A hydraulic control system for the injection unit of an injection molding machine

Abstract

This invention discloses a hydraulic control system for the injection unit of an injection molding machine, including an oil pump, a first solenoid directional valve, a first cartridge valve, a first throttle, and a hydraulic actuator. The output end of the hydraulic actuator is connected to the piston of the injection cylinder, and the piston of the injection cylinder is connected to a screw via a transmission component. The first solenoid directional valve connects the output end of the oil pump to the hydraulic actuator through the first cartridge valve. The return oil circuit of the hydraulic actuator is connected back to the oil tank of the oil pump. The first throttle is used to control the response of the first cartridge valve so that the pressure oil during melting enters the drive port of the hydraulic actuator through the first cartridge valve. A second cartridge valve and a second throttle are provided at the return oil port of the hydraulic actuator. The return oil of the hydraulic actuator is controlled by the second cartridge valve and the second throttle to drive the rodless chamber of the injection cylinder, achieving a rapid back pressure response, overcoming the friction between the piston and the cylinder of the injection cylinder, ensuring the stability of the melting action, and guaranteeing the quality of the product.

Description

Technical Field

[0001] This invention relates to the field of injection molding machine technology, and in particular to a hydraulic control system for the injection unit of an injection molding machine. Background Technology

[0002] The plasticizing unit of an injection molding machine has melting and injection functions. The melting and plasticizing process is as follows: granular rubber material enters the screw channel (the gap between the inner wall of the barrel and the screw) from the feed port of the barrel. The barrel is heated to the temperature required for plasticization, and the nozzle at the front end of the barrel is closed by the hot runner valve, achieving the conditions for plasticization. At this time, the injection molding machine's control system drives the motor to rotate the screw inside the barrel to melt and plasticize the rubber material and bring it to the front end of the screw. As the amount of molten material at the front end of the screw increases, the pressure of the molten material increases due to the limited volume, pushing the screw backward. When the screw backward, the piston of the injection cylinder, which is connected to the screw through a transmission component, also backward. In order to control the pressure of the melt (the plasticized material), the resistance of the piston backward in the injection cylinder must be controlled by the hydraulic system. This resistance comes from the pressure in the return oil chamber (rodless chamber) of the injection cylinder when the piston backward. This pressure is referred to as back pressure in the field. Because the pressure fluctuates during the melting process, unstable replenishment of pressure oil will cause instability in the melt. Therefore, it is necessary to control the back pressure during the melting process to avoid fluctuations in back pressure affecting the quality of the product. However, traditional plasticizing unit hydraulic systems generally replenish oil to the return oil chamber (rodless chamber) of the injection cylinder through an oil tank. Due to the long oil replenishment pipeline of the oil tank, numerous bends in the pipeline joints, and slow pressure response, the stability of the back pressure during the melting process is affected. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the purpose of this invention is to provide an injection hydraulic control system for an injection molding machine, which enables rapid back pressure response during the plasticizing unit's melting process, ensures stable melting action, and ensures smooth screw delivery of the rubber material, thereby improving injection accuracy and guaranteeing product quality.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A hydraulic control system for an injection molding machine's injection unit includes an oil pump, a first solenoid directional valve, a first cartridge valve, a first throttle, and a hydraulic actuator. The output end of the hydraulic actuator is connected to the piston of the injection cylinder in the injection unit. The piston of the injection cylinder is connected to the screw in the injection unit via a transmission component. The first solenoid directional valve connects the output end of the oil pump to the hydraulic actuator through the first cartridge valve. The return oil circuit of the hydraulic actuator is connected back to the oil tank of the oil pump. The first throttle is used to control the response of the first cartridge valve so that when the injection unit melts the glue, pressurized oil enters the drive port of the hydraulic actuator through the first cartridge valve. A second cartridge valve and a second throttle are provided at the return oil port of the hydraulic actuator. The second throttle is used to control the response of the second cartridge valve. The outlet of the second cartridge valve is connected to the rodless chamber of the injection cylinder.

