FR2524945A1 - ELECTRO-HYDRAULIC CONTROL SYSTEM FOR FINE CONTROL, FOR EXAMPLE FOR POSITIONING THE NACELLE AT THE END OF THE ARROW OF A WORKING VEHICLE - Google Patents

Abstract

THIS SYSTEM INCLUDES AN ELECTRONIC ASSEMBLY TO TRANSFORM AN ANALOGUE ELECTRICAL SIGNAL PROVIDED BY A MANUAL CONTROL UNIT (INCLUDING A POTENTIOMETER FOR EXAMPLE) INTO A BINARY CODE DECIMAL CONTROL SIGNAL, AS WELL AS A FLOW ADJUSTMENT VALVE 76 TO WHICH IS APPLIED. SIGNAL. THE VALVE INCLUDES, FOR EXAMPLE, FOUR CARTRIDGE VALVES 84, 86, 88, 90 INDIVIDUALLY CONTROLLED BY SOLENOID, THE FLOW CHANGES OF WHICH ARE DIMENSIONED SO THAT THEIR FLOWS ARE STEPPED ACCORDING TO CODE DCB8421. THE DIGITAL CONTROL SIGNAL PROVIDED BY THE ELECTRONIC MOUNTING ALSO ALLOWS PRECISE INCREMENTIAL ADJUSTMENT OF THE FLOW OF HYDRAULIC FLUID SENT, FOR EXAMPLE, TO THE JACK FOR LIFTING A Boom.

Description

The present invention relates to a system (device)

  control for hydraulically driven machines requiring

  relatively sensitive flow of hydraulic oil flow for

specific functions.

  Many types of hydraulic machines are manually operated, the operator operating levers, levers, switches and so on to establish, cut or adjust the flow of hydraulic fluid sent to distributors, valves, jacks, or other motors driven by a fluid so as to control the various functions of the machine For example, on work machines having an arm or an arrow with at the end a nacelle for a worker, of the general type described by the patent of the United States

  No. 3,776,367, a control lever known as "self-return

  matic in neutral position ", installed in the nacelle, is used to control the raising and lowering of a telescopic boom by adjusting the flow rate of hydraulic fluid sent to or expelled

a lifting cylinder.

  As this kind of material is used to place workers in high working positions and where freedom of movement is often limited, the worker must be able to control the movement of the boom carrying the basket with sufficient sensitivity or softness for reasons Safety devices Various manufacturers have proposed proportional control valves to increase the degree of sensitivity with which the worker can operate the

  arrow The valves currently existing on the market are typically

  only solenoid-operated and whose action is based on

  pressure, with means for detecting and varying the pressures

  sions of fluid at the ends of the supply piping and

  to maintain the ratio of these pressures to a preset value.

  These proportional control valves are controlled by an analog signal delivered by a manual control member and are supposed to allow more progressive or finer control of the movement.

by the worker.

  Certa Inesi Mperfections of art control systems, in particular their proportional control valve, prevent reaching a satisfactory solution for the needs of the industry of a safe and sensitive control system Primo, proportional control valves that are found on the market are excessively expensive because of the complexity of the mechanical parts which compose them and the tight tolerances with which they must be manufactured so that the valves function properly. The result is that their use by industry did not

not generalized.

  Second, the proper functioning of the proportional control valves currently in service is dependent on their ability to detect pressures accurately in

  working conditions which may not be ideal The pre-

  the presence of impurities in the oil and differences in viscosity can make the valve imprecise or even faulty As the various control and distribution devices are connected in series, replacement or repair of a defective valve

  can cause a long and costly shutdown of the entire machine.

  Third, current machines are often designed to be able to operate in several modes, depending on the circumstances. In the application mentioned above, the electro-hydraulic control system for positioning the nacelle can have fast and slow modes for maneuvering the plug and fast and slow modes for moving the vehicle or the support on which the boom is mounted Handling the lever

  boom lift control must produce an ele

  vation Of lowering which differs according to the operating modes

  arrow and displacement used.

  This requirement represents an additional complication

  in the realization of an adequate hydraulic control system.

  A control system typical of the prior art includes

  takes a jack, or other motor driven by a pressure fluid, a source of fluid to deliver pressure fluid to the jack, a valve or similar device with electrical control to regulate the flow of fluid between the source and the jack and an operating member for electrically controlling the operation of the valve Some commonly used control systems include, as described above, a control valve proportional to

  solenoid driven by an electrical-analog signal.

