Pressure injection system for caster

Abstract

To provide a pressure injection system capable of resolving such defects of a pressure injection system for a caster as a possible occurrence of a startup impact in a low-rate startup stage and poor control of accuracy.SOLUTION: A pressure injection system comprises an energy accumulator 3 connected by an oil line, an injection hydraulic cylinder 1, a pressure-boosting hydraulic cylinder 2, and a valve module. In a low-rate pressure injection stage of the injection hydraulic cylinder, the valve module is used to change over between a single oil-feed mode of the oil line by a pump and a common oil-feed mode of the oil line by the pump and the energy accumulator. In high-rate pressure injection, braking, and follow-up stages of the injection hydraulic cylinder, the valve module communicates the pump and the tank on the oil line to form an A-type semi-bridge structure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of metal casting, and more particularly to pressure injection systems in casting equipment. [Background technology]

[0002] A casting machine is a device used for pressure casting, and is often used in the production and processing of automobile parts, etc. The casting machine uses pressure to inject molten metal liquid into a mold, where the metal is cooled and shaped. The mold is then opened to obtain a solid metal casting.

[0003] The pressure injection operation of the current cooling chamber casting machine includes processes such as low-speed pressure injection, high-speed pressure injection, and boost pressure injection. In this case, after the high-speed pressure injection is completed, the injection hydraulic cylinder must be braked before preparing for the boost pressure injection. After the pressure injection operation is completed, the casting machine returns to its initial position by performing a decompression process, a follow-up process, and a hammer return process.

[0004] However, the pressure injection system of the current casting equipment has the following drawbacks when carrying out the above process.

[0005] (1) There is a risk of starting shock occurring during the low-speed starting stage, and precision control is poor.

[0006] (2) There is a risk of excessive velocity during the high-speed pressure injection stage.

[0007] (3) During the boost injection stage, the amount of oil discharged may exceed or be insufficient to the specified value, resulting in poor accuracy of the boost pressure.

[0008] (4) During the braking phase, braking may be slow and the braking effect may be reduced.

[0009] (5) During the following stage, there is a risk that the hammerhead will not be able to be controlled, resulting in an inability to control the following.

[0010] In view of the above, there is a need to improve the pressure injection systems of current casting machines. Summary of the Invention

[0011] SUMMARY OF THE INVENTION The present invention aims to provide a pressure injection system that can overcome at least one of the deficiencies of the background art described above.

[0012] In order to achieve at least one of the above-mentioned objects, according to the present invention, there is provided a pressure injection system for a casting machine, comprising: an energy accumulator, an injection hydraulic cylinder, a booster hydraulic cylinder, and a valve module, which are connected by an oil line; in a low-speed pressure injection stage of the injection hydraulic cylinder, the valve module is used to switch between a mode in which the oil line is supplied solely by the pump and a mode in which the oil line is supplied jointly by the pump and the energy accumulator; in a high-speed pressure injection stage, a braking stage, and a following stage, the valve module connects a rod-containing cavity of the injection hydraulic cylinder to the pump and a tank of the oil line so as to form an A-shaped half-bridge structure; and in a booster injection stage of the injection hydraulic cylinder, the valve module connects the rod-containing cavity of the booster hydraulic cylinder to the pump and a tank of the oil line so as to form an A-shaped half-bridge structure.

[0013] The valve module includes an on-off valve V5, an on-off valve V8, a servo valve V9, a check valve V11, and a check valve V13, and the output port of the pump is connected to the rod-equipped cavity of the injection hydraulic cylinder by the check valve V11 and the servo valve V9 connected in series in this order to form a first oil passage, and the output port of the pump is connected to the rod-less cavity of the injection hydraulic cylinder by the check valve V11, the check valve V13, the on-off valve V8, and the on-off valve V5 connected in series in this order to form a third oil passage, and in an individual oil supply mode by the pump for low-speed pressure injection, it is preferable that the pump supplies oil to the rod-less cavity of the injection hydraulic cylinder through the opened third oil passage, and that a differential circuit is formed by the first oil passage and the third oil passage.

[0014] Preferably, the valve module includes an on-off valve V4, and the energy accumulator is connected to the rodless cavity of the injection hydraulic cylinder by on-off valves V4 and V5 connected in series to form a fourth oil passage, and in a joint oil supply mode by the pump and the energy accumulator during low-speed pressure injection, in addition to the individual oil supply by the pump, the energy accumulator also supplies oil to the rodless cavity of the injection hydraulic cylinder through the opened fourth oil passage.

[0015] Preferably, the valve module includes a servo valve V7, and the tank is connected to the rod-equipped cavity of the injection hydraulic cylinder by the servo valve V7 to form a fifth oil passage, and during the high-speed pressure injection stage and braking stage of the injection hydraulic cylinder, the energy accumulator supplies oil to the rodless cavity of the injection hydraulic cylinder through the connected fourth oil passage, and the pressure oil in the rod-equipped cavity of the injection hydraulic cylinder is returned to the tank along the connected fifth oil passage, and the first oil passage and the fifth oil passage are connected to form an A-type half-bridge structure, and the pressure injection speed of the injection hydraulic cylinder is adjusted by controlling the opening of the servo valves V7 and V9.

[0016] Preferably, the valve module includes an on-off valve V12, and the output port of the pump is connected to the energy accumulator by the on-off valve V12 to form a second oil passage, and during the follow-up stage of the injection hydraulic cylinder, the pump and the energy accumulator supply oil to the rodless cavity of the injection hydraulic cylinder through the connected third oil passage and the connected fourth oil passage, respectively, and the pump supplies oil to the energy accumulator through the second oil passage, and the pressure oil in the rod-equipped cavity of the injection hydraulic cylinder is returned to the tank along the connected fifth oil passage, and the first oil passage and the fifth oil passage are connected to form an A-type half-bridge structure, and the pressure injection speed of the injection hydraulic cylinder is adjusted by controlling the aperture of the servo valves V7 and V9.

[0017] The valve module includes an on-off valve V6, the energy storage device is connected to the rodless cavity of the booster hydraulic cylinder by an on-off valve V4 to form a sixth oil passage, the tank is connected to the rod-equipped cavity of the booster hydraulic cylinder by a servo valve V7 and an on-off valve V6 connected in series in this order to form a seventh oil passage, the output port of the pump is connected to the rod-equipped cavity of the booster hydraulic cylinder by a check valve V11, a servo valve V9 and an on-off valve V6 connected in series in this order to form an eighth oil passage, and the booster injection of the injection hydraulic cylinder In the ejection step, it is preferable that the energy accumulator supplies oil to the rodless cavity of the boosting hydraulic cylinder through the connected sixth oil passage, and the pressure oil of the rod-equipped cavity of the boosting hydraulic cylinder and the pressure oil of the rod-equipped cavity of the injection hydraulic cylinder are returned to the tank along the connected seventh oil passage and the connected fifth oil passage, respectively, the eighth oil passage and the seventh oil passage are connected to form an A-type half-bridge structure, and the boosting pressure of the boosting hydraulic cylinder is adjusted by controlling the opening of servo valves V7 and V9.

