JPS6361136B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electro-hydraulic control device for compensating and reducing the table driving force in a tilting table device that tilts a table by engaging a worm and a worm wheel. .

[Conventional technology]

In a conventionally known tilting table device, a fan-shaped worm foil is formed on the lower surface of the table and integrated therewith, and the tilting table is supported tiltably and rotatably on a fixed base, and a worm is engaged with the worm wheel. This worm shaft is arranged in a bearing device on a fixed base so as to be rotatable. In a directly mechanically driven tilting table using such an irreversible rotation mechanism, a worm shaft thrust that constantly fluctuates acts in response to the load acting on the table or the tilt angle, and therefore the table rotation axis Due to changes in the table rotational moment relative to the centerline, that is, the table load, the contact pressure on the worm meshing tooth surfaces constantly fluctuates. Therefore, this type of tilting table cannot afford to reduce the setting accuracy of the tilting angle, for example, the indexing accuracy of the tilting table, and in terms of the tilting angle setting operation, it is difficult to use when the table has a large load or the equipment is large. In the design process, it was impossible to achieve basic accuracy due to the increased burden on the constituent elements of each part. In particular, regarding indexing accuracy, it is due to improvements in the manufacturing and meshing accuracy of the worm wheel and worm, the influence of torsion of the drive worm shaft, distortion or back gap of the worm meshing tooth surface, load fluctuation due to the inclination angle, etc. Improving indexing accuracy has never been easy.

[Problem to be solved by the invention]

The present invention is intended to eliminate the above-mentioned drawbacks of this type of conventional tilting table, and its purpose is to constantly reduce the meshing pressure generated on the worm tooth surface under a constant thrust that is independent of the table load and is reduced. This is intended to compensate for and reduce the driving force of the tilting table to be held.

The present invention connects a tilting table to a hydraulically actuated cylinder pivotally mounted on a fixed base so that the substantial tilting movement of the table is performed by powerful hydraulic drive, and reduces the table load acting around the rotation axis of the tilting table. A load detection element should be provided on the worm shaft to detect the axial thrust generated on the worm shaft that is operated in response to the rotational moment, and an electrical output signal should be sent out corresponding to a small reference worm shaft thrust selected in advance. a threshold output signal generator; a comparator that compares the threshold output signal with a detection output signal of the load detection element; an amplifier that amplifies the comparison difference output signal transmitted from the comparator; In addition to installing an electric operating circuit system consisting of an electric servo motor that operates in response to the amplification signal emitted from the width device,
This is achieved by setting up a hydraulic pressure control device that can control the hydraulic pressure introduced into both chambers of the hydraulic cylinder for driving the tilting table by the output shaft of the electric servo motor. Further, the hydraulic pressure control device set including the above-mentioned hydraulic actuation cylinder has a working hydraulic pressure supply and discharge circuit connected to a hydraulic pressure source and a return tank via a balancing relief valve for both chambers of the hydraulic actuation cylinder, and the above-mentioned balancing relief valve. a pilot hydraulic control circuit including a pair of remote control valves connected to each pilot port, and a servo motor that rotates in response to a differential input signal;
A transmission system transmits the rotation of the servo motor to the remote control valve, and the rotation of the servo motor adjusts and controls each pilot pressure so that it increases and decreases in opposite directions. It has a hydraulic control circuit that controls the hydraulic pressure introduced to the cylinder. The control aspect of driving force compensation of the tilting table according to the present invention is based on the viewpoint of keeping the axial thrust value generated on the operated worm shaft constant, and the detected axial thrust value and the target reference thrust value are A feedback control circuit is configured to reduce the axial thrust by changing the operating pressure difference between the two chambers of the hydraulic cylinder in accordance with changes in the comparison difference signal, and eventually the comparison difference signal becomes zero. When this occurs, the operation of changing the pressure difference supplied to both cylinder chambers is stopped, the pressure difference is determined, and the axial thrust value is maintained at the target value.

The present invention will be described in detail below with reference to embodiments shown in the accompanying drawings.

