JP4128073B2 - Piston pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piston pump that reciprocates a plunger and repeats a suction stroke and a discharge stroke.
[0002]
[Prior art]
As shown in FIG. 2, the conventional piston pump A includes a cam mechanism 1 as a drive source. When the cam nose of the cam mechanism 1 rotates to a position where it abuts against the tip of the plunger 2 as shown in the drawing, the plunger 2 is pushed in along with the rotation, and the hydraulic oil in the oil chamber 3 is discharged.
A spring 4 is incorporated in the plunger 2. When the cam mechanism 1 rotates 180 degrees from the illustrated position, the plunger 2 is pushed back by the spring force of the spring 4, so that the hydraulic oil is sucked into the oil chamber 3.
In this way, the pump action is performed by repeating the suction and discharge of the hydraulic oil.
[0003]
By the way, a piston pump originally discharges hydraulic oil intermittently. Therefore, if the piston pump is continuously used, the pulsation is intense. This pulsation causes noise and impact. Considering this, the use of piston pumps is quite limited. For example, there is a case where the actuator completes one operation with a discharge amount obtained by one effective stroke of the plunger.
[0004]
The fact that there are few scenes used for applications that require continuous operation as described above may be that the pump is actively stopped when not in use to reduce energy loss.
Thus, in order to minimize energy loss, in the conventional piston pump A, the left end surface of the plunger 2 is pressed against the cover 5 side, the plunger 2 is kept in the non-operating position, the pump action is stopped, and the cam mechanism 1 is Rotate idly. While the cam mechanism 1 is idling, no frictional resistance is generated at the contact portion between the body 6 and the plunger 2, so that the power energy is minimized.
[0005]
Thus, in order to keep the plunger 2 in the non-operating position, the conventional piston pump A is realized by applying pressure to the pilot chamber 7 .
That is, the plunger 2 and the body 6 are combined to provide the pilot chamber 7 around the plunger 2. As the pressure in the pilot chamber 7 increases, the pressing force on the plunger 2 also increases. Therefore, the plunger 2 moves to the inoperative position against the spring 4 and maintains this position. Here, maintaining the non-operating position refers to a state in which the plunger 2 is placed outside the operating range of the cam mechanism 1.
When the plunger 2 is in the non-operating position, the cam mechanism 1 and the plunger 2 are separated from each other by power, so the plunger 2 does not reciprocate and the cam mechanism 1 rotates idly.
[0006]
Here, when a high pressure is applied to the pilot chamber 7, the pressure oil in the pilot chamber 7 may leak from between the plunger 2 and the body 6. In order to prevent this, the pilot chamber 7 is sealed between the plunger 2 and the body 6 at two points so as to be sandwiched therebetween. That is, an annular recess is formed on the outer periphery of the plunger 2, and the seal members 8 and 9 are attached to the annular recess. As this sealing member, an O-ring made of rubber or the like is used.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-217551
[Problems to be solved by the invention]
In the above conventional example, when the plunger 2 performs a pumping action, the plunger 2 slides while contacting the body 6. However, since the seals 8 and 9 are provided between the plunger 2 and the body 6, friction caused by the seals 8 and 9 occurs when the plunger 2 slides. Moreover, since the seals are provided at two places, the total friction of each becomes larger. The effective force acting on the plunger 2 is killed by this total friction. Therefore, the suction action / discharge action of the piston pump is deteriorated and the piston pump does not operate smoothly.
[0009]
If the plunger 2 that is difficult to move is moved smoothly, the cam mechanism 1 that is a drive source requires a large amount of power. That is, since the friction is generated by the presence of the seal members 8 and 9, a large power is required to move the plunger 2 compared to the case without the seal member. In other words, power loss is caused by the presence of seal friction.
This invention makes it a subject to reduce the loss of this motive power. It is also an object of the present invention to realize a smooth pumping action at the same time.
[0010]
[Means for Solving the Problems]
In the first invention, the plunger is incorporated into the body so as to be reciprocally movable, and the plunger is reciprocated by the driving force of the drive source to repeat the suction stroke and the discharge stroke, while the plunger is kept in the non-actuated position. In a piston pump configured to separate the drive source, a pilot chamber is provided on the outer periphery of the sleeve while a sleeve that is movable relative to the body and the plunger is interposed between the body and the plunger. in moves the sleeve, the moving force of the sleeve, having the features a plunger in that the structure is moved to the non-actuated position disconnecting the power manner from the drive source.
