Slide drive apparatus and slide drive method for pressing machine

A slide drive apparatus and a slide drive method for a pressing machine capable of enhancing positioning precision at the time of adjustment of die height, and responding to pressing work at high stroke per minute. For this purpose, the drive apparatus includes a slide (4), a servo motor (21) for controlling slide motion, a mechanical power transmission mechanism (3, 5, 6) for converting rotational power of the servo motor for controlling slide motion into reciprocating motion of the slide, and a servo motor (31) for adjusting die height, which performs die height adjustment of the slide by a position control.

TECHNICAL FIELD

The present invention relates to a slide drive apparatus and a slide drive method for a pressing machine.

BACKGROUND ART

Since a temperature difference occurs to a each component frame while a pressing machine is used, the die height is changed, and when high product precision is required, the change in die height has a large influence on the product precision. Recently, there are more and more products that require very high product precision, and this problem becomes important. For such a change in die height, a die height adjusting apparatus is conventionally proposed, and the one disclosed in, for example, Japanese Utility Model Application Publication No. 3-29036 is known.FIG. 7is a block diagram of a die height adjusting apparatus described in Japanese Utility Model Application Publication No. 3-29036.

InFIG. 7, a slide4is connected to a plunger19operated in a vertical direction via an adjusting screw41, and by rotating the adjusting screw41, the position of the slide4is made adjustable with respect to the plunger19. A worm wheel78is concentrically fixed to the adjusting screw41, and a worm79is meshed with the worm wheel78. Two ratchet wheels81and82, both having a number of claws, each of which is in an unequal-sided angled shape where one side of the claw is a catching surface, are fixed to a shaft of the worm79, with the catching surfaces of the claws on the respective ratchet wheels facing in the opposite direction to each other. The tip ends of piston rods85and86of cylinder devices83and84oppose the side of the catching surfaces of the claws of the respective ratchet wheels81and82in the extension direction of the piston rods85and86. Further, cylinder chambers of the cylinder devices83and84are connected to a fluid pressure source89such as a reservoir via solenoid valves87and88.

However, in the above-described die height adjusting apparatus disclosed in Japanese Utility Model Application Publication No. 3-29036, the ratchet wheels81and82are driven in normal and reverse rotation by the cylinder devices83and84to rotate the adjusting screw41via the worm79and the worm wheel78, and therefore, responsiveness is not so good. Consequently, the positioning precision, at the time of adjustment of the die height, cannot be made so high, thus making it very difficult to apply the apparatus to the products requiring high precision. In addition, the die height adjustment requires much time, and therefore this arises the disadvantage that the apparatus cannot respond to press working at high stroke per minute of, for example, 300 SPM or more, when the die height adjustment is performed for each press stroke, during slide operation, and at the time when working is not performed.

SUMMARY OF THE INVENTION

The present invention is made in view of the above-described disadvantage, and has its object to provide a slide drive apparatus and a slide drive method for a pressing machine capable of enhancing positioning precision at the time of adjustment of die height and responding to pressing work at high stroke per minute.

In order to attain the above-described object, a slide drive apparatus for a pressing machine according to the present invention has a constitution including a slide, a servo motor for controlling slide motion, a mechanical power transmission mechanism for converting rotational power of the servo motor for controlling slide motion into reciprocating motion of the slide, and a servo motor for adjusting die height, which performs die height adjustment of the slide by a position control.

According to the above constitution, since the die height adjustment is performed by a position control of the servo motor, responsiveness of control becomes very good, die height adjustment can be performed with very high precision, and the product precision can be enhanced dramatically. Since the die height adjustment is completed in a short time, the apparatus can easily respond to a slide operation at high stroke per minute.

Further, in the slide drive apparatus for the pressing machine, the die height adjustment of the slide may be performed during a slide motion control of the servo motor for controlling slide motion. According to the above constitution, the die height adjustment is performed by the position control of the servo motor during a slide motion control, and therefore the die height adjustment can be performed at high precision, thus making it possible to enhance product precision dramatically and easily respond to a slide operation at high stroke per minute. Further, the die height adjustment is performed during a slide motion control, and thus a high speed operation at high stroke per minute of, for example, 300 SPM or higher, which has been conventionally difficult to respond to, can be easily performed.

