JP2009298064A - Hydraulic device of injection molding apparatus - Google Patents

Abstract

[PROBLEMS] To control the back pressure of an injection cylinder close to zero pressure, drive the injection cylinder at high speed, enable high-speed injection of resin, and reduce the number of electric motors and reduce the hydraulic pressure of an injection molding machine. Providing equipment.
In a metering process, a hydraulic motor is driven by a second hydraulic pump to rotate a screw. Then, the back pressure of the injection cylinder 1 is reduced to a low pressure close to zero by controlling the first hydraulic pump 2 that can rotate bidirectionally and discharge bidirectionally based on the output of the pressure sensor 9. Can be controlled. On the other hand, at the time of the injection process, the hydraulic oil from the second hydraulic pump 21 is joined to the first main line 5 of the first hydraulic pump 2 via the joining line 24 and the check valve 28 by the second switching valve 25, The injection cylinder 1 is driven at high speed.
[Selection] Figure 1

Description

  The present invention relates to a hydraulic device for an injection molding machine and a control method therefor.

  Conventionally, as a hydraulic device of an injection molding machine, a screw for an injection cylinder is driven by a first servo electric motor for a screw at the time of a metering process, and is used for back pressure control capable of rotating in both directions and discharging in both directions. There is one in which a hydraulic pump is controlled to rotate forward and backward by a second servo electric motor (Patent Document 1: Japanese Patent Laid-Open No. 2008-30379). In the hydraulic apparatus of this injection molding machine, during the injection pressure holding process, the hydraulic pressure pump for injection pressure holding is driven by the third servo electric motor to supply hydraulic oil to the injection cylinder.

  Since the hydraulic device of this conventional injection molding machine controls the hydraulic pump for back pressure control that can rotate in both directions and discharge in both directions during the metering process, the second servo electric motor controls forward and reverse rotation. There is an advantage that the back pressure of the injection cylinder can be controlled close to zero pressure (0 Mpa).

  However, in the hydraulic device of the conventional injection molding machine, since the hydraulic oil from only the injection holding pressure hydraulic pump is supplied to the injection cylinder during the injection process, the injection cylinder cannot be driven at high speed, There is a problem that high speed injection is not possible.

In the conventional hydraulic apparatus of the injection molding machine, the first servo electric motor for the screw, the second servo electric motor for the hydraulic pump for back pressure control, and the second servo electric motor for the injection holding pressure hydraulic pump. Since a total of three servo electric motors with three servo electric motors are required, there is a problem that it is very expensive.
JP 2008-30379 A

Therefore, the problem of the present invention is that the back pressure of the injection cylinder can be controlled close to zero pressure (0 Mpa), the injection cylinder can be driven at high speed, the resin can be injected at high speed, and the number of electric motors is small. Another object of the present invention is to provide a hydraulic device for an injection molding machine that is inexpensive.

In order to solve the above problems, a hydraulic device for an injection molding machine of the present invention is
An injection cylinder having an injection piston and a screw for partitioning the housing into a front chamber and a rear chamber;
A first hydraulic pump capable of rotating in both directions and discharging in both directions;
A first electric motor for driving the first hydraulic pump at a variable speed forward and backward;
The first main line connected to the first hydraulic pump is switched and connected to a first load line connected to the front chamber of the injection cylinder or a second load line connected to the rear chamber of the injection cylinder. A first switching valve;
A hydraulic motor for driving the screw;
A second hydraulic pump;
A second electric motor for driving the second hydraulic pump;
A second switching valve that switches and connects a second main line connected to the second hydraulic pump to a merging line that merges with the first main line or a third load line that is connected to the hydraulic motor;
A check valve provided in the merging line so that a flow from the second main line to the first main line is in a forward direction;
And a pressure sensor for detecting the pressure of the first main line.

  According to the above configuration, the second switching valve connects the second main line of the second hydraulic pump to the third load line of the hydraulic motor, drives the hydraulic motor, and rotates the screw during the metering process. At the same time, the second switching valve shuts off between the second main line and the merging line, while rotating bidirectionally based on the output of the pressure sensor that detects the pressure of the first main line. By rotating the first hydraulic pump capable of discharging in a bidirectional manner, the pressure in the rear chamber of the injection cylinder, that is, the back pressure is reduced to zero through the first main line, the first switching valve, and the second load line. The pressure can be controlled to a low pressure close to the pressure (0 Mpa).

  On the other hand, during the injection process, the second switching valve connects the second main line of the second hydraulic pump to the merging line, and the hydraulic oil from the second hydraulic pump passes through the merging line and the check valve. The resin can be injected at high speed by joining the first main line of the hydraulic pump and supplying the injection cylinder via the first switching valve to drive the injection cylinder at high speed.

  Furthermore, in the hydraulic apparatus for an injection cylinder according to the present invention, the electric motor only requires two electric motors, the first electric motor and the second electric motor, and the number of electric motors required is small, and the manufacturing cost is reduced. .

  Moreover, according to the hydraulic apparatus for an injection cylinder of the present invention, the rotational speeds of the first and second hydraulic pumps may be controlled, so that the control becomes simple.

One embodiment is:
Pressure flow control that receives one pressure command, one flow command, and a signal representing the detected pressure from the pressure sensor, and outputs an operation amount for obtaining a pressure and a flow corresponding to the pressure command and the flow command. And
When the operation amount is received from the pressure flow control unit and the operation amount is equal to or less than a predetermined set value, the first hydraulic pump supplies hydraulic oil whose flow rate continuously changes according to the operation amount. While discharging, the first and second distribution operation amounts are created based on the operation amount so that the second hydraulic pump does not discharge the hydraulic oil, and output to the first and second electric motors, When the operation amount exceeds the set value, each of the first and second hydraulic pumps is such that the total flow rate of the discharge flow rates of the first and second hydraulic pumps changes continuously according to the operation amount. A control device is provided that includes an operation amount distribution unit that generates the first and second distribution operation amounts based on the operation amount and outputs the first and second distribution operation amounts to the first and second electric motors so as to discharge the hydraulic oil.

