JPH042359B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stroke positioning method for a hydraulic press such as a press brake.

In hydraulic presses such as press brakes, where the upper table and ram are operated by two hydraulic cylinders on the left and right, the stroke operation of both left and right hydraulic cylinders depends on their stroke amount and stroke speed. must be symmetrical.

In particular, the stroke positioning of the left and right cylinders is
In this type of hydraulic press, horizontal symmetry is an essential requirement for ensuring the operational accuracy of the press machine, and various methods have been used in the past.

For example, (a) so-called linear gauges are installed on the left and right sides of the upper table ram to capture the strokes on the left and right sides of the table, respectively, and the hydraulic cylinders on both the left and right sides are controlled by hydraulic servo valves until each stroke reaches the target value. (b) By providing limit switches at the left and right positioning points of the upper table, and operating these switches to switch the solenoid valves in the hydraulic circuits of each hydraulic cylinder. position,
Alternatively, (c) the stroke position is determined by setting or changing the operating position of the mechanical valve.

However, the above method (a) lacks economic efficiency because the so-called linear gauges and hydraulic servo valves are expensive, and the method (b) can be implemented easily and at low cost, but the positioning accuracy is low. The problem with method (c) is that it is difficult to achieve high-precision positioning because it depends on the ram speed and accuracy of the limit switch, and method (c) has the disadvantage that the stopping position may not be the same due to the influence of oil temperature.

The present invention has been made in view of the current state of stroke positioning in hydraulic presses as described above, with the purpose of providing a control method that allows highly accurate stroke positioning using relatively inexpensive components. The structure of this method is that in a hydraulic press in which a ram is stroke-operated by left and right hydraulic cylinders, one valve chamber is connected to a plurality of on-off valves with different opening diameters in the hydraulic circuits of the left and right cylinders. A servo valve is inserted into each opening/closing valve in parallel so that it can be opened and closed by an actuator provided individually, and a pulse signal corresponding to the unit movement of the left and right cylinders is applied to the stroke operation section of the left and right cylinders. A stroke amount detector is provided for each cylinder, and when both cylinders operate, each stroke amount is determined by a distance pulse signal, and each stroke speed is determined by an appropriate time pulse signal corresponding to the distance pulse signal. It is detected by a speed pulse signal in the form of a distance pulse/time pulse or a time pulse/distance pulse, and is detected as the current value of the stroke position of both cylinders and the speed at that time. Positioning points including points, and each stroke speed at each positioning point,
The distance pulse signal and the speed pulse signal are configured to be able to set the respective expected values expressed by or converted into these, and the respective stroke operations of the two cylinders are controlled by the stroke amount and its value with respect to the positioning points of both cylinders. The left and right cylinders are respectively controlled by servo valves in the hydraulic circuit, which are driven based on the result of comparing and calculating the planned value and the current value of the speed at the time, and then,
Regarding the left and right cylinders, the current values of the stroke amounts of both cylinders, or the current values of the stroke amounts and the current values of the stroke speeds of both cylinders are compared, and the deviation between the current values of both cylinders is eliminated. This system is characterized by controlling the servo valves of each cylinder.

Next, an example of implementing the method of the present invention will be explained with reference to the drawings.

In the press brake, 1a and 1b are hydraulic cylinders installed on the left and right sides of the machine to move the ram up and down, 2 is a pump that supplies pressure oil to both cylinders 1a and 1b, 2a is its drive motor, and 3 is a Servo valves 4a, 4b and a switching valve 5, which will be described later, are connected by piping to the pressure oil supply and discharge ports of both cylinders 1a, 1b.
A, 5b, regulating valves 3a, 3b, 3c, etc. are inserted to form a hydraulic circuit. In addition, 6 is an oil reservoir.

Thus, each rod 1 of the cylinders 1a and 1b
1a and 11b are connected to an upper table (not shown) equipped with a punch at the bottom via a ram (not shown), etc., and by supplying and discharging pressure oil to the cylinders 1a and 1b, The press operation is performed by making the punch perform a stroke operation, and in the present invention, both the cylinders 1a and 1b are driven by a control system as described below. This point will be explained below.