Further, in the slide drive apparatus for the pressing machine, the die height adjustment of the slide may be performed for each slide stroke. According to the above constitution, die height adjustment is performed for each slide stroke, and therefore pressing work can be always performed in a state in which the die height is kept highly precise, thus making it possible to surely produce the product with high precision without variations.

Further, in the slide drive apparatus for the pressing machine, the power transmission mechanism may comprise a link mechanism. According to the above constitution, a servo motor rotational power is converted into slide reciprocating motion via the link mechanism, and therefore it is not necessary to receive large load directly with the servo motor, in addition to the fact that large pressurization force can be easily obtained with comparatively small torque. In addition, link motion suitable for molding work and cutting work can be easily realized. Further, the slide can be continuously operated by the continuous rotation of the servo motor in one direction, and therefore the drive control of the servo motor during continuous operation is easy.

Furthermore, in the slide drive apparatus for the pressing machine, the power transmission mechanism may comprise an eccentric mechanism. According to the above constitution, the rotational power of the servo motor is converted into slide reciprocating motion via the eccentric mechanism, and therefore it is not necessary to receive large load directly with the servo motor, and the conversion mechanism can be made simple.

Further, in the slide drive apparatus for the pressing machine, the power transmission mechanism may comprise a ball screw mechanism. According to the constitution, the rotating power of the servo motor is converted into the reciprocating motion of the slide via the ball screw mechanism, and therefore it is not necessary to receive large load directly with the servo motor, and the conversion mechanism can be made simple.

A slide drive method for a pressing machine according to the present invention has the constitution including the step of performing a position control of a servo motor for adjusting die height during driving of the slide to perform die height adjustment of the slide.

According to the above constitution, since the die height adjustment is performed by the position control of the servo motor during driving of the slide, the die height adjustment can be performed with very high precision, and the product precision can be enhanced dramatically. Further, even when the slide drive source is not a servo motor, but, for example, a DC motor, an AC motor or the like, if the position control of the servo motor for adjusting the die height is performed by receiving a signal of the slide position sensor and the like, the die height adjustment can be performed during driving of the slide. Further, if the slide motion control is performed with the servo motor, the die height adjustment is performed during slide motion control by being linked with the servo motor for the slide motion control, thus making it possible to easily respond to the slide operation with higher stroke per minute, and perform a high-speed operation of the pressing machine.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments according to the present invention will be explained in detail below with reference to the drawings.

A first embodiment will be explained based on FIG.1.FIG. 1is a schematic block diagram of this embodiment. InFIG. 1, a slide4and a plunger19of a pressing machine1are both supported at a main body frame2to be vertically movable, and the slide4and the plunger19are fitted at a lower protruded portion19aof the plunger19to be vertically slidable. A thread portion of an adjusting screw41provided at the slide4is screwed into a female screw portion formed in a lower part of the plunger19. An upper part of the plunger19is connected to the main body frame2via a link mechanism3. Namely, one end of a first link11is rotatably connected to an upper part of the main body frame2with a pin14, the other end thereof is connected to one end of both end portions of one side of a triangle link12. The other end of the both end portions of the aforementioned one side of the triangle link12is connected to one end of a second link13with a pin16, and the other end of the second link13is connected to the upper part of the plunger19with a pin18. The first link11, the triangle link12and the second link13constitute a link mechanism3.

A first pulley22is attached to an output shaft of a servo motor21for driving the slide (motion control). A timing belt22ais placed across a second pulley23rotatably supported at the main body frame2and the first pulley22. A first gear24is attached on the same axis as the second pulley23, and a second gear25meshed with the first gear24is rotatably supported at the main body frame2. A pin17on the other end, which opposes one side between the pins15and16of the triangle link12are rotatably connected to an eccentric position of the second gear25. By controlling the rotation of the servo motor21, an angle of rotation of the second gear25is controlled to reciprocate the plunger19and the slide4in the vertical direction via the link mechanism3such as the triangle link12and the like.

