JPH0552202A - Hydraulic servo device - Google Patents

Abstract

PURPOSE:To provide an inexpensive, applicable hydraulic servo device which has a simple structure to be easily applied to existing facilities and serves high-speed performance, high precision and high response. CONSTITUTION:Servo valves 1, 2 of at least two large, small types which have flow property are arranged in parallel. On the way of servo current instructions or opening instructions from a control section 5 to servo valves 1, 2, function generators 7, 8 with the property corresponding to the magnitude of an instruction signal or a filter with a frequency band different therefrom are provided. Individual servo currents or opening instructions are made adjustable, high-speed performance is controlled by the large flow servo valve 1 and high precision and high response are controlled by the small flow servo valve 2. As a result, an inexpensive hydraulic servo device can be provided, which has no deterioration of the large flow servo valves 1, 2 and still serves high-speed performance, high precision and high response.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic pressure reducing device for applying a reduction force to a rolling roll of a rolling mill, or a hydraulic servo device used for controlling the position of a sliding nozzle of a continuous casting machine.

[0002]

2. Description of the Related Art A hydraulic rolling reduction device such as a cold rolling mill was originally expanded to improve the response of a positioning device using an electric rolling reduction system. It is well known that it has an overwhelming advantage in comparison. A hydraulic rolling-down device such as a cold rolling mill has two functions of adjusting the roll gap for adjusting the plate thickness or elongation during rolling, and rapidly opening and closing rolls for roll evacuation in the event of abnormal roll replacement, plate breakage, or narrowing. Street behavior,
In many cases, one hydraulic cylinder is also used. in this case,
The former requires an adjustment range of several μ to several hundred μ, and requires high accuracy. The latter requires a high-speed opening / closing operation with a long stroke of tens to hundreds of mm.

For example, a hydraulic pressure reduction device such as a cold rolling mill is
As shown in the block diagram of the control system in FIG. 6, the position of the piston ram 32 of the hydraulic cylinder 31 for reduction is determined by the position detector 33.
Detected by and fed back to the adder 34, and the setter 30
The set position input from is compared and calculated, and the deviation is output to the position control unit 35 to control the servo current or the opening of the servo valve 36. As shown in FIG. 7, the hydraulic circuit of the cylinder 31 and the servo valve 36 in this case has the servo valve 3 in the pressurizing side oil chamber 37 of the piston ram 32 of the hydraulic cylinder 31.
The pressure oil is supplied from the tank 38 via the hydraulic pump 39 via the nozzle 6. On the other hand, demands for improving product quality have become stricter year by year, and even with hydraulic control devices,
The demands for improvement of accuracy and responsiveness and speeding up of position change are becoming stronger. On the other hand, in the servo valve, which should be called the heart of the hydraulic control device, various improvements have been made to meet the above requirements, and high performance and highly reliable servo valves such as direct acting servo valves have been developed and applied. Has been done.

However, high-speed performance, that is, the large flow rate of the servo valve and the high accuracy and high responsiveness are fundamentally contradictory propositions, and when the flow rate is increased, wear of the spool of the servo valve itself, packing, etc. Naturally, the internal leakage due to the deterioration of the control becomes large and the control performance is inevitably deteriorated. Figure 9
[Fig. 4] shows an example of changes over time in the internal leak amount of the hydraulic servo valve. Normally, the internal leak amount (%) of the hydraulic servo valve is expressed as a percentage of the leak amount with respect to the rated flow rate (l / min).
If it exceeds -15%, problems such as hunting or abnormal opening / closing operations occur, and the situation becomes serious, almost unusable. In addition, the change pattern of the internal leak amount largely depends on the usage condition of the hydraulic servo valve, and when the minute opening / closing state is repeated, the deterioration pattern becomes faster, so avoid repeating the minute opening / closing as much as possible. Is desirable.

Similarly, in the case of a large flow rate servo valve, even if the opening signal of the servo valve or the servo current is small, the hydraulic flow rate becomes a relatively large flow rate, so that the accuracy of the entire control system deteriorates, for example, the offset error of the control amplifier. In some cases, the effect of cannot be ignored. As described above, the pressure reduction control is conventionally performed by one servo valve, but in this case, it was difficult to achieve both high speed performance, accuracy, and responsiveness.