First, the servo valve 4a partitions a valve chamber 41a forming part of a hydraulic circuit into multiple valves (not shown) having different opening diameters in parallel, and each valve is equipped with an actuator 42a that can open and close each valve individually. At the same time, each actuator 42 is connected to the servo drive unit 4.
3a. Like the valve 4a, the servo valve 4b also has one valve chamber 41a, a plurality of valves (not shown in the figure), and an actuator 4 for each valve.
2b and a servo drive section 43b. In addition, each of the above-mentioned actuators 42a and 4
2b can be driven individually or collectively.

Next, the rod 11a of each cylinder 1a, 1b,
11b is associated with stroke amount detectors 7a and 7b which supply pulse signals corresponding to the stroke amount, for example, 100 distance pulse signals per 1 mm, when these strokes are activated. As the stroke amount detectors 7a and 7b, encoder type pulse generators are used as the stroke amount detectors 7a and 7b.
The rod is rotated by a roll that rotates in contact with the rod, and generates a pulse signal per unit movement of the rod.

Incidentally, the above-mentioned detector may be attached to a part other than the rod as long as it is a part of the press machine that performs stroke operation. Also. Of course, the above pulse signals are supplied correspondingly to each rod during its reciprocating stroke.

The pulse signals supplied from the detectors 7a and 7b indicate the stroke amount, that is, the current position, of the rods 11a and 11b from an arbitrarily determined origin, and at the same time, the supplied distance pulse signals are By making it correspond to a time pulse signal, for example, the distance pulse signal can be made to correspond to a time pulse signal with a unit amount, or a time pulse signal can be made to correspond to a distance pulse signal with a unit amount. The current stroke speed of 11a, 11b can be formed.

8a and 8b are current stroke amount detection units that count and store the distance pulse signals supplied from the detectors 7a and 7b, and 9a and 9b are distance detection units that count and store the distance pulse signals supplied from the detectors 7a and 7b. pulse,
A current stroke speed detection unit that detects the current stroke speed in response to time pulses supplied from the oscillators 10a and 10b; 11 indicates both cylinders 1a;
This is a setting section that sets the operating state of the motor 1b, for example, the acceleration and deceleration points including stopping, and the speed at those positions, using the scheduled stroke amount and the stroke speed at that time, that is, the scheduled value.

The planned stroke amount and planned stroke speed of the setting section 11 are determined by the initial processing sections 12, 15a, 15.
In b, the control signals for the servo valves 4a and 4b are processed and supplied to the servo drive units 43a and 43b, but when each cylinder 1a and 1b starts to operate, the stroke amount and speed thereof are changed. The current value and the expected value are compared and corrected by a signal formed by a calculation result.

That is, 13a and 13b are up-down counters that calculate the deviation between the distance pulses supplied from the current stroke amount detection units 8a and 8b and the distance pulses supplied from the setting unit 11 that indicate the expected values in each operating state. Mainly stroke amount comparison section,
Reference numerals 14a and 14b are comparison sections for the stroke speed at that time, and both comparison sections 13a and 14a, and
Based on the calculation results of 13b and 14b, the processing unit 12,
15a and 15b correct the control signals for the servo drive units 43a and 43b formed by the predetermined values.

In this way, both hydraulic cylinders 1a and 1b
The left and right hydraulic cylinders 1a are supplied with pressure oil from the same pressure oil supply source via servo valves 4a and 4b that are opened and closed to control the stroke amount and stroke speed for positioning. ，
This means that fine operation control can be performed for each of 1b.

Incidentally, in a press brake, the left and right hydraulic cylinders 1a and 1b normally operate at the same speed and the same stroke. Therefore, in principle, the planned stroke amounts and speeds for the left and right cylinders 1a and 1b are naturally the same, but they are not necessarily the same during stroke operation, so in the present invention, left and right cylinder 1
A and 1b were controlled individually.
However, if the left and right cylinders 1a and 1b are controlled individually, there is a concern that deviations may occur in the stroke operations of the left and right cylinders. For example, in the case of large press brakes, etc., the cylinder capacity or stroke is large, and due to various factors such as response delay and increase in oil temperature, it is necessary to supply pressure oil from the same pressure oil supply source. Even with control, a difference may occur between the stroke amounts of the left and right cylinders.

