JPH01244184A - Pressure controller for variable displacement compressor - Google Patents

Abstract

PURPOSE:To regulate compressor capacity automatically so as to cause fluid pressure in an air tank to become almost constant by operating a passage selector valve for a piston stroke controlling cylinder for its changeover by means of fluid pressure in a pressure tank. CONSTITUTION:What is called an Oldham's coupling is constituted of a first main shaft 6 and a second main shaft 7 as well as an intermediate node member lying between these shafts, and a piston 12 is connected to this intermediate node member 8 via a connecting rod 13. In the case where fluid pressure in a pressure tank 3 is less than the setting pressure, a piston stroke controlling cylinder 23 moves a rotational center of the second main shaft 7 in the piston stroke expanding direction by transfer operation of a passage selector valve 26. Consequently, compressor capacity is increased, and the fluid pressure in the pressure tank 3 goes up by degrees.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pressure control device for a variable displacement compressor, which uses a variable displacement compressor to control fluid pressure within a pressure tank to be substantially constant.

Conventional Technology For example, a reciprocating piston type compressor that utilizes the reciprocating motion of a piston is a typical compressor used as a pressure source for pneumatic equipment, but since the capacity of this reciprocating piston type compressor is always constant, its discharge In order to keep the air pressure in the air tank provided on the side almost constant, some of the air from the air tank can be released to the outside using an unloader valve, or an electric motor that drives the compressor can be used based on the detection of a pressure sensor. It is necessary to perform ON/OFF control of the motor and electromagnetic clutch.

Problems to be Solved by the Invention However, in the former unloader valve method, the air compressed by the compressor is wasted and the loss of drive energy is large. In addition, in the case of the latter, which controls the driving force of the compressor on and off, smooth operation is not possible, and torque fluctuations and vibrations are extremely large. A control circuit is required.

Means for Solving the Problems Accordingly, the present invention automatically maintains a substantially constant pressure by changing the capacity of the compressor depending on the fluid pressure within the pressure tank. That is,
The pressure control device for a variable capacity compressor according to the present invention has a first main shaft having a fixed rotation center, a second main shaft having a movable rotation center, and a second main shaft having a movable rotation center. A variable displacement compressor equipped with a variable piston stroke mechanism comprising: an intermediate joint member that moves as a piston and is linked to a piston; a piston stroke control cylinder that moves the center of rotation of the second main shaft; and a discharge side of the compressor. A flow path switching valve that switches and controls communication between a pressure tank provided in the pressure tank and the pressure chamber of the piston stroke control cylinder, and an actuator that switches and operates the flow path switching valve by fluid pressure in the pressure tank. It is configured.

Operation In the above configuration, the first main shaft, the second main sleeve, and the intermediate joint member between them constitute a so-called Oldham joint, and the piston connects the intermediate joint member, which is the intermediate joint, via a connecting rod. are connected.

Therefore, the reciprocating stroke of the piston is approximately equal to the distance between the rotation center of the first main shaft and the rotation center of the second main shaft, and the compressor capacity is determined accordingly.

If the fluid pressure in the pressure tank is below the set pressure,
By the switching operation of the flow path switching valve, the piston stroke control cylinder moves the rotation center of the second main shaft in the direction of expanding the piston stroke. Therefore, the compressor capacity increases and the fluid pressure in the pressure tank gradually increases. Further, when the fluid pressure in the pressure tank reaches the set pressure, the piston stroke control cylinder moves the second main shaft rotation center in the piston stroke reduction direction by the switching operation of the flow path switching valve. Therefore, the compressor capacity decreases and the pressure gradually decreases.

By repeating such operations, the fluid pressure within the pressure tank is kept substantially constant.

Embodiment FIG. 1 is a configuration explanatory diagram showing an embodiment of a pressure control device for a variable capacity compressor according to the present invention. Note that this embodiment shows an example in which the present invention is applied to an air compressor.

In FIG. 1, l is a variable displacement compressor,
This compressor 1 compresses air by reciprocating movement of a piston 12, and is equipped with a variable piston stroke mechanism 2, which will be described later. An air tank 3 is connected to the discharge boat of the compressor 1 via a passage 4. The air tank 3 primarily stores the air discharged from the compressor 1, and air pressure is supplied from the air outlet 3a to various external pneumatic devices. Note that 5 is a safety valve provided in the air tank 3.

