JPH10128820A - Driver for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a driver for alleviating a burden of designing, installing and maintenance almost without loss of power with a simple constitution by driving units for mold clamping, metering, injecting, nozzle moving and injecting of an injection molding machine by a hydraulic actuator. SOLUTION: A hydraulic actuator A20 of a secondary control system is utilized as a driving means of a mold clamping unit 20, metering unit 30, injecting unit 40 and nozzle moving unit 50 of the injection molding machine of the resin. A high pressure pipeline 6a directly communicates with a rod side port of a projecting cylinder 60. A directional switching valve 61 for switching communication between the pipeline 6a and a low pressure pipeline 6b is provided at a head side port. A large volume general purpose accumulator 68 is connected to the pipeline 6a, and a large capacity general purpose sealed tank 69 operating as a low pressure accumulator is connected to the pipeline 6b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for an injection molding machine for driving a mold clamping, metering, injection, nozzle movement, and ejection device of an injection molding machine for a resin or the like.

[0002]

2. Description of the Related Art Conventionally, a hydraulic circuit used for driving this type of injection molding machine is called a load-sensitive control of a variable displacement hydraulic pump. The discharge flow rate is automatically operated so that the pressure difference between the upstream and downstream of the flow control valve provided in the hydraulic circuit between each cylinder and the pressure control valve becomes constant.

FIG. 5 shows an example of a hydraulic circuit constituting a driving device of a conventional injection molding machine. Hydraulic pump 1
The flow rate of the hydraulic fluid discharged from 02 is controlled by the flow rate control valve 103. The pressurized liquid whose flow rate is controlled is supplied to a mold clamping cylinder 106 via a direction switching valve 104 for switching between mold clamping and mold opening and a direction switching valve 105 for high-speed mold clamping.
To the cylinder 108 via a direction switching valve 107 for ejector switching, a selector valve 109 for screw retraction and back pressure, and a direction switching valve 1 for injection and screw rotation.
Injection cylinder 1 with metering motor 111 via 10
12 is supplied to a nozzle moving cylinder 114 via a direction switching valve 113 for nozzle switching.

In operation of a conventional injection molding machine having such a hydraulic circuit, first, a metering motor 111 rotates a screw (not shown) to weigh resin into a heating cylinder. At this time, the injection cylinder 112 is retracted by the measured resin. Here, the injection cylinder 112 is slightly retracted to reduce the pressure of the measured resin. Nozzle moving cylinder 1
14 is retracted while cooling the resin of the previous cycle.

[0005] Next, the mold closing cylinder 106 is retracted to open the mold, the protruding cylinder 108 is advanced to take out the molded product of the previous cycle, and then the mold closing cylinder 106 is advanced to close the mold and the nozzle The moving cylinder 114 is advanced to press the nozzle against the mold. In this state, the injection cylinder 112 is advanced to start injection, and when the mold cavity is filled with resin, the hydraulic circuit pressure rises.

When this pressure rises to the primary injection pressure,
The electromagnetic relief valve 101 is actuated, and the hydraulic pump 102 automatically reduces the discharge flow rate to perform pressure control, and the pressure holds the resin. After the elapse of a certain time, the holding pressure is stopped, the injection pressure is released, and the operation from the first stroke is repeated.

Since the drive by such a hydraulic circuit device is load-sensitive control as described above, the variable displacement hydraulic pump 102 discharges a flow according to the opening of the flow control valve 103, and As a hydraulic device, the power loss can be reduced. The cylinders 106, 112, 114, and 108 for mold clamping, injection, nozzle movement, and protrusion, and the metering motor 111 are supplied and shut off by a directional switching valve formed of an electromagnetic valve.

[0008]

However, in such a conventional driving device for an injection molding machine, in order to control the speed of an actuator comprising each cylinder, the flow rate to be supplied is controlled by the discharge of a hydraulic pump. Since the amount was changed, a plurality of actuators could not be driven at the same time.

Further, the hydraulic circuit for controlling each actuator is extremely complicated and requires a great deal of knowledge and labor for the design and installation thereof. There is also a problem that a lot of labor and time are required for investigating and repairing the cause.

Further, since a large power must be supplied instantaneously when the mold and its holding machine are accelerated or when an instantaneous high load is applied in the injection stroke, the power supply device for power supply and the installation of electric wires and the like must be adjusted accordingly. Need to be big,
If only small power could be supplied, it could not be used. Even if a large amount of power can be supplied, cooling equipment is often required because the amount of generated heat increases, and malfunctions caused by generation of electromagnetic waves due to instantaneous current flowing, fluctuations in power supply voltage, and the like occur. There was a fear.

