DE102008024338A1 - Electro-pneumatic drive system, has electrically actuatable control valve devices designed different such that switching time of one of valve devices is longer than switching time of another one of valve devices - Google Patents

Abstract

The system (1) has electrically actuatable control valve devices (22, 23) designed different such that a switching time of the valve device (23) is longer than a switching time of the valve device (22) by simultaneously supplying electrical switching signals to the valve devices. The switching time of the valve device (23) elapses till switching into a counter-air ventilation position supplying brake pressure. The switching time of the valve device (22) elapses till switching into an air ventilation position supplying working pressure. An independent claim is also included for a method for operating an electro-pneumatic drive system.

Description

The The invention relates to an electro-pneumatic drive system, with at least one pneumatically actuable drive device, the output unit dividing two admission chambers comprising the two oppositely directed lifting movements can execute between two end positions, at least the one, first lifting movement can be caused by the fact that the one, first admission chamber with standing under a working pressure Compressed air is vented and delayed afterwards the other, second Beaufschlagungskammer with respect to the Working pressure lower brake pressure standing compressed air counter-ventilated becomes. The invention further relates to a method for operating such a drive system.

Such a drive system with associated operating method is from the DE 10 2005 060 530 A1 known. Measures are described here which make it possible to increase the travel speed of a pneumatically actuated output unit of a drive device designed as a linear drive. The output unit includes a piston which divides two Beaufschlagungsklammern from each other, which are acted upon in a controlled manner with compressed air. In one possible mode of operation, when the driven unit is retracted, the rear admission chamber is ventilated and, shortly thereafter, a counter ventilation of the front admission chamber is produced. Through this design, the movement times are to be shortened while ensuring effective cushioning. The counter ventilation is switched on either event-controlled or timed, that is to say, for example, when a certain position is reached or after a certain travel time of the output unit has elapsed. This type of control is relatively expensive and requires very accurate electronic control devices, because the time delay to obtain an optimal result should be as low as possible and therefore the required monitoring measures must be subject only to a very low tolerance.

The The object of the invention is low travel speeds of the Output unit of a pneumatically actuated drive device to enable.

These Task is in a drive system of the type mentioned solved that to control the ventilation the first Beaufschlagungskammer an electrically actuated first control valve device and for controlling the counter ventilation the second Beaufschlagungskammer an electrically actuated second control valve means is present, these two Control valve devices are designed differently so that from the simultaneous application of an electrical switching signal to both control valve devices until switching to a the brake pressure supplying counter ventilation position passing Changeover duration of the second control valve device longer is as the up to switching to a working pressure feeding Ventilation position passing switching time of the first control valve device.

About that In addition, the object is achieved by a method for operating a solved such drive system, starting from a condition in which both admission chambers are vented are, at the same time an electrical switching signal to both control valve devices applies to the relative to each other time-delayed switching cause the two control valve devices.

The delayed counter ventilation can be this way be initiated without resorting to sensor means that have a certain event and / or a certain Detect time course. Consequently, expensive monitoring measures are saved. Also required for operating the control valve device Media can be relative be implemented cost-effectively, since no time short consecutive switching signals must be generated. The electrical activation of the two control valve devices takes place at the same time, for example, by a single, simultaneously two control valve devices switched switching signal or by two simultaneously generated switching signals, wherein the providing the desired time delay effect Measure in the different structural design the two control valve devices can be found. One attacks, for example back on control valve devices that come from home have different switching times, for example, conditionally by different friction values of cooperating with each other Valve components or by using different control pressures with pilot-operated valve designs.

