JPS5828441B2 - hydraulic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic drive traveling device, such as a power shovel or a crane, in which a hydraulic pump and a hydraulic motor change their relative positions by straddling a relative movement point such as a swivel table. related to hydraulic circuits such as

When hydraulically driving a device such as a power shovel, it is known that using a variable displacement hydraulic motor has various advantages in terms of operation and control.

However, with a variable displacement hydraulic motor, it is necessary to arbitrarily or automatically change its theoretical displacement volume by some control input.

Power shovels and the like must be controlled arbitrarily by the driver, but the following problems arise when doing so.

For example, in a power excavator, the driver and prime mover,
Hydraulic pumps, hydraulic fluid tanks, etc. are located at the top of the revolving body, where they move relative to each other, and the hydraulic motor is installed at the bottom of the vehicle body, which does not rotate. The hydraulic motor is normally connected to the hydraulic motor through a pivot joint or swivel joint provided at the center of rotation.

Since the driver is on the upper part of the revolving structure, the control signal to the variable displacement hydraulic motor is necessarily generated at the upper part of the revolving structure, and is received by the control cylinder of the hydraulic motor located in the lower part of the revolving structure, so the hydraulic pressure signal is If this is used, this signal liquid path will also be transmitted via the swivel joint.

As the number of liquid paths passing through the swivel joint increases across relative movement points, the structure of the swivel joint becomes complicated, causing problems such as leaks, causing operational inconvenience, and increasing costs. .

Prior to a detailed description of the present invention, a conventional example will first be described with reference to FIGS. 1 and 2 in order to better understand the present invention.

In FIG. 1, a hydraulic pump P1 driven by a prime mover E
．． P2 is adapted to supply pressurized liquid to the actuator via liquid paths 1 and 2, respectively.

Since these channels 1 and 2 are each connected to a similar circuit, only the channel 1 of the hydraulic pump P1 is illustrated.

The fluid path 1 is connected to a variable displacement hydraulic motor 5 via a switching valve 3 and a brake valve 4 that change the direction of the hydraulic fluid supplied from the hydraulic pump to the hydraulic motor.

6 in the figure is a safety valve.

The variable displacement hydraulic motor 5 is adapted to control the amount of pushing and displacing by means of a variable angle device 7.

This angle changing device 7 is operated by the hydraulic pressure from the signal liquid passages 8 and 9, and is operated by the hydraulic pressure pump P1. Pressure liquid from P2 passes through the shuttle valve 10 and the switching valve 11 to the liquid path 8.
or 9.

12 in the figure is a brake device, arrow R indicates a turning point, that is, a relative movement point, and the hydraulic motor side A on the right side of the figure
is the fixed or lower part of the vehicle body, and the left hydraulic void side B shows the swinging or upper part of the rotating body.

In the control circuit of such a variable displacement hydraulic motor, two signal liquid paths 8,
9 must flow through the swivel joint.

If the variable displacement device T of the variable displacement hydraulic motor 5 is made of a spring balance type, only one signal fluid path is needed for the variable displacement device T.

An example of such a circuit is shown in FIG. 2, in which parts corresponding to those in FIG. 1 are given the same reference numerals.

In the example shown in FIG. 2, the piston 73 in the control cylinder 71 of the angle changer T takes a position where the hydraulic pressure in the chamber 74 introduced from the liquid path 8a and the spring 72 are balanced, and the piston 73 moves. The desired control position is obtained by

However, in the case of Fig. 2, the pressing force of the spring 72 must be quite strong to overcome the large load of the angle changer, and a cylinder with a large diameter is required to overcome the strong spring. There was a drawback that.

In the case of FIG. 1, since hydraulic pressure acts on the left and right sides of the piston in the cylinder, control can be achieved with a relatively small cylinder.

As described above, the prior art has the disadvantage that if the number of signal liquid paths is one, the control cylinder will inevitably become larger.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a hydraulic circuit that uses only one signal hydraulic path and can downsize the control cylinder of a variable displacement hydraulic machine.

