JP6065519B2 - Fluid pump - Google Patents

Description

  The present invention relates to a fluid pump that can suppress an increase in discharge pressure of a working fluid with respect to an increase in the rotational speed of an internal combustion engine.

  In an internal combustion engine (hereinafter also referred to as an engine) of a vehicle, a working fluid (hereinafter also referred to as hydraulic oil) is circulated for lubrication, cooling, cleaning, and the like inside the engine. The hydraulic oil is stored in an oil pan, and the hydraulic oil is sucked and discharged by a fluid pump and supplied to each part of the engine. Since the fluid pump is driven by the power of the crankshaft of the engine, the discharge pressure increases as the engine speed increases. Further, the discharge pressure of the hydraulic oil becomes high even in a low temperature state where the viscosity of the hydraulic oil becomes high.

  As the hydraulic oil discharge pressure increases, the amount of discharge increases.However, as the entire engine does not require excessive hydraulic oil, excess hydraulic oil is discharged when the discharge pressure is higher than the specified value. The shaft power is wasted. Therefore, some fluid pumps are provided with a relief valve that suppresses the discharge pressure by circulating the hydraulic oil by connecting the discharge side and the suction side of the fluid pump when the discharge pressure of the hydraulic oil becomes high. Thereby, useless consumption of the power of the crankshaft due to an increase in the discharge pressure of the hydraulic oil can be suppressed.

  In Patent Document 1, when the discharge pressure of the discharge port increases, the relief passage is opened by the opening / closing means that opens and closes by the discharge pressure, and the discharge-side pump space communicates with the suction-side pump space to circulate the working oil. A pump (fluid pump) is disclosed.

JP-A-5-248359

  In the oil pump disclosed in Patent Document 1, the pressure chamber that applies the discharge pressure to the opening / closing means and the relief passage that circulates the hydraulic oil are connected to each other. There is a risk that it flows into the relief passage, the pressure in the pressure chamber decreases, and the opening and closing means closes. When the opening / closing means closes, the pressure in the pressure chamber increases and the opening / closing means opens again. As described above, the oil pump disclosed in Patent Document 1 has a problem that the discharge pressure fluctuates because the operation of the opening / closing means is unstable and the circulation of the hydraulic oil is not stable. Further, since the drive rotor of the oil pump is attached to the end of the shaft, the shaft can be supported only on one side in the axial direction of the drive rotor, and the stable rotation of the drive rotor may be impaired. There was a problem.

  In view of the above problems, an object of the present invention is to provide a fluid pump that has a simple structure and enables stable circulation of working fluid.

In order to solve the above-described problems, the fluid pump according to the present invention is characterized in that a drive shaft, an inner rotor having an external gear with an even number of teeth arranged integrally with the drive shaft and a coaxial core, and the inner rotor Arranged eccentrically from the axis of the
An outer rotor having an internal gear that forms an operation chamber that sucks and discharges working fluid by meshing with the external gear, and a suction chamber that houses the drive shaft, the inner rotor, and the outer rotor and communicates with the operation chamber And a housing having a discharge chamber, wherein the drive shaft includes a shaft body having an internal space and a valve body disposed in the internal space, the pressure receiving chamber and the communication being independent from each other by the valve body and the internal space. Forming a chamber, the discharge chamber and the pressure receiving chamber communicate with each other, a communication passage is formed from each tooth bottom of the external gear to the internal space, and the pressure receiving chamber operates in the discharge chamber. An open state in which the communication passage and the communication chamber are communicated with each other by moving the valve body in the direction of the axial center in response to a fluid pressure; and a closed state in which the communication passage and the communication chamber are blocked. Cut into It is possible instead,
The communication chamber includes a first communication chamber and a second communication chamber that are independent of each other. When the valve body moves in the direction of the shaft core, the open state by the first communication chamber and the second communication chamber are provided. The open state is switched between the open state and the closed state .

  With such a characteristic configuration, the pressure receiving chamber that communicates with the discharge chamber and applies fluid pressure to the valve body and the communication chamber that communicates with the working chamber are formed independently. Even if the fluid pressure in the working chamber fluctuates due to the communication between the communication passage and the communication chamber when the valve is opened and closed, the valve element can perform a stable opening and closing operation while minimizing the influence thereof.