[0018] When depressurizing after the completion of the boosting pressure injection stage, it is preferable that the supply of oil from the energy accumulator to the rodless cavity of the boosting hydraulic cylinder is stopped, and the opening of the servo valve V9 is increased and the opening of the servo valve V7 is decreased, so that the pump supplies oil to the rod-equipped cavity of the boosting hydraulic cylinder through the opened eighth oil passage, and the boosting hydraulic cylinder returns, and the pressure oil in the rodless cavity is returned to the energy accumulator along the opened sixth oil passage.

[0019] It is preferable that the valve module includes an on-off valve V10, the tank is connected to the rodless cavity of the boosting hydraulic cylinder by the on-off valve V10 to form a ninth oil passage, the tank is connected to the rodless cavity of the injection hydraulic cylinder by the on-off valve V10 and the on-off valve V5 connected in series in this order to form a tenth oil passage, and when the hammer return step is performed after the follow-up step is completed, the pump supplies oil to the rod-equipped cavity of the injection hydraulic cylinder and the rod-equipped cavity of the boosting hydraulic cylinder through the opened first oil passage and the opened eighth oil passage, respectively, and the rodless cavity of the injection hydraulic cylinder and the rodless cavity of the boosting hydraulic cylinder return pressurized oil to the tank through the opened tenth oil passage and the opened ninth oil passage, respectively.

[0020] The valve module includes a servo valve V14 and a servo valve V15, and the energy accumulator is connected to the rodless cavity of the boosting hydraulic cylinder by the servo valve V4 to form a sixth oil passage, the energy accumulator is connected to the rod-equipped cavity of the boosting hydraulic cylinder by the servo valve V14 to form an eleventh oil passage, and the tank is connected to the rod-equipped cavity of the boosting hydraulic cylinder by the servo valve V15 to form a twelfth oil passage, and during the boosting injection stage of the injection hydraulic cylinder, the energy accumulator supplies oil to the rodless cavity of the boosting hydraulic cylinder through the opened sixth oil passage, and pressure oil in the rod-equipped cavity of the injection hydraulic cylinder is returned to the tank along the opened fifth oil passage, and the eleventh oil passage and the twelfth oil passage are opened to form an A-type half-bridge structure, and it is preferable that the boosting pressure of the boosting hydraulic cylinder is adjusted by controlling the opening of the servo valves V14 and V15.

[0021] When the pressure is reduced after the boosted injection stage is completed, it is preferable that the fifth oil passage and the twelfth oil passage are blocked and the sixth oil passage and the eleventh oil passage are connected, but the supply of oil from the energy accumulator to the sixth oil passage is stopped, so that the energy accumulator supplies oil to the rod-equipped cavity of the boosted hydraulic cylinder through the eleventh oil passage, and the boosted hydraulic cylinder returns, and the pressurized oil in the rod-less cavity is returned to the energy accumulator along the connected sixth oil passage.

[0022] It is preferable that the valve module includes an on-off valve V10, the tank is connected to the rodless cavity of the boosting hydraulic cylinder by the on-off valve V10 to form a ninth oil passage, the tank is connected to the rodless cavity of the injection hydraulic cylinder by the on-off valve V10 and the on-off valve V5 connected in series in this order to form a tenth oil passage, and the pump is connected to the rod-equipped cavity of the boosting hydraulic cylinder by the on-off valve V12 and the servo valve V14 connected in series in this order to form a thirteenth oil passage, and when the hammer return step is performed after the completion of the following step, the pump supplies oil to the rod-equipped cavity of the injection hydraulic cylinder and the rod-equipped cavity of the boosting hydraulic cylinder by the opened first oil passage and the opened thirteenth oil passage, respectively, and the rodless cavity of the injection hydraulic cylinder and the rodless cavity of the boosting hydraulic cylinder return pressurized oil to the tank by the opened tenth oil passage and the opened ninth oil passage, respectively.

[0023] Compared with the prior art, the present invention can achieve the following advantages.

[0024] (1) In the low-speed pressure injection stage, by increasing the independent oil supply mode of the oil passage by the pump, and combining the independent oil supply mode of the oil passage by the pump and the joint oil supply mode of the oil passage by the pump and the energy reservoir, the oil consumption of the energy reservoir can be efficiently reduced and the dynamic injection force of the injection hydraulic cylinder can be improved.

[0025] (2) By designing the oil passage, an A-type half-bridge structure is obtained, which can control the speed of the injection hydraulic cylinder and the boost pressure of the boost hydraulic cylinder. Compared to the conventional method, it can effectively avoid or reduce overspeed, and ensure the stability and control accuracy of the boost injection pressure. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic diagram of an oil passage structure of a pressure injection system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing oil passages and the like in an energy storage stage according to the first embodiment of the present invention. [Figure 3] 3 is a schematic diagram showing oil passages and the like in a low-speed pressure injection stage performed solely by a pump according to the first embodiment of the present invention. FIG. [Figure 4] FIG. 2 is a schematic diagram showing oil passages etc. in a low-speed pressure injection stage performed jointly by a pump and an energy accumulator according to the first embodiment of the present invention. [Figure 5] 1 is a schematic diagram showing oil passages and the like in a high-speed pressure injection stage and a braking stage according to a first embodiment of the present invention. FIG. [Figure 6] FIG. 2 is a schematic diagram showing oil passages and the like in a pressure increase delay stage according to the first embodiment of the present invention. [Figure 7] FIG. 2 is a schematic diagram showing oil passages and the like in a pressure boost load stage according to the first embodiment of the present invention. [Figure 8] FIG. 2 is a schematic diagram showing oil passages and the like in a pressure reduction stage according to the first embodiment of the present invention. [Figure 9] FIG. 2 is a schematic diagram showing oil passages and the like in a follow-up stage according to the first embodiment of the present invention. [Figure 10] FIG. 3 is a schematic diagram showing oil passages and the like in a hammer return stage according to the first embodiment of the present invention. [Figure 11] 1 is a partial schematic diagram of the relationship curve between pressure injection position, pressure injection speed, and casting pressure of a conventional pressure injection system. [Figure 12] FIG. 2 is a partial schematic diagram of the relationship curve between pressure injection position, pressure injection speed and casting pressure of the present invention. [Figure 13]FIG. 6 is a schematic diagram of an oil passage structure of a pressure injection system according to a second embodiment of the present invention. [Figure 14] FIG. 10 is a schematic diagram showing oil passages and the like in an energy storage stage according to a second embodiment of the present invention. [Figure 15] FIG. 10 is a schematic diagram showing oil passages and the like in a low-speed pressure injection stage performed solely by a pump according to a second embodiment of the present invention. [Figure 16] FIG. 10 is a schematic diagram showing oil passages etc. in a low-speed pressure injection stage performed jointly by a pump and an energy accumulator according to a second embodiment of the present invention. [Figure 17] FIG. 10 is a schematic diagram showing oil passages and the like in a high-speed pressure injection stage and a braking stage according to a second embodiment of the present invention. [Figure 18] FIG. 10 is a schematic diagram showing oil passages and the like in a pressure increase delay stage according to a second embodiment of the present invention. [Figure 19] FIG. 10 is a schematic diagram showing oil passages and the like in a pressure boost load stage according to a second embodiment of the present invention. [Figure 20] FIG. 10 is a schematic diagram showing oil passages and the like in a pressure reduction stage according to a second embodiment of the present invention. [Figure 21] FIG. 10 is a schematic diagram showing oil passages and the like in a follow-up stage according to a second embodiment of the present invention. [Figure 22] FIG. 10 is a schematic view showing oil passages and the like in a hammer return stage according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention will be further described below with reference to specific embodiments, in which, unless inconsistent, the embodiments and technical features described below can be arbitrarily combined to form new embodiments.