〔Example〕

FIG. 1 schematically shows only the manner in which a hydraulic cylinder 7 is connected to a tilting table 1 on which a material W as a workpiece is vertically mounted, and the worm wheel and worm engagement drive mechanism are omitted. This tilting table is used, for example, by fixing its fixed base 2 on the bed of a machine tool and setting the material W clamped on the upper surface of the tilting table 1 to a desired tilt angle position. A pair of support frames 3 are provided on the upper surface of the fixed base 2 and have a bearing device that supports the tilting table 1 by sandwiching the tilting table 1 back and forth.
has been erected. A trunnion support shaft 4 protruding from both sides of the tilting table is rotatably mounted on the bearing device of the support frame 3. Further, on the left side of the fixed base 2, there is provided a support shaft bracket 6 which rotatably supports a hydraulic cylinder 7 belonging to a worm shaft thrust compensation system which will be described later. The outer end of the actuating piston rod 10 inserted into the hydraulic actuating cylinder 7 is rotatably connected to a connecting bracket 9 provided at the lower end of the tilting table 1 via a pin shaft 8. FIG. 2 is a cross-sectional view of a plane perpendicular to the center axis 5 of the tilting rotation, and shows the operation rotation transmission system of the worm 12 meshing with the fan-shaped worm wheel 11 omitted in FIG. The worm foil 11 is integrally fixed along one side of the lower side of the tilting table 1 shown in FIG. 1 with bolts or the like.
A transmission gear 14 for worm rotation operation is fixed to the shaft end of the left worm shaft 13 of the worm 12 meshing with the worm wheel 11, and a transmission gear 14 fixed to the output shaft of a drive motor 16 for tilt rotation operation is attached to the gear 14. Gears 15 mesh with each other. The drive motor 16 can be replaced by a manually operable crank handle if desired. Reference numeral 17 denotes a bearing sleeve for bearing the left worm shaft 13 fixed to the fixed base 2 by bolts 19, and a roller bearing 18 is installed therein to rotatably support the left worm shaft 13. As shown in the figure, the right worm shaft integrally formed with the worm 12 consists of a large diameter shaft portion 20, a small diameter thrust bearing portion 20 ₁ , a fixed thread portion 20 ₂ , and a right end seal shaft portion 20 ₃ having the smallest diameter. The right wall shaft portion forms a stepped worm shaft portion whose diameter becomes smaller toward the right end. Reference numeral 21 denotes a bearing support holder for the right worm shaft 20, and the support holder 21 is formed into a hollow and elongated sleeve-like cylindrical body with a flange, and is inserted into a through opening 22 bored in a predetermined housing on the fixed base 2. It is loosely fitted. The right end flange 23 of the support holder 21 is fixed to the side surface of the housing by bolts 24, while the support holder 2
The inner end 25 of 1 is freely extending. Further, an annular groove 26 is formed in the outer circumferential portion of the holder cylindrical portion of the support holder 21 near the flange 23, and the bottom of this groove constitutes a weakened cylindrical portion that is thin and easily expandable and contractable. A pressure detection element 27, for example, a strain gauge, is attached to the bottom of the annular groove 26, that is, the outer circumferential surface of the weakened cylindrical portion, and the electrical output signal detected by the pressure detection element 27 is transmitted through a leader line 48 to generate a thrust, which will be described later. It is designed to be derived to a comparison circuit.

Further, an inwardly protruding step portion ₂₅₁ is formed on the inner circumferential surface near the inner end 25 of the support holder 21, and a pair of angular bearings 31 are provided on the front and rear sides of the step portion 251.
31 is installed inside to transmit the lateral axial thrust acting on the worm 12 to the weakened cylindrical part of the support holder 21 via the stepped part ₂₅₁ , and detect the axial thrust by the detection element 27 attached to this part. It's easy. 32 is an outer ring fixing nut of the angular bearing 31, and 33 and 34 are dustproof seals.