Therefore, according to the present invention, there is provided a hydraulic pump and a hydraulic motor which are provided across a relative moving part and whose relative positions change. A switching valve is provided in the fluid path to change the direction of the hydraulic fluid supplied from the hydraulic pump to the hydraulic motor, and at least one of the hydraulic pump and the hydraulic motor is A variable displacement hydraulic machine,
The variable displacement hydraulic machine has a control cylinder whose piston can be switched between two positions to control its theoretical displacement to small or small. In a hydraulic circuit in which the speed of a hydraulic motor is switched between high and low speeds, the piston of the control cylinder has different pressure-receiving areas on both sides, and the control cylinder with the smaller pressure-receiving area of the piston A single liquid path is connected to the chamber that does not cross the relative movement points between the hydraulic pump side and the hydraulic motor side, and the discharge pressure of the hydraulic pump is introduced through this liquid path. In addition, in the chamber of the control cylinder on the side where the pressure receiving area of the piston is larger, a swivel joint is provided that spans the relative movement area between the hydraulic pump side and the hydraulic motor side.
This signal liquid path is connected to a switching valve that is independent of the switching valve provided in the liquid path that connects the hydraulic pump and the hydraulic motor. A hydraulic circuit is provided in which the valve can be switched to drain the signal fluid path or to introduce the discharge pressure of the hydraulic pump into the chamber of the control cylinder on the side of the piston having a larger pressure-receiving area through the signal fluid path. .

In this way, only one signal fluid path is required to be provided in the swivel joint across the hydraulic pump side and the hydraulic motor side, which simplifies the structure of the swivel joint and solves problems such as leaks. can also be suppressed as much as possible.

In addition, the control cylinder uses a piston with different pressure-receiving areas on both sides, and the discharge pressure of the hydraulic pump is introduced into each chamber of the control cylinder divided by the piston, and the position of the piston is determined by the difference in the pressure-receiving area of the piston. Since it can be switched between two positions, the discharge pressure of the hydraulic pump is introduced into only one chamber of the control cylinder divided by the piston, and a spring is inserted into the other chamber, and the spring controls the discharge pressure of the hydraulic pump. The control cylinder can be made smaller in size compared to the one to be competed with.

The present invention will be described in detail below with reference to FIGS. 3 and 4.

In FIG. 3, parts corresponding to those in FIGS. 1 and 2 are designated by the same reference numerals.

The angle changing device 7 of the variable displacement hydraulic motor 5 is connected to the control cylinder 2
0, a piston 21 for controlling the displacement of the variable displacement hydraulic motor 5 is provided in the control cylinder 20, and effective pressure receiving surfaces S1. S
20 areas are different, and usually about 2S1=82 is preferable.

In the drawing of the piston 210, the discharge pressure of the hydraulic pump P1 is introduced into the left chamber 23, that is, the chamber with a smaller effective pressure receiving area, from the liquid path 26 via the shuttle valve 25.
This pressure pushes the piston 21 to the right in the drawing.

Further, a spring 24 is housed in the chamber 23 and presses the piston 21 to the right in an auxiliary manner.

The liquid passage 26 is on the hydraulic pump side B which is on the turning side from the turning point R.
It stays on the fixed side, the hydraulic motor side A, without coming out.

Therefore, it is not necessary to provide a swivel joint in this liquid path 26.

Note that the throttle 27 limits the moving speed of the piston 21.

In addition, a liquid passage 8 is connected to the right chamber 22, that is, the chamber with a larger effective pressure receiving area, through a shuttle valve 10 and a manual switching valve 11.
The highest pressure among the plurality of hydraulic pumps P1 and P2 is supplied by a, or is released (drained) to the atmosphere.

This selection is operated by the manual switching valve 11, and the illustrated state is drained.

The fluid path 8a extends between the fixed side, ie, the hydraulic motor side A, and the articulated side, ie, the hydraulic pump side B. Although not shown, a swivel joint is provided at the pivot point R.