In addition, the kinetic energy is consumed at the time of deceleration of the mold and its holding machine, which not only results in energy loss, but also sometimes requires the installation of a brake valve, which complicates the apparatus and reduces the installation cost. It was also the cause of the rise. In particular, in a rigid molding machine, when the raised mold and the holding machine are lowered, all the potential energy is released as heat, and there is a problem that the energy loss becomes extremely large.

Furthermore, a large amount of hydraulic fluid must be stored in a tank, and the installation place is strictly regulated by the Fire Service Law and the like. It was troublesome. The present invention has been made in view of the above points, and an object of the present invention is to provide a drive device for an injection molding machine that has a simple configuration, has little power loss, and can reduce the burden of design, installation, and maintenance. .

[0013]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides at least one of a mold clamping, metering, injection, nozzle movement, and ejection device of an injection molding machine which generates a substantially constant pressure. A hydraulic pressure source device, a variable capacity hydraulic device connected to the hydraulic pressure source device, a capacity operating device for changing the capacity of the variable capacity hydraulic device, The present invention provides a drive device for an injection molding machine driven by a hydraulic actuator including a control device for sending an operation signal.

In the driving device for the injection molding machine, the hydraulic actuator includes an accumulator, a hydraulic circuit communicating from the accumulator to the variable displacement hydraulic device, and a check valve from a general-purpose hydraulic pressure source device. And a hydraulic circuit that flows through the accumulator through the accumulator, and it is preferable that the accumulator is fixed to the variable displacement hydraulic device.

[0015]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, FIG. 2 is an enlarged hydraulic circuit diagram showing a part of the hydraulic actuator, and FIG. 3 is an explanatory diagram showing various operating states of the hydraulic actuator. It is. First, a hydraulic actuator according to the present invention will be described with reference to FIG. This hydraulic actuator is usually equipped with a secondary control system or a constant pressure source system (CP
S). In FIG. 2, for convenience of illustration, the inertial object driven by acceleration / deceleration is shown as a weight 3 mechanically coupled to the output shaft 2 of the hydraulic motor 1.

A first port 1a provided in a variable displacement hydraulic motor (hereinafter simply referred to as a "hydraulic motor") 1, such as a swash plate type axial piston motor, is provided with a low-output motor 4 and A high-pressure hydraulic fluid of a pump unit including a driven pump 5 is supplied through a check valve 7 through a high-pressure line 6a, and a high-pressure hydraulic fluid from an accumulator 8, which is a hydraulic pressure source device having a pressure equal to or higher than a predetermined pressure, is supplied. The working fluid is supplied directly to the closed tank 9 from the second port 1b through the low-pressure line 6b.

The displacement of the hydraulic motor 1 is controlled by a control device 10.
Center type control valve 1 in response to an electric signal from
, First and second displacement control pistons 1 operating via
It is controlled by a volume operation device composed of 2 and 13.

The hydraulic motor 1, accumulator 8, closed tank 9, control device 10, control valve 11,
The hydraulic actuator A is constituted by the first and second displacement control pistons 12, 13 and the like. The first of the hydraulic motor 1
The second ports 1a and 1b are provided with first and second external connection ports C1 and C2 which can be connected from the outside, respectively, and the discharge port side high pressure line 6a and the suction port side low pressure line of the pump 5 are provided respectively. 6b.

The hydraulic actuator A having such a configuration is stored in the accumulator 8 from the pump 5 through the high-pressure line 6a and the check valve 7. The hydraulic motor 1 operates, and the necessary energy is supplied from the accumulator 8. When the braking of the hydraulic motor 1 is stopped, the kinetic energy of the weight 3 is recovered by the accumulator 8. The power required to drive the weight 3 in the meantime is only the power required to drive the hydraulic motor 1, excluding the leakage loss of the hydraulic fluid and the friction loss due to the drive, and the energy equivalent to the pump 5 is required. Supplied from

Thus, the hydraulic actuator A
Can not only effectively reuse the braking energy, but also supply the momentarily necessary energy from the accumulator 8, so that a small amount of power can be supplied constantly. A certain continuously variable transmission function can be realized.

The operation of the hydraulic actuator A will now be described with reference to FIG. Now, let T be the hydraulic motor 1
Shaft torque (Nm), U is the shaft rotation speed (rad / sec),
If V is the motor capacity per unit rotation (m ³ / rad), Q is the required flow rate (m ³ / sec), and P is the pressure of the working fluid (Pa), T = PV (Nm), Q = U · V (m ³ / sec). In the drawing, suffixes (+) and (-) indicate positive and negative.