Figure 3 shows the entire configuration arrangement for reducing and compensating the axial thrust generated on the worm meshing tooth surface to a constant value regardless of table load fluctuations when setting the tilting table 1 to a desired tilt angle. Shown as a diagram. This block diagram serves to summarize and understand the concept of the invention. In FIG. 3, the solid line missing system shown in the top row, that is, the electric motor 16→
The motion transmission system of worm 12→worm wheel 11→tilt table rotating shaft 5 (◎)→tilt table 1 represents a mechanical motion transmission system, which corresponds to a known tilt table drive transmission system. In the present invention, the worm shaft thrust transmitted through the right worm shaft portion of the worm 12 is detected by the load detection element 27 described above, and its detection output signal is led as an input signal to the comparator 28. On the other hand, from the thrust threshold output signal generator 29, a threshold output signal corresponding to the minimum selected thrust required in advance on the worm engagement surface is led to the comparator 28 and compared. The threshold output signal can be set in advance by known adjustment circuit means, such as a potentiometer, so that a reference output signal corresponding to the desired minimum thrust to be produced on the worm tooth flank can be output.
Then, an output signal corresponding to the difference between the threshold value output signal generated from the comparator 28 and the output signal of the load detection element 27 is amplified by the amplifier 28' and causes the electric servo motor 40 to rotate. The electrical control circuit from the load detection element 27 to the servo motor 30 is shown as a dotted line with an arrow in the drawing.

Next, the output rotating shaft of the servo motor 40 is connected to a hydraulically operated cylinder 7 linked to the tilting table 1 by controlling and adjusting remote control valves 60, 60' which form part of a hydraulic pressure control valve circuit 50, which will be described in detail later. The hydraulic cylinder 7 is operated to reduce and compensate for the axial thrust generated above the reference thrust value mentioned above, and the worm tooth is adjusted based on the load fluctuation of the tilting table 1. The contact pressure is controlled to be always maintained within a pre-selected threshold value, and the operation input applied to the left worm shaft 13 during the tilting and rotation operation of the tilting table 1 is controlled to be a low driving force and constant rotational torque, and the tilting This aims to improve the accuracy of corner indexing. The double arrow system in the bottom row of FIG. 3 indicates the hydraulic circuit system.

Figure 4 shows how to generate a table rotation moment to compensate for load fluctuations on the tilting table 1.
A hydraulic pressure control valve circuit 50 is shown for automatically regulating the oil pressure values in both chambers of the hydraulically actuated cylinder 7. The circuit 50 includes a pair of balancing relief valves 51 for supplying and discharging pressure oil to both the left and right chambers of the hydraulic cylinder 7, that is, the expansion chamber side and the retraction chamber side, each time controlled according to the table load. 5
1'. the balancing relief valve 51;
The primary oil pressure _P1 on the inflow side of 51' is checked by the check valves 52, 5.
2' from the hydraulic source P through the common oil passage 53. The pilot ports formed inside the pair of balancing relief valves 51, 51' are connected to the pair of remote control valves 60, 60' via pilot control oil passages 61, 61', and the pilot oil pressure P ₂ , P ₂ ′ is adjusted as follows. That is, the output shaft of the electric servo motor 40, which receives a rotation control action in response to the difference between the detected worm shaft thrust and the reference thrust value, is connected to each poppet valve provided in each remote control valve 60, 60'. The pilot oil passages 61, 61' are adjusted by adjusting the pressures of the opening adjustment springs so as to be opposite to each other.
Also, pilot oil pressures P ₂ and P ₂ ' are set, which are adjusted by increasing and decreasing reciprocally. The pilot oil pressures P ₂ , P ₂ ′ set in this way are guided into the balancing relief valves 51 and 51 ′ through the pilot oil passages 61 , 61 ′, and the adjusted pilot oil pressures P ₂ , P ₂ ′ The secondary oil pressures P ₃ and P ₃ ' flowing out or being discharged through the pair of balancing relief valves 51 and 51' are regulated and supplied to the left and right chambers of the hydraulic cylinder 7 through the supply oil passages 55 and 55'. introduced or discharged. That is, the pressure in each chamber of the hydraulic cylinder 7 is controlled by the balancing relief valves 51 and 51' to the secondary oil pressure P ₃ ,
It becomes P ₃ ′. Therefore, the piston rod 10 moves due to the differential pressure, but at that time, the pressure oil in the chamber on the retraction side is returned to the tank T via the balancing relief valve, and the chamber on the expansion side has a balancing relief valve. Pressure oil flows in from the hydraulic source P via the secondary pressure, so the secondary pressure is kept constant. Furthermore, 54
and 62 indicate respective return oil passages connected to the excess pressure oil return tank T and drain tank Dr in each valve unit.

