DE3347000A1 - Electrohydraulic arrangement for controlling a double-acting hydraulic motor - Google Patents

Abstract

An electrohydraulic arrangement (10) for controlling a double-acting hydraulic motor (11) is proposed, the two sides (14, 15) of which hydraulic motor (11) can be activated independently of one another in each case via an electrohydraulically actuated 3-way continuous valve (16, 17) in spool type of construction. The continuous valves (16, 17) are designed as position-controlled built-in valves and are each activated by a 4/4 proportional pilot valve (43, 63) with safety position (46, 46'). The pilot valves (43, 63) are connected via separate electrical channels (68, 69) to an electronic control unit (33) which works out control variables in accordance with the respective drive task at the hydraulic motor (11) according to programmed control instructions. With a minimum of electromechanical transducers (53, 53', 61) and valves (16, 17) dependent upon nominal size, a multiplicity of additional functions such as differential connection, fail-safe function, power limiting, cavitation avoidance or mass-load braking can be realised. <IMAGE>

Description

Electro-hydraulic device for controlling a

double-acting hydraulic motor prior art The invention works from an electro-hydraulic device according to the preamble of the main claim. Such a device is already known from DE-OS 28 49 653, in which the Direction and speed of a double-acting hydraulic motor under the influence alternating load directions of an external load controlled with the help of 2-way valves will. While designed as seat valves for the volume flow control, through 473 servo valves are used for pilot operated 2-way throttle valves the directional control a total of four 2-way seat valve cartridges. A disadvantage with this facility is the high valve expense, as all of these valves, as well as additional Check valves for a differential circuit, to the required nominal size need to be coordinated. In addition, one is for the control side of the cartridge valves A large number of hydraulic components are required.

Furthermore, from DE-OS 30 11 o88 a hydraulic device for Control of a double-acting promoter known where the Pressure medium supply to both connections of the hydraulic motor from a 3-way slide valve is controlled, while the pressure medium discharge is controlled by two individual 2-way cartridge valves is controlled in poppet valve design. It is not only the assignment that is disadvantageous here of the 3-way slide valve to both motor connections, which increases the degree of freedom are limited in the control device, but also the fully hydraulic control of the individual built-in valves without any position control. Again, there are check valves Required in nominal size for an additional function, which increases the construction costs will.

Furthermore there is oil hydraulics and pneumatics from the magazine "o + p" 26 (1982) No. 9, page 640, Figure 5 an electro-hydraulic device for control a double-acting hydraulic motor known that executed in proportional technology and has individual hydraulic resistances. Here, too, are the individual resistances designed as 2/2 seat cartridge valves and for proportional control of volume flow and pressure two electromechanical transducers are provided.

The disadvantage of this device is that here, too, the effort for size-dependent valves is relatively large and, accordingly, so is the control circuit extensive valve means are required.

Furthermore, from DE-AS 23 57 274 an electrohydraulic device for controlling a double-acting injection cylinder of an injection molding machine known in which an electronic control unit depending on a variety of Process variables controls the screw drive. A disadvantage with this facility is that only 2-way valves are used here and a differential circuit is not provided.

Advantages of the Invention The electrohydraulic device according to the invention with the characterizing features of the main claim has the advantage over this that they have a proportional control of volume flows and pressures at as possible low cost of valves in proportional technology.

So comes the facility in terms of the functions it can perform with relatively few electromechanical converters and with few nominal size-dependent converters Valves off. Furthermore, additional requirements can easily be met by that the electrical control unit is programmed accordingly. So in particular additional requirements such as differential switching due to the low expenditure in the electronic control unit, Fail-safe function, force limitation or avoidance of negative pressure can be fulfilled.

In addition, this control device can be manufactured with affordable manufacturing costs Reach critical control edge overlaps in the main valves, which also include a allow good fail-safe behavior.

The measures listed in the subclaims are advantageous Further training and improvements of the facility specified in the main claim possible. It is particularly advantageous to use this device for the control of the lock cylinder in an injection molding machine.

Drawing An embodiment of the invention is shown in the drawing shown and explained in more detail in the following description. It show figure J an electro-hydraulic device for controlling a double-acting hydraulic motor in a schematic representation and FIG. 2 a partial Longitudinal section by means of a 3-way proportional valve with attached proportional pilot valve in a simplified Depiction.

