DE4414209A1 - Hydraulic control of simple tilting cylinder - Google Patents

Abstract

The hydraulic system operates a simple tilting cylinder (25,26). In its middle position, the proportional path value (10) provides a connection from the constant pump (29) to the pressure medium supply tank (30). A control signal at the proportional path value switches off when maximum pressure is reached. A control supply line (50) from the inlet control unit (52) to the proportional path value is relieved via a switch-off value (55) when maximum pressure is reached. Maximum pressure is sensed via an electrical pressure switch (56,57) and relayed to the control signal.

Description

The invention is based on a hydraulic system for actuation a single-acting tipper cylinder that has the features from the preamble of claim 1.

Such a hydraulic system is known from DE 39 00 887 A1 known. The hydraulic system shown in this document is built as a so-called Open Center LS system. It includes a constant pump and a 3-way pressure compensator, which fall independently via a metering orifice of the proportional directional valve the load pressure and the drive speed of the constant pump keeps constant. The oil flow flowing to the tipper cylinder is like this with only one function of the opening cross-section or the piston hubs of the proportional directional valve. The respective remaining amount of Pump delivery rate is diverted to the tank via the pressure compensator, whereby the pump pressure decreases via the pressure compensator.

The pressure compensator is in the opening direction from the pump pressure and in Closing direction of a compression spring and of a load load pressure applied to the signaling line. To when lifting of the tipper, i.e. the load when the tipper cylinder is extended pressure cannot rise above a maximum pressure the load signal line via a maximum pressure shut-off valve that the load pressure acts, are relieved to the tank. The pressure The scale then opens and the constant pump delivers in the unpressurized state Circulation. The load is then supported by a load holding valve.

The invention has for its object a hydraulic System that operates a single-acting tipper cylinder that serves and that the characteristics from the generic term of the An saying 1 has to develop so that it is special is inexpensive.  

This object is achieved by a hydraulic System that fulfills the characteristics from the generic term of the An claim 1 has and in accordance with the characterizing part of Claim 1 in the middle position of the proportional directional valve via this a connection from the constant pump to the tank stands and a control signal attached to the proportional directional control valve nal can be switched off when the maximum pressure is reached. Consequently there is no pressure circulation of the pump delivery flow when Errei the maximum pressure does not have an addition to the proportion tional directional valve, but via the proportion tional directional valve itself. If with such a proportional Actuate the directional control valve of the control piston from the middle position is opened, the Ver opens after a certain distance connection from the pump to the consumer via fine control grooves, while the circulation is throttled using fine control grooves. About if the pump pressure increases the consumer pressure, the pressure begins liquid to flow through the valve to the consumer. With white When the control piston is switched on, the pump volume electricity increasingly from the circulation channel to the consumer channel controls. After closing the circulation channel, the whole flows Pump volume flow to the consumer. One for the throttle control of a hydraulic consumer Propor tional directional control valve, the piston stroke is divided into three phases on. The first phase is the connection from the pump to the Consumer still closed. The second phase corresponds to one Fine control area in which a consumer is sensitive can be controlled. The last phase is the remaining stroke with locked circulation channel.

Advantageous embodiments of a hydraulic system according to the invention systems can be found in the subclaims.

Thus, according to claim 2, the control signal is switched off in advantageously in that one from the pilot unit to Proportional directional control valve leading control line when reached the maximum pressure through a maximum pressure shut-off valve is resilient.  

According to claim 3, the maximum pressure of one elec is preferred trical pressure switch detectable and the control signal is elec can be switched off trically. The effort then appears less than with an application of a shut-off valve directly with the Load pressure.

According to claim 4 can for two tipper cylinders, one of which Example of a tipper on a truck and truck the other is assigned to a truck trailer, two facilities designed to measure two different maximum pressures hen, one for one tipper cylinder and one is specified for the other tipper cylinder. On-off valve can be in a first switch position, in which a tipper cylinder the, and brought into a second switch position, in the the other tipper cylinder via the proportional directional valve can be actuated. Depending on the position of the switch valve the control signal is switched off depending speed of the state of the one pressure detection device or the other pressure detection device.

