JPH0255143B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an accumulator filling control device for supplying hydraulic oil for each injection cycle to an accumulator provided for high-speed injection in an injection circuit of a die-casting machine or the like. .

Conventionally, when a piston-type accumulator and a gas accumulator are used in combination as an accumulator installed in the injection circuit of a die-casting machine or an extrusion press, a circuit such as the one shown in Fig. 1 has been known. .

In Figure 1, 1 is a pump, 2 is a motor, and 3
4 is an injection cylinder, 4 is a switching valve for forward and backward movement of the injection cylinder, 5 is a piston-type accumulator with a slidably built-in piston 5a, 6 is a gas accumulator, 7 is a valve for high-speed injection, and 8 is a gas accumulator. A switching valve is provided in a circuit that supplies hydraulic oil to the lower part of the mulrator 6, 9 is a pressure switch, 10 is a pressure gauge, 11 is a relief valve, 12 to 16 are on-off valves, 17 is a check valve, and 18 is a tank. .

However, in the conventional device as shown in FIG. Open the
There was a case where the switching valve 8 was switched to supply hydraulic oil into the gas accumulator 6, but normally the on-off valve 14 is closed and the switching valve 8 also shuts off the hydraulic oil, and this is done every injection cycle. Hydraulic oil is supplied to the accumulator only to the piston type accumulator 5 with the on-off valve 12 kept open.

In these conventional devices,
As described in Publication No. 49-29405 and Japanese Patent Publication No. 54-30373, it is possible to reduce the volume of a piston type accumulator and to reduce the filling time when filling nitrogen gas from a commercially available gas bottle into a gas accumulator. The main focus was on shortening the time, but little consideration was given to changes in gas temperature.

That is, the pressure of the gas such as nitrogen gas filled in the gas accumulator 6 changes in proportion to the temperature change if the volume is kept constant. That is, when P0 is the pressure at absolute temperature T0 and P1 is the pressure at absolute temperature T1, P1=PO×T1/T0.

However, die-casting machines generally start work at a temperature of around 10℃ in winter, and
The ambient temperature in steady state is approximately 50°C. Then, the pressure increases in response to this temperature change, and the amount of pressure change due to this temperature difference is approximately 1.14 times, and the effect on die-cast products is a value that cannot be ignored. Moreover, this change does not stabilize rapidly, and changes over 30 to 60 shots after the start of work, and in some cases over about half a day. Therefore, this causes a decrease in product yield.

Of course, in the conventional device, it is also conceivable to open and close the on-off valves 14 and 15 each time depending on the temperature rise of the hydraulic oil and gas, and to manually adjust the amount of oil in the gas accumulator 6 each time. It is virtually impossible to manually perform this adjustment every cycle, and it cannot be performed accurately.

Furthermore, in the conventional device, a mechanical stopper for regulating the upper limit of the rise of the piston 5a is simply attached to the top of the piston type accumulator 5 using an adjustment screw, and the upper limit position of the piston 5a is adjusted for each shot. Some models were designed to keep the piston 5a at a fixed position in the middle of the gas accumulator 5, but this did not include the idea of adjusting the position of the piston 5a according to the temperature of the gas in the gas accumulator 6. Even if the position of the mechanical stopper was manually adjusted every cycle to regulate the stop position of the piston 5a according to the gas temperature, it would be virtually impossible to do so accurately. It cannot be done.

The present invention eliminates these drawbacks and automatically adjusts the gas pressure, thereby making it possible to perform injection under stable injection conditions from the start of work, thereby improving product quality.

The present invention includes an accumulator that is a combination of a piston-type accumulator and a gas accumulator, and a piston stop device that can stop the piston is provided on the gas chamber side of the piston-type accumulator so that the position can be adjusted freely. It is equipped with a pressure detection device that directly or indirectly detects the gas pressure, and controls the operating position of the piston stop device based on the output signal from the pressure detection device when the piston of the piston type accumulator hits the piston stop device. Equipped with a water control device.

Next, the present invention will be explained in detail with reference to an embodiment shown in the drawings. In FIG. 2, the same parts as those shown in FIG. 1 are designated by the same reference numerals as shown in FIG. 1, and the explanation thereof will be omitted.

In one embodiment shown in FIG. 2, the top of the piston type accumulator 5 and the gas accumulator 6
The tops of the piston 5a are connected to each other, and the piston 5a stops rising at the top or midway of the piston-type accumulator 5 at a position where an amount of hydraulic oil equal to or greater than the minimum amount required for injection is secured in the piston-type accumulator 5. A piston stop device 19 is provided whose position can be adjusted in the vertical direction. 20 is the piston stop device 1
This is a position control device for moving the movable portion of No. 9. As the piston stop device 19, a device such as a magnetic switch which also serves as a position detection device may be used, or a simple movable mechanical stopper may be used. However, in any case, the vertical position of the piston stop device 19 can be controlled by signals from a control device 22, which will be described later.

