JPH0691709A - Injection molding machine - Google Patents

Abstract

PURPOSE:To provide a compact high performance injection molding machine developing advantageous electromotive and hydraulic characteristics. CONSTITUTION:In an injection process, pawls 37,39 are engaged by an actuator 36 to fix a spline receiving member 30 and an electromagnetic clutch 41 is connected to transmit rotary power to the rotary nut member 15 of an electromotor 5 and, further, predetermined oil pressure is supplied to a hydraulic cylinder 55. In this state, the speed of the electromotor 5 is controlled. on the basis of the assist of a hydraulic cylinder 55 to advance a screw shaft 22 and a screw 19. In a dwelling process, the hydraulic cylinder 55 is controlled to predetermined pressure on the basis of the supply of pressure due to the torque control of the electromotor 5. In a plasticizing process, pawls 37,11 are engaged to transmit the rotation of the electromotor 6 to the screw shaft 22 and the clutch 41 is cut off to freely rotate the nut member 15 and, further, predetermined back oil pressure is supplied to the hydraulic cylinder 55.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-line type injection molding machine, and more particularly, to a drive device including an electric and hydraulic hybrid.

[0002]

2. Description of the Related Art Generally, an in-line type injection molding machine melts and measures a plastic material by retreating a screw while rotating the screw, and stops the rotation of the screw to advance the molten resin into a mold. Although it is injected / filled into the inside, and the pressure is maintained, conventionally, there are a hydraulic drive system in which the rotation and axial movement of the screw are hydraulically performed, and an electric drive system in which the screw is electrically driven.

In the injection control, in the step of filling the mold with the molten resin, the program is controlled mainly based on the speed of the screw, and after the completion of the injection, a pressure is continuously applied to the molten material to keep it constant. In the holding pressure process for holding time, the program control is mainly performed based on the pressure.

By the way, the electric drive system using a servo motor can easily perform effective control for the above speed control, and pressure control becomes possible due to recent advances in electronic control equipment. The hydraulic drive system can exhibit advantageous characteristics for pressure control.

On the other hand, recently, a hybrid type injection molding machine in which an electric servomotor and a hydraulic cylinder are combined is disclosed in Japanese Patent Laid-Open Nos. 4-141408 and 4-18.
It is disclosed as Japanese Patent No. 9525.

The one disclosed in JP-A-4-141408 is
When a hydraulic injection piston rod is connected to an electric servomotor of relatively small power via a ball screw device, and when the actual drive value of the hydraulic injection cylinder that is open-controlled according to a predetermined sequence deviates from the set target value, the setting is performed. Feedback control is performed by supplementarily driving the electric servomotor so that the measured drive value matches the target value.

In Japanese Patent Laid-Open No. 4-189525, the injection speed is controlled by an electric servomotor and the holding pressure is controlled by a hydraulic mechanism.

[0008]

The combination of the electric motor and the hydraulic cylinder described above is
It is used only for control during injection / pressure holding in which the screw is moved in the axial direction, and another electric or hydraulic motor for screw rotation is required to rotate the screw to melt / mix the resin.

The former is based on the speed control and pressure control based on the hydraulic cylinder, and when the measured speed value and measured pressure value based on the hydraulic mechanism deviate from the predetermined set speed value and set pressure value, the servo motor is turned on. Driven, feedback control is performed so that the measured value matches the predetermined value,
Therefore, in addition to the variable relief valve for pressure control in the hydraulic mechanism,
A variable flow rate control valve (proportional electromagnetic flow rate control valve) for speed control is required, the structure is complicated and expensive, and the feedback control by the servo motor and the speed control by the hydraulic mechanism interfere with each other, resulting in control reliability. May decrease. Further, this one has a ball screw device, which is connected to the piston rod of the hydraulic (injection) cylinder and connected to the piston rod of the cylinder, and is controlled by an electric servomotor, to make the device compact, especially the shaft. There is a risk of lack of compactness in the direction.

On the other hand, in the latter case, when the molten resin for advancing the screw is filled, the speed is controlled by an electric servomotor, and when the pressure is maintained, the pressure is controlled by a hydraulic mechanism. The hydraulic mechanism is stopped, and the electric servomotor is stopped when the pressure is maintained. For this reason,
Requires a large capacity electric servomotor and hydraulic mechanism that can independently support control during filling and holding pressure respectively.
It becomes a large-scale and expensive device, and the power efficiency also decreases.

