JPH0736960B2 - Device for monitoring the position of mechanical elements - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention determines the position of a machine element, such as a machine head of a machine tool, that performs a feed motion and a return motion in a direction toward and away from a workpiece during machining of the workpiece. A device for monitoring, which is provided with an electro-hydraulic type drive device for controlling the movement of mechanical elements, and the control device is provided with an electric target value and a follow-up adjustment in which the actual value is fed back. Claim 1 having a valve and otherwise
A type having a characteristic that defines the type of device described in the superordinate concept of the section.

The working movement of the tool is tracked, that is to say the mechanically monitored actual value of the tool position, for example, is due to the type of control of the movement course relative to the electronically given setpoint value of the tool position for the workpiece to be machined. Tonatetsu traction error ΔS
In hydraulically driven machines that are only delayed by time, a monitoring device is usually provided to check if the tool has completed its working stroke, such as in the case of a press or stamper. Whether the tool has reached a predetermined position and / or when the tool has reached a predetermined position, in order to accurately detect the end of the work stroke when it relates to whether the work result actually reaches the defined end position. It is necessary to be able to confirm whether the predetermined position has been reached. On the other hand, in a punching or nibbling machine that works cyclically, the work cycle must be able to be carried out with the highest possible repetition period, so that after reaching the work piece it can be considered that the work actually completes the work stroke. It is usually sufficient to monitor the position of.

For such monitoring it is known to use limit switches which are switched by an actuating member which moves with the tool. However, monitoring with limit switches is difficult because such switches must be very accurately adjusted and, in addition, must be very accurately adjustable to different travel distances depending on the workpiece and tool conditions. Is. Furthermore, in this case, in the limit switch, the response characteristics change after long-term use, and even when the machine is always used to machine the same workpiece with a given tool type, post-adjustment is possible. You will need it. Furthermore, if the circuit amplification value of the tracking adjustment circuit must be lowered to perform the work, it is often the case that an inconveniently long cycle time must be accepted. This is because it is necessary to wait until the workpiece reaches the end of the work movement most suitable for detection with the limit switch after a long adjustment time due to low circuit amplification.

The object of the present invention is thus to ensure a simple and precise adjustment of the tool position to be monitored and to enable a significant reduction of the cycle time when the tool makes feed and return movements at high repetition frequencies in a periodic work cycle. To provide a device of the type mentioned at the outset.

This problem has been solved according to the invention by the features stated in the characterizing part of claim 1.

According to the invention, the monitoring of the predetermined position of the tool movement near the end point or dead point defined by the desired value of the tool movement is performed by the distance of the adjusting valve actuating member from the reference position of the adjusting valve actuating member. Is monitored, and when this distance falls below a predetermined minimum defined value and the tool approaches the dead center, a close position switch positional monitoring signal is emitted.

The advantage of the device according to the invention is that the monitoring device can be adapted electronically to the appropriate end position setpoint value so that the tool can be adapted to the travel path traveled without costly adjustment or adjustment work. Is. In order to adapt the device to a given travel height of the tool and to a given material thickness or deformation depth of the workpiece, it is sufficient to program the target dosing device in a targeted manner. In this case, the most suitable setpoints can be obtained quickly and without great effort during a few small load work strokes. By choosing a sufficiently large conversion ratio that the displacement of the valve actuating member translates into, for example, a rotational excursion of the actuating member of the proximity switch, the monitoring device for changes in the position of the valve actuating member can be provided in a simple manner. A high degree of responsiveness and thus a high accuracy of the actual position value monitoring is achieved.

The target position dose is controlled to give an end position that is ahead of the end position that must be achieved by the tool, and the actual position indication signal is activated just before the proximity switch has moved the tool completely through the required working stroke. Adjustment and the display signal of the proximity switch then releases the setpoint input for the return movement, the adjustment time that the tool has to wait before reaching the target end position is similar. Cut into pieces. This is particularly advantageous for machines that work cyclically. This is because the cycle times are significantly reduced, which leads to an increased economy of machines equipped with the device according to the invention.
The device according to the invention, which seeks to monitor that the workpiece has reached an end position which must be reached exactly as is necessary, for example, in the case of a shape press or an embossing machine, is in fact relevant for target dosing. The target value is controlled so that it is delivered rather than corresponding to the travel distance traveled, and the target value is displayed when the actual position display signal of the proximity switch indicates that the tool is located in the immediate vicinity of the position which causes the desired workpiece deformation. Administration can be repositioned to this position. This also results in the required reduction in feed time.