FIG. 5 is an illustrative explanatory diagram of the entire system in which the configurations of the various parts described above are linked. For convenience, the left worm shaft 13 corresponding to the rotation operation side is rotated by a manually operated crank handle 16. , and the processed material W is omitted from the illustration. Now, when the tilting table 1 is rotated and tilted around the central axis of the trunnion shaft 4-4 by rotating the crank handle 16', the worm wheel 11 and the worm 12 are rotated.
A contact force corresponding to the table load is generated between the meshing tooth surfaces and an axial thrust is generated on the right worm shaft 20. This axial thrust is detected by the load detection element 27, and this detection output signal is input to the comparator 28. In the comparator 28, this input detection output signal is compared with a threshold input signal derived from the threshold output signal generator 29 corresponding to a small reference worm shaft thrust selected in advance, and a comparison signal corresponding to the difference amount is compared. A comparator output signal is derived from comparator 28. This comparator output signal is input to an electric servo motor 40 via an amplifier 28'. The output shaft 41 of the servo motor 40 rotates in a required rotational direction in response to the difference signal, and rotates until the comparator output signal becomes zero. G is an interlocking gear train 42, 43, 43' connected to the output shaft 41 of the servo motor 40.
The gear 43 and the gear 43' rotate in opposite directions.
Therefore, the poppet valve opening spring pressures incorporated in the remote control valves 60 and 60' are regulated reciprocally, ie, one is regulated stronger and the other weaker, and the corresponding variable pilot oil pressures P ₂ , P ₂ ' are also regulated. If one is set to a large value, the other is adjusted to a small value. For this purpose, the hydraulically actuated cylinder 7 is connected to the balancing relief valves 51, 51' which are controlled by the different variable pilot oil pressures _P2 , _P2' .
The left and right ventricles of the body have different secondary hydraulic pressures.
P ₃ and P ₃ ' are introduced, and a compensating rotational moment is applied to the tilting table 1 with a drive output corresponding to the differential pressure of the working oil pressure, and the contact pressure of the worm meshing surface is always maintained within a selected threshold value. You can force it.

In FIG. 6, for a tilting table 1 on which a workpiece W is mounted in an arbitrary state, the tilt angle α is set to 0 degrees when the table surface is aligned with the horizontal plane, and the table tilt is adjusted by rotating the worm shaft. The change curve of the worm shaft thrust that occurs when the angle α is gradually increased is shown by a curve Q including points U, K, and V. For example, in Fig. 5, when the table surface is in a horizontal position, that is, the inclination angle α = 0, and the center of gravity of the entire table including the tower weight is unevenly distributed to the right of the table rotation center axis, the rotational moment generated by the table is indicated by the arrow The worm shaft thrust is generated around B in the direction of leftward arrow D. Curve Q therefore initially lies at point U below the ordinate axis Y. Next, as the inclination angle α is gradually increased, the leftward thrust value decreases, and at a certain inclination angle K, the rotational moment of the table becomes zero, so the axial thrust also becomes zero. At this time, the center of gravity of the load passes through the central axis 5. As the inclination angle of the table increases past the inclination angle K, the rotational moment acting on the table rotation axis is generated around arrow A, so the axial thrust changes to the right in the direction of arrow C. From then on, as the inclination angle α increases, the rightward axial thrust increases. V
increases towards. A curve Q' shown in the figure is a curve symmetrical to the curve Q with respect to the abscissa axis X. Therefore, this Q' curve is a theoretical curve that completely balances out the axial thrust generated along the curve Q when operating the tilting table. Theoretically, it is also conceivable to set the table drive output from the hydraulically actuated cylinder to generate a drive shaft thrust in the opposite direction along the Q' curve with respect to the worm tooth surface. However, in the present invention, a small threshold thrust ΔT is selected in advance in consideration of the actual table tilting operation, and is determined so that the contact pressure generated on the worm tooth surface is always maintained within a constant threshold ΔT. That is, the illustrated T curve corresponds to a practically designed critical thrust curve obtained by adding a constant threshold thrust ΔT to the Q' curve. Therefore, the critical worm shaft thrust value controlled by the drive output of the hydraulically actuated cylinder is always controlled along the above-mentioned T curve, and the thrust value lies within the limits of the threshold value ΔT.