  According to the invention, such an electro-

  hydraulic is characterized in that the operating member comprises

  a variable analog signal generator and a converted circuit

  analog-digital sor, the input of which is electrically connected to the analog signal generator, and in that the valve has numerically controlled valves for incrementally regulating the flow rate of the valve, which are electrically controlled by the analog converter circuit -digital The system can additionally include a reference voltage generator circuit

  having multiple outputs having different voltage levels

  to change the voltage reference level of the analog signal generator and thus change the maximum admissible flow rate of the valve In this way, the system can work in several

  modes, unlike the systems that currently exist.

  The invention eliminates the drawbacks described in the foregoing of the Q-hydraulic electr control systems of the art. less expensive than proportional control valves and can easily be replaced at the place of use of the machine, which reduces downtime In the event of a malfunction, it is not necessary to replace the entire valve because each of its valves can be replaced individually In addition, the valves open and close

  in response to a digital signal and are therefore less sensitive

  so that the valves with analog control to impurities in

  hydraulic fluid and variations in its viscosity.

  The invention thus provides an electro-

  hydraulic which allows to selectively and repro-

  ductile the flow of pressure fluid between a pump and a jack and which is insensitive to changes in the viscosity of the fluid and to its possible contamination by solid impurities In addition, the system according to the invention can be manufactured economically and

  easily and it is adaptable to different operating modes.

  Other characteristics and advantages of the invention

  will emerge more clearly from the following description of a

  preferred but in no way limiting example of embodiment, as well as accompanying drawings, in which: FIG. LA is a logic diagram of the analog-digital conversion circuits of a variable rate control system according to the invention; Figure l B is connected to Figure l A along line C-C and is a logic diagram of the circuits supplying the output with a control signal for this system; FIG. 2 is a logic diagram of switching circuits, also forming part of the system of the invention which serve to establish the range in which the analog signals of the control mechanisms can vary according to the appropriate operating mode; and Figure 3 is a block diagram of a valve

  variable rate control and digital control according to the invention.

  Figure l A shows two analog-digital voltage converter circuits 2, 4, preferably of the LM 3914 type, which are connected in parallel and have multiple outputs.

  parallels a o designated as a whole by the reference 6.

  The components 2, 4 receive an input signal via a terminal 5 in the form of an analog voltage and make a determined output digitally active corresponding to the amplitude of the input voltage. For example, if the input signals can vary in a range from 0 to 8 V, components 2, 4 can be calibrated to deliver a digital signal on a determined output for each 0.5 V of input voltage So line 1 would go high for a signal SV input on terminal 5; line i would go high for an input signal of 4.5 V line d would go high for an input signal of 2 V; and so on The lines ap of the components 2, 4 are connected to a positive voltage source 8 through resistors 10 of kn, while the excess lines qt of unit 4 are connected to the voltage source 8 through resistors 12 of k 11 Figure l B, which is the continuation of the logic diagram in Figure LA, represents four NAND gates 14, 16, 18, 20 having

  each eight inputs, preferably of the type MM 74030, which converge

  weave the decimal output signal appearing on the CAN lines a p 2, 4 into a signal representing a binary coded decimal number. The outputs of the NAND gates 14, 16, 18, 20 are connected through resistors 30 of 5.1 k A to a two-stage amplifier circuit formed

  of transistors 22, 24 of types GE 56010, D 45 H 2, polarized respectively

  by voltage sources 26 and 34 The circuit further includes a resistor 28 of 100 ka, a resistor 32 of 120 ohms and a ground connection by a resistor 36 of 15 k f and a diode 38

type IN 914.

  On the four control signal outputs 40, 42, 44, 46 appear the four binary digits of the code DCB 8421 which are used to control the operation of the control valve to

  variable flow rate as described in detail in the following.

  FIG. 2 represents a voltage switching circuit for changing, according to the operating mode which is suitable each time, the range in which the analog signal supplied by the operating member of the machine considered can vary.

  example, in the case of a nacelle carried at the end of an articulated arrow

  abutment lifted by a lifting cylinder, the machine can operate in a fast boom operating mode or in a slow boom operating mode, in which the pump sends a greater or lesser quantity of pressure fluid to the lifting cylinder, depending on the inclination of the arrow If the inclination of the arrow is above the horizontal, the flow rate of the pressure fluid sent to the jack is less, which decreases, for safety reasons,

  the boom elevation speed.

  Similarly, on machines capable of this-

  place on the ground while the boom is raised or lowered, it is desirable to switch from a high moving speed to a slow moving speed when the boom rises above

  horizontal, for the same security reasons.

  In the present example of implementation of the invention, a manual operating member (not shown) is used to control the boom lifting cylinder; this member is of the type comprising a return lever in the neutral position, which is movable

  following a determined arc and is coupled to a potentiometer.

