JPH0152165B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a crank device used in a mold clamping device or a press machine such as an injection molding machine or a die-casting machine, and particularly relates to a method for determining the origin of the crank device. It is.

[Conventional technology]

FIG. 7 is a partial side view of a mold clamping device attached to a conventional injection molding machine. As shown in the figure, four tie bars 53 (only two tie bars 53 are shown in the drawing) are arranged at predetermined intervals between the tail stock 51 and the fixed die plate 52. ing. The die plate 5 moves using this tie bar 53 as a guide.
4 is movably supported with respect to the fixed die plate 51. A fixed die 55 is attached to the fixed die plate 52, and a movable die 56 is attached to the movable die plate 54, so that the movable die 56 can be moved into and out of contact with the fixed die 55.

A bracket 57 is protruded from the movable die plate 54, and the free end of a crank arm 59 is connected to the bracket 57 via a pin 58.
A mold opening/closing driving servo motor 60 is attached below the tail stock 51, and the base end of the crank arm 59 is rotated via a bearing 64 on an eccentric shaft 63 of a crankshaft 62 connected to a drive shaft 61 of the servo motor 60. freely connected.

Therefore, the rotational driving force of the servo motor 60 is transmitted to the crankshaft 62, the eccentric shaft portion 63, and the crank arm 5.
9 and the bracket 57, the rotational motion of the servo motor 60 is converted into a forward and backward motion by a crank mechanism, and the movable mold 54 is moved toward and away from the fixed mold 52.

A die thickness adjustment motor 66 is attached above the tail stock 51 via a bracket, and the drive side of the motor 66 is connected to each tie bar 53 via a gear group 67.
The mold thickness can be adjusted by rotating the motor 66.

Servo motor 60 as a drive source for the crank mechanism
An incremental encoder 68 that rotates simultaneously with the drive shaft 61 is attached to detect the rotation angle of the servo motor 60 and provide a control signal to the servo motor 60.

This encoder 68 is popular because it is inexpensive, but since it is an incremental encoder, it is necessary to locate the origin of the mold clamping device between when the power is turned on and the mold clamping device is used. In the conventional mold clamping device, in order to perform this origin finding, a position sensor 69 is installed near the dead point of the movable die plate 54, as shown in the figure.

Therefore, in the conventional mold clamping device, the power is turned on, the servo motor 60 is rotated, pulse signals from the encoder are counted by a counter in a control section (not shown), and the movable die plate 54 is moved from the fixed die plate 52. When it detects that it is below the position sensor 69, it sends a detection signal as an origin signal to a control unit (not shown),
The system is such that the count of the counter is reset and the pulse signal of the encoder 68 from that point on is used as an effective signal to control the servo motor 60. 70 in the figure is an escape rod.

[Problem to be solved]

By the way, in a conventional crank device, the above-mentioned variations in the mounting position of the position sensor 69 and variations in the sensitive range of the position sensor 69 directly affect the origin finding and appear as variations in the origin. Further, it is impossible to correct the backlash of the drive system in the crank device or the hysteresis when the position sensor 69 is a magnetic sensor.

For this reason, it is not possible to accurately determine the origin, and proper control operations are not performed, which poses a problem in terms of reliability.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for determining the origin of a crank device, which eliminates the drawbacks of the prior art and allows accurate origin determination.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention includes a crank mechanism body, a drive motor that drives the crank mechanism body, an incremental encoder that detects the rotation angle of the drive motor, and a reciprocating motion by the crank mechanism body. a proximity sensor that has a predetermined sensitive range and is provided near a dead point in the moving range of the movable part so as to sense when the movable part approaches; and a counter that counts pulse signals from the encoder. , and a calculation section that calculates the origin based on the count signal from the counter and the on/off signal from the proximity sensor.

Then, by rotating the drive motor, the movable part is moved via the crank mechanism main body, and the count number of the pulse signal at the first time point when the proximity sensor is turned on, and further rotation of the drive motor is continued. From the count number of the pulse signal at the second time point when the proximity sensor is turned off, the intermediate point between the first time point and the second time point is calculated by the calculation unit, and the intermediate point is set as the origin. This is a characteristic feature.

Furthermore, in order to achieve the above-mentioned object, the present invention has the following features:
A crank mechanism body, a drive motor that drives the crank mechanism body, an incremental encoder that detects the rotation angle of the drive motor, a movable part that reciprocates by the crank mechanism body, and has a predetermined sensitive range. A proximity sensor is provided near a dead point in the moving range of the movable part to sense when the movable part approaches, a counter that counts pulse signals from the encoder, and a count signal from the counter and a proximity sensor. and a calculation unit that calculates the origin based on the on and off signals.

