Hydraulic actuator operation controller

Abstract: The present invention makes it possible to easily change the operation speeds of a hydraulic actuator using the control input of an operating instrument. A signal input from a control input detection means (17) which detects the control input of an operating lever is converted into a logical function by a signal conversion unit (22) which can increase or decrease the signal in magnitude and provide an output to pump control means (25) which outputs a command to capacity change means (first electromagnetic proportional control valve) of a hydraulic pump, and to a valve control means (26) which outputs an instruction to opening area control means (second electromagnetic proportional control valves) of a control valve.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to controllers for controlling the operation of a hydraulic actuator or the like. Such a controller is known for example from EP-A-0,297,682. 2. Description of the Related Art In general, as shown in Fig. 5, there are some controllers of this type which are provided with pump control means 25 which receives as an input a signal from a control input detection means 17 for detecting a control input of a hydraulic-actuator operating instrument 16. The control means outputs a control command to a capacity change means (an electromagnetic proportional control valve 12 for supplying hydraulic pressure to control a pump swash plate of a hydraulic pump 10 in the case of Fig. 5) of a capacity-change hydraulic pump 10 which supplies hydraulic pressure to a hydraulic actuator 7 in accordance with the input signal. The controller also indicates a valve control means 26 which outputs a control command to an opening area control means (electromagnetic proportional control valves 14U and 14D in the case of Fig. 5) of a control valve 13 for controlling the flow rate of the hydraulic fluid to be supplied to a hydraulic actuator 7. In the case of the above controllers, the valve control means 26 is set so as to output a control command in accordance with the spool stroke characteristic (shown in Fig. 6Z) of the control valve 13 corresponding to the control input of the operating instrument 16 and the pump control means 25 is set so as to output a control command in accordance with the pump swash plate displacement characteristic (shown in Fig. 6Y) of the hydraulic pump 10 corresponding to the control input of the operating instrument 16. In this case, however, the spool stroke of the control valve, that is, the opening area of the valve and the capacity of the hydraulic pump are previously set so that a proper relation is maintained between them. That is, the problems can occur in that a high pressure is produced between the hydraulic pump and the control valve if the amount of oil supplied from the hydraulic pump is too much for the opening area of the control valve but the hydraulic actuator is subjected to a vacuum condition if the amount of oil supplied from the hydraulic pump is too little for the opening area of the control valve. Therefore, these parameters are set so that the above problems do not occur. In recent years, a need has arisen for a controller which makes it possible to optionally change the operation speed of a hydraulic actuator for the control input of an operating instrument according to necessity correspondingly to the individual difference or the operation content of an operator in order to improve the workability and operability. Therefore, it is advocated for the above operation controller that the opening area of the control valve for the control input of the operating instrument can be changed by operation means such as an adjusting dial. In this case, however, the opening area of the control valve and the capacity of the hydraulic pump must be kept at a preset relation as described above. Therefore, when the opening area of the control valve is changed in correspondence with the control input of the operating instrument, the pump swash plate displacement value of the hydraulic pump must also be changed so as to maintain the above-described corresponding relation. However, there is a problem that the above control is practically difficult. The present invention attempts to solve this. Moreover, there has arisen a need to make it possible to optionally change the limited rate of a hydraulic actuator in correspondence with the operation of an operating instrument according to necessity. SUMMARY OF THE INVENTION The present invention attempts to solve the above problems by considering the above actual situation and its object is to provide a hydraulic controller for controlling operation of an hydraulic actuator means for receiving an input signal corresponding to a control input of a hydraulic-actuator operating instrument and for outputting a control command according to the input signal which is fed to capacity change means of a hydraulic pump for supplying hydraulic pressure to a hydraulic actuator, and valve control means for outputting a control command according to the input signal to an opening area control means of a control valve for controlling the flow rate of the hydraulic fluid which is supplied to the hydraulic actuator; characterized in that said operation controller includes signal increasing and decreasing means which can increase or decrease said signal by means of a plurality of preset logical functions, the signal being increased or decreased according to one logical function selected from said plurality of the logical functions being output to both of said pump control means and said valve control means. In this way the signal input from the operating instrument is converted to a logical function selected by the signal conversion means, the converted signal is output to the pump control means and the valve control means, and