JP4053546B2 - Air balance device - Google Patents

Description

  The present invention relates to an air balance device applied to a mechanism that compensates the weight of a movable part that moves on a vertical axis in, for example, a precision measuring instrument, a precision machine tool, and a precision processing machine. It is related with the air balance apparatus which improved the adjustment method of the balance force for this.

Many measuring instruments, machine tools, processing machines, and the like that require precise movements have movable parts that move vertically on a vertical axis. Unlike the case of moving on the horizontal axis, a moving part that moves on the vertical axis (hereinafter also referred to as “vertical moving part”) usually requires a mechanism that compensates for gravity due to its own weight. is there. Generally used as such a mechanism is to compensate for the gravitational component by a counter balance method or an air balance method.
Of both types, the counter balance method has the disadvantage that it is necessary to mount the same weight as the movable part as the counter balancer, so that the apparatus cannot be reduced in size and an increase in weight equivalent to the movable part cannot be avoided. . Further, in order to adjust the balance force, it is necessary to adjust the weight itself, which is not suitable when the weight of the movable part changes.

On the other hand, the air balance type self-weight compensation mechanism does not perform the compensation by mounting the gravitational force applied to the movable part with an equivalent heavy object, and therefore it is relatively easy to adopt a compact structure. For example, if an air balance chamber using a piston having a diameter of 10 cm is prepared and a pressure of 5 kgf / cm ² is applied, a force of about 400 kgf can be obtained. Even if the weight of the movable part changes, the balance force can be easily adjusted by changing the air pressure.

  However, this air balance method also has one problem related to balance force adjustment. That is, when controlling the air balance force by controlling the pressure of the air flowing into the air balance chamber, it is an electropneumatic regulator that is generally used to electrically control the air pressure. Due to the operating principle of opening and closing the solenoid valve at high speed, it is inevitable that pressure pulsation occurs, and a precise and stable air balance force cannot be obtained.

  As one measure for solving this problem, it is known to employ a structure in which a large air tank is disposed between the electropneumatic regulator and the air balance chamber. 1 and 2 show an example in which the same structure is applied to a vertical drive shaft. FIG. 1 is an external view, and FIG. 2 is a cross-sectional view taken along a broken line AA in FIG.

  In FIG. 1, an air balance device generates a balance force in an air balance mechanism part (a vertical shaft structure part provided with an air balance mechanism) including a fixed part 10 and a movable part 20, and the air balance mechanism part 1. And a related configuration for controlling the balance force. The movable portion 20 has a rectangular container shape with an opening, is directed to the opening downward, the fixed portion 10 is inserted therefrom, and a vertical axis linear drive mechanism (not shown) The fixed portion 10 is supported so as to be linearly movable in the vertical direction (gravity direction).

  As shown in FIG. 2, the air balance chamber 14 is formed in a region excluding the region occupied by the insertion portion of the fixed portion 10 in the internal space region of the movable portion 20, and the pressurization sent to the air balance chamber 14. The weight load applied to the movable part 20 is reduced by the action of air.

  Inside the fixed part 10, a flow path 12 is provided that extends from an opening 11 located on the side near the lower end of the fixed part 10 to an opening 13 located at the top of the fixed part 10 (the bottom of the air balance chamber 14). It has been. The opening 11 is connected to a pressurized air supply system including an air compressor (not shown), a piping 31, a pressure control device 30, a piping 32, an air tank 33, and a piping 34. From this pressurized air supply system, it flows into the air balance chamber 14 through the opening 11, the flow path 12, and the opening 13, and the internal pressure generates a balance force that urges the movable part 20 upward.

  A bearing portion 15 is provided between the outer surface of the fixed portion 10 and the inner surface of the standing wall portion of the movable portion 20, although detailed illustration is omitted, and the movable portion 20 moves up and down smoothly relative to the fixed portion 10. It is possible to do. In addition, this bearing part 15 can also be comprised with the air bearing using the narrow clearance gap between the fixed part 10 and the movable part 20. FIG. In this case, this gap provides one outflow path for the pressurized air that has flowed into the air balance chamber 14 through the above path.

  An electropneumatic regulator is widely used as the pressure control device 30 and adjusts the pressure of high-pressure compressed air supplied from an air compressor or the like so as to obtain an optimum balance force. However, as described above, this electropneumatic regulator opens and closes the solenoid valve at a high speed to adjust the pressure, and thus causes pressure pulsation.