Description of the exemplary embodiment FIG. 1 shows an electrohydraulic one Device 10 for controlling a double-acting hydraulic motor 11 on its piston rod 12 can attack an external load 13 with changing load directions. A cylinder space of the hydraulic motor 11 is a first motor connection 14 and an annular space is a second Motor connection 15 assigned.

To control the pressure medium inflow and outflow to the hydraulic motor 11 are the first motor connection 14 a first 3-way proportional valve 16 and the second motor connection 15 is assigned a structurally identical, second 3-way continuous valve 17 in a corresponding manner. Since the 3-way continuous valves 16, 17 are designed in the same way, in following only on the first proportional valve 16 discussed in more detail, wherein. same components on the second 3-way continuous valve 17 with the same reference symbols, but with the Index. Furthermore, the 3-way continuous valve 16 is explained at the same time reference is also made to FIG.

The 3-way continuous valve 16 is a hydraulically piloted and position-regulated Slide valve designed in cartridge design. As Figure 2 shows in more detail, this has Continuous valve 16 has a housing 18 with a slide sleeve fixed to the housing 19, in which a hollow longitudinal slide 21 is tightly and slidably guided is. An inlet connection P is with 22, a return connection R with 23 and a consumer connection A is denoted by 24. The longitudinal slide 21 is made by a spring 25 loaded in the direction of a starting position 26 in which the consumer connection 24 to the return port 23 is relieved, while the inlet port 22 is blocked will. From the pressure in a control connection 27, the longitudinal slide 21 can counter to the The force of the spring 25 is brought into a switching position 28 beyond a zero position in which the inlet connection P is connected to the consumer connection A. and the return port R are blocked.

As can be seen in more detail from FIG. 2, the longitudinal slide 21 a zero position shown in FIG. 2 between the two positions 26 and 28 in which the two control edges 29 of the longitudinal slide 21 are closed and so that the consumer connection A is blocked. The position of the longitudinal slide 21 is picked up by an electromechanical displacement transducer 31, which transmits its signals an electrical line 32 forwards to an electronic control unit 33, the The signals from the displacement transducer 31 'are also fed to the second 3-way continuous valve 17 will.

The consumer connection 24 of the first 3-way continuous valve 16 has over a hydraulic line 34 with the first motor port 14 connection, while a second line 35 the corresponding connection to the second motor connection 15 manufactures. The inlet connections 22, 22 'of the two continuous valves 16, 17 are above one another parallel feed lines 36, 37 connected to a common pump 38. the Return connections 23, 23T are relieved via return lines 39, 41 to the tank 42.

The control connection 27 on the first 3-way continuous valve 16 is of a first proportional pilot valve 43 is activated.

This pilot valve 43 is designed as a 4-way 4-position valve and flanged directly to the housing 18, as FIG. 2 shows in more detail. His control slide 44 is held by a spring 45 in a safety position 46 in which a first motor connection 47 with a second motor connection 48 and at the same time via a Throttle point 49 is connected to an inlet connection 51; at the same time is the Drain connection 52 blocked. The spool 44 is by a proportional solenoid 53 against the force of the spring 45 successively in a first (54), second (55) and third working position 56 deflectable. While in the first working position 54 of the Inlet connection 51 has connection only with the first motor connection 47, and the two other connections 52 and 48 are blocked, are in the second working position 55 all connections 47, 48, 51, 52 blocked. In the third working position 56, only the first motor connection 47 is relieved to the drain connection 52, while connections 51 and 48 are blocked. During the inlet connection 51 and the outlet connection 52 is connected to the supply line 36 and the return line 39 via control lines are, has the first motor connection 4t via a control line 57 to the control connection 27 of the first proportional valve 16 connection. From the second motor connection 48 one leads Drain line 58 to tank 42, into which a proportional pressure control valve 59 is connected is, whose proportional magnet 61 is controlled by the electronic control unit 33 will. The proportional magnet 53 of the pilot valve 43 is position-regulated, which is why the position of its armature is detected by an electromechanical displacement transducer 62. The proportional solenoid 53 of the first pilot valve 43 is also from the electronic Control unit 33 activated.

