JP3240265B2 - Hydraulic control method of mold clamping device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control method for a mold clamping device such as an injection molding machine and the like, and more particularly to a switching timing for performing a brake control when switching a moving die plate from a high speed to a low speed in the mold clamping device. The present invention relates to a hydraulic control method that is appropriately set.

[0002]

2. Description of the Related Art Conventionally, for example, in an injection molding machine, an operation of a mold clamping cylinder is accelerated to increase a mold clamping speed in order to increase a cycle. However, if the molds collide at high speed, the molds may be damaged,
In order to switch the mold clamping speed to a low speed at a position where the moving mold that has started the mold clamping operation at high speed is close to the fixed mold, the amount of pressurized oil discharged from the hydraulic supply source (into the mold cylinder) The hydraulic brake circuit for reducing the pressure oil supply amount and forcibly reducing the speed is adopted.

As a specific example of such a hydraulic brake circuit, for example, a hydraulic brake circuit having a configuration shown in FIG. 5 has been proposed (Japanese Patent Laid-Open No. Hei 6-134829). That is, in FIG. 5, the mold clamping cylinder 10 is defined by the piston 10a into a chamber A and a chamber B in which the piston rod 10b is inserted. The main hydraulic pump 12 composed of a variable displacement pump has a suction side connected to the tank T and a discharge side connected to the discharge pipe 13. This discharge line 13
Is branched on the way, one is connected to the chamber A via a pipe 14, the other is connected to the chamber B via a pipe 15, and the discharge pipe 13 is provided with a relief valve 17 in the bypass 16. It is provided so that the discharge pressure of the main hydraulic pump 12 is kept constant.

[0004] Each of the conduits 14 and 15 is provided with a cartridge valve 18 and 19, respectively.
2 is configured to select and supply either the A chamber or the B chamber of the mold clamping cylinder 10. The pipeline 14 that communicates the cartridge valve 18 with the chamber A is branched and provided with a pipeline 20. The pipeline 20 is provided with a cartridge valve 21, and the cartridge valve 21 is opened by opening the cartridge valve 21. The pressure oil passing through the pipe 14 is supplied to the tank T
It is configured so that it can be returned to. Also,
The pipe 15 that communicates the cartridge valve 19 with the chamber B is also branched, and a discharge pipe 22 is provided. In the discharge pipe 22, cartridge valves 23 and 24 that function as brake valves are provided in parallel. Have been. Then, the pressure oil is returned to the tank T by opening these cartridge valves 23 and 24.

However, a pilot hydraulic pump 40 is provided separately from the main hydraulic pump 12, and a pilot line 25 for controlling opening and closing of a cartridge valve is connected to a discharge side line 41 of the pilot hydraulic pump 40. Have been. This pilot line 25 is branched after a check valve 26 is connected, one of which is connected to an electromagnetic pilot switching valve 27 at a 4-port, 3-position, and the other is connected to an electromagnetic pilot switching valve 28 at a 4-port, 2-position. ing. Also,
The 4 port 3 position electromagnetic pilot switching valve 27 includes:
A pilot line 29 for opening and closing the cartridge valve 18 and the cartridge valve 24, and a pilot line 3 for opening and closing the cartridge valve 19 and the cartridge valve 21.
0 is connected. Further, a pilot line 31 provided with a throttle 34 for opening and closing the cartridge valve 23 is connected to the electromagnetic pilot switching valve 28 at the 4-port 2-position. A pressure adjusting valve 43 composed of a proportional electromagnetic relief valve for adjusting the pressure is attached to the discharge side pipe line 41 of the pilot hydraulic pump 40, and when the pressure exceeds a predetermined pressure, the pressure oil is supplied to the tank T. It is configured to discharge and maintain a predetermined pressure.

A limit switch 32 for detecting that the movable mold has approached the fixed mold by the operation of the mold clamping cylinder 10 is provided.
A control device 42 is provided for reducing the discharge amount of the main hydraulic pump 12 and appropriately controlling the set pressure of the pressure regulating valve 43 of the pilot hydraulic pump 40 at the start of the brake operation of the second hydraulic pump 2.

