JP3611260B2 - Hydraulic circuit of injection molding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic circuit applied to hydraulic pressure control of an injection molding machine.
[0002]
[Prior art]
The injection process by the 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 the filling pressure set value, the pressure is controlled. In the pressure holding step, pressure control is performed.
[0003]
FIG. 3 shows a hydraulic circuit configuration proposed in Japanese Utility Model Laid-Open No. 4-54828 as an injection process of the injection molding machine. FIG. 3 shows a filling speed, a speed switching position, and a filling pressure when the hydraulic circuit is operated. FIG. 4 shows examples of the setting of the holding pressure and the holding time, the execution speed, and the change of the execution pressure.
[0004]
3 and 4, the pressure command value P1 is supplied from the control equipment 4 simultaneously to the proportional electromagnetic relief valve 6 filling start and the flow rate command value becomes the set speed V1 is applied to the flow valve 5. The oil from the variable discharge pump 7 is supplied to the injection cylinder 1 through the flow rate valve 5 opened to the flow rate at the injection set speed V1 as described above. The injection ram 2 of the injection cylinder 1 starts to move 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 is compared with the switching position S2 by the control device 4.
[0005]
As a result of the comparison, when the measured value of the position sensor 3 becomes equal to the switching position S2, the control device 4 changes the flow rate command value so that the speed of the injection ram 2 becomes V2, but the V2 is the discharge capacity of the variable discharge pump 7. Is insufficient (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 passes through the check valve 12 to the injection cylinder 1. At the same time as the supply, the specified value of the flow rate that becomes insufficient with the capacity of the fixed discharge pump 11 with respect to the speed V2 is given to the flow valve 5, and the discharge oil of the variable discharge pump 7 passes through the flow valve 5 to the injection cylinder 1. Supplied.
[0006]
The injection ram 2 starts to move at a speed of V2 due to the combined flow rate of the variable discharge pump 7 and the fixed discharge pump 11. At this time, the load pressure increases, and at 121 portion where the effective pressure reaches the set pressure P1, the discharge flow rate of the variable discharge pump 7 whose discharge pressure is controlled by the proportional electromagnetic relief valve 6 decreases, and further, the fixed discharge. Excess oil in the discharge flow rate of the pump 11 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 discharge pressures are both controlled to the set pressure P1.
[0007]
When the above state is continued and the position of the injection ram 2 reaches the switching position S3, the solenoid a of the direction switching valve 10 is excited so that the speed of the injection ram 2 becomes V3. 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 changed from the filling pressure P1 to the holding pressure P2. Further, the solenoid a of the directional control valve 10 is excited so that the set speed V4 is obtained, and the fixed discharge pump 11 is loaded with the control pressure P2 of the proportional electromagnetic relief valve 6 by remote control. Give to valve 5.
[0008]
However, in the pressure holding step, since the injection ram 2 is almost fully pushed, the speed of the injection ram 2 is almost zero and the load pressure is high. Similarly to the above-mentioned part 121, 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 pressure of the injection cylinder 1 is controlled to P2. This state continues at the same time as switching to S4 until T1 when the holding pressure completion timer 8 that starts driving times out.
[0009]
[Problems to be solved by the invention]
When pressure control is performed by the proportional pressure valve of the main pump (variable discharge pump) in the injection holding pressure as described above, if the set pressure of the load valve of the speed increasing pump (fixed discharge pump) is high, the speed increasing pump When the driver sets the flow rate at which the engine starts, the holding pressure becomes uncontrollable. As described above, as described above, the vent line of the speed increasing pump load valve 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, which causes a problem that a shock noise (surge pressure) is generated.
[0010]
In order to prevent this, a shockless valve may be inserted in this circuit. However, if this shockless valve is provided in series in the vent line, the oil flow in the shockless valve is unidirectional, so the speed increasing pump This cannot be used because the remote pressure control of the hydraulic circuit becomes impossible.
[0011]
The object of the present invention is to eliminate the shock phenomenon of the sub-hydraulic circuit without impeding the pressure control of the vent circuit of the fixed discharge pump for the sub-hydraulic circuit for speed increase, and prevent the surging and the generation of shock noise in the sub-hydraulic circuit There is to do.
[0012]
[Means for Solving the Problems]
The present invention is intended to solve the above problems, first means of that, in the hydraulic circuit of an injection molding machine provided with a fixed discharge flow sub pump with variable discharge flow main pump, the variable discharge flow main pump Main a vent circuit of the relief valve for unloading pressure control pilot line and the hydraulic circuit of the fixed discharge flow rate sub pump of the hydraulic circuit, the connection circuit, the sub pump load, the load of the switching valve and the relief valve for switching the unloading connected via a line, and the unloading line of the relief valve is branched from the vent circuit is connected to said switching valve, provided a one-way valve with an impact relaxation function during unloading line of the relief valve The hydraulic circuit of the injection molding machine is characterized by that.