The piston stroke variable mechanism 2 has 1. This utilizes a so-called Oldham joint, and as shown in FIG. 2, the first main shaft 6. It is generally composed of a second main shaft 7 and an intermediate node member 8. The intermediate node member 8 corresponds to the intermediate node in a so-called Oldham joint, and includes a short cylindrical pin portion 9 and a first slider formed on both end surfaces of the pin portion 9 along a direction perpendicular to each other. A piston 12 is connected to the pin portion 9 via a connecting rod 13.

Further, the first main shaft 6 corresponds to one node of the Oldham joint, and the disk portion 14 is in close contact with the end surface of the pin portion 9.
And, the shaft part formed protrudingly on the back surface of this disc part 14! 5, and a guide groove 16 along the radial direction is recessed in the surface of the disk portion 14. This guide groove 16 is fitted with the first slider lO, and restricts the direction of relative movement between the two in one direction. The shaft portion 15 is
Fixed bearing 17 fixed to a compressor case (not shown)
is rotatably supported by. In other words, the first spindle 6
The center of rotation of is fixed.

The second main shaft 7 corresponds to the other node of the Oldham joint, and the disk portion 1 closely contacts the other end surface of the bottle portion 9.
8 and a shaft portion 19 formed on the back surface thereof, and a guide groove 20 is recessed in the surface of the disk portion 18 along the radial direction. The guide groove 20 fits into the second slider 11 of the intermediate node member 8, and also restricts the direction of relative movement between the two to one direction. The shaft portion 19 is rotatably supported by a movable bearing 21 that is movable in a direction perpendicular to the shaft. Note that the rotation center of the second main shaft 7 is located below the fixed rotation center of the first main shaft 6, and the movable bearing 21
The structure is such that when the rotation center moves upward, both rotation centers approach each other.

As shown in FIG. 1, the shaft portion 1 of the first main shaft 6 is
5 is driven by an electric motor 22. Further, an air cylinder 23 for piston stroke control is connected to the movable bearing 21. In this embodiment, the air cylinder 23 is a double-acting cylinder, and has a first pressure chamber 24 and a second pressure chamber 25 above and below the piston 23a.

Reference numeral 26 denotes a passage switching valve that controls the introduction of pressure into each pressure chamber 24 and 25 of the air cylinder 23, and this passage switching valve 26 is connected to an inlet boat connected to the air tank 3 via a passage 28. 26a, and the first air cylinder 26a of the air cylinder 23
．． A pair of outlet boats 26b, 26C connected to the second pressure chamber 24.25, and a pair of atmosphere release boats 26d,
26e, and depending on the sliding position of the spool 27, the air tank 3 can be moved to the first position. It is configured to communicate with either one of the second pressure chambers 24, 25 and at the same time open the other pressure chamber to the atmosphere. Note that a check valve 29 is interposed in the above-mentioned passage 28 leading from the air tank 3 to the artificial port 26a. A piston-type or diaphragm-type actuator 31 is connected to the spool 27 of the flow path switching valve 26 via a rod 30. The pressure chamber 32 of the actuator 31 communicates with the air tank 3 via a passage 33, and a return spring 35 is disposed in the atmospheric pressure chamber 34 so as to face the pressure inside the pressure chamber 32. .

Next, the operation of the pressure control device for a variable displacement compressor configured as described above will be explained.

First, the operating principle of the variable piston stroke mechanism 2 will be explained. That is, in the above configuration, the first main shaft 6, the second main shaft 7, and the intermediate joint member 8 constitute a so-called Oldham joint, and a connecting member is connected to the intermediate joint member 8 corresponding to the intermediate joint of this Oldham joint. The large end of the rod 13 is linked.

As shown in FIG. 3, the rotation center of the first main shaft 6 is 01, the rotation center of the second main shaft 7 is 07, and the intermediate joint member 8 (pin part 9)
As is well known, if the center of rotation is 03, then
The first main shaft 6, the second main shaft 7, and the intermediate joint member 8 rotate in exactly the same phase, and the rotation center 03 of the intermediate joint member 8
revolves on a circle R whose diameter is the line segment 0.0°.

Therefore, when the first main shaft 6 is rotationally driven by the electric motor 22, the piston 1 rotates as the rotation center 03 revolves.
2 moves back and forth, compressing the air.

And the above piston! As is clear from FIG. 3, the reciprocating stroke S during the reciprocating linear motion of the second main axis 6. The distance is approximately equal to the distance between the rotation centers Or and Ot of the second main shaft 7.

Therefore, the movable bearing 21 is moved upward in FIG.
．． ．． If the distance between 02 is reduced, the reciprocating stroke S
becomes shorter, reducing compressor capacity. Conversely, if the movable bearing 21 is moved downward to increase the distance between 0 = and O, the reciprocating stroke S becomes longer and the compressor capacity increases.