In the state shown in FIG. 3A, the hydraulic fluid having the pressure P and the required flow rate Q from the accumulator 8 flows through the hydraulic motor 1 to the closed tank 9, and the hydraulic motor 1 has a positive shaft. A torque T (+) is generated, and the weight 3 has a shaft rotation speed U
(+) Indicates a forward rotation / acceleration state. From this state, as shown in FIG. 3 (c), when the motor capacity V per unit rotation of the hydraulic motor 1 becomes 0, the torque becomes 0, the acceleration becomes 0, and the weight 3 becomes a shaft. At the rotation speed U (+), the state becomes forward rotation / constant speed state. Since the flow rate Q at this time is 0, no power is used. Further, when the capacity V of the hydraulic motor 1 is made negative as shown in FIG. 3D, a negative shaft torque T (-) is generated in the hydraulic motor 1 and the weight 3 is decelerated. Since Q is negative, the flow is from the closed tank 9 to the accumulator 8
And braking energy is recovered. When the capacity of the hydraulic motor 1 is reduced to 0 when the shaft rotation speed U becomes 0, the shaft torque T of the hydraulic motor 1 becomes 0 and the weight 3 does not accelerate, that is, the weight 3 stops. I have.

Next, when the motor capacity V of the hydraulic motor 1 is made negative as shown in FIG. 3B, a negative torque T (-) is generated in the hydraulic motor 1 and the weight 3 It is in the reverse rotation / acceleration state at the shaft rotation speed U. Thereafter, the rotation shifts to constant-speed rotation as in the case of the forward rotation, so that no power supply is required, and the braking energy is recovered during deceleration.

As described above, the shaft rotation speed U or the shaft rotation phase can be controlled by operating the motor capacity V of the hydraulic motor 1. Now, in the configuration shown in FIG. 3, if the moment of inertia of the weight 3 is I (kg · m ² ), U = ∫Tdt / I, and the shaft rotation speed can be controlled by feedback control. If a command to speed control is used as a speed signal corresponding to the deviation between the command and the detected amount, the shaft rotation phase can be controlled.

From this equation, when du / dt = 0,
It is derived that T = 0. That is, (c) of FIG.
In the stop / constant speed state shown in FIG. 7, it can be understood that no power is consumed at all if the capacity control device is set to 0 and the loss other than the hydraulic circuit system is ignored. On the other hand, at the time of deceleration shown in FIGS. 3D and 3E, the signs of the shaft rotation speed U and the shaft torque T are opposite, so that the sign of the required flow rate Q is negative, and the kinetic energy of the weight 3 is stored in the accumulator. 8, it can be seen that it can be recovered.

In short, the energy required for rotationally driving the weight 3 is consumed as a liquid volume from a constant pressure source. At this time, the constant pressure source and the variable displacement hydraulic device There is no resistance element and there is almost no power loss. Further, by installing the accumulator 8, since the braking energy from the weight 3 is recovered as a liquid volume, wasteful consumption of energy can be minimized.

FIG. 1 shows a hydraulic actuator A of a secondary control system having the above configuration.
To the mold clamping device 20 and the measuring device 3 of the resin injection molding machine.
0, a high-pressure line 6a is directly connected to the rod-side port of the protruding cylinder 60, and the high-pressure line 6a and the low-pressure line are connected to the head-side port. A direction switching valve 61 for switching the communication with the valve 6b is provided. A large-capacity general-purpose accumulator 68 is connected to the high-pressure line 6a, and a large-capacity general-purpose closed tank 69 acting as a low-pressure accumulator is connected to the low-pressure line 6b. The hydraulic fluid is transferred from the low-pressure pipeline 6b to the high-pressure pipeline 6a, and constitutes a general-purpose hydraulic pressure source device together with the pump 5.

Mold clamping device 2 for opening and closing the mold and replacing the mold
Reference numeral 0 denotes a ball screw 22a mounted on the output shaft 22 of the hydraulic motor 21 of the hydraulic actuator A20 by the secondary control, and a mold clamping member 23 screwed to the ball screw 22a is driven in the straight direction to operate the toggle mechanism and the like. Operate through. The metering device 30 attaches the screw 33 to the output shaft 32 of the hydraulic motor 31 of the hydraulic actuator A30 by the secondary control, and feeds the resin material supplied from the hopper 70 to the tip by the rotational transfer action of the screw 33 to heat the heating cylinder 34. Accumulates on the tip side of

The injection device 40 has a ball screw 42a attached to the output shaft 42 of the hydraulic motor 41 of the hydraulic actuator A40 by the secondary control, and is screwed to the ball screw 42a to move in a linear direction. 43 rotatably supports the output shaft 32 of the weighing device 30 to impart a linear motion to the screw 33.