  According to the embodiment, the pressure flow control unit receives one pressure command, one flow command, and a signal representing the detected pressure from the pressure sensor, and receives a pressure corresponding to the pressure command and the flow command. And an operation amount for obtaining a flow rate is output to the operation amount distribution unit.

  When the operation amount is equal to or less than a predetermined set value, the operation amount distribution unit discharges the hydraulic oil at a flow rate that the first hydraulic pump continuously changes according to the operation amount. The first and second distribution operation amounts are created based on the operation amounts so that the second hydraulic pump does not discharge the hydraulic oil, and output to the first and second electric motors, respectively. When the set value is exceeded, the first and second hydraulic pumps discharge the hydraulic oil so that the total flow rate of the discharge flow rates of the first and second hydraulic pumps changes continuously according to the operation amount. As described above, the first and second distribution operation amounts are created based on the operation amount and output to the first and second electric motors, respectively.

  Thus, according to this embodiment, since only two commands, that is, one pressure command and one flow rate command, are required, the control becomes simpler than in the prior art.

  In the conventional example, the speed command of the first servo electric motor for the screw, the pressure command of the second servo electric motor for back pressure control of the injection cylinder, and the pressure command of the third servo electric motor for injection holding pressure control And four commands, the flow rate command, were necessary.

  Further, according to this embodiment, the first and second created by merging the discharge flow rate from the first hydraulic pump and the discharge flow rate from the second hydraulic pump and distributing the operation amount by the operation amount distribution unit. Since the first and second hydraulic pumps are controlled according to the distribution operation amount, no shock occurs when switching between the independent operation and the merged operation, and the transition between the isolated operation and the merged operation can be made smooth. .

  Further, according to this embodiment, since the operation amount distribution unit is provided at the subsequent stage of the pressure flow control unit, when the flow rate is reduced to a predetermined value or less by the pressure flow control unit, Since the operation of the second hydraulic pump stops, energy saving can be achieved.

In one embodiment,
The control device receives an identification signal for identifying an injection pressure holding process and a weighing process,
The control device
A switch device that is switched by an identification signal that identifies the injection pressure holding process and the metering process,
The switch device is
During the injection pressure holding process, the first distribution operation amount and the second distribution operation amount from the operation amount distribution unit are output to the first electric motor and the second electric motor as a first speed signal and a second speed signal, respectively. While
During the metering process, in order to control the back pressure of the injection cylinder, a pressure signal created based on the pressure command and the detected pressure is output to the first electric motor as a first speed signal, and the pressure The flow rate command bypassing the flow rate control unit and the operation amount distribution unit is output to the second electric motor as a second speed signal.

  According to the embodiment, the switch device is switched by the identification signal, and the first distribution operation amount and the second distribution operation amount from the operation amount distribution unit are respectively set to the first speed signal during the injection pressure holding process. And it outputs to a 1st electric motor and a 2nd electric motor as a 2nd speed signal. On the other hand, during the metering process, in order to control the back pressure of the injection cylinder, the switch device uses the pressure signal generated based on the pressure command and the detected pressure as the first speed signal as the first electric motor. While outputting to a motor, the said flow rate command which bypassed the said pressure flow control part and the operation amount distribution part is output to a said 2nd electric motor as a 2nd speed signal.

  Thus, the switch device is switched by the identification signal, and the first and second distribution operation amounts are output as the first and second speed signals in the injection pressure holding process, while in the weighing process, Since the pressure signal and the flow rate command are output as the first speed signal and the second speed signal, the control and structure are simple and inexpensive.

In one embodiment,
The control device
A first controller for controlling the first electric motor, comprising the pressure flow control unit, the operation amount distribution unit, and the switch device;
And a second controller that receives the second speed signal from the first controller and controls the second electric motor.

  According to the embodiment, the second controller receives the second speed signal from the first controller and controls the second electric motor, so that the structure of the second controller is simple and inexpensive.

  Since the control device is composed of a first controller and a second controller, the first controller and the second controller are separated into one unit unit, so that repair, replacement, and handling are facilitated. .

  However, it is possible to make the first controller and the second controller integral.

In one embodiment,
The switch device is
A first switch for outputting the first speed signal from an output terminal;
A second switch for outputting the second speed signal from an output terminal;
The first input operation amount distributed from the operation amount distribution unit is input to the first input terminal of the first switch, while the pressure command and the second input terminal of the first switch are input to the first input terminal of the first switch. The pressure signal created based on the detected pressure is input,
The second distribution operation amount distributed from the operation amount distribution unit is input to the first input terminal of the second switch, while the flow rate command is input to the second input terminal of the second switch. And
During the weighing process, the second input terminal and the output terminal of the first switch are connected by the identification signal, and the pressure signal created based on the pressure command and the detected pressure is used as the first speed signal. Input to the first electric motor, and a second input terminal and an output terminal of the second switch are connected, and the flow rate command is transmitted as the second speed signal to the second through the second switch. Input to the electric motor.

  According to the embodiment, since the second input terminal and the output terminal of the first switch are connected by the identification signal at the time of the weighing step, the above-mentioned created based on the pressure command and the detected pressure Since the pressure signal can be input to the first electric motor as the first speed signal and the second input terminal and the output terminal of the second switch are connected, the flow rate command is sent via the second switch. The pressure flow control unit and the operation amount distribution unit can be bypassed and input to the second electric motor as the second speed signal.

In one embodiment,
The hydraulic motor is a hydraulic motor that can rotate in both directions,
The second hydraulic pump is a pump that can rotate bidirectionally and discharge bidirectionally.