[0006] Furthermore, the hydraulic control system of the injection unit of the present invention also includes an oil pressure regulating system disposed on the oil return line of the rod chamber of the injection cylinder, for controlling the amount of oil return from the rod chamber of the injection cylinder to prevent the rod chamber of the injection cylinder from retracting.

[0007] Furthermore, the hydraulic pressure regulating system includes a second solenoid directional valve and a relief valve. The P port of the second solenoid directional valve is connected to the oil return port of the rod chamber of the injection cylinder, and the T port of the second solenoid directional valve is connected back to the oil tank. The relief valve is located between the B port of the second solenoid directional valve and the oil tank.

[0008] Furthermore, the hydraulic control system of the injection molding unit of the present invention also includes a third electromagnetic reversing valve, a third cartridge valve, and a third throttle. The third electromagnetic reversing valve connects the output end of the oil pump to the rod chamber of the injection cylinder through the third cartridge valve. The third throttle is used to control the response of the third cartridge valve so that the pressurized oil enters the rod chamber of the injection cylinder during injection, driving the piston of the injection cylinder to drive the screw to perform the injection action.

[0009] Furthermore, the hydraulic control system of the injection molding unit of the present invention also includes an electro-hydraulic directional valve. The P port of the electro-hydraulic directional valve is connected to the output end of the oil pump, the A port of the electro-hydraulic directional valve is connected to the rod chamber of the injection cylinder, the B port of the electro-hydraulic directional valve is connected to the rodless chamber of the injection cylinder, and the T port of the electro-hydraulic directional valve is connected back to the oil tank, so that when the screw in the injection molding unit is retracted, the pressure oil enters the rodless chamber of the injection cylinder.

[0010] Furthermore, in the released state, a fourth cartridge valve and a fourth throttle are provided on the return oil line of the rod chamber of the injection cylinder, and the fourth throttle is used to control the response of the fourth cartridge valve.

[0011] Furthermore, the rodless chamber of the injection cylinder is provided with a piston rod that is connected to the piston of the injection cylinder.

[0012] Furthermore, the hydraulic control system of the injection molding unit of the present invention also includes a fourth electromagnetic reversing valve. The P port of the fourth electromagnetic reversing valve is connected to the output end of the oil pump, the A port of the fourth electromagnetic reversing valve is connected to the rodless chamber of the injection cylinder in the injection molding unit, the B port of the fourth electromagnetic reversing valve is connected to the rod chamber of the injection cylinder, and the T port of the fourth electromagnetic reversing valve is connected back to the oil tank.

[0013] Furthermore, a pressure reducing valve is provided between the P port of the fourth electromagnetic reversing valve and the output end of the oil pump.

[0014] Furthermore, the hydraulic control system of the injection molding unit of the present invention also includes a first hydraulically controlled check valve and a second hydraulically controlled check valve. The rodless chamber of the injection cylinder is connected to port A of the fourth electromagnetic directional valve through the first hydraulically controlled check valve, and the rod chamber of the injection cylinder is connected to port B of the fourth electromagnetic directional valve through the second hydraulically controlled check valve.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] When the hydraulic control system of the injection molding unit controls the screw in the injection molding unit to melt the adhesive, the electromagnet b of the first electromagnetic reversing valve is energized, opening the first cartridge valve. The first throttle controls the response of the first cartridge valve, allowing pressurized oil to enter the hydraulic actuator through the first cartridge valve, thereby driving the piston of the injection cylinder to drive the screw to melt the adhesive. During the melting process, the pressure of the molten material increases, pushing the screw backward and generating back pressure. Therefore, the return oil of the hydraulic actuator is controlled by the second cartridge valve and the second throttle at the return oil point of the hydraulic actuator to drive the rodless chamber of the injection cylinder, overcoming the friction between the piston and the cylinder, thereby achieving a rapid response to back pressure, ensuring stable melting action, smooth screw conveying of adhesive, improving injection accuracy, and thus ensuring product quality. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the hydraulic control system for the injection molding unit of the present invention;

[0018] Figure 2 This is a schematic diagram of the power supply principle of the hydraulic control system for the injection molding unit of the present invention.

