JP2018003599A - Internal gear pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal gear pump capable of effectively reducing pressure rise and suppressing discharge pulsation while facilitating the design.SOLUTION: The internal gear pump includes an outer rotor having internal teeth, an inner rotor having external teeth which engage with the internal teeth and the number of which is one less than that of the internal teeth, and rotatably arranged inside the outer rotor to form between the outer rotor and itself a plurality of pump chambers to be repetitively expanded and contracted, and a pump housing formed with a case part having a holding recess rotatably holding the outer rotor and a cover part closing the opening of the holding recess, and provided with a suction port for sucking fluid into the pump chamber and a discharge port for discharging the fluid from the pump chamber. In the pump housing, an expansion chamber is provided whose capacity is increased according to pressure rise in the pump chamber in a capacity compression process for the pump chamber to allow part of the fluid to flow thereinto and is reduced according to pressure drop in the pump chamber in a discharge process to allow the fluid flowing thereinto to flow out to the pump chamber.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an internal gear pump used for lubricating oil or the like. Specifically, the present invention relates to a technical field of an internal gear pump that performs a pump operation by changing a volume of a plurality of pump chambers formed by an outer rotor and an inner rotor.

In a power mechanism such as an engine or a transmission, it is common to lubricate oil or the like for smooth operation and protection. Such a power mechanism includes an oil pump for supplying oil to each part.
There are various types of oil pumps, including an internal gear pump. The internal gear pump performs a pump operation by changing the volume of a plurality of spaces (pump chambers) formed by eccentrically arranging an inner rotor having external teeth and an outer rotor having internal teeth.
In the internal gear pump, there is a problem that the driving torque of the pump increases as the pressure in the pump chamber rises during the compression process of the pump chamber.
Patent Document 1 discloses a configuration in which a groove extending from a starting end of a discharge port (discharge port) to a suction port (suction port) side is provided in a pump housing (casing) in order to reduce pressure rise and suppress discharge pulsation. .

JP 2003-214356 A

  However, it may be necessary to lengthen the groove in order to obtain the effect of reducing the pressure rise and suppressing the discharge pulsation by forming the groove in the pump housing. It is difficult to design a long groove in a limited space between the suction port and the discharge port.

  In view of the above situation, an object of the present invention is to propose an internal gear pump that can achieve an effect of reducing pressure rise and suppressing discharge pulsation while facilitating design.

The internal gear pump according to the present invention includes an outer rotor having internal teeth, an external tooth that engages with the internal teeth and has one fewer tooth than the internal teeth, and rotates inside the outer rotor. An inner rotor that forms a plurality of pump chambers that are freely arranged and repeats expansion and contraction with the outer rotor, a case portion in which a holding recess is formed in which the outer rotor is rotatably held, and the holding A pump housing provided with a suction port for sucking fluid into the pump chamber and a discharge port for discharging fluid from the pump chamber. The volume increases in response to a pressure increase in the pump chamber in the process of compressing the volume of the pump chamber, a part of the fluid flows in, and the volume increases in response to a pressure drop in the pump chamber in the discharge process. In which expansion chamber is provided for discharging the fluid which has little flow into the pump chamber.
As a result, the volume of the expansion chamber increases or decreases according to the pressure change in the pump chamber.

In the internal gear pump described above, a part of the wall portion constituting the expansion chamber may be a movable wall that can be moved by an elastic body.
Thereby, the volume of the expansion chamber can be made variable with a simple structure.

In the internal gear pump described above, the expansion chamber may be provided in each of the case portion and the cover portion.
Thereby, the volume of an expansion chamber increases more.

The opening shape of the expansion chamber in the internal gear pump described above may be a shape in which the width of the outer rotor in the radial direction is longer than the width in the direction perpendicular to the radial direction.
As a result, when the width in the direction orthogonal to the radial direction of the outer rotor is constant in the opening shape of the expansion chamber, the opening area of the suction port and the volume of the expansion chamber are increased as compared with the circular shape.

The opening shape of the expansion chamber in the internal gear pump described above may be an elliptical shape.
As a result, when the width in the direction orthogonal to the radial direction of the outer rotor is constant in the opening shape of the expansion chamber, the opening area of the suction port and the volume of the expansion chamber are increased as compared with the circular shape.