With the control cylinder 200 chamber 22 drained via the switching valve 11 as shown in the figure, the hydraulic pumps P1 and P2 are driven,
When the switching valve 3 is switched from the neutral position, the discharge pressure of the hydraulic pump P1 is introduced into the chamber 23 of the control cylinder 20 through the liquid path 26, and the piston 21 is held at the right end position.

In this state, the displacement capacity of the hydraulic motor 5 is, for example, small, and the hydraulic motor 5 rotates at high speed with low torque.

When the manual switching valve 11 is switched to the opposite position as shown, the chamber 2
2, the discharge pressure of the hydraulic pump is introduced through the liquid path 8a.

This pressure is designed to be higher than the pressure in the chamber 23.

That is, the pressure source of the manual switching valve 11 is connected to the hydraulic pump P1. by the shuttle valve 10. The highest pressure of P2 is selected, and even if the hydraulic pump P□ is higher, the pressure of chamber 22 is selected.
The liquid path 8a leading to the chamber 23 communicates with the liquid path 1 on the upstream side of the liquid path 26 leading to the chamber 23, and the pressure in the chamber 22 is higher than that in the chamber 23.

Since the pressure receiving area S2 of the piston on the chamber 22 side is larger (about twice) than the pressure receiving area S1 of the piston on the chamber 23 side, the piston 21 is held at the left end position.

In this state, the displacement of the hydraulic motor 5 is, for example, a dog, and the hydraulic motor 5 rotates at a low speed with high torque.

Note that in this embodiment, the hydraulic pressure introduced into the chamber 22 of the control cylinder 20 is higher than the hydraulic pressure introduced into the chamber 23, but it is not necessarily necessary to do so, and the pressure may be the same. In some cases, the hydraulic pressure introduced into the chamber 22 may be lower than the hydraulic pressure introduced into the chamber 23.

In short, the pressure may be such that when hydraulic pressure is introduced into the chamber 22, the piston 21 is held at the left end position due to the difference in the pressure receiving area of the piston 21.

However, if the hydraulic pressure introduced into the chamber 22 is made higher than the hydraulic pressure introduced into the chamber 23, the holding force of the piston 21 at the left end position will be ensured.

Although the present invention has been described in the above embodiments with respect to a control device for a variable displacement hydraulic motor of a power shovel or the like, the present invention can also be implemented in a variable displacement hydraulic pump.

FIG. 4 shows an example in which a variable displacement hydraulic pump 31 is provided on the chassis side of a truck crane, and a fixed displacement hydraulic motor 32 and a control valve 33 are provided on the upper part of the revolving body for driving a winch, etc. .

In the figure, the right side of the arrow R indicates the upper part of the revolving body, and the left side thereof indicates the chassis side, and 34 is a switching valve.

In this embodiment as well, the angle change device I controls the pump 31 as in the case of FIG.

The other configurations are substantially the same as in FIG. 3.

In this embodiment as well, the number of signal liquid passages 35 can be reduced to one, and the angle changing device can be made smaller.

Note that the spring used in the control cylinder in Figs. 3 and 4 is an auxiliary one, and the piston in the control cylinder is activated when the hydraulic pump is stopped, that is, when there is no control pressure. This is to prevent the user from becoming misoriented.

Therefore, since this spring does not require a particularly large force, the action of this spring can be ignored in terms of operation.

As explained above, according to the present invention, a variable displacement hydraulic machine, a variable displacement hydraulic motor in the embodiment shown in FIG. 3, and a variable displacement hydraulic motor in the embodiment shown in FIG. To displace the pressure pump, if the chamber on the side where the piston pressure receiving area of the control cylinder that controls the capacity is large is drained using the switching valve installed in the signal liquid path, the liquid that is constantly introduced into the side chamber on the side where the piston pressure receiving area is small can be drained. The piston is held in one position by the pressure, the rightmost position in the drawing, and the displacement of the variable displacement hydraulic machine is assumed to be small, for example, and the hydraulic motor rotates at high speed with low torque. (if the variable displacement machine is a hydraulic pump), or a hydraulic motor rotates at high torque and low speed (if the variable displacement machine is a hydraulic pump).