The features of claim 2 define the basic construction of the proximity switch to be used within the framework of the device according to the invention. This proximity switch is defined by the third and fourth claims.
A Hall generator can be used as the switch element as shown in the paragraph, or a single or a plurality of photoelectric boxes can be used as shown in claim 5.

By constructing the proximity switch as described in claim 6, there is an advantage that the proximity switch can be matched with the flow-through characteristics of different follow-up control valves in a simple form.

According to claim 7, the device according to the invention has the possibility of use in which it is particularly advantageous to use in terms of a reduction in cycle time.

The details of the invention and other features are described in the description of specific embodiments with reference to the drawings. In the drawings, FIGS. 1a and 1b are block diagrams of a tracking-controlled electrohydraulic drive device having a device of the present invention for monitoring the position of a valve actuating member of a tracking control valve provided in the frame of a tracking control circuit. It is the figure which showed the structure of the said follow-up control valve. FIG. 2 is a schematic side view of a monitoring device according to the invention provided in the frame of the drive of FIGS. 1a and 1b. FIG. 3 shows the monitoring device of FIG. 2 III of FIG.
FIG. 3 is a sectional view taken along line III-III. Figures 4 and 5 are second
FIG. 4 is a diagram for explaining the function of the monitoring device shown in FIG. 3 and FIG. 3.

In order to explain the device shown in FIGS. 2 and 3 for monitoring the actual position of a tool, such as a punching tool or a pressing tool, which can be driven by a hydraulic drive device, FIGS. 1a and 1b are first described. The purpose of using the device of the present invention will be described with reference to and.

A punching machine, for example a Nipple machine, which is shown only schematically by a double-acting cylinder 11 and a punching tool 12 driven thereby, operates in a cyclically repeated punching cycle.
In such a punching machine, an electro-hydraulic type follow-up adjusting valve having a structure known per se, which is generally designated by reference numeral 13, is provided for controlling the fast-forwarding, the load-feeding and the fast-returning movements. This follow-up control valve works with electrical target value delivery and mechanical actual value feedback.

The principle structure of this follow-up regulating valve is necessary to explain the device 10 of the present invention and to some extent should be understood from FIG. 1b. The follow-up control valve is constructed as a 4 / 3-way control valve and has four valve inserts with control edges that can be adjusted independently of each other. These valve inserts are designed as conical seat valves 16, 17, 18, 19 in the illustrated embodiment. These valves are paired and controllable to an open or flow-through position by axial movement of the valve actuating member 14. in this case,
The opening takes place against the action of the return spring. Of course, a piston valve can be provided instead of the conical valve seat valve.
In the selective flow positions I and II of the follow-up adjusting valve 13, both working chambers 22 and 23 of the drive cylinder 11 are selectively connected to the P high pressure outlet of the hydraulic pressure supply source or the tank T. 1a
In the figure, the following position of the follow-up regulating valve is assigned to the rapid feed and the load feed of the punching tool 12 and the passing position indicated by the reference symbol II is the punching tool 12 or the drive cylinder 11.
Assigned to the Stonon 24 quick-rewind movement.

