Multiple clamping hydraulic oil circuit structure of injection molding machine and multiple clamping method thereof

Abstract

The multiple clamping hydraulic oil circuit structure of the injection molding machine of the present invention comprises an oil tank, a first oil pump and a main oil circuit oil pump, a servo motor, and a clamping high-pressure oil cylinder; a first control valve and a second control valve are provided between the connecting oil circuit of the oil pump and the clamping high-pressure oil cylinder, a third control valve is provided between the connecting oil circuit of the main oil circuit oil pump and the clamping high-pressure oil cylinder, and the main oil circuit oil pump is connected with the third control valve, the first control valve, the second control valve and the clamping high-pressure oil cylinder in sequence to form a second oil circuit channel; a first oil return channel is also provided between the second control valve and the connecting oil circuit of the clamping high-pressure oil cylinder, the first oil return channel comprises a fourth control valve and a regulating valve, and the first oil return channel is connected with the fourth control valve, the regulating valve and the oil tank in sequence. Through the setting of multiple oil circuit channels and the control of a series of hydraulic oil valves combined with multiple clamping steps, the pressure oil can be effectively delivered to each clamping oil cylinder, thereby controlling the clamping force.

Description

Technical Field

[0001] The invention belongs to the field of hydraulic oil circuit structures of injection molding machines, and in particular relates to a multiple-mode clamping hydraulic oil circuit structure of an injection molding machine and a multiple-mode clamping method thereof. Background Art

[0002] In hydraulic injection molding machines, the mold-shifting cylinder pulls the mold plate to make the two halves of the mold stick together, and then the movable mold plate is fixed to four tie rods through a mechanical device. Next, the high-pressure hydraulic oil is controlled by the hydraulic system to seal the clamping cavity, thereby generating a certain clamping force; then the injection mechanism injects the raw material into the mold, and then continues to maintain a certain pressure for a period of time until the product is cooled and formed.

[0003] However, the traditional working mode of injection molding machines has the following three disadvantages: 1) The process of hydraulic oil compression in the clamping cavity to generate clamping force is divided into two stages. First, in the low-pressure area, multiple pumps are involved in the work to quickly replenish the hydraulic oil in the clamping cavity; second, in the high-pressure area, a large-displacement high-pressure pump is used to generate clamping high pressure; but due to the large inertia of the large-displacement pump, the pressure cannot be increased smoothly at high pressure, and the pressure overshoot reaches more than 10 bar, which has a great impact on the life of the clamping mechanism; 2) During the entire injection and pressure holding process, the clamping force generated by the clamping mechanism does not change. At the beginning of the injection, the injection mold will have a large deformation, and the exhaust channel will be squeezed and narrowed, which will affect the exhaust in the cavity. If the air in the cavity cannot be discharged in time, it will gradually penetrate into the product during the injection process, which will affect the mechanical properties of the product; 3) Injection generally adopts a point-in-place pressure holding mode. The stress at the inlet will be very high, and the stress around it will be very low, which is prone to warping. This problem is more prominent for flat plastic parts. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the present invention aims to provide a multiple clamping hydraulic oil circuit structure for an injection molding machine, comprising an oil tank for storing hydraulic oil, a first oil pump and a main oil circuit oil pump for conveying hydraulic oil, a servo motor for providing power to the oil pump, and a clamping high-pressure oil cylinder connected to the oil pump and used to drive the mold to open and close the mold; a first control valve for controlling the on and off of the first oil pump and a second control valve for controlling the conduction of hydraulic oil to the clamping high-pressure oil cylinder are provided between the connecting oil circuit between the oil pump and the clamping high-pressure oil cylinder, and the oil pump is connected to the first control valve, the second control valve and the clamping high-pressure oil cylinder in sequence The first oil channel is formed by connecting the main oil pump and the clamping high-pressure oil cylinder. The third control valve for controlling the on-off of the main oil pump is provided between the main oil pump and the connecting oil circuit of the clamping high-pressure oil cylinder. The main oil pump is connected with the third control valve, the first control valve, the second control valve and the clamping high-pressure oil cylinder in sequence to form the second oil channel. The first oil return channel is also provided between the second control valve and the connecting oil circuit of the clamping high-pressure oil cylinder. The first oil return channel includes a fourth control valve for controlling the on-off of the first oil return channel and a regulating valve for controlling the pressure of the first oil return channel. The first oil return channel is connected with the fourth control valve, the regulating valve and the oil tank in sequence. Through the setting of multiple oil channels and the control of a series of hydraulic oil valves, the pressure oil can be effectively delivered to each clamping oil cylinder, thereby controlling the clamping force. The pressure shock of high-pressure clamping is eliminated, the service life of the parts of the clamping mechanism is extended, and the air marks and shrinkage holes inside the product are eliminated, and the internal stress after molding is reduced, and no warping occurs. Improve the mechanical properties and quality of the product.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] The multiple clamping hydraulic oil circuit structure of the injection molding machine includes an oil tank for storing hydraulic oil, a first oil pump and a main oil circuit oil pump for conveying hydraulic oil, a servo motor for providing power to the first oil pump and the main oil circuit oil pump, and a clamping high-pressure oil cylinder connected to the oil pump and used to drive the mold to open and close;

