the other sliding surface where the other side of each of the two gears slide in contact, and each of the circumferentially divided recesses of each of the two gears introduces, in the discharge area space , some of the liquid discharged to the discharge port through the tip of the thin-walled part forming the recess and the one sliding surface of the pump housing, thereby creating an intermediate pressure lower than the pressure of the discharge port, and in the suction area space, some of the liquid inside is extracted through the tip of the thin-walled part forming the recess and the one sliding surface of the pump housing, thereby creating an intermediate pressure higher than the pressure of the suction port.

In this case , both of the gears may be made of synthetic resin.

As described above in detail, the invention described in claim 1 defines a pump chamber by the internal teeth of the internal gear and the external teeth of the external gear, and the pump chamber increases the volume in the suction area space by the rotation of both gears to draw in liquid from the suction port and decreases the volume in the discharge area space to discharge liquid to the discharge port, and both gears are recessed in one side in the axial direction to form an annular recess, and the recess has multiple beams with gaps in the circumferential direction, and each beam divides the annular recess in the circumferential direction. Therefore, since both gears have multiple beams between the discharge port and the suction port, the multiple beams can suppress the leakage of liquid from the discharge port to the suction port to the multiple beams, and the leakage from the discharge port to the suction port can be reduced and the decrease in volume efficiency can be suppressed. In addition, both gears can be formed with recesses to reduce weight. In addition, since both gears have multiple beams in the recesses, the strength can be improved.

In the invention described in claim 1, the gears have flat sides facing one side, and the pump housing has flat one sliding contact surface where the one side of the gears slides, and the suction port and the discharge port are opened on the other sliding contact surface where the other side of the gears slide. Therefore, the flat other side of the gears slides on the other sliding contact surface of the pump housing where the suction port and the discharge port are opened, so that the suction port and the discharge port are not exposed to the recesses formed in the one side of the gears, and leakage from the discharge port to the suction port can be further reduced, and the decrease in volumetric efficiency can be further suppressed. In addition, the recess located in the discharge area space has an intermediate pressure lower than the pressure of the discharge port, and the recess located in the suction area space has an intermediate pressure higher than the pressure of the suction port. Therefore, the pressure of the recess located in the discharge area space and the pressure of the discharge port act on both gears in the axial direction, and the pressure of the recess located in the suction area space and the pressure of the suction port act on both gears in the axial direction, so that the gears can be approximately pressure balanced in the axial direction.

In the invention described in claim 2 , both gears are made of synthetic resin, which makes it possible to further reduce the weight of both gears.

3 is a cross-sectional view of the internal gear pump according to one embodiment of the present invention taken along line AA in FIG. 2. 2 is a cross-sectional view taken along line BB in FIG. 1. FIG. 2 is a cross-sectional view corresponding to FIG. 1 of another embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In Fig. 1 and Fig. 2, 1 denotes a pump body, which forms a bottomed accommodation hole 2. 3 denotes a cover member, which is attached to the pump body 1 so as to close the opening of the accommodation hole 2. The pump body 1 and the cover member 3 are made of metal, and the pump body 1 and the cover member 3 together form a pump housing 4. 5 denotes a ring-shaped internal gear, which has eight internal teeth 5A, and is rotatably accommodated in the accommodation hole 2. 6 denotes an external gear, which has seven external teeth 6A that mesh internally with the internal teeth 5A, and is eccentrically accommodated inside the internal gear 5. Both gears 5 and 6 are molded products of synthetic resin. One side surface 5B in the axial direction of the internal gear 5 and one side surface 6B of the external gear 6 are capable of sliding against the bottom surface of the accommodation hole 2, and this bottom surface is formed flat as one sliding contact surface 4A of the pump housing 4.

The gears 5, 6 have recesses 5C, 6C formed by axially recessing one side 5B, 6B. The recess 5C formed in the internal gear 5 is annular, with the outer circumference being slightly smaller in diameter than the outer circumference of the internal gear 5. The inner circumference of the recess 5C is shaped to follow the internal teeth 5A and is slightly larger than the internal teeth 5A. The axial depth of the recess 5C is slightly smaller than the width of the internal gear 5. The internal gear 5 has an outer peripheral thin portion 5D on the outer circumference of the recess 5C, an inner peripheral thin portion 5E on the inner circumference of the recess 5C, and a bottom thin portion 5F on the bottom of the recess 5C, with the thicknesses of the thin portions 5D, 5E, and 5F being approximately the same.