The drive system can optimally be operated if the first stroke movement is initiated in a state in which both admission chambers are vented. This means that the output unit extends at the beginning of the first stroke against a completely "empty" second Beaufschlagungskammer and no significant counterforce is exposed until shortly thereafter, the counter-ventilation is time-delayed effect. The counter-ventilation ensures after initial strong acceleration of the output unit a sufficiently strong deceleration to avoid a hard impact in the final position or the effectiveness of possibly integrated into the drive Endlagämpfungsmaß guarantee.

advantageous Further developments of the invention will become apparent from the dependent claims out.

to Actuation of the two control valve devices is the Drive system expediently with suitable Control means equipped to generate the switching signal and transfer, the latter either via cable or wirelessly. The control means are expediently formed by an electronic control device, in particular one so-called PLC, as they are for the operation electro-pneumatic Drive systems are usually used anyway and at Many users already exist, so they for the control of the drive system according to the invention can be shared.

Conveniently, The two control valve devices differ in their Design type. Preferably, the first control valve device is a 5/3-way valve formed and the second control valve device as a 3/2-way valve. The first control valve device can then not only the first Lift movement, but also the return stroke in the frame an oppositely oriented second stroke movement. It acts then as a directional control valve to specify the direction of movement.

From It is an advantage if both control valve devices of the pilot-controlled Type are, so in each case an electrically actuated pilot valve device included on the basis of the received electrical switching signal Generate a fluidic control signal, which ultimately switching the Control valve device causes. In such a case you can for example, about the selected type of feeder the fluidic control signal - for example, using various throttle cross sections - or by selection different sized actuating surfaces influence the switching times as desired for the fluidic actuating signal.

Before the two control valve devices in the ventilation position or the counter ventilation position are switched, take they expediently a treatment as readiness Stel markable switching position. This ensures a Vent the second impingement chamber so that the first stroke with fully vented can begin second impingement chamber. The time duration while to maintain the ready position for complete ventilation can be determined experimentally before become. The determined value is then in the context of a timed Acting considered and enabled adherence to minimum clock frequencies for consecutive clock frequencies first and second strokes.

In order to the back pressure does not rise excessively is in the brake pressure supplying fluid line expediently a pressure relief valve turned on, that too strong Pressure increase allows blowing off the overpressure. If the brake pressure is provided by means of a pressure regulator, the has sufficient secondary ventilation measures, can be dispensed with a separate pressure relief valve.

Also the working pressure is expediently means a pressure regulator provided at the desired height. Conveniently, both pressure regulators are input side connected to a common feed connection, so that a common compressed air supply is possible.

Around to ensure the desired high traversing speed it requires the provision of a sufficiently high amount of compressed air. The easiest way to do this is through an intermediary Ensure compressed air storage, which is a sufficiently high Buffer volume provides.

Conveniently, the directional control of the output unit is effected by means of the first control valve device. It therefore preferably contains two at each of the working connections connected to both admission chambers as well a ventilation connection for feeding the working pressure. In addition, it is preferably with two vent ports equipped, of which at least one to the work connection the second control valve device is connected, so that over this venting is feasible, when the first control valve means the above-mentioned Standby position occupies. The second vent port can lead directly to the atmosphere, if the second Lifting be performed without counter ventilation should. However, if a reverse ventilation is desired, can the second vent connection also to a second Control valve device connected, so that is a functional mirror image arrangement of the control valve devices results.

The invention will be explained in more detail with reference to the accompanying drawings. The only figure ( 1 ) shows the diagram of a preferred embodiment of the drive system according to the invention, which is advantageously suitable for carrying out the method according to the invention.

The total with reference number 1 designated electro-pneumatic drive system includes a drive device 2 which is operated by compressed air. In principle, the drive system could have more include similar or different drive devices.

Exemplary is the drive device 2 designed as a linear drive and contains a housing 3 in which the piston 4 a linearly movable output unit 5 slidably received. The output unit 5 has one outside the case 3 accessible power output part 6 on which an object to be moved 7 fix it.

The drive device 2 of the embodiment is designed as a pneumatic cylinder whose power output part 6 a piston rod is. Conceivable, however, would be a rodless design.