[0019] In the diagram: 10, oil pump; 101, oil tank; 20, first solenoid directional valve; 21, first cartridge valve; 210, first throttle; 30, hydraulic actuator; 301, second cartridge valve; 302, second throttle; 40, injection cylinder; 401, piston rod; 41, injection tail plate; 42, screw; 50, hydraulic pressure regulating system; 501, second solenoid directional valve; 502, relief valve; 503, proportional valve. Pressure valve; 504, pressure gauge; 60, fourth cartridge valve; 601, fourth throttle; 70, third solenoid directional valve; 701, third cartridge valve; 702, third throttle; 80, electro-hydraulic directional valve; 801, first check valve; 802, second check valve; 90, fourth solenoid directional valve; 901, pressure reducing valve; 902, injection cylinder; 903, first hydraulically controlled check valve; 904, second hydraulically controlled check valve. Detailed Implementation

[0020] The present invention will now be described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0021] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "horizontal," "vertical," "top," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] Implementation method:

[0024] Example:

[0025] like Figure 1-2As shown, this invention illustrates a hydraulic control system for an injection molding machine's injection unit, including an oil pump 10, a first solenoid directional valve 20, a first cartridge valve 21, a first throttle valve 210, and a hydraulic actuator 30. The hydraulic actuator 30 is a hydraulic motor, the output of which is connected to the piston of the injection cylinder 40 in the injection unit. The piston of the injection cylinder 40 is connected to the screw 42 in the injection unit via a transmission component. The first solenoid directional valve 20 is connected to the output of the oil pump 10 through the first cartridge valve 21. At the drive port of the hydraulic motor, the return oil circuit of the hydraulic motor is connected to the oil tank 101 of the return oil pump 10. The first throttle is used to control the response of the first cartridge valve 21 so that when the injection molding unit melts the glue, the pressure oil enters the drive port of the hydraulic motor through the first cartridge valve 21. At the return oil port of the hydraulic motor, there is a second cartridge valve 301 and a second throttle 302. The second throttle 302 is used to control the response of the second cartridge valve 301. The oil outlet of the second cartridge valve 301 is connected to the rodless chamber of the injection cylinder 40. Therefore, it can be understood that during the melting process, the electromagnet b of the first electromagnetic directional valve 20 is energized, opening the first cartridge valve 21. The first throttle 210 controls the response of the first cartridge valve 21, allowing the pressurized oil in the oil tank 101 of the oil pump 10 to enter the hydraulic actuator 30 through the first cartridge valve 21, thereby driving the piston of the injection cylinder 40 to drive the screw 42 to melt the adhesive. During the melting process, the increased pressure of the molten material pushes the screw 42 backward, generating back pressure. Therefore, the second cartridge valve 301 and the second throttle 302, located at the return oil point of the hydraulic actuator 30, control the return oil of the hydraulic actuator 30 to drive the rodless chamber of the injection cylinder 40, overcoming the friction between the piston and the cylinder, thereby achieving a rapid response to back pressure, ensuring the stability of the melting process, and ensuring smooth delivery of adhesive by the screw 42, thus improving the injection accuracy and guaranteeing the quality of the product.

[0026] It should be noted that the oil circuit of the oil pump is existing technology, and its control principle will not be explained here.

[0027] In this embodiment, a first check valve 801 is provided on the oil outlet of the second cartridge valve 301 into the rodless chamber of the injection cylinder 40. The first check valve 801 controls and prevents the oil in the rodless chamber of the injection cylinder 40 from entering the second cartridge valve 301, thereby controlling the direction of the pressurized oil from the second cartridge valve 301 into the rodless chamber of the injection cylinder 40.

[0028] As a preferred embodiment, the hydraulic control system of the injection molding unit of the present invention may further include the following additional technical features: an oil pressure regulating system 50 is provided on the oil return line of the rod chamber of the injection cylinder 40. The oil pressure regulating system 50 controls the amount of oil return from the rod chamber of the injection cylinder 40 to prevent the rod chamber of the injection cylinder 40 from retracting, thereby avoiding the friction between the piston and the cylinder of the injection cylinder 40, further improving the response speed of the back pressure of the injection unit during melting, ensuring stable melting action, smooth delivery of the material by the screw 42, improving injection accuracy, and ensuring product accuracy.