Therefore, according to the present invention, the rotation of the screw and the control at the time of injection can be controlled by one electric motor, and the hydraulic cylinder device can be used as an assist to perform the highly accurate control and the compact construction. It is an object of the present invention to provide an injection molding machine that can perform reliable operation with high efficiency.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and supports a screw (19) in a heating cylinder (17), retracts the screw while rotating it, and rotates the screw. In an injection molding machine having a drive unit (U) for stopping and advancing, a sleeve that rotates integrally with an electric motor (5) arranged in a cylindrical casing (1) and a rotor (3) of the electric motor. A member (9), a screw shaft (22) integrally connected to the rear end of the screw (19), and a spline receiving member engaged with a spline (26) formed on the screw shaft (22). (30) and a female screw member (15) screwed to a male screw (25) formed on the screw shaft (22).
And a switching means (4) capable of selectively engaging the spline receiving member (30, 37) with the fixing member (1, 39) such as the casing or the sleeve member (9, 11).
0, 36), clutch means (41) interposed between the sleeve member (9) and the female screw member (15), and a piston member (56) connected to the rear end of the screw shaft (22). And a hydraulic cylinder device (55) constituted by cylinders (57, 30c) provided on the inner diameter of the spline receiving member (30), and the spline receiving portion (40) based on the switching means (40, 36). (30, 37) engaged with the fixing members (1, 39), the clutch means (41) is connected to transmit a predetermined rotation of the electric motor (5) to the female screw member (15). By supplying a predetermined hydraulic pressure to the hydraulic cylinder device (55), the screw is moved forward and held, and the spline receiving member is based on the switching means (40, 36). (30, 37) engaged with the sleeve members (9, 11), the clutch means (41) is separated, the screw (19) is rotated by the electric motor (5), and With back pressure applied to the hydraulic cylinder device (55), the screw (1
9) The injection molding machine is characterized by being set back.

Further, preferably, at the time of injection control for advancing the screw (19), the electric motor (5) is mainly operated so as to follow a predetermined program on the basis of assist of hydraulic pressure acting on the hydraulic cylinder device (55). ) Speed control
Further, during the pressure holding control, the hydraulic pressure of the hydraulic cylinder device (55) is pressure controlled mainly based on the pressure replenishment by the torque control of the electric motor (5) so as to follow a predetermined pressure program.

[0014]

Based on the above construction, in the injection process, the spline receiving member (3) is operated by the switching means (40, 36).
0, 11) is engaged with the fixing member (1, 39) to prevent the rotation of the screw shaft (22), the clutch means (41) is connected, and the hydraulic cylinder device (55) is further connected.
Supply a predetermined hydraulic pressure to. Then, the rotation of the rotor (3) of the electric motor (5) is transmitted to the female screw member (15) via the sleeve member (9) and the clutch means (41),
And the male screw (2) formed on the screw shaft (22)
5) is in a stopped state, the hydraulic cylinder device (5
With the rear end of the screw shaft (22) being assisted in the forward direction by the piston member (56) of 5), the male screw (25) rapidly advances based on the screwing and rotation of the female screw member (15). As a result, the screw (19) integrated with the male screw also advances in the heating cylinder (17) to inject the molten resin and fill the mold.

In the injection step, the hydraulic cylinder device (55) is supplied with a predetermined hydraulic pressure based on the variable relief valve, and the electric motor (5) is feedback-controlled while being assisted by the hydraulic pressure. The speed is corrected so as to follow the predetermined speed program.

Following the injection step, the holding pressure control is performed in the same state. In this state, the forward movement of the screw (19) is almost stopped, the electric motor (5) is torque-controlled to replenish a predetermined pressure, and the hydraulic cylinder device (5) is
The hydraulic pressure to 5) is pressure controlled according to a predetermined pressure control phase.

Further, in the plasticizing step, the spline receiving member (30, 3) is operated by the switching means (40, 36).
7) is engaged with the sleeve members (9, 11) to rotate the rotor (3) of the electric motor (5) to rotate the sleeve members (9),
It is transmitted to the screw shaft (22) through the spline receiving member (30) and the spline (26), and the clutch means (41) is separated to put the female screw member (15) in a free state. At the same time, the hydraulic cylinder device (5
A predetermined hydraulic pressure is supplied to 5) to apply a predetermined back pressure to the screw shaft (22) via the piston member (56).
In this state, the screw shaft (22) and the screw (19) integrated with the screw shaft (22) are rotated at a predetermined speed by the electric motor (5) to convey the resin in the screw tip direction while melting the resin, and at the same time, the hydraulic cylinder device (55). Based on the back pressure control by the screw (19), the screw (19) is retracted by the pressure reaction force of the molten resin. As a result, the screw (19) retreats while rotating, melting the resin and weighing it.