5G is a beam formed in the recess 5C, and eight of them are provided at equal intervals in the circumferential direction. Each beam 5G is formed radially outward from the radial center of the internal gear 5, connecting between each tooth tip of the internal teeth 5A in the inner peripheral thin portion 5E and the outer peripheral thin portion 5D, dividing the recess 5C into eight in the circumferential direction. The axial width dimension of each beam 5G is approximately the same as the axial depth dimension of the recess 5C, and the thickness dimension is approximately the same as the thickness dimension of each thin portion 5D, 5E, 5F.

The recess 6C formed in the external gear 6 is formed in an annular shape, and the outer circumference is shaped to follow the external teeth 6A and is slightly smaller than the external teeth 6A. The inner circumference of the recess 6C is larger in diameter than the through hole 7 that is formed to penetrate the axial direction from the radial center. The axial depth dimension of the recess 6C is slightly smaller than the width dimension of the external gear 6. The external gear 6 has an outer peripheral thin-walled portion 6D formed on the outer circumference of the recess 6C, a boss portion 6E formed on the inner circumference of the recess 6C, and a bottom thin-walled portion 6F formed on the bottom surface of the recess 6C. The through hole 7 is approximately D-shaped in vertical section, and a drive shaft 8 with a vertical section of the tip end approximately D-shaped is fitted into it. The drive shaft 8 is sealed with a seal member 9 arranged in the pump body 1, and drives the external gear 6 to rotate.

6G is a beam formed in the recess 6C, and seven of them are provided at equal intervals in the circumferential direction. Each beam 6G is formed radially outward from the radial center of the external gear 6, connecting between the boss portion 6E and each tooth tip of the external teeth 6A in the outer peripheral thin portion 6D, dividing the recess 6C into seven in the circumferential direction. The axial width dimension of each beam 6G is approximately the same as the axial depth dimension of the recess 6C, and the thickness dimension is approximately the same as the thickness dimension of each thin portion 6D, 6F.

The gears 5 and 6 have flat sides 5H and 6H that face the side surfaces 5B and 6B. The other side surfaces 5H and 6H of the gears 5 and 6 are in sliding contact with the side surface of the cover member 3 that closes the opening of the receiving hole 2, and this side surface is the other sliding surface 4B of the pump housing 4, and is formed flat. S is the suction area space, and P is the discharge area space, which are provided between the gears 5 and 6, respectively. 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. T is 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 the volume of the suction area space S increases as the gears 5 and 6 rotate, while the volume of the discharge area space P decreases.

10 is an intake port that communicates with the intake area space S, and opens into a semicircular recess formed in the other sliding surface 4B of the pump housing 4. 11 is an intake flow passage that connects to the intake port 10, and is formed in the cover member 3, and flows the liquid that is sucked in from the low pressure side. 12 is a discharge port that communicates with the discharge area space P, and is formed into a semicircular recess formed in the other sliding surface 4B of the pump housing 4, and opens in a position symmetrical in the radial direction to the intake port 10. 13 is a discharge flow passage that connects to the discharge port 12, and is formed in the cover member 3, and flows the liquid that is discharged to the load side.

In each of the eight circumferentially divided recesses 5C, a small amount of liquid discharged to the discharge port 12 is introduced into the discharge area space P between the tip of the inner thin portion 5E and one sliding surface 4A of the pump housing 4, and in the suction area space S, a small amount of liquid inside is discharged to the suction port 10 between the tip of the inner thin portion 5E and one sliding surface 4A of the pump housing 4. Therefore, in each of the eight circumferentially divided recesses 5C, the discharge area space P has an intermediate pressure slightly lower than the pressure of the discharge port 12, and in the suction area space S, the suction area space S has an intermediate pressure slightly higher than the pressure of the suction port 10.

In the discharge area space P, each of the seven circumferentially divided recesses 6C introduces a small amount of liquid to be discharged to the discharge port 12 into the discharge area space P between the tip of the thin outer periphery 6D and one sliding surface 4A of the pump housing 4, and in the suction area space S, a small amount of liquid inside the discharge area space P is discharged to the suction port 10 between the tip of the thin outer periphery 6D and one sliding surface 4A of the pump housing 4. Therefore, in the discharge area space P, each of the seven circumferentially divided recesses 6C has an intermediate pressure slightly lower than the pressure of the discharge port 12, and in the suction area space S, an intermediate pressure slightly higher than the pressure of the suction port 10.

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 inscribed in mesh with the external gear 6, is rotated, and liquid flows from the low pressure side through the suction passage 11, is sucked into the suction area space S through the suction port 10, transported to the discharge area space P, and is discharged through the discharge passage 13 from the discharge port 12.

At this time, a small amount of liquid (a small amount) flowing from the discharge area space P through the discharge port 12 is introduced into the recess 5C located in the discharge area space P through the gap between the tip of the inner thin portion 5E of the internal gear 5 and one sliding contact surface 4A of the pump housing 4, and is also introduced into the recess 6C located in the discharge area space P through the gap between the tip of the outer thin portion 6D of the external gear 6 and one sliding contact surface 4A of the pump housing 4. Therefore, the recesses 5C and 6C located in the discharge area space P are at an intermediate pressure that is slightly lower than the pressure of the discharge port 12.