Preferably, together with the switching valve, is an electrical one Switch switchable, depending on its position from one or the other from two to different Maximum pressure set pressure switches an output signal is dispensable. In principle, it is not necessary for the elec trical output of the pressure switch, which to the higher maximum pressure is set, via which changeover with the switching valve leads electrical switch and the possibility of a Sig This pressure switch gives the electrical switch being affected. Only the electrical pressure switch for the lower maximum pressure must be switched off. Favorably he however, there appears to be a complete separation of the two pressure scarves ter such that in the one switching position of the electric scarf switchable together with the switching valve ters only over the one pressure switch and in the other switching an electric position only via the other pressure switch Circuit can be closed.  

According to claim 6, the one electrical pressure switch is hydraulic with one consumer branch line and the other electrical trical pressure switch with the other consumer branch line connected so that the pressure switch is not from one between the Proportional directional valve and the switching valve prevailing and possibly deviating from the pressures on the tipper cylinders Pressure can be affected.

The training according to claim 7 offers the possibility of both electrical pressure switches on the motor vehicle hydraulically on to connect the consumer line.

For a tipper cylinder is usually a so-called End position shut-off valve provided. Through such a valve either in a so-called one-pipe system that becomes a kip per cylinder leading consumer line easily lockable or in a so-called two-pipe system with one back to the tank leading line connectable. Especially in the former case it is favorable if the device for recording the for the Kip per cylinder predetermined maximum pressure between the Proportio directional control valve and the end position shut-off valve to the consumption line is connected. In front of the limit switch namely, the pressure in the consumer line increases when it is blocked by the limit switch. The pressure detection device responds so that the proportional Directional control valve returns to its central position and the pump circulates without pressure.

Two embodiments of a hydraulic according to the invention Systems for operating a single-acting tipper cylinder are shown in the drawings. Based on the figures of this Drawings, the invention will now be explained in more detail.  

Show it

Fig. 1, the first embodiment with two electrical pressure switches as a pressure sensing devices, each of which is connected to a tung extending between a valve and a dump truck cylinder consumer Two sliding,

Fig. 2 shows the second embodiment also with two electrical pressure switches, both of which are connected to the common consumer line between the proportional directional valve and the changeover valve, and

Fig. 3 is a longitudinal sectional view of the proportional directional control valve of Figs. 1 and 2.

The proportional directional control valve 10 according to FIG. 3 has a valve housing 11 , which receives a control piston 13 in a continuous piston bore 12 . In the valve housing 11 run a tank channel 14 , a pump channel 15 in which there is a load-holding check valve 16 , and two consumer channels 17 and 18 . The tank channel 14 and the pump channel 15 are branched and are connected to two control chambers of the piston bore 12 . Between a control chamber connected to the tank channel and a control chamber connected to the pump channel, a control chamber belonging to a consumer connection is arranged. The tank channel 14 is connected to a tank connection T, the pump channel 15 with a pump connection P, the consumer channel 17 with a consumer connection A and the consumer channel 18 with a consumer connection B of the valve housing 11 .

Axially in the middle, the piston bore 12 has three further control chambers 19 , 20 and 21 , the central control chamber 19 being connected to the tank connection T and the two outer control chambers 20 and 21 being connected to the pump connection P. The connection between the control chambers 20 and 21 and the pump connection P is made internally in the valve housing 11 . The connection between the control chamber 19 and the tank connection T takes place in a screwed to the valve housing 11 Endplat te 22 , which is shown schematically in FIGS . 1 and 2 and which also has a tank connection T.

