Patent Application
20180156214
The present invention relates to a pump unit and an actuator.
As a pump unit, for example, as disclosed in JP 2013-227943 A, there is a pump unit that includes a hydraulic pump, a motor, a coupling that couples a drive shaft of the hydraulic pump and the shaft of the motor, and an attachment portion that couples the hydraulic pump and the motor and houses the coupling.
In many cases, grease is filled between a coupling and a shaft and between the coupling and a drive shaft in order to prevent the wear of the coupling, the shaft and the drive shaft and to smoothly drive a hydraulic pump by a motor.
Additionally, in a pump unit, the coupling is cylindrical and the shaft of the motor is fitted to the inner periphery of the coupling together with a key to prevent rotation, and as for the prevention of rotation between the drive shaft of the hydraulic pump and the coupling, a spline and the like are used.
In the pump unit as described above, since a seal member that seals around the drive shaft is provided in an attachment portion so that hydraulic oil does not enter from a hydraulic pump side, the overall length of the pump unit becomes long.
Additionally, if the pump is used continuously for a long period of time, the grease may escape from the seal member that seals around the drive shaft and enter the hydraulic oil in the hydraulic pump. Usually, a filter for removing contaminants is installed in a hydraulic circuit. There is a case that grease adheres to this filter and hinders the passage of the hydraulic oil through the filter. In such a situation, the mechanical efficiency of the pump unit deteriorates, causing a decrease in discharge pressure and an increase in power consumption.
Accordingly, the present invention has been invented to improve the above-described problems. It is an object of the present invention to provide a pump unit capable of shortening the overall length thereof and maintaining mechanical efficiency even after long-term use and also to provide an actuator including such a pump unit.
A pump unit in a means for solving the problems according to the present invention includes a hydraulic pump, a motor, a coupling that couples a drive shaft of the hydraulic pump and a shaft of the motor, a holder having a housing portion that is hollow and houses the coupling, and an introduction passage that guides the hydraulic oil to the housing portion.
Hereinafter, the present invention will be described on the basis of an embodiment illustrated in the drawings. As illustrated in
Hereinafter, each part of the pump unit U will be described in detail. As illustrated in
As illustrated in
One end of the drive shaft 2 is inserted into the case 1 through the hole 1d provided in the case 1, and the other end thereof protrudes to the outside of the case 1. The drive shaft 2 has a tip on one end side rotatably held by the lid portion 1c and an intermediate part rotatably held by the bottom portion 1a and is rotatable around an axis with respect to the case 1. Additionally, the drive shaft 2 has a plurality of spline teeth 2a provided on the outer periphery of a tip on the other end side along an axial direction in a circumferential direction.
On the outer periphery of the drive shaft 2, the drive gear 4 housed in the case 1 is mounted. The drive gear 4 rotates in the case 1 together with the drive shaft 2 when the drive shaft 2 is rotationally driven by sliding contact with the bottom portion 1a and the lid portion 1c.
The driven shaft 3 has a tip on one end side rotatably held by the lid portion 1c and the other end rotatably held by the bottom portion 1a and is rotatable around the axis in the case 1. On the outer periphery of the drive shaft 2, the driven gear 5 housed in the case 1 and meshing with the drive gear 4 is mounted. The driven gear 5 is in sliding contact with the bottom portion 1a and the lid portion 1c, and rotates in the case 1 together with the drive gear 4 when the drive gear 4 is rotationally driven. Therefore, when the drive shaft 2 is rotationally driven, the drive gear 4 and the driven gear 5 rotate together in the case 1.
Then, when the drive gear 4 in
The motor M includes a motor main body 6 that encloses a stator (not illustrated), and the shaft 7 that is rotatably mounted on the motor main body 6 and is rotationally driven by energization of the motor main body 6. It suffices for the motor M to be able to rotationally drive the shaft 7 by energization, and various motors such as AC motor, DC motor, and induction motor can be adopted for the motor M. Additionally, the shaft 7 is provided with a plurality of spline teeth 7a provided on the outer periphery of a tip along the axial direction in a circumferential direction. A seal is provided between the motor main body 6 and the shaft 7, and the interior of the motor main body 6 is densely sealed.