In addition, if the switching valve is switched and the discharge pressure of the hydraulic pump is introduced into the chamber on the side of the control cylinder where the piston pressure receiving area is large, the piston is held in the other position due to the difference in the pressure receiving area of the piston, which is the left end position in the drawing. For example, the displacement of a pressure machine is like a dog, and a hydraulic motor has a high torque and low speed rotation (
When the variable displacement hydraulic machine is a hydraulic motor), or the hydraulic motor rotates at high speed with low torque (when the variable displacement machine is a hydraulic pump).

In this case, only one signal fluid path is required with a swivel joint installed across the hydraulic pump side and the hydraulic motor side, which simplifies the structure of the swivel joint and also reduces problems such as leaks. can also be suppressed as much as possible.

In addition, a control cylinder with different pressure-receiving areas on both sides of the piston is used, and the discharge pressure of the hydraulic pump is introduced into each chamber of the control cylinder divided by the piston, and the position of the piston is changed between the two by the difference in the pressure-receiving area of the piston. Since the control cylinder is switched between two positions, the discharge pressure of the hydraulic pump is introduced into only one chamber of the control cylinder divided by the piston, and a spring is inserted into the other chamber, so that the discharge pressure of the hydraulic pump can be adjusted between the spring and the discharge pressure of the hydraulic pump. The control cylinder can be made smaller compared to its rival.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a hydraulic circuit of a conventional variable displacement hydraulic motor, Fig. 2 is another conventional circuit diagram, and Fig. 3 is a hydraulic circuit of a variable displacement hydraulic motor according to the present invention. FIG. 4 is a circuit diagram showing a hydraulic circuit of a variable displacement hydraulic pump according to the present invention. Pl, P2... pump, 5... variable displacement hydraulic motor, 7... angle variable device, 20...
... Control cylinder, 21 ... Piston, 2
2, 23...room, 8 a s35...
Signal liquid path, 11, 33...Switching valve, 31...
...Variable displacement hydraulic pump.

Claims (1)

[Claims] 1. It has a hydraulic pump and a hydraulic motor which are provided across a relative movement point and whose relative positions can be changed, and the hydraulic pump and the hydraulic motor are connected by a liquid path provided with a swivel joint, The hydraulic pressure is provided with a switching valve that changes the direction of the pressure fluid supplied from the hydraulic pump to the hydraulic motor, and at least one of the hydraulic pump and the hydraulic motor is a variable displacement hydraulic machine. In the variable displacement hydraulic machine, the theoretical displacement is controlled to small or small by a side cylinder whose piston position is switched between two positions, and the piston of the control cylinder In a hydraulic circuit in which the speed of the hydraulic motor is switched between high and low speeds by switching the position of the piston, the piston of the control cylinder has different pressure receiving areas on both sides; A single fluid path that does not straddle the relative movement points of the hydraulic pump side and the hydraulic motor side is connected to the chamber of the smaller control cylinder, and the discharge pressure of the hydraulic pump is introduced through this fluid path. In addition, in the chamber of the control cylinder on the side where the pressure receiving area of the piston is larger, a single signal liquid is provided via a swivel joint, spanning the relative movement points of the hydraulic pump side and the hydraulic motor side. The signal fluid path is provided with a switching valve independent of the switching valve provided in the fluid path connecting the hydraulic pump and the hydraulic motor, and the switching valve is connected to the signal fluid path. 1. A hydraulic circuit characterized in that the hydraulic circuit can be switched to drain the hydraulic pump or to introduce the discharge pressure of the hydraulic pump into the chamber of the control cylinder on the side of the piston having a larger pressure-receiving area by means of the signal liquid passage.