Position setpoint dosing, which also results in tool speed dosing by time continuation, is effected by the rotation of the spindle nut 26, which is controlled by a stepper motor. The spindle nut 26 is rotatably supported on a sleeve 27. The sleeve 27 is axially reciprocable within the valve casing 29 in the direction of the longitudinal axis 28 of the valve casing 29, but is not rotatable with respect to the casing. This sleeve has a valve actuating member which together with the axial movement of the sleeve.
14 are combined. In the shown reference position of the follow-up regulating valve 13, all four conical seat valves are closed.
By rotating the spindle nut clockwise as viewed in the direction of arrow 31, the valve actuating member 14 shifts the displacement amount ε ₁ to the left as viewed in FIG. 1b. This ensures that both conical seat valves 16
And 17 are controlled to be opened, whereby the working chamber 22 above the drive cylinder 11 is connected to the P pressure outlet and the working chamber 23 below the drive cylinder 11 is connected to the tank of the hydraulic pressure supply source (not shown). It This corresponds to the flow position I in which the piston 24 is moved downwards. When the spindle nut 26 rotates counterclockwise, the valve actuating member 14 deviates from the right offset position ε ₂ as shown in Fig. 1b, and the follow-up adjusting valve 13 is assigned to the return movement of the hydraulic cylinder 11. Controlled by II. Piston 24 of drive cylinder 11 or punching tool 12 driven by it
The feedback of the actual value of the position is done through a rack mechanism, indicated generally by the numeral 32. The rack 33 of this rack mechanism moves together with the piston 24, and the pinion
34 is non-rotatably connected to the feed back spindle 36. The feedback spindle 36 itself is mounted in the casing 29 of the follow-up regulating valve so as not to move axially. The feed back spindle 36, in the particular embodiment shown, is mounted via a screw ball 37 on the spindle nut 26.
It meshes with the female screw. The function of the follow-up regulating valve 13 described with respect to the structure is that the rotational movement of the feedback spindle 36 transmitted by the rack mechanism 32 causes the valve operating member 14 to be displaced. This deviation is opposite to the movement of the spindle nut 26 due to the delivery of the setpoint value of the spindle nut 26, and when the actual position value and the setpoint position are equal, the valve actuating member 14 is the basic element shown in FIG. 1b. Located at position 0.

The device 10 according to the invention for monitoring the setpoint / actual value of the position of the tool 12 detects the basic position of the valve actuating member or the tool defines a defined distance from the end position, which marks the end of the working cycle, for example. Is configured to respond to the position taken by the valve actuating member when in the open position.

The second is to explain the structure of the target / actual value monitoring device 10.
Details will be described with reference to the drawings and FIG.

The target / actual value monitoring device 10 according to the present invention is a proximity switch according to the basic structure. In this proximity switch, the valve actuating member 14 causes a predetermined pulling error Δ due to the position target value administration.
A characteristic signal is produced when the valve actuating member returns to the basic position after being displaced from the reference position by the section ε ₁ or ε ₂ associated with s. This is the case during the end of the work-feed movement, where the target value dosing in the tool-feed direction ends. In this operating period, the drive cylinder 11 is determined by the circuit amplification of the adjustment circuit, With the adjustment time T given by, the vehicle gradually enters the position determined by the final price of the target placement administration. In this case, in the above equation
Kv shows the circuit amplification of the tracking adjustment circuit, and Δx shows the allowable position error that is still present or can be confirmed after the adjustment time period has elapsed. In this case, this position error is smaller than the step width of the target value administration.

This adjustment time is, in practice, extremely large, for example on the basis of the reduction of circuit amplification combined with the work of switching fast-forward to load-operated feed, and in the extreme case of the time required for fast-forwarding of the punching tool 12 and square load feeding. It could be several times. Instead of waiting for this adjustment time, after the tool 12 has gone through a working stroke, ie after having punched out the workpiece 38 (see FIG. 1a), the target / actual value monitoring device according to the invention is Proximity switch shown by 40, the output signal to switch the drive device from load feed to fast return operation, the valve actuating member has not yet reached the basic position that characterizes the equality of the actual position value and the desired position value, It is designed to occur when still located at a small distance from this basic position, which corresponds to part of the maximum excursion.