In the internal gear pump described above, the suction port and the discharge port may be provided in the case portion and the cover portion, respectively.
Thereby, the suction and discharge to the pump chamber are smoothly performed.

  ADVANTAGE OF THE INVENTION According to this invention, the internal gear pump which can acquire the effect of reduction of a pressure rise and suppression of a discharge pulsation can be proposed, aiming at the design simplicity.

It is a disassembled perspective view of the trochoid type pump of an embodiment of the invention. It is a perspective view of a rotor unit. It is a perspective view which shows a part of case part in a cross section. It is a top view which shows the state by which the rotor unit is arrange | positioned at the case part. It is a top view for demonstrating a mode that one focused pump chamber moves. It is a top view for demonstrating a mode that one focused pump chamber moves. It is a top view for demonstrating a mode that one focused pump chamber moves. It is sectional drawing which shows typically the positional relationship of a pump chamber and an expansion chamber. It is a top view for demonstrating a mode that one focused pump chamber moves. It is sectional drawing which shows typically the positional relationship of a pump chamber and an expansion chamber. It is a top view for demonstrating a mode that one focused pump chamber moves. It is sectional drawing which shows typically the positional relationship of a pump chamber and an expansion chamber. It is a top view for demonstrating a mode that one focused pump chamber moves. It is sectional drawing which shows typically the positional relationship of a pump chamber and an expansion chamber. It is a figure for demonstrating the position of a pump chamber. It is a graph which shows the relationship between the position of a pump chamber, and the pressure of the fluid in a pump chamber. It is sectional drawing for demonstrating the trochoid type pump in a 2nd example. It is a top view for demonstrating the trochoid type pump in the 3rd example. It is a top view for demonstrating the trochoid type pump in the 3rd example.

EMBODIMENT OF THE INVENTION Below, the form for implementing the internal gear pump of this invention is demonstrated with reference to an accompanying drawing.
An example of the internal gear pump is a trochoid pump having a trochoid tooth pattern.

<1. Configuration of Trochoid Pump>
A configuration of a trochoid pump as an example of the internal gear pump in the first embodiment will be described.
In addition, the vertical direction described in the following description is not intended for the vertical direction when used or the vertical direction when attached, but is for convenience of description.
FIG. 1 is an exploded perspective view of the trochoid pump 1.

  The trochoid pump 1 includes an outer rotor 2, an inner rotor 3, a pump housing 4, and a pump shaft 5 for rotating the inner rotor 3.

The outer rotor 2 has a cylindrical shape having a through hole 2a at the center. A plurality of internal teeth 2b are formed on the surface forming the through hole 2a.
In the present configuration example, nine inner teeth 2 b are formed on the outer rotor 2.

The inner rotor 3 is formed with a shaft hole 3a through which the pump shaft 5 is inserted at the center, and a plurality of external teeth 3b are continuously formed in the circumferential direction on the outer peripheral surface. The number of outer teeth 3b of the inner rotor 3 is one less than the number of inner teeth 2b of the outer rotor 2, and the number of outer teeth 3b is eight in this configuration example.
In addition, a recess or a protrusion is provided on the peripheral surface of the shaft hole 3 a of the inner rotor 3, and a protrusion or a recess that engages with the recess or the protrusion is provided on the peripheral surface of the pump shaft 5. It is also possible to prevent idling in the hole 3a.

  The inner rotor 3 is eccentric with respect to the outer rotor 2 and is disposed in the through hole 2a. The outer rotor 2 and the inner rotor 3 are combined to form a rotor unit 6.

FIG. 2 is a view showing a rotor unit 6 in which the outer rotor 2 and the inner rotor 3 are combined. As shown in FIG. 2, a plurality of pump chambers 7 are formed in the rotor unit 6 between the outer rotor 2 and the inner rotor 3.
The plurality of pump chambers 7 are separated in the circumferential direction by the inner teeth 2b of the outer rotor 2 and the outer teeth 3b of the inner rotor 3, and are independent chambers.

The pump housing 4 includes a case portion 8 and a cover portion 9 (see FIG. 1).
The case portion 8 includes a cylindrical holding recess 10 that is substantially the same size as the rotor unit 6 that holds the rotor unit 6, a first suction circuit 11 for sucking fluid, and for discharging the sucked fluid. A first discharge circuit 12, a plurality of attachment holes 13 for attaching the pump housing 4 to other members, and a plurality of positioning holes 14 for positioning the cover portion 9 are formed.

