KR960000575B1 - Device and method for shock absorber of hydrauric cylinder - Google Patents

Abstract

The method controls the damping force of the hydraulic/pneumatic cylinders when the cylinders are used as the actuator of the robot, excavator, loader, crane etc. The damping is performed when the piston of the cylinder is expanded or contracted at the hydraulic machinery having more than a cylinder controlled by the electromagnetic proportional flow control valve. The method consists of the step(S1, S5) for discriminating the position of the piston in the primary or secondary damping sector; step(S2, S3) for distinguishing the moving direction of the piston from the former direction; step(S4) for transmitting the reverse signal of the operation order signal to the electromagnetic proportional flow control valve through the low-frequency filter.

Description

Buffer control method of hydraulic cylinder and its device

1 is a view schematically showing the configuration of a hydraulic (or pneumatic) system including the present invention.

2 is a circuit block diagram showing the configuration of a cylinder buffer control apparatus according to a preferred embodiment of the present invention.

3 is a diagram showing characteristics of a general digital low pass filter.

4 shows the characteristics of a digital low pass filter employed in accordance with a preferred embodiment of the present invention.

5 is a diagram showing a relationship with the speed of an input voltage magneto-hydraulic (or pneumatic) cylinder of an electromagnetic proportional flow control valve.

6 is a view showing a change in the operating speed of the cylinder according to the output voltage of the filter.

7A to 7D are diagrams for explaining the setting of a buffer section of a cylinder.

8 is a flowchart for explaining a control method of a preferred embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

10: prime mover 30: operation signal generator

20a, 20b: variable displacement hydraulic pump 40: control unit

41: digital low pass filter 42,44: buffer section identification unit

43,45: command signal size and direction judgment part 46: or gate circuit

47a: switching section 47b: selecting section

60a, 60b: Hydraulic cylinder 50a, 50b: Electronic proportional flow control valve

70a, 70b: displacement detector

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for performing control for the cushioning of a cylinder in a hydraulic (air pressure) mechanical device such as a robot excavator, a loader, a crane, etc. using a hydraulic (or pneumatic) cylinder as an actuator. will be.

In the conventional hydraulic or pneumatic control device (operating mechanism of the hydraulic device, since the operating mechanism of the pneumatic device is almost similar, in the present specification, the hydraulic mechanism will be described later as an example), in particular, the hydraulic cylinder is employed as an actuator. In the construction equipment, a mechanical device was formed inside the cylinder to cushion the cushioning.

In such technology, the precision of mechanical processing for the shock absorber is required, and defects such as damage and breakage caused by friction are frequently generated during operation of the cylinder, and the shock effect is not sufficient, resulting in mechanical shock at the stroke end of the cylinder. As a result, there is a problem of reducing the workability of the driver by causing the shock and vibration of the equipment itself.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a method and a control apparatus in which the cushioning of the cylinder is made by electronic control of cylinder operation without depending on the mechanical configuration.

The method of the present invention for achieving the above object is any one of the first buffer section and the second buffer section in which the piston position of the cylinder is set to a predetermined length at both ends of the cylinder stroke region, respectively. Comparing the operation command data and the first reference data obtained by digitalizing the operation command signal instructing the operation of the cylinder when the piston displacement of the cylinder falls within the first buffer section; Determining that the piston movement direction of the operation command data is changed when the operation command data is large; and low frequency of the signal inverting the operation command signal when it is determined that the piston movement direction of the operation command data has not changed Causing a passing filtering signal to be provided to the electromagnetic proportional flow control valve; Determining whether the piston movement direction of the operation command data is changed by comparing the operation command data with the second reference data when the upper pressure falls within the second buffer section, and determining that the automatic command data is small. If it is determined that the movement direction is changed, causing the low pass filtering signal of the signal inverting the operation command signal to be provided to the electromagnetic proportional flow control valve; and wherein the piston displacement is provided in the first buffer section and the second buffer section. If it does not belong to any one of the section characterized in that it comprises the step of providing the operation command signal directly to the electromagnetic proportional flow control valve.

