JPH09117947A - Oil hydraulic circuit of injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of the surging and shock sound in a sub-oil hydraulic circuit by eliminating the shock phenomenon of the sub-oil hydraulic circuit without generating trouble in the control of the pressure of the vent circuit of the fixing emitting pump for an accelerating sub-oil hydraulic circuit. SOLUTION: In the oil hydraulic circuit of an injection molding machine together provided with the main oil hydraulic circuit 51 to an injection cylinder 1 and a sub-oil hydraulic circuit 52 having a fixed emitting flow rate sub-pump 11, a cushion valve having shock relaxing function is provided to an unload line 103 connecting the vent circuit 53 of the unloading relief valve 9 of the sub-oil hydraulic circuit 52 and a changeover valve 21 changing over the loading and unloading of the sub-pump 11 to perform the cushioning action due to the cushion valve at a time of unloading without troubling pressure control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit applied to hydraulic pressure control of an injection molding machine.

[0002]

2. Description of the Related Art The injection process by an injection molding machine is divided into a resin filling process and a pressure-holding process. In the filling process, the filling speed is controlled, and when the filling pressure exceeds a filling pressure set value, pressure control is performed. I do. In the pressure holding step, pressure control is performed.

FIG. 3 shows a hydraulic circuit configuration proposed in Japanese Utility Model Laid-Open No. 4-54828 in the injection process of the above-mentioned injection molding machine. FIG. 4 shows examples of changes in the filling pressure, the holding pressure, the holding pressure setting, the execution speed, and the execution pressure.

3 and 4, the pressure command value P is applied from the control position 4 to the proportional electromagnetic relief valve 6 at the same time when the filling is started.
1 is given, and the flow rate command value which becomes the set speed V1 is given to the flow rate valve 5. The flow valve 5 in which the oil from the variable discharge pump 7 is opened to the flow rate at which the injection set speed V1 is achieved as described above.
And is supplied to the injection cylinder 1. The injection ram 2 of the injection cylinder 1 starts moving from the position S1 at the speed of V1 and continues this state until the switching position S2. The position of the injection ram 2 is measured by the injection ram sensor 3 and compared with the switching position S2 by the control device 4.

When the measured value of the position sensor 3 becomes equal to the switching position S2 as a result of the comparison, the control device 4 changes the flow rate command value so that the speed of the injection ram 2 becomes V2.
Since 2 is insufficient in the discharge capacity of the variable discharge pump 7 (regulated by the flow valve 5), the solenoid a of the direction switching valve 10 is excited to operate the fixed discharge pump 11, and the oil from the fixed discharge pump 11 is activated. Is supplied to the injection cylinder 1 through the check valve 12, and at the same time, the specified value of the flow rate which becomes insufficient due to the capacity of the fixed discharge pump 11 is given to the flow rate valve 5 with respect to the speed V2, and the discharge oil of the variable discharge pump 7 flows It is supplied to the injection cylinder 1 through the valve 5.

The variable discharge pump 7 and the fixed discharge pump 1
Due to the combined flow rate with 1, the injection ram 2 begins to move at a velocity of V2. At this time, the load pressure becomes high and the discharge pressure of the variable discharge pump 7 whose discharge pressure is controlled by the proportional electromagnetic relief valve 6 decreases at the portion 121 where the execution pressure has reached the set pressure P1. Pump 1
The excess oil at the discharge flow rate of 1 is released to the tank from the relief valve 9 whose control pressure is remotely controlled by the proportional electromagnetic relief valve 6 by providing the connection circuit 101, and the variable discharge pump 7 and the fixed discharge pump 11 are provided. Both discharge pressures are controlled to the set pressure P1.

Continuing the above state, when the position of the injection ram 2 reaches the switching position S3, the solenoid a of the directional control valve 10 is excited so that the speed of the injection ram 2 becomes V3, whereby the flow valve 5 is supplied. The flow rate command value is changed, and the injection ram 2 moves to the switching position S4 at the speed of V3. Further, from this position S4, the pressure command value P2 is given to the proportional electromagnetic relief valve 6, and the upper limit of the pressure applied to the injection cylinder 1 is
The filling pressure P1 is changed to the holding pressure P2. Further, the solenoid a of the directional control valve 10 is excited so as to attain the set speed V4, the fixed discharge pump 11 is remotely controlled and loaded with the control pressure P2 of the proportional electromagnetic relief valve 6, and the flow rate command value of the insufficient flow rate with respect to V4 is set to the flow rate. Give to valve 5.