  The air tank 33 functions as a buffer that absorbs this pulsation, but a large volume is required for the air tank 33 in order to sufficiently perform the buffer function. As a result, in order to control the pressure of the air balance chamber 14, the air pressure corresponding to the volume of the large volume air tank 33 is also controlled, and the total volume of air to be pressure controlled is increased. It becomes difficult to control the air balance force at high speed. In other words, the response performance of the balance force control is low.

  There is a type of pressure control device 30 that electrically controls the valve opening / closing amount of a general manual regulator instead of an electropneumatic regulator with a servo motor. If a pressure control device of such a type is adopted, Since the pressure fluctuation is reduced, the air tank 33 becomes unnecessary. However, there is a problem that the response is poor when the pressure in the air balance chamber 14 is controlled to be rapidly lowered. That is, in the method of controlling the valve opening / closing amount, there is no other way than reducing the pressure of the supply air by letting air escape from the exhaust port of the regulator, and it is difficult to realize a pressure drop at high speed.

  Thus, in the prior art, control with good responsiveness is difficult regardless of whether a method using an air tank or a method using no air tank is employed as shown in FIGS. There is no known document that discloses the technology to be solved.

  As described above, in the prior art, when an electropneumatic regulator generally used as a pressure control device is adopted and the air balance force is controlled through the pressure control of the air flowing into the air balance chamber, It is difficult to prevent the pressure pulsation derived from the operation principle of the electropneumatic regulator, and a large capacity air tank is required to absorb the pulsation. Further, when a normal regulator is driven by a servo, the pressure change is sufficiently small, but it is difficult to control the pressure in the air balance chamber in the direction of reducing the pressure.

  Therefore, a basic object of the present invention is to provide an air balance device that can easily overcome such drawbacks of the prior art and easily control the balance force with high responsiveness.

  The present invention solves the above problem by introducing a method for controlling the flow rate of air exhausted from the air balance chamber while supplying air of a constant pressure to the air balance chamber.

  More specifically, the present invention is directed to the movable portion having a container shape having an opening portion with the opening portion facing downward and the movable portion being inserted into the internal space of the movable portion. An air balance that is provided so as to be linearly movable in the direction of gravity with respect to the fixed part, and that holds pressurized air in an area of the internal space area of the movable part excluding the area occupied by the insertion part of the fixed part. The present invention is applied to an air balance device of a linear drive device that constitutes a chamber.

The feature of the invention described in claim 1 that defines the basic requirements of the present invention is that the air balance device supplies a first flow of air pressurized to a constant pressure to the air balance chamber. Path means, second flow path means for exhausting the air in the air balance chamber, and flow rate control means for controlling the flow rate of exhaust gas that is performed through the second flow path means, and further, The flow path means has a first exhaust system and a second exhaust system which are separated from each other, and a constant flow rate of air is exhausted through the first exhaust system, while exhausted through the second exhaust system. The flow rate of the air is controlled by the flow rate control means, and adjustment is made to eliminate the pulsation of the air balance force by the air balance chamber through the flow rate control of the exhaust gas by the flow rate control means.

Here, the drive unit of the linear drive device is a motor, and the flow rate control unit is configured to reduce the load of the motor based on at least one index related to the control of the motor. Means for determining the flow rate may be provided (claim 2). A typical example of the index is a current value supplied to the motor. Usually, based on this current value, or a vertical axis position deviation, speed deviation, and the like are added to the exhaust flow rate calculation ( Claim 3 ).

  The exhaust flow rate can be controlled, for example, by providing a minute gap in the flow path and continuously changing it. According to such air flow rate control, pressure pulsation does not occur, and stable air balance force control can be performed. In addition, by controlling the flow rate of only a part of the exhaust gas, the resolution of the control can be improved, and even if the flow rate control device malfunctions, the vertical axis is prevented from suddenly dropping or rising. Will be able to.

  According to the present invention, it is possible to control the balance force with high speed and precision by controlling the displacement of the air balance chamber for the vertical axis of a measuring instrument or machine tool, and the motor used for driving the vertical axis can be controlled. It suppresses heat generation and enables high-speed and precise operation.

