JP2016084772A - Fluid pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluid pump suppressing leakage of fluid in temperature rise.SOLUTION: A fluid pump includes in a storage space S of a pump housing H: an inner rotor 11 having a plurality of external teeth 11A; an outer rotor 12 having a plurality of internal teeth 12A engaged to the outer teeth; and a cylindrical body 13 externally fitted to the outer rotor 12 in a relatively rotatable manner. The heat expansion coefficient of a member constituting the cylindrical body 13 is set to be equal to or less than the heat expansion coefficient of the outer rotor 12.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for suppressing performance degradation due to thermal expansion in a fluid pump in which an inner rotor having a plurality of external teeth and an outer rotor having a plurality of internal teeth are meshed with each other.

  As a fluid pump configured as described above, Patent Document 1 discloses a member having an inner rotor (external gear in the literature) and an outer rotor (internal gear in the literature) having the same thermal expansion coefficient (linear expansion coefficient in the literature). The technology constituted by is described. Thereby, in the fluid pump of patent document 1, the reduction | decrease of the leakage flow volume between an inner rotor and an outer rotor is implement | achieved.

  Further, in Patent Document 2, a cylindrical collar is provided between the inner peripheral surface of the pump casing and the outer peripheral surface of the outer rotor, and this collar is smaller than the thermal expansion coefficient of the pump casing and more than the thermal expansion coefficient of the outer rotor. Largely set technologies are described. As a result, the fluid pump of Patent Document 2 suppresses an increase in clearance between the outer rotor outer periphery and the collar when the temperature rises, and suppresses oil leakage from the high-pressure side discharge port to the low-pressure side suction port. Realized.

Japanese Utility Model Publication No. 63-162983 JP 2005-201103 A

  Taking a trochoidal fluid pump as an example of a fluid pump in which an inner rotor having a plurality of external teeth and an outer rotor having a plurality of internal teeth are engaged with each other, an iron-based sintered metal is used for the inner rotor and the outer rotor. Thus, the wear resistance can be improved and the thermal expansion coefficient can be made equal.

  As the material of the pump housing that accommodates these, aluminum is often used in order to obtain light weight and good workability. However, the thermal expansion coefficient of aluminum is larger than that of iron. Therefore, for example, when the temperature of the fluid rises, the gap between the outer rotor and the pump housing is enlarged, which may lead to fluid leakage.

  Further, in the configuration that causes fluid leakage as the temperature rises, the pressurized fluid leaks from the outer periphery of the outer rotor to the housing space of the pump housing, and this fluid further flows into the suction port, leading to a decrease in pump performance. Met.

  In order to suppress the leakage of the fluid, it is considered to reduce the gap between the inner peripheral surface of the accommodation space formed in the pump housing and the outer peripheral surface of the outer rotor. However, such a configuration in which the gap is reduced not only requires high machining accuracy, but also causes an inconvenience that the outer periphery of the outer rotor is in close contact with the inner surface of the housing space of the pump housing at low temperatures, thereby increasing rotational resistance. there were.

  On the other hand, the configuration shown in Patent Document 2 does not require as high processing accuracy as the configuration in which the outer rotor is directly fitted into the housing space of the pump housing, and the inner peripheral surface of the pump housing and the outer rotor are not affected when the temperature rises. The expansion of the clearance (clearance) with the outer periphery is suppressed. However, with this configuration, it was imagined that fluid leaks from this gap because the gap between the outer rotor and the collar expands when the temperature rises.

  The objective of this invention exists in the point which comprises the fluid pump by which the leak of a fluid is suppressed also at the time of a temperature rise.

The feature of the present invention is that the inner rotor has a plurality of external teeth and is rotatable about the first axis.
A plurality of inner teeth meshing with the outer teeth of the inner rotor are formed on the inner periphery, and the outer rotor is rotatable about a second axis that is eccentric with respect to the first axis in a posture parallel to the first axis. When,
A cylindrical body externally fitted so as to be rotatable relative to the outer periphery of the outer rotor;
A cylinder having a suction port for sucking fluid and a discharge port for discharging fluid, and having a cylindrical inner surface centered on the second axis for accommodating the outer rotor and the inner rotor in a state in which the cylindrical body is fitted. A pump housing having a peripheral wall,
The member constituting the cylindrical body has a thermal expansion coefficient equal to or lower than the thermal expansion coefficient of the outer rotor.