therefore, the operation speed of the hydraulic actuator for the control input of the operating instrument can easily be changed while maintaining the appropriate relation between the opening area of the control valve and the amount of hydraulic pressure supplied from the hydraulic pump. Thus, the operability and workability are improved. Moreover, because the limited rate of the control commands of the pump control means and valve control means corresponding to the signal input from the operating instrument is adjusted to a limited rate optionally selected from a plurality of preset limited rates, the limited rate of the hydraulic pump and the control valve to the operation of the operating instrument can be adjusted and the operability and workability are further improved. Furthermore, in the case of the controller, because a logical function and limited rate to be selected are determined by selecting any one of a plurality of combined modes set by optionally selecting one logical function and one limited rate out of a plurality of logical functions and a plurality of limited rates respectively, the logical function and the limited rate can simultaneously and easily be selected by the selecting operation means and thereby, the operability can further be improved. The invention will be described now by way of example only, with particular reference to the accompanying drawings. In the drawings: Figure 1 is a schematic side view of a hydraulic excavator; Figure 2 is an illustration showing the operation controller of a boom cylinder; Figure 3 is an illustration showing the structure of a control section; Figure 4V is a diagram in graph form showing logical functions, Figure 4W is a graph showing pump limited rates, Figure 4X is a graph showing valve limited rates, Figure 4Y is a graph showing a pump swash plate displacement characteristic, and Figure 4Z is a graph showing a spool stroke characteristic; Figure 5 is an illustration showing a conventional controller; and Figure 6Y is a graph showing a conventional pump swash plate displacement characteristic and Figure 6Z is a graph showing a spool stroke characteristic. DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention is described below by referring to the accompanying drawings. In the drawings, symbol 1 denotes a hydraulic excavator. The hydraulic excavator 1 comprises a crawler-type lower structure 2, a top revolving upper structure 3 rotatably supported above the lower structure 2, a boom 4 whose proximal end is pivotally supported at the front end of the upper structure 3, a stick 5 longitudinally pivotally supported at the front end of the boom 4, and a bucket 6 pivotally supported at the front end of the stick 5. Moreover, the excavator 1 is provided with a travelling motor and a swing motor (which are not illustrated), and various types of actuators such as a boom cylinder 7, a stick cylinder 8, and a bucket cylinder 9. Therefore, the basic structure of the excavator 1 is the same as that of a conventional one. Although in the case of this embodiment, the present invention is applied to a controller for controlling the operating of each of the above hydraulic actuators, it can similarly be applied to any type. Therefore, the case of the boom cylinder 7 to be described below is given as an example. The boom cylinder 7 extends or contracts in accordance with the hydraulic pressure supplied from the hydraulic pump 10 to be driven by the motive power of an engine. The hydraulic pump 10 is a variable capacity type comprising a pump swash plate-type axial piston pump whose discharge flow rate changes in accordance with the tilt angle displacement of a pump swash plate 10a and the pump swash plate regulator 11 of the hydraulic pump 10 is constituted so as to control the tilt of the pump swash plate 10a in correspondence with the pressure of pilot hydraulic pressure supplied from a first electromagnetic proportional control valve 12 to be mentioned below. In the drawings, symbol 13 denotes a control valve located in an oil line extending from the hydraulic pump 10 to the boom cylinder 7. The spool stroke of the control valve 13 can be changed in accordance with the pressure change of the pilot hydraulic pressure supplied from a second electromagnetic proportional control valves 14U and 14 to be mentioned later to pilot ports 13U and 13D, and the valve 13 comprises a flow rate control valve for supplying hydraulic pressure at a flow rate corresponding to the spool stroke to the boom cylinder 7. In the drawings, symbol 15 denotes a pilot pump for supplying hydraulic pressure to the first electromagnetic proportional control valve 12 and the second electromagnetic proportional control valves 14U and 14D. Furthermore, symbol 16 denotes a lever for operating the boom cylinder 7. In the case of the operating lever 16, the control input (amount of operation movements or angle) of an operator, that is, an operation angle  from a neutral position is detected by a control input detection means 17 such as an angle detection sensor and the detection signal is input to a control section 18 to be described below. The control section 18 comprises a microcomputer or the like, which is arranged so that it can receive as an input, signals from the control input detection means 17 and a mode change switch 19 to be mentioned later. The control section 18 outputs a control command to the first electromagnetic proportional control valve 12 and the second electromagnetic proportional control valves 14U and 14D in accordance with these input signals. The structure of the control section 18 will now be described below by referring to Fig. 3. In Fig. 3, symbol 22 denotes a signal conversion unit. The signal conversion unit 22 is arranged to receive as an input a signal from the control input detection means 17 and convert the magnitude