For convenience of explanation, one reference embodiment will be described before describing an embodiment of the present invention. FIG. 3 is a diagram illustrating a schematic configuration of an air balance device according to one reference embodiment, and FIG. 4 is a diagram illustrating an outline of a cross-sectional structure along line BB in FIG. 3. Air balancing device according to the present reference embodiment, FIG. 1, as in the conventional example shown in FIG. 2, are applied to the vertical driving rotary shaft structure. In FIG. 3, the air balance device generates a balance force in the air balance mechanism portion (vertical drive shaft structure portion provided with the air balance mechanism) 2 including the fixed portion 40 and the movable portion 50 and the air balance mechanism portion 2. And a related configuration for controlling the balance force. The movable part 50 has a rectangular container shape having an opening, the opening is directed downward, and the fixed part 40 is inserted therefrom. The movable unit 50 is supported so as to be linearly movable in the vertical direction (gravity direction) with respect to the fixed unit 40 by a vertical axis linear drive mechanism (not shown).

As shown in FIG. 4, the air balance chamber 44 is formed in a region excluding the region occupied by the insertion portion of the fixed portion 40 in the internal space region of the movable portion 50, and the pressurization sent to the air balance chamber 44. The weight load applied to the movable part 50 is reduced by the action (balance force) of air.
A major feature of the balance device 2 is that it is a flow path means (first flow path means) for sending air of constant pressure into the air balance chamber 44, and air is discharged (outflow) from the air balance chamber 44 while controlling the flow rate. ) Channel means (second channel means).

  The first flow path means includes a flow path 42 extending from an opening 41 located on the side near the lower end of the fixed portion 40 to an opening 43 positioned at the top of the fixed portion 40 (the bottom of the air balance chamber 44). Yes. The opening 41 is connected to a pressurized air supply system including an air compressor (not shown), a pipe 61, a pressure control device 60, and a pipe 62. The pressurized air is supplied from the pressurized air supply system to the opening 41, The air flows into the air balance chamber 44 through the flow path 42 and the opening 43, and the internal pressure generates a balance force that urges the movable portion 50 upward.

  Thus, the pressurized air supply system does not include the air tank 33 unlike the conventional example shown in FIGS. 1 and 2. Further, a pressure adjustment device 60 is employed instead of the pressure control device 30. The pressure adjusting device 60 is set not to variably control the air pressure in accordance with the control input (for example, the current value of the servo motor that drives the vertical axis) like the pressure control device 30 (adopted in the conventional example). It is a device that maintains a constant pressure. However, it is preferable that the set value itself of “constant pressure” is adjustable.

  As in the conventional example, a bearing 45 is provided between the outer side surface of the fixed portion 40 and the inner side surface of the standing wall portion of the movable portion 50, although illustration of details is omitted, and the movable portion 50 is fixed to the fixed portion. It is possible to move up and down smoothly with respect to 40. In addition, the bearing portion 45 can be configured by an air bearing that uses a narrow gap between the fixed portion 40 and the movable portion 50. In this case, this gap provides one outflow path for the pressurized air that has flowed into the air balance chamber 44 through the above path.

Then, the flow passage means a second flow path means for discharging (outlet) air from the air balance chamber 44 while controlling the flow rate, the top of the solid tough 40 (the bottom of the air balance chamber 44), open A flow path 46 extending from an opening 45 provided at a slight distance from the hole 43 to an air outlet 47 provided on a side near the lower end of the fixing portion 40 (however, at a position different from the opening 41). Is included.

  The air outlet 47 is connected to a pressurized air exhaust system including a pipe 71, a flow rate control device 70, and a pipe 72. The flow rate control device 70 is a device having a function of controlling the flow rate per unit time according to a control input (an example will be described later), and is known per se.

  Thus, in the air balance device 2, the compressed air enters the air balance chamber 44 at a constant pressure by the pressure adjusting device 60, and the exhaust amount from the air balance chamber 44 is controlled by the flow rate control device 70. Needless to say, if the amount of exhaust is increased by the flow rate control device 70 under the condition that air is sent to the air balance chamber 44 at a constant pressure, the pressure in the air balance chamber 44 decreases and the air balance force decreases. On the contrary, if the exhaust amount is decreased by the flow rate control device 70, the pressure in the air balance chamber 44 increases so as to approach the constant pressure, and the air balance force increases.

That is, by controlling the discharge flow rate by the flow rate control device 70, it is possible to control the pressure in the air balance chamber 44 in such a manner that the “constant pressure” set by the pressure adjustment device 60 is almost the upper limit. Appropriate air balance force can be controlled.
What should be noted here is that by controlling the air balance force through the flow rate control performed on the exhaust system side of the air balance chamber, there is no pressure pulsation as in the conventional example described above, and therefore The air tank (see FIGS. 1 and 2) is not necessary. In addition, since the increase or decrease in the discharge flow rate changes the pressure in the air balance chamber with high responsiveness, the speed of air balance force control can be increased compared to the conventional method in which pressure control is performed on the supply side.

