JP4033993B2 - Electric injection molding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric injection molding machine. In particular, the present invention relates to a stopper that regulates the backward limit and forward limit of a conduction shaft driven by the rotation of an injection motor in an injection molding machine.
[0002]
[Prior art]
In an injection molding machine, a molded product can be obtained by injecting resin melted by heating in a heating cylinder at a high pressure, filling the cavity space in the mold apparatus, and cooling and solidifying in the cavity space. It has become.
[0003]
Such an injection molding machine has a mold clamping device and an injection device, and the mold clamping device includes a fixed platen and a movable platen, and the mold clamping cylinder moves the movable platen forward and backward to close the mold, clamp and open the mold. Can be done.
[0004]
On the other hand, the injection device includes a heating cylinder that heats and melts the resin supplied from the hopper and an injection nozzle that injects the molten resin, and a screw is rotatably disposed in the heating cylinder. Has been. The screw is moved forward, the resin is injected from the injection nozzle, and the screw is moved backward to measure the resin.
[0005]
By the way, the invention filed by the present applicant as Japanese Patent Application No. 9-308662 (hereinafter referred to as “prior invention”) on November 11, 1997 will be described below with reference to FIG. In FIG. 7, reference numeral 150 denotes a heating cylinder. The heating cylinder 150 is similar to the conventional one in that the screw 151 is disposed so as to be movable forward and backward and rotatable.
The screw 151 has a screw head at the front end, extends backward in the heating cylinder 150, and a bearing box 153 is fixed at the rear end. A spiral flight 154 is formed around the screw 151, and a groove is formed between the flights 154.
[0006]
A hopper is fixed to the heating cylinder 150 (not shown). The resin supply port from the hopper is formed at a position corresponding to the rear end portion of the screw groove when the screw 151 is placed in the foremost position in the heating cylinder 150.
Therefore, when the screw 151 is rotated during the measuring step, pellet-shaped resin is supplied from the hopper, and the resin enters the heating cylinder 150 and is advanced in the groove of the screw.
[0007]
Further, a heater (not shown) is disposed around the heating cylinder 150, and the heating cylinder 150 is heated by the heater to melt the resin in the screw groove. Therefore, when the screw 151 is rotated, the screw 151 is retracted by the resin pressure, and the melted resin for one shot is accumulated in front of the screw head.
[0008]
Next, when the screw 151 is advanced without rotating during the injection process, the resin accumulated in front of the screw head is injected from the injection nozzle 152 and filled into the cavity space of the mold. A drive unit 155 for rotating or advancing and retreating the screw 151 is disposed behind the heating cylinder 150. The drive unit 155 includes a measuring motor 157 movably disposed with respect to the frame 156 and an injection motor 158 fixed to the frame 156, and the injection motor 158 and the screw 151 are disposed on the same axis. Has been.
[0009]
A guide bar 159 extending in parallel with the screw 151 is disposed on the frame 156, and the measuring motor 157 moves along the guide bar 159. For this purpose, the support plate 160 is slidably disposed with respect to the guide bar 159, and the measuring motor 157 is attached to the support plate 160.
A driving pulley 161 is fixed to the output shaft of the metering motor 157, and a driven pulley 163 is fixed to the outer periphery of the box body 162 of the bearing box 153. The timing is between the driving pulley 161 and the conventional pulley 163. A belt 164 is stretched. The driving pulley 161, the driven pulley 163, and the timing belt 164 constitute a transmission means for connecting the bearing box 153 and the measuring motor 157.
[0010]
On the other hand, the injection motor 158 includes a stator 165 fixed to the frame 156 and a rotor 166 disposed on the inner peripheral side of the stator 165, and the rotor 166 is rotatably supported by the frame 156. For this purpose, a hollow rotor shaft 167 is fitted and fixed to the rotor 166, and both ends of the rotor shaft 167 are supported by the frame 156 by bearings 168 and 169.
[0011]
Also, bearings 170 and 171 are disposed in the bearing box 153, and the screw 151 and a ball screw shaft 172 as a transmission shaft are connected to each other so as to be relatively rotatable by these bearings, and are fixed to the frame 156 via a load meter 177. The ball nut 173 thus formed and the screw portion 174 formed on the ball screw shaft 172 are screwed together. The rotational movement is converted into a linear movement by the threaded portion 174 of the ball screw shaft.