The second, which is provided for controlling the second 3-way continuous valve 17 Proportional pilot valve 63 is essentially identical in construction to the first pilot valve 43 and differs from it only in that it has a different control slide 60 with a partially changed circuit symbol. Otherwise the components are the same of the second pilot valve 63 with the same reference numerals as in the first pilot valve provided, but with the index '. Both motor connections are in the safety position 46 ' 47 ', 48' are connected to one another and to the outlet connection 52 ', while the inlet connection 51 'is blocked. In the first (54 ') and in the third working position 56' are the switching connections in comparison to the first pilot valve 43 are merely exchanged, so that in the first working position 54 'the first motor connection 47' to the drain connection 52 'has connection, while in the third working position 56' the first motor connection 47 'is connected to the inlet connection 51'. Otherwise the proportional solenoid is used 53 ′, in turn, position-regulated and activated by the electronic control unit 33.

The position of the piston rod 12 of the hydraulic motor 11 is controlled by a electromechanical Wegaufnahmver 64 monitors whose electrical output signals -demlektronic control unit 33 are supplied. In addition, the electronic one is available Control unit 33 in connection with a function generator 65 serving as a setpoint generator.

Furthermore, the motor connections 14, 15 are each a pressure sensor 66 and 67, the signals of which are fed to the electronic control unit 33.

The function of the device J0 is explained as follows: at In the present control device 10, each motor connection 14, 15 of the hydraulic cylinder 11 can be controlled separately from the 3-way continuous valves 16, 17 and in a targeted manner. The electronic control unit 33 works as a programmable controller, the according to the measured values entered for it with regard to pressures and volume flows works according to a control algorithm tailored to the respective drive task and for this purpose has powerful, fast microcomputers. Accordingly the control unit 33 is via two independent electrical control lines 68, 69 control the two proportional pilot valves 43 and 63. Accordingly the two 3-way proportional valves 16 and 17 are actuated separately from each other.

In the continuous valves 16, 27 only two per valve Control edges on the control slide 21 and the slide sleeve 19 are assigned to one another. The synchronization between two pairs of control edges in each of the two continuous valves 16 or 17 can be adjusted electronically and therefore easily via the position control accomplished. The advantage here is that in the 3-way proportional valves 16, 17 the the control edges 29 forming holes in relation to the diameter of the longitudinal slide 21 are shorter and can therefore be produced more precisely and more cheaply.

The possibility of both motor connections 24, 25 of the hydraulic motor 11 separately controlled independently by electrical signals is from a control point of view advantageous in that this results in the electronic control unit 33 according to particularly powerful control algorithms can work. This is especially true if with pressure sensors 66 the pressure on both sides of the hydraulic cylinder 11 is determined and their electrical signals from the control unit 33 in subordinate Pressure control loops are processed with.

With the device 10, additional functions can be particularly inexpensive realize. A fail-safe behavior is achieved with the device 10, if in the event of failure of the electronic control unit 33, the proportional magnets 53, 53 'of both Pilot valves 43, 63 are no longer energized. Their spool 44, 44 ' then take their respective safety positions 46, 46 ', so that the longitudinal slide 21, 21 'in the continuous valves 16, 17 each assume their starting position 26, 26' can. The two motor connections 14, 15 of the hydraulic motor 11 thus become a tank 42 relieved. This is where there is a critical overlap of 4 control edges in the two 3-way proportional valves 16, 17 and passive failure behavior without additional effort not from.

Another frequently requested additional function is the differential circuit of the hydraulic cylinder 11, which can be electrically preselected with the device 10. At the Normal operation of the device 10 are the two 3-way proportional valves 16, 17 in their respective zero positions when the hydraulic motor 11 is at a standstill, and are from here through the electrical command signals of the electronic control unit 33 deflected in push-pull.

For the differential operation of the hydraulic cylinder 11 is only necessary the second continuous valve 17 into its switching position by a constant command signal 28 ', in which the working connection 24' is connected to the inlet connection 22 ' is and via the variable command signal via the first proportional valve 26 the pressure medium flow to the first motor connection 14 with regard to Modulate pressure and volume. For the differential operation of the hydraulic cylinder 11, in addition to the proportional valves 16, 17 no additional valves in nominal size required.

Another additional function is the power limit, as it is above all is required when the hydraulic cylinder 11 is used as a mold locking cylinder in injection molding machines is used. In these cases, pressure protection must be possible to avoid damage avoid the injection mold. To initiate such a form locking security the first proportional pilot valve 43 is brought into its safety position 46, and thus the control connection 27 of the first proportional valve 16 with the proportional pressure control valve 59 connected. This pressure control valve 59 has no effect on the fail-safe behavior of the first 3-way continuous valve 16, as long as it is not energized, because its pressure the force of the spring 25 does not predominate. The second 3-way proportional valve is also used 17 electrically brought into its starting position 26, in which the consumer connection 24 to the tank 42 is relieved. The proportional pressure control valve 59 takes place now a position control of the first continuous valve 16 continues. Since this continuous valve 16 can work at the same time as a pressure reducing valve, can also work through an electronic Limitation of the soil value of the position control supplied to the pressure control valve 59 the continuous valve 26 a pressure limit to the desired pressure level during the mold clamping function of the hydraulic cylinder 12 can be forced. A detailed description Such a pressure protection is known per se from DE-OS 31 40 397.