[0029] Specifically, the hydraulic pressure regulating system 50 includes a second solenoid directional valve 501 and a relief valve 502. The P port of the second solenoid directional valve 501 is connected to the return port of the rod chamber of the injection cylinder 40, and the T port of the second solenoid directional valve 501 is connected back to the oil tank 101. The relief valve 502 is located between the B port of the second solenoid directional valve 501 and the oil tank 101. When the electromagnet b of the second solenoid directional valve 501 is energized, a certain pressure is generated. The return oil from the rod chamber of the injection cylinder 40 enters the B port of the second solenoid directional valve 501 through the P port, and then returns to the oil tank 101 through the relief valve 502. Therefore, by adjusting the valve port of the overflow valve 502 and controlling its return oil volume, the return oil volume of the rod chamber of the injection cylinder 40 can be controlled, thereby achieving the effect of hindering the retraction of the rod chamber of the injection cylinder 40. Specifically, when the electromagnet b of the second solenoid directional valve 501 is not energized, the return oil from the rod chamber of the injection cylinder 40 enters from port P of the second solenoid directional valve 501, enters port A of the second solenoid directional valve 501, and finally flows back to the oil tank 101 from port T of the second solenoid directional valve 501. Furthermore, the oil pressure regulating system also includes a pressure gauge 504, which is used to display the oil pressure of the oil pressure regulating system, thereby facilitating the operator to adjust the valve port of the overflow valve 502 to control the return oil volume of the rod chamber of the injection cylinder 40.

[0030] It should be noted that in other embodiments, the overflow valve 502 can also be replaced by a proportional pressure valve 503, and the return oil volume of the rod chamber of the injection cylinder 40 can be automatically controlled by setting the pressure of the proportional pressure valve 503.

[0031] In this embodiment, the injection unit hydraulic control system further includes a third electromagnetic reversing valve 70, a third cartridge valve 701, and a third throttle 702. The third electromagnetic reversing valve 70 connects the output end of the oil pump 10 to the rod chamber of the injection cylinder 40 through the third cartridge valve 701. The third throttle 702 is used to control the response of the third cartridge valve 701 so that the pressurized oil enters the rod chamber of the injection cylinder 40 during injection, thereby driving the piston of the injection cylinder 40 to move the screw 42 forward to perform the injection action. In other words, it can be understood that during injection or pressure holding (the melt is pushed by the screw 42 to generate a high injection pressure, which is injected into the mold cavity, and the pressure is maintained appropriately during the subsequent cooling time, which is called pressure holding), the electromagnet b of the third electromagnetic reversing valve 70 is energized, opening the third cartridge valve 701. The response of the third cartridge valve 701 is controlled by the third throttle 702, so that the pressure oil enters the right chamber (rod chamber) of the injection cylinder 40 through the third cartridge valve 701, pushing the piston of the injection cylinder 40 to drive the screw 42 forward to perform the injection action. At the same time, the oil in the left chamber (rodless chamber) of the injection cylinder 40 flows back to the oil tank 101.

[0032] In this embodiment, the hydraulic control system of the injection molding unit also includes an electro-hydraulic directional valve 80. The P port of the electro-hydraulic directional valve 80 is connected to the output end of the oil pump 10. The A port of the electro-hydraulic directional valve 80 is connected to the rod chamber of the injection cylinder 40, the B port of the electro-hydraulic directional valve 80 is connected to the rodless chamber of the injection cylinder 40, and the T port of the electro-hydraulic directional valve 80 is connected back to the oil tank 101, so that when the screw 42 in the injection molding unit retracts, the pressurized oil enters the rodless chamber of the injection cylinder 40. That is, during retraction (release: screw 42 retracts), the electromagnet b of the electro-hydraulic directional valve 80 is energized, and the pressurized oil directly drives the left chamber of the injection cylinder 40 through the electro-hydraulic directional valve 80, while the return oil from the right chamber of the injection cylinder 40 enters the oil tank 101. Furthermore, a second check valve 802 is installed on the pipeline connecting the T port of the electro-hydraulic directional valve 80 to the oil tank 101. This second check valve 802 prevents the pressure oil from flowing back into the electro-hydraulic directional valve 80 and controls the flow direction of the pressure oil.