The control method of the hydraulic device of the injection molding machine of this invention is
During the injection pressure-holding process, the hydraulic oil from the second hydraulic pump is joined to the hydraulic oil from the first hydraulic pump that rotates in both directions and can be discharged in both directions via the second switching valve and the check valve. And supplying the joined hydraulic oil to the injection cylinder via the first switching valve,
During the metering step, hydraulic oil is supplied from the second hydraulic pump to the hydraulic motor that drives the screw of the injection cylinder via the second switching valve to drive the screw, and the check valve and the second While the second switching valve shuts off the hydraulic pump, the back pressure of the injection cylinder is rotated in both directions and the rotation of the first hydraulic pump capable of discharging in both directions is controlled forward and reverse. It can be controlled to a low pressure close to zero pressure.

  According to this invention, the back pressure of the injection cylinder can be controlled close to zero pressure, the injection cylinder can be driven at high speed, the resin can be injected at high speed, and the number of electric motors can be reduced, An inexpensive hydraulic device for an injection cylinder can be provided.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  As shown in FIG. 1, the injection cylinder 1 includes an injection piston 11 and a screw 12 in a housing 10. The injection piston 11 partitions the front chamber 13 and the rear chamber 14 in the housing 10.

  The housing 10 is provided with an injection port 15 and a hopper 16 so that pellets made of a resin material can be put into the housing 10 from the hopper 16.

  On the other hand, the first hydraulic pump 2 composed of a fixed displacement hydraulic pump that rotates in both directions and can discharge in both directions is driven at a forward / reverse variable speed by a first electric motor 3 composed of a servo electric motor, for example. Yes.

  A first main line 5 is connected to the first hydraulic pump 2, and a first switching valve 8 is connected to the first main line 5. The first switching valve 8 switches and connects the first main line 5 to the first load line 6 or the second load line 7. The first load line 6 communicates with the front chamber 13 of the injection piston 11, and the second load line 7 communicates with the rear chamber 14 of the injection cylinder 1. Reference numeral 4 denotes a tank.

  A pressure sensor 9 is connected to the first main line 5. The pressure sensor 9 outputs a signal representing the detected pressure of the first main line 5 to the first controller 31.

  The first controller 31 includes one pressure command Pi, one flow rate command Qi, an identification signal Di for identifying an injection pressure holding process or a metering process, and a signal representing a detected pressure from the pressure sensor 9. In response, the rotational speed and direction of the first electric motor 3 are controlled to a variable speed. The identification signal Di is a binary signal. For example, “High” represents an injection pressure holding process, and “Low” represents a measurement process.

  The second hydraulic pump 21 is driven by a second electric motor 22 made of, for example, a servo electric motor. Note that the second hydraulic pump 21 and the second electric motor 22 may rotate in only one direction.

  A second main line 23 is connected to the second hydraulic pump 21, and a second switching valve 25 is connected to the second main line 23. The second switching valve 25 switches and connects the second main line 23 to a merging line 24 connected to the first main line 5 or a third load line 26. The junction line 24 is provided with a check valve 28 in which the flow from the second main line 23 to the first main line 5 is in the forward direction, and no back flow from the first main line 5 to the second main line 23 occurs. I am doing so. A metering hydraulic motor 18 is connected to the third load line 26, and the screw 12 of the injection cylinder 1 is driven to rotate by the hydraulic motor 18. The metering hydraulic motor 18 may rotate only in one direction.

  On the other hand, the second electric motor 22 is driven by the second controller 32. The second controller 32 receives the second speed signal V <b> 2 from the first controller 31.

  The first controller 31 and the second controller 32 constitute a control device 30.

  As shown in FIG. 3, the first controller 31 of the control device 30 includes a pressure flow control unit 40, an operation amount distribution unit 50, a switch device 60, and a first driver 71. The second controller 32 includes a second driver 72.

  The pressure flow control unit 40 of the first controller 31 includes a joining point 42, a pressure control calculation unit 43, and a speed limiter 45.

  The addition point 42 outputs a signal obtained by subtracting the detected pressure from the pressure sensor 9 from the pressure command Pi to the pressure control calculation unit 43.

  The pressure control calculation unit 43 receives a signal from the summing point 42 and performs, for example, PID (proportional integral differentiation) control calculation and outputs the obtained pressure signal Vp to the speed limiter 45. However, the pressure control calculation unit 43 may perform other known pressure control calculations such as a PI (proportional integral) control calculation.

  The speed limiter 45 receives the pressure signal Vp from the pressure control calculation unit 43 and the flow rate command Qi, limits the pressure signal Vp so as not to exceed a value corresponding to the flow rate command Qi, The operation amount Vq is output.

That is, the speed limiter 45 obtains the manipulated variable Vq from the pressure signal Vp by the following algorithm.
Vp ≤ Qi → Vq = Vp
Qi <Vp → Vq = Qi

  As described above, the operation amount Vq is obtained by limiting the pressure signal Vp from the pressure control calculation unit 43 so as not to exceed the value according to the flow rate command Qi. And the flow rate can be controlled. More specifically, when the pressure signal Vp ≦ the flow rate command Qi, the operation amount Vq = the pressure signal Vp, and the pressure control is performed. On the other hand, when the flow rate command Qi <the pressure signal Vp, the operation amount Vq = the flow rate command Qi. Thus, the flow rate is automatically controlled.

On the other hand, the operation amount distribution unit 50 distributes the operation amount Vq into the first distribution operation amount Vq1 and the second distribution operation amount Vq2 by the following algorithm.
Vq ≤ Vmax1 → Vq1 = Vq, Vq2 = 0
Vmax1 <Vq → Vq1 = Vmax1, Vq2 = Vq-Vmax1

  That is, when the operation amount Vq is equal to or lower than a predetermined set value, for example, the maximum speed Vmax1 of the first electric motor 3, the operation amount distribution unit 50 calculates the operation amount Vq as shown in FIG. While outputting as the 1st distribution operation amount Vq1, as shown in FIG. 5, the 2nd distribution operation amount Vq2 which is zero is output. On the other hand, when the manipulated variable Vq exceeds the set value Vmax1, the highest speed Vmax1 is output as the first distributed manipulated variable Vq1, as shown in FIG. 4, and as shown in FIGS. A value (Vq−Vmax1) obtained by subtracting the set value Vmax1 from the operation amount Vq is output as the second distribution operation amount Vq2.

