Hydraulic circuit for controlling glue injection action of injection molding machine

Abstract

The utility model discloses a glue injection action control hydraulic loop of an injection molding machine, which comprises a six-position four-way servo valve and a glue injection oil cylinder, a port P of the six-position four-way servo valve is communicated with an oil inlet, a port T of the six-position four-way servo valve is communicated with an oil return port, a port A of the six-position four-way servo valve is communicated with a rear oil port of the glue injection oil cylinder, and a port B of the six-position four-way servo valve is communicated with an oil return port of the glue injection oil cylinder. A port B of the six-position four-way servo valve is communicated with a front oil port of a glue injection oil cylinder, a cartridge valve is arranged between a rear oil port of the glue injection oil cylinder and a port A of the six-position four-way servo valve, a control port of the cartridge valve is communicated with a direction valve, and when the six-position four-way servo valve stops working, the direction valve is controlled to be not electrified, and the direction valve is controlled to be not electrified. And hydraulic oil at a rear oil port in the glue injection oil cylinder is sealed by the cartridge valve and cannot flow to the six-position four-way servo valve, so that the screw rod is prevented from retreating due to leakage of a valve core, the screw rod connected with the conveying end of the glue injection oil cylinder is always kept at a charging ending position, the glue injection starting point positions of the next mold are ensured to be the same, and the influence on the product precision is avoided.

Description

Technical Field

[0001] This utility model relates to the field of injection molding machine technology, and in particular to a hydraulic circuit for controlling the injection action of an injection molding machine. Background Technology

[0002] With the booming development of domestic manufacturing, traditional processing industries are gradually being replaced by high-precision processing industries with higher requirements, such as electronics, information technology, and automobiles. Precision injection molding has become the mainstream of the injection molding market. As a result, the proportion of high-precision injection molding machines in the injection molding machine market is increasing year by year. To meet the requirements of high injection accuracy and high injection stability of precision injection molding machines, more and more injection molding machines are using high-response servo valves for injection action. Currently, most injection molding machine manufacturers use German Rexroth closed-loop pilot-operated high-frequency response WRL dedicated injection servo valves. This valve can control the injection and release speed, as well as the injection holding pressure and melt back pressure, according to different signals input by the controller. At the same time, it can adjust the valve core position according to the real-time speed and pressure values ​​to meet the requirements of the command signal. To achieve this requirement, the P port of the servo valve needs to maintain a certain pressure and flow rate. However, with the widespread application of servo oil pump motor systems, in order to achieve energy saving, the oil pump motor usually stops rotating almost completely during the cooling stage after feeding. At this time, the pressure at the P port of the servo valve is close to zero. Thus, during the cooling stage, the servo valve cannot automatically adjust and is usually in the zero position. However, in the zero position, there will be some leakage in the valve core. After feeding, due to the pressure of the molten rubber at the front end of the screw, it will push the screw to slowly retreat a certain distance until the back pressure disappears and approaches zero. The greater the back pressure during feeding, the farther the retreat distance, and the retreat distance varies at different times, especially in semi-automatic production. This causes the starting position of the next injection to be different, affecting the product accuracy. Utility Model Content

[0003] The purpose of this invention is to provide a hydraulic circuit for controlling the injection action of an injection molding machine, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, this utility model provides the following technical solution: a hydraulic circuit for controlling the injection action of an injection molding machine, comprising a six-position four-way servo valve and an injection cylinder. The P port of the six-position four-way servo valve is connected to the oil inlet, the T port of the six-position four-way servo valve is connected to the oil return port, the A port of the six-position four-way servo valve is connected to the rear oil port of the injection cylinder, the B port of the six-position four-way servo valve is connected to the front oil port of the injection cylinder, a cartridge valve is provided between the rear oil port of the injection cylinder and the A port of the six-position four-way servo valve, and a directional valve is connected to the control port of the cartridge valve.

[0005] Preferably, a pressure sensor is connected to one side of the A port of the six-position four-way servo valve.

[0006] Preferably, the cartridge valve is a directional valve assembly cartridge valve.

[0007] Preferably, the opening pressure of the cartridge valve is 2 bar.