The piston 4 divides the interior of the housing 3 under sealing in a back-side first admission chamber 8th and one of the power output part 6 interspersed front, second Beaufschlagungskammer 9 ,

By coordinated pressurization of the two Beaufschlagungskammern 8th . 9 can be the output unit 5 relative to the housing 3 to optionally a right in the drawing to the right first stroke 12 or an opposite second stroke 13 drive. Here, the output unit shifts 5 between a in the embodiment, the retracted state of the output unit 5 defining first end position and a second end position. The first end position is the starting point for the first stroke movement 12 , the second end position is the starting point for the opposite second stroke movement 13 , In the first end position, the volume has the first admission chamber 8th a minimum, in the second end position, the volume of the second Beaufschlagungskammer 9 , The end positions are due to the housing 3 arranged stop means predetermined.

The two admission chambers 8th . 9 are at two work connections 14 . 15 a first control valve device 22 connected. The latter expediently has a 5/3-valve functionality, thus has five fluid connections and three possible switching positions. It acts as a directional control valve to control the direction of movement of the output unit 5 ,

Except the two working connections 14 . 15 contains the first control valve device 22 a ventilation connection 16 , which has a first feeder 24 is supplied with pressurized air under a certain working pressure. The working pressure is set by a first pressure regulator 26 ready, the input side with a feed connection 28 is connected to a pressurized air supplied under an operating pressure compressed air source P is connected or connected.

The one by the first pressure regulator 26 adjusted working pressure is lower than the operating pressure provided. For example, it is 7 bar, while the operating pressure is 8 bar.

As a further fluid connections contains the first control valve device 22 still a first vent connection 17 and a second vent port 18 , During the second vent connection 18 preferably connected directly to the atmosphere - exemplarily with the interposition of a silencer - is the first vent port 17 via a fluidic connection line 31 with the only working connection 32 a second control valve device 23 in connection, which has a 3/2-valve functionality in the embodiment.

The second control valve device 23 has three fluid connections and two possible switching positions. In addition to the work connection 32 There is a vent port, for better distinction from the above-mentioned vent connections as the third vent port 33 is designated. In addition, the second control valve device 23 provided with a connection for supplying compressed air connection, which due to its intended use as a counter ventilation connection 34 referred to as.

The counter ventilation connection 34 is via a second feedline 25 supplied with compressed air, which is under a fluid pressure called brake pressure. The brake pressure is from a respect to the first pressure regulator 26 independent second pressure regulator 27 provided, the input side also with the feed connection 28 is connected and thus supplied with pressurized air under the operating pressure.

Preferably, therefore, for fluid supply both pressure regulator 26 . 27 a common feed connection 28 available, which minimizes the connection costs.

Both pressure regulators 26 . 27 are expediently equipped with secondary venting means, so that they are in principle capable of increasing the pressure in the associated feed line 24 . 25 to respond by a venting measure.

The two control valve devices 22 . 23 are formed electrically actuated. About schematically indicated electrical control lines 35 . 36 . 40 They can be supplied to their operation with electrical switching signals. The latter are taxed 37 generated, preferably in Form of an electronic control device are realized, in particular a so-called programmable logic controller (PLC). The control means 37 In particular, they may be designed to be capable of being next to the drive system 1 also to control other systems and components.

In the electrically deactivated state, the second control valve device takes 23 due to a spring bias the apparent from the drawing vent position. In this state is the first vent port 17 via the third vent connection 33 vented to the atmosphere. The latter can in turn be done with the interposition of a muffler.

For the operation of the drive system 1 particularly relevant is the fact that the second control valve device 23 from the venting position in a counter-ventilation position is switchable, in the second feed line 25 via the counter ventilation connection 34 and the work connection 32 with the first vent connection 17 is connectable. As a result, it is possible by the first control valve device 22 through pressurized air under the brake pressure in the second Beaufschlagungskammer 9 feed when the first control valve device 22 their ventilation position occupies.

The second pressure regulator 27 is set so that the brake pressure is lower than the working pressure. In the embodiment, it is about 4 bar.

Conveniently, the drive system 1 operated according to the following procedure.