As an example of this configuration, in a configuration in which a cylindrical body having the same thermal expansion coefficient as that of the outer rotor is fitted to the outer periphery of the outer rotor, the value of the gap between the outer periphery of the outer rotor and the inner periphery of the cylindrical body is changed when the temperature rises. There is no. In addition, in a configuration in which a cylindrical body having a thermal expansion coefficient smaller than that of the outer rotor is fitted, the gap between the outer circumference of the outer rotor and the inner circumference of the cylindrical body is reduced when the temperature rises, and fluid from the outer circumference of the outer rotor is reduced. Control leakage.
Since the cylindrical body is used, even if a gap is formed between the outer periphery of the outer rotor and the inner periphery of the cylindrical body at low temperatures, fluid leakage can be suppressed due to the high viscosity of the fluid at low temperatures. In addition, since the cylindrical body is used, the configuration in which the gap between the outer periphery of the outer rotor and the inner circumference of the cylindrical body is reduced when the temperature rises can suppress fluid leakage by reducing the gap although the viscosity of the fluid is reduced. Further, a cylindrical body is fitted on the outer periphery of the outer rotor so as to be relatively rotatable.
Therefore, a fluid pump is configured in which fluid leakage is suppressed even when the temperature rises, and the outer rotor rotates easily.

  In the present invention, the thermal expansion coefficient of the member constituting the cylindrical body may be equal to or lower than the thermal expansion coefficient of the pump housing.

  According to this, when the temperature rises, the gap between the outer periphery of the cylinder and the inner periphery of the pump housing is enlarged, and even when the cylinder contacts the outer rotor, it acts on the outer rotor from the housing via the cylinder during rotation. Resistance can be reduced.

  In the present invention, a protrusion protruding in a direction perpendicular to the second axis may be formed on at least one of the outer peripheral wall of the cylindrical body and the inner peripheral wall of the pump housing.

  For example, a structure in which a protrusion is formed on the outer periphery of a cylindrical body and the protrusion is in contact with the inner periphery of the pump housing, and a structure in which a protrusion is formed on the inner periphery of the pump housing and the protrusion is in contact with the outer periphery of the cylindrical body. In any configuration, the friction received from the pump housing when the cylindrical body rotates is reduced. As a result, even when the outer rotor and the cylindrical body rotate integrally, the resistance acting on the cylindrical body can be reduced.

  In the present invention, the thickness of the cylindrical body in the direction along the second axis may be set larger than the thickness of the outer rotor in the direction along the second axis.

  For example, in a configuration in which the outer rotor and the cylindrical body are accommodated in the pump housing with the flat wall surface of the pump housing sandwiched from the thickness direction, the gap between the both end portions and the wall surface in the thickness direction of the cylindrical body is the thickness of the outer rotor. It can be narrower than the gap between both ends in the direction and the wall surface. Thereby, even if the fluid leaks outward from the outer rotor, the cylindrical body can suppress the fluid leaking outward from the outer rotor.

  The present invention may include an electric motor that drives and rotates the inner rotor or the outer rotor.

  Since the fluid pump of the present invention can reduce the resistance acting on the outer rotor by providing a cylindrical body that rotates relative to the outer rotor, it is possible to use a low-torque electric motor, and to reduce the size and weight of the fluid pump. Is possible.

It is sectional drawing of an oil pump. It is the II-II sectional view taken on the line of FIG. It is a disassembled perspective view of an oil pump. It is sectional drawing of the oil pump of another embodiment (a). It is a disassembled perspective view of the oil pump of another embodiment (a).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Basic configuration]
As shown in FIGS. 1 to 3, an oil pump as a fluid pump is configured by accommodating an inner rotor 11, an outer rotor 12, and a cylindrical body 13 in a housing space S of a pump housing H.

  This oil pump includes an electric motor M that drives and rotates the drive shaft 10 outside the pump housing H. By this driving, the inner rotor 11 and the outer rotor 12 are rotated in conjunction with each other, and oil as a fluid is sucked from the suction port 4 and sent out from the discharge port 5. In this configuration, the output shaft of the electric motor M also serves as the drive shaft 10. However, the drive shaft 10 is provided and the output shaft of the electric motor M is connected to the drive shaft 10 by a joint or the like. It may be adopted.

  The oil pump shown in the figure is an inscribed trochoid pump, and is used to supply engine lubricating oil as hydraulic oil (oil) to actuators in various parts in a vehicle such as a passenger car. In addition, the pump of this structure can also be used for supply of fluids other than oil.