Then, by rotating the drive motor, the movable part is moved via the crank mechanism main body, and the number of pulse signals counted at the first time point when the proximity sensor is turned on continues to rotate the drive motor. The count number of the pulse signal at the second point in time when the proximity sensor is turned off, and the third point in time when the proximity sensor is turned on again by reversing the moving direction of the movable part by continuing to reverse the drive motor. Based on the pulse signal count at that point and the pulse signal count at the fourth point when the drive motor continues to rotate and the proximity sensor turns off again, the sensor is turned on within the proximity sensor's sensitive range. The calculation unit calculates the midpoint between the OFF point and the OFF point, and the midpoint is set as the origin.

Furthermore, in order to achieve the above-mentioned object, the present invention has the following features:
A crank mechanism body, a drive motor that drives the crank mechanism body, an incremental encoder that detects the rotation angle of the drive motor, a movable part that reciprocates by the crank mechanism body, and has a predetermined sensitive range. A proximity sensor is provided near a dead point in the moving range of the movable part to sense when the movable part approaches, a counter that counts pulse signals from the encoder, and a count signal from the counter and a proximity sensor. and a calculation unit that calculates the origin based on the on and off signals.

and moving the movable part via the crank mechanism main body by rotating the drive motor,
The number of counts of the pulse signal at the first time when the proximity sensor is turned on, the number of counts of the pulse signal at the second time when the drive motor continues to rotate and the proximity sensor is turned off, and The count number of the pulse signal at the third point in time when the moving direction of the movable part is reversed and the proximity sensor is turned on again by reversing the direction of movement of the movable part, and the count number of the pulse signal at the third point in time when the proximity sensor is turned on again by continuing to rotate the drive motor Based on the count of the pulse signal at the point in time and the pulse signal at the fifth point in time when the rotation of the SARA drive motor continued for a while and then stopped, the distance between the on point and the off point of the sensor within the sensitive range of the proximity sensor is determined. The present invention is characterized in that the point and the current stop point are calculated by the calculation unit, and the intermediate point is set as the origin.

[Embodiments of the invention]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of an injection molding machine using a crank device according to an embodiment of the present invention.

1 in the figure is the base of the injection molding machine, and on the upper front side and on the right side when facing the drawing is the operation/display panel 2.
However, a chute 3 for discharging molded products is also provided on the left side. An injection cover 4, a safety door 5, and a crank cover 6 are provided on the upper part of the base portion 1.

A hopper 7 for charging pellet-shaped molding material is provided on the injection cover 4, and inside there is a charging servo motor 8, an injection servo motor 9, a nozzle touch limit switch 10, a nozzle touch back motor 11, and a heating motor. A tube 12 and the like are provided. A mold clamping device equipped with a crank mechanism described later is installed from the inside of the one safety door 5 to the inside of the crank cover 6.

FIG. 2 is a functional block diagram showing the relationship between the mold clamping device and the control section.

As shown in the figure, four tie bars 15 are installed between the tail stock 13 and the fixed die plate 14, arranged at predetermined intervals on the top, bottom, left, and right. A movable die plate 16 is movably supported using the tie bar 15 as a guide.
are respectively fixed, so that the movable mold 18 can be moved into and out of contact with the fixed mold 17.

A tail stock 13 is attached to the movable die plate 16.
A bracket 19 is provided to protrude toward the side, and the free end of a crank arm 21 is rotatably connected to it via a pin 20. A mold opening/closing servo motor 22 is installed below the tail stock 13, and the base end of the crank arm 21 rotates via a bearing 26 on the eccentric shaft of a crankshaft 24 connected to its drive shaft 23. freely connected.

Therefore, the rotational driving force of the mold opening/closing servo motor 22 is transmitted to the movable die plate 16 via the crankshaft 24, the eccentric shaft portion 25, the crank arm 21, and the bracket 19, and the servo motor 22
The rotational motion of is converted into a forward and backward motion by the crank mechanism, and the movable mold 16 is moved toward and away from the fixed mold 14.

Further, a mold thickness adjusting motor 28 is attached above the tail stock 13 via a bracket 27, and the drive side of the motor 28 is connected to each tie bar 15 via a gear group 29. The thickness of the mold can be adjusted.

Servo motor 22 as a drive source for the crank mechanism
An incremental encoder 30 that rotates at the same time as the drive shaft 23 is attached to detect the rotation angle of the servo motor 22 and provide a control signal to the servo motor 22.