The coupling 8 is cylindrical and has a plurality of spline grooves 8a provided on the inner periphery thereof in a circumferential direction along the axial direction from one end to the other end in a seamless manner. The number of the spline grooves 8a set is equal to the number of the spline teeth 2a of the drive shaft 2 and the number of the spline teeth 7a of the shaft 7. Then, when the tip of the drive shaft 2 is inserted into the coupling 8, the spline teeth 2a mesh with the spline grooves 8a, and the drive shaft 2 is fitted to the coupling 8. Additionally, when a tip of the shaft 7 is inserted into the coupling 8, the spline teeth 7a mesh with the spline grooves 8a, and the shaft 7 is fitted to the coupling 8. When the drive shaft 2 and the shaft 7 are fitted to the coupling 8 in this mariner, the drive shaft 2 and the shaft 7 are prevented from rotating by the coupling 8, and the power of the shaft 7 of the motor M is transmitted to the drive shaft 2, and the drive shaft 2 can be rotationally driven.
Additionally, a groove 8b provided along a circumferential direction is provided in the intermediate inner periphery of the coupling 8, and a snap ring 9 is mounted in the groove 8b. When the snap ring 9 is mounted in the groove 8b, the snap ring 9 functions as a protruding member protruding toward the inside of the inner periphery of the coupling 8. The protruding member may be formed by a member other than the snap ring 9. If the protruding member is provided on the coupling 8, even if the coupling 8 moves in the axial direction, the tip surface of the drive shaft 2 or the shaft 7 comes into contact with the protrusion member and further movement of the coupling 8 in the same direction is restricted, and the coupling 8 is prevented from falling off from the drive shaft 2 and the shaft 7.
As illustrated in
Then, the motor M is mounted on the left end of the holder H in
Note that a snap ring 16 is mounted on the inner periphery of the housing portion L of the holder H in the vicinity of the right end in
Subsequently, the hydraulic pump P is mounted on the right end of the holder H in
Then, when the hydraulic pump P is mounted on the holder H, the suction port 1e provided in the bottom portion 1a of the case 1 of the hydraulic pump P is opposed to the lateral hole 12 provided in the holder H and the suction port 1e and the lateral hole 12 communicate with each other, and similarly, the discharge port 1f is opposed to the lateral hole 13 and the discharge port 1f and the lateral hole 13 communicate with each other.
Additionally, as illustrated in
Therefore, when the motor M is driven to rotationally drive the drive shaft 2 of the hydraulic pump P, the hydraulic oil is sucked from the tank T through the introduction passage D, and pressure oil can be supplied to the hydraulic device E. Additionally, the introduction passage D communicates between the tank T and the suction port 1e of the hydraulic pump P, and the housing portion L is connected in the middle thereof. Therefore, since the coupling 8 in the housing portion L is immersed in the hydraulic oil, spaces between the coupling 8 and the shaft 7 and between the coupling 8 and the drive shaft 2 are lubricated, and the smooth operation of the hydraulic pump P is guaranteed.
In this manner, the pump unit U includes the hydraulic pump P, the motor M, the coupling 8 that couples the drive shaft 2 of the hydraulic pump P and the shaft 7 of the motor M, and the holder H having the housing portion L that is hollow and houses the coupling 8, and the introduction passage D that guides the hydraulic oil to the housing portion L. Therefore, it is possible to lubricate between the coupling 8 and the shaft 7 and between the coupling 8 and the drive shaft 2 with the hydraulic oil guided to the housing portion L, and a seal member that prevents communication between the interior of the hydraulic pump P and the housing portion L is also unnecessary. Therefore, utilizing the hydraulic oil sucked and discharged by the hydraulic pump P, it is possible to lubricate between the coupling 8 and the shaft 7 and between the coupling 8 and the drive shaft 2, and it is unnecessary to use grease. Consequently, according to the pump unit U of the present invention, the overall length of the pump unit U can be shortened, and the mechanical efficiency can be maintained even after long-term use.
Note that since it suffices for the introduction passage D to be able to guide the hydraulic oil to the housing portion L, instead of the introduction passage D as a passage for supplying the hydraulic oil to the suction port 1e of the hydraulic pump P, as in present embodiment, an introduction passage may be provided separately. Since the introduction passage D communicates with a side of the suction port 1e, high pressure on the discharge side does not act on the housing portion L, a load is not applied to the seal around the shaft 7 of the motor M, and energy loss due to friction against the rotational driving of the shaft 7 can be reduced.