[0007] A first control valve for controlling the on / off of the first oil pump and a second control valve for controlling the hydraulic oil to pass through the mold-locking high-pressure oil cylinder are provided between the connecting oil circuit of the oil pump and the mold-locking high-pressure oil cylinder. The oil pump is connected with the first control valve, the second control valve and the mold-locking high-pressure oil cylinder in sequence to form a first oil circuit channel;

[0008] A third control valve for controlling the on / off of the main oil pump is provided between the connecting oil circuit of the main oil pump and the mold locking high pressure oil cylinder. The main oil pump is connected with the third control valve, the first control valve, the second control valve and the mold locking high pressure oil cylinder in sequence to form a second oil circuit channel.

[0009] A first oil return channel is also provided between the second control valve and the connecting oil circuit of the locking high-pressure oil cylinder. The first oil return channel includes a fourth control valve for controlling the on-off of the first oil return channel and a regulating valve for controlling the pressure of the first oil return channel. The first oil return channel is connected to the fourth control valve, the regulating valve and the oil tank in sequence.

[0010] Furthermore, the regulating valve is any one of a pressure regulating valve, a relief valve, a one-way throttle valve, and a proportional valve.

[0011] Furthermore, a pressure sensor for detecting the oil circuit pressure is provided between the second control valve and the mold locking high-pressure oil cylinder connecting oil circuit.

[0012] Furthermore, the multiple clamping hydraulic oil circuit structure of the injection molding machine is also provided with a pressure relief valve for automatically relieving pressure in the first oil circuit channel, and the oil pump is communicated with the pressure relief valve to form a second oil return channel.

[0013] Furthermore, the multiple clamping hydraulic oil circuit structure of the injection molding machine is also provided with a safety valve for automatically relieving pressure on the first oil circuit channel, and the oil pump is communicated with the safety valve to form a third oil return channel.

[0014] Furthermore, the second oil passage is also provided with a control shuttle valve for enhancing the cutting effect of the third control valve.

[0015] Furthermore, a first one-way valve is provided between the second control valve and the oil passage connecting the mold locking high-pressure oil cylinder.

[0016] Furthermore, a second one-way valve is provided at the front end of the fourth control valve in the first oil return channel.

[0017] Furthermore, a filter for filtering hydraulic oil is provided between the oil tank and the oil pump.

[0018] The multiple clamping method of the multiple clamping hydraulic oil circuit structure of the injection molding machine as described above includes the following clamping steps:

[0019] Under low pressure state: start the servo motor, open the first control valve and the third control valve, so that the first oil pump and the main oil circuit oil pump supply oil to the clamping high-pressure oil cylinder, and the mold is closed at this time.

