A hydraulic injection molding machine oil supplement control method when performing a material storage action

Abstract

The application discloses a kind of oil supplement control methods when hydraulic injection molding machine executes storage action, by setting the installation position of second direction control valve is not lower than the installation position of injection cylinder, the A port of first direction control valve is respectively communicated with the A port, B port of second direction control valve and the rear part of injection cylinder, the T port of first direction control valve is respectively communicated with the T port of second direction control valve and oil return line, the P port of first direction control valve and the P port of second direction control valve are respectively communicated with main oil circuit, the B port of first direction control valve and the outlet of overflow valve are communicated, and the inlet of overflow valve is communicated with the front part of injection cylinder;Advantages are that when hydraulic injection molding machine executes storage action, motor is replaced by hydraulic motor, improves energy utilization efficiency, and in the process of screw retreat, vacuum does not appear in the rear part of injection cylinder, screw can retreat stably, make the internal melt of barrel uniform, can guarantee storage, subsequent injection and injection retreat action stability.

Description

Technical Field

[0001] This invention relates to an oil replenishment control method, and more particularly to an oil replenishment control method for a hydraulic injection molding machine when performing a material storage action. Background Technology

[0002] In existing hydraulic injection molding machines, during the material storage operation, a hydraulic motor drives a screw to rotate, feeding molten plastic (i.e., melted plastic) from the rear end of the barrel into the cylinder. During storage, the molten plastic continuously moves towards the front of the barrel, increasing in volume until storage is complete. During this process, the molten plastic generates pressure as it moves towards the front of the barrel, creating back pressure on the screw. When this back pressure is sufficient, it pushes the screw backward. Simultaneously, the piston rod of the injection cylinder connected to the screw moves synchronously from the rear to the front, causing the front of the injection cylinder to return oil to the oil tank via its return line, while the rear of the injection cylinder draws oil from the oil tank via its return line. Because the hydraulic motor is hydraulically driven, the return line is filled with oil from the motor's operation during the material storage operation. During the movement of the piston rod from the rear to the front of the injection cylinder, although the amount of oil returning to the oil tank from the front of the injection cylinder is inevitably less than the amount of oil required for suction from the rear due to the presence of a rod chamber, the return oil line is filled with return oil from the hydraulic motor. When oil returns from the front of the injection cylinder through the return oil line, sufficient hydraulic oil flows back to the oil tank, meeting the suction demand from the rear of the injection cylinder. At this time, the oil chamber at the rear of the injection cylinder can draw in enough oil, preventing a vacuum. The screw can retract stably, ensuring uniform melting inside the barrel, thus guaranteeing the stability of the material storage action, subsequent injection retraction, and injection ejection actions. However, as is well known, hydraulic motors have relatively low energy efficiency, resulting in high energy consumption during the material storage action of a hydraulic injection molding machine.

[0003] To reduce the energy consumption of material storage in hydraulic injection molding machines, some technicians have proposed replacing hydraulic motors with electric motors to drive the screw rotation in recent years. While this significantly reduces energy consumption for material storage, the electric motor doesn't require hydraulic oil, preventing the return oil line from being fully filled. Furthermore, the oil tank is located at a relatively low position in the machine. When the amount of oil returning from the front of the injection cylinder to the tank is less than the oil intake demand at the rear, a vacuum inevitably forms at the rear of the injection cylinder. Once a vacuum appears at the rear of the injection cylinder, the screw's retraction becomes uncontrolled and unstable, ultimately leading to instability in material storage, subsequent injection, and retraction. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for oil replenishment control when a hydraulic injection molding machine performs the material storage action. This method uses an electric motor instead of a hydraulic motor to improve energy utilization efficiency, while preventing a vacuum from appearing at the rear of the injection cylinder during the screw retraction process. The screw can retract stably, ensuring uniform melting inside the barrel and guaranteeing the stability of the material storage, subsequent injection, and injection retraction actions.

[0005] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a method for oil replenishment control when a hydraulic injection molding machine performs a material storage action. This method achieves oil replenishment control during material storage by setting a first directional control valve, a second directional control valve, and an overflow valve between the injection cylinder and the oil tank of the hydraulic injection molding machine. The second directional control valve is installed at a position no lower than the installation position of the injection cylinder in the hydraulic injection molding machine. Both the first and second directional control valves are controlled by the PID controller of the hydraulic injection molding machine. The A port of the first directional control valve is connected to the A port of the second directional control valve, the B port of the second directional control valve, and the rear of the injection cylinder of the hydraulic injection molding machine via pipelines. The T port of the first directional control valve is connected to the T port of the second directional control valve and the return oil pipeline of the hydraulic injection molding machine via pipelines. The P ports of the first and second directional control valves are connected to the main oil circuit of the hydraulic injection molding machine via pipelines. The B port of the first directional control valve and the outlet of the relief valve are connected by a pipeline. The inlet of the relief valve is connected to the front of the injection cylinder of the hydraulic injection molding machine by a pipeline. When the hydraulic injection molding machine enters the material storage state, the PID controller of the hydraulic injection molding machine controls the A port and its P port of the first directional control valve to be connected, the B port and its T port of the first directional control valve to be connected, the A port and its P port of the second directional control valve to be connected, and the T port and its B port of the second directional control valve to be connected. The hydraulic injection molding machine's oil pump operates at low speed. The second directional control valve connects the return oil line of the hydraulic injection molding machine to the rear of the injection cylinder, and the first directional control valve connects the main oil line to the rear of the injection cylinder. This ensures that the return oil line is always full of oil. The front of the injection cylinder returns oil to the oil tank through the overflow valve and the return oil line. The rear of the injection cylinder draws oil through the main oil line and the return oil line, ensuring sufficient oil intake and preventing vacuuming until the material storage is complete.

