Pressing device

Abstract

To provide a press device which is easy to smoothly operate a slide.SOLUTION: A press device (1) includes: a slide (10) operated by receiving the pressure of a first fluid chamber (311) and the pressure of a second fluid chamber (313); a flow rate variable pump (351) for sending working fluid to the first fluid chamber (311) and the second fluid chamber (313); and an opening variable valve (352) which is provided in a flow channel between the flow rate variable pump (351) and the second fluid chamber (313).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a press device.

Background Art

[0002] Patent Document 1 discloses a hydraulic press including a first oil chamber that moves a slide at high speed and a second oil chamber that generates a large pressing force on the slide.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When moving the slide with the pressures of two oil chambers, there is a problem that smooth movement of the slide cannot be obtained depending on the way of sending the hydraulic oil to the two oil chambers.

[0005] An object of the present invention is to provide a press device that can easily move the slide smoothly.

Means for Solving the Problems

[0006] The press device according to the present invention includes a slide that operates by receiving the pressure of a first fluid chamber and the pressure of a second fluid chamber, a flow rate variable pump that sends a working fluid to the first fluid chamber and the second fluid chamber, an opening degree variable valve provided in a flow path between the flow rate variable pump and the second fluid chamber, and 、 A speed switching start position and a speed switching completion position are set for switching the speed of the slide down to the downward speed for pressurization. When the speed is reduced while operating the slide from the speed switching start position to the speed switching completion position, the opening degree of the variable opening valve is gradually increased, and the flow rate of the variable flow rate pump is gradually decreased. is provided.

Effects of the Invention

[0007] According to the present invention, in a press device having a slide that operates in response to the pressure of a first fluid chamber and the pressure of a second fluid chamber, the effect of making it easier to operate the slide smoothly can be obtained. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows a press apparatus according to an embodiment of the present invention. [Figure 2] This is a timing chart showing an example of press machine control (Example 1). [Figure 3] This is a timing chart showing example 2 of press machine control. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below with reference to the drawings. In this embodiment, an example in which hydraulic oil is used as the working fluid will be described. However, various liquids or fluids may be used as the working fluid. Hereinafter, fluid passages will be referred to as oil passages, fluid pressure as hydraulic pressure, and fluid chambers as oil chambers.

[0010] Figure 1 shows a press apparatus according to an embodiment of the present invention. As shown in Figure 1, the press apparatus 1 of this embodiment comprises a slide 10, a bed 20, a slide drive unit 30, a position detection unit 40 for detecting the position of the slide 10, a first hydraulic pressure detector 41 for detecting the hydraulic pressure of the first oil chamber 311, a second hydraulic pressure detector 42 for detecting the hydraulic pressure of the second oil chamber 313, and a control unit 50. An upper die 2 is attached to the slide 10, and a lower die 3 is attached to the bed 20.

[0011] The slide drive unit 30 includes a main cylinder 31 and piston 32 that pressurize the slide 10, and a pull-back cylinder piston 33 for pulling the slide 10 back from the bed 20. Furthermore, the slide drive unit 30 includes a hydraulic circuit 35 that supplies hydraulic fluid to the main cylinder 31, and a hydraulic circuit (not shown) that supplies hydraulic fluid to the pull-back cylinder piston 33. In this specification, the term "piston" includes a ram capable of generating a driving force in only one direction relative to the cylinder.

[0012] The slide 10 is connected to the piston 32. The main cylinder 31 has a first oil chamber 311 and a second oil chamber 313, and pressure is applied to the slide 10 from the piston 32 when hydraulic pressure is applied to either oil chamber. The area over which the hydraulic fluid in the first oil chamber 311 pushes the piston 32 in the forward and backward directions is smaller than the area over which the hydraulic fluid in the second oil chamber 313 pushes the piston 32 in the forward and backward directions. With this configuration, the slide 10 can be driven at a higher speed by pressurizing the hydraulic fluid into the first oil chamber 311 than by pressurizing the hydraulic fluid into the second oil chamber 313. Furthermore, by pressurizing the hydraulic fluid into the second oil chamber 313, a greater pressing force can be generated on the slide 10 than by pressurizing the hydraulic fluid into the first oil chamber 311.