Additionally, as in the present embodiment, when the housing portion L is connected to the middle of the introduction passage D communicating between the tank T and the suction port 1e, the hydraulic oil is sucked into the suction port 1e from the tank T via the introduction passage D during driving of the hydraulic pump P. Therefore, the housing portion L is also filled with the hydraulic oil. Therefore, even if a layout such that the tank T is disposed below the pump unit U is adopted, spaces between the coupling 8 and the shaft 7 and between the coupling 8 and the drive shaft 2 are always lubricated during driving of the hydraulic pump P. Consequently, smooth operation of the motor M and the hydraulic pump P can be guaranteed even if the layout such that the tank T is disposed below the pump unit U is adopted. Additionally, since the introduction passage D connected to the housing portion L is connected to the suction port 1e of the hydraulic pump P, it is unnecessary to provide a passage connecting the suction port 1e and the tank T separately from the introduction passage D, and the holder H can be miniaturized.
Furthermore, in the present embodiment, the spline grooves 8a having no break are provided on the inner periphery of the coupling 8 from one end to the other end along the axial direction. When the spline grooves 8a are configured in this manner, the spline grooves 8a can be formed in a single passage from one end to the other end of the coupling 8 by a single cutting operation. Therefore, it becomes unnecessary to adopt such a process to provide a relief formed in an annular groove along the circumferential direction at the center of the coupling 8 and to cut the spline grooves 8a toward the center from both ends of the coupling 8. Then, since imaginary circles passing through the deepest portion of the spline grooves 8a at both ends of the coupling 8 are concentric and do not deviate from each other, eccentricity between the shaft 7 and the drive shaft 2 can be suppressed. Additionally, since the coupling 8, the shaft 7 and the drive shaft 2 are prevented from rotating by the spline grooves 8a and the spline teeth 2a and 7a, backlash corresponding to a fitting gap is allowed between the coupling 8 and the shaft 7 and between the coupling 8 and the drive shaft 2. Therefore, even if a load for eccentrically displacing the drive shaft 2 in a radial direction acts by the action of high pressure during driving of the hydraulic pump P, the load is difficult to be transmitted to the shaft 7, and a load due to the eccentricity is difficult to act on a ball bearing provided between the motor main body 6 and the shaft 7. Consequently, deterioration of the ball bearing in the motor M can be suppressed. Note that to prevent the coupling 8, the shaft 7, and the drive shaft 2 from rotating, instead of forming the spline grooves 8a and the spline teeth 2a and 7a, serration grooves may be provided in the coupling 8, and the serration grooves may be provided on the outer periphery of the shaft 7 and the drive shaft 2, thereby preventing rotation.
Additionally, in the case where a protruding member protruding toward the inner side of the inner periphery of the coupling 8 is provided on the intermediate inner periphery of the coupling 8, the coupling 8 is prevented from falling off from the drive shaft 2 and the shaft 7.
As illustrated in
The cylinder body C includes a cylinder 21, a piston 22 that is movably inserted into the cylinder 21 and partitions the interior of the cylinder 21 into a rod-side chamber R1 and a piston-side chamber R2, a rod 23 inserted in the cylinder 21 and coupled to the piston 22, an external cylinder 24 housing the cylinder 21 therein, a tank T formed between the cylinder 21 and the external cylinder 24, a bottom cap 25 joined with the right end in
The hydraulic circuit LC is configured by including a first on-off valve 28 provided in the middle of a first passage 27 that communicates between the rod-side chamber R1 and the piston-side chamber R2, a second on-off valve 30 provided in the middle of a second passage 29 that communicates between the piston-side chamber R2 and the tank T, a discharge passage 31 that communicates between the rod-side chamber R1 and the tank T, a variable relief valve 32 that can change valve opening pressure provided in the discharge passage 31, and a straightening passage 33 that allows only a flow of the hydraulic oil from the piston-side chamber R2 to the rod-side chamber R1 and a suction passage 34 that allows only a flow of the hydraulic oil from the tank T toward the piston-side chamber R2.
Additionally, the vertical hole 15 leading to the discharge port 1f of the hydraulic pump P in the pump unit U is connected to the rod-side chamber R1 of the cylinder body C through a passage 35. A check valve 36 that blocks only a flow of hydraulic oil from the rod-side chamber R1 to the hydraulic pump P is provided in the middle of the passage 35. Furthermore, the vertical hole 14 leading to the suction port 1e of the hydraulic pump P in the pump unit U is connected to the tank T via a passage 37. In the tank T, the hydraulic oil is stored. Therefore, the hydraulic pump P sucks the hydraulic oil from the tank T and can discharge the pressure oil to the rod-side chamber R1 in the cylinder body C.