The fixed die plate 14 has a movable die plate 1.
An arm 31 extending toward the 6 side is provided, and a magnetic sensor 32 for position detection is fixed to the tip of the arm 31. On the other hand, the movable die plate 16 has an arm 33 extending toward the fixed die plate 14.
is provided, and a magnetic material 34 is provided at the tip thereof.
is fixed, and as the movable die plate 16 moves, it faces the magnetic sensor 23 with a small gap as shown in the figure. This magnetic body 34 and the magnetic sensor 23 constitute a proximity sensor for finding the origin. In addition, 35 in the figure
is an ejection rod for taking out the molded product from the movable mold 18 after the mold is opened.

The mold opening/closing servo motor 22 and encoder 30 are connected to a control section 36. This control unit 36 includes a central processing unit (CPU) 37,
Memory 38 including random access memory (RAM) and read-on memory (ROM), servo motor 39, D/A converter 40, counter 4
It consists of 1 etc.

3 and 4 are explanatory diagrams and timing charts for explaining the first origin finding method.

In Fig. 3, point X in the figure is the mold clamping completion point (origin), point Y is the mold opening completion point, and range Z is the magnetic sensor 3.
2 (proximity sensor). As shown in the figure, when the power is turned on at point A, the mold opening/closing servo motor 22 starts rotating, which rotates the encoder 30 and sends a pulse signal to the pulse counter 41 of the control section 36. While being output, the movable die plate 16 approaches the fixed die plate 14 side via the above-mentioned crank mechanism. At this time, the magnetic body 34 is still attached to the magnetic sensor 3.
3, the magnetic sensor 33 remains off (see FIG. 4).

When the magnetic body 34 connected to the movable die plate 14 enters the sensitive range Z of the magnetic sensor 32 at point B, the magnetic sensor 32 is turned on as shown in FIG. The control unit 36 stores the pulse signal count number P1 at this point in the memory (RAM) 38.

Subsequently, the servo motor 22 is rotated to move the movable die plate 16 (magnetic body 34) in the same direction, and when it passes point C, the magnetic sensor 32 is turned off. The control unit 36 stores the pulse signal count P2 at this point in the memory (RAM) 38. Furthermore, the servo motor 22 is rotated a little, and at point F, the rotation of the servo motor 22 is stopped, and the movement of the movable die plate 16 (magnetic body 34) is stopped. The control unit 36 stores the pulse signal count number P3 at this point in the memory (RAM) 38.

Next, in the calculation section 37, based on the data of the counts P1, P2, and P3 of the pulse signal, the intermediate point X between point B and point C is calculated according to the following equation (1).
Find the midpoint and set it as the origin.

X=P3- _P1 + _P2 /2+a......(1) However, in this formula, a is the value of the mold clamping completion position, and when the mold clamping completion position is the origin as in this example, a =0. In addition, when the origin is the mold clamping completion position, the crank arm 21 is
The value is 1/2 of the number of pulses generated from the encoder 30 when rotating.

By finding the origin in this manner and resetting the number of pulses required to reach the origin, the crank mechanism can be subsequently controlled with the origin = 0 pulses. In addition, by finding the origin as described above, we can also find the current stopping point F.
Since we know the number of pulse signal counts up to the point F, we can accurately determine the position of the stopping point F. Figures 5 and 6 are explanatory diagrams and timing diagrams for explaining the second origin finding method. It's a chat. As shown in FIG. 5, when the power is turned on at point A, the mold opening/closing servo motor 22 starts rotating, which rotates the encoder 30 and outputs a pulse signal to the pulse counter 41 of the control section 36. At the same time, the movable die plate 16 is moved to the fixed die plate 14 via the above-mentioned crank mechanism.
coming closer to the side. At this time, since the magnetic body 34 has not yet entered the sensitive range Z of the magnetic sensor 32, the magnetic sensor 32 remains off (see FIG. 6).

When the magnetic body 34 connected to the movable die plate 16 enters the sensitive range Z of the magnetic sensor 32 at point B, the magnetic sensor 32 is turned on as shown in FIG. The control unit 36 stores the pulse signal count number P1 at this point in the memory (RAM) 38.

Subsequently, the servo motor 22 is rotated to move the movable die plate 16 (magnetic body 34) in the same direction, and when it passes point C, the magnetic sensor 32 is turned off. The control unit 36 stores the pulse signal count P2 at this point in the memory (PAM) 38.

