JPH07186152A - Hydraulic apparatus in molding machine - Google Patents

Abstract

PURPOSE:To improve the general oil feeding efficiency and starting-up characteristics of an oil feeding pump while influence of the flow path resistance in a feeding path for a hydraulic oil is suppressed as low as possible. CONSTITUTION:A hydraulic oil tank 3 wherein a hydraulic oil is stored is constituted of a closed tank 6 for feeding the hydraulic oil to an oil feeding pump 4 and a tank 7 opened to the atmosphere for feeding the hydraulic oil to this closed tank and recovering the returned oil from a hydraulic actuator 2 and the hydraulic oil tank has a dwelling structure by means of which the hydraulic oil pressure in the closed tank is kept above atmospheric pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic system of a molding machine, and more particularly, it is provided with a large number of hydraulic actuators or a hydraulic oil supply path connecting these hydraulic actuators and a hydraulic oil tank is set long. The present invention relates to a hydraulic device preferably used in a molding machine.

[0002]

2. Description of the Related Art Conventionally, in a molding machine such as an injection molding machine, various hydraulic actuators have been used in order to perform various operations such as mold clamping, mold opening, and resin metering and injection. In addition, a hydraulic device for supplying hydraulic oil to these hydraulic actuators is provided to operate these hydraulic actuators. In this hydraulic system, the hydraulic oil stored in the hydraulic oil tank is sucked by one or a plurality of oil supply pumps and pressurized to a predetermined pressure, and then supplied to the plurality of hydraulic actuators. Further, the hydraulic oil discharged from the hydraulic actuator is collected in the hydraulic oil tank.

In such a hydraulic system, when the oil supply pump sucks the hydraulic oil from the hydraulic oil tank, the resistance of the oil supply pipe connecting the hydraulic oil tank and the oil supply pump is the resistance of the suction force of the pump. This acts to impose a heavy burden on the suction capacity of the oil supply pump, and in particular, causes a decrease in the response characteristic when the oil supply pump rises.

When the molding machine becomes large, the hydraulic oil tank and the oil supply pump are often installed separately from each other.
Along with this, not only the oil supply pipe becomes longer, but also the piping route tends to be complicated and the number of bent portions tends to increase, which may further promote the above-mentioned problems.

Therefore, in the past, there has been a method of increasing the diameter of the oil supply pipe to reduce the line resistance, for example, Japanese Patent Laid-Open No.
As shown in Japanese Patent No. 253996, the hydraulic oil tank is designed to discharge the internal air to the outside when the pressure in the hydraulic oil tank rises, and suck the air into the internal when the pressure inside the hydraulic oil tank decreases. With such a configuration, measures have been proposed to reduce the pressure fluctuation range in the hydraulic oil tank and reduce the load on the oil supply pump.

[0006]

However, even in such a coping method, the following problems still remain. That is, with the former method, the amount of hydraulic oil per unit cross-sectional area increases as the diameter of the oil supply pipe increases, so the inertial mass increases and the movement of hydraulic oil slows down. There is a problem that it is not enough to improve the responsiveness of the pump. Further, in the latter method, the pressure in the hydraulic oil tank may be maintained in a positive pressure state depending on the situation, but in the line for returning the hydraulic oil to this hydraulic oil tank, for example, There are lines, such as the drain line of the oil supply pump, which do not want back pressure to be applied to the returned hydraulic oil, and when such a line is connected to a hydraulic oil tank in a positive pressure state, the system for the entire hydraulic system There is a problem that efficiency improvement is limited.

The present invention has been made in view of the above-mentioned conventional problems, and improves the overall system efficiency while suppressing the influence of the flow path resistance in the hydraulic oil supply path as much as possible, and the refueling pump. It is an object of the present invention to provide a hydraulic device capable of improving the rising characteristics of the.

