DE19721759A1 - Energy reduction process for pneumatic drive - Google Patents

Abstract

The energy reduction process involves displacing all the exhaust air from the piston rod cavity (13) into a prestressed store (1), so that compression work is accomplished. This energy is used to bring about the return stroke. At the same time, the storage volume and initial pressure can be varied to bring about a positive influence on the dynamic performance of the drive. The process can be applied to the reciprocal motion of the cylinder. Switching can take place through a pressure transmitter (20) and a 2/2 path valve.

Description

Technical problem of the invention

According to DE-OS 28 23 041 a method is known, wherein a pneumatic Ar working cylinder with two pressure levels. The extension movement takes place under high pressure. When the entry movement is carried out, one is switched on first Medium pressure reservoirs so that part of the pressure energy from the working cylinder is taken up by this. This closes off the means pressure reservoirs and the ventilation of the pneumatic cylinder to the atmosphere. From the medium pressure reservoir, other pneumatic consumers with right reduced operating pressure. This method is disadvantageous that two reservoirs (high pressure and medium pressure) are needed and only one Part of the pressure energy that is in the working cylinder in the extended position finds, can be recovered. Furthermore, the procedure is only applicable bar on single-acting pneumatic cylinders.

According to DE-OS 29 15 620 is a method for avoiding energy loss in Form of a lost amount of compressed air in pneumatic piston drives knows. The piston rod space of a pneumatic cylinder turns off drive not completely vented, so that a pressure cushion can build up, which supports the return stroke. A disadvantage of this method is that the Working cylinder can never perform its full stroke. Furthermore, the ver drive only applicable using pneumohydraulic pressure translator and a hydraulic cylinder. The invention is based on the Antriebsspro General mechanical engineering problems are not applicable and remain few Special areas e.g. B. reserved for press drives. Another disadvantage is that only part of the compressed air energy can be stored for the return stroke.

According to DE-OS 32 33 739 is a device for independent resetting of an actuating cylinder known. There is one double on the piston rod side acting pneumatic working cylinder a pressure accumulator arranged in turn, a check valve, a throttle, via a pressure relief valve and connects a directional valve to the compressed air source. In the retracted position  the cylinder is switched on with the pressure relief valve set memory pressure filled. When the working cylinder is extended, a Displacing the piston rod space into the reservoir, causing it to Pressure increase in the memory should come. However, since the accumulator with the Pressure relief valve is permanently connected, which can when the Compression work done is not saved and is sent to the cylinder Environment. A disadvantage of this invention is that the energy that is necessary for the return stroke, who is constantly removed from the compressed air network the must, so that no significant energy saving effects can be achieved can. Another disadvantage is that the drive against a constant Counter force, resulting from accumulator pressure and piston ring area, must work.

This means that only traversing behavior can be achieved, which is comparable to conventional (use of throttle check valves) corresponds to pneumatic drives. That means, It is not possible to brake the drive depending on the path.

Aim of the invention

The aim of the invention is to provide a method which is capable of the ener gie, which is required for the return stroke of a pneumatic cylinder, when off save driving or retracting movement and thus an energy saving of approx. 50% while maintaining the mechanical output of the To reach the drive.

The method is also intended to improve the dynamic movement behavior of the drive.

Solution of the problem or the technical problem

The technical object of the invention is one in the piston rod space Pneumatic cylinders present pneumatic energy to the atmosphere to give up when extending the drive, but to open a memory load. This amount of energy is the drive for the realization of the return stroke feed movement again. The method also generates one of the offs driving movement proportionally increasing counterforce, which enables the Braking the drive depending on the path and continuously, so that a gentle retraction is secured in the end position. This improvement in dynamic travel behavior is independent of the external mass inertia on the An drive.  