When the electromagnetic pilot switching valve 27 at the 4-port 3-position is switched to the side a from the state shown in FIG. Pilot pressure is applied to the cartridge valve 21 to close the valve.
8. Pilot line 2 of cartridge valve 24 for discharging chamber B
9 is connected to the tank T. Therefore, the main hydraulic pump 12
Is supplied to the chamber A of the mold clamping cylinder 10 through the mold clamping cartridge valve 18 to operate the piston 10a in the mold clamping direction. At this time, the pressure oil on the chamber B side is returned to the tank T through the discharge pipe 22, the cartridge valves 23 and 24.

Subsequently, when the movable mold approaches the fixed mold in accordance with the mold clamping operation, a limit switch 32 as a brake start detector for starting the braking operation detects this approach. Control device 42 by signal
Reduces the discharge amount of the main hydraulic pump 12 and appropriately controls the set pressure of the pressure regulating valve 43 installed in the discharge-side pipe of the pilot hydraulic pump 40. This pressure oil is used to control the electromagnetic pilot at the four-port two-position. Switch the switching valve 28 from the c side to d
Switch to the side. By switching the electromagnetic pilot switching valve 28 at the 4-port, 2-position, a pilot pressure is applied to the cartridge valve 23, the cartridge valve 23 is closed, and the pressure oil discharged from the chamber B of the mold clamping cylinder 10 is supplied to the cartridge valve 24. Will be returned to the tank T from only the passage,
The amount of pressure oil discharged from the B chamber of the mold clamping cylinder 10 is reduced,
A braking action will occur on the piston 10a.

As described above, according to the conventional hydraulic brake circuit, as the mold clamping speed increases, the flow rate of the pressure oil discharged from the chamber B of the mold clamping cylinder 10 increases, and the cartridge valve 23 closes. When trying to, discharge line 2
2, the pilot pressure must be set to a pilot oil pressure not to be defeated by the surge pressure.
And the pressure adjusting valve 43, the pressure can be set to an arbitrary pressure different from the pressure of the main hydraulic pump 12, and the responsiveness of the brake operation according to the mold clamping speed in a high-speed region can be improved. It can be achieved easily and conveniently.

Further, since the pressure setting valve 43 can easily change the pressure setting by remote control by the control device 42, the troublesome adjustment of changing the hole diameter of the orifice 34 becomes unnecessary. The mold opening is 4 port 3
By switching the electromagnetic pilot switching valve 27 in the position to the b side, the cartridge valves 18 and 24 are closed, the cartridge valves 19 and 21 are opened, and pressure oil is supplied to the B chamber of the mold clamping cylinder 10, The pressure oil in the A room is discharged to the tank T through the pipe 20. Also, if the pilot oil pressure of the cartridge valve 21 is adjusted according to the mold opening speed in the same manner as described above, the responsiveness of the brake can be improved even when the mold is opened.

[0011]

However, the hydraulic brake circuit in the above-described conventional mold clamping device still has a drawback in operability and operating characteristics to be improved.

That is, in the hydraulic brake circuit of the conventional mold clamping device, as described above, a valve (cartridge valve) provided in the hydraulic circuit for performing a braking operation when the movement of the movable mold is switched from high speed to low speed. The switching operation of (2) is performed by detecting the position of the moving-side mold.

In this case, the forward and backward movements of the moving side mold are performed by supplying and discharging pressure oil to and from the mold clamping cylinder by the direction control valve, and by detecting the position of the moving side mold, the brake operating valve is operated. When the valve is operated, the brake is controlled by the meter-out side throttle function. In the brake control, an operation for reducing the discharge amount of the main hydraulic pump is also performed on the meter-in side at the same time.

However, in the hydraulic brake circuit having the above-described structure, since the switching from high speed to low speed is performed rapidly, an impact is generated, the time until the speed becomes stable and low is varied, and the molding cycle time is inadequate. There is a difficulty to be uniform.