A small amount of liquid in the recess 5C located in the suction area space S is guided from the suction area space S to the suction port 10 through the gap between the tip of the inner thin portion 5E and one sliding contact surface 4A of the pump housing 4. A small amount of liquid in the recess 6C located in the suction area space S is guided to the suction port 10 through the gap between the tip of the outer thin portion 6D and one sliding contact surface 4A of the pump housing 4. Therefore, the recesses 5C and 6C located in the suction area space S have an intermediate pressure that is slightly higher than the pressure of the suction port 10.

In this operation, the internal teeth 5A of the internal gear 5 and the external teeth 6A of the external gear 6 define a pump chamber T, and the pump chamber T increases the volume in the suction area space S by the rotation of both gears 5 and 6 to draw in liquid from the suction port 10 and decreases the volume in the discharge area space P to discharge liquid to the discharge port 12, and one side surface 5B, 6B of both gears 5 and 6 is recessed in the axial direction to form annular recesses 5C, 6C, and the recesses 5C, 6C have gaps in the circumferential direction to form a plurality of beams 5G, 6G, and each beam 5G, 6G divides the annular recesses 5C, 6C in the circumferential direction. Therefore, since both gears 5 and 6 have a plurality of beams 5G, 6G between the discharge port 12 and the suction port 10, the leakage of liquid leaking from the discharge port 12 to the suction port 10 can be suppressed by the plurality of beams 5G, 6G to the suction port 10, and the leakage from the discharge port 12 to the suction port 10 can be reduced and a decrease in volumetric efficiency can be suppressed. The gears 5, 6 are lighter in weight by forming recesses 5C, 6C, and the gears 5, 6 are stronger by forming a plurality of beams 5G, 6G in the recesses 5C, 6C.

Moreover, the gears 5, 6 have flat side surfaces 5H, 6H facing the side surfaces 5B, 6B, and the pump housing 4 has flat first sliding contact surface 4A where the side surfaces 5B, 6B of the gears 5, 6 slide, and the suction port 10 and the discharge port 12 are opened on the second sliding contact surface 4B where the side surfaces 5H, 6H of the gears 5, 6 slide. Therefore, the flat second side surfaces 5H, 6H of the gears 5, 6 slide against the second sliding contact surface 4B of the pump housing 4 where the suction port 10 and the discharge port 12 are opened, so that the suction port 10 and the discharge port 12 are not exposed to the recesses 5C, 6C recessed in the side surfaces 5B, 6B of the gears 5, 6, and leakage from the discharge port 12 to the suction port 10 can be further reduced, and a decrease in volumetric efficiency can be further suppressed .

In addition, both gears 5 and 6 are made of synthetic resin. This allows the gears 5 and 6 to be made even lighter.

The recesses 5C and 6C located in the discharge area space P have an intermediate pressure slightly lower than the pressure of the discharge port 12, and the recesses 5C and 6C located in the suction area space S have an intermediate pressure slightly higher than the pressure of the suction port 10. Therefore, the pressures of the recesses 5C and 6C located in the discharge area space P and the pressure of the discharge port 12 act in opposing directions on both gears 5 and 6, and the pressures of the recesses 5C and 6C located in the suction area space S and the pressure of the suction port 10 act in opposing directions on both gears 5 and 6, so that the gears 5 and 6 can be well pressure balanced in the axial direction.

FIG. 3 shows another embodiment of the present invention. The same parts as those in the first embodiment are designated by the same reference numerals and their explanation is omitted, and only the different parts will be explained.
Eight beams 14 are formed in the recess 5C of the internal gear 5 at equal intervals in the circumferential direction, connecting the tooth bottoms of the internal teeth 5A in the inner thin portion 5E and the outer thin portion 5D, dividing the recess 5C into eight in the circumferential direction. Seven beams 15 are formed in the recess 6C of the external gear 6 at equal intervals in the circumferential direction, connecting the boss portion 6E and the tooth bottoms of the external teeth 6A in the outer thin portion 6D, dividing the recess 6C into seven in the circumferential direction. The drive shaft 16 that rotates the external gear 6 has a vertical cross section at its tip that is approximately two-face shaped. The through hole 17 into which the drive shaft 16 is fitted has a vertical cross section that is approximately two-face shaped.

In operation, the external gear 6 is rotated by the drive shaft 16, and liquid is sucked in through the suction port 10 and discharged through the discharge port 12, in a manner similar to that of the first embodiment.