As a countermeasure against this, a cylinder ram that is provided in the cylinder tube and that makes a stroke operation and a piston that makes a stroke operation in the same direction as the stroke direction of the ram are provided in the cylinder ram. A device for controlling the stroke movement of the ram by an independent hydraulic control system (JP-A-60-162513 and JP-A-62-130705) has been proposed. As shown in FIG. 8, the devices disclosed in JP-A-60-162513 and JP-A-62-130705 disclose a cylinder ram 42 in which the piston 41 is slidably incorporated, and the cylinder ram 42 is the piston 41. The piston 41 and the cylinder ram 42 are controlled by servo valves 44 and 45 having separate independent hydraulic circuits.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The devices disclosed in Japanese Patent No. 2513 and Japanese Patent Application Laid-Open No. 62-130705 can achieve the object of achieving both high flow rate, high accuracy, and high responsiveness, but the entire hydraulic cylinder device is complicated and large-scaled. Inevitably, the equipment cost will be high when newly installed and it cannot always be adopted.In addition, existing equipment requires renewal of the cylinder or major modification, which requires modification cost and man-hours. Has the drawback that it cannot be adopted. Moreover,
The above-mentioned hydraulic cylinder device has the drawbacks that the mechanism is complicated and therefore the failure frequency is high and the maintenance man-hour is large.

An object of the present invention is to provide a hydraulic servo device which has a simple structure and can be easily applied to existing equipment, is inexpensive and highly practical, and has high speed performance, high accuracy and high responsiveness. is there.

[0009]

Means for Solving the Problems The present inventors have conducted extensive studies to achieve the above object. As a result, by arranging a plurality of servo valves having two or more kinds of large and small flow rate characteristics in parallel and using a plurality of servo valves at the same time with one control circuit and without mutual interference, it is possible to reduce the cost. Therefore, the inventors have reached the conclusion that a hydraulic servo device having high-speed performance, high accuracy, and high responsiveness can be obtained, and reached the present invention.

That is, according to the present invention, the position, speed, pressure, etc. of the hydraulic cylinder are changed by using a flow rate adjusting valve such as a servo valve.
In a hydraulic servo device that controls based on a comparison calculation result of a feedback signal from a detector input to a control unit and a preset set value, a plurality of servo valves having two or more kinds of large and small flow rate characteristics are connected in parallel. A function generator having characteristics corresponding to the magnitude of the command signal is provided in the middle of the servo current command or opening command from the control unit to each servo valve, and individual servo current or opening command can be adjusted. I did.

Further, by using a flow rate adjusting valve such as a servo valve, the position, speed, pressure, etc. of the hydraulic cylinder are compared with a feedback signal from a detector input to the control unit and a comparison calculation result with a predetermined set value. In a hydraulic servo device that is controlled based on the above, a plurality of servo valves having flow characteristics of two or more types of large and small are arranged in parallel, and a frequency band of a frequency band is provided in the middle of a servo current command or an opening command from the control unit to each servo valve. By providing different filters, the servo current or opening command of each servo valve can be adjusted according to the frequency band. Further, a large flow solenoid valve is provided together with a plurality of servo valves having two or more types of large and small flow characteristics.

[0012]

In the hydraulic servo system according to the present invention, a plurality of servo valves having two or more kinds of flow characteristics of large and small are arranged in parallel, and the opening signals of the large flow servo valve and the small flow servo valve from the control unit or The magnitude of the servo current is divided by the function generator or filter, and multiple servo valves can be used simultaneously with one control circuit and without mutual interference, so that the large flow servo valve and the small flow servo valve can be used. High-speed performance and
Both high precision and high responsiveness are achieved. In addition, the mechanism is simple and inexpensive if a single control circuit and hydraulic system are used without separately making the hydraulic systems for the large flow rate servo valve and the small flow rate servo valve independent.

Further, in a system such as a hydraulic pressure reducing device of a rolling mill which carries out a subtle operation of a hydraulic cylinder at high frequency, by using the hydraulic servo device of the present invention,
High accuracy and high responsiveness are achieved by controlling the opening and closing of the small flow rate servo valve, so the spool of the large flow rate servo valve has an opening of 0.
It is possible to prevent the abrasion of the spool, the occurrence of sticks, etc. due to the frequent opening and closing operations in the vicinity of, and the extension of the life of the large flow rate servo valve and the deterioration of the control performance.