[0028] Directional terms such as "center," "lateral direction," "longitudinal direction," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise" used in the embodiments indicate directions and positional relationships shown in the drawings. These terms are used merely to facilitate explanation of the embodiments and do not directly or indirectly indicate a specific direction of a device or the like, nor do they limit the scope of protection of the present application.

[0029] Additionally, the terms "first" and "second" used in the specification and claims of this application are intended to distinguish between similar objects and not to describe a particular order.

[0030] As used in the specification and claims of this application, "including," "having," and any variations thereof are intended to mean inclusive and not exclusive. For example, a method, system, article of manufacture, or apparatus is not limited to the recited steps or units, but may include steps or units that are not recited.

[0031] As shown in Figures 1 to 22, a pressure injection system of a casting machine according to a preferred embodiment of the present invention includes an energy storage device 3, an injection hydraulic cylinder 1, a booster hydraulic cylinder 2, and a valve module, all connected by oil lines. During the low-speed pressure injection stage of the injection hydraulic cylinder 1, the valve module is used to switch between a pump-based oil line single-lubrication mode and a pump and energy storage device 3-based oil line joint-lubrication mode. During the high-speed pressure injection stage, braking stage, and follow-up stage of the injection hydraulic cylinder 1, the valve module connects the rod-containing cavity of the injection hydraulic cylinder 1 to the pump and tank in the oil line, forming an A-shaped half-bridge structure. During the booster injection stage of the injection hydraulic cylinder 1, the valve module connects the rod-containing cavity of the booster hydraulic cylinder 2 to the pump and tank in the oil line, forming an A-shaped half-bridge structure.

[0032] In conventional pressure injection systems, the control mode of the pressure injection speed of the injection hydraulic cylinder 1 is relatively single. Usually, in order to ensure stable operation of the injection hydraulic cylinder 1, oil is supplied to the injection hydraulic cylinder 1 by the energy accumulator 3 during the low-speed pressure injection stage. Because the duration of the low-speed pressure injection stage is relatively long and power output is required from the energy accumulator 3 during each of the subsequent pressure injection stages, the oil consumption during the low-speed pressure injection stage affects the subsequent pressure injection process.

[0033] In this embodiment, the injection hydraulic cylinder 1, the energy reservoir 3, and the pump are connected to the oil passages by the valve module, and thus there are three oil supply modes for the injection hydraulic cylinder 1 during the low-speed pressure injection phase. In the first oil supply mode, the injection hydraulic cylinder 1 is supplied with oil by the pump. In the second oil supply mode, the injection hydraulic cylinder 1 is supplied with oil by the energy reservoir 3. In the third oil supply mode, the injection hydraulic cylinder 1 is supplied with oil by the pump and the energy reservoir 3. To further ensure the stability of the pressure injection phase, the oil supply mode during the low-speed pressure injection phase in this embodiment employs a combination of the first and third oil supply modes. That is, when the speed requirement is low, oil is supplied by the first oil supply mode, and when the speed requirement is high, oil is supplied by the third oil supply mode. Switching between the first and third oil supply modes is controlled by the valve module, which efficiently reduces oil consumption in the energy reservoir 3 and improves the dynamic injection force of the injection hydraulic cylinder 1.

[0034] When a conventional pressure injection system performs a high-speed pressure injection phase, inertia causes the pressure injection speed of the injection hydraulic cylinder 1 to exceed the target speed when it reaches its maximum speed. This causes a rise in the speed curve, i.e., an overshoot. During the boost injection phase, the response of the servo valve in the oil passage lags behind the control cycle of the control system, resulting in an insufficient or excessive amount of oil discharged from the boost hydraulic cylinder 2, affecting the accuracy of the boost pressure. During the follow-up phase, after boosting is completed, the pressure in the rodless cavity of the injection hydraulic cylinder 1 becomes too high, resulting in insufficient oil in the rod-equipped cavity. As a result, when the mold is opened, the compressed oil in the rodless cavity pushes the hammer head forward, causing the hammer head to become uncontrollable and unable to follow.

[0035] In this embodiment, during the high-speed pressure injection stage and the follow-up stage, the valve module connects the rod-equipped cavity of the injection hydraulic cylinder 1 to the pump and tank of the oil passage, forming an A-shaped half-bridge structure. During the booster injection stage, the valve module connects the rod-equipped cavity of the booster hydraulic cylinder 2 to the pump and tank of the oil passage, forming an A-shaped half-bridge structure. The A-shaped half-bridge structure is a linked control structure consisting of two linked servo valves, which can simultaneously control the pressure injection speed and casting pressure of the hydraulic cylinder. This improves the speed control accuracy and pressure control accuracy of the pressure injection and significantly reduces costs.

[0036] According to this embodiment, there are multiple types of oil passage structures for the pressure injection system having the above-mentioned functions, but for ease of understanding, the following description will be given with reference to two specific embodiments. Of course, specific oil passage structures include, but are not limited to, the two embodiments described below. Here, solid lines shown in Figures 2 to 10 and Figures 14 to 22 indicate connected oil passages, dashed lines shown in Figures 2 to 10 and Figures 14 to 22 indicate connected oil passages, pumps are indicated by P, and tanks are indicated by T.

