JPH0460742B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a position detection device for detecting the position of a piston so that the piston moves forward in an injection cylinder of a die-casting machine and stops at a predetermined position.

[Conventional technology]

Die-casting machines are equipped with an injection cylinder that injects molten metal into the cavity of the mold, and if the propagation state of the force applied to the molten metal by the plunger of this injection cylinder changes, the injection conditions will change slightly, affecting the quality of the molded product. Therefore, it is necessary to monitor the plunger so that the stopping position of the plunger is always constant for each shot. Conventionally, therefore, the stopping position of the plunger has been controlled by measuring the thickness of a solid material called a biscuit formed outside the cavity of a mold during injection.

Figures 2a and b are schematic diagrams of the injection cylinder and the mold of a conventional horizontal clamping/horizontal casting type die-casting machine, and Figure 5a shows the state before injection; b shows the state after injection.
In the figure, a cavity 3 as a space is formed between the clamped fixed mold 1 and movable mold 2, and a constriction 4 is provided below the cavity 3.
The injection sleeve 5 is inserted horizontally through. The injection sleeve 5 is provided with a pouring port 7 for injecting the molten metal 6, and the injection sleeve 5 also includes:
A plunger 9 of the injection cylinder 8 is slidably fitted. Both ports of the injection cylinder 8 are connected to a hydraulic pump 10 and a tank 11 via electromagnetic valves, and when the electromagnetic valves are opened and closed, a piston 12 moves forward and backward, and a plunger 9 connected to the piston 12 by a coupling ring 13 is connected to the injection sleeve 5. It is configured to move forward and backward within the space. Furthermore, the limit switch 1 is attached to the coupling ring 13 by moving the piston 12 back and forth.
A striker 17 that opens and closes 4, 15, and 16 is fixed. Here limit switch 14,1
6 detects the forward limit and backward limit of the piston 12, and limit switch 1
5 is a command for changing the moving speed of the piston 12 during injection.

With this structure, when the molten metal 6 is injected into the injection sleeve 5 from the pouring port 7 in FIG. As shown in b, the molten metal 6 is injected into the cavity 3. The injection speed is increased when the tip of the striker 17 leaves the contact point of the limit switch 15. After injection, when the molten metal 6 solidifies and cools, the movable mold 2 is opened and the cast product in the cavity 3 is taken out. At this time, the solidified material 18 in the constriction 4
The biscuit 19, which is the solidified material inside the injection sleeve 5, is taken out along with the product, so by hitting the thin solidified material 18 with a hammer or the like and breaking it,
Solids 18 and biscuits 19 are separated from the product.

In such a casting operation, if the thickness of the biscuit 19, indicated by the symbol _l3 in the figure, is measured and controlled so that it always remains constant, the quality of the product will not only be uniform as described above, but also The mischatch is eliminated by making the connection with the product take-out device constant, and if the biscuit thickness _l3 is controlled to be small, unnecessary solids are reduced and the product yield is improved.

Conventionally, as a means for measuring the thickness of the biscuit 19, a magnetic scale fixed to the striker 17 has been used. This magnetic scale has magnetized and non-magnetized parts arranged alternately by providing a large number of notches at regular intervals in a long and thin magnetic material, and detects the presence or absence of magnetic flux using an external detector. In the case of a moving object, that is, the injection cylinder 8, both the displacement of the striker 17 and the integral plunger 9 are known. In this case, the length until the plunger 9 comes into contact with the movable mold 2 without the molten metal 6 is measured _{in advance as shown by the symbol l 1 in} FIG.
_The value of l ₃ is determined by subtracting the amount _of movement until the completion of casting, which is indicated by reference numeral _{l 1 in} FIG.

[Problem that the invention seeks to solve]

However, such a magnetic scale as a conventional position detection means has the advantage that it can easily monitor the injection speed and the state of change in the injection speed due to increase/deceleration by dividing the amount of displacement by time. The device itself and its control device are extremely expensive and cannot be easily installed, and the structure becomes complicated when trying to eliminate the accumulation of magnetic powder.
There has been a demand for the development of a position detection device that is relatively simple in structure and operation and can be provided at low cost, not only for injection cylinders but also for various fluid pressure cylinders such as hot water supply cylinders.