[0008]

In order to achieve the above-mentioned object, a hydraulic system in a molding machine according to claim 1 of the present invention is an oil supply pump for supplying hydraulic oil to a hydraulic actuator provided in the molding machine. And a hydraulic oil tank in a molding machine, the hydraulic oil tank communicating with the oil pump and storing the hydraulic oil, wherein the hydraulic tank is a closed tank for supplying hydraulic oil to the oil pump. When,
While being supplied with hydraulic oil to the closed tank, it is constituted by an atmosphere open tank in which return oil from the hydraulic actuator is collected, and the hydraulic oil tank is
It is characterized in that it has a pressure-holding structure for holding the hydraulic oil pressure in the closed tank above atmospheric pressure.

Further, in the hydraulic apparatus of the molding machine according to claim 2, the pressure maintaining structure according to claim 1 applies the hydraulic oil supplied to the closed tank between the closed tank and the atmosphere open tank. It is characterized by being provided with a pressure-holding pump for pressing.

According to a third aspect of the present invention, there is provided the hydraulic system for a molding machine according to the first aspect, wherein the pressure-holding structure is formed by arranging the atmosphere release tank above a closed tank. Characterize.

[0011]

According to the hydraulic system of the molding machine of claim 1, the hydraulic oil tank has a pressure-holding structure so that the hydraulic oil pressure in the closed tank constituting the hydraulic oil tank is maintained at atmospheric pressure or higher. As a result, positive pressure hydraulic oil is supplied from the closed tank to the oil supply pump, and the influence of the flow path resistance in the oil supply pipe connecting the closed tank and the oil supply pump on the oil supply pump is suppressed. In addition, the hydraulic oil discharged from the hydraulic actuator or oil pump is
By being collected by the atmosphere open tank, back pressure is prevented from acting on these hydraulic oils. As a result, the hydraulic oil is smoothly supplied to and discharged from the oil supply pump, and its rising characteristic is improved.

Further, according to the hydraulic device of the molding machine of the second aspect, the working oil stored in the atmosphere open tank is supplied to the closed tank while being pressurized by the pressure holding pump and temporarily stored therein. After that, the oil is supplied from the closed tank to the fuel pump. Since the pressure of the hydraulic oil supplied to the closed tank and the oil supply pump is set by the pressure holding pump, a stable hydraulic oil pressure can be obtained and a hydraulic oil pressure suitable for the oil supply pump can be easily obtained. To be

Further, according to the hydraulic apparatus of the molding machine of the third aspect, since the atmosphere open tank is arranged above the closed tank, the pressure corresponding to the difference in height is actuated in the closed tank. Given to the oil, the hydraulic oil is supplied to the oil supply pump under this pressure.

[0014]

EXAMPLE Next, an example of the present invention will be described with reference to FIG. Reference numeral 1 in FIG. 1 denotes a molding machine to which the present embodiment is applied. The molding machine 1 includes a hydraulic actuator 2 and a hydraulic oil tank 3 in which hydraulic oil for operating the hydraulic actuator 2 is stored. An oil supply pump 4 that sucks and pressurizes the hydraulic oil from the hydraulic oil tank 3 and supplies it to the hydraulic actuator 2, and controls the flow of the hydraulic oil supplied from the oil supply pump 4 to the hydraulic actuator 2. Flow path switching valve 5 to supply
It has a schematic configuration including and.

Explaining these details, the working oil tank 3 is communicated with the refueling pump 4 via a refueling pipe T, and the working oil is stored in a sealed state separated from the atmosphere. A tank 6, an air open tank 7 that is connected to the closed tank 6 via an oil supply pipe T, and stores the working oil in an open state to the atmosphere, and a communication between the closed tank 6 and the air open tank 7. And a holding pump 8 for pressurizing the working oil supplied from the atmosphere open tank 7 to the closed tank 6, and an upstream side of the holding pump 8 for cooling the working oil. Cooler 9 and the closed tank 6
A bypass pipe 10 for communicating the air release tank 7 with
The closed tank 6 is attached to the bypass pipe 10.
When the pressure exceeds a predetermined pressure, the relief valve 11 discharges the hydraulic oil in the closed tank 6 to the atmosphere open tank 7 and holds the pressure in the closed tank 6 at a set value. In the example, the pressure-holding structure is provided by providing the pressure-holding pump 8, and
The refueling pump 4, the closed tank 6, the atmosphere open tank 7,
Pressure-holding pump 8, cooler 9, bypass pipe 10, and
The relief valve 11 and the relief valve 11 constitute a hydraulic device O of this embodiment.