For this reason, it has been proposed to set a timer to delay the start of brake control, for example, at the timing of switching from high speed to low speed.

However, also in this case, since the speed setting at the time of high speed and the timer setting are not technically related to each other, the moving speed of the moving mold at the time of time-out depends on the weight of the mold and different molding machines. Not only does the model vary, but also when the speed setting at the time of high speed is changed, the moving speed of the moving side mold varies, and there is a problem that the occurrence of the impact cannot be eliminated (see FIG. 4).

Further, as a conventional method of controlling a brake valve in hydraulic control of a mold clamping device, a piston is moved by hydraulic pressure supplied from a large capacity pump and a small capacity pump.
A brake valve is disposed on the discharge oil discharge circuit at that time, and the brake valve is operated to control the movement speed of the piston from high speed to low speed. The control method of the brake valve is configured such that the back pressure is measured at a time, and when the detected value of the back pressure after the operation of the brake valve reaches a reference value, the large capacity pump is unloaded to switch from high speed to low speed. It has been proposed (Japanese Patent Publication No. 1-58057).

That is, in this brake valve control method, the brake can be reliably operated when switching from high speed to low speed by measuring the back pressure of the piston rod side cylinder chamber. In the above, the operation timing of the brake valve was adjusted every time the unloading position of the large-capacity pump was set. However, according to the proposal, only by setting the operating position of the brake valve, Since the large-capacity pump unloads a little later, there is no need to adjust the timing of the operation of the brake valve, and it is possible to realize a brake circuit using a brake valve in which the brake always operates optimally.

However, as described above, operating the brake valve before unloading the large-capacity pump to switch from high-speed to low-speed causes the moving speed of the moving-side mold at high speed to fluctuate, resulting in a large-capacity pump. When unloading is performed, an impact is generated, and the time required for a stable low speed is varied, and the molding cycle time is not uniform.

Accordingly, an object of the present invention is to provide a mold clamping apparatus for opening and closing a mold, in which when a mold clamping cylinder is switched from a high speed to a low speed, the timing of a brake operation is appropriately set in accordance with the speed setting at a high speed. It is an object of the present invention to provide a hydraulic control method of a mold clamping device that can eliminate the occurrence of an impact and realize stable low-speed movement and a molding cycle time.

[0021]

In order to achieve the above object, a method of controlling hydraulic pressure of a mold clamping device according to the present invention comprises a variable displacement pump for a cylinder pressure chamber defined by a piston of a mold clamping cylinder. A discharge pipe connected to the tank and a discharge pipe connected to the tank are connected so as to be selectively connected to each other via a directional switching valve, and a discharge flow rate of a variable displacement pump is controlled to the discharge pipe. In addition to providing an electromagnetic proportional switching valve, a brake valve and a throttle are provided in parallel in the discharge line, and when the approach position between the dies is detected, the electromagnetic proportional switching valve is operated to switch from high speed to low speed. In the hydraulic control method for a mold clamping device configured to perform a switching operation and a braking operation by switching a brake valve, a moving speed of a mold by a mold clamping cylinder is detected, and the mold clamping is performed. When operation of the cylinder is switched from a high speed to a low speed, at the time when the speed required proportions from moving velocity at high speed is lowered, characterized by operating switching the brake valve.

In this case, the moving speed of the mold can be detected by a speed detector based on a detection signal of a position detector provided on a moving member operated by a mold clamping cylinder.