[0013] The hydraulic circuit 35 includes a variable flow rate pump 351 that pumps hydraulic fluid at a variable flow rate, and a variable opening valve 352 provided in the oil passage between the variable flow rate pump 351 and the second oil chamber 313.

[0014] The variable flow rate pump 351 changes the flow rate of the hydraulic fluid by switching the power output from the servo motor 351a between high and low values. The method of changing the flow rate of the variable flow rate pump 351 can be any method. Below, the flow rate of the variable flow rate pump 351 is expressed in terms of the rotational speed of the servo motor 351a. A higher rotational speed indicates a larger flow rate.

[0015] The opening degree variable valve 352 can change the opening degree of the oil passage between 0% and 100%. In FIG. 1, the opening degree variable valve 352 is configured to change the opening degree by hydraulic control from the pilot valve 353, but various methods may be adopted, such as changing the opening degree by electric drive. Further, the pilot valve 353 is configured to control the opening degree based on the differential signal between the feedback signal from the opening degree variable valve 352 and the command signal from the control unit 50, and various methods may also be adopted for this control method. As the opening degree variable valve 352, a servo logic valve or a servo valve can be applied.

[0016] The output part of the flow rate variable pump 351 is connected to the first oil chamber 311 via the oil passage 312. The output part of the flow rate variable pump 351 is connected to the second oil chamber 313 via the opening degree variable valve 352 and the oil passage 314. In the oil passage 314, a one-way valve 355 such as a pre-filter valve that supplies hydraulic oil from the tank 354 when the hydraulic pressure in the second oil chamber 313 drops is provided.

[0017] According to the slide drive unit 30 configured as described above, when the opening degree variable valve 352 is closed, the hydraulic oil is output from the flow rate variable pump 351, and the hydraulic oil is sent to the first oil chamber 311, causing the piston 32 to descend at high speed. During this drive, the hydraulic oil is sent into the second oil chamber 313 from the tank 354 through the one-way valve 355, and does not give a large resistance to the operation of the piston 32. Also, when the valve 352 is open and the hydraulic oil is output from the flow rate variable pump 351, the hydraulic oil can be supplied to the first oil chamber 311 and the second oil chamber 313 to generate a large pressing force on the piston 32.

[0018] The position detection unit 40 detects the position of the slide 10 and sends the detection result to the control unit 50. As the position detection unit 40, a linear encoder can be adopted, but any configuration may be adopted as long as the position of the slide 10 can be detected.

[0019] The first hydraulic detector 41 and the second hydraulic detector 42 send the detection results of the hydraulic pressure in the first oil chamber 311 and the detection results of the hydraulic pressure in the second oil chamber 313 to the control unit 50, respectively.

[0020] The control unit 50 is a computer that executes a control program, and controls the flow rate of the variable flow pump 351 and the opening degree of the variable opening valve 352.

[0021] <Control Example 1 of Press Device> FIG. 2 is a timing chart showing Control Example 1 of the press device. Control Example 1 is an example in which the control unit 50 controls the flow rate of the variable flow pump 351 and the opening degree of the variable opening valve 352 based on the position of the slide 10.

[0022] The press control of Control Example 1 is a press control in which after the slide 10 is lowered at high speed, the speed of the slide 10 is reduced to the lowering speed for pressing, and then the workpiece is formed by the pressing force of the slide 10. Since this press control can realize a rapid descent of the slide 10 that suppresses the temperature drop of the workpiece in hot forging in which the heated workpiece is set in the lower die 3 and formed, it is particularly useful.

[0023] Control Example 1 starts in a state where the slide 10 is in the upper position (for example, the upper limit position). In the control unit 50, the "speed switching start position", the "speed switching completion position", and the "pressing completion position" are set in order from the higher position as slide positions for switching control. The "speed switching completion position" is set to the height before the upper die 2 applies a load to the workpiece, and the "pressing completion position" is set to the position of forming completion.

[0024] When the operation start timing t1 of the slide 10 is reached, the control unit 50 sets the rotation speed of the variable flow pump 351 to the rotation speed for high-speed approach in a state where the opening degree of the variable opening valve 352 is 0%. The rotation speed for high-speed approach is a rotation speed at which a large amount of flow rate can be output in a state where the output hydraulic pressure of the variable flow pump 351 is not high. Then, this control is continued for a period T1 until the slide 10 reaches the "speed switching start position".