[0037] Example 1 As shown in Figures 1 to 10, the valve module includes on-off valves V4 to V6, on-off valves V8, V10, and V12, servo valves V7 and V9, and check valves V11 and V13. The output port of the pump is connected to the rod-equipped cavity of the injection hydraulic cylinder 1 by the check valve V11 and the servo valve V9, which are connected in series, to form a first oil passage. The output port of the pump is connected to the energy accumulator 3 by the on-off valve V12, to form a second oil passage. The output port of the pump is connected to the rod-less cavity of the injection hydraulic cylinder 1 by the check valve V11, the check valve V13, the on-off valve V8, and the on-off valve V5, which are connected in series, to form a third oil passage. The energy accumulator 3 is connected to the rod-less cavity of the injection hydraulic cylinder 1 by the on-off valve V4 and the on-off valve V5, which are connected in series, to form a fourth oil passage. The tank is connected to the rod-equipped cavity of the injection hydraulic cylinder 1 by the servo valve V7, forming a fifth oil passage. The energy accumulator 3 is connected to the rod-less cavity of the booster hydraulic cylinder 2 by the on-off valve V4, forming a sixth oil passage. The tank is connected to the rod-equipped cavity of the booster hydraulic cylinder 2 by the servo valve V7 and on-off valve V6, which are connected in series, forming a seventh oil passage. The output port of the pump is connected to the rod-equipped cavity of the booster hydraulic cylinder 2 by the check valve V11, servo valve V9, and on-off valve V6, which are connected in series, forming an eighth oil passage. The tank is connected to the rod-less cavity of the booster hydraulic cylinder 2 by the on-off valve V10, forming a ninth oil passage. The tank is connected to the rod-less cavity of the injection hydraulic cylinder 1 by the on-off valve V10 and on-off valve V5, which are connected in series, forming a tenth oil passage.

[0038] The shut-off valve V12 controls the pump so as to supply energy to the energy storage tank 3.

[0039] The oil in the energy accumulator 3 flows into the rodless cavity of the booster hydraulic cylinder 2 and the rodless cavity of the injection hydraulic cylinder 1 via the on-off valves V4 and V5, respectively. Specifically, the on-off valve V5 allows the oil in the energy accumulator 3 to flow into the rodless cavity of the injection hydraulic cylinder 1 during pressure injection. Compared to conventional oil passages with multiple on-off valves, this reduces throttling loss during the high-speed pressure injection stage, effectively improving the dynamic injection force of the injection hydraulic cylinder 1. Furthermore, closing the on-off valve V5 during the booster injection stage prevents high-pressure oil from leaking out, and also allows the oil to be discharged from the rodless cavity of the injection hydraulic cylinder 1 during the hammer return stage.

[0040] The on-off valve V4 is directly connected to the rodless cavity of the booster hydraulic cylinder 2. During the booster injection stage, the oil in the energy accumulator 3 flows into the rodless cavity of the booster hydraulic cylinder 2 through the on-off valve V4. During the low-speed pressure injection stage, the on-off valve V8 connected to the on-off valve V5 allows the oil in the rod-equipped cavity of the injection hydraulic cylinder 1 to pass through the servo valve V9, and then passes through the on-off valve V8 together with the oil from the check valves V11 and V13, forming a differential connection.

[0041] The servo valve V9 and the on-off valve V5 are connected to the rodless cavity of the injection hydraulic cylinder 1. During the low-speed pressure injection phase, the servo valve V9 controls the oil return speed of the rodless cavity of the injection hydraulic cylinder 1. During the high-speed pressure injection phase, the servo valves V9 and V7 are connected to the rod-equipped cavity of the injection hydraulic cylinder 1 in the oil line, forming an A-shaped half-bridge structure to control the high-speed pressure injection speed. During the boost injection phase, when the on-off valve V6 is opened, the servo valves V9 and V7 are connected to the rod-equipped cavity of the booster hydraulic cylinder 2 in the oil line, forming an A-shaped half-bridge structure to control the boost pressure of the booster hydraulic cylinder 2. Specifically, the on-off valve V6 is connected to the rod-equipped cavity of the booster hydraulic cylinder 2 and controls whether or not to boost the pressure.

[0042] The on-off valves V10 and V5 respectively connect the rodless cavity of the booster hydraulic cylinder 2 and the rodless cavity of the injection hydraulic cylinder 1 to the tank, allowing the oil in the rodless cavity of the booster hydraulic cylinder 2 and the rodless cavity of the injection hydraulic cylinder 1 to return to the tank during the hammer return phase.

[0043] The check valve V11 prevents the pressure in the oil passage downstream of the check valve from becoming too high and causing a backflow of oil.

[0044] The pressure injection process of the pressure injection system of this embodiment is divided into the following stages: energy storage stage, low-speed pressure injection stage, high-speed pressure injection stage, braking stage, boost delay stage, boost injection stage, decompression stage, follow-up stage, and hammer return stage. For ease of understanding, the specific operation of each stage will be described in detail.

[0045] As shown in Fig. 2, in the energy accumulation stage, the control system of the pressure injection system can control the servo valve V9 and the shut-off valve V12 to be turned on. Then, with the first oil line and the second oil line in a connected state, the started pump supplies oil to the rod-equipped cavity of the injection hydraulic cylinder 1 through the connected first oil line, and also supplies oil to the energy accumulator 3 through the connected second oil line. By supplying oil to the rod-equipped cavity of the injection hydraulic cylinder 1 to increase the pressure before the low-speed pressure injection stage, the starting shock in the low-speed pressure injection stage can be reduced or avoided.

[0046] The low-speed pressure injection stage includes a mode of oil passage sole supply by the pump and a mode of oil passage joint supply by the pump and the energy reservoir 3 .

[0047] As shown in Figure 3, in the pump-operated oil line independent oil supply mode, after the energy storage stage is completed, the on-off valve V12 is closed, the servo valve V9 is kept open, and the on-off valves V5 and V8 are opened. Then, with the first and third oil lines in a connected state, the first and third oil lines are connected at the output port of the check valve V11 to form a differential circuit. That is, the pump supplies oil to the rodless cavity of the injection hydraulic cylinder 1 through the connected third oil line, and the pressurized oil in the rod-equipped cavity of the injection hydraulic cylinder 1 flows into the rodless cavity of the injection hydraulic cylinder 1 along the servo valve 9, via the check valve V13 and the on-off valves V5 and V8.

[0048] As shown in Figure 4, in the common oil supply mode of the oil passages by the energy accumulator 3, in addition to the individual oil supply to the pump, the on-off valves V4 and V12 are opened. Then, with the first oil passage, the second oil passage, the third oil passage, and the fourth oil passage all in a connected state, the first oil passage and the third oil passage are connected at the output port of the check valve V11 to form a differential circuit. That is, in addition to the individual oil supply to the pump, the energy accumulator 3 supplies oil to the rodless cavity of the injection hydraulic cylinder 1 through the connected fourth oil passage, and the pump replenishes oil to the energy accumulator 3 through the connected second oil passage.

[0049] By adopting differential control in the low-speed pressure injection stage, stability of low-speed pressure injection is ensured, and the servo valve V9 controls the flow rate of the rod-equipped cavity of the injection hydraulic cylinder 1, thereby controlling the speed of low-speed pressure injection. Because the pressure difference between before the servo valve V9 and after the servo valve V9 during differential control is smaller than the pressure difference during conventional single outlet control, the pressure increase of the servo valve V9 can be reduced, improving the control accuracy of the injection hydraulic cylinder 1. In addition, because pressure is increased in the rod-equipped cavity of the injection hydraulic cylinder 1 during the energy accumulation stage before the start of low-speed pressure injection, the amount of oil compressed in the rod-equipped cavity of the injection hydraulic cylinder 1 is reduced when low-speed pressure injection is started, preventing or reducing startup shock.