  The amplitude of the analog voltage signal produced by the potentiometer is determined by the position of the control lever or joystick on its arcuate path. The range of analog voltage signals produced by the potentiometer can be changed by the circuit of Figure 2 switching according to the modes

  appropriate boom and movement maneuver The movement signal

  this fast or slow ment appears on an input terminal 48 and the fast or slow maneuvering signal of the arrow arrives on an input terminal 50 The logic switching circuit has four AND gates 54, 56, 58, 60 each having two inputs The AND gate supplies a transistor supply circuit, while the gates 54, 56, 58 supply a voltage switching circuit 61 of the LF 13202 type The inputs of the AND gates 54, 56, 58, 60 are connected to the terminals 48, 50 o appear voltage signals of the modes, with intercalation in certain connections, as shown in FIG. 2, of inverters 52 of the HM 74 C 04 type for inversion

logic of received signals.

  The outputs of AND gates 54, 56, 58, 60, in pa-s t

  at the high level, select the appropriate output voltage range

  requested by amplification and switching lines 63-62; 64-62 -62 and 66, which deliver a voltage level to the operating or manual control member via terminal 74 and receive from this member, on terminal 75, an input voltage of 8.2 V Le output signal from gate ET 60 undergoes a logic inversion by

  the inverter 67, of the EIM 74 C 04 type, and is sent to a supply circuit

  mentation comprising a 12V source 68, a resistor 69 of 24 kn, a resistor 70 of 10 ki) a diode 71 of the IN 914 type and a

  switching transistor 72 of the GE 52907 type.

  The switching arrangement of FIG. 2 operates as described below. The voltage range of the operating member is determined by the variables of the machine fixing the modes, of the jib and displacement maneuver in this example When the position of the arrow indicates that the slow modes must be used (because the inclination of the arrow is above the horizontal for example), the output of the gate ET 58 goes high and causes the connection of the line 64 at the output terminal 74 The input voltage of 8.2 V on terminal 75 is applied through a 6.2 kfl series resistor from line 64 and the

  voltage level is applied to the operating device via terminal 74.

  The operation of the lever of this member from a starting point produces an incremented analog voltage signal. This analog signal is applied to the input terminal 5 of FIG. 1A and a

  DCB control signal is produced as described in the above.

  Similarly, if fast modes are to be used, because the arrow is pointing down for example, the output of AND gate 60 goes high and its output signal, inverted by 67 and applied to transistor 72, has the effect that the latter connects the voltage source 68 of 12 V to the operating member to

  through output terminal 74 This results in the displacement

  ment of the lever of the operating member following the same circular arc produces, incrementally, an analog voltage whose maximum value is 12 V and which is converted by the circuits of FIGS. LA and 1 B into a DCB signal, as described in the above. The device shown in Figure 2 constitutes an assembly

  voltage generator which includes a reference voltage source

  rence 68, a voltage divider circuit 61 capable of dividing the voltage supplied by the source 68 into a number of different output voltages and a logic circuit 52, 54, 56, 58, 60 for applying the selected output voltage to the generator analog signal. In FIG. 3, P denotes the inlet pressure of the fluid

  hydraulic valve 76 with variable flow, at inlet port 78.

  The valve has an outlet port 80 through which pressure fluid of a regulated flow rate is sent to a directional distributor, which directs the oil to the boom lifting cylinder in this example The valve 76 has a third port 82 which constitutes a bypass or return port to the tank and through which the excess hydraulic oil according to the control signal

  applies to the valve is returned to the tank.

  The valve 76 shown in FIG. 3 has four valves in the form of cartridges 84, 86, 88, 90 of a type which exists on the market. They are mounted in parallel and they

  can be opened individually by excitation

  noide that they contain by the digital control signal. When the operating device sends no control signal

  at valve 76, none of the four valves are open.

  popes 84, 86, 88 and 90 for the establishment according to the invention of a flow rate adjustable in increments are dimensioned, with regard to the flow passage of the fluid, ma nire prset of the flows corresponding respectively to 1, 2 , 4 and 8 liters per minute, for example, according to the figures of the code DCB 8421 The flow of fluid entering through the orifice 78 is detected by a pressure-flow compensator 92 forming part of the valve This compensator is intended to detect the pressure at the outlet 80 and the pressure that builds up in the oil circulation From the inlet 78 The compensator 92 opens to the extent necessary to return oil through the bypass port 82 to the tank to prevent in particular that the pump runs empty when all the valves 84, 86, 88 and 90 are closed 94 designates a safety valve sensitive to a maximum pressure of the system and capable of sending all the pump flow through port 82

  to the tank when this pressure is reached.

  An example of operation of the system will be described below.

  after with reference to the drawings It is assumed that the arrow or the

  arm of a machine carrying a nacelle at the end is pointed upwards.