In the embodiment shown in FIGS. 2 and 3, the operating member of the proximity switch 40 is used.
A circular disc 41 is provided as 41, which is supported in the casing 29 of the follow-up regulating valve about an axis 42.
This axis 42 extends at right angles to the longitudinal axis 28 of the follow-up regulating valve 13 along which the movement of the valve actuating member 14 takes place. In FIG. 2, the longitudinal axis 28 of the follow-up control valve extends perpendicular to the plane of the drawing. The valve actuating member 14 has a clutch finger 44 which is laterally spaced from the rotary shaft 42 of the actuating member 41 of the proximity switch 40 to the actuating member 41 via a finger clutch 43, and the deviation of the valve actuating member 14 is a disc. It is drivingly connected so as to be converted into rotation. In this case, the disc 41 is made in the direction of the arrow 46 in FIG. The disk-shaped clutch member 47 of the finger clutch is constructed as a U-shaped spring steel member. One leg of the U-shaped spring steel member is inserted into a radial hole of the rotary shaft 48 of the disc 41 and engages the clutch finger 44 of the finger clutch 43 without play. In this case, the U-shaped member limits the slot 49. This elongated hole 49 allows the compensating movement necessary for the rotation of the disc as the actuating member 41 between the disc 41 and the clutch finger 44.

The disk as actuating member 41 has a radius R which is approximately five times larger than the distance from the central axis 51 of the clutch finger 44 to the axis 52 of the bearing shaft 48 in a typical displacement. This means that the deviations of the edges 52 and 53, measured along the circumference of the disc, are five times greater than the deviations ε ₁ and ε _{2 of the} valve actuating member 14. With such a transmission ratio, the position of the valve actuating member 14 is within a range of 0.5 mm, and the proximity switch 40 is responsive to the angular movement of the edges 52 and 53 of the notch 54.
Therefore, it can be accurately measured up to 1/10 mm.

In the special configuration of the proximity switch, the proximity switch has a Hall generator 56. The outer edge 58 of the disc projects into the working magnetic field H of the Hall generator 56, which is oriented transversely to the disc as the actuating member 41, as indicated by the arrow 57. In this case, the output signal of the Hall generator 56 is a high level signal when the disk edge 58 of the disk is in the range of the magnetic field 57, and a low level signal when the disk cutout 54 reaches within the magnetic field 57. . The edges 52 and 53 of the U-shaped edge notch 54 are edge notches 54
With respect to the radial central plane 59 of the disc, the valve actuating member 14 is located at the same distance from the respective basic position in both alternative directions of movement and both possible directions of rotation of the disc
It is arranged so that the output signal level of the Hall generator 56 is changed at 46.

Of course, depending on the purpose of the monitoring device, notches 54 are provided so that when the valve actuating member moves in a selective direction towards the basic position, the proximity switch acts at different intervals from the basic position.
Can be formed.

It is also possible to use a radially projecting vane instead of a disc with a notch 54 open at the edge. Further, instead of the Hall generator, it is also possible to use a photoelectric box in which the light rays are blocked by radially projecting vanes provided in place of the disk edges 58, 52, 53 or the notches 54. It is also possible to use inductive or capacitive proximity switches within the framework of the target / actual value monitoring device according to the invention.

The typical functioning of the device 10 according to the invention will now be described with reference to FIG. 4 by taking a punching machine working in a cyclically repeated working cycle as an example.

FIG. 4 shows that the descending movement of the tool 12, which is initially directed as a fast-forward to the workpiece 38, has already transitioned to the load movement phase before the time point t ₀ , and the tool 12 moves loosely, but instead. The starting point is that the drive provides more feed force than is necessary to punch the workpiece 38. The actual position of the tool 12 whose time evolution is shown by a solid line in FIG. 4 in a curve 62 and the time curve written in a dash-dotted line in which the time evolution is indicated by 61 is in this case formula The difference is Δs given in. In this case, V is the feed rate, and Kv is the circuit amplification of the so-called tracking adjustment circuit. Without limiting generality, it was assumed that the traction error Δs above was approximately the same as the workpiece 38 thickness.