[0008] Preferably, the directional valve is a two-position four-way directional valve, with its P port connected to the rear oil port of the injection cylinder, its A port connected to the control port of the cartridge valve, and its T port connected to the independent return oil port.

[0009] Preferably, a throttle is provided between the A port of the two-position four-way directional valve and the control port of the cartridge valve.

[0010] The beneficial effects of this utility model are as follows: When the six-position four-way servo valve stops working, the control directional valve is not energized, and the hydraulic oil in the rear port of the injection cylinder is sealed by the cartridge valve, preventing it from flowing to the six-position four-way servo valve. This avoids the screw retraction caused by leakage of the valve core of the six-position four-way servo valve, ensuring that the screw connected to the conveying end of the injection cylinder always remains in the feeding end position, ensuring that the injection start position of the next mold is the same, and avoiding any impact on product accuracy. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the hydraulic principle for servo injection motion control in an embodiment of this utility model.

[0012] In the diagram: 1. Six-position four-way servo valve; 2. Injection cylinder; 3. Cartridge valve; 4. Directional valve; 5. Pressure sensor; 6. Throttling element. Detailed Implementation

[0013] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0014] Please see Figure 1 This utility model provides a hydraulic circuit for controlling the injection action of an injection molding machine, including a six-position four-way servo valve 1 and an injection cylinder 2. The P port of the six-position four-way servo valve 1 is connected to the oil inlet, the T port of the six-position four-way servo valve 1 is connected to the oil return port, the A port of the six-position four-way servo valve 1 is connected to the rear oil port of the injection cylinder 2, the B port of the six-position four-way servo valve 1 is connected to the front oil port of the injection cylinder 2, a cartridge valve 3 is provided between the rear oil port of the injection cylinder 2 and the A port of the six-position four-way servo valve 1, and a directional valve 4 is connected to the control port of the cartridge valve 3.

[0015] Specifically, the hydraulic circuit is composed of components such as a six-position four-way servo valve 1, a pressure sensor 5, a cartridge valve 3, a directional valve 4, and an injection cylinder 2. When the injection molding machine enters the injection, pressure holding, release, and feeding actions, the six-position four-way servo valve 1 receives the instruction signal voltage value from the injection molding machine control computer. During injection, the six-position four-way servo valve 1 receives a voltage of 1.5V to 10V, and its valve core is at the rightmost end, with port P connecting to port A and port B connecting to port T, driving the injection cylinder piston to move to the left. During release, the six-position four-way servo valve 1 receives a voltage of -8V to -10V, and its valve core is at the leftmost end, with port P connecting to port B and port A connecting to port T, driving the injection cylinder piston to move to the right.

[0016] Specifically, during injection and retraction of the injection molding machine, the six-position four-way servo valve 1 adjusts its valve core opening according to the command signal value to achieve the speed requirement. During pressure holding and feeding, the six-position four-way servo valve 1 adjusts its valve core position according to the detection value of the pressure sensor 5 to ensure that the detection value of the pressure sensor 5 reaches the set value. The valve core voltage of the six-position four-way servo valve 1 varies between -8V and 1.5V. When the six-position four-way servo valve 1 is working, the directional valve 4 is energized and the valve port is in the left position. The control port of the cartridge valve 3 is connected to an independent return oil pipe. During retraction, the hydraulic oil in the rear oil port of the injection cylinder 2 can push the valve core of the cartridge valve 3 to the A port of the six-position four-way servo valve 1.

[0017] Specifically, when the injection molding machine enters other operations, the enable signal of the six-position four-way servo valve 1 is disconnected, the valve core of the six-position four-way servo valve 1 returns to the middle position, and at the same time, the directional valve 4 is de-energized and in the right position. The control port of the cartridge valve 3 is connected to the rear oil port in the injection cylinder 2. The hydraulic oil in the rear oil port in the injection cylinder 2 cannot pass through the cartridge valve 3 in reverse. Even if there is pressure at the front end of the screw, it will not push the screw backward. In this way, after the feeding is completed, the screw stays in the feeding end position, keeping the injection start position of the next mold unchanged and improving the injection accuracy.