[0020] Under high pressure: ensure the conduction of the first control valve, control the third control valve to cut off the second oil passage, and only the first oil pump supplies oil to the clamping high pressure oil cylinder.

[0021] Multiple clamping: ensure the conduction of the first control valve, and control the third control valve to cut off the second oil channel, so that only the first oil pump supplies oil to the clamping high-pressure oil cylinder. At this time, when the pressure sensor detects that the pressure is greater than the set first pressure value, the fourth control valve opens, the first oil return channel is connected, and part of the hydraulic oil flows back to the oil tank through the proportional adjustment of the regulating valve.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The multiple clamping hydraulic oil circuit structure of the injection molding machine of the present invention comprises an oil tank for storing hydraulic oil, a first oil pump and a main oil circuit oil pump for conveying hydraulic oil, a servo motor for providing power to the oil pump, and a clamping high-pressure oil cylinder connected with the oil pump and used for driving the mold to open and close the mold; a first control valve for controlling the on and off of the first oil pump and a second control valve for controlling the conduction of hydraulic oil to the clamping high-pressure oil cylinder are provided between the connecting oil circuit of the oil pump and the clamping high-pressure oil cylinder, and the oil pump is connected with the first control valve, the second control valve and the clamping high-pressure oil cylinder in sequence to form a first oil circuit channel ; A third control valve for controlling the on and off of the main oil circuit oil pump is provided between the connecting oil circuit of the main oil circuit oil pump and the locking high-pressure oil cylinder. The main oil circuit oil pump is connected with the third control valve, the first control valve, the second control valve and the locking high-pressure oil cylinder in sequence to form a second oil circuit channel; a first return oil channel is also provided between the second control valve and the connecting oil circuit of the locking high-pressure oil cylinder. The first return oil channel includes a fourth control valve for controlling the on and off of the first return oil channel and a regulating valve for controlling the pressure of the first return oil channel. The first return oil channel is connected with the fourth control valve, the regulating valve and the oil tank in sequence. Through the setting of multiple oil circuit channels and the control of a series of hydraulic oil valves, the pressure oil can be effectively delivered to each locking cylinder, thereby controlling the size of the locking force. And the multiple clamping steps of the multiple clamping hydraulic oil circuit structure of the above-mentioned injection molding machine can achieve the following advantages by combining the above-mentioned oil circuit structure.

[0024] The advantages of this solution are:

[0025] 1. Eliminate the pressure shock of high-pressure clamping and extend the service life of the parts of the clamping mechanism;

[0026] 2. The air marks and shrinkage holes inside the product disappear, improving the mechanical properties of the product.

[0027] 3. After molding, the internal stress is reduced, warping does not occur, and the quality of the product is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a hydraulic principle diagram of a preferred embodiment of the multiple clamping hydraulic oil circuit structure of the injection molding machine of the present invention;

[0029] Figure 2It is a structural schematic diagram of a preferred embodiment of a servo motor oil pump assembly of the present invention;

[0030] Figure 3 It is a structural schematic diagram of a preferred embodiment of the second control oil circuit control valve of the present invention;

[0031] Figure 4 It is a structural schematic diagram of a preferred embodiment of the first oil return channel control valve of the present invention;

[0032] Figure 5 It is an electrical control principle diagram of a preferred embodiment of the present invention.

[0033] In the figure: 1. first control valve; 2. pressure relief valve; 3. safety valve; 5. servo motor; 6. first oil pump; 9. third control valve; 10. control shuttle valve; 11. fourth control valve; 13. regulating valve. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0035] The multiple clamping hydraulic oil circuit structure of the injection molding machine of the present invention is as follows Figure 1-Figure 5 As shown, it includes an oil tank for storing hydraulic oil, a first oil pump 6 and a main oil circuit oil pump for conveying hydraulic oil, a servo motor 5 for providing power to the oil pump, and a clamping high-pressure oil cylinder connected to the oil pump and used to drive the mold to open and close the mold;