  When the fluid pump is operated, the volume of the working chamber is increased or decreased by the rotation of the inner rotor and the outer rotor, so that the pressure of the working fluid in each working chamber constantly varies. Since the discharge chamber is connected to a plurality of working chambers, and the pressure obtained by averaging them becomes the discharge pressure of the discharge chamber, the pressure fluctuation of the discharge chamber is also the average of the pressure fluctuation of the working fluid in those working chambers. Become. Therefore, the pressure fluctuation in the discharge chamber is small compared to the pressure fluctuation in the working chamber. In the fluid pump according to the present invention, since the discharge pressure of the working fluid in the discharge chamber is transmitted to the pressure receiving chamber to act on the valve body, the pressure fluctuation in the pressure receiving chamber is reduced, and the valve body is stably operated. be able to.

  In the fluid pump according to the present invention, since there are a plurality of external gears, there are a plurality of tooth bottoms and a plurality of communication passages. During rotation of the fluid pump, half of the communication passage is always on the side of the working chamber facing the suction chamber, and the other half of the communication passage is on the side of the working chamber facing the discharge chamber. In other words, the communication passage is configured so that the number of working chambers on the discharge chamber side that allows the working fluid to flow out and the number of working chambers on the suction chamber side that allow the working fluid to flow in are equal. With the same number of inflow side communication passages and outflow side communication passages, the working fluid can be completely circulated, and the fluid pump continues to rotate while maintaining a constant amount of all working fluid in the working chamber. Can be made.

In particular, since the valve body operates so that it is once closed after being opened by the first communication chamber and then opened by the second communication chamber, the rate of increase in the discharge pressure of the fluid pump with respect to the rotational speed of the internal combustion engine After changing to become smaller, it once becomes larger and then becomes smaller again. Further, the rate of increase can be changed according to the size of the passage cross-sectional area of the first communication chamber and the second communication chamber, and the period of the closed state between the open state by the first communication chamber and the open state by the second communication chamber. Can also be changed according to the length of the axial center of the valve body. Therefore, by adopting such a configuration, it is possible to freely set the change in the rate of increase in the discharge pressure of the fluid pump with respect to the rotational speed of the internal combustion engine and the rotational speed at the time of the change, so that the fluid pump can have a desired operation Can be made.

  In the fluid pump according to the present invention, the shaft body has an opening continuous with the internal space at one end, and the drive shaft is disposed between a plug for closing the opening, and between the plug and the valve body. A spring that is supported at one end by the plug and applies a biasing force to the valve body, and the plug is movable in the direction of the shaft core, thereby changing an initial load that the spring acts on the valve body. It is preferable to be able to.

  With such a configuration, since it becomes possible to adjust the rotation speed when the rate of increase in the discharge pressure with respect to the increase in the rotation speed of the internal combustion engine changes, it is possible to obtain a fluid pump having desired operating characteristics. Can do.

  In the fluid pump according to the present invention, it is preferable that the drive shaft is supported by bearing portions provided on both sides of the inner rotor in the axial direction.

  With such a configuration, even if the pressure of the working fluid acting on the inner rotor and the outer rotor varies, the drive shaft can be stably rotated, and the operation of the fluid pump can be stabilized.

It is a longitudinal section showing the schematic structure of the oil pump concerning a 1st embodiment. It is the II-II sectional view taken on the line of FIG. It is a partial expanded sectional view showing an oil pump when a valve body is in a closed state. It is a partial expanded sectional view showing an oil pump when a valve body is in the state opened a little. It is a partial expanded sectional view showing an oil pump when a valve element is in an open state. It is a graph showing the relationship between the rotation speed of an engine and the discharge pressure of an oil pump. It is a partial expanded sectional view showing the oil pump which concerns on 2nd Embodiment when a valve body exists in a closed state. It is a partial expanded sectional view showing an oil pump when a valve body is in an open state by the 1st communication room. It is a partial expanded sectional view showing an oil pump when it is in a closed state while a valve element changes from an open state by the 1st communication room to an open state by the 2nd communication room. It is a partial expanded sectional view showing an oil pump when a valve body is in an open state by the 2nd communication room. It is a graph showing the relationship between the rotation speed of an engine and the discharge pressure of an oil pump. It is a partial expanded sectional view showing the schematic structure of the oil pump which concerns on 3rd Embodiment. It is a partial expanded sectional view showing the schematic structure of an oil pump when the initial load applied to a valve body is changed. It is a graph showing the relationship between the rotation speed of an engine and the discharge pressure of an oil pump when the initial load applied to a valve body is changed.

1. First Embodiment [Structure of Oil Pump]
Hereinafter, the oil pump 1 according to the present embodiment will be described with reference to the drawings. The oil pump 1 is an example of a fluid pump. In FIG. 1, the longitudinal cross-sectional view showing the schematic structure of the oil pump 1 is shown. FIG. 2 is a sectional view taken along line II-II in FIG.