However, in the pressure holding step, since the injection ram 2 is almost completely pressed down, the speed of the injection ram 2 is almost zero, the load pressure becomes high, and the execution pressure is set to P2.
In the portion 122 which has reached the point, similarly to the portion 121 described above, the discharge pressures of the variable discharge pump 7 and the fixed discharge pump 11 are both controlled to the control pressure P2 of the proportional electromagnetic relief valve 6, and the injection cylinder 1 is discharged. The pressure is controlled to P2. At the same time as switching to S4, this state continues until T1 when the holding pressure completion timer 8 which starts driving times out.

[0009]

As described above, the main pump (variable discharge pump) is used for pressure control in the injection holding pressure.
If the set pressure of the load valve of the booster pump (fixed discharge pump) is high when the proportional pressure valve is used, the holding pressure is not controlled when the driver sets the flow rate at which the booster pump starts. It will be possible. As a countermeasure against this, as described above, the vent line of the load valve of the speed increasing pump may be connected to the proportional control line of the main hydraulic circuit so that the pressure of the speed increasing pump becomes the same as that of the hydraulic circuit. When the load valve (relief valve) of the pump is unloaded, the pressure in the vent line is quickly released, so that a shock noise (surge pressure) occurs.

In order to prevent this, it is conceivable to insert a shockless valve into this circuit, but if this shockless valve is provided in series in the vent line, the oil flow in the shockless valve is one-way, so This cannot be used because the pressure remote control of the booster pump hydraulic circuit cannot be performed.

An object of the present invention is to eliminate the shock phenomenon of the sub hydraulic circuit without disturbing the pressure control of the vent circuit of the fixed discharge pump for the sub hydraulic circuit for speed-up, and to prevent surging and shock noise in the sub hydraulic circuit. It is to prevent the occurrence.

[0012]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and a first means thereof is to provide a main hydraulic circuit to an injection cylinder and a sub hydraulic circuit having a fixed discharge flow sub-pump. In the hydraulic circuit of the injection molding machine installed side by side, a buffer having a shock absorbing function in the unload line that connects the vent circuit of the relief valve for unloading the sub hydraulic circuit and the switching valve that switches between loading and unloading of the sub pump It is in a hydraulic circuit of an injection molding machine, which is provided with a valve.

Further, the main hydraulic circuit is provided with a variable discharge flow rate main pump, and the pressure control pilot line of the main hydraulic circuit and the vent circuit of the relief valve for unloading the hydraulic circuit of the sub pump are connected to the load of the sub pump. , A unidirectional valve for buffering is provided in the unload line of the relief valve, which is a second means of the present invention.

Further, a fixed discharge flow main pump provided with a proportional flow control valve and a proportional electromagnetic relief valve is attached to the main hydraulic circuit, and the pressure line of the main hydraulic circuit and the hydraulic circuit of the fixed discharge sub pump are unloaded. The vent circuit of the relief valve for use is connected via a switching valve that switches between loading and unloading of the sub-pump, and a unidirectional valve for buffering is provided in the unload line of the relief valve. Is a means to do.

According to the above-mentioned first means, when the fixed discharge flow rate sub-pump is loaded, normal pressure control is performed, and when the sub-pump is unloaded, the shock phenomenon of the sub-hydraulic circuit is caused by the buffering action of the buffer valve provided in the unload line. Is avoided, which prevents the generation of surging and shock noise.

Further, a second, which embodies the first means,
According to the third means, the pressure control line of the main hydraulic circuit and the vent circuit of the relief valve for unloading the hydraulic circuit of the fixed discharge flow sub-pump are connected via a switching valve that switches between loading and unloading of the sub-pump. By
It is possible to control the discharge pressure of the sub pump so that the pressure of the sub hydraulic circuit becomes equal to the pressure of the main hydraulic circuit when the sub pump is loaded. Therefore, even if the sub-pump is loaded and the pressure-holding step is started, the control of the pressure does not collapse, and the pressure is controlled to be equal to the discharge pressure of the main pump.

When the hydraulic circuit of the sub-pump is switched to unloading by the switching valve, the vent circuit of the unloading relief valve of the main hydraulic circuit and the sub-hydraulic circuit is cut off to switch to unloading and unloading. Pressure is slowly released through a one-way valve having the same shockless function as the pressure reducing valve provided between the vent port of the relief valve and the oil tank. Therefore, shock noise is reduced without causing surging in the tank line of the relief valve when the sub-pump is unloaded.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a configuration diagram of a hydraulic circuit of an injection molding machine including a variable displacement pump and a fixed discharge flow rate sub-pump according to an embodiment of the present invention.