[0033] In this embodiment, a fourth cartridge valve 60 and a fourth throttle 601 are provided on the return oil line of the rod chamber of the injection cylinder 40. The fourth throttle 601 is used to control the response of the fourth cartridge valve 60. That is, it can be understood that when the injection unit is in the retracted state, the return oil from the right chamber of the injection cylinder 40 returns to the oil tank 101 through the fourth cartridge valve 60, thereby ensuring stable retraction, no impact, and no creeping phenomenon.

[0034] In this embodiment, the rodless chamber of the injection cylinder 40 is provided with a piston rod 401 connected to the piston of the injection cylinder 40. Those skilled in the art will understand that adding this piston rod 401 can save the hydraulic driving force of the rodless chamber of the injection cylinder 40 during the reverse operation of the injection unit, thereby achieving the effect of energy saving.

[0035] In this embodiment, the hydraulic control system of the injection molding unit also includes a fourth solenoid directional valve 90. The P port of the fourth solenoid directional valve 90 is connected to the output end of the oil pump 10, the A port of the fourth solenoid directional valve 90 is connected to the rod chamber of the injection cylinder 902 in the injection molding unit, the B port of the fourth solenoid directional valve 90 is connected to the rodless chamber of the injection cylinder 902, and the T port of the fourth solenoid directional valve 90 is connected back to the oil tank 101. That is, it can be understood that when the injection unit moves forward (injection moving platform), the electromagnet b of the fourth solenoid directional valve 90 is energized, and pressurized oil enters the rodless chamber of the injection cylinder 902 through the B port of the fourth solenoid directional valve 90, driving the piston of the injection cylinder 902 to move the injection moving platform to conform to the mold, preparing for the injection action. Oil in the rod chamber of the injection cylinder 902 enters the fourth solenoid directional valve 90 through the A port of the fourth solenoid directional valve 90. The oil flows back to the oil tank 101 of the oil pump 10 from the T port of the solenoid directional valve. When the injection shifts backward, the electromagnet a of the fourth solenoid directional valve 90 is energized, and the pressurized oil enters the rod chamber of the injection shift cylinder 902, driving the piston of the injection shift cylinder 902 to move the injection platform backward. The oil in the rodless chamber of the injection shift cylinder 902 enters the fourth solenoid directional valve 90 through the B port and flows back to the oil tank 101 of the oil pump 10 from the T port of the solenoid directional valve.

[0036] In this embodiment, a pressure reducing valve 901 is provided between the P port of the fourth solenoid directional valve 90 and the output end of the oil pump 10. The return oil port of the pressure reducing valve 901 and the return oil path of the T port of the fourth solenoid directional valve 90 both flow back to the oil tank 101 through the aforementioned second check valve 802. Therefore, it can be understood that when the injection moves forward, the pressure reducing valve 901 reduces the pressure of the oil to a safe pressure before it enters the injection cylinder 902 to drive the injection platform forward, avoiding excessive pressure that could cause impact during the injection platform's movement. This prevents damage to the mold or the spherical surface of the nozzle when it contacts the mold. When the injection moves backward, the pressure reducing valve 901 first reduces the pressure of the oil to a safe pressure, preventing excessive pressure that could cause impact during the backward injection.

[0037] In this embodiment, the injection molding unit hydraulic control system further includes a first hydraulic check valve 903 and a second hydraulic check valve 904. The rodless chamber of the injection cylinder 902 is connected to port A of the fourth electromagnetic directional valve 90 through the first hydraulic check valve 903, and the rod chamber of the injection cylinder 902 is connected to port B of the fourth electromagnetic directional valve 90 through the second hydraulic check valve 904. Therefore, when the injection moves forward, the electromagnet b of the fourth solenoid directional valve 90 is energized. The pressure oil is reduced to a safe pressure by the pressure reducing valve 901 and then enters the rodless chamber of the injection cylinder 902 through the first hydraulic check valve 903, driving the injection platform to move forward. The oil in the rod chamber of the injection cylinder 902 enters the fourth solenoid directional valve 90 and the second check valve 802 through the second hydraulic check valve 904, and finally flows back to the oil tank 101. When the injection moves backward, the electromagnet a of the fourth solenoid directional valve 90 is energized. The pressure oil is reduced to a safe pressure by the pressure reducing valve 901 and then enters the rod chamber of the injection cylinder 902 through the second hydraulic check valve 904, driving the injection platform to move backward. The oil in the rodless chamber of the injection cylinder 902 enters the fourth solenoid directional valve 90 and the second check valve 802 through the first hydraulic check valve 903, and finally flows back to the oil tank 101.