Since a large flow solenoid valve is provided together with a plurality of servo valves having two or more large and small flow rate characteristics, a small flow servo valve and a large flow solenoid valve are combined, or a small flow servo valve and a large flow rate are provided. When a solenoid valve and a large flow servo valve are combined and a high-speed opening / closing operation is required for roll evacuation in the event of roll changes, plate breakage, narrowing, etc., a large flow solenoid valve or a large flow solenoid valve and a large flow rate The same effect as described above can be obtained even if the servo valve is used and high-responsiveness, high-precision opening / closing is performed by the small flow rate servo valve.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram of a control system provided with a function generator of a hydraulic servo device of the present invention, FIG. 2 is a block diagram of a control system provided with filters of different frequency bands of the hydraulic servo device of the present invention, FIG. Is a hydraulic system diagram of the present invention, FIG. 4 is an explanatory view showing an example of a step response of the position control system of the prior art, the first embodiment of the present invention device and the second embodiment of the present invention device, and FIG. 5 is the frequency of FIG. It is a diagram which shows the characteristic of the filter which a band differs. In FIG. 1, 1 is a large flow rate servo valve, 2 is a small flow rate servo valve, 3
Is a piston tube of the cylinder, and 4 is a cylinder ram provided in the piston tube 3. 5 is a position controller, 6
Is a position command signal, 7 and 8 are function generators, 9 is a position detector for detecting the position of the cylinder ram 4, and the position detector 9
The position of the cylinder ram 4 detected in 1 is fed back to the adder 10. The adder 10 is configured to compare and calculate the position command signal 6 and the position signal of the cylinder ram 4 fed back from the position detector 9, and output the deviation to the position control unit 5.

The function generators 7 and 8 have the characteristics shown in FIG. 1, and the function generator 7 receives the output of the position control unit 5 as an input and when the input is large. It is valid and has a characteristic that it is invalid or the gain is sufficiently small when the input is small. Further, the function generator 8 has such a characteristic that the output of the position control unit 5 is effective when the input is small and is limited to a constant output when the input is large. Therefore, when the servo current command or the opening command from the position controller 5 is large, the output of the function generator 8 is limited to a constant value, and the function generator 7 controls the servo current or the opening of the large flow rate servo valve 1. Controlled. Conversely, when the servo current command or the opening command from the position control unit 5 is small, the output of the function generator 7 is invalid or the gain is limited to a sufficiently small value, and the function generator 8 causes the servo current of the small flow rate servo valve 2 to be reduced. Alternatively, the opening degree is controlled.

In FIG. 3, 11 is an oil tank and 12
Is a hydraulic pump, 13 is a motor for driving the hydraulic pump 12, 1 is a large flow servo valve, 2 is a small flow servo valve, 3 is a piston tube of a cylinder, 4 is a cylinder ram provided in the piston tube 3, and 14 is an accumulator. , 15 are pressure reducing valves, and the pressurizing side oil chamber 16 of the cylinder ram 4 has a large flow rate servo valve 1 and a small flow rate servo valve 2 arranged in parallel.
And is connected by pressure oil piping.

In FIG. 2, 1 is a large flow rate servo valve, 2 is a small flow rate servo valve, 3 is a cylinder piston tube, 4
Is a cylinder ram provided in the piston tube 3.
Reference numeral 5 is a position control unit composed of an amplifier, 6 is a position command signal, 21 and 22 and 23 are filters having different frequency bands, 9 is a position detector for detecting the position of the cylinder ram 4, and 9 is a position detector 9. The detected position of the cylinder ram 4 is fed back to the adder 10. The adder 10 is configured to add the position command signal 6 and the position signal of the cylinder ram 4 fed back from the position detector 9, and output the deviation to the position control unit 5.

Filters 2 having different frequency bands
As shown in FIG. 5, Nos. 1, 22 and 23 are characteristics that the filter 21 of FIG.
The filter 22 in the figure has a characteristic of passing only a medium frequency band, and the filter 23 of (c) has a characteristic of passing only a high frequency band. Therefore, the position control unit 5
When the servo current command or the opening command from is large and in the low frequency band, the gain is set by the filter 21 and the servo current or the opening of the large flow rate servo valve 1 is controlled.
Conversely, when the servo current command or the opening command from the position controller 5 is small and in the high frequency band, the gain is set by the filter 23 and the servo current or the opening of the small flow rate servo valve 2 is controlled.

In FIG. 4, the conventional example is the hydraulic servo device shown in FIGS. 6 and 7, the first embodiment is the hydraulic servo device shown in FIGS. 1 and 3, and the second embodiment is the servo device shown in FIGS. 2 and 3. 3 is a diagram of a step response of the position control system of FIG. The servo command A in FIG. 4 indicates the servo opening of the large flow rate servo valve 1, and the servo command B indicates the servo opening of the small flow rate servo valve 2. The servo flow rate is a combination of the flow rates of the large flow rate servo valve 1 and the small flow rate servo valve 2 in Embodiments 1 and 2, and the broken line represents the flow rate of the small flow rate servo valve 2. Position feedback represents feedback from the position detector 9. As is clear from FIG. 4, if the hydraulic cylinder position control is performed by the method of the first embodiment shown in FIGS. 1 and 3, and the second embodiment shown in FIGS. By arranging 2 in parallel and combining them,
It is possible to obtain a response that is equal to or higher than that using one servo valve.