The punching tool 13 first moves toward the workpiece 38 at a constant speed. In this case, the tool contacts the upper side of the work piece 38 at time t ₁ . At this point the target dose has already corresponded to the working stroke.
That is, if the actual position corresponds to the target dose, the tool 12 has already penetrated the workpiece 38 and the punched edge of the tool 12 extends the height of the lower limiting surface of the workpiece 38. However, depending on the set point dosing, the tool 12 will carry out a further downward stroke until it corresponds to the end position 63 below the workpiece 38. In this type of target dosing, the lower end of the work piece 38 is aimed at for the drive to drive the tool 12 into the work piece 38 with full force. From time t _{2 the} target dose is the tool below the work piece 38
It is kept at a constant value corresponding to the 12 end positions. This end position should be reached by the tool only after a relatively long adjustment period, ie at time t ₅ . This is because the speed of the tool 12 approaching the position determined by the target value administration from the time t ₂ decreases exponentially.
The monitoring device 10 is adjusted to change the output signal level as the tool 12 pierces the workpiece 38. This is done at time t ₃ . From this point on, the return movement of the workpiece is provided by the setpoint dosing device as indicated by the rising branch portion 64 of the setpoint curve 61. In this case, the time point
At t ₄ , the equalization between the target value and the actual value is obtained.

As soon as it is known by the monitoring device 10 that the actual position value is feed back, that the workpiece 38 has been punched out, that is, the tool 12 has completed the working stroke,
The return movement of is started. In this case, the tool 12 does not have to wait until it has reached the position defined by the target dose, the adjustment time is expired, which causes the workpiece to move to time t ₂
The starting position for the next work cycle, which can only be reached after reaching the target position given by, can already be reached, for example at time t ₅ .

The type of setpoint dose and actual position feedback used in the present invention described so far is used when the working movements carried out by the tool 12 are carried out cyclically in the shortest possible cycle time, as is the case, for example, in a nipple machine. It is particularly advantageous. In such a use, it is not necessary to know when the work result has reached the position required to achieve the punching of the workpiece 38, but only to know if this position has been reached.

However, the device 10 of the present invention provides when the tool 12 has reached the position required to achieve the work result, i.e. when the stroke required to achieve a given workpiece deformation, for example in an embossing press, has been completed. Can be used to indicate that the tool 12 should not be sent any further from this point. In such an application, the device of the present invention is adjusted so that the position indicating output signal of the monitoring device 10 is emitted when the tool has traveled most of the stroke required to deform the desired workpiece. In other words, in this case, it is possible to start from the fact that the end position corresponding to the target value administration is also reliably achieved during the elapse of the adjustment time determined by the circuit amplification of the tracking adjustment circuit. Therefore, in such an application, the monitoring device 10 is adjusted such that a change in the output signal level occurs in FIG. 4 at the instant t ₅ ′ at which the tool substantially corresponds to the target end position.

Next, based on FIG. 5, it is possible to use the apparatus of the present invention which makes it possible to remarkably shorten the time period required to complete the working process of the press tool which causes the desired deformation even in the working process, the stamping process or the pressing process. Sex or driving style will be explained.

As an example of explanation of this driving mode, for example, a pressing process of pressing a thin body plate into a predetermined shape is assumed.

In FIG. 5, the time curve of the target value administration is shown by the alternate long and short dash line and the time curve of the actual position of the press tool is shown by the solid line in the same course curve as in FIG.

FIG. 5 shows the position of the pressing tool, which indicates that the tool moves from above and contacts the workpiece in load operation by a straight line 66 extending parallel to the time axis, that is, the horizontal axis of the diagram. ing. This contact is made at time t ₂ . A straight line 67 parallel to the transverse axis indicates the end position which the tool must reach. This end position is the position that the tool must reach in order to achieve the desired permanent deformation of the workpiece. The target dose indicated by the curve 61 ′ at the instant t ₁ corresponds for the first time to this position. As described in FIG. 4, the target value dosing exceeds the time points t ₁ and t ₂ and has a larger value until the time point t ₃ at which the tool reaches the lower position where the target value dosing is to be achieved. Will continue in. At the instant t ₃ ′, the tool does not reach this end position reliably, as shown by the actual value curve 62 ′. From time t ₃ , the target dose is kept constant at the curve 61 ″. At time t ₄ ′, the tool has only a very small distance from the end position, this time t ₄ ′. In the proximity switch 40, the position setpoint is returned to the value indicated by the straight line 67, which corresponds to the end position of the tool, at which the setpoint dose is set at time t ₅ . is the value. time t actual value of ₅ target dose and the tool substantially match the target value from the point of administration is kept to a value corresponding to the end position. time target value administration already t ₁ At a value corresponding to the end position of the work piece, which is significantly shorter than the adjustment time that must be waited for when the tool first reaches the end position at time t ₇ as shown in FIG. after the band △ t, already at time t ₆ in this case Assuming the completion of the engineering process, it is possible to start the return movement of the press tool.