[0018] Specifically, a pressure sensor 5 is connected to one side of the A port of the six-position four-way servo valve 1. The pressure sensor 5 detects the pressure in the hydraulic circuit in real time. The six-position four-way servo valve 1 adjusts the valve core position according to the detection value of the pressure sensor 5 to ensure that the detection value of the pressure sensor 5 reaches the set value.

[0019] Specifically, the cartridge valve 3 is a directional valve assembly cartridge valve.

[0020] Specifically, the directional valve 4 is a two-position four-way directional valve. The P port of the two-position four-way directional valve is connected to the rear oil port of the injection cylinder 2, the A port of the two-position four-way directional valve is connected to the control port of the cartridge valve 3, and the T port of the two-position four-way directional valve is connected to the independent return oil port. When the six-position four-way servo valve 1 is working (DPQ servo valve control card enabled), the directional valve 4 is energized and in the left position. The A port and T port of the two-position four-way directional valve are connected, and the hydraulic oil can pass through the cartridge valve 3 in both directions. Injection, release, pressure holding, feeding, and back pressure control can be achieved through the six-position four-way servo valve 1. When the six-position four-way servo valve 1 stops working, the directional valve 4 is de-energized and in the right position. The A port and P port of the two-position four-way directional valve are connected, and the oil in the injection cylinder 2 is sealed by the cartridge valve 3 and will not flow to the six-position four-way servo valve 1 to avoid screw retraction due to leakage of its core.

[0021] Specifically, a throttle element 6 is provided between the A port of the two-position four-way directional valve and the control port of the cartridge valve 3. The throttle element 6 controls the hydraulic oil flow at the control port of the cartridge valve 3, adjusts the opening and closing time of the cartridge valve 3, and reduces pipeline impact.

[0022] The working principle of this utility model is as follows: When the injection molding machine enters other operations, the enable signal of the six-position four-way servo valve 1 is disconnected, the valve core of the six-position four-way servo valve 1 returns to the middle position, and at the same time, the directional valve 4 is de-energized and in the right position. The control port of the cartridge valve 3 is connected to the rear oil port inside the injection cylinder 2. The hydraulic oil in the injection cylinder 2 cannot pass through the cartridge valve 3 in reverse. Even if there is pressure at the front end of the screw, it will not push the screw backward. In this way, after the feeding is completed, the screw stays in the feeding end position, keeping the injection start position of the next mold unchanged, thus improving the injection accuracy.

[0023] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An injection molding machine hydraulic circuit for controlling a shot action, characterized by; The utility model relates to a six-position four-way servo valve (1), a shot glue oil cylinder (2), the P mouth of six-position four-way servo valve (1) is connected with the oil inlet, six-position four-way servo valve (1) T mouth is connected with the oil return, six-position four-way servo valve (1) A mouth is connected with the shot glue oil cylinder (2) rear oil port, six-position four-way servo valve (1) B mouth is connected with the shot glue oil cylinder (2) front oil port, the shot glue oil cylinder (2) rear oil port and six-position four-way servo valve (1) A mouth between be equipped with cartridge valve (3), the control mouth of cartridge valve (3) is connected with the direction valve (4).

2. The hydraulic circuit for controlling the injection action of an injection molding machine according to claim 1, wherein The side of six-position four-way servo valve (1) A mouth is connected with the pressure sensor (5).

3. The hydraulic circuit for controlling the injection action of an injection molding machine according to claim 1, wherein The cartridge valve (3) is a direction valve assembly cartridge valve.

4. The hydraulic circuit for controlling the injection action of an injection molding machine according to claim 1, wherein The opening pressure of cartridge valve (3) is 2bar.

5. The hydraulic circuit for controlling the injection action of an injection molding machine according to claim 1, wherein The direction valve (4) is two-position four-way direction valve, the P mouth of two-position four-way direction valve is connected with the shot glue oil cylinder (2) rear oil port, two-position four-way direction valve A mouth is connected with the control mouth of cartridge valve (3), two-position four-way direction valve T mouth is connected with the independent oil return.

6. The hydraulic circuit for controlling the injection action of an injection molding machine according to claim 5, wherein The throttle (6) is arranged between the control mouth of cartridge valve (3) and the A mouth of two-position four-way direction valve.

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