In the first embodiment shown in FIGS. 1 and 3, when the position deviation is small, the function generator 8 controls the position of the small flow rate servo valve 2 only. In the second embodiment shown in FIG. 3, in the high frequency region, that is, in the normal control range passing through the filter 23,
The position is controlled only by the small flow rate servo valve 2. Therefore, when the amount of positional change is small and the change in the high frequency range is large during rolling of a rolling mill,
Only the small flow rate servo valve 2 is often used, and only when a large amount of position change is needed in a very short time, such as rapid roll opening / closing for roll evacuation in the event of abnormal roll replacement, plate breakage, narrowing, etc. The flow rate servo valve 1 will be used.

In the above embodiment, the case where a plurality of servo valves having two or more large and small flow rate characteristics are arranged in parallel has been described, but a plurality of servo valves having two or more large and small flow rate characteristics are provided. High accuracy and high responsiveness are required by installing a large flow solenoid valve and combining a small flow servo valve and a large flow solenoid valve or a small flow servo valve and a large flow solenoid valve and a large flow servo valve. When using a small flow rate servo valve, and when a large amount of position change is required in a short time, use a large flow rate solenoid valve or a large flow rate solenoid valve and a large flow rate servo valve to achieve quick roll opening and closing. Can be implemented as

[0023]

As described above, according to the present invention,
In a hydraulic servo system where there are many small and relatively high-frequency position changes, deterioration due to frequent opening / closing operations of the large flow rate servo valve is eliminated, and internal leakage etc. of the large flow rate servo valve is eliminated. It is possible to inexpensively provide a hydraulic servo device that is less affected by. Although the present invention has been described with respect to the example of the position control device, it can be applied to hydraulic pressure control, speed control and the like.

[Brief description of drawings]

FIG. 1 is a block diagram of a control system provided with a function generator of a hydraulic servo system according to the present invention.

FIG. 2 is a block diagram of a control system provided with filters of different frequency bands in the hydraulic servo device according to the present invention.

FIG. 3 is a hydraulic system diagram of the position control device of the present invention.

FIG. 4 is an explanatory diagram showing an example of a step response of the position control system according to the first embodiment and the second embodiment of the conventional device of the present invention.

5 is a diagram showing characteristics of filters having different frequency bands in FIG. 2, where (a) is a low frequency band, (b) is a medium frequency band, and (c) is a high frequency band. Indicates.

FIG. 6 is a block diagram of a control system of a conventional general hydraulic servo device.

FIG. 7 is a hydraulic system diagram of a conventional general position control device.

FIG. 8 is a hydraulic system diagram of a conventional position control device disclosed in JP-A-60-162513.

FIG. 9 is a graph showing an example of changes over time in the internal leak amount of the hydraulic servo valve.

[Explanation of symbols]

 1 Large flow rate servo valve 2 Small flow rate servo valve 3,43 Piston tube 4,42 Cylinder ram 5 Position control section 6 Position command signal 7,8 Function generator 9,33 Position detector 10,34 Adder 11,38 Oil tank 12, 39 Hydraulic pump 13 Motor 14 Accumulator 15 Pressure reducing valve 16, 37 Pressure side oil chamber 21, 22, 23 Filter 30 Setting device 31 Pressure reduction cylinder 32 Piston ram 35 Control section 36, 44, 45 Servo valve

Claims (3)

[Claims] 1. A comparison calculation result of a feedback signal from a detector input to a control unit and a predetermined set value for the position, speed, pressure, etc. of a hydraulic cylinder using a flow rate adjusting valve such as a servo valve. In a hydraulic servo system that is controlled based on the above, a plurality of servo valves having two or more types of flow characteristics, large and small, are arranged in parallel, and a command signal is issued during the servo current command or opening command from the control unit to each servo valve. 2. The hydraulic servo device according to claim 1, wherein a function generator having characteristics corresponding to the magnitude of is provided so that each servo current or opening command can be adjusted. 2. The position, speed, pressure, etc. of the hydraulic cylinder are calculated using a flow rate adjusting valve such as a servo valve as a comparison calculation result of a feedback signal from a detector input to the control unit and a predetermined set value. In a hydraulic servo device that is controlled based on the above, a plurality of servo valves having flow characteristics of two or more types of large and small are arranged in parallel, and a frequency band of a frequency band is provided in the middle of a servo current command or an opening command from the control unit to each servo valve. A hydraulic servo device characterized in that a plurality of different filters are provided and the servo current or opening command of each servo valve can be adjusted according to the frequency band. 3. The hydraulic servo device according to claim 1, wherein a large flow solenoid valve is provided together with a plurality of servo valves having two or more types of large and small flow rate characteristics.