Another additional function in device 20 is protection against negative pressure, if e.g. as a result pulling load 13 when extending Piston rod 12 there is a risk of cavitation at the first motor connection 14. at it is now possible for the device 10 to use the one assigned to the first motor connection 14 larger effective area in the hydraulic cylinder 11 with a defined, low pressure with the help of the possible pressure reducing function through the first proportional valve 16 in connection to pressurize with the proportional pressure control valve 59.

At the same time, the control unit 33 controls via the second continuous valve 17 the flowing pressure medium flow from the second motor connection 15 so that through corresponding throttling of this pressure medium flow even with rapid braking of the pulling load 13 no cavitation occurs in the first motor connection 14.

In the present device 10 can also in an expedient manner Nominal size of the proportional valve 16, 17 to the different sized piston areas in the Hydraulic cylinder 11 are adapted. When using the device 10 in a Injection molding machine is also advantageous that on the injection side as on the same drive elements on the closing side, namely the proportional valves 16, 17 can be used.

Changes to the device 10 shown are of course possible possible without rejecting the idea of the invention. In particular, additional Pressure control loops for power control of the device 10 are used.

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Claims (10)

Claims El) 'Electro-hydraulic device for controlling a double-acting hydraulic motor according to direction and speed, whose pressure medium supply and outflow to both motor connections can be influenced by built-in valves that can be controlled independently of each other by a proportional pilot valve are and are each in a position control loop, its associated electronic Control unit is in operative connection with the solenoid of the pilot control valve, thereby characterized in that the proportionally operating built-in valves are each designed as a three-way continuous valve (16, 17) are formed and each have a longitudinal slide (21, 21 ') and that the consumer connections (24, 24 ') of the proportional valves (16, 17) each with a the motor connections (14, 15) and the inlet (22, 22 ') and return connections (23, 23 ') each parallel directly to a pressure medium supply (38) or a return (42) are connected. 2. Device according to claim 1, characterized in that the longitudinal slide (21, 21 ') of the continuous valves (16, 17) by a spring (25) loads an initial position (26, 26 '), in which they relieve the consumer connection (24) and from one Pressure in the control connection (27) can be deflected into a switching position (28) in which they connect the consumer connection (24) to the inlet connection (22). 3. Device according to claim 1 or 2, characterized in that the longitudinal slide (21, 21 ') have a central zero position in which the Consumer connection (24, 24 ') is hydraulically blocked, especially when it is critical Coverage of the control edges (29). 4. Device according to one or more of claims 1 to 3, characterized characterized in that each proportional pilot valve (43, 63) is one-sided by a spring (45) loaded control slide (44, 44 '), which by the spring is held in a safety position (46, 46 '). 5. Device according to one of claims 1 to 4, characterized in that that the hydraulic motor (11) is designed as a differential cylinder. 6. Device according to claim 5, characterized in that in the safety position (46) of the pilot valve (43) assigned to the cylinder side (14) is the pressure in Control connection (27) of the proportional valve (16) from a proportional pressure control valve (59) is adjustable. 7. Device according to one or more of claims 1 to 6, characterized characterized in that the device has an electronic control unit (33), at least with the displacement sensors (31, 31 ') of the continuous valves (16, 17) and the proportional magnets (53, 53 ') of the pilot valves (43, 63) is in operative connection and in particular has an operative connection with pressure sensors (66, 67) at the motor connections (14, 15). 8. Device according to claim 7, characterized in that the electronic Control unit (33) with the pressure control valve (59) and in particular a displacement transducer (64) is in operative connection with the hydraulic motor (11). 9. Device according to one of claims 1 to 8, characterized in that that the pressure control valve (59) is in the safety position (46) of the first pilot valve (43) with the first proportional valve (16) as a pressure reducer to limit the pressure in the first Motor connection (14) can work together. 10. Device according to one of claims 1 to 9, characterized by their use for controlling the lock cylinder in an injection molding machine.