[Means for solving problems]

In order to solve such problems, the present invention detects a piston-side member that advances and retreats integrally with the piston of the injection cylinder and a predetermined reference position of the piston-side member that is disposed in its advancement and retreat path and issues a signal. In addition to providing multiple fixed switches,
a rotary encoder connected to a rotating shaft in a drive system by a driving means and connected to a counter; a slider that is driven forward and backward in a direction of movement of a piston-side member by rotation of the rotating shaft; and a piston-side member fixed to the slider. It consists of a movable switch that opens and closes its contacts at A measuring means for counting and converting into the position of the piston was provided to detect the position of the piston.

[Effect]

When the output of the measuring means to the piston is calibrated in advance, the piston is moved forward for work, and the switch is moved at a predetermined reference position at the limit of its advancement, the relative positional relationship between the piston side member and the switch is The measuring means receives the signal and counts the amount of movement of the switch from the reference position to the transmission position and converts it into the position of the piston.

〔Example〕

1 to 3 show an embodiment of a position detection device for an injection cylinder of a die-casting machine according to the present invention, FIG. 1 is a vertical sectional view of the injection cylinder of a die-casting machine, and FIG. 2 is a schematic configuration diagram, FIG. 3 is an explanatory diagram of the operation. Components in the figure denoted by the same reference numerals as those in FIGS. 5a and 5b have the same configuration, so detailed explanation thereof will be omitted. Clamped mold 1,
An injection sleeve 5 having a spout 7 is inserted into the injection cylinder 2 so as to communicate with the cavity 3 through the constriction 4. It is slidably inserted into the injection sleeve 5. Then, when the piston 12 is advanced after supplying the molten metal 6 into the injection sleeve 5 from the pouring port 7, the plunger 9 moves forward together with the piston 12, and the molten metal 6 is injected into the cavity 3. FIG. 2 shows a state in which the plunger 9 has moved forward and injection has been completed, and the above-mentioned biscuit 19 is formed at the end of the injection sleeve 5.
Reference numeral 17 denotes a striker as a piston side member, which moves forward and backward integrally with the piston 12 by being fixed to the coupling ring 13, and the three limit switches 14, 15, and 16 are arranged in its forward and backward path.

The injection cylinder 8 configured as described above has
A position detection device 20 is attached. That is,
Front and rear integral brackets 22 and 23 connected by a guide shaft 21 are fixed to the outer peripheral surface of the injection cylinder 8 as a fluid pressure cylinder.
A screw shaft 24 parallel to the screw shaft 1 is rotatably supported by the front and rear brackets 22 and 23 via ball bearings. 25
is a slider to which a limit switch 26 shown as an example of a detection switch to be described in detail later is fixed, and a bush 27 fitted to the slider is slidably fitted to a guide shaft 21. Further, the threaded pipe 28 fitted on the slider 25 is connected to the threaded shaft 2
4 is screwed together. By doing this, when the screw shaft 24 rotates in the forward and reverse directions, the slider 25 is guided by the guide shaft 21 and reciprocates in the forward and backward direction of the piston 12, and the limit switch 26 integrated with the slide 25 also reciprocates. 29 is bracket 22
The motor serves as a screw shaft rotation driving means, and is connected to the screw shaft 24 by a coupling 30, and rotates in response to a command from a motor control device 31 to rotate the screw shaft 24 and set the limit switch 26 to a predetermined position. It is structured so that it can be advanced during the period of . 32 is a rotary encoder that is electrically connected to the counter 33 and constitutes a measuring means, and is connected to the screw shaft 24 by a coupling 34, and when the contact point of the limit switch 26 comes into contact with the striker 17, A signal is generated by detecting the correspondence between the limit switch 26 and the limit switch 26, and a counter 33 counts the amount of movement between the reference point of the limit switch 26 and the emitted signal.
It is configured to convert to position 2. That is, for example, when the piston 12 is stopped at the casting completion position, when the screw shaft 24 is rotated by the drive of the motor 29 and the slider 25 is advanced, the connection point of the limit switch 26 comes into contact with the striker 17, so that a signal is generated. Since the rotary encoder 32 receives and outputs this, the counter 33 counts the amount of movement of the limit switch 26 based on this output and converts it to the position of the piston 12 at the time of completion of casting. Therefore, if the amount of movement of the piston 12 to its forward limit is known in advance, the thickness of the biscuit 19 can be determined.

