DE3307267A1 - ELECTROHYDRAULIC CONTROL DEVICE - Google Patents

Description

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JLG Industries, Inc. JLG Drive, McConnellsburg Pennsylvania
V.St.A.

ELECTROHYDRAULIC CONTROL DEVICE

The invention relates to an electro-hydraulic control device for hydraulically operated machines, one of which is relatively sensitive control of the hydraulic fluid flow require for selected functions.

There are a variety of hydraulic machines that are hand operated and operator-grounded levers, Switches, etc. for controlling the hydraulic fluid flow used on the valves or cylinders of hydraulic motors, triggering the various machine functions v / earth. For example, in the case of aerial work platforms, such as those in general are described in US-PS 3776367, a control lever with automatic return to the central position in the basket used to raise and lower a telescopic boom

by regulating the flow of hydraulic fluid to the lifting cylinder to control.

Because such devices are used to keep workers in high altitude and often to bring confined spaces, the operator has to be sufficiently sensitive for safety reasons Have control of the movement of the boom and vorb. Proportional control valves have been proposed by several manufacturers in order to increase the degree of sensitivity for increase the control that an operator can have over the movement of the boom. Typical proportional control valves available are operated electromagnetically and are matched to pressures, whereby they are devices for feeling and monitoring fluid pressures at opposing ones Have sides of the liquid line and keep the ratio of these pressures at a) predetermined value. Theoretically Such devices work with analog signals from a hand control and would have a finer gradation of the Allow operator control of movement. · '

Certain shortcomings in the prior art control devices, and particularly in the control valve used as part of the same, make it impossible to obtain a satisfactory solution to the industry demand for a reliable, sensitive control device. First, the price of commercial proportional control valves because of their complicated mechanical components and high tolerances drove for satisfactory Be is required prohibitive. As a result, these are far from being widely accepted in the industry.

In addition, one relies on the proportional control valves currently in use on their ability to

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pressures under less than ideal working conditions to be precisely determined. The presence of contaminants in the oil so / ie Differences in viscosity can render the valves inaccurate, if not completely unusable. Since the Devices built into the circuit may result in replacement or repair or malfunction of the valves lead to costly downtime.

After all, the existing machines are often designed to to work in one of several modes under the given circumstances. In the example above, the working lift, with switching options to high resp. low engine power and high or low drive type. The operation of the control lever to "raise the The boom must trigger a different lifting or lowering speed, depending on the motor and drive type, a requirement the creation of a suitable hydraulic control device continue to be complicated.

Its a typical prior art control device uta houses a hydraulic motor, a source, the hydraulic fluid supplies to the hydraulic motor, an electrically controlled valve assembly for regulating the flow of fluid between the Source and the motor, as well as an actuator for the elec-

25. tric control of the operation of the valve assembly. The usual valve assemblies used include an electromagnetically actuated proportional control valve, as described above, which is operated with the help of an analog signal.

The invention is based on the object of an electrohydraulic To provide control device that selectively controls the flow of fluid between a hydraulic motor and a hydraulic pump regulates, and which is insensitive to changes in the Viscosity of the liquid and in the respective contamination

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degree of liquid is. An operationally efficient control device is to be created that is economical and easy to manufacture and can be adapted to changing operating conditions,
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This object is achieved according to the invention by an electro-hydraulic «? Control device in which the actuating element contains a signal generator for generating a variable analog signal and an analog-digital converter circuit which is electrically controlled by the analog signal generator, and in that the valve arrangement contains a plurality of digitally operated Ilehr step valves which are electrically controlled by the analog-digital converter circuit been. is can also be provided a circuit for generating a reference voltage, the plurality of individual Ausgangssponnungspegel p.ufweisti the change the reference voltage level of the analog signal generator and thereby the maximum allowable fluid flow through the valve assembly. The device can therefore operate in different operating modes in contrast to currently available control devices.