[Details of the pump]
The pump housing H has a configuration in which an aluminum base plate 2 is superposed on an aluminum housing body 1 and connected by connecting bolts 3. The housing body 1 is formed with a housing space S having a cylindrical inner peripheral wall Sc centered on the second axis X2. The housing space S includes an inner peripheral wall Sc, a main body inner wall Sa formed in the housing body 1 in a posture orthogonal to the second axis X2, and a plate formed in the base plate 2 in a posture orthogonal to the second axis X2. It is comprised with the form enclosed by inner wall Sb.

  In particular, the inner peripheral wall Sc of the accommodation space S is formed with a plurality of protrusions Sd at predetermined intervals along the circumferential direction. The housing body 1 is manufactured by die casting in which molten aluminum is pressed into a mold, and the protruding portion Sd of the inner peripheral wall Sc is cut around the second axis X2 in the cutting process after manufacturing. Therefore, the cast surface is left outside the cut area, and the cutting amount is reduced.

  The base plate 2 is formed with a suction port 4 communicating with the accommodation space S and a discharge port 5 in a hole shape. A through-hole 6 through which the drive shaft 10 is inserted is formed in the housing body 1 on the same axis as the first axis X1 that is parallel to the second axis X2.

  The drive shaft 10 is fitted to the inner rotor 11 so as not to be relatively rotatable, and a plurality of external teeth 11A are formed on the outer periphery. The outer rotor 12 has a number of internal teeth 12 </ b> A that is one more than the external teeth 11 </ b> A of the inner rotor 11. A common iron-based sintered metal is used as a material for the inner rotor 11 and the outer rotor 12. Thereby, the thermal expansion coefficients of the inner rotor 11 and the outer rotor 12 are equal.

  The cylindrical body 13 is formed with a cylindrical outer peripheral wall 13A having an outer diameter that fits into the plurality of protrusions Sd of the inner peripheral wall Sc of the housing space S, and an inner peripheral cylindrical wall 13B having an inner diameter that fits the outer peripheral surface 12B of the outer rotor 12. Is formed. The cylindrical body 13 is made of a material (for example, iron-based sintered metal) equal to the thermal expansion coefficient of the material of the outer rotor 12 or a material (for example, ceramics or cemented carbide) having a smaller thermal expansion coefficient of the outer rotor 12. It is used.

  Further, the thermal expansion coefficient of the cylindrical body 13 is set to be equal to or lower than the thermal expansion coefficient of the pump housing H (housing main body 1 and base plate 2). In the embodiment, the thermal expansion coefficient of the cylindrical body 13 is less than the thermal expansion coefficient of the pump housing H, but the respective thermal expansion coefficients may be set equal.

  In particular, the radius of the cylindrical inner peripheral wall 13B of the cylindrical body 13 is set to a slightly larger value than the radius of the outer peripheral surface 12B of the outer rotor 12, and the radius of the cylindrical outer peripheral wall 13A of the cylindrical body 13 is set within the accommodating space S. It is set to a value slightly smaller than the radius of the imaginary circle connecting the protruding ends of the plurality of projecting portions Sd formed on the peripheral wall Sc.

  For these reasons, the inner rotor 11 is disposed so as to be accommodated in the accommodating space S in a state in which the drive shaft 10 is inserted into the through hole 6, the outer rotor 12 is disposed at the outer peripheral position, and the cylindrical body 13 is disposed on the outer periphery. By arranging, as shown in FIG. 1, a part of the outer teeth 11 </ b> A of the inner rotor 11 meshes with a part of the inner teeth 12 </ b> A of the outer rotor 12.

  In this positional relationship, the inner rotor 11 is rotatably disposed on the first axial core X1 and the coaxial core, and the outer rotor 12 and the cylindrical body 13 are rotatably disposed on the second axial core X2 and the coaxial core. Further, the cylindrical body 13 is rotatable relative to the outer rotor 12 and the pump housing H.

  In this oil pump, the inner rotor 11 and the outer rotor 12 are set to have the same thickness (rotor thickness Ta described later) in the direction along the first axis X1, and this value is the inner peripheral wall of the inner peripheral wall Sc of the pump housing H. The depth is set to be slightly smaller than the depth Tc (distance between the main body inner wall Sa and the plate inner wall Sb). Further, the ring thickness Tb as the thickness in the direction along the first axis X1 of the cylindrical body 13 is set to a value slightly larger than the rotor thickness Ta as the thickness in the direction along the second axis X2 of the outer rotor 12. Has been.