Further, an oil discharge pipe U for returning the hydraulic oil discharged from the hydraulic actuator 2 via the flow path switching valve 5 is inserted into the atmosphere open tank 7, and the oil supply pump 4 is connected to the oil discharge pump 4. The connected drain pipe D is inserted.

The hydraulic system O of the present embodiment constructed as described above is initially in an initial state by filling the hydraulic actuator 2, the flow path switching valve 5 and the hydraulic path of the hydraulic system O with hydraulic oil. Is made.

Then, by operating the pressure-holding pump 8,
By sending the hydraulic oil stored in the atmosphere open tank 7 to the closed tank 6 while pressurizing it, the closed tank 6
Increase the hydraulic oil pressure inside. At this time, the closed tank 6
When the working oil pressure inside reaches the relief pressure set in the relief valve 11 attached to the bypass pipe 10, the working oil inside the sealed tank 6 passes through the bypass pipe 10 to the atmosphere open tank 7 It is maintained at a constant pressure by being discharged to.

In this state, when the oil supply pump 4 is operated to operate the hydraulic actuator 2,
The hydraulic oil in the closed tank 6 is sucked by the oil supply pump 4, is pressurized to a predetermined pressure, and is supplied to the hydraulic actuator 2 via the flow path switching valve 5, so that the hydraulic actuator 2 flows. It is operated based on the supply form of hydraulic oil set by the path switching valve 5.

In the process of supplying the hydraulic oil by the oil pump 4, the hydraulic oil sucked by the oil pump 4 is boosted to a predetermined pressure by the pressure holding pump 8 as described above. The hydraulic oil of a predetermined pressure is constantly applied to the suction portion of the oil supply pump 4, and this suppresses an increase in negative pressure in the suction portion of the oil supply pump 4 when the oil supply pump 4 shifts to the suction operation. It
Further, since the hydraulic oil is poured into the oil supply pipe T that connects the closed tank 6 and the oil supply pump 4 so as to be pushed by the pressure given by the pressure holding pump 8, the resistance at the time of suction by the oil supply pump 4 is increased. Therefore, the flow path resistance in the oil supply pipe T is reduced. Therefore, due to these synergistic effects, the hydraulic oil is smoothly sucked into the oil supply pump 4, good start-up characteristics are obtained, and the hydraulic oil is smoothly supplied to the hydraulic actuator 2.

In addition, the hydraulic oil of a constant pressure is sealed in the tank 6.
Since the sufficient amount is stored in the inside, the pressure fluctuation of the hydraulic oil is suppressed even during the supply of the hydraulic oil by the oil supply pump 4, and from this point as well, the supply of the hydraulic oil to the oil supply pump 4 is stable. Performed, and by extension the hydraulic actuator 2
The hydraulic oil is stably supplied to. Further, since the drain pipe D that prevents back pressure is inserted into the atmosphere open tank 7, it is possible to prevent the back pressure from acting on the drain pipe D, and the back pump acts on the drain pipe D by the back pressure. The reduction in efficiency of No. 4 is suppressed.

The shapes, dimensions, etc. of the respective constituent members shown in the above embodiment are merely examples, and can be variously changed based on design requirements and the like.

For example, in the above embodiment, the closed tank 6
It is also possible to use a check valve instead of the relief valve 11 provided to keep the hydraulic oil pressure therein constant.

Further, in the above-mentioned embodiment, a pressure-holding pump 8 is provided as a pressure-holding structure between the atmosphere open tank 7 and the closed tank 6 to pressurize the hydraulic oil in the atmosphere open tank 7 and supply it to the closed tank 6. However, instead of this, as shown in FIG. 2, the atmosphere open tank 7 is installed above the closed tank 6 to correspond to the head of these height differences. It is also possible to adopt a configuration in which the pressure obtained by adding the pressure and the atmospheric pressure is applied to the hydraulic oil in the closed tank 6. With such a configuration, the pressure holding structure can be simplified by omitting the mechanical portion.

Further, in the above-mentioned embodiment, an example in which an air region is present in the closed tank 6 has been described, but it is also possible to fill all the inside with hydraulic oil.
It is possible to prevent the deterioration of the hydraulic oil by filling an inert gas in place of air in the air region.