At this time, the recesses 5C, 6C located in the discharge area space P have an intermediate pressure that is slightly lower than the pressure of the discharge port 12. Also, the recesses 5C, 6C located in the suction area space S have an intermediate pressure that is slightly higher than the pressure of the suction port 10. Therefore, the pressures of the recesses 5C, 6C located in the discharge area space P and the pressure of the discharge port 12 act in opposing axial directions on both gears 5, 6, and the pressures of the recesses 5C, 6C located in the suction area space S and the pressure of the suction port 10 act in opposing axial directions on both gears 5, 6, so that the gears 5, 6 can be well pressure balanced in the axial direction.

In this operation, the recesses 5C, 6C are formed with a plurality of beams 14, 15 with gaps in the circumferential direction, and each beam 14, 15 divides the annular recesses 5C, 6C in the circumferential direction. Therefore, since both gears 5, 6 have a plurality of beams 14, 15 between the discharge port 12 and the suction port 10, the plurality of beams 14, 15 can suppress the leakage of liquid leaking from the discharge port 12 to the suction port 10 to the suction port 10, and the leakage from the discharge port 12 to the suction port 10 can be reduced and the decrease in volume efficiency can be suppressed. Furthermore, the recesses 5C, 6C are formed in both gears 5, 6, so that the strength can be improved.

Also, substantially similar to the first embodiment, the suction port 10 and the discharge port 12 are opened on the other sliding contact surface 4B (shown in FIG. 2) of the pump housing 4 with which the flat other side surfaces 5H, 6H (shown in FIG. 2) of both gears 5, 6 slide. Therefore, the suction port 10 and the discharge port 12 are not exposed to the recesses 5C, 6C recessed into the one side surfaces 5B, 6B (shown in FIG. 2) of both gears 5, 6, so that leakage from the discharge port 12 to the suction port 10 can be further reduced and the decrease in volumetric efficiency can be further suppressed . Also , because both gears 5, 6 are made of synthetic resin, the weight of both gears 5, 6 can be further reduced.

In the above-mentioned embodiments, the beams 5G and 6G are connected to the tooth tips of the internal teeth 5A and the external teeth 6A, and the beams 14 and 15 are connected to the tooth bottoms of the internal teeth 5A and the external teeth 6A, but the beams may be connected to both the tooth tips and the tooth bottoms of the internal teeth and the external teeth. In addition, the pump housing 4 is composed of the pump body 1 and the cover member 3, but the pump housing may be composed of three members: a first member that penetrates and forms a housing hole that houses both gears, a second member that is attached to one side of the first member and against which one side of both gears slide, and a third member that is attached to the other side of the first member and against which the other side of both gears slide. In addition, the through holes 7 and 17 that fit the drive shafts 8 and 16 that rotate the external gear 6 are formed to be approximately D-shaped or approximately two-faced in cross section, but it goes without saying that the through holes may be formed to be spline-shaped in cross section.

2: Accommodating hole 4: Pump housing 4A: One sliding surface 4B: Other sliding surface 5: Internal gear 5A: Internal teeth 5B, 6B: One side surface 5C, 6C: Recess 5G, 6G, 14, 15: Beam 5H, 6H: Other side surface 6: External gear 6A: External teeth 10: Suction port 12: Discharge port S: Suction area space P: Discharge area space T: Pump chamber

Claims (2)

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 internally mesh with the internal teeth of the internal gear is eccentrically accommodated inside the internal gear, and an suction area space is formed between both gears in a region where the meshing gap between both teeth increases as both gears rotate, and the suction area space is formed in communication with a suction 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 suction area space increases as both gears rotate to draw in liquid from the suction port and the volume of the discharge area space decreases to discharge liquid to the discharge port, and one side of both gears is recessed in the axial direction to form an annular recess, a pump housing having a plurality of beams formed with gaps in the circumferential direction, each beam dividing an annular recess in the circumferential direction, one side surface of each of the gears being flat and opposing the other side surface of the gears, a pump housing having a flat sliding surface on which one side surfaces of the gears slide and an intake port and a discharge port being opened in the other sliding surface on which the other side surfaces of the gears slide, and each of the circumferentially divided recesses of the gears introduces , in a discharge area space, a portion of the liquid discharged to the discharge port through the gap between the tip of the thin-walled portion forming the recess and the one sliding surface of the pump housing, thereby creating an intermediate pressure lower than the pressure of the discharge port, and, in a suction area space , a portion of the liquid inside is discharged through the gap between the tip of the thin-walled portion forming the recess and the one sliding surface of the pump housing, thereby creating an intermediate pressure higher than the pressure of the suction port. 2. The internal gear pump according to claim 1 , wherein both of said gears are made of synthetic resin.

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