[0050] During the actual pressure injection stage, the low-speed pressure injection occupies a large portion of the stroke. In this embodiment, the differential circuit allows the injection hydraulic cylinder 1 to reduce the flow rate required for low-speed pressure injection compared to the flow rate required in conventional non-differential control, and the joint oil supply between the pump and the energy storage device 3 can further reduce the amount of oil supplied by the energy storage device 3, allowing the volume of the energy storage device 3 to be appropriately reduced.

[0051] As shown in Figure 5, during the high-speed pressure injection phase and the braking phase, servo valve V7 is opened, shut-off valves V8 and V12 are closed, and shut-off valves V4 and V5 are kept open. The first, fourth, and fifth oil lines are all open, and the first and fifth oil lines are connected to the rod-equipped cavity of the injection hydraulic cylinder 1. The energy accumulator 3 supplies oil to the rodless cavity of the injection hydraulic cylinder 1 through the open fourth oil line, and pressure oil in the rod-equipped cavity of the injection hydraulic cylinder 1 is returned to the tank via the fifth oil line. At the same time, the pump supplies oil to the first oil line, and the first and fifth oil lines form an A-type half-bridge structure when connected. This allows the pressure injection speed of the injection hydraulic cylinder 1 to be adjusted by controlling the opening of servo valves V7 and V9.

[0052] During the high-speed pressure injection phase, the servo valve V7 is opened widely and the servo valve V9 is opened narrowly, allowing the pressurized oil in the rod-equipped cavity of the injection hydraulic cylinder 1 to quickly return to the tank, achieving high-speed pressure injection. During the high-speed pressure injection phase, the first oil passage is opened, forming an A-type half-bridge structure. Then, by controlling the opening of the servo valve V9, the flow rate in the rod-equipped cavity of the injection hydraulic cylinder 1 can be quickly adjusted, achieving high-precision speed control, thereby reducing or avoiding excessive speed.

[0053] During the braking phase, servo valve V7 has a small opening and servo valve V9 has a large opening, which increases the pressure in the rod-containing cavity of the injection hydraulic cylinder 1, thereby achieving active braking. The pump oil supply uses an A-type half-bridge structure to speed up the rise of pressure in the rod-containing cavity of the injection hydraulic cylinder 1, allowing for faster deceleration and active braking.

[0054] As shown in Figure 6, during the pressure boost delay phase, i.e., the preparation phase before the boost injection phase begins, after the braking phase is completed, the on-off valve V5 is closed and the servo valves V7 and V9 are adjusted to their predetermined positions. With the sixth oil line open, the energy accumulator 3 supplies oil to the rodless cavity of the boost hydraulic cylinder 2 through the open sixth oil line. This reduces the period of constant casting pressure during the preparation operation for boosting pressure after the settling phase is completed. Furthermore, compared to the conventional passive closing system, this embodiment actively opens and closes the on-off valve, thereby creating pressure in the rodless cavity of the boost hydraulic cylinder 2 and improving the pressure build-up speed during pressure boosting.

[0055] The boost-up delay phase can be considered a step following the braking phase. Conventional pressure injection systems perform the boost-up injection phase directly after completing the braking phase, which causes pressure oscillations as shown by the curve in Figure 11. In this embodiment, before the boost-up injection phase, i.e., just before the braking phase is about to end, the on-off valve V5 is closed to enter the boost-up delay phase. The fast closing speed of the on-off valve V5 significantly improves the braking speed, thereby reducing the oscillations of the casting pressure, as shown in Figure 12.

[0056] As shown in Figure 7, when the shut-off valve V6 is opened during the boost injection stage based on the boost delay stage, the sixth, seventh, and eighth oil lines are all connected, and the seventh and eighth oil lines are connected between the shut-off valve V6 and the servo valve V9. The energy accumulator 3 supplies oil to the rodless cavity of the boost injection cylinder 2 through the connected sixth oil line, and the pressurized oil in the rod-equipped cavity of the boost injection cylinder 2 is returned to the tank through the connected seventh oil line. Since the pump can supply oil to the connected eighth oil line, the eighth and seventh oil lines are connected at the connected position, forming an A-type half-bridge structure, and the boost pressure of the boost injection cylinder 2 can be adjusted by controlling the opening of the servo valves V9 and V7.

[0057] Because the servo valves V7 and V9 are in a conducting state, the first oil line and the fifth oil line are in a conducting state. During the boosted injection stage, the rod-equipped cavity of the injection hydraulic cylinder 1 can be supplied with or drained from the rod-equipped cavity according to the pressure demand. That is, when the pressure in the rod-equipped cavity of the injection hydraulic cylinder 1 is low, oil can be supplied to the rod-equipped cavity of the injection hydraulic cylinder 1 through the first oil line, and when the pressure in the rod-equipped cavity of the injection hydraulic cylinder 1 is high, oil can be drained from the rod-equipped cavity of the injection hydraulic cylinder 1 to reduce its pressure through the fifth oil line. This avoids the loss of tracking control that occurs with conventional oil lines when the pressure in the rodless cavity of the injection hydraulic cylinder 1 is high at the end of boosted injection and there is no oil in the rod-equipped cavity.

[0058] The method for accurately controlling the boost pressure using the A-type half-bridge structure is as follows. Specifically, during the delay phase before boosting begins, the servo valve V7 is opened to a predetermined aperture, and the servo valve V9 is opened to a predetermined aperture to quickly increase the pressure during the boosted injection phase. When the pressure in the rodless cavity of the injection hydraulic cylinder 1 reaches a certain proportion of the predetermined value of the first level, the aperture of the servo valve V7 is adjusted to a small value. This adjustment of the aperture of the servo valve V9 changes the flow rate through the servo valve V9. This adjustment causes a pressure drop when the flow rate through the servo valve V9 and the flow rate from the rod-equipped cavity of the booster hydraulic cylinder 2 flow into the servo valve V7. This pressure drop is the pressure in the rod-equipped cavity of the booster hydraulic cylinder 2, and the boost pressure can be adjusted by controlling the pressure in the rod-equipped cavity of the booster hydraulic cylinder 2. Therefore, the flow rate can be controlled by adjusting the aperture of the servo valve V9, and the boost pressure can be controlled by controlling the pressure drop of the servo valve V7. According to this control method, the boost pressure can be adjusted with higher accuracy, and the boost pressure can be reduced when the boost pressure exceeds the limit.

[0059] In the boost injection stage, when the on-off valve V12 is opened, the pump supplies oil to the energy accumulator 3 through the opened second oil line. By supplying oil to the energy accumulator 3, the pressure in the energy accumulator 3 can be increased, thereby ensuring that the energy accumulator 3 has sufficient pressure in the subsequent follow-up stage. At the same time, the injection hydraulic cylinder 1 and the boost hydraulic cylinder 2 share the single energy accumulator 3. In both the boost injection stage and the low-speed pressure injection stage, by supplying oil to the energy accumulator 3, the volume of the energy accumulator 3 can be made smaller, thereby reducing costs.