[0006] When the oil pump is running at low speed, its operating speed is 20-30% of its normal operating speed.

[0007] Compared with the prior art, the advantages of this invention are that oil replenishment control in the material storage state is achieved by setting a first directional control valve, a second directional control valve, and an overflow valve between the injection cylinder and the oil tank of the hydraulic injection molding machine. The installation position of the second directional control valve in the hydraulic injection molding machine is not lower than the installation position of the injection cylinder. Both the first directional control valve and the second directional control valve are controlled by the PID controller of the hydraulic injection molding machine. The A port of the first directional control valve is connected to the A port of the second directional control valve, the B port of the second directional control valve, and the downstream of the injection cylinder of the hydraulic injection molding machine. The components are connected via pipelines. The T port of the first directional control valve is connected to the T port of the second directional control valve and the return oil line of the hydraulic injection molding machine via pipelines. The P ports of the first and second directional control valves are connected to the main oil circuit of the hydraulic injection molding machine via pipelines. The B port of the first directional control valve and the outlet of the relief valve are connected via pipelines. The inlet of the relief valve is connected to the front of the injection cylinder of the hydraulic injection molding machine via pipelines. When the hydraulic injection molding machine enters the material storage state, the PID controller of the hydraulic injection molding machine controls the A port and the P port of the first directional control valve respectively. The hydraulic injection molding machine's oil pump operates at low speed. The first directional control valve connects its B port to its T port, the second directional control valve connects its A port to its P port, and the second directional control valve connects its T port to its B port. The second directional control valve connects the return oil line of the hydraulic injection molding machine to the rear of the injection cylinder. The first directional control valve connects the main oil circuit to the rear of the injection cylinder. The second directional control valve is installed at a higher position. Because the return oil line is connected to the main oil circuit, when the oil pump draws hydraulic oil from the tank and flows out through the main oil circuit, it also enters the return oil line. The oil pipeline ensures that the return oil pipeline is always full of oil. The front of the injection cylinder returns oil to the oil tank through the overflow valve and the return oil pipeline. The rear of the injection cylinder draws oil through the main oil circuit and the return oil pipeline. The oil intake is sufficient and will not be vacuumed until the material storage is completed. Therefore, when the hydraulic injection molding machine performs the material storage action, the electric motor replaces the hydraulic motor, which improves energy utilization efficiency. At the same time, during the screw retraction process, a vacuum will not be formed at the rear of the injection cylinder. The screw can retract stably, so that the melt inside the barrel is uniform, which can ensure the stability of material storage, subsequent injection and injection retraction actions. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the oil circuit structure of the oil replenishment control method for the hydraulic injection molding machine when performing the material storage action according to the present invention. Detailed Implementation

[0009] Example: Figure 1As shown, a method for controlling oil replenishment during the material storage action of a hydraulic injection molding machine is described. This method utilizes a first directional control valve 3, a second directional control valve 4, and an overflow valve 5 installed between the injection cylinder 1 and the oil tank 2 of the hydraulic injection molding machine to achieve oil replenishment control during material storage. The second directional control valve 4 is installed at a position no lower than the installation position of the injection cylinder 1. Both the first directional control valve 3 and the second directional control valve 4 are controlled by the PID controller 12 of the hydraulic injection molding machine. The A port of the first directional control valve 3 is connected to the A port and B port of the second directional control valve 4, and the rear a of the injection cylinder a, via pipelines. The T port of the first directional control valve 3 is connected to the T port of the second directional control valve 4 and the return oil line 6 of the hydraulic injection molding machine via pipelines. The P port of the first directional control valve 3 and the P port of the second directional control valve 4 are connected to the main oil line 7 of the hydraulic injection molding machine via pipelines. The B port of the first directional control valve 3 and... The outlet of the overflow valve 5 is connected via a pipeline, and the inlet of the overflow valve 5 is connected via a pipeline to the front part b of the injection cylinder of the hydraulic injection molding machine. When the hydraulic injection molding machine enters the material storage state, the PID controller 12 of the hydraulic injection molding machine controls the A port and P port of the first directional control valve 3 to be connected, the B port and T port of the first directional control valve 3 to be connected, the A port and P port of the second directional control valve 4 to be connected, the T port and B port of the second directional control valve 4 to be connected, and the oil pump 8 of the hydraulic injection molding machine to operate at low speed. During operation, the second directional control valve 4 connects the return oil line 6 of the hydraulic injection molding machine to the rear part a of the injection cylinder of the hydraulic injection molding machine, and the first directional control valve 3 connects the main oil line 7 to the rear part a of the injection cylinder of the hydraulic injection molding machine. At this time, the return oil line 6 will always be full of oil. The front part b of the injection cylinder returns oil to the oil tank 2 through the overflow valve 5 and the return oil line 6. The rear part a of the injection cylinder draws oil through the main oil line 7 and the return oil line 6 respectively. The oil intake is sufficient and will not be vacuumed until the material storage is completed.