A first insertion hole 15 a through which the pump shaft 5 is inserted is formed in the bottom surface portion 15 of the holding recess 10. Further, the bottom 15 of the holding recess 10 has a suction port 15 b for sucking fluid from the first suction circuit 11 to the pump chamber 7 and a discharge for discharging fluid from the pump chamber 7 to the first discharge circuit 12. An outlet 15c is formed.
The suction port 15b is formed along the first insertion hole 15a over a substantially half circumference of the first insertion hole 15a.
The discharge port 15c is an opening smaller than the suction port 15b, and is formed on the substantially opposite side of the first insertion hole 15a with respect to the suction port 15b.
Furthermore, an expansion chamber 15 d is provided in the bottom surface portion 15 of the holding recess 10. The expansion chamber 15d will be described later.

  The cover portion 9 has a second insertion hole 16 through which the pump shaft 5 is inserted at a position facing the first insertion hole 15 a when assembled to the case portion 8, and a circuit following the first suction circuit 11 of the case portion 8. A second suction circuit 17, a second discharge circuit 18 that is a circuit continuing from the first discharge circuit 12 of the case portion 8, a plurality of mounting holes 19 for mounting the pump housing 4 to other members, A substantially cylindrical positioning convex portion 20 to be inserted into the positioning hole 14 is formed at a position corresponding to the positioning hole 14 when assembled to the case portion 8.

Further, the surface of the cover portion 9 that faces the bottom surface portion 15 of the holding recess 10 when the cover portion 9 is assembled to the case portion 8 is a ceiling surface 21.
The pump chamber 7 is a space surrounded by the outer rotor 2, the inner rotor 3, the bottom surface portion 15 of the case portion 8, and the ceiling surface 21 of the cover portion.

  By inserting the positioning convex portion 20 of the cover portion 9 into the positioning hole 14 of the case portion 8, the cover portion 9 is positioned with respect to the case portion 8. In addition, the convex part for positioning may be formed in the case part 8, and the hole for positioning may be formed in the cover part 9. FIG.

The expansion chamber 15d will be described with reference to FIG.
3 is a cross-sectional view of the suction port 15b, the discharge port 15c, and the expansion chamber 15d provided in the bottom surface portion 15 of the holding recess 10. As shown in FIG.

The expansion chamber 15d shown in FIG. 3 is a cylindrical hole having a variable volume. The inner wall of the expansion chamber 15d is a wall portion 22, and the bottom portion of the expansion chamber 15d, which is a part of the wall portion 22, is a movable wall 23 that is urged toward the opening direction of the expansion chamber 15d by an elastic body. Yes.
A surface constituting a part of the inner wall of the expansion chamber 15d in the movable wall 23 is a pressing surface 23a that presses the fluid flowing into the expansion chamber 15d in the opening direction.

In addition, various things can be considered as an elastic body. The elastic body in this example is a coil spring 24 as an example.
In a state where the coil spring 24 has a free length, the pressing surface 23 a of the movable wall 23 is located on the same plane as the surface of the bottom surface portion 15 of the holding recess 10. As another means for making the pressing surface 23a and the surface of the bottom surface portion 15 flush with each other, the free length of the coil spring 24 is made longer than the depth of the expansion chamber 15d, and the pressing surface 23a is The movable wall 23 may be regulated by the rotor unit 6 or other members so as not to move to the ceiling surface 21 side from the surface.

As described above, the names of the bottom surface portion 15 and the ceiling surface 21 are given for convenience of explanation, and are not intended for the vertical direction when using the trochoid pump 1 or the vertical direction when mounting it. Absent.
For example, when the trochoidal pump 1 is in use, the ceiling surface 21 may be a surface facing upward or a surface facing sideways. In other words, the case portion 8 may be used in combination so as to be positioned above the cover portion 9 or may be used such that the holding recess 10 of the case portion 8 is opened to the side. .

<2. Operation of Trochoid Pump>
The operation of the trochoid pump in this example will be described with reference to FIGS.
FIG. 4 shows a state where the outer rotor 2, the inner rotor 3, the pump shaft 5, and the case portion 8 are viewed from the opening direction of the holding recess 10.
As illustrated, a plurality of pump chambers 7 are formed between the outer rotor 2 and the inner rotor 3.