As another feature of the invention, at least one cylinder for converting fluid power, such as hydraulic pressure or pneumatic pressure, into linear motion provided from a solenoid controlled proportional flow control valve controlled by an electrical signal. The control device of the present invention for performing control for cushioning the piston of the cylinder in the fluid machine equipped with displacement detection means for detecting the piston displacement of the cylinder and generating a corresponding electric signal, and the cylinder A filter means for receiving an operation command signal for the operation of the digital signal and performing a digital low pass filtering process, and converting the output of the displacement detection means into a digital signal and comparing the first reference data and the second reference data, respectively. The first buffer section and the second arm set to predetermined widths at both ends of the cylinder stroke, respectively. First and second buffer section identification means for respectively determining whether the piston of the cylinder is located within any one of the charging sections and outputting corresponding first and second identification signals, respectively; The outputs of the two buffer interval identification means are enabled or disabled, respectively, and in response to the operation command signal being received and converted into a digital signal, the third reference value and the third reference value are respectively obtained. First determination means and second determination means for determining the magnitude of the operation command signal by comparing each of the four reference data, and for determining the direction of movement of the piston and outputting a predetermined electric signal indicating the result; Logical operation means for logically operating the output of the first judging means and the output of the second judging means, and controlled by the logic operation means so that the inversion signal of the operation command signal is And switching means for providing to the filter means, and selecting means for controlling any one of the operation command signal and the output signal of the filter means to be provided to the electromagnetic proportional flow control valve.

As another feature of the present invention, the above-described function realization means according to the present invention may be constituted by several processors and storage devices or by one microcomputer.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 schematically shows the configuration of a hydraulic system to which the present invention is applied.

In the drawings, reference numeral 10 denotes a prime mover such as a diesel engine, and 20a and 20b respectively denote a variable displacenlent type oil hydraulic pump driven by the rotational force of the prime mover 10. . Further, reference numeral 30 denotes an electric signal for operating an actuator (hereinafter referred to as an operation command signal) corresponding to a physical displacement of an operation means such as a joy stick or a paddle. An operating signal generator is shown, and 40 is a feature of the present invention, which is a control unit for performing control on all components in response to the operation command signals provided from the operation signal generator 30. Represented by reference numerals 50a and 50b, respectively, are well-known electromagnetic proportional flow control valves, and 60a and 60b represent hydraulic energy due to hydraulic fluids supplied from the electromagnetic proportional flow control valves 60a and 60b, respectively. Each of the hydraulic cylinders, which are mechanical actuators, is shown. Finally, those denoted by reference numerals 70a and 70b, respectively, are displacement detection units which generate electrical signals corresponding to the piston displacements of the cylinders 60a and 60b and provide them to the controller 40.

2 shows the configuration of the control unit 40 according to the preferred embodiment of the present invention. For the sake of simplicity, only the configuration of the control means associated with any one of the two hydraulic cylinders 60a and 60b is shown.

In the figure, denoted by reference numeral 41 is a digital low pass filter for filtering the output of the operation signal generator 30, and 42 and 44 are the displacement detectors 70a (or 70b) described above. Is a buffer section identification section that receives the piston displacement data of the cylinders 60a and 60b provided from the circuit and compares them with the predetermined reference data to discriminate the cushion section of the cylinder and output a predetermined identification signal indicating the result. . Reference numerals 43 and 45, respectively, are controlled by the identification signals provided from the buffer section identification units 42 and 44, respectively, and receive the outputs of the operation signal generator 30 described above, respectively, and operate command. A command signal magnitude and direction determination portion for discriminating the magnitude of the signal and the direction of movement of the pistons of the cylinders 60a and 60b and outputting a predetermined state signal indicating the result, respectively, and 46 is the command signal magnitude and direction determination portion. Is an or gate circuit that receives and outputs the output signals of (43, 45), and 47a is a digital low-pass filter inverting the operation command signal by the output of the or gate 46 when buffer control is performed. A switching unit 47b, which is provided to 81, is controlled by the output of the or gate circuit 46, which is a logic means, so that any one of the output of the operation signal generator 30 and the output of the filter 41 is provided. It is shown to select each to provide to the electronic proportional flow control valve (60a, 60b).