The reference numerals in parentheses are for comparison with the drawings, but do not limit the structure of the present invention.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the screw driving device U has a cylindrical casing 1, and the casing 1 is fixed on a base B. A motor core 2 is fixed in the casing 1, and the core 2
The rotor 3 arranged so as to face the inner circumference of the above constitutes an electric hollow motor 5 having a predetermined capacity such as a servo motor. A sleeve member 9 is rotatably and axially immovably supported by the casing 1 and the lid portion 1a integral with the casing 1 via bearings 6 and 7. The sleeve member 9 is supported by the rotor 3 and a key or the like. They are connected together. The sleeve member 9 is composed of two members 9a and 9b fixed by bolts 10 and extends to a length slightly shorter than the casing 1. The inner diameter of the base end portion of the sleeve member 9 has a spline-like engaging claw. 11 is formed, and a ball nut member 15 is rotatably supported on the inner diameter portion on the distal end side via bearings 12 and 13.

On the other hand, a heating cylinder case 16 is fixed to the tip of the casing 1, a heating cylinder 17 is fixed in the case 16, and a screw 19 is rotatably supported in the cylinder 17. . A material supply hole 20 extending to the screw 19 is formed in the case 16 and the cylinder 17, and a hopper 21 is provided so as to communicate with the material supply hole 20. And screw 1
A screw shaft 22 is coaxially fixed to the tip of the screw shaft 9. A ball screw 25 is formed on the screw shaft 22 of the screw shaft 22 and a spline 26 is formed on the opposite side thereof.

A cylindrical spline boss 30a is slidably fitted into the spline 26 of the screw shaft 22, and a sleeve 30b is integrally connected to the boss 30a. Constitutes the spline receiving member 30. Further, as shown in detail in FIG. 2, an annular piston member 33 is connected to an end of the sleeve 30b via a bearing 32 so as to be rotatable and integrally move in the axial direction, and a casing. An annular cylinder portion 35 is fixed to the cap member 1b integral with 1 by bolts, and the piston member 33 and the cylinder portion 35 form an air or hydraulic actuator 36. On the other hand, a spline-like engagement claw 37 is formed on one end outer peripheral surface of the sleeve 30b, and a spline-like engagement claw 39 is also formed on the inner peripheral surface of the cap member 1b which is a fixing member. The claw 37 of the sleeve 30 engages with either the fixed claw 39 or the rotary claw 11 based on the movement based on the actuator 36, thereby forming a switching dock clutch 40.

On the other hand, the ball nut member 15 is screwed into the ball screw 25 of the screw shaft 22 via balls, and these balls can circulate in the nut member 15. The nut member 15 has an end plate 15a.
At the same time, the cover member 15b is integrally fixed. An electromagnetic clutch 41 is disposed between the nut cover member 15b and the rotor sleeve member 9b, and the electromagnetic clutch 41 has an exciting coil portion 41a fixed to the casing 1 by a positioning pin 42. .

The electromagnetic clutch 41 includes a movable plate 41b supported by a ring plate 15c fixed to an end of a nut cover member 15b so as to be slidable only in an axial direction, and a suction standup formed at an end of a sleeve member 9b. The movable plate 41b is attracted to the rising portion 41c by the excitation of the exciting coil portion 41a, and the torque of the sleeve member 9 is transmitted to the nut member 15. The clutch means interposed between the sleeve member 9 and the nut member 15 is not limited to the friction type electromagnetic clutch described above, but may be another clutch such as a hydraulic clutch or a dock clutch.

Further, the end cap member 1 of the casing
As shown in detail in FIG. 2, a first rotary encoder 45 is provided in b, and the encoder 45 is provided with a gear 4
It is connected to the sleeve member 9 via 6, 47. A second rotary encoder 49 is arranged on the end cap member 1b, and a gear 50 fixed to the input shaft of the encoder 49 is a spline tooth which forms the engaging claw formed on the spline sleeve 30b. It meshes with 37. Furthermore, if necessary, the heating cylinder case 1
6, a third rotary encoder 51 may be arranged,
A gear 52 fixed to the input shaft of the encoder meshes with a gear 53 fixed to the ring plate 15c. Therefore, the first encoder 45 is the rotor 3 of the electric motor 5.
It is possible to detect the rotation amount of the sleeve member 9 that is integral with the
The encoder 49 can detect the amount of rotation of the spline receiving member 30 and thus the screw 19 that rotates integrally therewith, and the third encoder 51 can detect the amount of rotation of the nut member 15. The position of the screw 19 can be detected by the difference between the second encoder 49 and the third encoder 51.