A gear42is attached at a lower end portion of the adjusting screw41provided at the slide4, and the gear42is meshed with a pinion44attached to an output shaft of a servo motor31for adjusting die height, which is attached to the slide4. Control command signals are inputted into the servo motor21for driving the slide (motion control) and the servo motor31for adjusting the die height, from a controller30. Position detecting signals θ1and θ2of position sensors27and32, which are provided at both the servo motors21and31, are inputted into the controller30. A load sensor33constituted by a strain sensor or the like is attached to the slide4, and a load detection signal P of the load sensor33is inputted into the controller30.

The controller30is constituted by a high-speed operation unit such as a microcomputer, a high-speed numeric operation processor, and has memory for storing predetermined control parameters, control target data and the like. For example, set means (not shown) for previously setting slide positions and slide speed in one cycle as a slide control pattern according to the types of machining for a work, work machining conditions and the like is included, the set slide control pattern is stored in the aforementioned memory. Here, as the types of machining for the work, there are molding, drawing, punching, marking and the like, and as the work machining conditions, there are plate thickness, molding shape, slide SPM and the like. Before a work is actually machined under the above-described set condition, precision of the product, which is previously machined by trial pressing, is measured, then a target load corresponding to a die height amount which makes optimal precision is obtained, and the target load is stored in the aforementioned memory.

Next, an operation at the time of driving the slide4via the link mechanism3will be explained.

When the servo motor21is rotated in the direction of the arrow21ashown in the drawing, the speed is reduced via the pulleys22and23and the gears24and25, and the pin17of the triangle link12is rotated in the direction of the arrow25a. When the pin17is at a position17a(corresponding to the triangle link12shown by the two-dot chain line), the position of the pin18at the upper part of the plunger19is set at a position18acorresponding to a top dead center of the slide4. When the pin17is at the position17b(corresponding to the triangle link12shown by the solid line), the position of the pin18is set at a position18bcorresponding to a bottom dead center of the slide4. Following the above-described rotation of the pin17, the pin18reciprocates between the position18aand the position18b, whereby the plunger19and the slide4can reciprocate between the bottom dead center position and the top dead center position. By continuously rotating the servo motor21in the same direction, the slide4can be continuously operated.

At the time of actual machining, the rotation angle and the speed of the servo motor is controlled by the controller30based on a previously set control pattern, whereby a slide motion corresponding to the pattern is realized. The slide motion is shown in, for example, FIG.2. Here, inFIG. 2, a horizontal axis represents a crank angle in the control, a time axis of one cycle of the slide motion is shown by being brought into correspondence with 0 degree to 360 degrees of the crank angle in the conventional mechanical link press. A vertical axis represents a slide stroke (moving distance).

The controller30brings the horizontal axis of the slide motion to be controlled into correspondence with one cycle time corresponding to the slide SPM, and a slide stroke position corresponding to each point of the time axis in a uniform speed operation of the slide is obtained based on the above-described slide motion. Further, the controller30sets a motor rotation angle, which realizes the obtained slide stroke position, as a target position. Then, the controller30arithmetically operates a control command value, so that a deviation value between the target position and the position detection signal θ1from the position sensor27becomes small, and the controller30controls the rotation angle of the servo motor21according to this control command value. Such a control is repeated for each cycle of the slide motion in succession, whereby motion is realized.

Meanwhile, when the servo motor31for adjusting the die height is rotated, the adjusting screw41is rotated via the pinion44, and gears43and42, and the slide4vertically moves, whereby the die height is adjusted. The adjustment of the die height is performed, following the procedure as shown in a flowchart inFIG. 3, for example.

InFIG. 3, in step S1, the slide4is controlled up to the bottom dead center by the servo motor21based on a slide motion previously set. In step2, a load value at the time of pressurization is inputted from the load sensor33, and a maximum load value Pmax at the slide stroke is obtained. Next, in step S3, it is checked whether or not the maximum load value Pmax is larger than a target load value P0previously stored, and when it is larger, a command is given to proceed to step S5. In step S5, after the slide passes the bottom dead center, the slide4is controlled up to the top dead center by the servo motor21based on the aforementioned slide motion, and the die height is moved upward by a predetermined amount ΔH by the servo motor31. Thereafter, a command is given to return to step S1to repeat the above process.