The operation of the position detection device constructed as above will be explained by taking as an example the operation of measuring the thickness of a biscuit. Before the mold clamping is completed and the casting operation is started, the rotary encoder 32 is first calibrated and the dimensions indicated by reference numeral _l1 in FIG. 5a are determined according to the new mold dimensions. That is, as shown in FIG. 5a, the motor 29 is rotated while the piston 12 is retracted to its retraction limit, and the slider 25 is moved to its forward limit, where it abuts the bracket 22, as shown in FIG. 3a. In this state, the rotary encoder 32 is calibrated using this as a reference point. After calibration, move the piston 12 to the plunger 9 without adding molten metal 6.
It is advanced at low speed until the tip comes into contact with the mold 2.
In this state, the limit switch 26 is at the forward limit position and is turned on. Therefore, the motor 29 is rotated in the opposite direction as shown in FIG.
After retracting the slider 25 until it turns OFF,
The motor 29 is rotated forward and the slider 25 is advanced until the limit switch 26 is turned on again as shown in FIG. 3c. After that, slider 25
Continue to advance the slider 25 to bring it into contact with the bracket 22 again as shown in FIG. 3d. The third limit switch 26 begins to operate.
The rotary encoder 32 outputs an output at the position shown in FIG. The stroke of the plunger 9, which is counted by the instrument 33 and converted into the position of the piston 12, is obtained by the reference numeral _l1 in FIG. This stroke l ₁ is a fixed value corresponding to the dimensions of molds 1 and 2, so this operation is performed once for one type of mold.
Just do it once in a while.

After preparing in this way, bracket 22
While the slider 25 is advanced until it contacts the slider 25, the piston 12 is moved back to the retraction limit, and after injecting the molten metal 6 into the injection sleeve 5 from the pouring port 7, the piston 12 is moved to the casting completion position shown in FIG. When the metal is advanced, the molten metal 6 is injected into the cavities 3 of the molds 1 and 2, and solidifies into a product. The product includes a solidified material 18 within the constricted portion 4 and a biscuit 19 below it. Therefore, in this state,
In the same way as when calculating l ₁ , the slider 25 is moved backward until the contact point of the limit switch 26 leaves the strike squid 17 and turns OFF by reversing the motor 29, and then the slider 25 is moved forward again.
The contact point of the limit switch 26 is pressed down by the striker 17 and turned ON, and the rotary encoder 3
2 is outputted and the arithmetic unit 33 counts it, so that the value of l ₂ shown in FIG. 2 can be found.
Therefore, this l ₂ and the previously known l ₁
The difference between l ₁ - l ₂ = l ₃ or biscuit 19
The thickness of the biscuit 19 after each injection can be obtained by performing the operation for determining l ₃ after each cycle of casting is completed.

Furthermore, in the present invention, the forward stop position of the piston is measured by providing a limit switch 26 and moving it, but normally the limit switch is turned on by pushing the detection member left and right and back.
It is a device that detects OFF, and the position where it detects ON and the position where it detects OFF are slightly different, so
When detecting a position, if the reference point is measured with ON, it is also necessary to measure with ON when actually measuring. To explain this in more detail using Figure 3, first,
If the reference point is detected with ON when the slider 25 is in contact with the bracket 22, the piston 1
I would like to measure the stop position during forward movement of 2 when it turns ON, but if I measure this when it changes from Figure 3 a to Figure 3 B, I will measure it when it turns OFF. Therefore, it cannot be measured accurately.
Therefore, since the position shown in Fig. 3c is to be measured, in the apparatus of the present invention, the position is measured from Fig. 3a to Fig. 3b, and then from Fig. 3c. In other words, limit switch 26 is turned on and off.
-ON, which is also a feature of the present invention.