[0025] During the control of the period T1, the hydraulic fluid output from the variable flow rate pump 351 is sent to the first oil chamber 311, causing the slide 10 to descend at high speed.

[0026] Next, the control unit 50 controls the speed of the slide 10 during the period T2 from the "speed switching start position" to the "speed switching completion position". During this period T2, the control unit 50 controls the variable opening valve 352 so that its opening degree gradually switches from 0% to 100%, and the rotational speed of the variable flow rate pump 351 so that its rotational speed gradually switches from the high-speed approach rotational speed to the pressurizing descent rotational speed. The pressurizing descent rotational speed is the rotational speed at which the variable flow rate pump 351 can output high pressure for molding. The control during period T2 can be achieved by coordinating the time it takes for the variable flow rate pump 351 to transition to the pressurizing descent rotational speed with the time it takes for the variable opening valve 352 to transition to 100% opening, while also coordinating with the position of the slide 10.

[0027] Figure 2 shows an example where the change in the opening degree of the variable valve 352 and the change in the rotational speed of the variable flow pump 351 during period T2 are linear changes. However, the change may follow a curve, or any curve that allows the speed of the slide 10 to change smoothly.

[0028] Controlling period T2 causes the speed of slide 10 to smoothly decrease from a speed at which slide 10 descends rapidly to a slow speed at which slide 10 can generate a large pressing force.

[0029] Next, during the period T3 from when the slide 10 moves from the "speed switching completion position" to the "pressurization completion position," the control unit 50 drives the variable flow rate pump 351 at the pressurization rotation speed with the variable opening valve 352 at 100% opening. As an example, the control unit 50 maintains the rotation speed of the variable flow rate pump 351 at the "pressurization descent rotation speed."

[0030] During the period T3, the slide 10 applies pressure to the workpiece, thereby forming it. The position at which the slide 10 begins to apply pressure to the workpiece corresponds to one of the positions between the "speed switching completion position" and the "pressure completion position".

[0031] Next, the control unit 50 controls the slide 10 to maintain the pressurized position during period T4. During this period T4, the control unit 50 controls the variable flow rate pump 351 to a rotational speed for maintaining the pressurized pressure while the opening of the variable opening valve 352 is at 100%. At this time, the control unit 50 may also perform feedback control to control the rotational speed of the variable flow rate pump 351 while monitoring the position data of the slide 10, so that the position is maintained.

[0032] Once the maintenance control for period T4 is complete, the control unit 50 stops the variable flow rate pump 351 and operates the retraction cylinder piston 33 to retract the slide 10 to the upper position. This completes one press control process.

[0033] According to the control example 1 described above, the slide 10 descends at high speed during period T1 before the upper die 2 comes into contact with the workpiece. Then, during the subsequent period T3, the slide 10 descends at a low speed, thereby forming the workpiece. Therefore, in hot forging, where a heated workpiece is set in the lower die 3 for forming, the rapid descent of the slide 10 during period T1 enables a forming process that suppresses the temperature drop of the workpiece.

[0034] Furthermore, according to the control example 1 described above, during the period T2 in which the slide 10 moves from the "speed switching start position" to the "speed switching completion position," the control unit 50 gradually increases the opening of the variable-opening valve 352 and gradually decreases the flow rate of the variable-flow pump 351. This control makes the speed change of the slide 10 smoother and reduces the shock caused by sudden speed changes of the slide 10.

[0035] Even without the control of the above-mentioned period T2, by opening the oil passage 314 between the output of the variable flow rate pump 351 and the second oil chamber 313 and reducing the flow rate of the variable flow rate pump 351, the slide 10 can be lowered at high speed before the workpiece is formed, and then a large forming pressure can be generated on the slide 10. However, in this case, a sudden change in the speed of the slide 10, as well as a sudden change in hydraulic pressure in the oil passages 312 and 314 and the first oil chamber 311 and the second oil chamber 313, will occur, causing a large shock to the press device 1. In this embodiment, such a shock can be reduced.