[0014]
The second means is a hydraulic circuit of an injection molding machine provided with a fixed discharge flow main pump and a fixed discharge flow sub pump provided with a proportional flow rate control valve and a proportional electromagnetic relief valve , and a pressure line of the main hydraulic circuit. And a relief valve vent circuit for unloading the hydraulic circuit of the fixed discharge flow rate sub-pump via a connection circuit, a switching valve for switching between loading and unloading of the sub- pump, and a load line of the relief valve , and the unloading line of the relief valve is branched from the vent circuit is connected to said switching valve, an injection molding machine, characterized in that a one-way valve having a shock-absorbing function during unloading line of the relief valve In the hydraulic circuit .
[0015]
According to the first, second means, performs normal pressure control at the time of loading of the fixed discharge flow sub pump, the hydraulic circuit of the sub-pump by an impact relaxation function of the one-way valve provided in the unloading line during unloading of the sub pump The occurrence of a shock phenomenon is avoided, thereby preventing the generation of surging and shock noise.
[0016]
In other words , a connection circuit, a switching valve for switching between loading and unloading of the sub pump, and a load line are connected to the pressure control pilot line or pressure line of the main hydraulic circuit and the vent circuit of the relief valve for unloading of the hydraulic circuit of the fixed discharge flow rate sub pump. by connecting via can perform the discharge pressure control of the sub pump to be equal to the pressure of the main hydraulic circuit the pressure of the hydraulic circuit of the sub-pump when loading the sub-pump. Therefore, even if the pressure holding process is started while the sub pump is loaded, the pressure control is not disrupted and is controlled to be equal to the discharge pressure of the main pump.
[0017]
Further, when the above switching valve hydraulic circuit sub pump is switched to unload, turned down vent circuit unloading relief valve of the hydraulic circuit of the main hydraulic circuit and a sub pump is switched to the unloading, the unloading The pressure is gradually released through a one-way valve having a shockless function having the same structure as that of the pressure reducing valve provided between the vent port of the relief valve and the oil tank. Therefore, the shock noise is reduced without causing surging in the unload line of the relief valve when the sub pump is unloaded .
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described 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.
[0019]
In FIG. 1, 1 is an injection cylinder, 2 is an injection ram fitted to the cylinder, 3 is a position sensor for detecting the position of the injection ram 2, 4 is a control device for controlling the pressure flow of each circuit, A flow control valve, 6 is a proportional control type relief valve, 7 is a variable discharge flow rate main pump, 11 is a fixed discharge flow rate sub pump, and 9 is a sub hydraulic circuit provided in a sub hydraulic circuit 52 which is a discharge path of the fixed discharge flow rate sub pump 11. A pressure adjusting relief valve, 12 is a check valve, and 15 is a load reaction circuit. The above configuration is the same as the conventional one shown in FIG.
[0020]
In the embodiment shown in FIG. 1, the pressure control circuit of the fixed discharge flow rate sub-pump 11 includes the pressure control pilot line 54 of the load sensing circuit 15 of the main hydraulic circuit 51 of the variable discharge flow rate main pump 7 and the fixed discharge flow rate. The vent circuit of the unloading relief valve 9 of the sub hydraulic circuit 52 of the flow rate sub-pump 11 is connected by the connection circuit 102 via the switching valve 21 for switching between loading and unloading of the fixed discharge flow rate sub-pump 11 and the relief described above. The one-way valve 22 having a shockless function (impact mitigation function) is provided in the unload line 103 of the valve 9.
[0021]
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.
[0022]
1, the hydraulic circuit according to this embodiment fixes the pressure control pilot line 54 of the main hydraulic circuit 51 and the vent circuit 53 of the unloading relief valve 9 of the sub hydraulic circuit 52 of the fixed discharge flow rate sub-pump 11. The discharge flow rate sub-pump 11 is connected via a switching valve 21 for switching between loading and unloading, whereby the control device 4 performs the following control operation. When the fixed discharge flow rate sub-pump 11 is loaded (in the range from S2 to S4 or T1 in FIG. 4), the pressure of this hydraulic circuit is transmitted to the vent circuit 53 via the load line 105 and is equal to the pressure of the main hydraulic circuit. The discharge pressure can be controlled. Accordingly, even when the pressure holding process is started with the fixed discharge flow rate sub-pump 11 loaded, the pressure of the injection cylinder 1 is controlled to the control pressure P2 of the proportional electromagnetic relief valve 6.
[0023]
When the switching valve 21 switches the sub hydraulic circuit of the fixed discharge flow rate sub pump 11 to unloading (position of S4 or T1 in FIG. 4), the connection circuit 102 and the load line of the main hydraulic circuit 51 and the sub hydraulic circuit 52 are connected. The unload line 103 is connected to the tank by disconnecting the connection to the tank 105, and the vent pressure of the relief valve 9 is gradually released through the one-way valve 22 provided in the unload line 103 and having a shockless function. Accordingly, shock noise can be reduced without causing surging in the tank line of the relief valve when the fixed discharge flow rate sub-pump 11 is unloaded.