The control piston 13 is provided with a total of four ring grooves and cut with fine control grooves in the adjacent to the ring grooves Kolbenab. The annular grooves are arranged and so large that the three control chambers 19 , 20 and 21 are connected to one another in the central position of the control piston 13 shown. The consumer channels 17 and 18 are blocked off from both the pump channel 15 and the tank channel 14 . In the middle position shown in Fig. 3 there is thus a direct connection between the pump connection and the tank connection of the valve. A pump flow can therefore be pumped through the valve without pressure in circulation. If the control piston 13 is moved out of the middle position to the side, then the consumer channels 17 and 18 continue to be blocked off to about 35% of the total possible piston stroke. Then about 45% of the piston stroke is followed by a fine control range in which the connection from the pump channel to a consumer channel via fine control grooves is continuously opened, while the connection between the control chamber 20 or 21 and the control chamber 19 , i.e. the connection between the pump connection P and the tank connection T of the valve is throttled via fine control grooves. Due to the throttling of the circulation, the pressure in the pump channel rises. If this pressure finally exceeds the consumer pressure, hydraulic fluid begins to flow to the consumer via the check valve 16 . As the control piston is moved further, the pump volume flow is increasingly reversed from the circulation to the consumer channel. On the remaining 20% of the possible piston stroke, the control chamber 19 is separated from the control chamber 20 or 21 .

Referring to FIGS. 1 and 2, a proportional directional control valve 10, including an end plate 22 in a hydraulic system for operating one or, as is the case in the embodiments, when using two single-acting the tipper cylinders 25 and 26 on a truck Motor car 27 or on a truck trailer 28 connected to the pump port P of the proportional directional valve 10 with its pressure side, a constant pump 29 , which can suck oil from a tank 30 and deliver it into a pressure line 31 . The tank connection T of the end plate 22 is connected to the tank 30 via a tank line 32 . The consumer connection B is also connected to the tank line 32 . From the consumer connection A, a consumer line 33 leads to the input of a 3/2-way switching valve 34 , which can be switched manually between two latched switching positions. From each of the two outputs of the switching valve 34 , a consumer branch line 35 and 36 leads to the tipper cylinder 25 and 26, respectively.

In the consumer line 36 there is an end position switch-off valve 40 which is designed as a 2/2-way valve and the Verbraucherlei tung in a position determined by a spring rest position leaves 36 are open and the consumer cherleitung in an actuated position 36 shuts off. In the bypass to the valve 40 , a return check valve 41 is arranged, which blocks the tipper cylinder 26 , which is mounted on the trailer 28 .

Also in the consumer branch line 35 is an end position shut-off valve, which is provided with the reference number 42 and is designed as a 3/2-way valve. In a rest position of the valve 42 determined by a compression spring 43 , the consumer branch line 35 to the tipper cylinder 25 on the truck motor vehicle 27 is open. In the other switching position, valve 42 connects consumer branch line 35 to tank line 32 . A check valve 44 integrated in the valve 42 then supports the load. In the second switching position, the valve 42 can be brought with the aid of a plunger 45 , which is actuated in a predetermined end position of the tipper on the motor vehicle 27 and acts via a compression spring 46 on the control piston, not shown, of the valve 42 .

Because to the end position shut-off valve 42 arranged in the vicinity of the tipper cylinder 25 lead a consumer line and a tank line, the hydraulic subsystem for actuating the tipper cylinder 25 is also referred to as a two-pipe system. In contrast, only one consumer line leads to the end position shut-off valve 40 arranged in the vicinity of the tipper cylinder 26 . The corresponding subsystem is therefore called a single-pipe system.

The proportional directional valve 10 has two control inputs a and b, which are connected via two control lines 50 and 51 to a pneumatic pilot control unit 52 . The valve 10 can thus be actuated pneumatically. The output of the pilot device 52 , to which the control line 51 is connected and which is pressurized to lower a tipper, is also connected via a control line 53 to a control input of the limit switch valve 42 , which via the control line 53 in the sense of a reset in its rest position, in which the consumer branch line 35 to the tipper cylinder 25 is open, can be pressurized.

The control line 50 can be relieved to the atmosphere by means of an attached to the housing 11 of the proportional directional control valve 10 by an Elektromag neten 54 operable pneumatic maximum pressure shut-off valve 55 . If the magnet is switched off, the connection to the atmosphere is blocked. The electric magnet 54 receives a control signal via an electrical pressure switch 56 or an electrical pressure switch 57 . The pressure switch 56 responds to a higher maximum pressure than the pressure switch 57 .