[0060] As shown in Fig. 6, when the on-off valve V12 is closed in the pressure reducing stage, the pump stops supplying oil to the energy accumulator 3 and stops supplying oil from the energy accumulator 3 to the rodless cavity of the booster hydraulic cylinder 2. Then, by increasing the opening of the servo valve V9 and decreasing the opening of the servo valve V7, the pump supplies oil to the rod-equipped cavity of the booster hydraulic cylinder 2 through the opened eighth oil line, and the booster hydraulic cylinder 2 returns and returns the pressurized oil in the rodless cavity to the energy accumulator 3 along the opened sixth oil line.

[0061] In the conventional pressure injection system, after the boost injection stage is completed, the hammer head needs to push the product out of the fixed mold. After the boost injection stage is completed, the pressure in the rodless cavity of the injection hydraulic cylinder 1 is too high and there is not enough oil in the rod-equipped cavity of the injection hydraulic cylinder 1. As a result, when the mold is opened, the compressed oil in the rodless cavity of the injection hydraulic cylinder 1 pushes the hammer head forward, causing the hammer head to become uncontrollable and unable to follow.

[0062] In this embodiment, by increasing the opening of the servo valve V9, the pressure in the rod-equipped cavity of the boosting hydraulic cylinder 2 can be increased, the boosting hydraulic cylinder 2 returns, and the pressure oil in the rodless cavity of the boosting hydraulic cylinder 2 is returned to the energy storage tank 3, which can actively reduce the pressure in the rodless cavity of the injection hydraulic cylinder 1, and the balance of forces can reduce the pressure in the rod-equipped cavity of the injection hydraulic cylinder 1. Of course, during the pressure reduction stage, the pressure in the rodless cavity of the injection hydraulic cylinder 1 is pushed out to be the same as the system pressure, which can ensure that the pressure in the rodless cavity of the injection hydraulic cylinder 1 is not too high and causes it to be unable to follow.

[0063] As shown in Figure 9, in the follow-up stage, when the on-off valve V6 is closed and the on-off valves V5 and V12 are opened, the second, third, fourth, and fifth oil lines are connected, and the first and fifth oil lines are connected at the connection position of the rod-equipped cavity of the injection hydraulic cylinder 1. The pump and the energy accumulator 3 supply oil to the rodless cavity of the injection hydraulic cylinder 1 through the connected third and fourth oil lines, respectively. The pump supplies oil to the energy accumulator 3 through the connected second oil line, and the pressure of the rod-equipped cavity of the injection hydraulic cylinder 1 is returned to the tank along the fifth oil line. The pump supplies oil to the connected first oil line, so that the first and fifth oil lines form an A-type half-bridge structure at the connection position, and the pressure and injection speed of the injection hydraulic cylinder 1 can be adjusted by controlling the opening of the servo valves V7 and V9.

[0064] Specifically, after the depressurization stage is completed, the servo valve V7 is opened larger and the servo valve V9 is opened smaller, thereby controlling the follow-up speed of the hammer head. The pump refueling to the energy reservoir 3 can increase the follow-up pressure.

[0065] As shown in Figure 10, in the hammer return stage, when the on-off valves V4, V8, V12 and servo valve V7 are closed and the on-off valve V10 is opened, the first, eighth, ninth and tenth oil lines are connected. The pump supplies oil to the rod-equipped cavity of the injection hydraulic cylinder 1 and the rod-equipped cavity of the booster hydraulic cylinder 2 through the connected first and eighth oil lines, respectively, and returns pressurized oil to the tank from the rod-less cavity of the injection hydraulic cylinder 1 and the rod-less cavity of the booster hydraulic cylinder 2 through the connected tenth and ninth oil lines.

[0066] By supplying oil to the rod-containing cavity of the injection hydraulic cylinder 1 and the rod-containing cavity of the booster hydraulic cylinder 2 during the hammer return phase, the risk of wear on the rod-containing cavity during the hammer return phase that occurs in conventional pressure injection systems can be avoided.

[0067] In this embodiment, servo valve V9 is used in all of the low-speed pressure injection stage, high-speed pressure injection stage, boost injection stage, follow-up stage, and hammer return stage. On the other hand, servo valves V7 and V9 are used in all of the high-speed pressure injection stage, boost injection stage, and follow-up stage. In other words, by using only two servo valves, the pressure injection system can effectively reduce the cost of the pressure injection system.

[0068] Example 2 The second embodiment differs from the first embodiment in the following respects. In the second embodiment, the servo valves V14 and V15 are added, and the on-off valve V6 is eliminated. Specifically, as shown in FIGS. 13 to 22, the valve module according to the second embodiment includes on-off valves V4, V5, V8, V10, and V12, servo valves V7, V9, V14, and V15, and check valves V11 and V13. The output port of the pump is connected to the rod-equipped cavity of the injection hydraulic cylinder 1 by the check valve V11 and the servo valve V9, which are connected in series, to form a first oil passage. The output port of the pump is connected to the energy accumulator 3 by the on-off valve V12, to form a second oil passage. The output port of the pump is connected to the rod-less cavity of the injection hydraulic cylinder 1 by the check valve V11, the check valve V13, the on-off valve V8, and the on-off valve V5, which are connected in series, to form a third oil passage. The energy accumulator 3 is connected to the rod-less cavity of the injection hydraulic cylinder 1 by on-off valves V4 and V5 connected in series, forming a fourth oil passage. The tank is connected to the rod-containing cavity of the injection hydraulic cylinder 1 by servo valve V7, forming a fifth oil passage. The energy accumulator 3 is connected to the rod-less cavity of the booster hydraulic cylinder 2 by on-off valve V4, forming a sixth oil passage. The tank is connected to the rod-less cavity of the booster hydraulic cylinder 2 by on-off valve V10, forming a ninth oil passage. The tank is connected to the rod-less cavity of the injection hydraulic cylinder 1 by on-off valves V10 and V5, connected in series, forming a tenth oil passage. The energy accumulator 3 is connected to the rod-containing cavity of the booster hydraulic cylinder 2 by servo valve V14, forming an eleventh oil passage. The pump is connected to the rod-containing cavity of the booster hydraulic cylinder 2 by servo valve V15, forming a twelfth oil passage. The pump is connected to the rod-containing cavity of the booster hydraulic cylinder 2 by an on-off valve V12 and a servo valve V14, which are connected in series, to form a thirteenth oil passage.

[0069] In this embodiment, the pressure injection process of the pressure injection system is divided into an energy storage stage, a low-speed pressure injection stage, a high-speed pressure injection stage, a braking stage, a pressure boost delay stage, a pressure boost injection stage, a decompression stage, a follow-up stage and a hammer return stage. For ease of understanding, the specific operation of each stage will be described in detail.

[0070] As shown in Figure 14, in the energy storage stage, the equivalent oil path structure of this embodiment is similar to the oil path structure shown in Figure 2 of Example 1, so detailed explanations thereof will be omitted here, and for details, please refer to the energy storage stage of Example 1.