That is, in the method of controlling the supply pressure of air as in the conventional example, even if the supply pressure is changed by the pressure control device 70, it takes time until the change is completely reflected in the pressure in the air balance chamber 14. There is a delay. This delay becomes more prominent as the volume of the air balance chamber 14 is larger and the volume of the air tank 33 is larger (a kind of impedance effect). On the other hand, when the flow rate is changed by a method of controlling the flow rate on the discharge side as in this reference embodiment, the pressure in the air balance chamber 44 is exhausted from a constant pressure set by the pressure adjusting device 60. Shift upwards or downwards according to the amount change. This shift occurs almost without time delay.
This is because the “continuous equation” is established for the flow from the air balance chamber 44 to the pipe 72 via the flow path 6, the pipe 71 and the flow rate control device 70, and there is a certain amount Δ change in the flow rate passing through the flow rate control device 70. Then, almost simultaneously, the air flow rate sucked into the opening 45 also changes by the same amount Δ, which is immediately reflected in the pressure in the air balance chamber 44.
Next, an example of how to take a control input to the flow control device 70 in the air balance device described above will be described with reference to FIG. 5 showing a related block configuration.
In FIG. 5, the air balance mechanism portion of the air balance device according to the reference embodiment described above is represented by an air balance chamber 44, and a motor 52 that drives the movable portion 50 on the vertical axis, and an attachment to the motor 52. A portion to which the position detector (pulse encoder) 53 is added is surrounded by a broken line and depicted as a vertical axis mechanism portion 51. While set to; (setting change can set pressure) is supplied to the air balance chamber 44, the compressed air to supply the air compressor 29, as previously described, the constant pressure by the pressure adjusting device 60 Exhaust gas whose flow rate is controlled is performed through an exhaust system including the flow rate control device 70. In the reference embodiment, the exhaust system is one system as described above. However, as described later, in the embodiment of the present invention, the exhaust system is divided into an exhaust system that performs constant flow exhaust and an exhaust system that controls the exhaust flow .

The motor 52 that drives the vertical axis is operated by the current supplied through the amplifier 82, and the current value is controlled by the motor control device 81. An arithmetic unit (CPU) indicated by reference numeral 80 performs calculations necessary for control. Further, the position detector 53 detects the position (rotational position or linear movement position) of the motor 52 and sends it to the motor control device 81. Using this, the motor control device 81 performs feedback control for controlling the position and speed of the vertical axis based on, for example, a machining program (in the case of a machine tool). Although the control method itself of such motors are well known, in this preferred embodiment, in parallel with such a motor controller, and controls the flow control device 70.

  That is, a motor current value (an example of an index related to motor control) is output from the motor control device 81, converted into a required flow rate value by the arithmetic device 80, and input to the flow rate control device 70. Thereby, even when a workpiece or jig having different weights is attached to the vertical axis, the air balance force can be automatically controlled to cancel the change in weight. In addition, representative examples of “index related to motor control” used for flow rate control are the above-mentioned “current value supplied to the motor”. By adding the above to the calculation of the exhaust flow rate, the dynamic load of the motor can be reduced more effectively, and the heat generation of the motor can be suppressed.

As an example of the flow rate conversion formula in which the position deviation Δz and the speed deviation Δv are added to the current value I, the following can be considered.
Flow rate (m ³ / sec) = aI + bΔz + cΔv (1)
However, a, b, and c are weighting coefficients. If b = c = 0, flow control is performed in consideration of only current.

In the reference embodiment described above, the exhaust system is one system, but as already mentioned, the present invention is provided with an exhaust system that performs constant flow exhaust and an exhaust system that controls the exhaust flow. A schematic configuration of an air balance device according to such an embodiment is shown in FIG. The configuration shown in FIG. 6 differs from the configuration shown in FIGS. 3 and 4 only in the exhaust system, and the structure and the like of the balance mechanism section (vertical drive shaft structure section provided with an air balance mechanism) 3 are the same. It is. That is, a branch pipe 73 that exhausts through the flow rate adjusting device 71 is provided in the pipe 71 connected to the air outlet 47. That is, the exhaust path from the air balance chamber 44 is divided into two systems, and the flow rate of the air passing through the flow rate adjusting device 71 is kept at a constant set value (the set value can be changed), while the flow rate control device 70. The flow rate of the air passing through is controlled in accordance with the control input, as in the above reference embodiment.