The starting point is the middle position of the first control valve device, also referred to below as the readiness position 22 with simultaneous venting position of the second control valve device 23 , This condition gives the 1 again. Both control valve devices 22 . 23 are electrically deactivated, wherein the ready position is ensured in particular by not further illustrated mechanical holding means. The output unit 5 takes the leftmost first end position.

In the middle position of the first control valve device 22 is the first feeder 24 shut off and the two Beaufschlagungskammern 8th . 9 are over the two working connections 14 . 15 and the first and second vent ports connected thereto 17 . 18 vented. Both admission chambers 8th . 9 are therefore depressurized. In principle, now the output unit 5 be moved back and forth by hand with little effort.

Now, the output unit 5 be moved from the first end position to the second end position at high speed. For this purpose, the control means 37 over the two control lines 35 . 36 at the same time an electrical switching signal to both control valve devices 22 . 23 , The consequence of this is that the first control valve device 22 switches from the ready position to the right in a designated as ventilation position first switching position and that the second control valve device 23 switches from the vent position to the counter ventilation position. In the ventilation position takes place via the ventilation connection 16 aeration of the first admission chamber 8th instead of. After completion of these two switching operations, the first admission chamber 8th with the working pressure and the second admission chamber 9 subjected to the brake pressure.

However, this pressurization takes place delayed. This results from the different structural design of the two control valve devices 22 . 23 , which has the consequence that the first control valve device 22 has a shorter switching time than the second control valve device 23 to switch from receipt of the electrical switching signal in the relevant switching position.

So while the first control valve device 22 already switched to the ventilation position, finds the switching of the second control valve device 23 in the counter-ventilation position in this regard with a small time delay instead. For a short time, therefore, a venting of the second Beaufschlagungskammer continues 9 via the first vent connection 17 and the second control valve device located in the venting position 23 , The time delay may, for example, be so pronounced that it amounts to one third of the total time that the output unit 5 needed to get in the context of the first lifting movement 12 to move from the first end position to the second end position.

This ensures that the output unit 5 during the first phase of the first stroke 12 due to the lack of pressure build-up, it is accelerated very strongly, in order then to continue in the course of the first stroke movement 12 be gradually slowed down by the counter-ventilation by means of the brake pressure so that it reaches the second end position without appreciable impact or at least with a residual energy that can completely degrade a conventional pneumatic Endlagendämpfungseinrichtung, with the drive device 2 preferably also equipped.

The significant difference between the two control valves for the different switching times 22 . 23 lie in the embodiment, inter alia, in the different valve types, which have different internal friction values, so that the switching operation of the second control valve device 23 runs slower than that of the first control valve device 22 , However, it would be readily conceivable to additionally or alternatively provide other measures that cause the different switching times. In conjunction with pilot operated control valve devices 22 . 23 For example, there is the possibility of the fluidic control signal of the electrically actuated pilot valve device 42 acted upon surface of the valve member of the main valves of different sizes, so that at the same pilot pressure divergent actuating forces are generated, which have a different speed switching result.

For achieving the desired high speed of the output unit 5 It is advantageous if the cross sections of the fluid channels are chosen as large as possible. It is expedient, moreover, to provide a large amount of air a compressed air storage 43 in the working pressure supplying the first feed line 24 turn. For typical applications, a buffer volume on the order of 10 liters has been found to be sufficient so that the overall dimensions of the drive system can be kept moderate. The compressed air storage 43 prevents the occurrence of a pressure drop in the first Beaufschlagungskammer especially during the initial, very high air requirement accelerating phase 8th ,

Since the staggered switching of the two control valve devices 22 . 23 does not need to be called forth by special sensor means ago, a simple construction of the drive system is possible, which works very reliable. Since the to the control means 37 Asked claim is only directed to generate two simultaneous switching signals or only one switching signal, the then two control valve devices 22 . 33 is switched, also provides the electronic structure of the control means 37 no particularly high requirements, which in turn benefits the production costs.

Reaching the second end position of the output unit 5 is determined by first position sensor means 38 detected and sent to the control means 37 reported. It can then, depending on the application, a temporary holding the second end position or an immediately subsequent return movement are caused in the first end position.