Further, according to the hydraulic control method for a mold clamping device of the present invention, a cylinder pressure chamber defined by sandwiching a piston of a mold clamping cylinder is communicated with a discharge pipe line connected to a variable displacement pump and a tank. Connected to a discharge line to be connected to each other via a direction switching valve, and provided with an electromagnetic proportional switching valve for controlling a discharge flow rate of a variable displacement pump in the discharge line; A brake valve and a throttle are provided in parallel, and when the approach position of the molds is detected, the electromagnetic proportional switching valve is switched to switch from high speed to low speed, and the brake valve is switched. In a hydraulic control method for a mold clamping device configured to perform a brake operation, a pressure of a discharge pressure oil of a variable displacement pump supplied to the mold clamping cylinder is detected to operate the mold clamping cylinder. There when switching from high speed to low speed, at the time the pressure at a required rate from the pressure of pressure oil discharged at high speed is reduced, it can also be adapted to operate switch the brake valve.

In this case, the pressure of the discharge pressure oil of the variable displacement pump is detected by a detection signal detected by a pressure detector provided near a pump discharge port of a discharge pipe or feedback control supplied to a control system of the variable displacement pump. it can be obtained as signals.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for controlling a hydraulic pressure of a mold clamping device according to the present invention will be described in detail with reference to the accompanying drawings. For convenience of description, the same components as those of the conventional structure shown in FIG. 5 are denoted by the same reference numerals, and detailed description will be omitted.

In FIG. 1, reference numeral 10 denotes a mold clamping cylinder. The mold clamping cylinder 10 defines an A chamber by a piston 10a and a B chamber into which a piston rod 10b is inserted. Is connected to a movable die plate 52a that supports the movable mold 50a. In FIG. 1, reference numeral 50b denotes a fixed mold, 52b denotes a fixed die plate, and 54 denotes a tie bar.

On the other hand, a hydraulic control circuit for controlling the mold clamping cylinder 10 includes a variable displacement pump 12, and a discharge line 13 of the variable displacement pump 12 is connected to the mold via an electromagnetic proportional switching valve 56. It is communicatively connected to a directional control valve 58 having four ports and three positions for selectively supplying and discharging pressure oil to the chamber A or chamber B of the tightening cylinder 10.

A discharge line 22 for selectively discharging the pressure oil from the chamber A or B of the mold clamping cylinder 10 through the direction switching valve 58 is provided. The two-position switching type brake valve 60 and the throttle 62 are connected and arranged in parallel and communicate with the tank T, respectively.

In the present invention, however, a rotary encoder 64 as a position detector is attached to a part of the piston rod 10b, and the opening / closing operation in the mold clamping operation is performed by a position signal obtained from the rotary encoder 64. It is set to detect the relative positions of the molds.

Therefore, in this embodiment, based on the detected position in the mold clamping operation obtained by the rotary encoder 64, the mold clamping cylinder 10 is switched from high-speed movement to low-speed movement, and an appropriate brake operation is started. Through the controller 66 to the electromagnetic proportional switching valve 5
6 and the operation of the brake valve 60 are controlled. In this case, the controller 66 includes a mold position comparison calculator 68.
And a first control system C1 for energizing the electromagnetic proportional switching valve 56 via the control amplifier 70, and a second control system C1 for energizing the brake valve 60 via the speed detector 72, the comparator 74, and the switching control circuit 76. And two control systems C2. It should be noted that a setting unit 78 capable of externally inputting and setting appropriate set values to the mold position comparison operation unit 68 of the first control system C1 and the comparison operation unit 74 of the second control system C2. Is provided.

Next, the controller 66 having the above configuration
A method for controlling the mold clamping device by using will be described with reference to FIG.

First, the direction switching valve 58 is switched from the illustrated neutral position to the side a. At this time, in the mold position comparison calculator 68 of the controller 66, a rotary encoder 6
4 is compared with the approach position of the dies in the mold clamping operation set in advance by the setting device 78 , and the control amplifier 70 is operated until the position detection signal matches the set value. , The electromagnetic proportional switching valve 56 is urged to switch the electromagnetic proportional switching valve 56 to the f side, and the pressure oil discharged from the variable displacement pump 12 is supplied to the A chamber of the mold clamping cylinder 10 through the direction switching valve 58. And mold clamping cylinder 1
0 indicates that the mold clamping operation is performed at a high speed.