When the maximum load value Pmax is the aforementioned target load value P0or less in step S3, it is determined whether the maximum load value Pmax is smaller than the target load value P0in step S4, and when it is smaller than the target load value P0, a command is give to proceed to step S6. In step S6, after the slide passes the bottom dead center, the slide4is controlled to move to the top dead center based on the aforementioned slide motion by the servo motor21, and the die height is moved downward by the predetermined amount ΔH by the servo motor31. Thereafter, the command is given to return to step S1to repeat the above process. When the maximum load value Pmax is not smaller than the target load value P0in step S4, namely, when both of them are equal, a command is given to proceed to step S7, and after the slide passes the bottom dead center, the slide4is controlled to move to the top dead center by the servo motor21based on the aforementioned slide motion, then a command is given to return to step S1to repeat the above process.

According to the constitution and operation of the first embodiment as described above, the following effects are provided.

(1) Since a very small movement of the slide4for adjustment of the die height is controlled by the servo motor31, the control responsiveness is very good, and thus positioning of a predetermined very small moving amount of the slide (1 μm to 5 μm) can be completed with high precision. Accordingly, the die height can be adjusted with high precision, and therefore product precision can be kept high.

(2) Since die height adjustment is performed by controlling the servo motor as in the above-described item (1), adjustment can be completed in a short time with excellent responsiveness, adjustment can be performed for each slide stroke even when the slide is driven at high stroke per minute (high speed SPM). Accordingly, the die height can be always adjusted to an optimal die height position, and highly precise products can be produced with stability without variations.

(3) In addition, during driving of the slide, namely, during the movement after passing the bottom dead center to a work contact position via the top dead center, the die height adjustment by the servo motor31is completed in a short time, and therefore the apparatus can also respond to machining at high stroke per minute. As a result, there is no inconvenience in operation and availability is extremely enhanced as compared with the apparatus, which performs die height adjustment while the slide stops.

(4) The die height is adjusted so that the load becomes the optimal load according to the work by monitoring the load value, and therefore the apparatus can be constructed at lower cost as compared with the apparatus which controls the die height by directly measuring it with a highly precise linear sensor or the like.

Next, a second embodiment will be explained based on FIG.4.FIG. 4is a schematic block diagram of a press drive apparatus of this embodiment, and the same components as inFIG. 1are given the same reference numerals and symbols inFIG. 4, and the explanation will be omitted below. A pinion51attached to an output shaft of a servo motor21for driving a slide is meshed with a gear52, and a nut member54is fixedly provided at an axis of the gear52, the nut member54is rotatably supported at a main body frame2. A ball screw53is screwed into the nut member54to be movable in the axial direction. A tip end portion of the ball screw53is caught by a long hole55longer in a perpendicular direction to the axis of the ball screw and an catching pin56, which are formed at a triangle link12of a link mechanism3, to be vertically slidable to be connected thereto.

Next, an operation of this embodiment will be explained with reference to FIG.4. When the servo motor21is rotated, the nut member54is rotated via the gears51and52. As a result, the ball screw53advances and retreats in the axial direction to push and pull the triangle link12to drive it in the arrow direction. The ball screw53is driven to reciprocate so that the triangle link12moves between a position12acorresponding to a first top dead center of the slide4and a position12ccorresponding to a second top dead center via a position12bcorresponding to a bottom dead center. At this time, a moving amount in the vertical direction of the triangle link12is absorbed by the catching pin56vertically sliding inside the long hole55. As a result, as in the case of the first embodiment, the plunger19and the slide4reciprocate between the top dead center and the bottom dead center via the pin18connected to the upper part of the plunger19. Further, it is the same as in the first embodiment that the die height adjustment is performed by the servo motor31.

The effects of the second embodiment is substantially the same as the first embodiment, but other than this, the second embodiment has the unique effects as follows.

(1) The ball screw53is driven to reciprocate in a horizontal direction to reciprocate the triangle link12between the two positions12aand12cthat correspond to the top dead center with the position12bcorresponding to the bottom dead center between them, and therefore it is made possible to pass the bottom dead center twice by reciprocating drive of one cycle by the servo motor21. As a result, twice as many as strokes per minute of the slide4with respect to the number of drive cycles of the servo motor21can be realized, and thus slide drive at high stroke per minute can be facilitated.

(2) Twice as many as strokes per minute can be realized as described above, thus making it possible to obtain the effect that it is effective because clear marking can be performed by double pressing in the case of, for example, coining work, and the like.