The above-described disadvantages are eliminated by the invention of the electrohydraulic control devices according to the prior art. First are the Hehrstufenver.itile less expensive in terms of valve arrangement than proportional control valves and can be easily exchanged at the point of use, thereby reducing downtime. Every single stage valve can be replaced individually in the event of malfunctions, and the entire valve arrangement is not necessary to exchange. The high-level valves continue to open and close due to a digital signal and are therefore less sensitive to contamination than analog valves of the liquid and changes in the viscosity of the liquid.

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Exemplary embodiments of the invention are shown on the basis of the figures explained in more detail. It shows:

Fig. 1A is a Logite diagram of the analog-to-digital converter circuit of the variable flow control device

flow.

Fig. 1B is a logic diagram for the circuit that provides the output control signal supplies for the control device. ·

Figures 1B and "1A are continuous with each other along line C-C tied together.

FIG. 2 is a logic circuit diagram of the switching device according to FIG Invention, which the analog range of the control device

according to the appropriate operating mode

Figure 3 is a block diagram of the variable flow valve assembly of the invention.

As can be seen from FIG. 1A, two analog-digital-voltage converter circuits 2, 4 are provided, preferably of the Lh type 3914 which provide several parallel outputs 1-15, indicated generally by the reference number 6. The circuits 2, 4 receive an analog voltage input signal via terminal 5 and digitally switch an output according to the Size of the input voltage through. V / enn e.g. the area of Analog inputs zv / ischen 0 and 8 volts, the circuits 2, 4 can be calibrated in such a way that they have a digital output for every 0.5 volt input voltage. Thus the line would 12 go to high level with an input signal of 6 volts at terminal 5, line 9 with an input voltage of 4.5 volts, line 4 at an input voltage of 2 volts u.s.v /. The lines 1 to 16 of the circuits 2, 4 are on

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positive voltage source 8 connected via 10 ohm resistors 10, and the remaining lines 17 to 20 of circuits 4 are connected to source 8 via 100 ohm resistors 12.
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As can be seen from Fig. 1B, which is the continuation of the logic circuit diagram of Fig. 1Λ, IIAND gates with B inputs, preferably of the KH 74030 type, are shown between the table, which is the decimal output of lines 1 to 16 of the analog-to-digital converter Convert 2.4 to binary coded deci mc ¹ If ο mat. The outputs of the UAKD gates 14, 16, Yu, 20 are connected via 5> 1 KohnM / iderstands 30 to a two-stage amplifier circuit, which consists of the transistors 22, 24 :! Type GES 6010, D45H2 is made up of voltage sources 26 or. 34 preloaded. The selected resistance values are represented by a 100 Ohm resistor 28 and a 120 Ohm resistor 32, which are connected to ground via a 15 Ohm resistor and an IN 914 diode 38.

The control signal outputs 40, 42, 44, 46 represent the 4 binary digits of BCD code 8421 and are used to control the operation of the variable control valves in the below ways to be explained.

FIG. 2 shows a voltage switching arrangement for changing the analog range of the controller of the corresponding machine function in accordance with the appropriate operating mode. A working lift has, for example, an articulated boom that is lifted by a lifting cylinder. The machine can operate in a high / low power mode, with the pump delivering more or less fluid to the lift cylinder, depending on the angle of the boom. whereby the lifting

speed decreases for safety reasons.

In the same way it is with machines that a locomotion can run on the ground while the boom is raised or is lowered, desirably, of high drive speed to switch to low drive speed when the angular position of the boom is the horizontal plane exceeds, for the same security reasons.

According to the invention, a manual control member (not shown) used to control the boom lift cylinder, the control member comprising a lever which automatically turns into the central position returns, and which extends along a limited, ten 3ogenbahn moved and operated a potentiometer.