In FIG. 1, 1 is an injection cylinder, 2 is an injection ram fitted in the cylinder, 3 is a position sensor for detecting the position of the injection ram 2, and 4 is a control device for controlling the pressure and flow rate of each circuit. Reference numeral 5 is a flow valve, 6 is a proportional control type relief valve, 7 is a variable discharge flow main pump, 11 is a fixed discharge flow sub-pump, and 9 is a sub hydraulic circuit 52 which is a discharge passage of the fixed discharge flow sub pump 11. A relief valve for adjusting the pressure of the sub-hydraulic circuit, 12 is a check valve, and 15 is a load reaction circuit. The above configuration is similar to the conventional configuration shown in FIG.

In the embodiment shown in FIG. 1, the pressure control circuit of the fixed discharge flow rate sub-pump 11 includes a pressure control pilot line 54 of the load sensitive circuit 15 of the main hydraulic circuit 51 of the variable discharge flow rate main pump 7, The vent circuit of the relief valve 9 for unloading the sub-hydraulic circuit 52 of the fixed discharge flow sub-pump 11 is connected by the connection circuit 102 via the switching valve 21 that switches between loading and unloading of the fixed discharge flow sub-pump 11. ,
The unload line 103 of the relief valve 9 is provided with a one-way valve 22 having a shockless function (shock absorbing function).

In the hydraulic circuit of the injection molding machine configured as described above, the operation during the injection process is the same as that shown in FIG.

Referring to FIG. 1, the hydraulic circuit according to this embodiment includes a pressure control pilot line 54 of the main hydraulic circuit 51 and a vent circuit 53 of the relief valve 9 for unloading the sub hydraulic circuit 52 of the fixed discharge flow sub-pump 11. Are connected via a switching valve 21 for switching between loading and unloading of the fixed discharge flow rate sub-pump 11, whereby the control device 4 performs the following control operation. When the fixed discharge flow rate sub-pump 11 is loaded (from S2 to S4 in FIG.
In the range of T1), the pressure of this hydraulic circuit is transmitted to the vent circuit 53 via the load line 105, and the discharge pressure of the fixed discharge flow sub-pump 11 can be controlled to be equal to the pressure of the main hydraulic circuit. Therefore, even if the fixed discharge flow sub-pump 11 is loaded and the holding pressure process is started, the pressure of the injection cylinder 1 is controlled by the control pressure P of the proportional electromagnetic relief valve 6.
2 is controlled.

When the switching valve 21 switches the sub-hydraulic circuit of the fixed discharge flow sub-pump 11 to unloading (position S4 or T1 in FIG. 4), the connecting circuit 102 for connecting the main hydraulic circuit 51 and the sub-hydraulic circuit 52. And the load line 105 are disconnected, the unload line 103 is connected to the tank, and the vent pressure of the relief valve 9 is moderated via the one-way valve 22 having a shockless function provided in the unload line 103. Exit to. Therefore, when the fixed discharge sub pump 11 is unloaded, surging does not occur in the tank line of the relief valve,
Shock noise can be reduced.

In FIG. 2, a fixed discharge flow main pump 20 having a proportional flow control valve 23 and a proportional electromagnetic relief valve 6 according to a second embodiment of the present invention, and an injection molding provided with a fixed discharge flow sub-pump 11. The hydraulic circuit of the machine is shown.
In this hydraulic circuit, the fixed discharge flow main pump 2
The pressure line of the hydraulic circuit 61 of 0 and the vent circuit of the relief valve 9 for unloading the hydraulic circuit of the fixed discharge flow sub-pump 11,
Connection circuit 10 via switching valve 21 for switching unloading
4 is connected (connection circuit 104), and the unload line 103 is provided with a one-way valve 22 having a shockless function.

In this embodiment, similarly to the variable discharge flow pump 7 in the first embodiment, the pressure control line of the hydraulic circuit 61 of the fixed discharge flow main pump 20 and the sub hydraulic circuit 52 of the fixed discharge flow sub-pump 11 are turned off. Switching valve 21 for switching the loading / unloading of the fixed discharge flow sub-pump 11 with the vent circuit of the relief valve 9 for loading
Since it is connected via a fixed discharge sub-pump 1
It is possible to control the pressure of the hydraulic circuit 52 to be equal to the pressure of the fixed discharge flow rate main hydraulic circuit when loading 1. Therefore, the pressure of the injection cylinder 1 is controlled to the control pressure of the proportional electromagnetic relief valve 6 even if the pressure maintaining process is started while the fixed discharge flow sub-pump 11 is loaded.