In this way, if the above movement is performed with the reference point at the forward limit position shown in FIG. 3a, the injection stop position will be relatively forward, so after injection, the limit switch 26 can be moved from the forward limit position shown in FIG. The distance to move to Figure 3b may be relatively short, but since the striker 17 contacts the limit switch 26 during injection,
The mechanical friction of the limit switch 26 is not necessarily good. Therefore, it is better to set the reference point at the rear and turn off the limit switch 26, and after injection, move the limit switch 26 forward, turn on the limit switch 26, and then move the limit switch 26 back a little and turn it off. Since the striker 17 does not come into contact with the limit switch 26 during the operation, there is no mechanical friction, which is advantageous. That is, in this case, the limit switch 26 becomes OFF-ON-OFF, which is also a feature of the present invention. However, in this case, there is a disadvantage that it takes a little more time to move the limit switch 26 forward from the reference point of the reverse limit, but instead of starting the limit switch 26 from the 0 point each time, the reference point is moved forward. If the position is determined in advance near the injection stop position, the time will be shortened and wear on the limit switch 26 will be reduced.

FIG. 4 is a side view of the main parts of a position detecting device according to another embodiment of the present invention, and the same reference numerals as in FIG. In this embodiment, a fluid pressure cylinder 35 is used as a means for driving the slider 25 forward and backward in place of the motor 29 of the previous embodiment, and a rotary encoder 32 is rotated by a rack 36 and a pinion 37. That is, the piston rod 38 of the fluid pressure cylinder 35 attached to the bracket 22
has an active end connected to a slider 25 supported by the guide shaft 21, and a rack 36 connected to the slider 25 is pivotally supported by the bracket 23 so as to be movable forward and backward, and meshes with a pinion 37 of the rotary encoder 32. It's on. In this way, when the fluid pressure cylinder 35 is operated, the slider 25 moves forward and backward together with the piston rod 38, and the rack 3
6 and the pinion 37, the rotary encoder 32 rotates. The position detection operation is exactly the same as in the previous embodiment.

In each of the above embodiments, a contact type limit switch 26 is used as an example of a switch for detecting the response of the striker 17, which is a piston side member, but a non-contact type proximity switch may also be used.

Furthermore, in each of the embodiments described above, an example has been shown in which the slider 25 is moved back to a position where the limit switch 26 is turned OFF and then moved forward again to a position where the limit switch 26 is turned ON during the operation for position detection. This was done in consideration of the large difference in hysteresis between when the limit switch 26 goes from ON to OFF and from OFF to ON. If the difference is within an error that can be ignored with respect to the position of the piston 12, scanning in only one direction is sufficient instead of the reciprocating scanning described above. That is,
Move slider 25 from bracket 22 to bracket 2.
3 or block 2
3 toward the bracket 22 to turn the limit switch 26 from ON to OFF or
The position of the piston 12 may be obtained by detecting the point at which the signal changes from OFF to ON using the rotary encoder 32.