[0036] <Example of press machine control 2> Figure 3 is a timing chart showing control example 2 of a press machine. Control example 2 is an example in which the control unit 50 controls the flow rate of the variable flow rate pump 351 and the opening degree of the variable opening valve 352 based on the hydraulic pressure of the first oil chamber 311 and the hydraulic pressure of the second oil chamber 313.

[0037] The press control in Control Example 2 realizes a press operation in which the pressing force of the slide 10 is continuously increased over time. This press operation is advantageous because it allows the workpiece to be formed with continuous pressure without requiring the operator to be aware of the switching between the two types of oil chambers, the first oil chamber 311 and the second oil chamber 313.

[0038] In control example 2, the operator first sets the desired pressure curve G1. The pressure curve G1 is a characteristic curve that represents the change in pressure over time. The control unit 50 controls the press device 1 so that the requested pressure curve G1 is obtained.

[0039] In the example shown in Figure 3, a linearly increasing pressure curve G1 is set, but a curved pressure curve may also be used. The pressure curve is set within a range smaller than the "total maximum pressure" of the press device 1. The "total maximum pressure" is the sum of the maximum pressure that can be generated from the first oil chamber 311 and the maximum pressure that can be generated from the second oil chamber 313.

[0040] When the pressure line G1 is set, the control unit 50 calculates the hydraulic pressure line H1 of the first oil chamber 311 and the hydraulic pressure line H2 of the second oil chamber 313 that realize the pressure line G1. The hydraulic pressure line H1 represents the time change of hydraulic pressure in the first oil chamber 311, and the hydraulic pressure line H2 represents the time change of hydraulic pressure in the second oil chamber 313. The hydraulic pressure lines H1 and H2 can be calculated as follows, divided into a pre-merging period T11 in which hydraulic pressure is applied only to the first oil chamber 311, a merging period T12 in which different hydraulic pressures are applied to the first oil chamber 311 and the second oil chamber 313, and a post-merging period T13 in which equivalent hydraulic pressures are applied to the first oil chamber 311 and the second oil chamber 313.

[0041] Specifically, first, the control unit 50 determines the merging start timing t11 to be at any timing within the period in which the pressure line G1 can be achieved using only the hydraulic pressure of the first oil chamber 311. In the example in Figure 3, the merging start timing t11 is set to the timing at which the maximum pressure of the first oil chamber 311 (the maximum pressure that can be generated from the first oil chamber 311) is reached. Furthermore, the control unit 50 determines the merging completion timing t12 to be at any timing thereafter.

[0042] By determining the timings t11 and t12 in this way, the control unit 50 can calculate what hydraulic pressure should be set in the first oil chamber 311 during the pre-merging period T11 to achieve the pressure curve G1 for period T11. Furthermore, it can calculate what hydraulic pressure should be set in the first oil chamber 311 during the post-merging period T13 to achieve the pressure curve G1 for period T13. This is because in the post-merging period T13, the hydraulic pressure of the first oil chamber 311 and the hydraulic pressure of the second oil chamber 313 are the same.

[0043] Furthermore, the control unit 50 can calculate the hydraulic pressure curve connecting the hydraulic pressure at the merging start timing t11 and the hydraulic pressure at the merging completion timing t12 as the hydraulic pressure line H1 of the first oil chamber 311 during the merging period T12. Through such calculations, the hydraulic pressure line H1 over the entire period can be determined.

[0044] Furthermore, the control unit 50 sets the hydraulic pressure of the second oil chamber 313 to zero during the pre-merging period T11, and sets the hydraulic pressure of the second oil chamber 313 during the post-merging period T13 to a value equivalent to the hydraulic pressure of the first oil chamber 311 during period T13. In addition, the control unit 50 calculates the hydraulic pressure of the second oil chamber 313 during the merging period T12 from the pressure line G1 during the merging period T12 and the hydraulic pressure line H1 of the first oil chamber 311 during the merging period T12. That is, the hydraulic pressure of the second oil chamber 313 should be calculated so that the pressure from the second oil chamber 313 is insufficient to meet the pressure line G1 if only the pressure from the first oil chamber 311 is obtained from the second oil chamber 313. Through such calculations, the hydraulic pressure line H2 for the entire period of the second oil chamber 313 is obtained.