Even with this mode of operation of the device according to the invention, a considerable reduction in the pressing or stamping process is achieved.

Claims (7)

[Claims] 1. A device for monitoring the position of a machine element, such as a machine head of a machine tool, which performs feed and return movements towards and away from the workpiece during machining of the workpiece. In order to control the progress of the feed and return movements, an electro-hydraulic type drive device is provided, and this drive device has a follow-up adjustment valve that works by electric target value dosing and mechanical actual value feedback. The regulating valve is provided with a valve adjusting member, which can be displaced by a target value administration from a basic position in which the valve adjusting member is located when the target value and the actual value are the same, which causes a deviation. Is controlled to open the valve through which the working medium flow is proportional to, and this working medium flow causes the drive device to be loaded in the direction to match the actual value to the target value. Direction In the type in which the displacement direction of the mechanical element also corresponds to the displacement direction of the mechanical element, a mechanical conversion device is provided, and the conversion device is provided for the valve adjusting member (14) of the follower adjustment valve (13). It translates the excursion into a larger excursion of the mechanical actuation member (41) of the proximity switch (40) associated with it, which proximity switch (40) sees in the excursion direction of that actuation member (41). For monitoring the position of a mechanical element, characterized in that it is arranged at a predetermined distance before the position taken by the actuating member (41) when the valve adjusting member (14) is in its basic position. Equipment. 2. An actuating member (41) of a proximity switch (40) is configured as a vane which can be rotationally driven by the excursion of a valve adjusting member (14), the vane having a notch (54) at its edge (58). ) Or a protrusion, and when the notch or protrusion enters the stationary functional member of the proximity switch (40), the position display output signal of the proximity switch (40) is transmitted. . 3. A valve adjusting member (14) of a follow-up adjusting valve (13) is configured as a valve operating member capable of reciprocating along an axis of the follow-up adjusting valve (13), and the valve operating member is a finger clutch (43). ) Is drivingly connected to the shaft (48), and the shaft (48) is rotatably supported about an axis (42) extending at right angles to the moving direction of the valve operating member, and the proximity switch (40). Of the Hall-generator, whose actuating member (41) of (1) is made of a ferromagnetic material and is fixed to the section of said shaft (48) projecting from the valve casing (29) and is thereby used as a proximity switch (40). 3. The device as claimed in claim 1, which is swivelable in the operating magnetic field (57). 4. The operating member (41) of the proximity switch (40) is configured as a disk or sector plate, and the peripheral edge of the disk or sector plate is the operating magnetic field (57) of the Hall generator as the proximity switch (40). Is projected into the range of the gap that is pierced in the lateral direction, and the edge of the disk or sector plate is notched (54)
Device according to claim 3, characterized in that the notch (54) penetrates into the gap range when the valve adjusting member (14) of the follow-up regulating valve (13) approaches its basic position. 5. The fixed functional member of the proximity switch (40) has a photoelectric box, and the blocking or release of the photoelectric of the photoelectric box caused by the displacement of the actuating member (41) of the proximity switch (40). The device according to claim 1, which emits a switch output signal indicating the position. 6. The method according to any one of claims 1 to 5, wherein the position of the proximity switch (40) that emits a position indicating signal related to the proximity of the follow-up control valve (13) is adjustable. The device according to item 1. 7. The work cycle is repeated at great frequency to monitor whether it is being used in a press drive to monitor a predetermined end position or whether a predetermined tool position has been passed during the work cycle. An apparatus according to any one of claims 1 to 6 for use in a drive of an obtained machine, for example a punching machine.