  When the pump shaft 5 is rotated in the rotation direction R, the inner rotor 3 rotates in the same direction. When the inner rotor 3 rotates, the inner teeth 2b and a part of the outer teeth 3b are engaged, so that a rotational force is applied to the outer rotor 2 and the outer rotor 2 also rotates in the same direction.

  As the pump shaft 5, the inner rotor 3, and the outer rotor 2 rotate, the pump chamber 7 moves along the inner peripheral edge of the outer rotor 2 while repeating expansion and contraction. At that time, each pump chamber 7 communicates with the suction port 15b, the discharge port 15c, and the expansion chamber 15d of the case portion 8 as appropriate, so that the pump operation is performed.

Specifically, the expansion and contraction states of the pump chamber 7 will be described by paying attention to one pump chamber 7A among the plurality of pump chambers 7 (FIGS. 5 to 14).
5 to 14, the outer rotor 2, the inner rotor 3 (or the rotor unit 6), the pump chamber 7A, and the suction port 15b, the discharge port 15c, and the expansion chamber 15d of the case portion 8 are included. Some of these are illustrated as appropriate.
In each figure, the pump chamber 7A of interest is indicated by a hatched area.
Moreover, the part shown as the rotor unit 6 in the figure has shown that it is any member of the outer rotor 2 and the inner rotor 3. FIG.

  FIG. 5 is a view showing the outer rotor 2, the inner rotor 3, and the holding recess 10 of the case portion 8. The pump chamber 7A shown in FIG. 5 is in a state in which the volume starts to expand from a state where the volume is the smallest and starts to communicate with the suction port 15b.

When the inner rotor 3 is rotated from the state shown in FIG. 5, the state shown in FIG. 6 is obtained.
The state shown in FIG. 6 is a state in which the volume of the pump chamber 7A expands further than the state shown in FIG. 5, and the fluid is sucked into the pump chamber 7A from the suction port 15b.

When the inner rotor 3 is rotated from the state shown in FIG. 6, the state shown in FIG. 7 is obtained. FIG. 8 is a view schematically showing the relationship between the pump chamber 7A and the expansion chamber 15d in the state shown in FIG. 7 in a sectional view.
The state shown in FIGS. 7 and 8 is a state where the volume of the pump chamber 7A is further expanded and the volume of the pump chamber 7A is substantially maximized as compared with the state shown in FIG. This state is a state immediately before the communication state with the suction port 15b is released. Further, the pressing surface 23a of the movable wall 23 is in a state before it comes into contact with the fluid sucked into the pump chamber 7A.

When the inner rotor 3 is rotated from the state shown in FIGS. 7 and 8, the state shown in FIGS. 9 and 10 is obtained. FIG. 10 is a cross-sectional view schematically showing a part of the state shown in FIG.
9 and 10, the communication between the pump chamber 7A and the suction port 15b is eliminated, and the pump chamber 7A is in a substantially sealed state. Further, the volume of the pump chamber 7A starts to decrease compared to the state shown in FIGS.

  Part of the fluid that has flowed into the pump chamber 7A is in contact with the pressing surface 23a of the movable wall 23 until the pressure of the fluid in the pump chamber 7A elastically deforms the coil spring 24 via the movable wall 23. Since the height is not increased, the pressing surface 23 a of the movable wall 23 is flush with the surface of the bottom surface portion 15.

When the inner rotor 3 is further rotated from the state shown in FIGS. 9 and 10, the pressure of the fluid in the pump chamber 7A increases, and the pressing surface 23a of the movable wall 23 is pressed in the direction opposite to the opening direction of the expansion chamber 15d. Is done.
This will be specifically described with reference to FIGS. The state shown in the figure is a state immediately before the pump chamber 7A communicates with the discharge port 15c. In this state, the pump chamber 7A is sealed.
As shown in FIG. 12, due to the increase in the pressure of the fluid in the pump chamber 7A based on the decrease in the volume of the pump chamber 7A, the pressing surface 23a is pressed toward the coil spring 24 and the volume of the expansion chamber 15d increases. Thereby, the pressure of the fluid in the pump chamber 7A decreases.