[0036] A first control valve 1 for controlling the on / off of the first oil pump 6 and a second control valve for controlling the hydraulic oil to pass through the mold-locking high-pressure oil cylinder are provided between the connecting oil circuit of the oil pump and the mold-locking high-pressure oil cylinder. The oil pump is connected to the first control valve 1, the second control valve and the mold-locking high-pressure oil cylinder in sequence to form a first oil circuit channel;

[0037] A third control valve 9 for controlling the on / off of the main oil circuit oil pump is provided between the connecting oil circuit of the main oil circuit oil pump and the clamping high-pressure oil cylinder. The main oil circuit oil pump is connected with the third control valve 9, the first control valve 1, the second control valve and the clamping high-pressure oil cylinder in sequence to form a second oil circuit channel;

[0038] A first oil return channel is also provided between the second control valve and the connecting oil circuit of the mold locking high-pressure cylinder. The first oil return channel includes a fourth control valve 11 for controlling the on-off of the first oil return channel and a regulating valve 13 for controlling the pressure of the first oil return channel. The first oil return channel is connected to the fourth control valve 11, the regulating valve 13 and the oil tank in sequence.

[0039] Through the setting of the above multiple oil channels and the control of a series of hydraulic oil valves, the pressure oil can be effectively delivered to each clamping cylinder, so as to control the clamping force. It can eliminate the pressure shock of high-pressure clamping, extend the life of the parts of the clamping mechanism, and at the same time eliminate the air marks and shrinkage holes inside the product, and ensure that the internal stress after molding is reduced and no warping occurs. Improve the mechanical properties and quality of the product.

[0040] The multiple clamping structure for injection molding machine in this solution is also provided with a pressure relief valve 2 for automatically relieving pressure in the first oil channel. The oil pump is connected with the pressure relief valve 2 and forms a second oil return channel. The pressure relief valve 2 (ReliefValve), also known as an overflow valve, is an automatic pressure relief device driven by the static pressure of the medium before the valve. It opens in proportion to the increase in pressure exceeding the opening force. It is mainly used in fluid occasions.

[0041] The multiple clamping structure for injection molding machine in this solution is also provided with a safety valve 3 for automatically releasing pressure to the first oil channel. The oil pump is connected with the safety valve 3 and forms a third oil return channel. Safety valve 3 is an automatic pressure relief device driven by the static pressure of the medium before the valve. It is characterized by a full opening action with a sudden opening. It is used in gas or steam occasions. The safety of the first oil channel can be ensured by setting the two valve bodies of the pressure relief valve 2 and the safety valve 3.

[0042] Since only a small force is required to maintain the die after the mold closing action is completed, the pressure of the oil pump does not need to be too high at this time. Too high pressure will produce a certain inertia and cause a certain life loss to the clamping high-pressure oil cylinder. For this reason, the first oil return channel is designed in this scheme. The first oil return channel is arranged between the second control valve and the connecting oil circuit of the clamping high-pressure oil cylinder. The first oil return channel includes a fourth control valve 11 for controlling the on and off of the first oil return channel and a regulating valve 13 for controlling the pressure of the first oil return channel. The first oil return channel is connected to the fourth control valve 11, the regulating valve 13 and the oil tank in sequence. Correspondingly, a pressure sensor for detecting the oil circuit pressure is also provided between the second control valve and the connecting oil circuit of the clamping high-pressure oil cylinder in this embodiment. The pressure of the hydraulic oil in the oil circuit can be monitored in real time through the detection of the pressure sensor. When the pressure of the hydraulic oil is too high, the fourth control valve 11 controls the first oil return channel to open, and conducts a part of the hydraulic oil back to the oil tank. At the same time, according to the degree of pressure, the flow rate of the hydraulic oil in the first oil return channel can be controlled by adjusting the proportion of the regulating valve 13, so as to achieve the effect of keeping the pressure of the clamping oil cylinder constant.

[0043] Preferably, the regulating valve 13 in this solution is any one of a pressure regulating valve, a relief valve, a one-way throttle valve, or a proportional valve. Of course, other valves that play a regulating role can also be used, which are not listed one by one here.