of the input signal (that is, the magnitude of the control input of the operating lever 16) into a plurality of preset logical functions and to output these. Specifically, in the case of this embodiment, seven types of logical functions are preset as shown by (1) to (7) in Fig. 4V. That is, the conversion unit 22 is designed so as to output the input signal by increasing the input signal in magnitude by the logical functions (1) to (3), maintaining that of the signal by the logical function (4), and decreasing that of the signal by the logical functions (5) to (7). It is also arranged so that a logical function to be adopted out of the preset logical functions can be selected by the mode change switch 19. Moreover, the signal output from the signal conversion unit 22 is input to a pump rate limiter 23 and a valve rate limited 24. The rate limiters 23 and 24 restrict respectively the rate of pump swash plate displacement and the rate of spool movement of the control valve 13 when operating the operating lever 16. The relationship between the operation of the operating lever 16 and the opening movement of the control valve 13 is explained as follows: Namely, when operating the lever 16 there is set to be a certain relationship between the operation angle from a neutral position of the operating lever 16 and the opening area of the control valve 13. Therefore when the lever 16 is operated from the neutral position to the optional position the control valve 13 opens so as to achieve the preset opening area corresponding to said optional position (optional operation angle). And opening rate of the valve 13 is defined as change values of opening area of the valve 13 per unit time and is set not to exceed a preset upper limited rate. If the operating lever 16 is operated at a slow speed not exceeding the upper limited rate the opening area of the control valve 13 changes at the rate of the operating speed of the lever and if the lever 16 is operated at the speed exceeding the upper limited rate the opening area of the valve 13 is controlled to change based upon said upper limited rate instead of the operating speed of the lever 16. This relationship is applied to the pump swash displacement. According to a preferred embodiment, three levels of limited rates, "fast", "standard", and "slow" are set to the pump rate limited 23 and the valve rate limiter 24 respectively as shown in Figs, 4W and 4X. Moreover, this embodiment is constituted so that a limited rate to be adopted can be selected by the mode change switch 19. The mode change switch 19 is a switch for changing three preset modes of A, B, and C in the case of this embodiment, in which modes are changed in the sequence of A → B → C → A... whenever the switch 19 is pressed. In this case, the modes A, B, and C are combinations selected out of the above seven types of logical functions and the three types of limited rates by a logical function selecting dial and a limited rate selecting dial 21, which can optionally be set by an operator according to the operator's skill or operation content. For example, the mode A is set as the combination of the logical function (1) for increasing an input signal in magnitude with the limited rate "fast", the mode B is set as the combination of the logical function (4) with the limited rate "standard", and the mode C is set as the combination of the logical function (7) for decreasing the input signal in magnitude with the limited rate "slow". Though three modes are preset in the case of this embodiment, it will be appreciated that different numbers of modes, e.g. two modes or four or more modes, can be preset. A signal output from the mode change switch 19 is input to the signal conversion unit 22, pump limited rate adjustment unit 23, and valve limited rate adjustment unit 24. For example, when the mode change switch 19 is set to the mode A, the logical function (1) is selected by the signal conversion unit 22 and the limited rate "fast" is selected by the pump limited rate adjustment unit 23 and the valve limited rate adjustment unit 24. Symbol 25 denotes a pump control means. The pump control means 25 is arranged to receive as an input a signal sent from the pump limited rate adjustment unit 23 and to output a control command to the first electromagnetic proportional control valve 12 in accordance with the pump swash plate displacement characteristic (Fig. 4Y) of the hydraulic pump 10 for the preset control input of the operating lever 16 in order to control the pump swash plate of the hydraulic pump 10 in correspondence with the input signal. The pump swash plate displacement value for the control input of the operating lever 16 when the logical function (4), that is, the signal input from the control input detection means 17 is output at the original magnitude by the signal conversion unit 22 is set at the preset pump swash plate displacement characteristic. Symbol 26 denotes a control means. The control means 26 is arranged to receive as an input a signal sent from the valve limited rate adjustment unit 24 and to output a control command to the second electromagnetic proportional control valves 14U and 14D in accordance with the spool stroke characteristic (shown in Fig. 4Z) for the preset control input of the operating lever 16 in order to control the opening area of the control valve 13 correspondingly to the input signal. However, the spool stroke for the control input of the operating lever 16 when the logical function (4), that is, the signal input from the control input detection means 17 is output at the original magnitude by the signal conversion unit 22 is set as the spool stroke characteristic in a manner similar to the case of the pump control means 25. It will be appreciated that the pump swash plate displacement characteristic set for the pump control means 25 is