The analog voltage signal v / eist generated by the potentiometer an amount, the value of which is determined by the angular position of the control lever or stick. The area of Analog voltage signals generated by the potentiometer can through the effect of the switching arrangement of FIG. 2 according to the variable Sizes of the corresponding motor / drive operating modes can be changed. The high drive signal is applied to terminal placed, and the high motor signal at terminal 50. The switching lo-. C-ik comprises four AND gates 54, 56, 58, 60 with two inputs each. The AND gate 60 controls a transistor circuit. (transistive network) .an, and control the gates 54, 56, 58 a voltage switching device 61 of the type "LF13P02. The AND gates 54, 56, 58, 60 are connected to signal terminals 48,

JO - driven, and negation circuits 52 of the type MM 74C04 r. Are provided, v / o this is appropriate for inverting the received signals. The outputs of the AND gates 54, 56, 58, 60 v / ground high resolved and select the output voltage range via amplifiers, switches and lines 63-62, 64-62, 65-62 and

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66, which emit an output voltage level to the manual control element at terminal 74 and an input voltage of 8.2 Volt received from hand control element at terminal 75. The exit of the AND gate 60 is generated by the alloy circuit 67 from the Τ3Φ MM 74C04 logically inverted and a switching arrangement which is a 12 volt Ouellc 68, a 24 Kohm resistor 69, a 10 Kohm-V / resistor 70, a diode 71 of type IN914 and a switching transistor 72 of type GES2907 contains.

The function of the switching arrangement of FIG. 2 is as follows. The voltage range of the manual control element is determined of the variable values for motor and drive modes the machine. If the position of the boom shows e-n, that low engine power and low driving force are required (e.g. raising the boom above the horizontal plane) the output of AND gate 50 is switched up and switches line 64 to output terminals 74. De: The 8.2 volt input from terminal 74 is through the 6.2 Kohn series resistor on line 64, and the voltage level is fed from terminal 74 to the manual control element. If so If the manual control element is moved through its arc path, an analog voltage signal is generated incrementally. This analog signal is applied to input 1 of Fig. 1A and an ECD encoded Control signal is generated as previously described. The same is true for high engine power and high drive power appear as indicated due to the position of the boom, the output of AND gate 60 is switched high by 67 inverted, and transistor 72 switches the 12 VoIt voltage source 68 via the output terminal 74 to the manual control element. As a result, it produces the same arc deflection of the hand control element incrementally an analog voltage of up to 12 volts, which is generated by the circuit of Fig. 1Λ and 1B in BCD format is implemented as previously explained.

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In Fig. 3, P denotes the hydraulic fluid pressure for the variable flow valve 76 which is passed through the Opening 7ö enters. A regulated opening BO is provided, to deliver oil from valve 76 to a directional control valve, in the case of the example described so far, oil for Boom Hubzylinner would lead. A transition hole 02 directs excess oil, which is not required due to the control signal applied to the valve, into the container return.

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As shown, there are four multi-stage valve inserts 04, 86, 88, 90 of a commercial type arranged in parallel and designed such that by actuation of an electromagnet be opened electrically based on the digital control signal. If there is no control signal from the manual control element to the valve is sent, none of the four valve cores is open. The dimensioning of the multi-stage valve inserts 84, 06, 88, 90 is selected according to the BCD format with 3.79, 7.57, 15.14, 30.28 liters per hour (1, 2, 4, 8 gallons per minute). The streak of liquid which enters through the opening 78 is measured by a pressure-flow compensator 92, which is a fixed Contains part of the valve. The function of the compensator 92 is to reduce the pressure at the regulated port 80 and to measure the pressure of the oil flow that builds up at the opening 70. The compensator 92 then opens, to divert the oil through the opening 82 to the tank so that the pump does not hit the closed valve inserts 84, 86, 88, 90 works at idle. The valve 94 is a pressure relief valve, that monitors the maximum system pressure and directs the entire pump flow through opening 82.

The example of the operation of the device results from following with reference to the figures. With regard to Fig. 2, it is assumed that the position of the boom is a

Working lift or the like via a feeler and logical Switching elements indicates that low engine power and low drive force is the appropriate mode of operation for the machine. The input value at terminals 48, 50 is therefore low so that AND gate 58 is switched high will. The 8.2 volts v / earth applied to terminal 75 through the 6.2 Kohm resistor to the hand control element (not shown) switched via terminal 74.