According to the invention, the technical problem is realized by a method which preferably takes place in 6 method steps. In the first procedural step, the storage 1 and the piston rod chamber ( 13 ) are preloaded with the storage admission pressure p ₁ via the pressure reducing valve ( 2 ), the check valve ( 3 ), the 3/2 way valve ( 4 ) and the connected 2/2 Directional control valve ( 5 ) and 3/2 directional control valve ( 10 ). The process step ( 1 ) is completed after the storage pressure p _{1 has been reached} , which is detected by the pressure sensor ( 16 ), as a result of which the 2/2 way valve ( 5 ) and the 3/2 way valve ( 10 ) block again. This is followed by method step 2 , in which the piston chamber ( 12 ) of the cylinder ( 6 ) with the compressed air source ( 22 ) by switching on the 2/2 way valve ( 7 ) and the 3/2 way valve ( 8 ) via the throttle check valve ( 15 ) is connected. The cylinder ( 6 ) then extends and displaces the air from the piston rod chamber ( 13 ) via the 3/2 way valves ( 18 ) and ( 10 ) as well as the check valve ( 11 ) into the accumulator ( 1 ). This increases the storage pressure proportionally to the path. Since at the beginning of the movement the accumulator pre-pressure (p ₁ ) is relatively low compared to the pressure prevailing in the compressed air source ( 22 ), the cylinder ( 6 ) achieves high acceleration values. However, since the pressure p ₁ increases proportionally to the path, a constantly increasing counterforce acts on the cylinder ( 6 ), so that there is a progressively increasing deceleration and the cylinder moves into the end position at a low final speed. The traversing behavior of the cylinder ( 6 ) can be optimized and adapted to very different masses ( 17 ) by means of the parameters volume and pre-pressure of the accumulator ( 1 ). The process is therefore well suited to allowing pneumatic drives with heavy mass to move with high dynamics and thus fulfills a crucial point of the objective.

Method step 2 is completed when the cylinder ( 6 ) has reached its extended position.

This is followed by method step 3 , which is used to ensure that the cylinder ( 6 ) can develop the maximum force in its extended position. To do this, it is necessary to vent the small dead volume ( 19 ) of the cylinder ( 6 ), which is achieved by switching the 3/2 way valve ( 18 ). If the maximum force of the cylinder ( 6 ) is not required, method step 3 can be skipped. Shortly before the start-up movement, the method step 4 is initiated, which serves to improve the travel behavior during the return stroke and to increase the efficiency of the drive. For this purpose, there is pressure equalization between the piston chamber ( 12 ) and the accumulator ( 1 ). This makes sense because the pressure in the accumulator ( 1 ) is generally below the pressure in the piston chamber ( 12 ). Locking the 2/2 way valve ( 7 ) and briefly opening the 2/2 way valve ( 14 ) leads to a further increase in pressure in the accumulator ( 1 ). If there is pressure equality in the accumulator ( 1 ) and in the piston chamber ( 12 ), the 2/2 way valve ( 14 ) closes and thus ends process step 4 .

This is followed by step 5 , which realizes the retracting movement of the cylinder ( 6 ). For this purpose, the 3/2 way valve ( 8 ) is switched off, so that the piston chamber ( 12 ) is vented via the throttle check valve ( 15 ) and at the same time the 2/2 way valve ( 5 ) opens, the 3/2 way valve ( 10 ) is activated and that 3/2 way valve ( 18 ) is switched off. The accumulator ( 1 ) is thus connected to the piston rod space ( 13 ) and the cylinder ( 6 ) retracts exclusively with the help of the stored energy from the extension movement. Since the highest pressure prevails in the accumulator ( 1 ) at the start of the retracting movement, the desired high initial acceleration of the cylinder ( 6 ) occurs. However, this pressure drops with increasing travel, so that the drive can move into the end position at low speed. Method step 5 is completed when the cylinder ( 6 ) has reached its retracted end position. This is followed by process step 6 , which is necessary to restore the original storage pressure p ₁ , because the pressure equalization carried out in process step 4 causes the pressure in the accumulator ( 1 ) after the retracting movement of the cylinder ( 6 ) to be higher than that in the process step 1 set. To ensure constant process conditions, compressed air must be released to the atmosphere from the accumulator ( 1 ) via the still open 2/2 way valve ( 5 ) and the switched 3/2 way valve ( 4 ) and the throttle ( 9 ). The pressure sensor ( 16 ) signals the desired storage pressure and switches off the 3/2 way valves ( 4 , 10 ) and the 2/2 way valve ( 5 ). The method can thus be continued with method step 2 .