[0044] The second oil circuit channel in this embodiment is also provided with a control shuttle valve 10 for strengthening the cutting effect of the third control valve 9. The control shuttle valve 10 is set to strengthen the cutting effect of the third control valve 9 to ensure that in the high-pressure clamping state and multiple clamping processes, the main oil circuit pump does not work, the second oil circuit channel is cut off, and only the first oil pump 6 in the entire oil circuit structure supplies oil to the clamping high-pressure cylinder.

[0045] In order to prevent the hydraulic oil from flowing back, a first one-way valve is provided between the second control valve and the connecting oil path of the clamping high-pressure oil cylinder. The first oil return channel is provided with a second one-way valve at the front end of the fourth control valve 11 to ensure smooth operation of the hydraulic oil path.

[0046] In this embodiment, a filter for filtering the hydraulic oil is provided between the oil tank and the oil pump. The filter can filter out the dregs in the hydraulic oil and prevent the dregs from entering the oil pump and damaging the oil pump.

[0047] The specific multiple clamping method of the multiple clamping hydraulic oil circuit structure of the injection molding machine includes the following film locking steps:

[0048] Under low pressure state: start the servo motor 5, open the first control valve 1 and the third control valve 9, so that the first oil pump 6 and the main oil circuit oil pump supply oil to the clamping high-pressure oil cylinder, and the mold is closed at this time.

[0049] Under high pressure: the conduction of the first control valve 1 is ensured, and the third control valve 9 is controlled to cut off the second oil passage, and only the first oil pump 6 supplies oil to the clamping high pressure oil cylinder.

[0050] Multiple clamping: ensure the conduction of the first control valve 1, and control the third control valve 9 to cut off the second oil channel, and only the first oil pump 6 supplies oil to the clamping high-pressure cylinder. At this time, when the pressure sensor detects that the pressure is greater than the set first pressure value, the fourth control valve 11 opens, the first return oil channel is connected, and through the proportional adjustment of the regulating valve 13, part of the hydraulic oil flows back to the oil tank.

[0051] This patent aims at three shortcomings of ordinary hydraulic injection molding machines, specifically:

[0052] In view of the first shortcoming, the process of hydraulic oil compression in the clamping cavity to generate clamping force is divided into two stages. First, under low pressure, the main oil circuit pump and the first oil pump 6 are both involved in the work to quickly replenish the hydraulic oil in the clamping cavity; second, under high pressure, only the first oil pump 6 is used to generate clamping high pressure; but because the first oil pump 6 is a small displacement pump, its inertia is relatively small; on the control panel of the driver, changing the parameters of the oil pressure PID can increase the pressure more smoothly than a large displacement pump, and the pressure overshoot can be controlled within 2 bar, which is very helpful in extending the life of the clamping mechanism.

[0053] As for the second shortcoming, after the clamping mechanism of the injection molding machine closes the mold by oil pressure, the mold cavity is full of air. In the initial stage of injection, the molten plastic cannot provide pressure to the inner wall of the mold before filling the mold cavity. In order to ensure that the shape of the exhaust groove remains unchanged and can exhaust smoothly, the clamping force only needs to ensure that there is no leakage. As the molten plastic gradually fills the mold cavity and can gradually provide pressure to the inner wall of the mold, the clamping force also needs to be gradually increased to prevent defects such as air marks and shrinkage holes inside the plastic product and ensure normal molding of the product.

[0054] To address the third shortcoming, on the basis of adopting a multi-point glue injection method, after completing multiple stages of glue injection and pressure holding, while the glue is melting, the high-pressure pressure oil is maintained in the clamping cylinder, and the formed product is continuously squeezed through the template and mold to resist the internal stress of the product caused by temperature changes.