On the hydraulic oil supply side of the piston type accumulator 5, a check valve 17a or an electromagnetic switching valve is provided on the pump 1 side of the on-off valve 12, which is always open during operation. Further, a pressure detector 21 for directly detecting the pressure of gas within the gas accumulator 6 was attached to the gas accumulator 6. However, in order to indirectly detect the pressure of the gas in the gas accumulator 6, the pressure detector 21 may be installed at a position where it can detect the pressure of the hydraulic oil in the gas accumulator 6. 22 is a control device, which includes a pressure sensor 2;
1 receives an electrical input in response to the pressure detected by the position control device 20;
The position of the piston stop device 19 can be appropriately controlled before the next cycle. In addition, in the piston-type accumulator 5, in order to ensure the minimum amount of hydraulic oil required for injection each time, the piston stop device 19 is prevented from lowering below a pre-instructed position. 23 is pump 1
This is a switching valve 23 for unloading.

Next, the operation of the accumulator filling control device shown in FIG. 2 will be explained.

During the injection work, the on-off valves 12 and 13 are always open, and the on-off valves 14, 15, and 16 are always closed.

When the pump 1 is rotated and the on-off valve 12 is opened to start work, the piston 5a in the piston type accumulator 5 approaches the upper limit and is stopped by the action of the piston stop device 19. 1 to a certain extent to open the on-off valve 12, and at the time of each injection, before the pump 1 is loaded on-load to fill the piston-type accumulator 5 with hydraulic oil, the pressure detection device 21 is The gas pressure is detected, and the vertical position of the piston position stop device 19 is adjusted accordingly by the actions of the control device 22 and the position control device 20.

Of course, in order to obtain a predetermined gas pressure, the volume of gas that needs to be set can be set in advance, so the pressure sensor 21 detects the amount based on this. If the pressure has not reached the specified pressure, raise the piston stop device 19 to reduce the gas volume, and conversely, if the pressure is higher than the specified pressure, lower the piston stop device 19 to reduce the gas volume. Control as appropriate to increase the volume of. Then, the gas pressure in the gas accumulator 6 is set to a predetermined pressure.

In this way, in the embodiment shown in FIG. 2, the pressure detection device 21 that directly or indirectly detects the pressure of the gas in the gas accumulator 6 is used. Then, the position of the piston stop device 19 is controlled by the output signal from the pressure detection device 21 when the piston 5a of the piston type accumulator 5 hits the piston stop device 19. However, if the pressure is low and it is necessary to raise the piston stop device 19, it can be done immediately, but conversely, if the pressure is high and it is necessary to lower the piston stop device 19, the high pressure is raised below the piston 8a. If you cannot do it right away because it is working, then do it before the next cycle.

The piston type accumulator 5 can be installed upside down or in any other position by connecting the hydraulic oil supply side to the pump 1 or injection cylinder 3 and the gas action side to the gas accumulator 6. You can leave it there.

In this way, in the present invention, the structure described in the claims is adopted, and the gas pressure of the accumulator is automatically adjusted in response to pressure changes without ignoring pressure changes in hydraulic oil or gas. In addition, this adjustment can be made in accordance with the gas pressure for each injection cycle, so in die-casting machines, etc., the hydraulic oil or gas pressure is still relatively low after work has started. By controlling the piston-type accumulator, you can of course easily obtain the specified amount of oil in the piston-type accumulator, but also the specified gas pressure every time, so you can quickly start obtaining high-quality products. In addition, the product can be injected in response to requests from the downstream process, and the product can be sent to the downstream process promptly.
A so-called billboard system can be used. Even when the pressure of hydraulic oil or gas is relatively high, the predetermined gas pressure and oil amount can be automatically and easily obtained through control, ensuring that high-quality products are always obtained. can. Note that the gas pressure is high when the hydraulic oil is completely filled and low after injection, and changes during one cycle, but when controlling based on gas pressure, the specified amount of hydraulic oil is in the piston-type accumulator. The volume of gas in the gas accumulator can be adjusted based on the pressure when the piston of the piston-type accumulator hits the piston stop device by setting the volume of gas using the point in time when it is supplied as a reference point. Therefore, gas pressure and oil amount can be controlled reliably. Of course, it is also possible to easily save energy by unloading the pump when the gas volume or gas pressure in the gas accumulator reaches a specified amount or pressure.

[Brief explanation of the drawing]

Figure 1 is a hydraulic circuit diagram showing an example of a conventional device;
FIG. 2 is a hydraulic circuit diagram showing one embodiment of the present invention. 1... Pump, 3... Injection cylinder, 4, 23
...Switching valve, 5...Piston type accumulator,
5a...Piston, 6...Gas accumulator,
7... Valve, 12-16... Open/close valve, 19... Piston stop device, 20... Position control device, 21...
Pressure detector, 22...control device.

Claims (1)

[Claims] 1.Equipped with an accumulator that is a combination of a piston-type accumulator and a gas accumulator, a piston stop device that can stop the piston is provided on the gas chamber side of the piston-type accumulator in a position adjustable manner, and the pressure of the gas in the gas accumulator is adjusted. Filling an accumulator, which is equipped with a pressure sensing device for detecting pressure, and a control device capable of controlling the operating position of the piston stop device based on an output signal from the pressure sensing device when the piston of the piston-type accumulator hits the piston stop device. Control device.