To improve the dynamics of the drive when retracting, method step 5 , the circuit can be expanded as shown in FIG. 2 by a pressure intensifier ( 20 ) and a further 2/2-way valve ( 21 ). The aim of this measure is not to discharge the exhaust air from the piston chamber ( 12 ) of the cylinder ( 6 ) directly into the atmosphere, but to use it to increase the pressure p ₁ in the accumulator ( 1 ). Thus, the 3/2 way valve ( 8 ) is connected to the pressure intensifier ( 20 ), which in turn is connected to the accumulator ( 1 ) via the 2/2 way valve ( 5 ) and via the 3/2 way valves ( 18 ) and ( 10 ) the piston rod chamber ( 13 ) is coupled.

In this circuit variant, method step 5 is completed by reaching the retracted position of the cylinder ( 6 ) and venting the pressure booster ( 20 ) by unlocking the 2/2 way valve ( 21 ).

The method can be used for both the extension and the retraction of the cylinder ( 6 ). If the extension movement of the cylinder ( 6 ) is to be carried out with the stored energy from the accumulator ( 1 ), the piston chamber ( 12 ) must be connected to the 3/2 way valve ( 18 ) and the piston rod chamber ( 13 ) with the throttle check valve ( 15 ).

application areas

The field of application of the invention extends over the entire pneumatics, insofar as pneumatic working cylinders are used. Particularly suitable the method is applicable when working cylinders with large stroke and large Piston surface are used or the drives are heavily mass-laden. In each of the applications, about 50% of the required pneumatic Energy can be saved. This is special for technical use interesting because compressed air is a very expensive energy source, what the poor efficiency, about 30% in its manufacture, is due. By the possibility, by variation of the Storage pressure and the storage volume the dynamics of the drives can influence completely new areas of application for pneumatic drives be developed, whereby the nominal sizes of the drives are reduced can. This goes hand in hand with a saving in installed pneumatic Performance as well as creating favorable design relationships as the Take up drives in a smaller space.

Embodiment

The invention will be explained in more detail using an exemplary embodiment will.

A connected to a mass 17 working cylinder 6 is connected to its piston chamber 12 via a throttle check valve 15 , a 3/2 way valve 8 and a 2/2 way valve 7 with the compressed air source 22 . Its piston rod chamber 13 is connected to the accumulator 1 via two 3/2 way valves 18 and 10 and the check valve 11 . The pressure prevailing in the accumulator 1 is tapped via the pressure sensor 16 . The accumulator 1 is in turn connected to the compressed air source 22 via the 2/2 way valve 5 , the 3/2 way valve 4 with throttle 9 and the pressure reducing valve 2 and check valve 3 . Piston chamber 12 and piston rod chamber 13 of the cylinder 6 can be connected via the 2/2 way valve 14 . In method step 1 , the 3/2 way valve 10 and the 2/2 way valve 5 are switched through, so that the accumulator 1 and the piston rod chamber 13 are acted upon by an accumulator admission pressure p ₁ , which is set on the pressure reducing valve 2 . If this pressure is reached, which is detected by the pressure sensor 16 , 2/2 way valve 5 and 3 / 2-way valve 10 are switched back to their basic position and method step 1 is completed. In method step 2 , the piston chamber 12 of the cylinder 6 is pressurized with compressed air by switching on the 2/2 way valve 7 and the 3/2 way valve 8 via the throttle check valve 15 , as a result of which the cylinder 6 extends.