The second invention is characterized in that, in the first invention, a metal seal is formed by a contact portion between the sleeve and the plunger.
The third invention is characterized in that, in the first or second invention, the body and the sleeve are sealed by a sealing member such as an O-ring.
A fourth invention is characterized in that, in any one of the first to third inventions, the sleeve and the plunger are made of an iron-based material while the body is made of an aluminum-based material.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a piston pump B according to an embodiment of the present invention. In addition, the same code | symbol is used about the component similar to a prior art example.
As shown in FIG. 1, a sleeve 10 is interposed between the plunger 2 and the body 6. Accordingly, the plunger 2 does not directly contact the body 6 but contacts the inner peripheral surface of the sleeve 10. The outer peripheral surface of the plunger 2 and the inner peripheral surface of the sleeve 10 have high dimensional accuracy, and the gap between the outer periphery of the plunger 2 and the inner periphery of the sleeve 10 is minimized. In this way, by keeping the gap between the outer periphery of the plunger 2 and the inner periphery of the sleeve 10 to a minimum, the contact surface between the plunger 2 and the sleeve 10 performs a metal seal function.
[0012]
The sleeve 10 is slidably in contact with the inside of the body 6, and the sleeve 10 and the body 6 are combined to provide a pilot chamber 11 on the outer periphery of the sleeve 10. When pilot pressure is introduced into the pilot chamber 11, the pressure oil in the pilot chamber 11 may leak out. In order to prevent this, an annular recess is formed on the outer periphery of the sleeve 10, and the seal member 12 is attached to the annular recess. Further, an annular recess is formed on the inner periphery of the body 6, and the seal member 13 is attached to the annular recess. That is, the pilot chamber 11 is positioned between the seal members 12 and 13 to prevent the hydraulic oil from the pilot chamber 11 from leaking.
A spring 14 is provided between the sleeve 10 and the cover 5, and the spring force of the spring 14 is applied to the sleeve 10.
[0013]
A flange portion 15 is provided at the inner end of the plunger 2 so that the sleeve 10 abuts against the flange portion 15 when the sleeve 10 moves to the left in FIG. Accordingly, when the sleeve 10 is moved leftward in the drawing and its end is in contact with the flange 15, when the sleeve 10 is further moved leftward, the moving force is applied to the plunger 2 via the flange 15. Is transmitted to. When the moving force of the sleeve 10 is transmitted to the plunger 2 in this way, the plunger 2 moves to the inoperative position against the spring 4. And when the edge part of the plunger 2 is pressed on the cover 5 side, the said plunger 2 will arrive at a non-operation position.
When the plunger 2 is moved to the non-operation position, the pilot pressure is naturally introduced into the pilot chamber 11. With this pilot pressure, the sleeve 10 can move against the spring force of the spring 14. Here, the pilot pressure guided to the pilot chamber 11 is controlled by switching a pilot valve (not shown).
As described above, when the plunger 2 remains in the non-operating position, the plunger 2 is powered off from the cam mechanism 1 as a driving source, and the piston pump B does not perform a pumping action.
[0014]
When the plunger 2 is put into an operating state, the pilot pressure is communicated from the pilot chamber 11 to a tank (not shown). When the pilot chamber 11 communicates with the tank, the sleeve 10 moves to the right of the screen by the spring force of the spring 14 and reaches the position shown in the figure. Thus, since the end point of the sleeve 10 that has pressed the flange portion 15 of the plunger 2 against the cover 5 moves to the right, there is a space that allows the flange portion 15 to move between the cover 5 and the sleeve 10. Secured. As a result, the plunger 2 can reciprocate. When the plunger 2 is reciprocating, the sleeve 10 is stationary.
[0015]
Thus, the sleeve 10 moves when the plunger 2 is switched from the operating state to the non-operating state or from the non-operating state to the operating state. However, when the plunger 2 is kept in an operating state, that is, when performing a pumping action, the sleeve 10 is stationary at the illustrated position. Therefore, when the plunger 2 reciprocates, friction between the seal member 12 on the outer periphery of the sleeve 10 and the seal member 13 on the inner periphery of the body 6 does not occur.