The switching unit 47a may be simply configured as a three-state inverter. In the following description, the buffer section identifying section 42 and 44 and the command signal size and direction determining section 43 and 45 are each composed of a processor having an A / D conversion means and a storage means such as a ROM. These are not shown in the drawings as they become apparent. The electromagnetic proportional flow control valves 50a and 50b are supplied with hydraulic oil from the variable displacement hydraulic pumps 20a and 20b driven by the rotational force of the prime mover 10. The electromagnetic proportional flow control valves 50a and 50b are supplied to the electromagnetic proportional flow control valves 50a and 50b. The amount of hydraulic oil provided to the hydraulic cylinders 60a and 60b as actuators is provided from the operation signal generator 30 to the control unit 40 according to the magnitude of the operation command signal having a magnitude corresponding to the physical displacement of the operation means. Is determined. The pistons of the hydraulic cylinders 60a and 60b are linearly moved by the amount of hydraulic oil (ie, hydraulic power) provided from the valves 50a and 50b. At this time, the control unit 40 including a microcomputer or a plurality of processors is the cylinder 60a, in accordance with the data signal provided from the displacement detection unit (70a, 70b) for detecting the piston displacement of the hydraulic cylinder (60a, 60b) Of the opening areas (not shown) of the valves 50a and 50b to control the amount of hydraulic oil flowing into the cylinders 60a and 60b so that the piston is not impacted at the stroke end of 60b). Adjust the size.

In general, the digital low pass filter 41 has an output waveform characteristic such as b for the unit pulse input signal a, as shown in FIG. 4 shows the input / output signal waveforms of the digital low pass filter 41 for buffering, in which c is the actuator operation command signal and d is the filter (b) from the switching unit 47a for buffering. 41 shows the waveform of the signal provided. Referring to FIG. 4, as the output of the switching part 47a drops to the low level potential Vcmin at the time to start of the buffering, the output level of the filter 41 is also continuously decreased until the time te of the end of the buffering. It can be seen. 5 shows a change in the movement speed of the piston in the cylinder (60a, 60b) according to the magnitude of the input signal of the electromagnetic proportional flow control valve (50a, 5ob).

In the figure, the right side shows the voltage of the signal supplied to the solenoid of the valves 50a and 50b when the pistons of the cylinders 60a and 60b are elongated with respect to the vertical axis, and the left side thereof is the cylinders 60a and 60b. When the piston of the contraction shows the voltage of the signal supplied to the solenoid of the valve (50a, 50b). In addition, the vertical axis of the coordinates represents the movement speed of the piston according to the voltage magnitude of the input signal provided to the valve (50a, 50b), respectively. The minimum value Vcmin, which is provided to the low pass filter 41 for the buffer, is the valve 50a, which corresponds to the minimum travel speed Uemin (or Urmin) of the piston at the time of expansion (or contraction) of the cylinders 60a, 60b. Equal to the minimum input Vemin (or Vrmin) of 50 b). Considering the input / output characteristics (see FIG. 4) of the filter 41 for the piston buffer of the cylinder and the movement speed characteristics (see FIG. 5) of the piston according to the input of the valves 50a and 50b, the filter 41 As shown in FIG. 6, the velocity curve e and the change of the speed of the piston from the time to the start of the buffer (to) to the time (te) to reach the minimum travel speed (Umin) of the piston are shown. The area α of the hatched portion below this velocity curve is the absolute displacement along the direction in which the piston of the cylinder moves (the direction of movement of the piston for expansion and contraction of the cylinder). This absolute displacement depends on the expansion and contraction of the piston as shown in Figs. 7 (a) to 7 (d). Fig. 7 (a) shows the displacement Dmin when the piston of the cylinder is contracted to the maximum possible, and (b) shows the displacement Dmax when the piston is extended to the maximum possible.

In addition, (c) of FIG. 7 shows the first buffer section 1 ₁ set to prevent the shock when the piston of the cylinder is contracted, and (d) is set to prevent the shock when the piston of the cylinder is extended. The second buffer section 1 ₂ is shown. In Fig. 7, two buffer sections 1 ₁ and 1 ₂ can be expressed as follows by absolute displacement Dmin and Dmax, cylinder shrinkage side buffer displacement (DCmin) and cylinder extension side buffer displacement (DCmax).

1 ₁ : DCmin-Dmin

1 ₂ : Dmax-DCmax

The control unit 40 selects one of the absolute displacements Dmin and Dmax according to the piston movement direction of the cylinder, that is, whether the piston is in a contracting or extending movement, and one of them and the displacement detection units 70a and 70b. Calculate, compare and review the data provided by the controller. 8 is a flowchart illustrating a control method for buffering performed by the controller 40.

In FIG. 1, a predetermined operating instruction for operating the actuator from the operating signal generator 30 is provided by the driver by operating the operating means to perform a predetermined work (for example, an excavation work by an excavator). The signal Vm is provided to the controller 40. The controller 40 adjusts the flow rate supplied from the pumps 20a and 20b to the cylinders 60a and 60b by controlling the driving of the valves 50a and 50b in response to the operation command signal Vm. Therefore, the operation (linear movement of the piston) of the hydraulic cylinders 60a and 60b as actuators is controlled so that the driver can perform a desired work. When the control unit 40 performing the control function as described above contracts or expands the piston of the cylinder to the maximum, it performs buffer control to prevent a collision occurring between the piston and the cylinder. Referring to this in detail with reference to the following.