related to the spool stroke characteristic set for the valve control means 26 so that the amount of hydraulic pressure supplied from the hydraulic pump 10 is appropriate for the opening area of the control valve 13. In the above structure, when it is detected by the control input detection means 17 that the operating lever 16 is operated, the control section 18 controls the opening area of the control valve 13 and the discharge quantity of the hydraulic pump 10 in order to extend or contract the boom cylinder 7 in correspondence with a signal input from the control input detection means 17. In this case, an operator can easily change the extension or contraction speed of the boom cylinder 7 by the control input of the operating lever 16. That is, the control section 18 is provided with the signal conversion unit 22 for converting the magnitude of a signal input from the control input detection means 17 to a plurality of preset logical functions to output them and a signal converted to a logical function selected out of the logical functions by the mode change switch 19 is input to the pump control means 25 and the valve control means 26 through the pump limited rate adjustment unit 23 and the valve limited rate adjustment unit 24. Moreover, control commands are output to the first electromagnetic proportional control valve 12 and the second electromagnetic proportional control valves 14U and 14D from the control means 25 and 26 and thereby, the capacity of the hydraulic pump 10 and the opening area of the control valve 13 are controlled and the boom cylinder 7 is extended or contracted in correspondence with these types of control. Thus, in the present embodiment, a signal input from the control input detection means 17 is converted to a signal with a magnitude selected by an operator by the signal conversion unit 22 and the magnitude-converted signal is output to the pump control means 25 and the valve control means 26. As a result, it is possible to simultaneously change the spool stroke of the control valve 13 for the control input of the operating lever 16 and the pump swash plate displacement value of the hydraulic pump 10 without changing the spool stroke characteristic and the pump swash plate displacement characteristic set for the valve control means 26 and the pump control means 25 respectively, that is, while keeping the correct relation between the opening area of the control valve 13 and the amount of oil supplied from the hydraulic pump 10. Thus, it is possible to easily change the extension or contraction speed of the boom cylinder 7 for the control input of the operating lever 16 in correspondence with the individual difference or operation state such as operation content of an operator and thereby, the operability and workability are greatly improved. Conversion of an input signal is performed by the signal conversion unit 22 in accordance with a preset logical function. In this case, by increasing the input signal in magnitude and converting the signal into a logical function to be output, it is possible to perform efficient operations because the boom cylinder 7 is quickly extended or contracted in accordance with a slight lever control input. Moreover, by decreasing the input signal in magnitude and converting it into a logical function to be output, it is possible to perform precise operations because the boom cylinder 7 is slowly extended or contracted in accordance with the same lever control input. Moreover, this embodiment makes it possible to adjust the limited rate of the hydraulic pump 10 and that of the control valve 13 because it is provided with the pump limited rate adjustment unit 23 and the valve limited rate adjustment unit 24. In this case, by operating the mode change switch 19, it is possible to simultaneously change the logical functions and the limited rates by one touch and further improve the operability and workability.

Claims: A controller for controlling the operation of an hydraulic actuator comprising pump control means (25) for inputting a signal corresponding to a control input of a hydraulic actuator operating instrument (16) and outputting a control command according to said input signal to capacity change means of a hydraulic pump (10) for supplying an oil pressure to a hydraulic actuator and valve control means (26) for outputting a control command according to said input signal to the opening area control means of a control valve (13) for controlling the flow rate of the pressure oil to be supplied to said hydraulic actuator, characterized in that said operation controller includes signal increasing and decreasing means (22) which can increase or decrease said signal by means of a plurality of preset logical functions, the signal being increased or decreased according to one logical function selected from said plurality of the logical functions being output to both of said pump control means and said valve control means. A controller according to claim 1, characterized in that said valve control means (26) and said pump control means (25) are controlled so that a rate of capacity change of a pump per unit time and a rate of opening area changes of a valve per unit time become the limited rates selected from a plurality of preset limited rates. A controller according to claim 2 characterized in that said logical function and said limited rate to be selected are determined by selecting any one of a plurality of combined modes set by selecting one logical function and one limited rate from a plurality of logical functions and a plurality of limited rates respectively.

Inventors: HASUIKE MAKOTO, MORIYA NAOYUKI, MUROTA ISAO, HASUIKE, MAKOTO, MORIYA, NAOYUKI, MUROTA, ISAO
Applicants: CATERPILLAR MITSUBISHI LTD, SHIN CATERPILLAR MITSUBISHI LTD.
Application year: 1997
Main classification: E02F9
IPC codes: F15B11, E02F9