Next, in the first control system C1 of the controller 66, when the value detected by the rotary encoder 64 matches the set value, the control amplifier 7
The urging of the electromagnetic proportional switching valve 56 is released via 0 , and the electromagnetic proportional switching valve 56 is switched to the e side. Thereby, the discharge amount of the pressure oil from the variable displacement pump 12 is limited, and the mold clamping cylinder 10 is switched to the mold clamping operation at a low speed. At this time, the brake valve 60 is held in the state shown in the figure, and the oil discharged from the chamber B of the mold clamping cylinder 10 is directly discharged to the tank T.

As described above, in the operation of switching the mold clamping cylinder 10 from high speed to low speed, the second control system C2 of the controller 66 uses the speed detector based on the position detection signal obtained from the rotary encoder 64. The speed is detected by 72. In this case, the speed detection value obtained by the speed detector 72 and a set value B ( for example, 20% lower than at the time of high speed) lower than that at the time of high speed previously set by the setting unit 78 (see FIG. 3). Is compared by the comparison calculator 74, and when the decrease in the detected speed value matches the set value B , the brake valve 60 is energized via the switching control circuit 76, and the brake valve 60 Is switched to the d side. Thereby, the mold clamping cylinder 1
The discharged oil from the B room 0 is discharged to the tank T via the throttle 62, and the brake operation of the mold clamping cylinder 10 can be performed.

Therefore, according to the method of controlling the hydraulic pressure of the mold clamping apparatus of the present embodiment, as shown in FIG. When the decreasing speed is reduced at a required rate from the speed at the high speed, the brake valve 60 is urged to perform the braking operation, thereby preventing the occurrence of an impact and smoothly shifting to a low speed. And shortening and stabilization of the molding cycle time can be easily realized.

FIG. 2 shows another embodiment of the controller 66 shown in FIG. That is, in this case, the first control system C1 for performing the switching operation of the electromagnetic proportional switching valve 56
Are the same, and use the pressure detection value of the discharge oil of the variable displacement pump 12 instead of the speed detection value for the second control system C2 for performing the switching operation of the brake valve 60.

Therefore, in this embodiment, a pressure detector 80 is provided near the discharge port of the variable displacement pump 12 for the discharge pipe 13 of the variable displacement pump 12 (see FIG. 1).
2, the pressure of the discharge pressure oil is detected, and the pressure detection value of the discharge pressure oil is reduced at a required ratio from the pressure at the time of high speed previously set by the setting device 78 (for example, 20% lower than the pressure at the time of high speed). The set value is compared with a set value by a comparison calculator 74 ', and when the detected pressure value matches the set value, the brake valve 60 (FIG. 1) is energized via the switching control circuit 76'.
The brake valve 60 is switched to the d side. With such a configuration, similarly to the above-described embodiment,
The brake operation of the mold clamping cylinder 10 can be performed.

In this embodiment, in addition to the pressure detection by the pressure detector 80, for example, the variable displacement pump 1
A signal that supports the actual pressure of the discharge pressure oil of the variable displacement pump 12, such as a feedback control signal supplied to the second control system, can be used.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and many design changes can be made without departing from the spirit of the present invention.

[0040]

As described above, according to the hydraulic control method of the mold clamping device according to the present invention, the cylinder pressure chamber defined by the piston of the mold clamping cylinder is connected to the variable displacement pump. An electromagnetic proportional switching valve that connects the discharge pipe and a discharge pipe that is connected to the tank so as to selectively communicate with each other via a direction switching valve, and controls a discharge flow rate of a variable displacement pump to the discharge pipe. Along with the provision, a brake valve and a throttle are provided in parallel in the discharge line, and when the approach position of the molds is detected, the electromagnetic proportional switching valve is switched to perform switching from high speed to low speed, In a hydraulic control method for a mold clamping device configured to perform a brake operation by switching a brake valve, a moving speed of a mold by a mold clamping cylinder is detected, and the operation of the mold clamping cylinder becomes high. When switching from high speed to low speed, when the speed decreases at a required rate from the moving speed at high speed, the brake valve is switched to set the speed at high speed when switching the mold clamping cylinder from high speed to low speed. , The timing of the brake operation is appropriately set, the occurrence of impact is eliminated, and stable low-speed movement and a molding cycle time can be realized.