As described in detail in the above embodiments, according to the present invention, even if the table load fluctuates, the contact force between the worm wheel and the worm is always maintained at a constant value, improving the accuracy of setting the inclination angle. Since the contact force can be set extremely low, the drive output is also small and the drive means can be made lighter and smaller.
It is possible to design the tilting table device regardless of its size. In addition, since the operation of the tilting table is based on the engagement of a mechanical worm and worm wheel, even if a failure occurs in the hydraulic control system or electrical control system, the operation of the tilting table will be prevented in conjunction with the table clamping device and other incidental equipment. Table operations can be carried out safely.

In addition, when compared with a conventional tilting table device, the accuracy of the conventional table tilting angle has a cumulative error of 10%.
The angle error used to be on the order of minutes, but the present invention was able to improve this to about two minutes.

[Brief explanation of drawings]

Fig. 1 shows a side elevational view of the tilting table device, with the worm wheel and worm engagement drive mechanism parts removed, and Fig. 2 shows a cross section in a plane perpendicular to the table rotation center axis in Fig. 1. This is an elevation view with the tilting table removed. Figure 3 is a block diagram of the compensation control circuit that maintains the worm shaft thrust at a constant value, Figure 4 is the hydraulic circuit of the hydraulic pressure control valve, and Figure 5 is the tilting table. FIG. 6 is a diagram showing the principle of compensating the worm shaft thrust. 1... Inclined table, W... Processing material, 2...
Fixed base, 3... Support frame, 7... Hydraulic actuation cylinder, 11... Worm foil, 12...
Worm, 13, 20... Left and right worm shafts, 16... Worm shaft drive motor, 21...
...Support holder, 27...Load detection element, 28...
Comparator, 40... Servo motor, 50... Hydraulic pressure control valve circuit, 51, 51'... Balancing relief valve, 60, 60'... Remote control valve, P
...Hydraulic power source, T, Dr...Excess oil return tank.

Claims (1)

[Scope of Claims] 1. A tilting table is rotatably supported on a fixed base, a worm wheel is integrally formed on the lower surface of the tilting table, and a rotating operation shaft of a worm that meshes with the worm wheel is fixed as described above. In a tilting table that is mounted on a bearing device provided on a base to set a tilting table angle, detecting a worm shaft thrust generated in response to a table load rotation moment acting around the rotation axis of the tilting table 1. a load detection element 27 that rotates the tilting table; and a hydraulic cylinder 7 that rotates the tilting table.
a threshold output signal generator 29 that generates an output signal corresponding to a preselected worm reference thrust; a comparator 28 that compares the threshold output signal with the detection output signal of the load detection element; and from the comparator. It consists of an amplification device 28' that amplifies the output signal of the comparative difference amount to be generated, and a hydraulic pressure control device that changes the supply pressure to the hydraulically operated cylinder 7 in response to the output signal of the amplification device. A driving force compensation control device for a tilting table, characterized in that a pressure control device is provided to change the supply pressure to the hydraulic cylinder in a direction that reduces the output signal of the amplifier. 2. The hydraulic pressure control device connects the hydraulic pressure source P and the return tank T to both chambers of the hydraulic cylinder through balancing relief valves 51 and 51', respectively.
a pilot hydraulic control circuit including a remote control valve 60, 60' connected to each pilot port of the balancing relief valve; a servo motor 40 and a remote control valve 6 that controls the rotation of the servo motor;
0 and 60', and is adjusted and controlled so that each pilot pressure P ₂ and P ₂ ' increases and decreases in opposite directions by the rotation of the servo motor. A driving force compensation control device for a tilting table according to claim 1.