The screw drive device U is provided with a hydraulic cylinder device 55 in addition to the above-mentioned electric drive device.

As shown in detail in FIG. 2, the hydraulic cylinder device 55 includes a piston member 56 fixed to the rear end of the screw shaft 22 and a cylinder end surface fixed to the rear end surface of the cylinder portion 35 of the actuator 36. The member 57. The piston member 56 is fixed to the rear end surface of the spline 26 by a bolt 59, and is fitted into the sleeve 30b of the spline receiving member in an oil-tight manner, so that the inner peripheral surface of the sleeve 30b becomes the cylinder surface 30c. The piston member 56 can move integrally with the screw shaft 22.

The cylinder end surface member 57 is a cylindrical portion 57.
The a and the flange portion 57b are integrally fixed, the cylindrical portion is inserted into the inner peripheral surface of the sleeve 30b, and the O-ring 60 forms an oil tight state. The flange portion 57b is fixed to the rear end surface of the end cap 1b with bolts 61 sandwiching the actuator cylinder portion 35. The end cap 1b and the cylinder portion 35 are fixed to each other.
The outer peripheral surface of the flange portion 57b is aligned to form a cylindrical surface.

The oil passages 62 and 6 are provided in the end surface member 57.
3 is formed, and the oil passage 62 on one side is the piston member 5
6 and the end surface member 57 to communicate with the hydraulic chamber to form a supply oil passage, and the other oil passage 63 is connected to the end surface member 57.
A drain oil passage that communicates between the two O-rings 60 and 60 and collects the oil leaking from the hydraulic chamber is formed. The supply oil passage 62 communicates with a hydraulic control unit (not shown) via a hose 65, and the hydraulic control unit includes a switching valve, a variable relief valve and the like.

Next, the operation of this embodiment will be described.

In the injection (filling) step, air (or hydraulic pressure) is supplied to the passage a of the actuator 36 to move the piston member 33 rightward in the drawing. Then, in the switching dock clutch 40, the spline claw 37 engages with the fixed claw 39, and the rotation of the spline receiving member 30 is blocked.
Therefore, the rotation of the screw shaft 22 and the screw 19, which are engaged with the boss 30a by the spline 26, is also prevented. On the other hand, a current is supplied to the coil 41a of the electromagnetic clutch 41, the movable plate 41b is attracted to the rising portion 41c, and the nut member 15 is integrally connected to the sleeve member 9.

On the other hand, a predetermined hydraulic pressure from the hydraulic control unit is supplied to the hydraulic cylinder device 55 via the hose 65,
Further, it acts on the hydraulic chamber via the oil supply passage 62, presses the piston member 56 integral with the screw shaft 22, and assists the rear end of the shaft 22 in the screw forward direction F.

Then, with the assistance of the hydraulic cylinder device 55, the rotation of the rotor 3 of the electric hollow motor 5 is transmitted to the sleeve member 9 and further the electromagnetic clutch 41.
The rotation of the ball screw 25 of the screw shaft 22 is blocked in this state, and the rotation of the nut member 15 causes the screw shaft 22 and the screw 19 to move in the direction of arrow F. Move rapidly to. As a result, a predetermined amount of resin melted by the rotation of the screw is injected from the nozzle and filled in the mold.

In the injection (filling) step, as shown in FIG.
As indicated by V, the control is performed by a speed program mainly composed of speed with respect to the screw position x. In this state, the servo motor 5 is operated by the first rotary encoder 45.
Based on (and the third rotary encoder 51), the rotation speed thereof is detected, and the correction feedback control by the speed component V ₁ as shown in FIG. 3 (b) is performed along the speed program curve V. On the other hand, the hydraulic pressure acting on the hydraulic cylinder device 55 is controlled by a variable relief valve so as to follow a predetermined control phase, as indicated by a line P ₁ in FIG. 3 (c). At this time, the pressure P ₂ within the torque limit based on the speed control V ₁ of the servomotor 5 acts in addition to the predetermined control phase by the hydraulic pressure (P ₁ + P ₂ ), and the pressure program curve of FIG. The pressure rises smoothly along P.