To return to the first end position, the first control valve device 22 through a via the control line 40 supplied switching signal of the control means 37 switched from the ventilation position to a third switching position referred to below as the reverse position to the left of the center position, in which the first Beaufschlagungskammer 8th vented and the second Beaufschlagungskammer 9 is ventilated. This switching is preferably done without inserting a stopover in the middle position. This has the effect that when driving over the center position by the first control valve device 22 both admission chambers 8th . 9 be vented in part, with the in the first Beaufschlagungskammer 8th remaining compressed air is sufficient to cause a pneumatic braking and thus a smooth reaching the first end position.

From the time when the brake pressure is no longer in the second Beaufschlagungskammer 9 is needed, the second control valve device 23 be switched back to the venting position. This is done by a corresponding switching signal of the control means 37 causes, especially when reaching the second end position.

With the return to the first end position, a work cycle is completed. The reaching of the first end position is by second position sensor means 39 detectable and is sent to the control means 37 is reported.

Before after completion of a cycle again the first stroke 12 is triggered, it is recommended a complete bleeding the second admission chamber 9 , A preferred mode of operation therefore provides that the first control valve device 22 before the renewed triggering of the first stroke movement 12 is held in the standby position for a certain period of time, in which case at the same time the second control valve device 23 the final vent position occupies. As a result, the second Beaufschlagungskammer 9 completely empty and the first stroke 12 starts with fully vented second admission chamber 9 , By time monitoring and / or timing, it can be ensured during continuous cyclic operation that the standby position is maintained for a sufficiently long period of time. The latter can be determined beforehand and can be found in the tax credits 37 save as reference value.

Conveniently, measures are taken to prevent the brake pressure appreciably over that by the second controller 27 predetermined value increases. This can be done by the secondary venting means of the second pressure regulator 27 be guaranteed if they have a sufficiently large outflow cross section. Alternatively or additionally, however, there is also the advantageous possibility of supplying the brake pressure in the second feed line 25 one from the second pressure regulator 27 independent pressure relief valve 44 turn on, which keeps the brake pressure at the desired level. The second control valve device 23 can remain unchanged in the counter ventilation position.

While the high-speed phase in the embodiment of the first stroke 12 limited, of course, there is the possibility of a comparable high-speed phase also in the second stroke movement 13 to realize. For this it is sufficient, the second vent port 18 in the same way as the first vent port 17 to interconnect, ie, inter alia, to another second control valve device 23 connect, which can also supply a brake pressure or make a vent, as to the first control valve device 22 true. The two second control valve devices 23 are then alternately simultaneously with the first control valve device 22 supplied with a switching signal.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102005060530 A1 [0002]

Claims (15)