In the embodiment of Fig. 1, both pressure switches 56 and 57 are connected to an electrical input connected to a voltage source. The pressure switch 57 is hydraulically connected to the consumer branch line 36 and the pressure switch 56 is connected to the consumer line 35 . A 3-pole electrical switch 58 can be actuated together with the valve 34 and, depending on the position of the valve 34, connects the electrical output of only the pressure switch 56 or the electrical output of only the pressure switch 57 with the solenoid 54 of the maximum pressure shut-off valve 55 , depending on whether the consumer line 33 is connected to the consumer branch line 35 or the consumer branch line 36 .

In the embodiment according to FIG. 2, both pressure switches 56 and 57 are hydraulically connected to the consumer line 33 . The two electrical outputs of the pressure switches 56 and 57 are permanently connected to the electromagnet 54 together. Depending on the position of the valve 34 , the electrical changeover switch 58 connects either the electrical input of the pressure switch 56 or of the pressure switch 57 to a voltage source.

To extend the tipper cylinder 25 , the valve 34 assumes the state shown in FIGS . 1 and 2. The pilot device 52 is actuated so that the control connection a of the proportional directional valve 10 is acted upon by a pneumatic pressure, so that the pressure rises in the consumer line 33 and in the consumer branch line 35 , until finally the tipper cylinder 25 is extended. The pressure in the consumer branch line 35 rises for some reason, e.g. B. because the tipper hits an obstacle, so far that the maximum pressure set at the pressure switch 56 is reached, this pressure switch closes a circuit for the electromagnet 54th The valve 55 switches over so that the control line 50 is relieved and the proportional directional control valve 10 returns to its central position. In this position of the proportional directional control valve 10 , this supports the load. The pump flow flows unpressurized in circulation through the proportional directional valve back to the tank. If the tipper cylinder is extended 25 without a response of the pressure switch 56 to its end position, so the final lay-off valve 42 is switched so as to flow back of the proportional directional valve 10, the pump delivery now flow through the shut-off valve 42 to the tank while maintaining the position . In order to retract the tipper cylinder 25 , the control input b of the proportional directional valve 10 is subjected to a control pressure. Via the control line 53 , the shut-off valve 42 is acted upon with a control pressure and is returned to its rest position against the force of the spring 46 . Now pressure medium can be displaced from the tipper cylinder 25 via the proportional Wegeven valve 10 to the tank.

To extend the tipper cylinder on the trailer 28 , the valve 34 is brought into its other switching position. If the pressure in the consumer branch line 36 exceeds the set maximum pressure when the cylinder 26 is extended, the pressure switch 57 responds and the electromagnet 54 actuates the valve 55 . When the tipper cylinder 26 reaches its end position, the valve 40 shuts off the consumer branch line 36 . The pressure in this increases to the maximum pressure, so that the pressure switch 57 speaks to, the valve 55 is actuated, the control input a of the proportional directional control valve 10 is relieved of the control pressure and the proportional directional control valve 10 returns to its central position. Just as with the two-pipe system for the motor vehicle 27 , the pump delivery flow also flows to the tank without pressure when the one-pipe system for the trailer 28 is reached. To retract the tipper cylinder 26 , the proportional directional valve 10 is pressurized in the opposite direction from the control input b, so that pressure medium from the tipper cylinder 26 is displaced via the check valve 41 and the proportional directional valve 10 to the tank. The pump flow flows when lowering a tipper via the consumer port B of the proportional directional valve 10 without pressure to the tank.

In the embodiment of FIG. 2 during the extension of Kip be perzylinders 26 both pressure switches 56 and 57 be on the load pressure aufschlagt. However, this has no effect on the maximum pressure protection because, depending on the position of the changeover valve 34 and thus the electrical switch 58, only one or the other pressure switch can connect the electromagnet 54 to the voltage source.

Both pressure switches 56 and 57 are advantageously arranged on the motor vehicle 27 . The electrical wiring is then less expensive than if the one pressure switch is arranged on the trailer 28 .