  For example, the oil pump 1 pumps up hydraulic oil as a working fluid stored in an oil pan (not shown) or an oil tank and pumps it to a lubricating portion of an engine (not shown). As shown in FIG. 1, the outer portion of the oil pump 1 is configured by assembling a first housing 2 and a second housing 3. Both the first housing 2 and the second housing 3 are examples of housings.

  The first housing 2 and the second housing 3 are made of an iron-based metal. An annular oil seal 4 is attached to the boundary between the first housing 2 and the second housing 3 to prevent leakage of hydraulic oil to the outside. A cylindrical pump chamber 7 for accommodating the pump rotor 6 is formed on the first housing 2 side of the boundary. Details of the pump rotor 6 will be described later.

  A first shaft support hole 8, which is a through-hole penetrating the first housing 2, is formed at a position eccentric from the center of the bottom surface of the pump chamber 7, and the second housing 3 is coaxial with the first shaft support hole 8. A second shaft support hole 9, which is a through-hole penetrating the second housing 3 with a smaller diameter than the first shaft support hole 8, is formed. That is, the first shaft support hole 8 and the second shaft support hole 9 are formed on both sides of the pump chamber 7 (pump rotor 6) in the axial direction. The first shaft support hole 8 and the second shaft support hole 9 are inserted with a drive shaft 10 in which shafts having two different outer diameters are connected by a coaxial core, and are rotatably supported. The inner peripheral surface of the first shaft support hole 8 and the inner peripheral surface of the second shaft support hole 9 serve as a bearing portion of the drive shaft 10. The boundary surface where the outer diameter of the drive shaft 10 changes is on the same plane as the bottom surface of the pump chamber 7. An end 10a of the drive shaft 10 on the first housing 2 side protrudes from the first housing 2 and has a small outer diameter. The end 10a is connected so that the rotational power from the crankshaft of the engine is transmitted, and the drive shaft 10 is rotated by the rotation of the crankshaft. Since the drive shaft 10 is supported by the inner peripheral surface of the first shaft support hole 8 and the inner peripheral surface of the second shaft support hole 9 formed on both sides in the axial direction, the hydraulic oil acting on the pump rotor 6 is supported. Even if the pressure fluctuates, the drive shaft 10 can be stably rotated, and the operation of the oil pump 1 can be stabilized.

  The pump rotor 6 is made of sintered metal. The pump rotor 6 includes an inner rotor 21 that is attached so that one end thereof is in contact with the boundary surface of the drive shaft 10, and an annular outer rotor 22 that is disposed so as to surround the outer periphery of the inner rotor 21. The inner rotor 21 is disposed coaxially with the drive shaft 10, is joined to the drive shaft 10 by a method such as press fitting or bonding, and rotates integrally.

  As shown in FIG. 2, an external gear 23 having six teeth is formed on the outer peripheral surface of the inner rotor 21. The number of teeth of the external gear 23 is not limited to six, but is desirably an even number. On the inner peripheral surface of the outer rotor 22, seven internal gears 24 are formed so as to mesh with the external gear 23 of the inner rotor 21. The outer rotor 22 is arranged eccentrically with respect to the drive shaft 10 of the inner rotor 21, and the outer rotor 22 rotates with the inner rotor 21 rotating. The outer peripheral surface of the outer rotor 22 is configured to be slidable in close contact with the inner peripheral surface of the pump chamber 7. The inner rotor 21 and the outer rotor 22 have the same length (thickness) in the axial direction, and two surfaces perpendicular to the axial center are also in close contact with the surface of the pump chamber 7.

  The number of teeth of the external gear 23 is one less than the number of teeth of the internal gear 24. The external gear 23 and the internal gear 24 are engaged to form a plurality of working chambers 25. The volume of each working chamber 25 changes as the inner rotor 21 and the outer rotor 22 rotate. The change in volume will be described later.

  As shown in FIG. 1, the second housing 3 includes a suction chamber 26 communicating with a suction side working chamber 25a (a working chamber 25 located in the upper half region in FIG. 2), and a discharge side working chamber 25b (FIG. 2). Discharge chambers 27 communicating with the working chambers 25) located in the lower half region of each are formed. In the first housing 2, a suction chamber 28 is formed at a position symmetrical to the suction chamber 26 across the pump rotor 6 in the axial direction, and a discharge chamber 29 is formed at a position symmetrical to the discharge chamber 27. Yes. The suction chambers 26 and 28 are connected to a suction passage (not shown) through which hydraulic oil pumped from an oil pan or the like flows, and the discharge chambers 27 and 29 have a hydraulic fluid pumped to the lubricating portion of the engine. The illustrated discharge path is connected. The suction chamber 26, the suction side working chamber 25a, and the suction chamber 28 are connected to each other, and the discharge chamber 27, the discharge side working chamber 25b, and the discharge chamber 29 are connected to each other.