  When the inner rotor 3 is rotated from the state shown in FIGS. 11 and 12, the pump chamber 7A and the discharge port 15c are in communication with each other as shown in FIGS. In this state, since the fluid in the pump chamber 7A is discharged from the discharge port 15c to the first discharge circuit 12, the pressure of the fluid in the pump chamber 7A decreases. Thereby, the coil spring 24 is elastically restored, the movable wall 23 moves to the ceiling surface 21 side of the cover portion 9, and the volume of the expansion chamber 15d becomes zero.

As described with reference to FIGS. 5 to 14, the volume of the expansion chamber 15d is increased or decreased each time the pump chamber 7 passes through the upper portion of the expansion chamber 15d.
Then, when the volume of the expansion chamber 15d increases or decreases according to the pressure of the fluid in the pump chamber 7, it is possible to prevent the fluid pressure in the pump chamber 7 from being excessively increased.

  The process in which the pressure of the fluid in the pump chamber 7 is reduced will be specifically described with reference to FIGS.

First, the expression of the position of the pump chamber 7 will be described with reference to FIG.
The pump chamber 7 moves along the inner periphery of the outer rotor 2, that is, along the outer periphery of the inner rotor 3. Therefore, an angle is used to indicate which position of the substantially central portion of the pump chamber 7 is located with respect to the rotation center of the outer rotor 2.
For example, FIG. 15 shows a state where the pump chamber 7A of interest is positioned at 45 ° with respect to the rotation center of the outer rotor 2.

Subsequently, the relationship between the position of the pump chamber 7A relative to the rotation center of the outer rotor 2 and the pressure of the fluid in the pump chamber 7A is shown in FIG.
In FIG. 16, the pressure change for the trochoid pump 1 provided with the expansion chamber 15d is indicated by a solid line, and the pressure change for the trochoid pump not provided with the expansion chamber 15d is indicated by a broken line.
As shown in the figure, the trochoidal pump 1 having the expansion chamber 15d has a reduced pressure peak of the fluid in the pump chamber 7 than the trochoid pump having no expansion chamber 15d. I understand.

<3. Second Example>
A trochoid pump 1A as a second example will be described with reference to FIG.
In the trochoidal pump 1A, not only the suction port 15b, the discharge port 15c and the expansion chamber 15d are provided in the bottom surface portion 15 of the arrangement recess 10 of the case portion 8, but also an opening is formed in the ceiling surface 21 of the cover portion 9. A suction port 21a, a discharge port 21b, and an expansion chamber 21c are provided.
The opening shapes of the suction port 21a, the discharge port 21b, and the expansion chamber 21c of the cover part 9 are the same as the suction port 15b, the discharge port 15c, and the expansion chamber 15d of the case unit 8, respectively. The opening of the expansion chamber 21c is provided to face the opening of the expansion chamber 15d.
Although not shown, the expansion chamber 21c is provided with a movable wall 23 and a coil spring 24 as in the expansion chamber 15d.

As shown by the arrow in FIG. 17, the suction port 21 a communicates with the second suction circuit 17. Further, the discharge port 21 b communicates with the second discharge circuit 18.
Therefore, when the fluid is sucked into the pump chamber 7, the fluid flows from the second suction circuit 17 through the suction port 21 a and also flows from the suction port 15 b through the first suction circuit 11. The When the pressure of the fluid in the pump chamber 7 increases, a part of the fluid flows into the two expansion chambers 15d and 21c. When fluid is discharged from the pump chamber 7, fluid is discharged from the discharge port 21 b to the second discharge circuit 18, and fluid is discharged from the discharge port 15 c to the first discharge circuit 12. At this time, the fluid flowing into the two expansion chambers 15d and 21c is also discharged from the discharge holes 15c and 21b. Thereby, fluids, such as oil, are supplied to each required part, for example.

  A smooth suction operation is performed by increasing the area of the opening for sucking the fluid into the pump chamber 7. Further, since the area of the opening for discharging the fluid from the pump chamber 7 is increased, a smooth discharge operation is performed.