Furthermore, after rotating the servo motor 22 a little to ensure that the magnetic body 34 leaves the sensitive range Z of the magnetic sensor 32, the servo motor 22 is then rotated in the opposite direction to change the moving direction of the moving die plate 16 (magnetic body 34). It reverses and continues to move, and the magnetic body 34 is connected to the magnetic sensor 32.
The number of pulses P3 of the pulse signal at time D when it enters the sensitive range Z is stored in the memory (RAM) 38.

Furthermore, the rotation of the servo motor 22 is continued to move the movable die plate 16 (magnetic body 34) in the same direction, and when it passes point E, the magnetic sensor 3
2 turns off. The count number P4 of pulse signals at this point is stored in the memory (RAM) 38. Furthermore, rotate the servo motor 22 a little, and
The rotation of the servo motor 22 is stopped to stop the movement of the movable die plate 16 (magnetic body 34). The control unit 36 stores the pulse signal count number P5 at this point in the memory (RAM) 38.

Next, in the calculation unit 37, based on the data of the count numbers P1, P2, P3, P4 and P5 of the pulse signal, points B and C are calculated according to the following equation (2).
Find the average midpoint X between the midpoint of , and the midpoint between point D and point E, and use the average midpoint as the origin.

=P5−P ₁ +P ₂ +P ₃ +P ₄ /4+a ………(2) Similar to the above formula (1), a in the formula is the value of the mold clamping completion position, and when the mold clamping completion position is the origin, , a=0. Also, if the mold clamping completion position is the origin,
The value is 1/2 of the number of pulses generated from the encoder 30 when the crank arm 21 rotates once.

In this way, the origin is found at the point A when the power is turned on.
By resetting the number of pulses from 1 to 1 to reach the origin, the crank mechanism can be controlled thereafter with the origin = 0 pulses.
Furthermore, by determining the origin as described above, the number of pulse signal counts from the origin to the current stop point F is known, so the stop point F can be accurately determined.

In particular, in this second origin finding method, the effects of hysteresis on the drive system of the crank mechanism and the magnetic sensor 32 are canceled out.
It can be used for prizes because it allows for more accurate origin determination.

That is, when the servo motor 22 rotates forward and the movable die plate 61 moves from point A to point C, and when the servo motor 22 rotates in reverse and the movable die plate 61 moves from point D to point F, The direction of the crushing of the drive system in the crank mechanism is completely opposite.

Therefore, by calculating the average value of the midpoint between point B and point C and the midpoint between point D and point E,
Backlashes in different directions are canceled out, which allows for more accurate position control.

Further, when the magnetic sensor 32 is used as the proximity sensor as in this embodiment, the hysteresis of the magnetic sensor 32 is canceled out in the following manner. That is, points C and E, where the magnetic sensor 32 changes from on to off, are symmetrical with respect to the intermediate point X, and the degree of hysteresis applied at points C and E is exactly opposite.

Therefore, by calculating the average value of the midpoint between points B and C and the midpoint between points D and E, hysteresis in different directions is canceled out, and an origin that is not affected by hysteresis can be calculated. be done.

In the above embodiment, a case has been described in which the mold clamping completion point is used as the origin, but the mold opening completion point, which is completely opposite to this, may be used as the origin.

In addition, the origin does not necessarily have to be the dead point of the movable part when the crank arm is fully extended or contracted, but the dead point can be set very close to the dead point, for example at the rotation angle of the crank arm. (0 degrees or 180 degrees)
In some cases, the origin is set at a position shifted by about 0.5 degrees or 1 degree.

Further, in the above embodiment, a magnetic sensor is provided on the fixed side and a magnetic body is provided on the movable side, but conversely, a magnetic substance may be provided on the fixed side and a magnetic sensor may be provided on the movable side.

In addition, in the above embodiment, the origin is found by reciprocating the movable part in one direction or once, but if the movable part is reciprocated multiple times and the average value is calculated, the precision can be improved. It is possible to find the origin.

Although a magnetic sensor was used as the proximity sensor in the above embodiment, other proximity sensors may also be used.

In the above embodiment, a mold clamping device of an injection molding machine has been described as the crank device, but the present invention is not limited thereto, and can also be applied to, for example, a mold clamping device of a die-casting machine, a crank device of a press machine, etc.

〔Effect of the invention〕

Since the present invention is configured as described above,
Unlike the conventional method, the origin position does not vary depending on the position of the proximity sensor, and the origin can be accurately determined. Further, there is an advantage that there is no need to provide a plurality of sensors for determining the origin, and the configuration is extremely simple.