  As shown in FIG. 2, the suction side working chamber 25 a is configured such that the volume increases as the pump rotor 6 rotates. As a result, a negative pressure is generated in the suction side working chamber 25a, and the working oil flowing through the suction path is pumped into the suction chamber 26, the suction side working chamber 25a, and the suction chamber 28. The volumes of the suction chambers 26 and 28 are also configured so that the volume increases as the pump rotor 6 rotates. Specifically, the depth of the suction chambers 26 and 28 along the rotation direction of the pump rotor 6 is constant, and the area of the suction chambers 26 and 28 is large when viewed along the axial direction. As a result, more hydraulic oil can be pumped up along with the rotation of the pump rotor 6, and more hydraulic oil can be fed into the suction side working chamber 25a.

  The discharge side working chamber 25b is configured such that the volume decreases with the rotation of the pump rotor 6. As a result, a positive pressure is generated in the discharge side working chamber 25b, and the hydraulic oil in the discharge chamber 29, the discharge side working chamber 25b, and the discharge chamber 27 is discharged at a predetermined discharge pressure, flows through the discharge passage, and flows through the engine. Supplied to the lubrication part. The volumes of the discharge chambers 27 and 29 are also configured so that the volume decreases as the pump rotor 6 rotates. Specifically, the depths of the discharge chambers 27 and 29 along the rotation direction of the pump rotor 6 are constant, and the areas of the discharge chambers 27 and 29 are small when viewed along the axial direction. Thereby, more hydraulic oil can be discharged with rotation of the pump rotor 6, and more hydraulic oil can be discharged from the discharge side working chamber 25b.

  Next, the structure of the drive shaft 10 will be described. The drive shaft 10 includes a shaft body 11, a valve body 15, a spring 16, and a plug 17.

  As shown in FIG. 1, the shaft body 11 has a bottomed cylindrical shape. The opening side of the shaft body 11 is closed by a plug 17 projecting outward from the second housing 3, and an internal space 12 having a constant inner diameter is formed inside the shaft body 11. A hydraulic oil introduction portion 13 is formed in the vicinity of the opening side of the shaft body 11. The hydraulic oil introduction unit 13 includes a groove 13 a formed on the outer periphery of the shaft body 11, and one or a plurality of communication holes 13 b that connect the bottom surface of the groove 13 a and the internal space 12. An introduction passage 30 is formed in the second housing 3 as a through hole that connects the discharge chamber 27 and the hydraulic oil introduction portion 13. An oil seal 18 that prevents leakage of hydraulic oil from the internal space 12 is attached to the outer peripheral surface of the plug 17.

  A back pressure release portion 14 is formed at the end of the shaft body 11 opposite to the opening. The back pressure release portion 14 includes a groove 14 a formed on the outer periphery of the shaft body 11, and one or a plurality of communication holes 14 b that connect the bottom surface of the groove 14 a and the internal space 12. An open passage 31 is formed in the first housing 2 as a through hole connecting the suction chamber 28 and the back pressure release portion 14.

  A communication passage 32 that communicates the inner space 12 with the working chamber 25 is formed radially inward from each tooth bottom of the external gear 23. The axial centers of the communication passages 32 are on the same plane, and the cross-sectional areas (passage cross-sectional areas) perpendicular to the flow direction of the hydraulic oil are the same.

  The valve body 15 is disposed so that its outer peripheral surface is in close contact with the inner peripheral surface of the internal space 12 and is movable along the axial direction of the drive shaft 10. The valve body 15 has a first recess 15 a formed along the axial direction from the end surface facing the plug 17 and over the entire circumference from the outer peripheral surface of the valve body 15 toward the radially inner side. Thereby, the convex part 15d which makes the outer periphery the bottom face of the radial direction of the 1st recessed part 15a is formed. A space formed by the first recess 15a and the internal space 12 is referred to as a pressure receiving chamber P. A second recess 15b is formed over the entire circumference from the outer peripheral surface of the valve body 15 toward the inner side in the radial direction at a predetermined interval from the first recess 15a in the axial direction. A space formed by the second recess 15b and the internal space 12 is referred to as a communication chamber C.

  A cross-sectional area (passage cross-sectional area) when the communication chamber C is cut along a plane including the axis of the drive shaft 10 is larger than half of the total cross-sectional area of the three communication passages 32. Since the communication chamber C is an annular passage, when the hydraulic oil flows into the communication chamber C from the three communication passages 32 at the same time, the hydraulic oil divides in two circumferential directions of the communication chamber C and is opposite. It flows into the three communication passages 32 on the side. Accordingly, when the cross-sectional area of the communication chamber C and the sum of the cross-sectional areas of the three communication passages 32 satisfy the above relationship, the communication chamber C can flow the hydraulic oil without resistance.