[0038] The working principle of the hydraulic control system for the injection molding unit of this invention:

[0039] 1. When the injection moves forward, the electromagnet b of the fourth solenoid directional valve 90 is energized. The pressure oil is first reduced to a safe pressure through the pressure reducing valve 901B, and then enters the rodless chamber of the injection cylinder 902 through the first hydraulic control check valve 903 to drive the injection moving platform to move forward. The oil in the rod chamber of the injection cylinder 902 enters the fourth solenoid directional valve 90 and the second check valve 802 through the second hydraulic control check valve 904, and finally flows back to the oil tank 101.

[0040] 2. During injection or pressure holding, the electromagnet b of the third solenoid directional valve 70 and the electromagnet b of the fourth solenoid directional valve 90 are energized (ensuring the injection moving platform fits the mold), opening the third cartridge valve 701. The response of the third cartridge valve 701 is controlled by the third throttle valve 702, and the pressure oil enters the right chamber of the injection cylinder 40 through the third cartridge valve 701 to perform the injection action. At the same time, the oil in the left chamber of the injection cylinder 40 flows back to the oil tank 101 through the electro-hydraulic directional valve 80 and the second check valve 802.

[0041] 3. During the melting action, the solenoid b of the first solenoid directional valve 20 and the solenoid b of the fourth solenoid directional valve 90 are energized (ensuring the injection moving platform adheres to the mold). Pressure oil enters the drive port of the hydraulic motor through the second cartridge valve 301. During the back pressure action, the solenoid b of the second solenoid directional valve 501 is energized, setting a certain pressure to hinder the retraction of the rod chamber of the injection cylinder 40, controlling the return oil volume of the rod chamber, and avoiding the friction between the piston and the cylinder of the injection cylinder 40, as well as the friction from the sliding of the transmission components. The force ensures a rapid back pressure response during the melting process, guaranteeing stable melting action, smooth material delivery by the screw 42, improved injection accuracy, and thus ensuring product precision. Simultaneously, the return oil of the hydraulic motor is controlled by the second cartridge valve 301 and the second throttle 302 at the return oil point of the hydraulic motor to drive the rodless chamber of the injection cylinder 40, achieving a rapid back pressure response and overcoming the friction between the piston and the cylinder of the injection cylinder 40, the resistance of the weight of the injection tail plate 41, and the friction of sliding with the transmission components.

[0042] 4. During the reversing action, the electromagnet b of the electric reversing valve is energized, and the pressure oil directly drives the left chamber of the injection cylinder 40 through the electric reversing valve. The oil in the right chamber of the injection cylinder 40 returns to the oil tank 101 through the fourth cartridge valve 60. The opening of the fourth cartridge valve 60 is controlled by the fourth throttle 601.

[0043] 5. When the injection shifts backward, the electromagnet a of the fourth solenoid directional valve 90 is energized. The pressure oil is reduced to a safe pressure through the pressure reducing valve 901 and then enters the rod chamber of the injection cylinder 902 through the second hydraulic control check valve 904, driving the injection platform to move backward. The oil in the rodless chamber of the injection cylinder 902 enters the fourth solenoid directional valve 90 and the second check valve 802 through the first hydraulic control check valve 903 and finally flows back to the oil tank 101.