[0026]

As described above, according to the first aspect of the present invention.
The hydraulic device in the molding machine described in (1) includes an oil supply pump that supplies hydraulic oil to a hydraulic actuator provided in the molding machine, and a hydraulic oil tank that is in communication with the oil supply pump and stores the hydraulic oil. A hydraulic device in a molding machine, wherein the hydraulic oil tank supplies a closed tank for supplying the hydraulic oil to the oil supply pump, and the hydraulic oil is supplied to the closed tank, and return oil from the hydraulic actuator is recovered. It is composed of an atmosphere open tank and
In addition, this hydraulic oil tank is characterized by having a pressure-holding structure for holding the hydraulic oil pressure in the closed tank above the atmospheric pressure, and has the following excellent effects.

Since the hydraulic oil tank has a pressure-holding structure, the hydraulic oil pressure in the closed tank for supplying the hydraulic oil to the oil supply pump is maintained above the atmospheric pressure, whereby the suction portion of the oil supply pump is always kept at the atmospheric pressure. By supplying the above-mentioned hydraulic oil, the hydraulic oil can be immediately sucked when the oil pump is started. Further, by supplying the hydraulic oil by overcoming the flow path resistance of the oil supply pipe for supplying the hydraulic oil from the closed tank to the oil supply pump, it is possible to prevent the flow path resistance from adversely affecting the oil supply pump. As a result, not only the startup characteristics of the oil supply pump can be made good, but also the supply of hydraulic oil to the hydraulic actuator can be made smooth. Furthermore, by providing an atmosphere release tank, by connecting an oil discharge route that prevents back pressure to this atmosphere release tank, it is possible to suppress the back pressure from acting on the oil discharge and to improve the system efficiency of the entire hydraulic system. Can be improved. Further, by storing a sufficient amount of the pressurized hydraulic oil in the closed tank, the pressure fluctuation of the hydraulic oil supplied to the oil supply pump is suppressed, and from this point also, the reduction of the system efficiency of the oil supply pump is suppressed. be able to.

Further, in the hydraulic device of the molding machine according to claim 2, the pressure maintaining structure according to claim 1 pressurizes the hydraulic oil supplied to the closed tank between the closed tank and the atmosphere open tank. It is characterized by being provided with a pressure-holding pump. With the pressure-holding pump, it is possible to reliably increase the pressure of the hydraulic oil in the closed tank and to obtain a stable pressure state. You can

Further, in the hydraulic device in the molding machine according to claim 3, the pressure-holding structure according to claim 1 is characterized in that the atmosphere opening tank is arranged above a closed tank. However, since the pressure-holding structure is composed only of the positional relationship between the two tanks, the structure is greatly simplified.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing another embodiment of the present invention.

[Explanation of symbols]

 1 Molding Machine 2 Hydraulic Actuator 3 Hydraulic Oil Tank 4 Oil Pump 6 Sealed Tank 7 Atmosphere Open Tank 8 Pressure Holding Pump 10 Bypass Pipe 11 Relief Valve

Claims (3)

[Claims] 1. A hydraulic system in a molding machine comprising an oil supply pump for supplying hydraulic oil to a hydraulic actuator provided in the molding machine, and a hydraulic oil tank communicating with the oil supply pump and storing the hydraulic oil. The hydraulic oil tank is a closed tank for supplying hydraulic oil to the oil supply pump, and an atmosphere open tank for supplying hydraulic oil to the closed tank and collecting return oil from the hydraulic actuator. A hydraulic device in a molding machine, wherein the hydraulic oil tank is configured to have a pressure holding structure for holding the hydraulic oil pressure in the closed tank at atmospheric pressure or higher. 2. The pressure-holding structure is configured such that a pressure-holding pump that pressurizes hydraulic oil supplied to the closed tank is provided between the closed tank and the atmosphere open tank. The hydraulic device in the molding machine according to claim 1. 3. The hydraulic device for a molding machine according to claim 1, wherein the pressure maintaining structure is configured by disposing the atmosphere opening tank above a closed tank.