  A third recess 15c is formed along the axial direction from the end surface of the valve body 15 facing the bottom surface of the internal space 12 and outward from the center of the valve body 15 in the radial direction. A space formed by the third recess 15c and the internal space 12 is referred to as a back pressure chamber B. The pressure receiving chamber P, the communication chamber C, and the back pressure chamber B are independent from each other in the internal space 12 and do not communicate with each other. In the present embodiment, the groove depths of the first recess 15a and the second recess 15b are the same, but may be different.

  In the back pressure chamber B, a spring 16 that urges the valve body 15 in the direction of the plug 17 is disposed between the bottom surface of the internal space 12 and the bottom surface of the third recess 15c. Due to the urging force of the spring 16, the convex portion 15 d of the valve body 15 is in contact with the end face of the plug 17. This state is referred to as an initial state.

  When the valve body 15 is in the initial state, it is in a closed state. In the closed state, the communication chamber C is closer to the plug 17 in the axial direction than the communication passage 32, and the communication chamber C and the communication passage 32 are blocked. When the valve body 15 moves to the left in FIG. 1 from the initial state and the communication chamber C and the communication passage 32 are connected, the valve body 15 is opened. The communication hole 13b is always connected to the internal space 12 from the time when the valve body 15 is closed to the time when the valve body 15 is opened, and is not blocked. That is, the discharge chamber 27 and the pressure receiving chamber P are always in communication with each other via the introduction passage 30 and the hydraulic oil introduction portion 13. Also, the communication hole 14b is always connected to the internal space 12 from the time when the valve body 15 is closed to the time when the valve body 15 is opened, and is not blocked. That is, the suction chamber 28 and the back pressure chamber B are always in communication with each other via the open passage 31 and the back pressure release portion 14.

[Operation of oil pump]
Next, the operation of the oil pump 1 will be described. The end portion 10a of the drive shaft 10 of the oil pump 1 is connected so that the rotational power from the crankshaft of the engine is transmitted, and the drive shaft 10 is rotated by the rotation of the crankshaft. That is, the rotational speed of the drive shaft 10 increases or decreases in proportion to the rotational speed of the engine. Due to the rotation of the drive shaft 10, the inner rotor 21 rotates, and thereby the outer rotor 22 rotates along with the internal gear 24 that meshes with the external gear 23 of the inner rotor 21. When the inner rotor 21 and the outer rotor 22 (pump rotor 6) rotate, the hydraulic oil pumped up from an oil pan or the like and circulated through a suction path (not shown) is sucked into the suction chamber 26, the suction side working chamber 25a, and the suction chamber 28. Pumped to the discharge chambers 27 and 29 by the pump action, discharged from the discharge chambers 27 and 29, circulated through a discharge path (not shown), and pumped to the lubricating portion of the engine. The discharge pressure of the hydraulic oil discharged from the discharge chambers 27 and 29 is proportional to the engine speed. FIG. 3A shows a partially enlarged sectional view showing the oil pump 1 when the valve body 15 is in the closed state. FIG. 3B shows a partially enlarged sectional view showing the oil pump 1 when the valve body 15 is in a slightly opened state. FIG. 3C shows a partially enlarged sectional view showing the oil pump 1 when the valve body 15 is in the open state. FIG. 4 is a graph showing the relationship between the engine speed and the discharge pressure of the oil pump 1.

  FIG. 3A shows a state where the oil pump 1 is operating at a low speed. When the oil pump 1 is operating, part of the hydraulic oil in the discharge chamber 27 flows into the pressure receiving chamber P, and the pressure receiving chamber P is filled with hydraulic oil. The communication passage 32 connected to the discharge side working chamber 25b is also filled with hydraulic oil. At this time, the hydraulic oil in the pressure receiving chamber P applies the discharge pressure from the discharge chamber 27 to press the valve body 15 to the left in FIG. 3A, but the biasing force of the spring 16 is greater than the pressing force. Therefore, the valve body 15 does not move in the initial state, and the valve body 15 is in the closed state. Thereafter, when the engine speed increases, the discharge pressure of the hydraulic oil increases, and the pressure acting on the valve body 15 in the pressure receiving chamber P also increases. When this force exceeds the urging force of the spring 16, the valve body 15 begins to move to the left in FIG. 3A, but the closed state continues. The relationship between the engine speed at this time and the discharge pressure of the oil pump 1 is shown in FIG. As the valve body 15 moves, the air in the back pressure chamber B and the leaked hydraulic fluid are released from the back pressure release portion 14 to the suction chamber 28 via the open passage 31, so that the valve body 15 is smooth. To slide.