[0012]
Accordingly, when the measuring motor 157 is driven in the measuring step, the rotation of the measuring motor 157 is sequentially transmitted to the driving pulley 161, the timing belt 164, the box body 162, and the screw 151, the screw 151 is rotated, and the resin is screwed. Move to the front of the head. In this case, since the screw 151 and the ball screw shaft 172 are coupled to each other via a bearing box 153 so as to be relatively rotatable, the rotation transmitted to the box body 162 is not transmitted to the ball screw shaft 172, but the heating cylinder 150 The pressure of the resin inside is transmitted to the ball screw shaft 172 via the bearing box 153. Accordingly, the ball screw shaft 172 moves backward while rotating, and accordingly, the screw 151 is moved backward. When the screw 151 is moved backward, a back pressure is applied to the screw 151 against the pressure of the resin.
[0013]
On the other hand, in the injection motor 158, by supplying a current having a predetermined frequency to the stator 165, the screw 151 can be advanced without rotating. Therefore, an annular locking member 175 is fixed inside the hollow rotor shaft 167, and a spline 176 formed on the inner periphery of the locking member 175 and a spline formed on the rear outer periphery of the ball screw shaft 172 are engaged. Match. The spline 176 constitutes a rotation transmission unit that transmits the rotation of the injection motor 158.
[0014]
Accordingly, when the injection motor 158 is driven in the injection process, the rotation of the injection motor is sequentially transmitted to the rotor shaft 167, the locking member 175, and the ball screw shaft 172. Since the ball nut 173 is fixed to the frame 156, the ball screw shaft 172 rotates and moves forward to advance the screw 151. At this time, the radiant power applied to the timing belt 164 is transmitted to the load meter 177 via the bearing box 153 and detected.
The ball screw shaft 172 advances and retracts by a stroke S in the axial direction (FIG. 7).
[0015]
As described above, the rotation of the injection motor 158 is directly transmitted to the ball screw shaft 172 without passing through a speed reduction mechanism, a pulley, or the like, so that mechanical efficiency can be increased and inertia can be reduced. Can do. However, in an electric injection molding machine, injection is performed by advancing the screw by driving a motor, but it is necessary to prevent the tip of the screw from colliding with the tip of the heating cylinder even if the screw is accidentally advanced too much. .
[0016]
As a means for solving this problem, for example, as shown in FIG. 8, a ring-shaped stopper 181 is provided on a pressure plate 178 for advancing a screw, and a valve nut 184 is provided on a front plate 180 to which a heating cylinder 179 is fixed. The screw 183 is prevented from moving forward.
[0017]
With such a configuration, even if the pressure plate 178 tries to move until the screw and the heating cylinder collide due to a malfunction of the controller or the like, the pressure plate 178 and the screw are held by the valve nut 184 with the stopper 181 fixed to the front plate 180. It is safe because the forward movement is blocked and the forward movement of the screw stops before it hits the cylinder.
[0018]
However, when such a stopper is installed, since the ring-shaped stopper 181 is provided at a position away from the axis of the screw 183, the stopper 181 and the valve nut 184 are separated even if the pressure plate 178 is slightly inclined. The pressure plate 178 and the ball screw 182 were subjected to excessive stress. Further, the pressure plate 178 may be inclined due to a slight dimensional difference between the stopper 181 and the valve nut. As a result, a moment load is applied to the screw shaft and the ball screw shaft, causing mechanical damage.
[0019]
[Problems to be solved by the invention]
In the electric injection molding machine described above, a moment is applied to the screw shaft or ball screw shaft when the electric injection motor interferes with the stroke limit, and the pressure plate and the like caused by this moment load are prevented from being damaged. Objective.
[0020]
[Means for Solving the Problems]
A heating cylinder, a screw disposed in the heating cylinder so as to advance and retreat, an injection motor for moving the screw shaft forward and backward, and a rotation of the injection motor connected to the screw in the heating cylinder so as to be rotatable relative to the heating cylinder. And a transmission shaft having a motion direction conversion section for converting rotational motion into linear motion, and the injection motor and the transmission shaft are disposed on the same axis, and the transmission shaft is injected. An advancing / retreating amount restricting means for restricting the advancing / retreating in the axial direction inside the rotor constituting the motor for use and restricting the advancing / retreating in the axial direction was installed on the transmission shaft.
In the above configuration, the transmission shaft includes a ball screw part and a spline part, and the advance / retreat amount limiting means includes a forward limit stopper provided at the rear end part of the spline part and a reverse limit stopper provided at the front part of the spline part. The front end of the spline nut and the step portion of the spline nut are in contact with each other.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
A description will be given with reference to FIGS. The basic technical idea that the present invention is an electric injection molding machine is an extension of the electric injection molding machine according to the prior invention described with reference to FIG. However, the present invention further improves this and relates to a stopper that regulates the backward limit and forward limit of the conduction shaft driven by the rotation of the injection motor in the injection molding machine.