When the driver moves the operation means, the operation signal generator 30 generates an operation command signal Vm corresponding to the physical displacement of the operation means. At this time, the displacement of the piston moving by the operation command signal is in any one of the first buffer section (1 ₁ ) set for the maximum contraction of the piston and the second buffer section (1 ₂ ) set for the maximum extension of the piston. In order to determine whether it belongs, the first buffer section identification section 42 may determine a predetermined stretch buffer displacement value corresponding to the first reference data when the value of the current piston displacement D provided from the displacement detection unit (for example, 70a). It is determined whether or not the value of DCm ax) (S ₁ ), and the second cushioning section identification section 44 determines that the predetermined contraction buffer displacement (DCmin) where the value of the current piston displacement D corresponds to the second reference data. (S ₅ ). The first when the piston of the cylinder proven to be in the buffer section ₍₁₂₎ of the second by the buffer section identifying unit 42 (and therefore, at this time the second buffer section identifying unit 44 is of course the piston of the cylinder No. It is determined that it is not within the buffer section 1 _1. ) A predetermined identification signal is output to enable the first command signal size and the direction determining section 43. In this case, the second command signal size and the direction determination unit 45 are disabled by the second buffer section identification unit 44.

The operation command provided from the operation signal generator 30 is provided with the first command signal size and the direction determination unit 43 enabled by the predetermined identification signal provided from the first buffer section identification unit 42. The signal is converted into a digital data signal and compared with the third reference data (Vemin) corresponding to the minimum movement speed Uemin (see Fig. 5) of the piston during piston extension operation. (S ₂ ). At this time, if the potential Vm of the operation command signal is found to be less than or equal to the potential Vemin corresponding to the minimum movement speed Uemin of the piston when it is extended, the determination unit 43 does not need control for buffering, so the state signal of the low level is Outputs However, if the potential Vm of the operation command signal is found to be larger than the potential Vemin, it is determined whether the actuator (i.e., hydraulic cylinder) operation command direction of the current operation command signal is different from the command direction of the operation command signal input immediately before. (S ₃ ). At this time, if it is found that the direction of the command is changed, the piston of the cylinder is in the process of being stretched and then contracted, and thus it is unnecessary to perform the buffer control for the stretching. Therefore, even at this time (i.e., when the potential Vm of the operation command signal is greater than the potential Vemin and the command direction is changed), the first command signal size and the direction determination part 43 output the low level status signal. However, if it is found that the operation command direction of the actuator has not changed (YES in step S ₃ ), the piston of the cylinder, which is the actuator, is in continuous extension motion, and thus buffer control is required.

Therefore, the first command signal magnitude and direction determination part 43 output the high level status signal so that the output of the filter 41 is provided to the electromagnetic proportional flow control valve 50a or 50b. As a result, the output of the or gate 46, which is a logic means, is high level irrespective of the second command signal size and the output of the direction determining section 45. FIG. The selector 47b selectively outputs the signal input to the first input terminal A when the level of the signal input to the selection input terminal Sel is low, and to the second input terminal B when the level is high. Outputs the input signal selectively. The switching unit 47a configured between the operation signal generator 30 and the digital filter 41 sets the potential level of the operation command signal from low to high (or when the signal provided from the or gate 46 is high level). High to low).

When the piston of the cylinder is extended by the operation command signal having a positive value as described above, the piston is in the second buffer section 1 ₂ and when the buffer control is required, the output of the or gate 46 is at a high level. As a result, the output of the switching unit 47a is converted into a stepped waveform such as d in FIG. 4 and the output of the filter 41 has a form such as Vc. The output Vc of the filter 41 is selected by the selector 47b and provided to the solenoid of the electromagnetic proportional flow control valve 50a or 50b to be provided from the hydraulic pumps 20a and 20b to the cylinders 60a and 60b. The amount of hydraulic oil is reduced exponentially. As a result, the speed of movement of the piston in the _second buffer section 12 of the cylinder is reduced exponentially to prevent the collision between the cylinder and the piston.