[0071] As shown in Figures 15 and 16, in the low-speed pressure injection stage, the equivalent oil passage structure of this embodiment is similar to the oil passage structure shown in Figures 3 and 4 of Example 1, so detailed explanations thereof will be omitted here, and for details, please refer to the low-speed pressure injection stage of Example 1.

[0072] As shown in Figure 17, in the high-speed pressure injection stage and the braking stage, the equivalent oil passage structure of this embodiment is similar to the oil passage structure shown in Figure 5 of Example 1, so detailed explanations thereof will be omitted here, and for details, please refer to the high-speed pressure injection stage and the braking stage of Example 1.

[0073] 18, in the pressure boost delay stage, i.e., the preparation stage before the start of the pressure boost injection stage, after the braking stage is completed, if the on-off valve V5 and the servo valve V9 are closed and the on-off valve V12 is opened, the second oil line, the fifth oil line, and the sixth oil line are all opened. By performing the pressure boost preparation operation after the braking stage is completed, the period during which the casting pressure remains unchanged can be reduced.

[0074] As shown in Figure 19, in the boost injection stage, when the servo valves V14 and V15 are opened based on the boost delay stage, the second oil line, fifth oil line, sixth oil line, eleventh oil line and twelfth oil line are all opened, and the eleventh oil line and the twelfth oil line are connected in the rod-equipped cavity of the boost hydraulic cylinder 2. The energy accumulator 3 supplies oil to the rodless cavity of the boost hydraulic cylinder 2 through the opened sixth oil line, and the pressurized oil in the rod-equipped cavity of the injection hydraulic cylinder 1 is returned to the tank through the opened fifth oil line. At the same time, the energy accumulator 3 supplies oil to the connected 11th oil line, and the rod-equipped cavity of the booster hydraulic cylinder 2 discharges oil through the connected 12th oil line, so that the 11th oil line and the 12th oil line form an A-type half-bridge structure at the connected position, and the booster pressure of the booster hydraulic cylinder 2 can be adjusted by controlling the opening of the servo valves V14 and V15.

[0075] The method for accurately controlling the boost pressure using the A-type half-bridge structure is as follows. The servo valve V7 is opened to a predetermined aperture, and the servo valves V14 and V15 are also opened to predetermined apertures. When the pressure in the rodless cavity of the injection hydraulic cylinder 1 reaches a certain proportionality with the first level predetermined value, the aperture of the servo valve V15 is adjusted to a smaller value. This adjustment of the aperture of the servo valve V14 changes the flow rate through the servo valve V14. This causes a pressure drop when the flow rate through the servo valve V14 and the flow rate from the rod-equipped cavity of the booster hydraulic cylinder 2 flow into the servo valve V15. This pressure drop is the pressure in the rod-equipped cavity of the booster hydraulic cylinder 2, and the boost pressure can be adjusted by controlling the pressure in the rod-equipped cavity of the booster hydraulic cylinder 2. Therefore, the flow rate can be controlled by adjusting the aperture of the servo valve V14, and the boost pressure can be controlled by controlling the pressure drop of the servo valve V15. According to this control method, the boost pressure can be adjusted with higher accuracy, and the boost pressure can be reduced when the boost pressure exceeds the limit.

[0076] In the boost injection stage, the on-off valve V12 is opened to open the second oil line, and the pump supplies oil to the energy accumulator 3 through the opened second oil line. This ensures that the energy accumulator 3 has sufficient pressure in the boost injection stage.

[0077] As shown in Figure 20, in the depressurization stage, when the on-off valve V12 is closed after the boosted injection stage is completed and the servo valves V7 and V15 are also closed, the second, fifth and 12 oil lines are blocked and the energy accumulator 3 stops supplying oil to the rodless cavity of the boosted hydraulic cylinder 2 through the sixth oil line, but the sixth and 11 oil lines remain open. The energy accumulator 3 supplies oil to the rod-equipped cavity of the boosted hydraulic cylinder 2 through the open 11 oil line, and the boosted hydraulic cylinder 2 returns and returns the pressure oil in the rodless cavity to the energy accumulator 3 along the open sixth oil line. At this time, the pressure in the rodless cavity of the injection hydraulic cylinder 1 is pushed out to be the same as the system pressure, ensuring that the pressure in the rodless cavity of the injection hydraulic cylinder 1 is not too high, causing the injection hydraulic cylinder 1 to be unable to follow the pressure.

[0078] As shown in Figure 21, in the follow-up stage, the equivalent oil path structure of this embodiment is similar to the oil path structure shown in Figure 9 of Example 1, so detailed explanations will be omitted here and please refer to the follow-up stage of Example 1 for details.

[0079] As shown in Figure 22, during the hammer return phase, after the follow-up phase is completed, the on-off valves V4 and V8 and servo valve V7 are closed and servo valve V14 is opened, so that the first, second, ninth, tenth, and thirteenth oil lines are connected. The pump supplies oil to the rod-equipped cavity of the injection hydraulic cylinder 1 and the rod-equipped cavity of the booster hydraulic cylinder 2 via the connected first and thirteenth oil lines, respectively, and the pump replenishes oil to the energy accumulator 3 via the connected second oil line, thereby shortening the time for the accumulation phase in the next pressure injection process. At the same time, the rod-less cavity of the injection hydraulic cylinder 1 and the rod-less cavity of the booster hydraulic cylinder 2 return pressurized oil to the tank via the connected ninth and tenth oil lines, respectively.

[0080] The above is the basic principle, main features and advantages of the present invention. Those skilled in the art will understand that the present invention is not limited to the above-described embodiments, and that the above-described embodiments and the matters described in the specification are merely the principles of the present invention, and that modifications to the embodiments are included within the scope of the claims. [Explanation of symbols]

[0081] 1 Injection hydraulic cylinder 2. Booster hydraulic cylinder 3 Energy Storage