[0022]
FIG. 1 is a cross-sectional view of an injection molding machine according to the present invention, and FIG. 2 is an external side view of the injection molding machine according to the present invention. 3 is a cross-sectional view taken along arrow A in FIG. 4 is a sectional view taken along arrow C in FIG. 1, FIG. 5 is a sectional view taken along arrow D in FIG. 1, and FIG. 6 is a sectional view taken along arrow E in FIG. 1 and 2, reference numeral 1 denotes a heating cylinder, and a screw (see FIG. 7) is disposed in the heating cylinder 1 so as to be able to advance and retreat and to be rotatable, as in the prior art described in FIG. Has been. The screw and screw shaft 3 extend rearward in the heating cylinder 1, and the rear end of the screw shaft 3 is fixed to a screw support plate 4 (see FIG. 6).
[0023]
As in the case of FIG. 7 and the subsequent figures, a resin supply port 5 is formed at a set location in the heating cylinder 1, and a hopper (FIG. 2) is fixed on the resin supply port 5. The resin supply port 5 is formed at a position corresponding to the rearmost end of the groove formed by the flight of the screw in the state where the screw is placed in the forefront in the heating cylinder 1. Accordingly, when the screw shaft 3 is moved backward while rotating in the measuring step, pelletized resin is supplied from the resin supply port 5.
[0024]
Further, a heater (not shown) is disposed around the heating cylinder 1, thereby heating the heating cylinder 1 and melting the resin in the groove of the screw 2. Therefore, when the screw 2 is rotated, the screw 2 is retracted by the resin pressure, and one shot of molten resin is accumulated in front of the screw head.
[0025]
Next, when the screw shaft 3 is advanced without rotating during the injection process, the molten resin collected in front of the screw head is injected from the injection nozzle and filled into the cavity space in the mold.
[0026]
By the way, behind the heating cylinder 1 is a drive unit 6 for rotating and advancing and retracting the screw 2. The drive unit 6 includes a measuring motor 8 movably disposed with respect to the machine frame 7 and an injection motor 9 fixed to the machine frame 7. The injection motor 9 and the screw shaft 3 are on the same axis. It is arranged on the line.
[0027]
The machine frame 7 is provided with a plurality of guide rods 10 extending in parallel with the screw 2 (FIG. 4), and a pressure plate 11 that supports the measuring motor 8 moves along the guide rods 10. As shown in FIGS. 1 and 2, the machine frame 7 includes a front frame 7a that covers a portion of the heating cylinder 1 and a rear frame 7b that supports a ball nut 36 and a guide rod 10 to be described later. And 7b are integrally connected by four connecting rods 12 as shown in FIG.
[0028]
A motor mounting bracket 13 (FIGS. 1 and 3) is attached to the side of the pressure plate 11, and a measuring motor 8 is attached to the bracket 13 via a motor flange 14. A bearing box 16 is rotatably mounted in the pressure plate 11 via bearings 15a and 15b. Reference numeral 17 denotes a bearing holder, which holds one bearing 15b. The bearing box 16 includes an annular hollow shaft 18 fixed to the rear of the screw support plate 4 and a bearing retainer 19. The front end of the ball screw shaft 30 is rotatably supported via bearings 20 and 21. A bearing retainer 22 holds the bearing 20 between the bearing retainer 19.
[0029]
Now, in FIG. 1, a gear 23 is fixed to the output shaft 8 a of the metering motor 8, and this gear 23 meshes with an annular gear 25 via an intermediate gear 24. The annular gear 25 is fixed to the outer periphery of the hollow shaft 18, and one end of the hollow shaft 18 is bolted to the rear end of the screw support plate 4. A hollow portion 38 is formed by the hollow shaft 18, the bearing holder 17, the pressure plate 11 and the bracket 13, and the motor flange 14, and the gears 23, 24, and 25 are accommodated in the hollow portion.
[0030]
The injection motor 9 includes a stator and a rotor. A hollow rotor shaft 26 is fitted and fixed to the rotor. Both ends of the hollow rotor shaft 26 are rotatably supported in the motor frame by bearings 27 and 28, and a spline nut 29 is fixed in the hollow rotor shaft 26, and the rear end of the ball screw shaft 30 is attached to the spline nut 29. The spline shaft 31 fixed to is slidably engaged. Reference numeral 32 denotes an annular backward limit stopper that constitutes an advance / retreat amount limiting device provided at the front portion of the spline shaft 31, and reference numeral 33 denotes an advance limit stopper provided at the rear end of the spline shaft 31. Since these front and rear stoppers 32 and 33 are provided, it is possible to prevent the spline shaft 31 from coming into contact with these stoppers in the front and rear stroke limit and further strokes. The forward limit stopper 33 is configured to be engaged with and stopped by a step portion 29 a provided on the spline nut 29.