[0044] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A hydraulic control system for an injection molding unit of an injection molding machine, comprising an oil pump (10), a first solenoid directional valve (20), a first cartridge valve (21), a first throttle (210), and a hydraulic actuator (30), wherein the output end of the hydraulic actuator (30) is connected to the piston of the injection cylinder (40) in the injection molding unit, the piston of the injection cylinder (40) is connected to the screw (42) in the injection molding unit via a transmission component, the first solenoid directional valve (20) connects the output end of the oil pump (10) to the hydraulic actuator (30) via the first cartridge valve (21), the return oil circuit of the hydraulic actuator (30) is connected back to the oil tank (101) of the oil pump (10), and the first throttle (210) is used to control the response of the first cartridge valve (21) so that when the injection molding unit melts the glue, the pressure oil enters the drive port of the hydraulic actuator (30) through the first cartridge valve (21); characterized in that: A second cartridge valve (301) and a second throttle (302) are provided at the return port of the hydraulic actuator (30). The second throttle (302) is used to control the response of the second cartridge valve (301). The outlet of the second cartridge valve (301) is connected to the rodless chamber of the injection cylinder (40). It also includes an oil pressure regulating system installed on the oil return line of the rod chamber of the injection cylinder (40) to control the amount of oil return from the rod chamber of the injection cylinder (40) and prevent the rod chamber of the injection cylinder (40) from retracting. The hydraulic pressure regulating system includes a second electromagnetic reversing valve (501) and an overflow valve (502). The P port of the second electromagnetic reversing valve (501) is connected to the oil return port of the rod chamber of the injection cylinder (40). The T port of the second electromagnetic reversing valve (501) is connected back to the oil tank (101). The overflow valve (502) is located between the B port of the second electromagnetic reversing valve (501) and the oil tank (101). It also includes an electro-hydraulic directional valve (80), the P port of which is connected to the output end of the oil pump (10), the A port of which is connected to the rod chamber of the injection cylinder (40), the B port of which is connected to the rodless chamber of the injection cylinder (40), and the T port of which is connected back to the oil tank (101) so that when the screw (42) in the injection unit is released, the pressure oil enters the rodless chamber of the injection cylinder (40).

2. The hydraulic control system for the injection unit of an injection molding machine as described in claim 1, characterized in that: It also includes a third electromagnetic reversing valve (70), a third cartridge valve (701), and a third throttle (702). The third electromagnetic reversing valve (70) connects the output end of the oil pump (10) to the rod chamber of the injection cylinder (40) through the third cartridge valve (701). The third throttle (702) is used to control the response of the third cartridge valve (701) so that the pressurized oil enters the rod chamber of the injection cylinder (40) during injection to drive the piston of the injection cylinder (40) to drive the screw (42) to perform the injection action.

3. The hydraulic control system for the injection unit of an injection molding machine as described in claim 1, characterized in that: In the released state, a fourth cartridge valve (60) and a fourth throttle (601) are provided on the return oil line of the rod chamber of the injection cylinder (40). The fourth throttle (601) is used to control the response of the fourth cartridge valve (60).

4. The hydraulic control system for the injection unit of an injection molding machine as described in claim 1 or 3, characterized in that: The rodless chamber of the injection cylinder (40) is provided with a piston rod (401) that is connected to the piston of the injection cylinder (40).

5. The hydraulic control system for the injection unit of an injection molding machine as described in claim 1, characterized in that: It also includes a fourth electromagnetic directional valve (90), the P port of which is connected to the output end of the oil pump (10), the A port of which is connected to the rodless chamber of the injection cylinder (902) in the injection unit, the B port of which is connected to the rod chamber of the injection cylinder (902), and the T port of which is connected back to the oil tank (101).

6. The hydraulic control system for the injection unit of an injection molding machine as described in claim 5, characterized in that: A pressure reducing valve (901) is provided between the P port of the fourth electromagnetic reversing valve (90) and the output end of the oil pump (10).

7. The hydraulic control system for the injection unit of an injection molding machine as described in claim 5, characterized in that: It also includes a first hydraulically controlled check valve (903) and a second hydraulically controlled check valve (904). The rodless chamber of the ejector cylinder (902) is connected to port A of the fourth electromagnetic directional valve (90) through the first hydraulically controlled check valve (903), and the rod chamber of the ejector cylinder (902) is connected to port B of the fourth electromagnetic directional valve (90) through the second hydraulically controlled check valve (904).

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