Therefore, in the present invention, the current positions of the left and right cylinders 1a and 1b are compared, and if there is a deviation, it can be corrected.

That is, the distance pulses supplied from the stroke amount detectors 7a and 7b of both cylinders 1a and 1b are constantly compared in the position comparison section 16, and based on the calculation result of this comparison section 16, the processing section 1
In step 2, for example, a control signal is generated to throttle the servo valve of the advancing cylinder and open the servo valve of the lagging side.

In this way, the unevenness of the current positions of the left and right cylinders can be corrected, so that in combination with the above-described fine positioning according to the present invention, more effective positioning can be realized.

From the above viewpoint, the present invention compares the stroke speeds of the left and right cylinders at the same position during stroke operation, which is considered to be one of the causes of the unevenness of the current positions of the left and right cylinders, although the control system is not shown. The speeds during the stroke of both cylinders may be controlled to be the same.

As a control system for the above, for example, the current stroke speeds of both cylinders formed in the current stroke speed detection parts 9a and 9b of both cylinders are constantly compared at the same time as their positions, and based on the speed deviation at the same position, Any device that corrects the control signals for the servo valves 4a and 4b may be used.

The present invention is as described above, and the stroke operation of a hydraulic press such as a press brake having hydraulic cylinders on the left and right is performed by determining the current stroke amount and the same speed of the left and right cylinders, and determining the scheduled value for each of them. Control is performed while comparing the current value, and at the same time, the current positions of the left and right cylinders are compared with each other, and if necessary, the speed at that point.This allows for unprecedentedly accurate stroke positioning. It can be realized. Furthermore, the configuration of the servo valves and stroke amount detectors required for this control, as well as the configuration of the control system, are extremely simple, so the control device can be manufactured at low cost and maintenance is simple. This method is extremely useful as a control method for hydraulic presses.

[Brief explanation of drawings]

The figure is a system block diagram showing an example of a control system for implementing the method of the present invention. 1a, 1b...hydraulic cylinder, 11a, 11b
... Rod, 2 ... Oil pump, 3 ... Piping, 4
a, 4b... Servo valve, 7a, 7b... Stroke amount detector, 8a, 8b... Current stroke amount detection section, 9a, 9b... Current stroke speed detection section, 11... Setting section, 12, 15a, 15b...
Processing section, 13a, 13b... Stroke amount comparison section, 14a, 14b... Stroke speed comparison section,
16...Position comparison section.

Claims (1)

[Claims] 1. In a hydraulic press in which the ram is stroke operated by left and right hydraulic cylinders, one valve chamber is partitioned in parallel with a plurality of on-off valves with different opening diameters in the hydraulic circuits of the left and right cylinders. A servo valve formed to open and close each opening/closing valve by an actuator provided individually is inserted into each valve, and a stroke amount that supplies a pulse signal corresponding to the unit movement amount to the stroke operating section by the left and right cylinders. A detector is provided for each cylinder, and when both cylinders operate, the respective stroke amounts are detected by a distance pulse signal, and the respective stroke speeds are determined by a distance pulse/time pulse by associating an appropriate time pulse signal with the distance pulse signal. Alternatively, it is detected by a speed pulse signal in the form of a time pulse/distance pulse, and is detected as the current value of the stroke position of both cylinders and the speed at that time, while positioning including the speed of both cylinders, stopping point, etc. point and each stroke speed at each positioning point, the distance pulse signal, and
The stroke operation of each of the two cylinders can be set by a scheduled value expressed by a speed pulse signal or converted into these, and the stroke operation of each of the cylinders is determined by the scheduled value of the stroke amount and the speed at that time with respect to the positioning point of both cylinders. The left and right cylinders are controlled individually by servo valves in the hydraulic circuits of the left and right cylinders, which are driven based on the results of comparison and calculation between the value and the current value, and then, for the left and right cylinders,
The current stroke amounts of both cylinders are the same, or
Positioning of a hydraulic press, characterized in that the current values of the stroke amounts and the current values of the stroke speeds of both cylinders are compared, and the servo valves of the respective cylinders are controlled so as to eliminate the deviation between the current values of both cylinders. Method.