[Brief description of the drawings]

FIG. 1 is a hydraulic system diagram showing one embodiment of a mold clamping control device for implementing a hydraulic control method in a mold clamping device according to the present invention.

FIG. 2 is a control system diagram showing another embodiment of the controller in the mold clamping control device shown in FIG.

FIG. 3 is a graph of a brake characteristic according to a hydraulic control method for a mold clamping device according to the present invention.

FIG. 4 is a diagram showing a brake characteristic diagram according to a conventional hydraulic control method for a mold clamping device.

FIG. 5 is a hydraulic system diagram showing a configuration example of a mold clamping control device that implements a hydraulic control method in a conventional mold clamping device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Mold-clamping cylinder 10a Piston 10b Piston rod 12 Variable displacement pump 13 Discharge pipeline 22 Discharge pipeline 50a Moving die 50b Fixed die 52a Moving die plate 52b Fixed die plate 54 Tie bar 56 Electromagnetic proportional switching valve 58 Directional control valve Reference Signs List 60 brake valve 62 throttle 64 position detector (rotary encoder) 66 controller 68 mold position comparison calculator 70 control amplifier 72 speed detector 74 comparison calculator 76 switching control circuit 78 setting device 80 pressure detector T tank C1 first Control system C2 Second control system

Claims (4)

(57) [Claims] 1. A directional control valve for connecting a discharge line connected to a variable displacement pump and a discharge line connected to a tank to a cylinder pressure chamber defined with a piston of a mold clamping cylinder interposed therebetween. Connected selectively to communicate with each other, and an electromagnetic proportional switching valve for controlling the discharge flow rate of the variable displacement pump is provided on the discharge line, and a brake valve and a throttle are provided in parallel on the discharge line, A mold clamping device configured to switch the electromagnetic proportional switching valve to switch from high speed to low speed when detecting the approach position of the molds, and to switch the brake valve to perform a braking operation. In the hydraulic control method of the device, the moving speed of the mold by the mold clamping cylinder is detected, and when the operation of the mold clamping cylinder is switched from high speed to low speed, a required ratio is calculated from the moving speed at high speed. At the time the speed is decreased, the hydraulic control method of the mold clamping device, characterized in that the operating switch the brake valve. 2. The mold clamping device according to claim 1, wherein the moving speed of the mold is detected by a speed detector based on a detection signal of a position detector provided on a moving member operated by the mold clamping cylinder. Hydraulic control method. 3. A directional control valve for connecting a discharge pipe connected to a variable displacement pump and a discharge pipe connected to a tank to a cylinder pressure chamber defined with a piston of a mold clamping cylinder interposed therebetween. Connected selectively to communicate with each other, and an electromagnetic proportional switching valve for controlling the discharge flow rate of the variable displacement pump is provided on the discharge line, and a brake valve and a throttle are provided in parallel on the discharge line, A mold clamping device configured to switch the electromagnetic proportional switching valve to switch from high speed to low speed when detecting the approach position of the molds, and to switch the brake valve to perform a braking operation. In the hydraulic control method of the device, the pressure of the discharge pressure oil of the variable displacement pump supplied to the mold clamping cylinder is detected, and when the operation of the mold clamping cylinder switches from high speed to low speed, At the time the pressure at a required rate from the pressure of the discharge pressure oil decreases, the oil pressure control method of the mold clamping device, characterized in that the operating switch the brake valve. Pressure of the discharge pressure oil of 4. A variable displacement pump, the detection signal or variable capacitance feedback control signals supplied to the control system of the pump is detected by the pressure detector provided in the vicinity of the pump discharge port of the discharge pipe hydraulic control method of the mold clamping apparatus according to claim 3, wherein obtained as.