  This situation is detected by a sensor, which is combined with logic elements which indicate that the machine should be used

  according to the slow modes for the operation of the boom and for the

  placement The signals applied to the input terminals 48, 50 are therefore low, which causes the output of the AND gate 58 to go high. The voltage of 8.2 V on terminal 75 is applied to

  through the resistance of 6.2 kf There the actuator (not shown -

felt) through terminal 74.

  It is assumed that the operating member comprises a lever, controlling the elevation of the arrow, which is displaceable in an arc and is coupled to a potentiometer The analog output signal of this potentiometer is a voltage whose amplitude varies between OV and ne maximum voltage which corresponds to the voltage applied to terminal 74, according to the position occupied by the lever When, by the position of its lever, the actuator sends an analog signal of 7 V for example at input terminal 5 for analog to digital converter circuits in figure l A, line N of CAN 4 goes high and the NAND gates and control circuits in figure 1 B convert this signal to a DCB signal 0111, which is applied across the output terminals 40,

  42, 44 and 46 to the variable flow valve 76 of FIG. 3.

  When no control signal is sent to the valve 76 of FIG. 3, its four valves 84, 86, 88 and 90 are closed and a positive displacement pump delivers a fixed flow rate, of 15 l per minute for example, at l orifice 78 of the valve The four valves of the latter are dimensioned respectively to have

  flow rates of 1, 2, 4 and 8 liters per minute, according to DCB code 8421.

  When the operator brings the control lever to a first position, a decimal control signal binary code 1000 is produced, which opens the valve 94, while the valves 86, 88 and 90 remain closed. A liter of hydraulic fluid is then sent through the outlet port 80 in the controlled supply piping (from the boom lifting cylinder), while 14 liters per minute

  of fluid are returned through the orifice 82 to the tank of the installation

  hydraulic lation under the action of the pressure-flow compensator 92.

  When the operator moves the lever to a second position, the control signal produced causes the valve 84 to close

  and the opening of the valve 86, corresponding to a supply flow

  tation of the lifting cylinder 2 liters per minute In this example, the control signal 0111 opens the valves 86, 88 and 90, with the consequence that 14 liters of fluid per minute are sent through the outlet port 80 to the cylinder lifting, while 1 liter of

  fluid per minute returns to the reservoir.

  Valve 76 therefore converts the DCB control signal to liters per minute of hydraulic fluid or to any other hydraulic fluid unit Four cartridge valves

  are used in the example which has just been described, to correspond

  to lay out the code DCB 8421, but it is obvious that one can use a greater number of valves to obtain a greater number of successive degrees therefore a finer control until the limit of the indicated code or another code and up to the limit of the pumping system The flow rates of the valves can also be staggered differently, in particular according to specific applications The numerically controlled valves used according to the invention eliminate

  the need for expensive analog control valves which are related

  mechanically complex and sensitive to operating conditions

  which may disrupt their functioning In addition,

  a numerically controlled valve like that used according to the invention

  tion allows easy and quick replacement of the various valves it contains if necessary in the event of malfunctions or malfunctions, which increases flexibility of use

  of the system and reduces downtime.

  The invention is therefore in no way limited to the embodiment described and the person skilled in the art can bring to it various

  other modifications without departing from its scope.

11.

Claims (4)

R E V E N D I C A T ION S   1 Electro-hydraulic control system comprising a jack or other motor driven by a pressure fluid, a source of fluid for delivering pressure fluid to the jack, a valve (76) or a similar device with electrical control for regulating the flow of the fluid between the source and the actuator and an operating member for electrically controlling the operation of the valve, characterized in that the operating member comprises a variable analog signal generator and an analog-digital converter circuit (2, 4), whose input (5) is electrically connected to the generator   analog signal, and in that the valve (76) has supports   popes (84, 86, 88, 90) numerically controlled to adjust the flow rate of the valve incrementally, which are electrically controlled   by the analog-digital converter circuit (2, 4).   2 System according to claim 1 o each of the valves   (84, 86, 88, 90) has a fluid flow passage of dimension particular information.   3 System according to claim 1 or 2 o the valve (76) has a bypass opening (82) for the return to the tank   excess hydraulic fluid.   4 System according to claim 1 o the operating member   is combined with a voltage generator circuit.   A system according to claim 4, the voltage generator circuit of which comprises a reference voltage source (68), a voltage divider circuit (61) which divides the voltage of the reference voltage source into a number of voltages. different outputs, as well as a logic circuit (52, 54, 56, 58, 60) for applying one of the output voltages to the analog signal generator. 6 System according to claim 5 o the selected output voltage is applied to an analog signal generator consisting of a potentiometer.