TO A manual control device or lever that controls the lifting of the boom controls, .moves an arcuate path and actuates a potentiometer. The analog output signal of the. Potentiometers therefore moves in the size range from 0 to the maximum voltage at terminal 74 when the control lever is through- " NEN actuation travel is pivoted. Assume that the position of the control lever sends an analog signal of 7 volts to the analog-to-digital converter circuit of Fig. 1A at 5 ebjibt Line 14 of LI-I 3914 circuit 4 goes high and is made up of the NANB gates and driver circuits of Figure 1B converted to BCD format.0111. The BCD control signal becomes 0111 then fed via the output terminals 40, 42, 44, 46 to the variable flow valve 76 of FIG. 3 '.

In Fig. 3 it is assumed that, when no control signal is sent, the four valve inserts 8.4, 86 ,. 83, 90 are closed and a fixed flow pump is delivering 57 liters (15 gallons) of liquid per minute to port 78. The four valve inserts 84, 86, 88, 90 are each so small that they have a throughput of 3.79, 7.57, 15, 14 and 30, 2z liters (1, 2, 4 or 8 gallons) per minute, based on a command, according to the BCD format. \ 'onn. DIE Becier the person H ^ ndsteuerorgan moved a BCO-Steuersirri ^a l is generated 1000 that 84'bewirkt the opening of the valve, the valves 86 are closed 88, 90. Denzufolrre werder

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3.79 liters (1 gallon) of liquid per minute of the regulated Port 80 to the controlled line while 53 liters (14 gallons) per minute by the action of the Pressure flow compensator 92 via the Übergangsbohrunf be returned to the tank. When the operator moves the control lever into the second step range, it closes The control signal generated controls valve 84 and opens valve 86 to admit 7.57 liters (2 gallons) per hour. In the example shown above, control signal 0111 opens valves 86, 88, 90, and 53 liters (14 gallons) per minute flow to regulated port 00, while 3.79 liters (1 gallon) flow back into the tank.

From the foregoing it can be seen that the valve assembly 76 does the decoding of the digital format BCD control signal in hydraulic units of liters per minute causes. Four valve inserts are selected in such a way that that they match the BCD code, but multiple valves could be used in considering the invention become, un a larger number of gradations and therefore one to result in increased control possibility, up to the limit value of the BCD code and the pumping system. The valve inserts can be used for special applications are dimensioned differently than described above. It should be noted that the valve inserts are digital be controlled and the need for expensive analog controlled valves is eliminated, which are mechanically proportionate are complicated and sensitive to environmental factors that reduce their performance. The invention facilitates also, if necessary, the corresponding replacement of defective or damaged valve inserts, which enhances the versatility the device increases and downtime is reduced.

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Claims (1)

Claims Electro-hydraulic ^ control device with a hydraulic motor, a fluid source that supplies hydraulic fluid to the hydraulic motor, one electric controlled valve assembly for regulating hydraulic flow between the source and the motor, and an actuator for the electrical control of the valve arrangement, characterized in that the actuating member has a signal generator (8) for generating a variable Analog signal and an analog-to-digital converter circuit (2, 4), which is controlled electrically by the analog signal generator (8), and that the valve arrangement includes a number of digitally operated multi-stage valves (84, 86, 88, 90) which are electrically operated by the analog-to-digital converter circuit (2, 4) can be controlled. 2. Apparatus according to claim 1, characterized in that each of the multi-stage valves an individually dimensioned Has liquid passage opening. cc * « Postal checking account: Karlsruhe 76979-754 Bank account: Deutsche Bank AG Villingen (BLZ 69470039) 146332 j5. Device according to claim 1 or 2, characterized in that that the valve assembly has an additional transition opening (82) contains. 4. Apparatus according to claim 1, characterized in that the actuator is a voltage generating circuit contains. 5. Apparatus according to claim U, characterized in that the circuit has a reference voltage source (68), an input divider circuit (61) which divides the reference voltage source into several individual output voltage sources, and a logic circuit (52, 54, 56, .58 , 60) which is connected in such a way that it applies one of the individual output voltages to the analog signal generator (b) 6. Apparatus according to claim 5, characterized in that. the analog signal generator (8) contains a potentiometer, to which the selected individual output voltage is switched will.