  In FIG. 4, Vq1max represents the maximum value of the first distribution operation amount Vq1, and in FIG. 5, Vq2max represents the maximum value of the second distribution operation amount Vq2.

  Thus, when the operation amount Vq is equal to or less than the maximum speed Vmax1 of the first electric motor 3, that is, when the flow rate command Qi is equal to or less than 40% of the maximum flow rate in FIG. The operation amount Vq is set to the first distribution operation amount Vq1, the second distribution operation amount Vq2 is set to zero, and the first distribution operation amount Vq1 (V1) using only the first electric motor 3 as the first speed signal V1, as will be described later. = Vq = Vq1) and the second electric motor 22 is stopped at the second distribution operation amount Vq2 (V2 = Vq2 = 0) as the second speed signal V2 to achieve energy saving.

  Here, the ratio between the maximum rotation speed Vmax1 of the first electric motor 3 and the maximum rotation speed Vmax2 of the second electric motor 22 is 4: 6, and the discharge of the first hydraulic pump 3 and the second hydraulic pump 21 is performed. Since the capacities Vcc are the same, switching between the single operation and the merge operation is performed at a location where the flow rate command Qi is 40% of the maximum merge flow rate divided by Vmax1 × Vcc: Vmax2 × Vcc = 4: 6. It is said. However, switching between the single operation and the merge operation is not limited to 40%, and may be performed at an arbitrary% such as 50% or 60% depending on the capacity of each hydraulic pump and the maximum rotation speed of the motor.

  6 to 8, the flow rate command, the flow rate, and the pressure are both expressed as% of the maximum value, the broken line represents the flow rate of the first hydraulic pump 2, and the alternate long and short dash line represents the flow rate of the second hydraulic pump 21. The solid line represents the total flow rate of the first and second hydraulic pumps 2 and 21.

  On the other hand, when the manipulated variable Vq exceeds the maximum speed Vmax1 of the first electric motor 3, the manipulated variable distributing unit 50, that is, the flow command corresponding to the manipulated variable in FIG. 6 exceeds 40% of the maximum combined flow. When the first distribution operation amount Vq1 is set to the maximum value Vq1max, that is, the maximum speed Vmax1, the first electric motor 3 is driven at the maximum speed Vmax1, and the second electric motor 22 is driven to the second distribution operation amount Vq2 ( Vq2 = Vq−Vmax1).

  Thus, when the operation amount Vq is equal to or less than the maximum speed Vmax1 of the first motor 12, the operation amount distribution unit 50 is driven with the first distribution operation amount Vq1 (Vq1 = Vq), while the operation amount Vq is the first amount. When the maximum speed Vmax1 of the first electric motor 3 is exceeded, the first electric motor 3 is driven at the maximum speed Vmax1 and the second electric motor 22 is driven at the second second distribution operation amount Vq2 (Vq2 = Vq−Vmax1). FIG. 6 shows a transition from the single operation in which the hydraulic oil is discharged only from the first hydraulic pump 2 to the merging operation in which the hydraulic oil from the first and second hydraulic pumps 2 and 21 is merged. As such, it can be smooth and free from shock.

  Further, as described above, the operation amount distribution unit 50 can obtain the first and second distribution operation amounts Vq1 and Vq2 by a simple calculation.

  On the other hand, the switch device 60 includes a first switch 61 and a second switch 62.

  The first distribution operation amount Vq1 from the operation amount distribution unit 50 is input to the first input terminal 61a of the first switch 61, and the pressure signal Vp from the pressure control calculation unit 43 is input to the second input terminal 61b. Enter. A first driver 71 is connected to the output terminal 61 c of the first switch 61.

  The second distribution operation amount Vq2 from the operation amount distribution unit 50 is input to the first input terminal 62a of the second switch 62, and the flow rate command Qi is input to the second input terminal 62b. A second driver 72 of the second controller 32 is connected to the output terminal 62 c of the second switch 62.

  The first driver 71 drives the first electric motor 3 and receives a signal representing the rotation speed of the first electric motor 3 from the encoder 81. Similarly, the second driver 72 drives the second electric motor 22 and receives a signal representing the rotation speed of the second electric motor 22 from the encoder 82.

  The hydraulic apparatus of the injection molding machine having the above configuration operates as follows.

  Now, it is assumed that the hydraulic apparatus of this injection molding machine performs the weighing process shown in FIG.

  At this time, as shown in FIG. 2, the first switching valve 8 is located at the symbol position S1, connects the first main line 5 to the second load line 7, rotates in both directions, and discharges in both directions. A possible first hydraulic pump 2 is connected to the rear chamber 14 of the injection cylinder 1. On the other hand, the second switching valve 8 is positioned at the symbol position S12, the second main line 23 is connected to the third load line 26, the second hydraulic pump 21 is connected to the metering hydraulic motor 18, and the second 2 Blocks between the main line 23 and the merge line 24.

  2 and 3, the identification signal Di shown in FIGS. 2 and 3 is “Low”, and the second input of the first switch 61 of the switch device 60 shown in FIG. 3 is determined by the identification signal Di. The terminal 61b is connected to the output terminal 61c, and the second input terminal 62b of the second switch 62 is connected to the output terminal 62c.