  Thereby, the end in the thickness direction of the cylindrical body 13 and the pump from the gap formed between the end in the thickness direction of the outer rotor 12 and the main body inner wall Sa or the plate inner wall Sb of the pump housing H, and the pump A gap formed between the main body inner wall Sa of the housing H or the plate inner wall Sb is reduced.

[Operating form]
In this oil pump, the inner rotor 11 rotates around the first axis X1 in the direction indicated by the arrow in FIG. 1 due to the rotation of the drive shaft 10 by the driving force of the electric motor M, and the outer teeth of the inner rotor 11 accompany this rotation. The inner teeth 12A meshing with 11A move, and accordingly, the outer rotor 12 rotates around the second axis X2. By this rotation, oil is sucked from the suction port 4 between the outer teeth 11A of the inner rotor 11 and the inner teeth 12A of the outer rotor 12, and the oil pressurized between the outer teeth 11A and the inner teeth 12A is discharged to the discharge port 5. The operation to send out is performed.

  In this oil pump, the relatively rotatable cylindrical body 13 is interposed between the housing space S, so that the outer peripheral surface 12B of the outer rotor 12 can be rotated together with the cylindrical body 13 during this operation. . Thereby, for example, when compared with a configuration in which the outer peripheral surface 12B of the outer rotor 12 is in contact with the inner peripheral surface of the accommodation space S of the pump housing H, the sliding resistance acting on the outer rotor 12 is reduced, and light rotation is realized. To do. The rotation of the outer rotor 12 and the cylindrical body 13 is performed when the oil is low temperature and high in viscosity. During this rotation, the cylindrical outer peripheral wall 13A of the cylindrical body 13 comes into contact with the protruding ends of the plurality of protrusions Sd, so that the sliding resistance of the cylindrical body 13 is reduced and rotation is performed with a light load.

  Further, when the oil temperature rises with the engine temperature rise, the temperature of the entire oil pump rises. Due to this temperature rise, the pump housing H is thermally expanded, the radius of the inner peripheral wall Sc of the accommodation space is expanded, and the radius of the virtual circle connecting the protruding ends of the plurality of projecting portions Sd is expanded.

  In the oil pump of the present invention, since the cylindrical body 13 having a thermal expansion coefficient smaller than or equal to the thermal expansion coefficient of the outer rotor 12 is used, the outer peripheral surface of the outer rotor 12 and the cylindrical inner peripheral wall of the cylindrical body 13 when the temperature rises. The gap with 13B (inner circumference) does not expand. Moreover, since the thermal expansion coefficient of the cylindrical body 13 is smaller than the thermal expansion coefficient of the pump housing H (the housing body 1 and the base plate 2), the outer periphery of the cylindrical body 13 and the inner periphery of the housing body 1 of the pump housing H when the temperature rises. Increase the gap. Thereby, when the cylindrical body 13 rotates, resistance from the pump housing H does not act on the cylindrical body 13, and therefore the smoothness of the outer rotor 12 can be achieved even when the inner periphery of the cylindrical body 13 is in contact with the outer periphery of the outer rotor 12. To enable easy rotation.

  When the oil is low temperature and high in viscosity, even if a gap is formed between the outer periphery of the outer rotor 12 and the cylindrical inner peripheral wall 13B of the cylindrical body 13, leakage of oil from the cylindrical body 13 to the outside is prevented. . Further, in a configuration in which the gap between the outer periphery of the outer rotor 12 and the cylindrical inner peripheral wall 13B of the cylindrical body 13 is reduced when the oil temperature rises, the oil leaks outward from the cylindrical body 13 even if the oil viscosity decreases. Can be suppressed.

  Further, since the ring thickness Tb of the cylindrical body 13 is set to a value slightly larger than the rotor thickness Ta of the outer rotor 12, the oil flow can be reduced even in a situation where oil can leak out from the outer periphery of the outer rotor 12. It suppresses with the clearance gap between the edge part of the thickness direction of the cylindrical body 13, and the pump housing H. FIG. As a result, the viscosity of the oil decreases due to the temperature rise, and the leakage of the oil is satisfactorily suppressed even when each part is thermally expanded, and the oil leaked outward from the outer periphery of the outer rotor 12 flows into the suction port 4. Eliminate and increase pump efficiency.