Furthermore, in each of the embodiments described above, an example was shown in which the position is detected using the position where the slider 25 abuts the bracket 22 as a reference point, but moving the slider 26 to the position where the slider 26 abuts the bracket 22 every cycle is Since this is not a good idea in terms of the durability of each member, it is desirable to do this because it is possible to calibrate the output of the rotary encoder 32 relative to the piston 12 using a position a certain distance away from the bracket 22 as a reference point. Of course,
Instead of using the position where the slider 25 abuts the bracket 22 as the reference point, the position where the slider 25 abuts the bracket 23 is used as the reference point, and the slider 25
It is also possible to detect the position by moving the

Further, in each of the above embodiments, the present invention was implemented for measuring the thickness of a biscuit in an injection cylinder of a die-casting machine.
The present invention can be similarly implemented for detecting the piston position of various fluid pressure cylinders, such as for measuring the deceleration position near the forward limit of a water supply cylinder, or controlling the amount of poured hot water by detecting the piston position of a fluid pressure cylinder for hot water supply.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in the position detection device for a fluid pressure cylinder,
A piston-side member that advances and retreats integrally with the piston of the injection cylinder, and a plurality of fixed switches that are arranged in the path of movement of the piston-side member and that detect a predetermined reference position of the piston-side member and issue a signal, and are driven by a driving means. A rotary encoder connected to a rotating shaft in the system and connected to a counter, a slider that is driven forward and backward in the direction of movement of a piston-side member by rotation of the rotating shaft, and a contact that is fixed to this slider and opens and closes with the piston-side member. When the piston is placed at a predetermined reference position by a signal from the fixed switch, the amount of movement of this switch from the reference point to the transmission position is counted and the piston is moved. A measuring means for converting the position to the position of the piston was provided to detect the position of the piston.

As in the embodiment, the present invention is used in the injection device of a die-casting machine, and the injection stroke is controlled based on the thickness of the biscuit obtained by measurement, so that the thickness of the biscuit is constant every time. If controlled, the injection conditions will be constant every time, the quality of the injection product will be uniform, and high quality injection products can be obtained. It also becomes easier to take out the product.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the position detection device for an injection cylinder of a die-casting machine according to the present invention, FIG. 1 is a longitudinal cross-sectional view thereof, and FIG. 3 is a schematic diagram of the configuration, FIG. 3 is an explanatory diagram of operation, FIG. 4 is a side view of the main part of a position detection device showing another embodiment of the present invention, and FIG.
Figures a and b show schematic configuration diagrams of a conventional position detection device for an injection cylinder of a die-casting machine, with Figure 5a showing the piston retracted position and Figure 5b showing the piston forward position. 1, 2... Mold, 3... Cavity, 5... Injection sleeve, 6... Molten metal, 8... Injection cylinder,
9... Blungier, 12... Piston, 17...
Striker, 19... Biscuit, 20... Position detection device, 22... Bracket, 24... Screw shaft, 25... Slider, 26... Limit switch, 29... Motor, 32... Rotary encoder, 33 ... Counter, 35 ... Fluid pressure cylinder, 36 ... Rack, 37 ... Pinion, 38 ...
... Piston rod, l ₁ ... Maximum stroke from the piston's retraction limit to the forward limit, l ₂ ... Stroke from the piston's retraction limit to the casting completion position, l ₃ ...
...The thickness of the biscuit.

Claims (1)

[Claims] 1. A piston-side member 17 that is fixed to the piston 12 and moves back and forth together with the piston 12 by the fluid pressure of the injection cylinder 8, and a piston-side member 17 that is fixed to the machine base and arranged in the movement path of the piston-side member 17. A plurality of fixed switches 16, 1 detect a predetermined reference position of the piston side member 17 and issue a signal.
5 and 14, and a rotary encoder 32 connected to a rotating shaft 24 in a drive system by a driving means 29 and connected to a counter 33, and a rotary encoder 32 which is connected to a rotating shaft 24 in a drive system by a driving means 29 and connected to a counter 33; It consists of a slider 25 that is driven forward and backward, and a movable switch 26 that is fixed to the slider 25 and whose contacts are opened and closed by the piston side member 17,
When the piston 12 is placed at a predetermined reference position by the signals from the fixed switches 14 and 16, the amount of movement of the switch 25 placed at the predetermined reference point from the reference point to the transmission position is counted and the piston 12 is 1. A position detection device for an injection cylinder of a die-casting machine, characterized in that the position of a piston 12 is detected by providing a measuring means for converting the position into a position of .