  In this state, one flow rate command Qi bypasses the pressure flow rate control unit 40 of the first controller 31 and the operation amount distribution unit 50 of the control device 30, and the second input of the second switch 62 of the switch device 60. A hydraulic pressure for metering from the second hydraulic pump 21 by driving the second electric motor 22 at a speed according to the flow rate command Qi, which is input to the second driver 72 via the terminal 62b and the output terminal 62c. Hydraulic oil is supplied to the motor 18 and the screw 12 is driven via the hydraulic motor 18 at a speed according to the flow rate command Qi.

  Simultaneously with the input of the single flow rate command Qi to the switch device 60, the single pressure command Pi is input to the joining point 42 of the pressure flow rate control unit 40 of the first controller 31 of the control device 30. The detected pressure from the pressure sensor 9 is subtracted from the pressure command Pi at the addition point 42, and the obtained signal is input from the addition point 42 to the pressure control calculation unit 43.

  The pressure control calculation unit 43 receives a signal from the summing point 42, performs PID (proportional integral differentiation) control calculation, and generates a pressure signal Vp. The pressure signal Vp is input to the first driver 71 via the second input terminal 61b and the output terminal 61c of the first switch 61, and drives the first electric motor 3 in both forward and reverse directions. The first hydraulic pump 2 that rotates in the direction and can be discharged in both directions is driven in both directions to control the discharge pressure, thereby controlling the pressure in the rear chamber 14 of the injection cylinder 1, that is, the back pressure.

  At this time, the first hydraulic pump 2 that rotates in both directions and can discharge in both directions is driven in both forward and reverse directions by the first electric motor 3 so that the first hydraulic pump 2 operates as a pump or a motor. Therefore, the back pressure in the rear chamber 14 of the injection cylinder 1 can be controlled to a very low pressure in the vicinity of 0 MPa.

  Next, it is assumed that the injection pressure holding process shown in FIG. 1 is performed.

  At this time, as shown in FIG. 1, the first switching valve 8 is located at the symbol position S <b> 1, the first main line 5 is connected to the second load line 7, and the first hydraulic pump 2 is connected to the injection cylinder 1. Connect to rear chamber 14. The second switching valve 8 is located at the symbol position S11, connects the second main line 23 to the merging line 24, and connects the second hydraulic pump 21 to the first main line 5. As a result, the discharge hydraulic oil from the second hydraulic pump 21 can merge with the discharge hydraulic oil from the first hydraulic pump 2 via the merge line 24 and the check valve 28.

  Also, during this injection pressure holding process, the identification signal Di shown in FIGS. 1 and 3 is “High”, and the first switch 61 of the first switch 61 of the switch device 60 shown in FIG. The first input terminal 61a is connected to the output terminal 61c, and the first input terminal 62a of the second switch 62 is connected to the output terminal 62c.

  In this state, one pressure command Pi is input to the joining point 42 of the pressure flow control unit 40 of the first controller 31 of the control device 30. The detected pressure from the pressure sensor 9 is subtracted from the pressure command Pi at the addition point 42, and the obtained signal is input from the addition point 42 to the pressure control calculation unit 43.

  The pressure control calculation unit 43 receives a signal from the summing point 42, performs PID (proportional integral differentiation) control calculation, and generates a pressure signal Vp. This pressure signal Vp is input to the speed limiter 45.

  The speed limiter 45 restricts the pressure signal Vp from the pressure control calculation unit 43 so as not to exceed a value corresponding to the flow rate command Qi to obtain an operation amount Vq. It is input to the quantity distribution unit 50. Thus, when the pressure signal Vp ≦ the flow rate command Qi, the pressure is controlled as the operation amount Vq = pressure signal Vp, while when the flow rate command Qi <the pressure signal Vp, the operation amount Vq = the flow rate command Qi is automatically set. The flow rate is controlled.

The operation amount distribution unit 51 calculates the first and second distribution operation amounts Vq1 and Vq2 by the following speed distribution algorithm based on the operation amount Vq and the maximum speed Vmax1 of the first motor 3 as a set value. create.
Vq ≤ Vmax1 → Vq1 = Vq, Vq2 = 0
Vmax1 <Vq → Vq1 = Vmax1, Vq2 = Vq-Vmax1

  That is, when the operation amount Vq is equal to or lower than a predetermined set value, for example, the maximum speed Vmax1 of the first electric motor 3, the operation amount distribution unit 50 calculates the operation amount Vq as shown in FIG. While outputting as the 1st distribution operation amount Vq1, as shown in FIG. 5, the 2nd distribution operation amount Vq2 which is zero is output. On the other hand, when the manipulated variable Vq exceeds the set value Vmax1, the highest speed Vmax1 is output as the first distributed manipulated variable Vq1, as shown in FIG. 4, and as shown in FIGS. A value (Vq−Vmax1) obtained by subtracting the set value Vmax1 from the operation amount Vq is output as the second distribution operation amount Vq2.

  As described above, when the operation amount Vq is equal to or less than the maximum speed Vmax1 of the first electric motor 3, the operation amount distribution unit 50 performs the first distribution operation amount Vq1 and the second distribution as shown in FIGS. A manipulated variable Vq2 is obtained. That is, in FIG. 6, when the flow rate command corresponding to the manipulated variable Vq is 40% or less of the maximum flow rate after the discharge hydraulic fluids of the first and second hydraulic pumps 2 and 21 merge, the manipulated variable Vq is set to the first. The distribution operation amount Vq1, the second distribution operation amount Vq2 is set to zero, and only the first electric motor 3 is the first distribution operation amount Vq1 (V1 = Vq = Vq1) as the first speed signal V1, and the first switch 61 Driven via the first input terminal 61a, the output terminal 61c and the first driver 71, the second electric motor 22 is stopped at the second distribution operation amount Vq2 (V2 = Vq2 = 0) as the second speed signal V2. And achieve energy savings.