[0031]
Reference numeral 34 denotes a guide rod support member that supports the rear end of the guide rod 10, and an injection motor 9 is fixed to the guide rod support member. A load cell 35 is fixed to a rear frame 7b and a flange 36a provided at the rear end of the ball nut 36, and an oil supply plate 37 having an oil supply port is fixed to the upper portion of the load cell 35. Eventually, the guide rod 10 passes through the rear frame 7b, and is supported by being fastened to the guide rod support member 34 with screws 10a.
[0032]
In the weighing process, when the weighing motor 8 is driven in the weighing process, the rotation is transmitted from the output shaft 8 a to the gears 23, 24, 25, and the bearing box 16 is rotated by the rotation of the annular gear 25. Since the bearing box 16 is rotatable with respect to the ball screw shaft 30 by the bearings 20 and 21, this rotation is transmitted to the screw shaft 3 through the screw support plate 4.
[0033]
In the injection process, the hollow rotor shaft 26 is rotated by the rotation of the injection motor 9, the spline shaft 31 is rotated, and the ball screw shaft 30 that is integrally fixed to the front end of the spline shaft 31 is rotated. Then, the ball screw shaft 30 is advanced by the ball nut 36, and the screw shaft 3 is advanced to perform injection. At this time, the backward limit stopper 32 contacts the front end of the spline nut 29 to limit the backward stroke, and the forward limit stopper 33 contacts the step 29a of the spline nut 29 to limit the forward stroke.
[0034]
【The invention's effect】
(1) Since the advance / retreat amount control device is provided coaxially with the conduction shaft in this way, the distance from the axis of the conduction shaft to the advance / retreat amount control device becomes short. Therefore, the generation of moment load can be minimized, and the related members can be prevented from being damaged.
(2) Also, a spline nut is provided inside the rotor of the injection motor, and this step 29a is provided with a forward limit stopper and a backward limit stopper at the rear end of the ball screw shaft, so the distance from the spline shaft core to the stopper This prevents the moment load from being generated on the screw shaft and ball screw shaft when the stroke limit interferes.
(3) The structure is extremely simple because the advancing / retreating prevention means has a contact structure between the front and rear ends of the spline nut and the front and rear ends of the spline shaft. It is a great place to contribute to
[Brief description of the drawings]
FIG. 1 is a transverse sectional view of an injection molding machine embodying the present invention.
FIG. 2 is an external side view of the same.
FIG. 3 is a cross-sectional view of FIG.
4 is a cross-sectional view taken along the line C in FIG.
FIG. 5 is a cross-sectional view taken along the line D in FIG.
6 is an E sectional view of FIG. 1. FIG.
FIG. 7 shows the “prior invention” by the present applicant in an electric injection molding machine.
FIG. 8 shows a known molding machine provided with a stopper for restricting advancement and retraction.
[Explanation of symbols]
1 Heating cylinder 2 Screw 3 Screw shaft 4 Screw support plate 5 Resin supply port 6 Drive unit 7 Machine frame 7a Front frame
7b Rear frame 8 Weighing motor 9 Injection motor 10 Guide rod
11 Pressure plate 12 Connecting rod
13 Motor mounting bracket 14 Motor flange
15a, 15b Bearing 16 Bearing box
17 Bearing holder 18 Hollow shaft
19 Bearing retainer 20 Bearing
21 Bearing 22 Bearing restraint
23 gear 24 intermediate gear
25 Annular gear 26 Rotor shaft
27 Bearing 28 Bearing
29 Spline nut 29a Step
30 Ball screw shaft 31 Spline shaft
32 Reverse limit stopper 33 Forward limit stopper
34 Guide rod support member 35 Load cell
36 Ball nut 37 Lubrication plate
38 Cavity

Claims (2)

A heating cylinder;
A screw disposed in the heating cylinder so as to freely advance and retract;
An injection motor for advancing and retracting the screw shaft, a rotation transmission unit for transmitting the rotation of the injection motor, and a motion direction conversion unit for converting the rotation motion to a linear motion. The transmission motor and the transmission shaft are arranged on the same axis, and the transmission shaft is inside the rotor constituting the injection motor and advances and retreats in the axial direction. An electric injection molding machine characterized in that an advance / retreat amount restricting means for restricting advance / retreat in a direction is installed on a transmission shaft. The transmission shaft is composed of a ball screw part and a spline part, and the advance / retreat amount limiting means is a forward limit stopper provided at the rear end part of the spline part, and a reverse limit stopper provided at the front part of the spline part is the front end of the spline nut and 2. The electric injection molding machine according to claim 1, wherein the electric injection molding machine is configured to abut against a step portion of the spline nut.

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