[0045] Once hydraulic lines H1 and H2 are determined, the system becomes ready for press control. Therefore, when the control unit 50 receives a command to start press control in this state, it starts the press control described below.

[0046] First, during period T11, the control unit 50 maintains the opening of the variable-opening valve 352 at 0%, and during the following period T12, it controls the opening of the variable-opening valve 352 by performing feedback control, etc., so that the hydraulic pressure in the second oil chamber 313 matches the hydraulic pressure line H2. In Figure 3, the opening during period T12 is shown to be almost constant, but in reality, the opening contains many fluctuations due to the feedback control. Subsequently, during period T13, the control unit 50 sets the opening of the variable-opening valve 352 to 100% and maintains it there.

[0047] In parallel with the control of the variable-opening valve 352 described above, the control unit 50 controls the rotational speed (flow rate) of the variable-flow pump 351 by performing feedback control, etc., during periods T11 and T12 so that the hydraulic pressure in the first oil chamber 311 matches the hydraulic pressure line H1. Furthermore, in the next period T13, the control unit 50 controls the rotational speed (flow rate) of the variable-flow pump 351 by performing feedback control, etc., so that the hydraulic pressure in the first oil chamber 311 or the second oil chamber 313 matches the hydraulic pressure lines H1 and H2. In Figure 3, the rotational speed during period T12 is shown to change linearly, but in reality, the rotational speed contains many fluctuations due to feedback control.

[0048] During period T12, the control of the variable-opening valve 352 and the control of the variable-flow pump 351 are performed in parallel based on two hydraulic lines H1 and H2. However, even during this period T12, the control unit 50 controls the variable-opening valve 352 based on one hydraulic line H2 and the variable-flow pump 351 based on one hydraulic line H1, so that the control of both can be performed stably.

[0049] Through the control described above, hydraulic pressure is generated in the first oil chamber 311 along the hydraulic pressure line H1, and hydraulic pressure is generated in the second oil chamber 313 along the hydraulic pressure line H2. As a result, a continuous pressing force can be obtained from the slide 10 along the pressing force line G1.

[0050] As described above, the press device 1 of this embodiment includes a slide 10 that operates in response to the hydraulic pressure of the first oil chamber 311 and the second oil chamber 313, a variable flow rate pump 351 that supplies hydraulic fluid to the first oil chamber 311 and the second oil chamber 313, and a variable opening valve 352 provided in the flow path between the variable flow rate pump 351 and the second oil chamber 313. With this configuration, by appropriately controlling the opening degree of the variable opening valve 352, it becomes possible to control the hydraulic pressure of the first oil chamber 311 and the hydraulic pressure of the second oil chamber 313 to gradually approach each other. Therefore, smooth movement of the slide 10 with less shock is easily obtained.

[0051] Furthermore, according to the press device 1 of this embodiment, the control unit 50 controls the flow rate (rotational speed) of the variable flow rate pump 351 and the opening degree of the variable opening valve 352 based on the position of the slide 10. With such control, as shown in the control example 1 above, it is possible to stably achieve control such as moving the slide 10 at high speed to a certain position, then smoothly reducing the speed, and moving the slide 10 at a low speed to obtain a large pressing force from the slide 10.

[0052] Furthermore, according to the press device 1 of this embodiment, as shown in control example 1, the control unit 50 changes the flow rate of the variable flow rate pump 351 and the opening degree of the variable opening valve 352 before the slide 10 moves to the molding start position where it begins to apply pressure to the workpiece. This period corresponds to the period when no load is applied to the slide 10 and a sudden change in the speed of the slide 10 may occur. Therefore, by changing the flow rate of the variable flow rate pump 351 and the opening degree of the variable opening valve 352 during this period, a sudden change in the speed of the slide 10 can be suppressed, and a shock to the press device 1 can be prevented.

[0053] Furthermore, according to the press apparatus 1 of this embodiment, as shown in control example 2, the control unit 50 changes the flow rate of the variable flow pump 351 and the opening degree of the variable opening valve 352 based on the required pressure line G1 of the slide 10. With this control, the operator can form the workpiece with various pressures without being aware of switching between the two types of oil chambers, the first oil chamber 311 and the second oil chamber 313.