Although only the buffer control action during the piston extension operation has been described so far, the second buffer section identifying unit 44 and the second command signal size and direction, as shown by S ₅ to S ₈ in FIG. The determination unit 45 has a piston in the first buffer section 1 ₁ (S ₅ ), and the operation command signal value Vm is smaller than the fourth reference data Vrmin (see FIG. 5). It will be readily understood that (S ₆ ), the damping control for the contraction of the piston is made if the operating command direction does not change (S). That is, a signal obtained by low-pass filtering the inverted signal of the operation command signal (output signal of the filter 41) is provided to the valves 50a and 50b to provide the cylinders 60a and 60b from the pumps 20a and 20b. The amount of working oil is adjusted.

On the other hand, if it is found that the piston of the cylinder is not present in any one of the first buffer section 1 ₁ and the second buffer section 1 ₂ , the buffer control for expansion and contraction of the piston does not need to be performed. The first and second discriminating portions 43 and 45 are both disabled. Accordingly, the or gate 46 outputs a low level signal, and the switching unit 47a performs the buffer function instead of the inverter function, and the selection unit 47b performs the operation signal generator (B). The operation command signal provided from 30 is provided to the electronic proportional flow control valve as it is (S ₉ ). Therefore, the actuator is operated according to the operation command signal by the driver at this time.

By applying the present invention as described above to a hydraulic machinery (particularly, heavy construction equipment) using a hydraulic cylinder as an actuator, a conventional mechanical shock absorber is unnecessary in the manufacture of a cylinder, and the productivity and economy can be improved. It allows to maintain its durability and integrity. In addition, in the present invention, by controlling the hydraulic cylinder operation by the automatic control, mechanical shock and vibration of the equipment is prevented and work efficiency is improved.

Claims (2)

In a fluid machine having at least one cylinder operated by a fluid power controlled by an electromagnetic proportional flow control valve, a method is provided for buffering when the piston of the cylinder is stretched. Determining whether the piston is located in one of the first buffer section and the second buffer section, each set to a length of (S ₁ , S ₅ ), and wherein the piston is in the first buffer section. When located in the piston, if the digitally processed data (operation command data) of the operation command signal, which is an electric signal indicative of the expansion and contraction of the piston, is greater than the first reference data, it is determined that the piston is represented by the operation command data. further comprising: a movement direction determines whether or not the same as the previous direction of movement (S _2, S ₃₎ and the piston movement direction when the same phase When step that causes an inverted signal of the operation command signal provided to the electro-proportional flow control valve through a low-pass filter (S ₄₎ and, that the piston be located in the buffer region of the second the operation command data is the second If it is determined that it is smaller than the reference data or smaller, it is determined whether the piston movement direction of the operation command data is the same as the previous movement direction (S ₆ , S ₇ ) and the piston movement direction is the same. When the above operation instruction step in which the inverted signal of the signal to be provided to the electro-proportional flow control valve through the low-pass filter (S ₈₎ and the piston a buffer region of the buffer section of the first and the second If it not located in any one zone of a particular in that the operation command signal comprises the step (S ₉₎ to be directly provided to the electro-proportional flow control valve Buffer control method of the pneumatic and hydraulic cylinder as set. In a fluid machine having at least one cylinder for converting a fluid power provided by an electronic proportional flow control valve for controlling the amount of fluid by an electric signal into a linear motion, the low-pass filter and the piston displacement of the cylinder A displacement detection means for detecting and generating an electric signal corresponding thereto, and receiving the output of the displacement detection means and converting the digital signal into a digital signal, and comparing the first reference value and the second reference value, respectively, A first and a second for respectively determining whether the piston of the cylinder is located in one of the first and second buffer sections respectively set to the width and outputting corresponding first and second identification signals, respectively; The buffer section identification means and the outputs of the first and second buffer section identification means, respectively, in an enable state or a disabled state. In the enable state, the operation command signals are respectively received and converted into digital signals, and then the magnitudes of the operation command signals are determined by comparing with the third reference value and the fourth reference value, respectively, and the direction of movement of the piston is determined. First and second judging means for outputting a predetermined electric signal representing the result, respectively, logic arithmetic means for performing a logic operation on an output of the first judging means and an output of the second judging means, and the logical operation means. Switching means for controlling the inversion signal of the operation command signal to be provided to the low frequency filter; and selecting one of the operation command signal and an output signal of the low frequency filter to be controlled by the logic operation means. A buffer control device for a pneumatic cylinder, characterized in that it comprises a selection means provided by the proportional flow control valve.