The hydraulic speed acting on the hydraulic cylinder device 55 is set to a constant high speed V ₂ as shown in FIG. 3 (b) so as not to interfere with the speed control V ₁ by the motor 5. Further, as shown in FIG. 3C, the pressure component P ₂ generated by the servomotor 5 acts in the positive direction of pressing the screw in addition to the hydraulic pressure component P ₁ , but the pressure component P ₁ generated by the hydraulic pressure. Is larger than the pressure program curve P, it may act in the negative direction along the speed control V ₁ . In addition, the pressure limit P _X of the hydraulic cylinder device 55 is relatively low because the speed of the hydraulic cylinder device 55 is set to a high value V ₂ and the displacement of the hydraulic pump and the layout of the hydraulic cylinder device are limited. It is set.

Then, when the filling of the molten resin into the cavity is completed and the pressure holding step is started, as shown in FIG. 3 (a),
It is switched to the pressure program control P consisting of the pressure acting on the screw 19 with respect to the time t (VP switching). In this state, as shown in FIG. 3 (c), the hydraulic pressure acting on the hydraulic cylinder device 55 is substantially at the limit value P _X , and the servomotor 5 almost stops the movement of the screw 19. Torque controlled and thus ball screw device 15,
It is replenished by adding as a pressure component P ₂ via 25 to the hydraulic pressure P ₁ . Further, in the pressure maintaining step, the hydraulic pressure acting on the hydraulic cylinder device 55 is reduced by the variable relief valve along a predetermined control phase in a state where the pressure component of the motor 5 based on the torque control is applied. Then, the pressure based on the hydraulic pressure and the electric motor is released, whereby the control along the pressure program curve P shown in FIG. 3 (a) is performed.

The hydraulic pressure acting on the hydraulic cylinder device 55 is controlled so as to follow a predetermined hydraulic control phase, which can be more accurately performed based on teaching. Next, a plasticizing process of melting and measuring a predetermined amount of resin is started. First, a valve (not shown) is switched to switch air from the passage a to b. Then, the actuator 36
Moves the spline sleeve 30b to the left in the figure and engages the engaging claw 37 of the sleeve 30b with the engaging claw 11 of the rotor sleeve member 9. At the same time, the electromagnetic clutch 41
The coil 41a is de-energized, the clutch is disengaged, and a predetermined hydraulic pressure is supplied from the hydraulic control unit to the hydraulic cylinder device 55.

Then, the rotation of the rotor 3 of the electric motor 5 is transmitted to the spline receiving member 30 through the engagement of the sleeve member 9 and the engaging claws 11 and 37, and further through the spline 26, the screw shaft 22 and the screw. 19, the nut member 15 is in a free rotation state, allows rotation and axial movement of the screw shaft 22, and a predetermined back pressure is applied to the rear end of the screw shaft 22 from the hydraulic cylinder device 55. . In this state, based on the rotation of the screw 19, the plastic material supplied from the hopper 21 is kneaded and sent in the distal direction, and the plastic material acts on the friction heat and the heating cylinder 17 accompanying the kneading action. It is melted by heating the heater.

The resin in the molten state is stored at the tip of the screw 19, and the pressure from the resin exerts a return pressing force in the arrow R direction on the screw 19. The return pressing force (back pressure) acting on the screw 19 acts on the hydraulic cylinder device 55 via the piston member 56,
The hydraulic pressure acting on the cylinder device 55 via the oil passage 62 is appropriately controlled by a variable relief valve to gradually discharge the oil in the hydraulic chamber, thereby gradually moving the screw shaft 22 and the screw 19 in the arrow R direction. Retreat to. This allows
The screw 19 rotates at a predetermined number of revolutions, and retracts so that the resin pressure does not become higher than a predetermined value.

Then, the screw 19 is rotated and retracted to melt the resin and measure a predetermined amount, and then the resin is injected in the injection step described above.

In the above embodiment, the pressure oil acting on the hydraulic cylinder device does not perform speed control by appropriately controlling the hydraulic pressure by the variable relief valve, but this is a variable flow control valve for speed control. Alternatively, the speed control may be enabled, or conversely, a fixed relief valve may be used to constantly supply a constant hydraulic pressure.

[0042]

As described above, according to the present invention,
The screw can be moved and rotated in the axial direction by one electric motor, and the drive device can be configured simply and compactly.