  4 and 5, when the operation amount Vq exceeds the maximum speed Vmax1 of the first electric motor 3, as shown in FIGS. 4 and 5, that is, the maximum flow command Qi in FIG. When the flow rate exceeds 40%, the first distribution operation amount Vq1 is set to the maximum speed Vmax1, while the second distribution operation amount Vq2 is set to Vq2 = Vq−Vmax1. The first electric motor 3 controls the first input terminal 61a, the output terminal 61c, and the first driver 71 of the first switch 61 with the first distribution operation amount Vq1 as the first speed signal V1 that is the maximum speed Vmax1. Driven through. As a result, the first hydraulic motor 3 is driven at the maximum speed Vmax1. On the other hand, the second electric motor 22 has the second distribution manipulated variable Vq2 (Vq2 = Vq−Vmax1) as the second speed signal V2, and the first input terminal 62a, the output terminal 62c, and the second driver 72 of the second switch 62. Driven through. As a result, the second hydraulic motor 21 is driven with the second distribution operation amount Vq2 (Vq2 = Vq−Vmax1) as the second speed signal V2.

  Therefore, the hydraulic oil from the second hydraulic pump 21 joins the hydraulic oil from the first hydraulic pump 2 to the injection cylinder 11 via the merge line 24 and the check valve 28, and The hydraulic oil and the hydraulic oil from the second hydraulic pump 21 are supplied to the injection cylinder 1 so that the injection cylinder 1 can be driven at a high speed and the resin can be injected at a high speed.

  Furthermore, when the operation amount Vq is equal to or less than the maximum speed Vmax1 of the first electric motor 3, the operation amount distribution unit 50 drives only the first electric motor 3 with the first distribution operation amount Vq1 as the first speed signal V1. On the other hand, when the operation amount Vq exceeds the maximum speed Vmax1 of the first electric motor 3, the first electric motor 3 is driven at the maximum speed Vmax1 which is the first distribution operation amount Vq1 as the first speed signal V1. Since the second electric motor 22 is driven by the second distribution operation amount Vq2 (Vq2 = Vq−Vmax1) as the second speed signal V2, from the single operation in which the hydraulic oil is discharged only from the first hydraulic pump 2, As shown in FIG. 6, the transition to the merging operation for merging the hydraulic oil from the first and second hydraulic pumps 2 and 21 can be made smooth so as not to cause a shock.

  Furthermore, in the hydraulic apparatus of this injection molding machine, an operation amount distribution unit 50 is provided after the pressure flow control unit 40 to distribute the operation amount Vq from the pressure flow control unit 40 as the first speed signal V1. The first distribution operation amount Vq1 and the second distribution operation amount Vq2 as the second speed signal V2 are created, and the first distribution operation amount Vq1 and the second distribution operation amount Vq2 are set as the first distribution operation amount Vq2. As shown in FIG. 8 which is an enlarged view of the main part of FIG. 7, the rotation of the second electric motor 22 is input to the first and second drivers 71 and 72 through the second switches 61 and 62. The speed gradually decreases, the discharge flow rate of the second hydraulic pump 21 gradually decreases from 90% of the maximum flow rate after joining, and the discharge flow rate becomes zero when the pressure is 96% of the maximum pressure. On the other hand, the first electric motor 3 rotates at a constant rotational speed until the pressure reaches 96% of the maximum pressure, and the discharge flow rate of the first hydraulic pump 2 is constant at 40% of the maximum flow rate after merging. When the pressure exceeds 96% of the maximum pressure, the rotation speed of the first electric motor 3 gradually decreases, and the discharge flow rate of the first hydraulic pump 2 gradually decreases from 40% of the maximum flow rate after merging. When the pressure is 100% of the maximum pressure, the discharge flow rate becomes zero.

  As described above, the operation amount distribution unit 50 provided in the subsequent stage of the pressure flow control unit 40 distributes the operation amount Vq from the pressure flow control unit 40, and the first speed signal V1 and the second speed signal V2 are obtained. Since the first and second distribution manipulated variables Vq1 and Vq2 are created, a cutoff characteristic (not shown) is provided with the cutoff characteristic shown in FIG. 7 (characteristic that gradually decreases the control flow rate as the maximum pressure is approached). In this case, as can be seen from FIG. 8 which is an enlarged view of FIG. 7, the operation of the second hydraulic pump 21 is stopped when the flow rate is reduced at a high pressure of 96% or more. Since the discharge amount of the pump 21 is zero when the pressure is in the range of 96 to 100%, energy saving can be achieved.

  If the flow command Qi is distributed before the pressure flow control unit 40, both the first hydraulic pump 2 and the second hydraulic pump 21 are driven until the pressure is just before 100%, thereby saving energy. Cannot be achieved.

  In the hydraulic apparatus for the injection cylinder of the above embodiment, the electric motor only needs two electric motors, the first electric motor 3 and the second electric motor 22, and the number of electric motors required is small and inexpensive. Has the advantage of saying.

  In addition, according to the hydraulic apparatus for the injection cylinder of this embodiment, since only two hydraulic pumps, the first and second hydraulic pumps 2 and 21, need to be controlled, the control becomes simple.

  Further, according to the hydraulic device for an injection cylinder of the above-described embodiment, since only two commands, that is, one pressure command Pi and one flow command Qi are required, four commands are necessary. Compared to the example, the control becomes easier. In the conventional example, the speed command of the first servo electric motor for the screw, the pressure command of the second servo electric motor for back pressure control of the injection cylinder, and the pressure command of the third servo electric motor for injection holding pressure control And four commands, the flow rate command, were necessary.

  Further, according to the hydraulic device for the injection cylinder of the above-described embodiment, the first switch 61 and the second switch 62 of the switch device 60 are switched by the identification signal Di that is a binary signal, and in the injection pressure holding process. The first and second distribution manipulated variables Vq1 and Vq2 are output as the first and second speed signals V1 and V2, while the pressure signal Vp and the flow rate command Qi are output as the first speed signal V1 and the second speed signal during the measuring step. Since it is output as the speed signal V2, the control and structure are simple and inexpensive.