Claims

1. 1. A pressure injection system of a casting apparatus, comprising: The hydraulic cylinder includes an energy storage device, an injection hydraulic cylinder, a booster hydraulic cylinder, and a valve module, which are connected by an oil passage; In the low-speed pressure injection stage of the injection hydraulic cylinder, the valve module is used to switch between a pump-only oil supply mode and a pump-and-energy storage-shared oil supply mode; In the high-speed pressure injection stage, the braking stage and the follow-up stage, the valve module connects the rod-containing cavity of the injection hydraulic cylinder to the pump and the tank of the oil passage so as to form an A-type half-bridge structure; In the boost injection stage, the valve module connects the rod-containing cavity of the boost hydraulic cylinder to the pump and tank of the oil passage, so as to form an A-type half-bridge structure; The valve module includes an on-off valve V4, an on-off valve V5, an on-off valve V8, an on-off valve V12, a servo valve V7, a servo valve V9, a check valve V11, and a check valve V13, The output port of the pump is connected to the rod-containing cavity of the injection hydraulic cylinder by a check valve V11 and a servo valve V9 connected in series, forming a first oil passage. The output port of the pump is connected to the energy storage device by an on-off valve V12 to form a second oil passage; The output port of the pump is connected to the rodless cavity of the injection hydraulic cylinder by a check valve V11, a check valve V13, an on-off valve V8 and an on-off valve V5 connected in series in this order, thereby forming a third oil passage; The energy accumulator is connected to the rodless cavity of the injection hydraulic cylinder by an on-off valve V4 and an on-off valve V5 connected in series to form a fourth oil passage; The tank is connected to the rod-equipped cavity of the injection hydraulic cylinder by a servo valve V7, forming a fifth oil passage; The energy accumulator is connected to the rodless cavity of the boosting hydraulic cylinder by an on-off valve V4, forming a sixth oil passage; The output port of the pump is connected to the rod-equipped cavity of the booster hydraulic cylinder by a check valve V11, a servo valve V9, and an on-off valve V6, which are connected in series in this order, to form an eighth oil passage; In the high-speed pressure injection stage and the braking stage, the energy accumulator supplies oil to the rodless cavity of the injection hydraulic cylinder through the fourth oil line that is connected, and the pressure oil in the rod-equipped cavity of the injection hydraulic cylinder is returned to the tank along the fifth oil line that is connected, the first oil line and the fifth oil line are connected to form an A-type half-bridge structure, and the pressure injection speed of the injection hydraulic cylinder is adjusted by controlling the opening of the servo valves V7 and V9, In the follow-up stage, the pump and the energy accumulator supply oil to the rodless cavity of the injection hydraulic cylinder through the connected third oil line and the connected fourth oil line, respectively, the pump supplies oil to the energy accumulator through the connected second oil line, and the pressure oil in the rod-equipped cavity of the injection hydraulic cylinder is returned to the tank along the connected fifth oil line, the first oil line and the fifth oil line are connected to form an A-type half-bridge structure, and the pressure injection speed of the injection hydraulic cylinder is adjusted by controlling the opening of the servo valves V7 and V9, The valve module includes an on-off valve V6, The tank is connected to the rod-equipped cavity of the boosting hydraulic cylinder by a servo valve V7 and an on-off valve V6 connected in series, forming a seventh oil passage. In the boost injection stage, the energy accumulator supplies oil to the rodless cavity of the boosting hydraulic cylinder through the sixth oil line that is connected, and the pressure oil in the rod-equipped cavity of the boosting hydraulic cylinder and the pressure oil in the rod-equipped cavity of the injection hydraulic cylinder are returned to the tank along the seventh oil line and the fifth oil line that are connected, respectively, and the eighth oil line and the seventh oil line are connected to form an A-type half-bridge structure, and the boost pressure of the boosting hydraulic cylinder is adjusted by controlling the opening of the servo valves V7 and V9, Alternatively, the valve module includes a servo valve V14 and a servo valve V15, The energy accumulator is connected to the rod-containing cavity of the boosting hydraulic cylinder by a servo valve V14, forming an eleventh oil passage; The tank is connected to the rod-equipped cavity of the booster hydraulic cylinder by a servo valve V15, forming a 12th oil passage; In the boost injection stage, the energy accumulator supplies oil to the rodless cavity of the boost hydraulic cylinder through the sixth oil line that is connected, and the pressure oil in the rod-equipped cavity of the injection hydraulic cylinder is returned to the tank along the fifth oil line that is connected, the eleventh oil line and the twelfth oil line are connected to form an A-type half-bridge structure, and the boost pressure of the boost hydraulic cylinder is adjusted by controlling the opening of the servo valves V14 and V15. A pressure injection system for a casting machine.

2. In a sole oil supply mode by the pump during low-speed pressure injection, the pump supplies oil to the rodless cavity of the injection hydraulic cylinder through the opened third oil passage, and a differential circuit is formed by the first oil passage and the third oil passage.

2. The pressure injection system of claim 1.

3. In a joint oil supply mode by the pump and the energy accumulator during low-speed pressure injection, in addition to the sole oil supply by the pump, the energy accumulator supplies oil to the rod-less cavity of the injection hydraulic cylinder through the fourth oil passage that is opened.

3. The pressure injection system of claim 2.

4. When depressurizing after the completion of the boosting pressure injection stage, the supply of oil from the energy accumulator to the rodless cavity of the boosting hydraulic cylinder is stopped, and the opening of the servo valve V9 is increased and the opening of the servo valve V7 is decreased, so that the pump supplies oil to the rod-equipped cavity of the boosting hydraulic cylinder through the opened eighth oil passage, and the boosting hydraulic cylinder returns, and the pressure oil in the rodless cavity is returned to the energy accumulator along the opened sixth oil passage.

2. The pressure injection system of claim 1.

5. The valve module includes an on-off valve V10, The tank is connected to the rodless cavity of the booster hydraulic cylinder by the on-off valve V10, forming a ninth oil passage; The tank is connected to the rodless cavity of the injection hydraulic cylinder by an on-off valve V10 and an on-off valve V5 connected in series, forming a tenth oil passage; When the hammer return step is performed after the completion of the following step, the pump supplies oil to the rod-equipped cavity of the injection hydraulic cylinder and the rod-equipped cavity of the boosting hydraulic cylinder through the first oil passage and the eighth oil passage that are connected, respectively, and the rod-less cavity of the injection hydraulic cylinder and the rod-less cavity of the boosting hydraulic cylinder return pressurized oil to the tank through the tenth oil passage and the ninth oil passage that are connected, respectively.

2. The pressure injection system of claim 1.

6. When the pressure is reduced after the boosted injection stage is completed, the fifth oil passage and the twelfth oil passage are blocked, and the sixth oil passage and the eleventh oil passage are connected, but the supply of oil from the energy accumulator to the sixth oil passage is stopped, so that the energy accumulator supplies oil to the rod-equipped cavity of the boosted hydraulic cylinder through the eleventh oil passage, and the boosted hydraulic cylinder returns, and the pressure oil in the rod-less cavity is returned to the energy accumulator along the sixth oil passage through which it is connected.

2. The pressure injection system of claim 1.

7. The valve module includes an on-off valve V10, The tank is connected to the rodless cavity of the booster hydraulic cylinder by the on-off valve V10, forming a ninth oil passage; The tank is connected to the rodless cavity of the injection hydraulic cylinder by an on-off valve V10 and an on-off valve V5 connected in series, forming a tenth oil passage; The pump is connected to the rod-equipped cavity of the boosting hydraulic cylinder by an on-off valve V12 and a servo valve V14 connected in series, forming a 13th oil passage; When the hammer return step is performed after the completion of the following step, the pump supplies oil to the rod-equipped cavity of the injection hydraulic cylinder and the rod-equipped cavity of the boosting hydraulic cylinder through the first oil passage and the thirteenth oil passage that are connected, respectively, and the rod-less cavity of the injection hydraulic cylinder and the rod-less cavity of the boosting hydraulic cylinder return pressurized oil to the tank through the tenth oil passage and the ninth oil passage that are connected, respectively.

7. The pressure injection system of claim 6.

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