[0016]
When the plunger 2 reciprocates, the inner peripheral portion of the sleeve 10 slides. At this time, the frictional resistance of the metal seal described above occurs at the contact surface between the sleeve 10 and the plunger 2. However, the frictional resistance of the metal seal is very small compared to the friction of the seal members 12 and 13.
[0017]
In this embodiment, when the plunger 2 performs a pump action, the large friction due to the seal member as in the conventional example does not occur. Instead, a frictional resistance is generated by a metal seal between the plunger 2 and the sleeve 10, but this frictional resistance is negligible compared to the friction of the seal member. Therefore, when the plunger 2 performs a pumping action, the large friction caused by the sealing member as in the conventional example does not occur, so that the plunger 2 operates smoothly.
Thus, since the plunger 2 operates smoothly, large power is not required unlike the conventional example. That is, power loss can be reduced.
[0018]
Next, in the piston pump B, the plunger 2 and the sleeve 10 can be made of iron, and the body 6 can be made of aluminum. The reason is as follows.
In the conventional piston pump A, the plunger 2 directly contacts the body 6, and the plunger 2 slides on the inner peripheral surface of the body 6 during the operation of the pump. Both 6 and plunger 2 must be iron-based.
However, as in this embodiment, since the sleeve 10 moves only when the plunger 2 is switched from the operating position to the non-operating position or from the non-operating position to the operating position, the sleeve 10 frequently slides with the body 6. It is not a thing. Therefore, the wear resistance between the sleeve 10 and the body 6 need not be considered so much. Therefore, the body 6 can be made of a soft aluminum material.
[0019]
【The invention's effect】
In the first invention, since a sleeve is provided between the plunger and the body and the plunger slides inside the sleeve, a seal such as an O-ring is unnecessary around the plunger. Therefore, the friction of the seal does not occur when the plunger moves during the pump operation. Since the plunger operates smoothly as much as friction does not occur, the power loss of the drive source can be reduced. Moreover, since the slidability of the plunger is stable, the pump suction action and the discharge action are improved.
[0020]
In the second invention, the same iron-based material is used for the sleeve and the plunger, and the gap between the inner periphery of the sleeve and the outer periphery of the plunger is minimized. Therefore, when the plunger moves, the contact surface between the plunger and the sleeve performs a metal seal function. This metal seal has negligible frictional resistance compared to a seal such as an O-ring made of rubber or the like. Therefore, since the plunger operates smoothly, the power loss of the drive source can be reduced.
[0021]
In the third invention, since the seal member such as an O-ring is provided between the body and the sleeve, it is possible to prevent the pressure oil in the pilot chamber from leaking between the body and the sleeve when the sleeve moves. . On the other hand, the sleeve moves when the plunger is switched between the operating state and the non-operating state. Therefore, the number of movements of the sleeve is small. Therefore, the influence by the friction of the seal member can be reduced as compared with the conventional example.
[0022]
In the fourth invention, a light metal such as aluminum can be used for the body. Therefore, the weight of the piston pump can be reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view of a piston pump according to an embodiment of the present invention.
FIG. 2 is a sectional view of a conventional piston pump.
[Explanation of symbols]
1 Cam Mechanism 2 Plunger 6 Body 10 Sleeve 11 Pilot Chambers 12 and 13 Sealing Member

Claims (4)

The plunger is incorporated into the body so that it can reciprocate, and the plunger is reciprocated by the driving force of the drive source to repeat the suction stroke and the discharge stroke, while the plunger is kept in the non-operating position to separate the plunger from the drive source. In this piston pump, a sleeve that is movable relative to the body and the plunger is interposed between the body and the plunger, while a pilot chamber is provided on the outer periphery of the sleeve, and the sleeve is moved by the pressure action of the pilot chamber. together, the moving force of the sleeve, piston pump was configured to move the plunger to the non-actuated position disconnecting the power manner from the drive source. The piston pump according to claim 1, wherein a metal seal is formed at a contact portion between the sleeve and the plunger. The piston pump according to claim 1 or 2, wherein the body and the sleeve are sealed with a sealing member such as an O-ring. The piston pump according to any one of claims 1 to 3, wherein the sleeve and the plunger are made of an iron-based material, and the body is made of an aluminum-based material.

Images