Claims (9)

1. Hydraulic system for actuating a single-acting tipper cylinder ( 25 , 26 ) with a constant pump ( 29 ) from the pressure medium from a tank ( 10 ) can be sucked in, with a proportional directional valve ( 10 ), which is used to raise and lower the tipper Via a pilot device ( 52 ) from a spring-centered position, in which a consumer line ( 33 , 35 , 36 ) leading from the proportional directional valve ( 10 ) to the tipper cylinder ( 25 , 26 ) is blocked, adjustable in opposite directions, and with a pressure cut-off for switching the pump volume flow to pressureless circulation when a maximum pressure in the consumer line ( 33 , 35 , 36 ) is reached, characterized in that in the middle position of the proportional directional valve ( 10 ) a connection from the constant pump ( 29 ) to the tank ( 30 ) and that a proportional signal valve ( 10 ) applied control signal can be switched off when the maximum pressure is reached . 2. Hydraulic system according to claim 1, characterized in that one of the pilot control ( 52 ) to the proportional Wegeven valve ( 10 ) leading control line ( 50 ) when the maximum pressure is released by a maximum pressure shut-off valve ( 55 ) can be relieved. 3. Hydraulic system according to claim 1 or 2, characterized in that the maximum pressure of an electrical pressure switch ( 56 , 57 ) can be detected and the control signal is electrically switchable. 4. Hydraulic system according to a preceding claim, characterized in that depending on the position of a switching valve ( 34 ) one or the other of two Kip perzylindern ( 25 , 26 ) individually via one of the switching valve ( 34 ) to the respective tipper cylinder ( 25th , 26 ) leading consumer branch line ( 35 , 36 ) can be actuated by actuating the proportional directional valve ( 10 ) such that at least two devices ( 56 , 57 ) are available for detecting two different maximum pressures, one of which is for one tipper cylinder ( 25 ) and one for the other tilting cylinder ( 26 ) is specified, and that depending on the position of the switching valve ( 34 ) from the control signal depending on the state of one pressure detection device ( 56 ) or the other printer detection device ( 57 ). 5. Hydraulic system according to claim 4, characterized in that together with the switching valve ( 34 ) an electrical switch ( 58 ) is switchable, depending on the position of one or the other from two to different maximum pressures set under different electrical Druckschal tern ( 56 , 57 ) an output signal can be output. 6. Hydraulic system according to claim 5, characterized in that the one electrical pressure switch ( 56 , 57 ) hydraulically with one consumer branch line ( 35 , 36 ) and the other electrical pressure switch ( 57 , 56 ) hydraulically with the other consumer branch line ( 36 , 35 ) is connected. 7. Hydraulic system according to claim 5, characterized in that the two electrical pressure switches ( 56 , 57 ) between the proportional directional valve ( 10 ) and the switching valve ( 34 ) are connected to the consumer line ( 33 ) and that depending on the Position of the electrical switch ( 58 ) only one or only the other of the two pressure switches ( 56 , 57 ) is connected to a voltage source (UB). 8. Hydraulic system according to one of the preceding claims, characterized in that a consumer line ( 35 , 36 ) leading to a tipper cylinder ( 25 , 26 ) can be shut off by a limit switch ( 40 , 42 ) and in that a device ( 56 , 57 ) for detecting the tipper cylinder ( 25 , 26 ) before the given maximum pressure between the proportional directional valve ( 10 ) and the limit switch ( 40 , 42 ) to the consumer line ( 35 , 36 ) is connected. 9. Hydraulic system according to one of the preceding claims, characterized in that the proportional directional control valve ( 10 ) can be controlled pneumatically via a first control line ( 50 ) for lifting the tipper and via a second control line ( 51 ) for lowering the tipper that a maximum pressure by an elec trical pressure switch ( 56 , 57 ) can be detected that the first control line ( 50 ) by a solenoid ( 54 ) operable maximum pressure shut-off valve ( 55 ) can be relieved to the atmosphere and that the electromagnet ( 54 ) via the electrical Pressure switch ( 56 , 57 ) can be connected to voltage.