In order to reduce the pressure of the fluid in the pump chamber 7, it is desirable that the volume of the expansion chamber 15d is large.
However, the opening area of the expansion chamber 15d (particularly the width of the opening in the direction perpendicular to the radial direction of the outer rotor 2) cannot be increased beyond a predetermined value. This is because the suction port 15b and the discharge port 15c may communicate with each other through the expansion chamber 15d. Thus, in order to increase the volume of the expansion chamber 15d, it is conceivable to increase the depth of the expansion chamber 15d. However, if the depth is increased, the case portion 8 may be increased in size. is there.

  In the trochoid pump 1A in the second example, the expansion chamber 21c is provided not only in the case portion 8 but also in the cover portion 9, so that the case portion 8 and the cover portion 9 do not increase in size. The effect of reducing the pressure of the fluid can be enhanced.

<4. Third Example>
A trochoid pump 1B as a third example will be described with reference to FIG.
The trochoid pump 1B is different from the trochoid pumps 1 and 1A described above in the opening shape of the expansion chamber 15d.
Specifically, as shown in FIG. 19, the opening shape of the expansion chamber 15d is an elliptical shape, and the width W1 in the radial direction of the outer rotor 2 in the elliptical shape is larger than the width W2 in the direction orthogonal to the width W1. Has also been long.
For example, the rotation center of the outer rotor 2 is configured to be positioned on an extension line of an elliptical long axis that is an opening shape of the expansion chamber 15d.
Although not shown, the shape of the pressing surface 23a of the movable wall 23 is also the same elliptical shape.

In the trochoid pump 1B of the third example, the length of the width W2 and the depth of the expansion chamber 15d in the elliptical shape that is the opening shape of the expansion chamber 15d are the same as those of the other trochoid pumps 1 and 1A described above. In this case, the volume of the expansion chamber 15d can be increased.
That is, the effect of reducing the pressure of the fluid in the pump chamber 7 can be further enhanced.

  The same effect can be obtained even with the trochoid pump 1B provided with the expansion chamber 21c instead of the expansion chamber 15d and the trochoid pump 1B provided with both the expansion chambers 15d and 21c. it can.

  Note that the opening shape of the expansion chamber 15d in which the width W1 is longer than the width W2 may be other than an ellipse, for example, an oval shape other than an ellipse shape or a rectangular shape.

<5. Summary>
As shown in each example, the trochoidal pump 1 (1A, 1B) of the embodiment has an outer rotor 2 having internal teeth 2b, and engages with the internal teeth 2b and has more teeth than the internal teeth 2b. An inner rotor 3 having one outer tooth 3b, rotatably disposed inside the outer rotor 2, and forming a plurality of pump chambers 7 (7A) that repeat expansion and contraction with the outer rotor 2; A suction port 15b (intake of fluid into the pump chamber 7) is formed by a case portion 8 having a holding recess 10 in which the outer rotor 2 is rotatably held, and a cover portion 9 that closes the opening of the holding recess 10. 21a) and a pump housing provided with a discharge port for discharging fluid from the pump chamber 7. The pump housing 6 has a volume corresponding to the pressure increase in the pump chamber 7 during the compression process of the volume of the pump chamber 7. Increases Part of the body flows, extend chamber 15d the volume depending on the pressure drop in the pump chamber 7 to flow out the reduced inflow fluid into the pump chamber 7 (21c) are provided in the discharge process.
Thereby, the volume of the expansion chamber 15d increases / decreases according to the pressure change of the pump chamber 7.
Therefore, since the pressure increase in the process of compressing the volume of the pump chamber 7 can be reduced, the driving torque of the pump and the discharge pulsation can be reduced.
In addition, the generation of cavitation can be suppressed and the discharge pulsation can be reduced by reducing the pressure rise in the compression process, so that the pump sound can be reduced.
Furthermore, by reducing the pressure increase in the compression process, it is possible to suppress a decrease in the discharge amount due to the fluid leaking between the rotor unit 6 and the pump housing 4 through the gap between the parts in the compression process. Can do.
According to the trochoid pump 1 of the embodiment, since it is not necessary to provide a long groove or the like in the pump housing 4 (the case portion 8 or the cover portion 9) in order to reduce the pressure rise, the design is simplified and the number of processing steps is reduced. Reduction is planned.

Further, as described in the configuration of the trochoid pump 1, a part of the wall portion 22 configuring the expansion chamber 15d (21c) may be a movable wall 23 that can be moved by an elastic body (for example, a coil spring 24). .
Thereby, the volume of the expansion chamber can be made variable with a simple structure.