An example of a block configuration in such an embodiment is shown in FIG. The block configuration in FIG. 7 is different from the block configuration shown in FIG. 5 in that a flow rate adjusting device 71 is added and the exhaust system of the air balance chamber 44 is connected to a system that passes through the flow rate control device 70 and the flow rate adjusting device 71. It is divided into two hands of the system that passes through.

  The reason why such a configuration can be taken is that, in general, the control of the exhaust amount necessary to reduce the motor load is small. That is, if the exhaust from the air balance chamber 44 is separated into two systems, the rough exhaust amount is adjusted by the flow rate adjusting device 71 (maintains a constant flow rate value), and the remaining part is adjusted by the flow rate control device 70. The range of balance force control can be secured.

The control method of the flow control device 70 is the same as in the reference embodiment described above. That is, a motor current value, or a vertical axis position deviation, a speed deviation, and the like are output from the motor control device 81, converted into a necessary flow rate value by the calculation device 80, and input to the flow rate control device 70. As a result, even when a workpiece or jig having a different weight is attached to the vertical axis, it is possible to automatically control the air balance force and cancel the change in the weight as in the above-described reference embodiment. The same applies to the above formula (1) as an example of the flow rate conversion formula in which the position deviation Δz and the speed deviation Δv are added to the current value I.

Furthermore, by deforming the structure of the reference embodiment in this manner, new advantages. In other words, the flow rate control device 70 can adjust the flow rate more finely as the maximum flow rate is smaller. Therefore, in such a modification, the flow rate can be controlled more precisely. In addition, even if a failure (for example, the flow rate cannot be reduced) occurs in the flow control device 70, the influence on the air balance is small, and a situation where the vertical axis suddenly falls or rises can be avoided.

It is a figure which shows schematic structure about the prior art example which employ | adopted the air balance apparatus which arrange | positions a big air tank between an electropneumatic regulator and an air balance chamber. It is a figure which shows the outline of the cross-sectional structure along line AA in FIG. It is a figure which shows schematic structure of the air balance apparatus which concerns on the reference form relevant to this invention. It is a figure which shows the outline of the cross-sectional structure along line BB in FIG. FIG. 2 is a block diagram showing a configuration example used when controlling the exhaust flow rate of the air balance so as to reduce the load on the drive motor. It is a diagram showing a schematic configuration of the air balancing device according to the implementation embodiments of the present invention. FIG. 7 is a block diagram illustrating a configuration example used for controlling the exhaust gas flow rate of the air balance so as to reduce the load of the drive motor in the air balance device illustrated in FIG. 6.

Explanation of symbols

1, 2, 3 Air balance mechanism part 10, 40 Fixed part 11, 13, 41, 43, 45 Open hole 12, 42, 46 Flow path 14, 44 Air balance chamber 15, 48 Bearing part 20, 50 Movable part 21 Movable part 21 Unit 29 Air compressor 30 Pressure control device 31, 32, 34, 61, 62, 71, 72 Piping 33 Air tank 47 Air outlet 51 Vertical shaft mechanism 52 Motor 53 Position detector 60 Pressure adjustment device 70 Flow control device 71 Flow rate Adjustment device 73 Branch pipe 80 Arithmetic device 81 Motor control device 82 Amplifier

Claims (3)

The movable part can move linearly in the direction of gravity with respect to the fixed part with the opening of the movable part having a container shape having an opening directed downward and the fixed part inserted into the internal space of the movable part. Provided in
In the air balance device of the linear drive device that constitutes the air balance chamber that holds the pressurized air in the region excluding the region occupied by the insertion portion of the fixed portion in the internal space region of the movable portion,
First flow path means for supplying air pressurized to a constant pressure to the air balance chamber;
Second flow path means for exhausting air in the air balance chamber;
Flow rate control means for performing flow rate control of exhaust gas performed through the second flow path means,
The second flow path means has a first exhaust system and a second exhaust system separated from each other,
While a constant flow rate of air is exhausted through the first exhaust system, the flow rate of air exhausted through the second exhaust system is controlled by the flow control means,
The air balance device is characterized in that adjustment is performed to eliminate pulsation of air balance force by the air balance chamber through the flow rate control of the exhaust gas by the flow rate control means. The drive means of the linear drive device is a motor,
The flow rate control means includes means for determining a flow rate of the exhaust gas based on at least one index related to control of the motor so that a load on the motor is reduced. Item 2. The air balance device according to Item 1.   The air balance device according to claim 2, wherein the index includes a current value supplied to the motor.

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