  According to the injection cylinder hydraulic device of the above embodiment, the second controller 32 receives the second speed signal V2 from the first controller 31 and controls the second electric motor 22, so the structure of the second controller 32 is the same. Easy and cheap.

  Furthermore, according to the hydraulic apparatus for an injection cylinder of the above-described embodiment, since the control device 30 includes the first controller 31 and the second controller 32, the first controller 31 and the second controller 32 are separated from each other. One unit unit can be used, and repair, replacement, and handling become easy.

  Further, according to the hydraulic device for an injection cylinder of the above embodiment, the second input terminal 61b and the output terminal 61c of the first switch 61 are connected by the identification signal Di at the time of the metering process. The pressure signal Vp created based on the pressure detected by the pressure sensor 9 can be input to the first electric motor 3 as the first speed signal V1, and the second input terminal 62b and the output terminal 62c of the second switch 62 Therefore, the flow rate command Qi is input to the second electric motor 22 as the second speed signal V2 via the second switch 62, bypassing the pressure flow control unit 40 and the operation amount distribution unit 50. Can do.

  Moreover, according to the control method of the hydraulic apparatus of the injection molding machine of the above embodiment, the back pressure of the injection cylinder 1 can be controlled to a low pressure close to zero pressure, and the injection cylinder 1 can be driven at a high speed. High-speed injection can be performed, and the number of electric motors 3 and 22 can be reduced to two.

  In the hydraulic apparatus of the injection molding machine of the above embodiment, the first hydraulic pump 2 and the second hydraulic pump 21 are used. However, these third hydraulic pumps are used by using a third hydraulic pump, a fourth hydraulic pump, and the like. Discharge hydraulic fluid such as a pump and a fourth hydraulic pump may be joined to the first main line 5 via check valves, respectively.

  In the hydraulic apparatus for an injection molding machine according to the above-described embodiment, the second hydraulic pump 21 and the metering hydraulic motor 18 can rotate in both directions to discharge hydraulic oil in both directions. These may rotate in only one direction and discharge hydraulic oil in only one direction.

In the hydraulic apparatus for an injection molding machine according to the above embodiment, the operation amount distribution unit 50 is based on the operation amount Vq and the maximum speed Vmax1 of the first electric motor 3 as a predetermined set value.
Vq ≤ Vmax1 → Vq1 = Vq, Vq2 = 0
Vmax1 <Vq → Vq1 = Vmax1, Vq2 = Vq-Vmax1
The first and second distribution manipulated variables Vq1 and Vq2 are generated as the first and second speed signals V1 and V2 by the speed distribution algorithm. The set value is based on the maximum rotational speed Vmax1 of the first electric motor 3. May be a small value.

  In addition, the speed distribution algorithm of the operation amount distribution unit 50 is not limited to the above example. In short, when the operation amount Vq is equal to or less than a predetermined set value, the first hydraulic pump 2 operates the operation amount Vq. The first and second distribution operations as the first and second speed signals V1 and V2 are performed so that the hydraulic oil whose flow rate changes continuously according to the pressure and the second hydraulic pump 21 does not discharge the hydraulic oil. The amounts Vq1 and Vq2 are created based on the manipulated variable Vq. When the manipulated variable Vq exceeds the set value, the first and second hydraulic pumps 2 and 21 have a total flow rate corresponding to the manipulated variable Vq. As long as the first and second distribution manipulated variables Vq1 and Vq2 are created based on the manipulated variable Vq so as to discharge the hydraulic oil so as to continuously change, not only the above example but many A polyline with a bending point of Properties and it may be those which can be represented by like.

  In addition, the pressure flow control unit 40, the signal distribution unit 50, and the switch device 60 of the hydraulic device of the injection molding machine according to the above embodiment may be configured by software, or may be configured by a digital circuit. Or you may comprise with an analog circuit.

  Further, as the pressure sensor, a current sensor that detects the driving current of the first electric motor 3 and indirectly detects the pressure of the first main line 5 may be used.

FIG. 1 is a circuit diagram showing an injection pressure holding process of a hydraulic apparatus for an injection molding machine according to an embodiment of the present invention. FIG. 2 is a circuit diagram showing the metering process of the hydraulic apparatus of the injection molding machine according to the above embodiment. FIG. 3 is a block diagram of a control device of the hydraulic device of the injection molding machine according to the above embodiment. FIG. 4 is a graph showing the relationship between the operation amount and the first distribution operation amount. FIG. 5 is a graph showing the relationship between the operation amount and the second distribution operation amount. FIG. 6 is a diagram illustrating a flow rate characteristic between the flow rate command and the flow rate. FIG. 7 is a diagram showing a pressure flow characteristic between the pressure and the flow rate. FIG. 8 is an enlarged view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection cylinder 2 1st hydraulic pump 3 1st electric motor 5 1st main line 6 1st load line 7 2nd load line 8 1st switching valve 9 Pressure sensor 10 Housing 11 Injection piston 12 Screw 13 Front chamber 14 Rear chamber 18 Hydraulic motor 21 Second hydraulic pump 22 Second electric motor 23 Second main line 24 Junction line 26 Third load line 28 Check valve 30 Controller 31 First controller 32 Second controller 40 Pressure flow control unit 42 Joining point 43 Pressure Control calculation unit 45 Speed limiter 50 Operation amount distribution unit 60 Switch device 61 First switch 62 Second switch

Claims (7)