[0055] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. The multiple clamping hydraulic oil circuit structure of the injection molding machine is characterized by: The invention comprises an oil tank for storing hydraulic oil, a first oil pump and a main oil circuit oil pump for conveying hydraulic oil, a servo motor for providing power to the first oil pump and the main oil circuit oil pump, and a mold-locking high-pressure oil cylinder connected with the oil pump and used for driving the mold to open and close the mold; a first control valve for controlling the on and off of the first oil pump and a second control valve for controlling the hydraulic oil to pass through the mold-locking high-pressure oil cylinder are arranged between the connecting oil circuit between the oil pump and the mold-locking high-pressure oil cylinder, and the oil pump is connected with the first control valve, the second control valve and the mold-locking high-pressure oil cylinder in sequence to form a first oil circuit channel; the main oil circuit oil pump and A third control valve for controlling the on / off of the main oil circuit oil pump is provided between the connecting oil circuit of the mold locking high-pressure oil cylinder, and the main oil circuit oil pump is sequentially connected with the third control valve, the first control valve, the second control valve and the mold locking high-pressure oil cylinder to form a second oil circuit channel; a first oil return channel is also provided between the second control valve and the connecting oil circuit of the mold locking high-pressure oil cylinder, and the first oil return channel includes a fourth control valve for controlling the on / off of the first oil return channel and a regulating valve for controlling the pressure of the first oil return channel, and the first oil return channel is sequentially connected with the fourth control valve, the regulating valve and the oil tank; The regulating valve is any one of a pressure regulating valve, a relief valve, a one-way throttle valve or a proportional valve; A pressure sensor for detecting the oil circuit pressure is also provided between the second control valve and the mold locking high-pressure oil cylinder connecting oil circuit.

2. The multiple clamping hydraulic oil circuit structure of the injection molding machine according to claim 1, characterized in that: The multiple clamping hydraulic oil circuit structure of the injection molding machine is also provided with a pressure relief valve for automatically relieving pressure on the first oil circuit channel, and the oil pump is communicated with the pressure relief valve to form a second oil return channel.

3. The multiple clamping hydraulic oil circuit structure of the injection molding machine according to claim 1, characterized in that: The multiple clamping hydraulic oil circuit structure of the injection molding machine is also provided with a safety valve for automatically relieving pressure on the first oil circuit channel, and the oil pump is communicated with the safety valve and forms a third oil return channel.

4. The multiple clamping hydraulic oil circuit structure of the injection molding machine according to claim 1, characterized in that: The second oil passage is also provided with a control shuttle valve for enhancing the cutting effect of the third control valve.

5. The multiple clamping hydraulic oil circuit structure of the injection molding machine according to claim 1, characterized in that: A first one-way valve is also provided between the second control valve and the communicating oil passage of the mold locking high-pressure oil cylinder.

6. The multiple clamping hydraulic oil circuit structure of the injection molding machine according to claim 1, characterized in that: The first oil return passage is provided with a second one-way valve at the front end of the fourth control valve.

7. The multiple clamping hydraulic oil circuit structure of the injection molding machine according to claim 1, characterized in that: A filter for filtering hydraulic oil is provided between the oil tank and the oil pump.

8. The multiple clamping method of the multiple clamping hydraulic oil circuit structure of the injection molding machine according to any one of claims 1 to 7, characterized in that: The film locking steps include the following: In the low-pressure state: start the servo motor, open the first control valve and the third control valve, so that the first oil pump and the main oil circuit oil pump supply oil to the clamping high-pressure oil cylinder, and the mold is closed at this time; Under high pressure: ensuring the conduction of the first control valve, and controlling the third control valve to cut off the second oil passage, so that only the first oil pump supplies oil to the clamping high-pressure oil cylinder; Multiple clamping: ensure the conduction of the first control valve, and control the third control valve to cut off the second oil channel, so that only the first oil pump supplies oil to the clamping high-pressure oil cylinder. At this time, when the pressure sensor detects that the pressure is greater than the set first pressure value, the fourth control valve opens, the first oil return channel is connected, and part of the hydraulic oil flows back to the oil tank through the proportional adjustment of the regulating valve.

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