Furthermore, as described in the second example, the case portion 8 and the cover portion 9 may be provided with expansion chambers 15d (21c), respectively.
Thereby, the volume of the expansion chamber 15d further increases.
Therefore, the pressure rise in the pump chamber 7 (7A) and the expansion chamber 15d can be further reduced.

Furthermore, as described in the third example, the opening shape of the expansion chamber 15d may be such that the width W1 in the radial direction of the outer rotor 2 is longer than the width W2 in the direction orthogonal to the radial direction. Good.
Thus, when the width of the expansion chamber opening shape is constant in the direction orthogonal to the radial direction of the outer rotor, the opening area of the suction port 15b (21a) and the volume of the expansion chamber 15d are larger than the circular shape. To increase.
Therefore, the pressure rise in the pump chamber 7 and the expansion chamber 15d can be reduced.

In addition, as described in the third example, the opening shape of the expansion chamber 15d (21c) may be an elliptical shape.
Thus, when the width of the expansion chamber opening shape is constant in the direction orthogonal to the radial direction of the outer rotor, the opening area of the suction port 15b (21a) and the volume of the expansion chamber 15d are larger than the circular shape. To increase.
Therefore, the pressure rise in the pump chamber 7 (7A) and the expansion chamber 15d can be reduced.

And as demonstrated in the 2nd example, the suction port 15b (21a) and the discharge port 15c (21b) may be provided in the case part 8 and the cover part 9, respectively.
Thereby, the suction and discharge of the fluid to the pump chamber 7 (7A) are performed smoothly.
Therefore, the pump sound can be further reduced.

  The configuration in which the movable wall 23 is moved by an elastic body such as the coil spring 24 is an example, and the movable wall 23 may be configured to move using other means. For example, the movable wall 23 may be moved by an actuator.

  In the process of increasing the pressure of the fluid in the pump chamber 7, it is desirable that the center of the pressing surface 23a of the movable wall 23 is in contact with the fluid. Thereby, when the movable wall 23 moves to the coil spring 24 side, the center of the pressing surface 23a is pressed, and the movable wall 23 is easily moved, so that the pressure of the fluid in the pump chamber 7 is reduced. It is easy to show the effect.

1, 1A, 1B ... Trochoid pump, 2 ... Outer rotor, 2b ... Inner teeth, 3 ... Inner rotor, 3b ... Outer teeth, 4 ... Pump housing, 7, 7A ... Pump chamber, 8 ... Case part, 9 ... Cover , 10 ... holding recess, 15b ... suction port, 15c ... discharge port, 15d ... expansion chamber, 21a ... suction port, 21b ... discharge port, 21c ... expansion chamber, 22 ... wall portion, 23 ... movable wall, 24 ... coil spring

Claims (6)

An outer rotor having internal teeth;
It has an external tooth that engages with the internal tooth and has one fewer teeth than the internal tooth, is rotatably disposed inside the outer rotor, and repeats expansion and contraction with the outer rotor. An inner rotor forming a plurality of pump chambers;
A suction port for sucking fluid into the pump chamber and a fluid from the pump chamber formed by a case portion formed with a holding recess for rotatably holding the outer rotor and a cover portion for closing the opening of the holding recess. A pump housing provided with a discharge port for discharging
The pump housing increases in volume according to the pressure increase in the pump chamber in the process of compressing the volume of the pump chamber, and a part of the fluid flows in, and the volume in response to the pressure drop in the pump chamber in the discharge process. An internal gear pump provided with an expansion chamber for reducing the flow of fluid flowing in and flowing out the fluid into the pump chamber. The internal gear pump according to claim 1, wherein a part of the wall portion constituting the expansion chamber is a movable wall movable by an elastic body. The internal gear pump according to claim 1, wherein the expansion chamber is provided in each of the case portion and the cover portion. The internal gear pump according to any one of claims 1 to 3, wherein the opening shape of the expansion chamber is a shape in which a width in a radial direction of the outer rotor is longer than a width in a direction orthogonal to the radial direction. . The internal gear pump according to claim 4, wherein an opening shape of the expansion chamber is an elliptical shape. The internal gear pump according to any one of claims 1 to 5, wherein the suction port and the discharge port are provided in the case portion and the cover portion, respectively.

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