Then, the actuator A configured in this manner can be extended and driven when the hydraulic pump P is driven in a state in which the first passage 27 is made a communicating state by the first on-off valve 28 and the second on-off valve 30 is closed. Additionally, the actuator A can be contracted and driven when the hydraulic pump P is driven in a state in which the second passage 29 is made into a communicating state by the second on-off valve 30 and the first on-off valve 28 is closed.
The variable relief valve 32 can adjust the valve opening pressure. Irrespective of the open and closed states of the first on-off valve 28 and the second on-off valve 30, when there is an excessive input in an extending and contracting direction in the actuator A and the pressure of the rod-side chamber R1 exceeds the valve opening pressure, the variable relief valve 32 opens the discharge passage 31 to cause the rod-side chamber R1 to communicate with the tank T. In this manner, in response to the excessive input to the actuator A, the variable relief valve 32 releases the pressure in the rod-side chamber R1 to the tank T to protect the entire system of the actuator A.
In order to cause the actuator A configured in this manner to exert a desired extending-directional thrust force, the first on-off valve 28 is opened, the second on-off valve 30 is closed, and the hydraulic oil is supplied from the hydraulic pump P to the cylinder 21 while the motor M is rotated. In this way, the rod-side chamber R1 and the piston-side chamber R2 are in a communicating state. The hydraulic oil is supplied from the hydraulic pump P to both the rod-side chamber R1 and the piston-side chamber R2. The piston 22 is pushed to the left in
On the other hand, in order to cause the actuator A to exert a desired contracting-directional thrust force, the first on-off valve 28 is closed and the second on-off valve 30 is opened, and then the hydraulic oil is supplied from the hydraulic pump P into the rod-side chamber R1 while the motor M is rotated. In this way, the piston-side chamber R2 and the tank T are in a communicating state, the hydraulic oil is supplied from the hydraulic pump P to the rod-side chamber R1. The piston 22 is pushed to the right in
Additionally, in the actuator A, when both the first on-off valve 28 and the second on-off valve 30 are closed, the rod-side chamber R1, the piston-side chamber R2, and the tank T are connected by being tied in a row by the straightening passage 33, the suction passage 34, and discharge passage 31. In this state, regardless of whether the hydraulic pump P is driven, when the actuator A is extended and contracted by an external force, the pressure in the rod-side chamber R1 is controlled to be the valve opening pressure of the variable relief valve 32. Therefore, the actuator A acts as a passive damper that exerts a thrust force that suppresses the extension. Then, when the current supply to the motor M, the first on-off valve 28, the second on-off valve 30 and the variable relief valve 32 is cut off, the first on-off valve 28 and the second on-off valve 30 are closed and the variable relief valve 32 functions as a pressure control valve, the valve opening pressure of which is fixed to the maximum. Therefore, the actuator A can function automatically as a passive damper in a state in which the power supply is cut off or when the power supply fails.
When the pump unit U is used for the actuator A configured in this manner, since the overall length of the pump unit U is shortened, the overall size of the actuator A is also reduced, and the mountability of the actuator A to various devices is improved.
Note that the hydraulic circuit LC may have a configuration other than the above-described configuration. For example, the hydraulic circuit LC may selectively supply the pressure oil from the pump unit U to one of the rod-side chamber R1 or the piston-side chamber R2 in the cylinder 21 of the cylinder body C and cause the other of the rod-side chamber R1 and the piston-side chamber R2 to communicate with the tank T. Also in this case, the actuator A can extend and contract by supply of the hydraulic oil from the hydraulic pump P. That is, the hydraulic circuit LC may be any hydraulic circuit LC as long as the hydraulic circuit LC can control the extension and contraction of the actuator A by controlling the communicating state among the hydraulic pump P, the rod-side chamber R1, the piston-side chamber R2 and the tank T.
In present embodiment, the hydraulic pump P sucks all the hydraulic oil from the introduction passage D, but the hydraulic pump P may have a suction passage and the introduction passage D may be provided in parallel with the suction passage.
This application claims priority based on Japanese Patent Application No. 2015-180627 filed to the Japan Patent Office on Sep. 14, 2015, and the entire contents of the application are incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-180627 | Sep 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/066381 | 6/2/2016 | WO | 00 |