  In particular, in this oil pump, by forming a plurality of protrusions Sd on the inner peripheral wall Sc of the housing space S of the pump housing H, the sliding resistance during rotation of the outer rotor 12 is reduced, and the low-torque electric motor M is used. Making it possible.

[Another embodiment]
The present invention may be configured as follows in addition to the embodiment described above.

(A) As shown in FIGS. 4 and 5, the cylindrical body 13 is formed into a cup shape by integrally forming a wall portion 13 </ b> W orthogonal to the first axis X <b> 1 in the cylindrical body 13. In this configuration, the cylindrical body 13 and the wall portion 13W can be integrally rotated with respect to the pump housing H. Further, in this configuration, a hole 13C through which the drive shaft 10 is inserted is formed in the wall portion 13W, and the end portions of the inner rotor 11 and the outer rotor 12 are in close contact with the inner surface of the wall portion 13W.

  In this other embodiment (a), since the inner rotor 11 and the outer rotor 12 are accommodated in the internal space of the cylindrical body 13 and the wall portion 13W, leakage of oil (fluid) to the outside can be suppressed. In particular, in this configuration, although it is necessary to finish the inner surface of the wall portion 13W smoothly, it is not necessary to finish the inner wall Sa of the pump housing H smoothly, and the first axis X1 is formed on the outer peripheral portion of the inner wall Sa of the housing body 1. By forming the annular support portion Se centered on the sliding body, the sliding resistance of the cylindrical body 13 is reduced.

  By forming the annular support portion Se, the main body inner wall Sa of the accommodation space S is not required to be processed, and a plurality of protrusions Sd are formed on the inner peripheral wall Sc of the accommodation space S. In this way, the machining process can be reduced.

  In this alternative embodiment (a), when the cylindrical body 13 can be accurately rotated at an appropriate position around the first axis X1, the annular support portion Se and the projection portion Sd are not necessarily provided. It is not necessary to form in the inner surface of the accommodation space S, and it may be a cast surface.

(B) A plurality of protrusions protruding outward with respect to the cylindrical outer peripheral wall 13A of the cylindrical body 13 are formed. In this configuration, it is desirable to finish the inner peripheral wall Sc of the accommodation space S to a peripheral surface centered on the second axis X2, but it is not necessary to finish, and the sliding resistance during rotation of the cylindrical body 13 can be reduced. It can also be reduced.

(C) The drive shaft 10 may be driven by the driving force of the engine E. Moreover, as a structure driven by the electric motor M, a rotor having a permanent magnet may be fixed to the drive shaft 10, and a stator constituted by a field coil may be provided around the rotor.

  The present invention can be used for a fluid pump in which an inner rotor and an outer rotor are housed in a pump housing.

4 Suction port 5 Discharge port 11 Inner rotor 11A Outer teeth 12 Outer rotor 12A Inner teeth 13 Cylindrical body 13B Cylindrical outer peripheral wall (outer peripheral wall)
M Electric motor Sc Inner peripheral wall Sd Protrusion H Pump housing X1 First axis X2 Second axis

Claims (5)

An inner rotor having a plurality of external teeth and rotatable about a first axis;
A plurality of inner teeth meshing with the outer teeth of the inner rotor are formed on the inner periphery, and the outer rotor is rotatable about a second axis that is eccentric with respect to the first axis in a posture parallel to the first axis. When,
A cylindrical body externally fitted so as to be rotatable relative to the outer periphery of the outer rotor;
A cylinder having a suction port for sucking fluid and a discharge port for discharging fluid, and having a cylindrical inner surface centered on the second axis for accommodating the outer rotor and the inner rotor in a state in which the cylindrical body is fitted. A pump housing having a peripheral wall,
The fluid pump in which the thermal expansion coefficient of the member which comprises the said cylindrical body is below the thermal expansion coefficient of the said outer rotor.   The fluid pump according to claim 1, wherein a member constituting the cylindrical body has a thermal expansion coefficient equal to or less than a thermal expansion coefficient of the pump housing.   3. The fluid pump according to claim 1, wherein a protrusion projecting in a direction perpendicular to the second axis is formed on at least one of the outer peripheral wall of the cylindrical body and the inner peripheral wall of the pump housing. .   The thickness in the direction along the said 2nd axial center of the said cylindrical body is set larger than the thickness in the direction along the said 2nd axial center of the said outer rotor. Fluid pump.   The fluid pump as described in any one of Claims 1-4 provided with the electric motor which drives and rotates the said inner rotor or the said outer rotor.

Images