When the switching valve 21 switches the hydraulic circuit 52 of the fixed discharge flow sub-pump 11 to unloading (position S4 or T1 in FIG. 4), the connecting circuit 104 for connecting the main hydraulic circuit and the sub-hydraulic circuit described above. The load line 105 and the unload line 103.
Is connected to the tank, and the vent pressure of the relief valve 9 is gently released via the one-way valve 22 provided in the unload line 103 and having a shockless function. Therefore, shock noise can be reduced without causing surging in the tank line of the relief valve when the fixed discharge flow sub-pump 11 is unloaded.

[0027]

The present invention is configured as described above.
According to the first aspect of the present invention, the normal pressure control can be performed when the fixed discharge flow rate sub-pump is loaded, and the buffering valve provided in the unload line can perform the buffering action when the sub-pump is unloaded. As a result, the occurrence of a shock phenomenon in the sub-hydraulic circuit can be avoided and the occurrence of surging and shock noise can be prevented without affecting the pressure control of the sub-pump circuit.

Further, according to the second and third aspects of the invention, the vent circuit of the speed increasing pump is controlled so that the pressure of the fixed discharge flow sub-pump, which is the speed increasing pump, becomes the same as that of the main hydraulic circuit. When connecting to the line and unloading the relief valve of the speed-up pump by the switching valve, the switching valve cuts off the connection circuit between the main hydraulic circuit and the sub hydraulic circuit and switches to the unload line. The pressure is gradually released through the buffering one-way valve, so that surging can be avoided and shock noise can be reduced. Therefore, according to the above configuration, it is possible to prevent surging and shock noise without hindering the pressure control of the speed increasing pump circuit, that is, the discharge circuit of the fixed discharge flow rate sub-pump.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of an injection molding machine provided with a variable discharge flow rate main pump and a fixed discharge flow rate sub-pump according to a first embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram of an injection molding machine provided with a fixed discharge flow main pump and a fixed discharge flow sub-pump equipped with a proportional flow rate control valve and a proportional electromagnetic relief valve according to a second embodiment of the present invention.

FIG. 3 is a hydraulic circuit diagram of a conventional injection molding machine.

FIG. 4 is a diagram showing the relationship between the switching position and the filling speed and pressure in the case of FIG.

[Explanation of symbols]

 1 Injection Cylinder 2 Injection Ram 3 Injection Ram Position Sensor 4 Control Device 5 Flow Valve 6 Proportional Electromagnetic Relief Valve 7 Variable Discharge Flow Main Pump 9 Relief Valve 11 Fixed Discharge Flow Sub Pump 15 Load Sensitive Circuit 20 Fixed Discharge Flow Main Pump 21 Switching Valve 22 1-way valve 23 Flow control valve 51 Main hydraulic circuit 52 Sub hydraulic circuit 53 Vent circuit 54 Pressure control pilot line 102 Connection circuit 103 Unload line 104 Connection circuit 105 Load line

Claims (3)

[Claims] 1. A hydraulic circuit of an injection molding machine in which a main hydraulic circuit to an injection cylinder and a sub hydraulic circuit having a fixed discharge sub pump are provided side by side, and a vent circuit of a relief valve for unloading the sub hydraulic circuit and the above A hydraulic circuit for an injection molding machine, wherein a buffer valve having a shock absorbing function is provided in an unload line that connects a switching valve for switching between loading and unloading of a sub pump. 2. In a hydraulic circuit of an injection molding machine provided with a variable discharge flow main pump and a fixed discharge flow sub-pump, a pressure control pilot line of a main hydraulic circuit of the variable discharge flow main pump and a hydraulic pressure of the fixed discharge flow sub-pump. The vent circuit of the relief valve for unloading the circuit is connected via a switching valve that switches between loading and unloading of the sub-pump, and a one-way valve having a shock absorbing function is provided in the unload line of the relief valve. The hydraulic circuit of the injection molding machine characterized by the above. 3. In a hydraulic circuit of an injection molding machine equipped with a fixed discharge flow main pump provided with a proportional flow control valve and a proportional electromagnetic relief valve, and a fixed discharge flow sub-pump, the pressure line of the main hydraulic circuit and the fixed line. One-way connection with the vent circuit of the relief valve for unloading the hydraulic circuit of the discharge flow rate sub-pump through a switching valve that switches between loading and unloading of the sub-pump, and the impact easing function in the unload line of the relief valve. A hydraulic circuit for an injection molding machine, which is provided with a valve.