[0010] In this embodiment, when the oil pump 8 is running at low speed, its operating speed is 20-30% of its normal operating speed, and the specific speed is set according to actual usage requirements.

[0011] In this embodiment, when the hydraulic injection molding machine enters the material storage state, the molten material in the storage funnel 9 flows into the screw 10. The PID controller 12 controls the storage drive motor 11 to drive the screw 10 to rotate, sending the molten material in the storage funnel 9 into the barrel. At the same time, the PID controller 12 controls the A port and P port of the first directional control valve 3 to be connected, the B port and T port of the first directional control valve 3 to be connected, the A port and P port of the second directional control valve 4 to be connected, the T port and B port of the second directional control valve 4 to be connected, and the oil pump 8 of the hydraulic injection molding machine to run at low speed. The rear part a of the injection cylinder is connected to the main oil circuit 7 and the return oil circuit 6, respectively. The front part b of the injection cylinder is connected to the return oil circuit 6 through the overflow valve. The second directional control valve 4 is installed at a higher position, and the oil pump 8 is at a lower speed. During high-speed operation, since the return oil line 6 is connected to the main oil line 7, when the oil pump 8 draws hydraulic oil from the oil tank 2 and flows out through the main oil line 7, it will also enter the return oil line 6, thus keeping the return oil line 6 full. The front part b of the injection cylinder returns oil to the oil tank 2 through the overflow valve 5 and the return oil line 6, and the rear part a of the injection cylinder draws oil through the main oil line 7 and the return oil line 6 respectively. The oil intake is sufficient and will not be vacuumed until the material storage is completed. Therefore, when the hydraulic injection molding machine performs the material storage action, the electric motor is used instead of the hydraulic motor, which improves the energy utilization efficiency. At the same time, during the retraction of the screw 10, the rear part a of the injection cylinder will not be vacuumed. The screw 10 can retract stably, so that the melt inside the barrel is uniform, which can ensure the stability of the material storage, subsequent injection and retraction actions.

Claims

1. A method for controlling oil replenishment during the material storage action of a hydraulic injection molding machine, characterized in that... Oil replenishment control during material storage is achieved by installing a first directional control valve, a second directional control valve, and an overflow valve between the injection cylinder and the oil tank of a hydraulic injection molding machine. The second directional control valve is installed at a position no lower than the injection cylinder's installation position. Both the first and second directional control valves are controlled by the hydraulic injection molding machine's PID controller. Port A of the first directional control valve is connected to Port A and Port B of the second directional control valve, and the rear of the injection cylinder via pipelines. Port T of the first directional control valve is connected to Port T of the second directional control valve and the hydraulic injection molding machine's return oil pipeline via pipelines. Ports P of both the first and second directional control valves are connected to the main oil circuit of the hydraulic injection molding machine via pipelines. Port B of the first directional control valve is connected to the outlet of the overflow valve. The overflow valve inlet is connected to the front of the injection cylinder of the hydraulic injection molding machine via a pipeline. When the hydraulic injection molding machine enters the material storage state, the PID controller of the hydraulic injection molding machine controls the A port and P port of the first directional control valve to be connected, the B port and T port of the first directional control valve to be connected, the A port and P port of the second directional control valve to be connected, the T port and B port of the second directional control valve to be connected, and the oil pump of the hydraulic injection molding machine to run at low speed. The second directional control valve connects the return oil pipeline of the hydraulic injection molding machine to the rear of the injection cylinder of the hydraulic injection molding machine, and the first directional control valve connects the main oil circuit to the rear of the injection cylinder of the hydraulic injection molding machine. At this time, the return oil pipeline will always be kept full of oil. The front of the injection cylinder returns oil to the oil tank through the overflow valve and the return oil pipeline. The rear of the injection cylinder draws oil through the main oil circuit and the return oil pipeline respectively. The oil intake is sufficient and will not be vacuumed until the material storage is completed.

2. The oil replenishment control method for a hydraulic injection molding machine during material storage operation according to claim 1, characterized in that... When the oil pump is running at low speed, its operating speed is 20-30% of its normal operating speed.

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