Further, since the electric motor is arranged in the cylindrical casing and the hydraulic cylinder device is provided on the inner diameter of the spline receiving member, the electric motor and the hydraulic cylinder device are of the hybrid type, but in the axial and radial directions. It can be compactly integrated.

Further, the electric motor and the hydraulic device work together in all of the injection (filling) step, the pressure holding step and the plasticizing step, and the power efficiency can be improved.

In the injection (filling) process that requires accurate speed control, the speed correction control can be performed by the electric motor having advantageous characteristics for the speed control, and in this state. Since it is assisted by the hydraulic cylinder device, it is possible to use a small electric motor, but it is possible to cope with a large capacity and to smoothly increase the pressure.

Further, in the pressure-holding process requiring a large holding pressure, the control can be performed by the hydraulic cylinder device which can exhibit advantageous characteristics for the pressure control, and in this state, the electric drive is performed. Since the motor replenishes the pressure by torque control, a large holding pressure can be provided and accurate pressure control can be performed even though a small capacity pump and a small diameter hydraulic cylinder device are used.

Further, in the plasticizing process in which a small back pressure is sufficient as compared with the injection and pressure-holding processes, the back pressure control at the time of retreating the screw can be sufficiently coped with by only the hydraulic cylinder device having a small capacity. Moreover, the rotation of the screw is performed by an electric motor, and the two can work together to exert high performance.

Therefore, in each process, the electric motor and the hydraulic cylinder device can sufficiently exhibit their respective excellent performances, and these high performances cooperate with each other to provide a high-performance and compact injection molding machine. be able to.

Further, since the speed can be accurately corrected by the electric motor, the hydraulic control device does not need an expensive speed control device such as a proportional electromagnetic flow control valve, and the structure can be simplified and the cost can be reduced. it can.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a drive device of a hybrid injection molding machine according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing a main part of the drive device.

FIG. 3 is a diagram showing control of the driving device, and FIG. 3A is a diagram showing a speed control program and a pressure control program during an injection (filling) step and a pressure holding step. (b) is a figure which shows speed correction control by an electric motor. FIG. 6C is a diagram showing pressure control by a hydraulic cylinder device and an electric motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing (fixing member) 3 Rotor 5 Electric motor (hollow motor) 9 Sleeve member 15 Female screw member (nut member) 19 Screw 22 Screw shaft 25 Male screw (ball screw) 30 Spline receiving member 30a Boss 30b Sleeve 30c Cylinder surface 36 Switching means (Actuator) 40 Switching means (switching claw dock clutch) 41 Clutch means (electromagnetic clutch) 55 Hydraulic cylinder device 56 Piston member 57 Cylinder end surface member

Claims (2)

[Claims] 1. An injection molding machine having a drive device for supporting a screw in a heating cylinder, retracting while rotating the screw, and stopping the rotation and advancing the screw, an electric motor arranged in a cylindrical casing. A sleeve member that rotates integrally with the rotor of the electric motor, a screw shaft integrally connected to the rear end of the screw, and a spline receiving member that engages with a spline formed on the screw shaft, A female screw member screwed into a male screw formed on the screw shaft; a switching means capable of selectively engaging the spline receiving member with a fixing member such as the casing or the sleeve member; Member interposed between the member and the female screw member, a piston member connected to the rear end of the screw shaft, and the sprue member. A hydraulic cylinder device constituted by a cylinder provided in the inner diameter of the engine receiving member, wherein the clutch means is connected by engaging the spline receiving portion with the fixing member based on the switching means. By transmitting a predetermined rotation of the electric motor to the female screw member and by supplying a predetermined hydraulic pressure to the hydraulic cylinder device, the screw is moved forward and held, and the spline receiving member is moved to the sleeve member based on the switching means. In a state of being engaged with, the clutch means is separated, the screw is rotated by the electric motor, and the screw is retracted while back pressure is applied to the hydraulic cylinder device. A characteristic injection molding machine. 2. At the time of injection control for advancing the screw, based on the assistance of the hydraulic pressure acting on the hydraulic cylinder device,
The electric motor is subjected to speed correction control mainly along a predetermined speed program, and at the time of the pressure holding control, based on pressure supplementation by torque control of the electric motor, mainly so as to follow the predetermined pressure program. The injection molding machine according to claim 1, wherein the hydraulic pressure of the hydraulic cylinder device is pressure-controlled.