[0054] More specifically, according to the press apparatus 1 of this embodiment, as shown in control example 2, the control unit 50 controls the flow rate of the variable flow rate pump 351 based on the hydraulic line H1 of the first oil chamber 311, and controls the opening degree of the variable opening valve 352 based on the hydraulic line H2 of the second oil chamber 313. By controlling the flow rate and opening degree separately in these two systems, stable control of the variable flow rate pump 351 and the variable opening valve 352 can be achieved.

[0055] Furthermore, according to the press device 1 of this embodiment, there is a period, such as period T2 in control example 1 or period T12 in control example 2, during which the control period for changing the flow rate of the variable flow rate pump 351 and the control period for changing the opening degree of the variable opening valve 352 overlap. Controlling during this period enables a wide range of control, such as significantly reducing the speed of the slide 10 while making the slide 10 operate smoothly (period T2 in control example 1), or generating a continuously changing pressing force from the slide 10 (period T12 in control example 2).

[0056] Furthermore, according to the press device 1 of this embodiment, the variable-opening valve 352 is provided in the oil passage between the variable-flow pump 351 and the second oil chamber 313, and even when the variable-opening valve 352 is open, the hydraulic fluid output from the variable-flow pump 351 continues to be supplied to the first oil chamber 311. With this connection configuration of the variable-opening valve 352, efficient distribution control of hydraulic fluid with minimal waste becomes possible, enabling a wide range of control with a low-cost configuration.

[0057] Embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. For example, in the above embodiments, an example was shown in which one main cylinder 31 has two oil chambers 311 and 313, but for example, a configuration in which first and second cylinders and pistons (e.g., a double cylinder piston) pressurize the slide may be used. In this case, a first fluid chamber is provided in the first cylinder, and a second fluid chamber is provided in the second cylinder. Also, in the above embodiments, an example was shown in which the opening degree of the variable opening valve is controlled between 0% and 100%, but for example, the opening degree of the variable opening valve may be controlled between any opening degree, such as 5% and 95%. Furthermore, details shown in the embodiments can be modified as appropriate without departing from the spirit of the invention. [Explanation of symbols]

[0058] 1 Pressing device 2 Upper mold 3 Lower mold 10 slides 20 beds 30 Slide drive unit 31 Main Cylinder 32 pistons 35 Hydraulic Circuit 311 Oil room 1 312 Oil road 313 2nd oil room 314 Oil road 351 Variable flow pump 352 Variable opening valve 40 Position detection unit 41. First hydraulic detector 42. Second hydraulic sensor 50 Control Unit

Claims

1. A slide that operates in response to the pressure of the first fluid chamber and the pressure of the second fluid chamber, A variable flow pump that supplies working fluid to the first fluid chamber and the second fluid chamber, A variable-opening valve is provided in the flow path between the variable-flow pump and the second fluid chamber, Equipped with, A speed switching start position and a speed switching completion position are set for switching the speed of the slide down to the downward speed for pressurization. A press device that, when the speed is reduced while operating the slide from the speed switching start position to the speed switching completion position, gradually increases the opening of the variable opening valve and gradually decreases the flow rate of the variable flow rate pump.

2. The system includes a control unit that controls the flow rate of the variable flow rate pump and the opening degree of the variable opening valve, The control unit controls the flow rate and the opening degree based on the position of the slide. The press apparatus according to claim 1.

3. The control unit changes the flow rate and the opening before the slide moves to the molding start position where it begins to apply pressure to the workpiece. The press apparatus according to claim 2.

4. The system includes a control unit that controls the flow rate of the variable flow rate pump and the opening degree of the variable opening valve, The control unit controls the flow rate and the opening degree based on the required pressure applied to the slide. The press apparatus according to claim 1.

5. The system includes a control unit that controls the flow rate of the variable flow rate pump and the opening degree of the variable opening valve, The control unit controls the flow rate based on the pressure in the first fluid chamber and controls the opening degree based on the pressure in the second fluid chamber. The press apparatus according to claim 1.

6. The press apparatus according to claim 2 or claim 5, wherein the control period for changing the flow rate and the control period for changing the opening overlap in at least part.

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