  When the engine speed further increases and the pressure in the pressure receiving chamber P increases, as shown in FIG. 3B, the valve body 15 further moves to the left and the valve body 15 begins to open, and the communication passage 32 and the communication chamber C Begins to connect. As a result, the hydraulic oil that has flowed into the communication passage 32 from the three discharge-side working chambers 25b in which positive pressure is generated flows into the communication chamber C, flows through the three communication passages 32 on the opposite side, and is on the suction side. It is returned to the working chamber 25a. As a result, as shown in FIG. 4B, the slope of the graph changes in a decreasing direction. Thereafter, when the engine speed further increases and the pressure in the pressure receiving chamber P increases, the valve body 15 further moves to the left, and is completely opened as shown in FIG. 3C. In this state, a predetermined amount of the hydraulic oil in the discharge side working chamber 25b is always circulated to the suction side working chamber 25a, and as shown in FIG. As described above, the passage cross-sectional area of the communication chamber C is larger than half of the total of the passage cross-sectional areas of the three communication passages 32. Therefore, the hydraulic oil flowing through the communication passage 32 is circulated without receiving resistance. Therefore, even if the engine speed increases thereafter and the pressure in the pressure receiving chamber P increases, the valve body 15 will not move further to the left and close again.

  During the operation of the oil pump 1, the hydraulic oil is blocked or circulated between the communication passage 32 and the communication chamber C each time the valve body 15 is switched between the closed state and the open state. The pressure of the hydraulic oil in the side working chamber 25b varies. However, in the oil pump 1 of the present embodiment, the pressure receiving chamber P for applying the pressure for operating the valve body 15 and the communication chamber C for circulating and circulating the working oil in the discharge side working chamber 25b are provided separately and independently. Therefore, even if the hydraulic oil pressure in the discharge side working chamber 25b fluctuates with the opening and closing of the valve body 15, the valve body 15 can perform the opening and closing operation stably with minimal influence.

  When the oil pump 1 is operated, the volume of the working chamber 25 is increased or decreased by the rotation of the pump rotor 6, so that the pressure of the working oil in each discharge-side working chamber 25b is constantly fluctuating. The discharge chamber 27 is connected to the three discharge side working chambers 25b, and the pressure obtained by averaging them becomes the discharge pressure of the discharge chamber 27. Therefore, the pressure fluctuations in the discharge chamber 27 are also caused by the hydraulic oil in the three discharge side working chambers 25b. The pressure fluctuation is averaged. Therefore, the pressure fluctuation in the discharge chamber 27 is smaller than the pressure fluctuation in the discharge side working chamber 25b. In the oil pump 1 of the present embodiment, the discharge pressure of the discharge chamber 27 is transmitted to the pressure receiving chamber P to act on the valve body 15. Therefore, the pressure fluctuation in the pressure receiving chamber P is also reduced, and the valve body 15 can be operated stably.

  As shown in FIG. 2, in the oil pump 1 of the present embodiment, there are six external gears 23 and six tooth bottoms, so there are also six communication passages 32. Since each communication passage 32 is formed at intervals of 60 ° in the circumferential direction, the three communication passages 32 are always on the suction side working chamber 25a side while the pump rotor 6 is rotating, and the remaining three communication passages 32 are provided. Located on the discharge side working chamber 25b side. That is, the communication passage 32 is configured such that the number of discharge side working chambers 25b for flowing out the hydraulic oil and the number of suction side working chambers 25a for flowing in are three to three. By having the same number of inflow side communication passages 32 and outflow side communication passages 32, it is possible to continue the rotation of the pump rotor 6 while keeping the amount of all the hydraulic oil in the working chamber 25 constant. If the amount of hydraulic fluid pumped from the discharge chambers 27 and 29 is drastically reduced for some reason, such as clogging of the oil filter or low hydraulic fluid viscosity, the inflow side communication passage 32 and the outflow side communication passage 32 In the oil pumps 1 that are not equal in number, there is a risk that the rotation of the pump rotor 6 may stop without the hydraulic oil being completely circulated. However, in the oil pump 1 of the present embodiment, the hydraulic oil can be completely circulated by setting the same number of communication paths 32 on the inflow side and the outflow side. Therefore, even in such a case, the rotation of the pump rotor 6 is prevented. Can continue.