Further, in the nozzle moving device 50, a ball screw 52a is attached to the output shaft 52 of the hydraulic motor 51 of the hydraulic actuator A50 by the secondary control, and a bearing member 53 is screwed to the ball screw 52a.
The output shaft 42 of the injection device 40 is rotatably supported by the bearing member 53, and the nozzle 34a provided in the head of the heating cylinder 34 is moved back and forth. In FIG. 1, reference numerals 27, 37, 47, and 57 denote check valves,
8, 38, 48, 58 are accumulators, 29, 3
Reference numerals 9, 49, and 59 indicate closed tanks, respectively.

Since the drive circuit of the injection molding machine has the above-described configuration, the accumulator 28 of the hydraulic actuator A20 for the mold clamping device 20 is determined by the maximum moving speed of the mold and the holding machine. If the corresponding kinetic energy can be accumulated, the energy used for acceleration can be substantially recovered at the time of deceleration, so that only the loss due to friction or the like needs to be gradually supplied. Therefore, since the supply flow rate at this time may be small, it is sufficient that the passage loss is small and the pipe is narrow. This is exactly the same for the nozzle moving device 50.

On the other hand, for the injection device 40, if the energy required for injection can be stored in the accumulator 48 of the hydraulic actuator A40, the flow rate required for the accumulator 48 to re-accumulate in the entire cycle time. Only need to be able to supply. Incidentally, in the pressure-holding process, the hydraulic motor 41 only operates the displacement and the output shaft 42 does not rotate, so that almost no power is required. The same applies to the weighing device 30.

In the protruding cylinder 60, the pressure fluid is usually communicated to the rod side, the head side is communicated to the tank, and the piston is at the retreating end shown in the figure.
, The pressure liquid is introduced to the head side, the piston protrudes due to the difference in pressure receiving area, and the molded product is released from the mold. If necessary, the extension cylinder 6
0 is the same hydraulic actuator A as the other devices 20 to 50
The protruding pin may be operated instead of (FIG. 2).

Normally, these devices are operated sequentially. For example, the mold clamping device 20 and the nozzle moving device 50 are operated.
It is also possible to reduce the cycle time by simultaneously operating and to retract the nozzle while opening the mold. In that case, each hydraulic actuator 20, 30, 4
Since energy corresponding to the work is accumulated in the accumulators 28, 38, 48, 58 of 0, 50, the pressure fluctuation is extremely small, and there is no possibility of interference with each other.

Next, the hydraulic actuator A shown in FIG.
An embodiment in which the accumulator 8 and the sealed tank 9 are integrally fixed to the hydraulic motor 1 will be briefly described with reference to FIG. FIG. 4 is a cross-sectional plan view of the hydraulic motor 1, showing a swash plate 14.
Are first and second displacement control pistons 12, 1 (not shown).
3 (FIG. 2), it is possible to swing and rotate a predetermined angle about the axis X from a state perpendicular to the plane of the drawing.

On the other hand, a piston 16 can slide in each of a plurality of cylinder bores 15a formed at predetermined angular intervals on the same pitch circle from the rotation center axis of the cylinder block 15 which rotates together with the output shaft 2. It is inserted in.
A valve plate 17 is in sliding contact with the rear surface of the cylinder block 15, and the cylinder bore 15a is connected to the accumulator 8 and the closed tank 9 through a plurality of arc-shaped valve holes 17a formed in the valve plate 17.
Is communicated to. The accumulator 8 and the closed tank 9 are formed integrally with the casing 1c of the hydraulic motor 1, and the accumulator 8 communicates with the high-pressure pipe 6a (FIG. 2) via the check valve 7.

A shoe 18 is loosely fitted to the spherical tip portion 16a of each piston 16 so as to freely rotate in all directions, and the shoe 18 is slidably and rotatably pressed against the swash plate 14 so as to rotate with the rotation of the cylinder block 15. The piston 16 is moved backward in the axial direction. Further, the output shaft 2 is provided in the casing 1c.
, An electric motor 19 is provided, and a rotor 19a is fixed to the output shaft 2 and a stator 19b is fixed to the casing 1c. In addition, a tank unit may be provided together with the electric motor 19 in the casing 1c. In such a case, all the pipings are not necessary, but only one of them may be provided.