[0024]
FIG. 2 shows the hydraulic pressure of an injection molding machine provided with a fixed discharge flow rate main valve 20 having a proportional flow rate control valve 23 and a proportional electromagnetic relief valve 6 and a fixed discharge flow rate sub pump 11 according to a second embodiment of the present invention. A circuit is shown. In this hydraulic circuit, the pressure line of the hydraulic circuit 61 of the fixed discharge flow rate main pump 20 and the vent circuit of the relief valve 9 for unloading the hydraulic circuit of the fixed discharge flow rate sub pump 11 are connected to the load of the fixed discharge flow rate sub pump 11. The unload line 103 is connected by a connection circuit 104 via a switching valve 21 (connection circuit 104), and the unload line 103 is provided with a one-way valve 22 having a shockless function.
[0025]
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 unloading of the sub hydraulic circuit 52 of the fixed discharge flow sub pump 11 are used. Since the vent circuit of the relief valve 9 is connected via a switching valve 21 for switching between loading and unloading of the fixed discharge flow rate sub-pump 11, the pressure of the hydraulic circuit 52 is fixed to the fixed discharge flow rate when the fixed discharge flow rate sub-pump 11 is loaded. It can be controlled to be equal to the pressure of the main hydraulic circuit. Therefore, even when the pressure holding process is started with the fixed discharge flow rate sub-pump 11 loaded, the pressure of the injection cylinder 1 is controlled to the control pressure of the proportional electromagnetic relief valve 6.
[0026]
Further, when the switching valve 21 switches the hydraulic circuit 52 of the fixed discharge flow rate sub-pump 11 to unload (position of S4 or T1 in FIG. 4), the connection circuit 104 and the load line of the main hydraulic circuit and the sub hydraulic circuit described above. The unload line 103 is disconnected from the tank, the unload line 103 is connected to the tank, and the vent pressure of the relief valve 9 is gradually released through the one-way valve 22 provided in the unload line 103 and having a shockless function. Accordingly, shock noise can be reduced without causing surging in the tank line of the relief valve when the fixed discharge flow rate sub-pump 11 is unloaded.
[0027]
【The invention's effect】
The present invention is configured as described above. According to the first and second aspects of the present invention, normal pressure control is performed when the fixed discharge flow rate sub-pump is loaded, and the buffer provided in the unload line is loaded when the sub-pump is unloaded. The buffering action of the valve can be made. As a result, the occurrence of a shock phenomenon in the sub hydraulic circuit can be avoided without disturbing the pressure control of the sub pump circuit, and the occurrence of surging and shock noise can be prevented.
[0028]
Furthermore, as the pressure of the fixed discharge flow sub pump is a speed-increasing pump is identical with the main hydraulic circuit to connect the vent circuit of the sub-pump to the pressure control pilot line or pressure line of the main hydraulic circuit, the switching valve when unloading relief valve of the sub-pump, it refused the connection circuit of the hydraulic circuit of the switching valve main hydraulic circuit and a sub pump, since switching to the unload line, the pressure of the hydraulic circuit of the sub-pump shock alleviating function Surging can be avoided and shock noise can be reduced by the gentle release of pressure through the one-way valve having the . Therefore, according to the above configuration, it is possible to realize the prevention of trouble without surging and a shock sound pressure and the ejection circuit of 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 rate main valve and a fixed discharge flow rate sub pump provided 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.
4 is a diagram showing the relationship between the switching position, the filling speed and the pressure in the case of FIG. 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Injection cylinder 2 Injection ram 3 Injection ram position sensor 4 Control apparatus 5 Flow valve 6 Proportional electromagnetic relief valve 7 Variable discharge flow main pump 9 Relief valve 11 Fixed discharge flow subpump 15 Load sensitive circuit 20 Fixed discharge flow main pump 21 Switching valve 22 One-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 (2)

In the hydraulic circuit of an injection molding machine provided with a variable discharge flow rate main pump and fixed discharge flow sub pump, unloading of the hydraulic circuit of the variable discharge flow rate main hydraulic circuit of the main pump pressure control pilot line and the fixed discharge flow rate sub pump The relief valve vent circuit is connected via a connection circuit, a switching valve for switching between loading and unloading of the sub- pump and a load line of the relief valve , and the relief valve is branched from the vent circuit. hydraulic circuit of an injection molding machine to load lines connected to said switching valve, characterized in that a one-way valve with an impact relaxation function during unloading line of the relief valve. In the hydraulic circuit of an injection molding machine provided with the proportional fixed discharge flow main pump flow rate control valve and the proportional electromagnetic relief valve is Fusetsu and fixed discharge flow sub pump, pressure Chikarara-in main hydraulic circuit and the fixed discharge flow rate A vent circuit of a relief valve for unloading the hydraulic circuit of the subpump is connected via a connection circuit, a switching valve for switching between loading and unloading of the subpump and a load line of the relief valve , and from the vent circuit A hydraulic circuit for an injection molding machine, wherein an unload line of the relief valve that branches is connected to the switching valve, and a one-way valve having an impact relaxation function is provided in the unload line of the relief valve.

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