If the method of calculating the origin by reciprocating the movable part once or multiple times as in the above embodiment is adopted,
It is possible to correct for bumps in the drive system of the crank device or for hysteresis when the proximity sensor is an air pressure sensor.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an injection molding machine according to an embodiment of the present invention, FIG. 2 is a functional block diagram showing the relationship between a mold clamping device and a control section in the injection molding machine, and FIG.
The figure and FIG. 4 are explanatory diagrams and timing charts for explaining the first origin finding method according to the present invention, and FIGS.
FIG. 7 is a partial side view of a mold clamping device in a conventional injection molding machine. 13... Tail stock, 14... Fixed die plate, 15... Tie bar, 16... Moving die plate, 17... Fixed mold, 18... Moving mold,
20...Pin, 12...Crank arm, 22...
...Servo motor for mold opening and closing, 24...Crankshaft,
25...Eccentric shaft portion, 26...Bearing, 30...
... Encoder, 32 ... Magnetic sensor, 34 ... Magnetic body, 36 ... Control section, 37 ... Central processing section, 3
8...Memory, 41...Pulse counter. P1,
P2, P3, P4, P5... Number of pulse signal counts.

Claims (1)

[Claims] 1. A crank mechanism body, a drive motor that drives the crank mechanism body, an incremental encoder that detects the rotation angle of the drive motor, and a movable part that reciprocates by the crank mechanism body. , a proximity sensor having a predetermined sensitive range and provided near the dead point of the movable part movement range so as to sense when the movable part approaches, a counter that counts pulse signals from the encoder, and a count from the counter. and a calculation unit that calculates the origin based on the signal and the on/off signal from the proximity sensor, and by rotating the drive motor, the movable part is moved via the crank mechanism main body, and the proximity sensor is activated. Based on the count number of the pulse signal at the first time point when it is turned on and the number of pulse signal counts at the second time point when the drive motor continues to rotate and the proximity sensor is turned off, the first time point and the second time point are determined. 2
A method for determining the origin of a crank device, characterized in that the intermediate point between the point in time and the point in time is calculated by the calculation section and the intermediate point is set as the origin. 2. A crank mechanism body, a drive motor that drives the crank mechanism body, an incremental encoder that detects the rotation angle of the drive motor, a movable part that reciprocates by the crank mechanism body, and a predetermined sensitive range. a proximity sensor provided near a dead point in the moving range of the movable part to sense when the movable part approaches, a counter that counts pulse signals from the encoder, and a count signal from the counter and an ON signal from the proximity sensor. , a calculation unit that calculates an origin based on an off signal, and a first point in time when the movable part is moved via the crank mechanism main body by rotating the drive motor and the proximity sensor is turned on. The count number of the pulse signal at the second point in time when the drive motor continues to rotate and the proximity sensor is turned off, and the movement of the movable part by reversing the drive motor. The number of counts of the pulse signal at the third point in time when the direction is reversed and the proximity sensor is turned on again, and the number of counts of the pulse signal at the fourth point in time when the drive motor continues to rotate and the proximity sensor is turned off again. A method for determining the origin of a crank device, characterized in that the intermediate point between the ON point and the OFF point of the sensor is calculated by the calculation unit within the sensitive range of the proximity sensor, and the intermediate point is set as the origin. 3 A crank mechanism body, a drive motor that drives the crank mechanism body, an incremental encoder that detects the rotation angle of the drive motor, a movable part that reciprocates by the crank mechanism body, and a predetermined sensitive range. a proximity sensor provided near a dead point in the moving range of the movable part to sense when the movable part approaches, a counter that counts pulse signals from the encoder, and a count signal from the counter and an ON signal from the proximity sensor. , a calculation unit that calculates the origin based on the off signal, and moves the movable part via the crank mechanism main body by rotating the drive motor, and at the first time point when the proximity sensor is turned on. , the count number of the pulse signal at the second point in time when the drive motor continues to rotate and the proximity sensor is turned off, and the direction of movement of the movable part by the drive motor being reversed. The number of counts of the pulse signal at the third time point when is reversed and the proximity sensor is turned on again, the number of counts of the pulse signal at the fourth time point when the drive motor continues to rotate and the proximity sensor is turned off again, and From the count number of the pulse signal at the fifth point in time when the drive motor continues to rotate for a while and then stops, the calculating section calculates the intermediate point between the on point and the off point of the sensor and the current stopping point within the sensitive range of the proximity sensor. A method for determining the origin of a crank device, characterized in that the intermediate point is set as the origin.