A drive current corresponding to the amount of torque operation is supplied to the electric motor 19 to generate a drive torque, and a signal corresponding to the amount of torque operation is transmitted to the controller 1 shown in FIG.
Output to 0. The control device 10 controls the control valve 11 by supplying an exciting current to the electromagnetic actuator of the control valve 11 according to the input signal. Thus, in this embodiment,
By providing the accumulator 8 and the closed tank 9 integrally with the casing 1c of the hydraulic motor 1, the necessity of piping is eliminated, and the installation is further simplified.

In the embodiment of the present invention shown in FIG. 1, the mold clamping device 20, the measuring device 30, and the injection device 4
Although the hydraulic actuators A20, A30, A40, and A50 by the secondary control system are all used to drive the 0 and nozzle moving devices 50, they need not always be used, and only the necessary devices are driven. It may be used. The accumulators 28, 38, 48, 58 and the closed tanks 29, 3 are respectively provided to the hydraulic actuators A20, A30, A40, A50.
When 9, 49 and 59 are provided, the general-purpose accumulator 68 and the general-purpose closed tank 69 provided in the high-pressure pipeline 6a and the low-pressure pipeline 6b do not necessarily have to be provided.

Further, in the hydraulic circuit shown in FIG.
With the capacity control function of the pump 5, the pressure level of the high-pressure line 6a may be made variable, and the discharge power (flow rate pressure product) may be made substantially constant. Pump 5
It is also possible to make the operating speed possible or to turn it on and off by controlling the pressure value.

[0041]

As described above, the driving device of the injection molding machine according to the present invention is a hydraulic actuator comprising a hydraulic pressure source device, a variable displacement hydraulic device, a displacement operating device thereof, and a control device. Drive at least one of the devices constituting the injection molding machine, so that the design, installation, and maintenance burden can be reduced with a simple configuration, and a drive device with extremely low power loss can be obtained. Can be driven.

In the above-described driving device for the injection molding machine, the hydraulic actuator includes an accumulator, a hydraulic circuit communicating from the accumulator to the variable displacement hydraulic device, and a check valve from a general-purpose hydraulic pressure source device. And a hydraulic circuit that flows into the accumulator through the hydraulic circuit, the hydraulic circuit becomes extremely simple, and it is not necessary to supply large power instantaneously when the mold and its holding machine are accelerated. And the cooling device can be simplified, and the occurrence of electromagnetic waves can be reduced to prevent malfunctions caused thereby.

In the above-described drive device for the injection molding machine, the accumulator is fixed to the variable displacement hydraulic device, so that the design and installation work is further reduced, and the power of the hydraulic pipeline is reduced. Loss can also be reduced.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram showing an enlarged portion of the hydraulic actuator.

FIG. 3 is an explanatory view showing various operation states of the hydraulic actuator.

FIG. 4 is a plan sectional view showing an example of the variable displacement hydraulic motor.

FIG. 5 is a hydraulic circuit diagram illustrating a driving device of a conventional injection molding machine.

[Explanation of symbols]

1, 21, 31, 41, 51: variable displacement hydraulic motors 2, 22, 32, 42, 52: output shaft 4: electric motor 5: pump 6a: high pressure line 6b: low pressure line 7, 27, 37, 47, 57: check valve 8, 28, 38, 48, 58: accumulator 9, 29, 39, 49, 59: closed tank 10: control device 11: control valve 12: first capacity control piston 13: first 2. Capacity control piston 14: Swash plate 15: Cylinder block 16: Piston 17: Valve plate 18: Shoe 19: Electric motor 20: Forming device 30: Measuring device 33: Screw 34: Heating cylinder 40: Injection device 50: Nozzle Moving device 60: Projecting cylinder 68: General-purpose accumulator 69: General-purpose closed tank A, A20, A30, A40, A50: Hydraulic actuator

Claims (3)

[Claims] At least one of a mold clamping, metering, injection, nozzle movement, and ejection device of an injection molding machine is connected to a hydraulic pressure source device for generating a substantially constant pressure and connected to the hydraulic pressure source device. Driven by a hydraulic actuator comprising a variable displacement hydraulic device, a displacement device for changing the capacity of the variable displacement hydraulic device, and a control device for sending an operation signal to the displacement device in response to an electric signal. A driving device for an injection molding machine. 2. A hydraulic actuator, comprising: an accumulator; a hydraulic circuit communicating from the accumulator to the variable displacement hydraulic device; and a hydraulic pressure flowing into the accumulator from a general-purpose hydraulic pressure source device through a check valve. The driving device for an injection molding machine according to claim 1, further comprising a circuit. 3. The driving device for an injection molding machine according to claim 2, wherein the accumulator is fixed to the variable displacement hydraulic device.