Electro-pneumatic drive system, with at least one pneumatically actuatable drive device ( 2 ), which has a two admission chambers ( 8th . 9 ) dividing output unit ( 5 ), the two oppositely directed lifting movements ( 12 . 13 ) between two end positions, wherein at least the one, first stroke movement ( 12 ) can be brought about by the fact that the one, first admission chamber ( 8th ) is pressurized with pressurized air under a working pressure and, after a time delay, the other, second admission chamber ( 9 ) is counter-ventilated with pressurized air which is at a lower pressure than the working pressure, characterized in that for controlling the ventilation of the first pressurizing chamber ( 8th ) an electrically operable first control valve device ( 22 ) and for controlling the counter-ventilation of the second admission chamber ( 9 ) an electrically actuated second control valve device ( 23 ) is present, these two control valve devices ( 22 . 23 ) are formed so differently that from the simultaneous application of an electrical switching signal to both control valve devices ( 22 . 23 ) the switchover duration of the second control valve device that elapses until it is switched over into a counter-ventilation position supplying the brake pressure ( 23 ) is longer than the switchover to the switching to a working pressure supplying ventilation position elapse switching period of the first control valve device ( 22 ). Drive system according to claim 1, characterized in that it is connected to the two control valve devices ( 22 . 23 ) communicating control means ( 37 ), for the simultaneous output of an electrical switching signal to both control valve devices ( 22 . 23 ) are formed. Drive system according to claim 2, characterized in that the control means ( 37 ) are formed by an electronic control device. Drive system according to one of claims 1 to 3, characterized in that the two control valve devices ( 22 . 23 ) differ in their design, wherein expediently the first control valve device ( 22 ) a 5/3-valve functionality and the second control valve device ( 23 ) has a 3/2 valve functionality. Drive system according to one of claims 1 to 4, characterized in that at least one and expediently both control valve devices ( 22 . 23 ) are of a pilot-operated type, in which the switching operation is controlled by an electrically actuable pilot valve device ( 42 ) generated fluidic actuating signal is caused. Drive system according to Claim 5, characterized in that, in order to obtain a different switch-over duration, the actuating surfaces of the two control valve devices which can be acted upon by the fluidic actuating signal ( 22 . 23 ) are formed differently large. Drive system according to one of claims 1 to 6, characterized in that the first and / or second control valve device ( 22 . 23 ) in one of the initiation of the first stroke movement ( 12 ) immediately preceding standby position is / are in which the second loading chamber ( 9 ) is vented, such that the first stroke movement ( 12 ) with completely deaerated second admission chamber ( 9 ) begins. Drive system according to one of claims 1 to 7, characterized in that in the brake pressure supplying feed line ( 25 ) a pressure relief valve ( 44 ) is turned on by the at a certain pressure increase beyond the brake pressure while maintaining the counter-ventilation position of the second control valve device ( 23 ) a venting of the second admission chamber ( 9 ) can be evoked. Drive system according to one of claims 1 to 8, characterized in that for the provision of the working pressure, a first pressure regulator ( 26 ) and to provide the brake pressure, a second pressure regulator ( 27 ), whereby expediently both pressure regulators ( 26 . 27 ) on the input side with a common compressed air supply enabling common feed connection ( 28 ) are connected. Drive system according to one of claims 1 to 9, characterized in that in the first control valve device ( 22 ) supplying the working pressure supply line ( 24 ) a compressed air reservoir ( 43 ) is turned on. Drive system according to one of claims 1 to 10, characterized in that the first control valve device ( 22 ) via two to one of the two admission chambers ( 8th . 9 ) connected working connections ( 14 . 15 ) and in addition a serving for feeding the working pressure ventilation port ( 16 ), and a vent port ( 17 ), which has a working connection ( 32 ) of the second control valve device ( 23 ) and via which, depending on the position of the second control valve device ( 23 ) the second admission chamber ( 9 ) is counter-ventilated or vented. Drive system according to claim 11, characterized in that the first control valve device ( 22 ) a directly connected to the atmosphere further exhaust port ( 18 ), via which the first admission chamber ( 8th ) during the first stroke movement ( 12 ) opposite second stroke movement ( 13 ) and then until the first control valve device ( 22 ) is vented to the ventilation position. Method for operating a drive system according to one of Claims 1 to 12, characterized in that, starting from a state in which both admission chambers ( 8th . 9 ) are vented, at the same time an electrical switching signal to both control valve devices ( 22 . 23 ) applies to the relatively time-delayed switching of the two control valve devices ( 22 . 23 ). Method according to Claim 13, characterized in that the switching signal is then sent to the two control valve devices ( 22 . 23 ) after reaching the starting point for the first lifting movement ( 12 ) forming end position of the output unit ( 5 ) has allowed a period of time to elapse, the complete venting of the second admission chamber ( 9 ) guaranteed. Method according to claim 13 or 14, characterized in that a first control valve device ( 22 ) is used with a three-position characteristic and this first control valve device ( 22 ) without intermediate stop from the ventilation position via a simultaneously both admission chambers ( 8th . 9 ) Entlüftende center position in one of the first stroke movement ( 12 ) opposite second stroke movement ( 13 ) reversing reversing position after the end position of the first stroke has been reached.