2. Second Embodiment Next, an oil pump 1 according to a second embodiment will be described. In the following description of the embodiment, the same reference numerals are given to the same components as those in the first embodiment, and the description regarding the same components is omitted. The present embodiment is different from the first embodiment in that the communication chamber C of the valve body 15 is composed of a first communication chamber C1 and a second communication chamber C2, and the other structures are the same. FIG. 5A shows a partially enlarged sectional view showing the oil pump 1 when the valve body 15 is in the closed state. FIG. 5B shows a partially enlarged cross-sectional view showing the oil pump 1 when the valve body 15 is opened by the first communication chamber C1. FIG. 5C shows a partially enlarged cross-sectional view showing the oil pump 1 when the valve body 15 is in the closed state while the valve body 15 is switched from the open state by the first communication chamber C1 to the open state by the second communication chamber C2. FIG. 5D is a partially enlarged cross-sectional view showing the oil pump 1 when the valve body 15 is opened by the second communication chamber C2. FIG. 6 is a graph showing the relationship between the engine speed and the discharge pressure of the oil pump 1.

  As shown in FIG. 5A, in the oil pump 1 of the present embodiment, a first communication chamber C1 and a second communication chamber C2 are formed from the left side of the valve body 15. The first communication chamber C1 and the second communication chamber C2 are separated and independent, and the opened state of the valve body 15 by the first communication chamber C1 and the opened state by the second communication chamber C2 once sandwich the closed state. It is designed to switch. The cross-sectional area of the first communication chamber C1 is smaller than half of the total cross-sectional area of the three communication passages 32, and the cross-sectional area of the second communication chamber C2 is equal to the cross-sectional area of the three communication passages 32. It is larger than half of the total.

  FIG. 5A shows a state where the oil pump 1 is operating at a low speed. The relationship between the engine speed and the discharge pressure of the oil pump 1 at this time is shown in FIG. When the engine speed increases from this state and the pressure in the pressure receiving chamber P increases, as shown in FIG. 5B, the communication passage 32 and the first communication chamber C1 are connected, and the valve body 15 is open (hereinafter referred to as this state). The state is referred to as a first open state). As a result, as shown in FIG. 6B, the slope of the graph representing the relationship between the engine speed and the discharge pressure of the oil pump 1 is reduced. At this time, the passage cross-sectional area of the first communication chamber C1 is smaller than half of the total passage cross-sectional area of the three communication passages 32, so that the hydraulic oil flowing through the communication passage 32 flows into the first communication chamber C1. It is difficult to circulate hydraulic oil according to the discharge pressure due to resistance. As a result, when the engine speed further increases and the pressure in the pressure receiving chamber P increases, the valve body 15 further moves to the left, and the valve body 15 is closed again as shown in FIG. 5C. As a result, the flow of hydraulic oil between the communication passage 32 and the first communication chamber C1 is interrupted and is not circulated, so that the relationship between the engine speed and the discharge pressure of the oil pump 1 is obtained as shown in FIG. The slope of the representing graph increases again.

  When the engine speed further increases, the valve body 15 further moves to the left, the communication passage 32 and the second communication chamber C2 are connected, as shown in FIG. This state is referred to as a second open state). As a result, as shown in FIG. 6D, the slope of the graph representing the relationship between the engine speed and the discharge pressure of the oil pump 1 is reduced again. The slope of the graph in the second open state is smaller than the slope of the first open state shown in B of FIG. This is because the passage cross-sectional area of the second communication chamber C2 is larger than half of the total cross-sectional area of the three communication passages 32, so that the hydraulic oil flowing through the communication passage 32 is circulated without receiving resistance, This is because the amount of hydraulic fluid to be circulated increases. As a result, a predetermined amount of the hydraulic oil in the discharge side working chamber 25b is always circulated to the suction side working chamber 25a, and even if the engine speed further increases to increase the pressure in the pressure receiving chamber P, the valve The body 15 does not move to the left and close again.

  In this way, by forming a plurality of communication chambers by changing the passage cross-sectional area, the change in the rate of increase in the discharge pressure of the oil pump 1 relative to the engine speed and the speed at the time of the change can be freely set. The oil pump 1 can be made to perform a desired operation.

  In the present embodiment, the valve body 15 has two types of communication chambers, but is not limited thereto. Depending on the operation required for the oil pump 1, a structure having three or more types of communication chambers may be used.

3. Third Embodiment Next, an oil pump 1 according to a third embodiment will be described. FIG. 7 is a partial enlarged cross-sectional view showing a schematic structure of the oil pump 1 according to the present embodiment. In the present embodiment, in the oil pump 1 of the first embodiment, the arrangement of the valve body 15 and the spring 16 in the internal space 12 is reversed. That is, in the initial state, the convex portion 15 d of the valve body 15 is in contact with the bottom surface of the internal space 12, and one end of the spring 16 is in contact with the plug 17. Further, along with this, the formation positions of the hydraulic oil introduction part 13 and the back pressure release part 14 are reversed. The introduction passage 30 is connected to the discharge chamber 29, and the open passage 31 is connected to the suction chamber 26. Other structures are the same.