Next, a third embodiment will be explained base on FIG.5. The same components as inFIG. 1are given the same numerals and symbols, and the explanation thereof will be omitted here. A pinion51attached to an output shaft of a servo motor21is meshed with a gear52, a ball screw53ais attached at an axis of the gear52, and a ball screw53ais rotatably supported at a main body frame2. A nut member54ais screwed onto a ball screw53ato be movable in an axial direction. An upper part of a link66is swingably connected to the nut member54awith a pin, and an upper part of a plunger19is connected to a lower part of the link66with a pin18. The ball screw53a, the nut member54aand the link66constitute a ball screw mechanism5.

Here, an operation of the third embodiment will be explained. When the servo motor21is rotated, the ball screw53ais rotated, and following this, the nut member54ais moved in the axial direction (the horizontal direction in this example). The movement of the nut member54ais converted into vertical movement by the link66to drive the plunger19and the slide4vertically. When the ball screw53ais normally and reversibly rotated in a range of a predetermined rotational frequency, the nut member54areciprocates between predetermined positions54band54c, and the plunger19and the slide4vertically moves via the link66. When the predetermined positions54band54care set at the positions corresponding to two top dead centers as in the first and the second embodiments, the slide4vertically moves two strokes and passes the bottom dead centers twice for one cycle of reciprocation of the nut member54a. It is the same as in the aforementioned embodiments that the servo motor31for adjusting the die height and the adjusting screw41are included.

The effects according to the third embodiment are the same as the second embodiment, and therefore the explanation will be omitted. In the second and the third embodiments, the slide4vertically moves two strokes for one cycle of reciprocation of the triangle link12or the nut member54a, but this is not restrictive. For example, the triangle link12or the nut member54amay be reciprocated between the position corresponding to the top dead center of the slide and the position corresponding to the bottom dead center, so that the slide4may vertically move one stroke for one cycle of reciprocation.

Next, a fourth embodiment will be explained based on FIG.6. InFIG. 6, a first pinion61, which is attached to an output shaft of a servo motor21for driving a slide, is meshed with a first gear62, and a second pinion63having the same axis is fixedly provided at a position of the axis of the first gear62. A second gear64is meshed with the second pinion63, and an upper part of a link66is swingably connected to the second gear64at an eccentric position with a pin65. An upper part of the plunger19is connected to a lower part of the link66with a pin18. As in the first embodiment, an adjusting screw41is screwed into the plunger19, and a pinion44, which is attached to an output shaft of a servo motor31for adjusting die height attached to the slide4, is meshed with a gear42of the adjusting screw41via an intermediate gear43. The gear64, the pin65and the link66constitute an eccentric mechanism6.

An operation of the fourth embodiment will be explained with reference to FIG.6. When the servo motor21is rotated, the second gear64is rotated via the second pinion63, and the link66, which is eccentrically connected to the second gear64with the pin, and the plunger19, which is connected to the link66, reciprocate in the vertical direction, whereby the slide4reciprocates in the vertical direction. In this situation, by the continuous rotation in one direction of the servo motor21, the slide4continuously reciprocates. It is the same as in the previous embodiments that the die height is adjusted via the adjusting screw41by the rotation of the servo motor31. The effects according to the fourth embodiment is the same as the first embodiment, and therefore the explanation will be omitted.

As explained thus far, according to the present invention, the following effects are provided.

(1) Since the die height adjustment is performed by the control of the position of the servo motor, control responsiveness is very good, and the die height adjustment with high precision can be completed in a short time. Accordingly, press working with high product precision can be made even during an operation at high stroke per minute.

(2) As a result that the die height adjustment is performed by the control of the position of the servo motor, the die height adjustment can be performed without reducing stroke per minute even if the die height adjustment is performed during a slide motion control, for the reason of the above-described item (1). As a result, a pressing operation can be made at high stroke per minute, and excellent productivity is obtained. The control of the die height adjustment by the servo motor is linked with the slide motion control by the servo motor, and thus the control can be facilitated.

(3) Since the die height adjustment with the servo motor is performed for each slide stroke, pressing work can be always performed in a state in which the die height is kept highly precise, and thus the products with high precision can be surely produced without variations.