In the pressure control device shown in FIG. 1, the position of the movable bearing 21 is automatically controlled based on the air pressure within the air tank 3. That is, when the air pressure in the air tank 3 is below the set pressure of the actuator 31 (determined by the relationship between the spring force of the return spring 35 and the pressure receiving area), the spool 27 is located on the right side in FIG. port 26
a communicates with one exit boat 26b, and the other exit boat 26c communicates with an atmosphere open boat 26e.

Therefore, the air pressure in the air tank 3 is introduced into the first pressure chamber 24 of the air cylinder 23, thereby causing the movable bearing 2!
moves to the lower force. This increases the reciprocating stroke S of the piston 12, that is, the compressor capacity, as described above. Therefore, the air pressure inside the air tank 3 gradually increases.

On the other hand, when the air pressure in the air tank 3 exceeds the set pressure of the actuator 31, the actuator 31 switches the spool 27 of the flow path switching valve 26 to the left in FIG. In this state, the air tank 3 is connected to the air cylinder 2 via the inlet boat 26a and the outlet boat 26c.
The first pressure chamber 24 on the opposite side and communicating with the second pressure chamber 25 of No. 3 is opened to the atmosphere via an outlet boat 26b and an atmosphere release boat 26d. Therefore, the air cylinder 23 is actuated upward by the air pressure in the air tank 3, and the movable bearing 21 is moved upward. As a result, as described above, the reciprocating stroke S of the piston 12, that is, the compressor capacity is reduced. Therefore, an increase in the pressure inside the air tank 3 is suppressed, and when air is flowing out from the air tank 3 to external equipment, the air pressure gradually decreases.

In this way, when the air pressure inside the air tank 3 exceeds the set pressure, the compressor capacity decreases, and when it falls below the set pressure, the compressor capacity increases, so by repeating this operation, the air pressure inside the air tank 3 is released to the outside. Regardless of the amount of supplied air, it is kept approximately constant.

Therefore, ON/OFF control and rotation speed control of the electric motor 22 are not required, and extremely smooth operation can be achieved.

Further, for example, in a situation where no air flows out from the air tank 3 to an external device, the reciprocating stroke S of the piston 12 eventually becomes 0, and no substantial compression action is performed. Therefore, even if the electric motor 22 is rotating,
It becomes a no-load state and energy consumption is significantly reduced.

In addition, in the configuration of the above embodiment, when the movable bearing 21 and the piston 23a of the air cylinder 23 move downward due to their own weight when the operation is not performed for a long period of time, the residual pressure in the air tank 3 is reduced at the next startup. Even if is 0, a large compressor capacity can be secured and the pressure can be increased immediately.

Effects of the Invention As is clear from the above explanation, according to the pressure control device for a variable pot type compressor according to the present invention, the piston stroke control cylinder is mechanically controlled by the fluid pressure in the pressure tank, and the air tank 3 Since the compressor capacity is automatically adjusted so that the fluid pressure inside is approximately constant, there is no need for ON/OFF control of the electric motor or electromagnetic clutch or rotation speed control, resulting in smooth operation with less torque fluctuation and vibration. It becomes possible to perform the following. Furthermore, since the compression action is always performed at the optimum capacity without causing the once compressed fluid to escape to the outside, there is little loss in energy consumption.

[Brief explanation of the drawing]

Fig. 1 is a configuration explanatory diagram showing one embodiment of the pressure control device for a variable displacement compressor according to the present invention, Fig. 2 is an exploded perspective view showing the variable piston stroke mechanism thereof, and Fig. 3 is an explanatory diagram showing the principle of variable piston stroke. It is an explanatory diagram for explanation. l... Compressor, 2... Piston stroke variable mechanism, 3... Air tank, 6... First main shaft, 7...
...Second main shaft, 8...Intermediate node member, 12...Piston, 23...Air cylinder, 26...Flow path switching valve,
31...actuator. Figure 1 Figure 2

Claims (1)

[Claims] (1) A first main shaft with a fixed rotation center, a second main shaft with a movable rotation center, and an intermediate node that moves along an orbital circle whose diameter is the distance between the two rotation centers and is linked to a piston. A variable capacity compressor equipped with a variable piston stroke mechanism comprising: a cylinder for piston stroke control that moves the center of rotation of the second main shaft; a pressure tank provided on the discharge side of the compressor; and a pressure tank for controlling the piston stroke. A pressure control device for a variable capacity compressor, comprising a flow path switching valve that switches and controls communication between a cylinder and a pressure chamber, and an actuator that switches and operates the flow path switching valve using fluid pressure in a pressure tank.