An injection cylinder (1) having an injection piston (11) and a screw (12) for partitioning the inside of the housing (10) into a front chamber (13) and a rear chamber (14);
A first hydraulic pump (2) capable of rotating in both directions and discharging in both directions;
A first electric motor (3) that drives the first hydraulic pump (2) in a variable speed forward and backward;
The first main line (5) connected to the first hydraulic pump (2), the first load line (6) connected to the front chamber (13) of the injection cylinder (1), or the injection cylinder (1) a first switching valve (8) that is switched and connected to a second load line (7) connected to the rear chamber (14);
A hydraulic motor (18) for driving the screw (12);
A second hydraulic pump (21);
A second electric motor (22) for driving the second hydraulic pump (21);
The second main line (23) connected to the second hydraulic pump (21) is connected to the merging line (24) joining the first main line (5) or the hydraulic motor (18). A second switching valve (25) for switching connection to the third load line (26);
A check valve (28) provided in the merging line (24) so that a flow from the second main line (23) to the first main line (5) is in a forward direction;
A hydraulic apparatus for an injection molding machine, comprising a pressure sensor (9) for detecting the pressure of the first main line (5). In the hydraulic apparatus of the injection molding machine according to claim 1,
One pressure command (Pi), one flow rate command (Qi), and a signal representing the detected pressure from the pressure sensor (9) are received, and according to the pressure command (Pi) and the flow rate command (Qi) A pressure flow control unit (40) for outputting an operation amount (Vq) for obtaining a pressure and a flow rate;
When the operation amount (Vq) is received from the pressure flow control unit (40) and the operation amount (Vq) is equal to or less than a predetermined set value, the first hydraulic pump (2) The first and second distribution operation amounts (Vq1 and Vq2) are set so that the hydraulic oil whose flow rate changes continuously according to Vq) and the second hydraulic pump (21) does not discharge the hydraulic oil. The first and second electric motors (3, 22) are created based on the manipulated variable (Vq) and output to the first and second electric motors (3, 22). When the manipulated variable (Vq) exceeds the set value, The first and second hydraulic pumps (2, 21) supply hydraulic oil so that the total flow rate of the discharge flow rate of the second hydraulic pump (2, 21) changes continuously according to the operation amount (Vq). The first and second distribution manipulated variables (Vq1 And a control device (30) having an operation amount distribution unit (50) that creates Vq2) based on the operation amount (Vq) and outputs it to the first and second electric motors (3, 22). A hydraulic device for an injection molding machine. In the hydraulic apparatus of the injection molding machine according to claim 2,
The control device (30) receives an identification signal (Di) for identifying an injection pressure holding process and a weighing process,
The control device (30)
A switch device (60) that is switched by an identification signal (Di) that identifies the injection pressure-holding step and the weighing step;
The switch device (60)
During the injection pressure holding process, the first distribution operation amount (Vq1) and the second distribution operation amount (Vq2) from the operation amount distribution unit (50) are respectively converted into a first speed signal (V1) and a second speed signal ( While V2) is output to the first electric motor (3) and the second electric motor (22),
During the measuring process, in order to control the back pressure of the injection cylinder (1), the pressure signal (Vp) created based on the pressure command (Pi) and the detected pressure is used as the first speed signal (V1). The flow rate command (Qi) that is output to the first electric motor (3) and bypasses the pressure flow rate control unit (40) and the operation amount distribution unit (50) is used as the second speed signal (V2). A hydraulic device for an injection molding machine, wherein the hydraulic device outputs to an electric motor (22). In the hydraulic apparatus of the injection molding machine according to claim 3,
The control device (30)
A first controller (31) that includes the pressure flow control unit (40), the operation amount distribution unit (50), and the switch device (60) to control the first electric motor (3);
A hydraulic apparatus for an injection molding machine comprising a second controller (32) for receiving the second speed signal (V2) from the first controller (31) and controlling the second electric motor (22). . In the hydraulic apparatus of the injection molding machine according to claim 3 or 4,
The switch device (60)
A first switch (61) for outputting the first speed signal (V1) from an output terminal;
A second switch (62) for outputting the second speed signal (V2) from an output terminal;
The first distribution operation amount (Vq1) distributed from the operation amount distribution unit (50) is input to the first input terminal of the first switch (61), while the first switch (61) The pressure signal (Vp) created based on the pressure command (Pi) and the detected pressure is input to the second input terminal,
The second distribution operation amount (Vq2) distributed from the operation amount distribution unit (50) is input to the first input terminal of the second switch (62), while the second switch (62) of the second switch (62). The flow rate command (Qi) is input to the second input terminal,
During the weighing process, the second input terminal and the output terminal of the first switch (61) are connected by the identification signal (Di), and are created based on the pressure command (Pi) and the detected pressure. The pressure signal (Vp) is input to the first electric motor (3) as a first speed signal (V1), and a second input terminal and an output terminal of the second switch (62) are connected, The hydraulic apparatus for an injection molding machine, wherein the flow rate command (Qi) is input to the second electric motor (22) as a second speed signal (V2) via the second switch (62). . In the hydraulic apparatus of the injection molding machine according to any one of claims 1 to 5,
The hydraulic motor (18) is a hydraulic motor (18) rotatable in both directions,
The hydraulic device of an injection molding machine, wherein the second hydraulic pump (21) is a pump capable of rotating in both directions and discharging in both directions. In the injection pressure holding process, hydraulic oil from the second hydraulic pump (21) is supplied to the second switching valve (25) to hydraulic oil from the first hydraulic pump (2) that can rotate bidirectionally and discharge bidirectionally. ) And the check valve (28), and the joined hydraulic oil is supplied to the injection cylinder (1) via the first switching valve (8).
During the metering process, hydraulic oil is supplied from the second hydraulic pump (21) to the hydraulic motor (18) that drives the screw (12) of the injection cylinder (1) via the second switching valve (25). The screw (12) is driven and the check valve (28) and the second hydraulic pump (21) are shut off by the second switching valve (25), while the injection cylinder (1) An injection molding machine characterized in that the back pressure is controlled to a low pressure close to zero pressure by controlling forward and reverse rotation of the first hydraulic pump (2) capable of rotating bidirectionally and discharging bidirectionally. Control method of the hydraulic system.

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