  FIG. 8 is a partial enlarged cross-sectional view showing a schematic structure of the oil pump 1 when the initial load acting on the valve body 15 (the urging force by the spring 16 in the initial state) is changed. In this case, the plug 17 is loosened, the spacer 19 is sandwiched between the plug 17 and the shaft body 11, the attachment length of the spring 16 in the initial state is lengthened, and the initial load acting on the valve body 15 is reduced. Thus, if the initial load acting on the valve body 15 is reduced, the urging force by the spring 16 when the valve body 15 is in the open state is also reduced, so that the valve body 15 is opened at a lower discharge pressure. be able to. FIG. 9 is a graph showing the relationship between the engine speed and the discharge pressure of the oil pump 1 when the initial load applied to the valve body 15 is changed.

  In FIG. 9, the change in the rate of increase in the discharge pressure with respect to the increase in the engine speed when the spacer 19 shown in FIG. 7 is not included is shown by a solid line, and the change when the spacer 19 shown in FIG. Indicated by a two-dot chain line. From this, it can be seen that the engine speed is lower when the spacer 19 is inserted when the slope of the graph of the increase in the discharge pressure with respect to the increase in the engine speed becomes smaller. Thus, by adjusting the discharge pressure when the valve body 15 is in the open state with the spacer 19, desired characteristics can be obtained in the oil pump 1.

  Although the oil pump 1 of this embodiment was applied to the valve body 15 of 1st Embodiment, it is not restricted only to this, Of course, it can apply also to the valve body 15 of 2nd Embodiment.

  In the oil pump 1 of each of the embodiments described above, the oil pump 1 is driven by the power of the crankshaft of the engine, but is not limited thereto. An oil pump driven by an electric motor or other driving method is also included.

  The structures of the above embodiments can be combined as much as possible.

  The present invention can be used for a fluid pump that can suppress an increase in discharge pressure of a working fluid with respect to an increase in the rotational speed of an internal combustion engine.

1 Oil pump (fluid pump)
2 First housing (housing)
3 Second housing (housing)
8 1st shaft support hole (bearing part)
9 Second shaft support hole (bearing part)
DESCRIPTION OF SYMBOLS 10 Drive shaft 11 Shaft body 12 Internal space 15 Valve body 16 Spring 17 Plug 21 Inner rotor 22 Outer rotor 23 External gear 24 Internal gear 25 Actuation chamber 26, 28 Suction chamber 27, 29 Discharge chamber 32 Communication channel C Communication chamber C1 1st Communication chamber C2 Second communication chamber P Pressure receiving chamber

Claims (3)

A drive shaft;
An inner rotor having an external gear with an even number of teeth arranged integrally with the drive shaft and coaxial core;
An outer rotor provided with an internal gear that is arranged eccentrically from the axis of the inner rotor, is rotated by the rotation of the inner rotor, and is engaged with the external gear to form a working chamber that sucks and discharges working fluid; ,
A housing that houses the drive shaft, the inner rotor, and the outer rotor, and has a suction chamber and a discharge chamber that communicate with the working chamber;
The drive shaft includes a shaft body having an internal space and a valve body disposed in the internal space,
The valve body and the internal space form a pressure receiving chamber and a communication chamber independent of each other,
The discharge chamber and the pressure receiving chamber communicate with each other,
A communication path is formed from each tooth bottom of the external gear to the internal space,
The pressure receiving chamber receives the pressure of the working fluid in the discharge chamber and moves the valve body in the direction of the axial core, thereby opening the communication passage and the communication chamber, the communication passage, It can be switched to a closed state that shuts off the communication room ,
The communication chamber includes a first communication chamber and a second communication chamber independent of each other,
A fluid pump that switches between the open state by the first communication chamber and the open state by the second communication chamber across the closed state by the valve body moving in the direction of the shaft core . The shaft body has an opening continuous with the internal space at one end,
The drive shaft further includes a plug that closes the opening, and a spring that is disposed between the plug and the valve body and is supported at one end by the plug and applies a biasing force to the valve body,
2. The fluid pump according to claim 1, wherein the plug is movable in a direction of the shaft core, whereby an initial load applied to the valve body by the spring can be changed. The fluid pump according to claim 1 or 2, wherein the drive shaft is supported by bearing portions provided on both sides of the inner rotor in the direction of the axis.

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