During this movement, the compressed air is displaced from the piston rod chamber 13 via the 3/2 way valves 10 and 18 and the check valve 11 into the accumulator 1 , as a result of which the pressure p ₁ in the accumulator 1 increases. When the outward movement of the cylinder 6 ends, method step 2 is completed and method step 3 follows. This serves to vent the dead volume 19 by switching through the directional valve 18 . The cylinder 6 is thus able to generate the maximum force in its extended position. If this is not necessary, method step 3 can be skipped and the 3/2 way valve 18 is omitted. Shortly before the retracting movement of the cylinder 6 , a pressure equalization between the piston chamber 12 , the accumulator 1 and the piston rod chamber 13 makes sense, since the pressure prevailing in the piston chamber 12 is generally higher than that prevailing in the accumulator 1 . In order to have the largest possible amounts of energy available for the return stroke, the pressure compensation is carried out in process step 4 by switching off the 3/2 way valve 18 and the 2/2 way valve 7 and briefly switching on the 2/2 way valve 14 . Finally, process step 5 is run through, in which the cylinder 6 retracts again. This is done by reversing the 3/2 way valves 10 and 8 and the 2/2 way valve 5 . Thus, the pressure in the reservoir 1 acts on the cylinder 6 , causing the cylinder 6 to retract. Method step 5 is completed when the basic position of cylinder 6 is reached , and method step 6 follows, which is necessary for restoring the initial pressure in accumulator 1 , since method step 4 results in a higher pressure in accumulator 1 after method step 5 as the value set in step 1 form p. ₁ In order to achieve this again, the 3 / 2 -way valve 4 is actuated so that the excess pressure can be released to the environment via the throttle 9 . If the upstream pressure p _{1 is} reached, which is detected by the pressure sensor 16 , the 3/2 way valves 4 , 10 and the 2/2 way valve 5 are switched off , as a result of which the process step 6 is completed and the cycle is repeated through the processing of the process step 2 can be. The energy stored in memory 1 can also be used for the extension movement. For this application, the throttle check valve 15 must be connected to the piston rod chamber 13 and the 3 /2-way valve 18 to the piston chamber 12 of the cylinder 6 .

To improve the dynamics of the drive when retracting, method step 5 , the circuit can be expanded as shown in FIG. 2 by a pressure intensifier 20 and a further 2/2 way valve 21 . The aim of this measure is not to discharge the exhaust air from the piston chamber 12 of the cylinder 6 directly into the atmosphere, but to use it to increase the pressure p ₁ in the accumulator 1 . Thus, the 3 /2-way valve 8 is connected to the pressure intensifier 20 , which in turn is coupled to the accumulator 1 via the 2/2-way valve 5 and to the piston rod chamber 13 via the 3 /2-way valves 18 and 10 .

Reference list

1

Storage

2nd

Pressure reducing valve

3rd

check valve

4th

3/2 way valve

5

2/2 way valve

6

cylinder

7

2/2 way valve

8th

3/2 way valve

9

throttle

10th

3/2 way valve

11

check valve

12th

Piston chamber

13

Piston rod space

14

2/2 way valve

15

Throttle check valve

16

Pressure sensor

17th

Dimensions

18th

3/2 way valve

19th

Dead volume

20th

Pressure translator

21

2/2 way valve

22

Compressed air source

Claims (4)

1. A method for saving energy from pneumatic drive units best consisting of 6 process steps, characterized in that in the process step 1, which is preferably run through when starting up the system, the memory ( 1 ) with a pre-pressure p ₁ through the pressure control valve ( 2 ), the Check valve ( 3 ), the 3/2 way valve ( 4 ) and the 2/2 way valve ( 5 ) is loaded, which is followed by process step 2, in which the cylinder ( 6 ) with mass ( 17 ) via the 2/2 Directional valves ( 7 ) and the 3/2 way valve ( 8 ) are supplied with pneumatic energy from the compressed air source ( 22 ), whereby the cylinder ( 6 ) extends and its displaced volume from the piston rod space ( 13 ) via the 3/2 way valve ( 10 ) and the check valve ( 11 ) conveys into the accumulator ( 1 ), causing the pressure p _{1 to} rise in the subsequent method step 3 in the extended position of the cylinder ( 6 ) to vent the dead volume ( 19 ) r the 3/2 way valve (18), which is followed by the step 4, in which the cylinder (6) is produced, a pressure equalization between the piston chamber (12) and memory (1) just before the retraction by the 2/2 Directional control valve ( 14 ) and the 2/2 directional control valve ( 7 ) are switched off, which leads to a further increase in pressure p ₁ in the accumulator ( 1 ); In the subsequent method step 5, the retracting movement of the cylinder ( 6 ) takes place in that the 3/2 way valve ( 8 ) and the 2/2 way valve ( 14 ) move down and the 2/2 way valve ( 5 ) and the 3/2 way valve ( 10 ) are switched on, whereby the pneumatic energy present in the accumulator ( 1 ) is conducted into the piston rod chamber ( 13 ) of the cylinder ( 6 ) and the piston chamber ( 12 ) is vented via the throttle check valve ( 15 ) and the 3/2 way valve ( 8 ) becomes; After reaching the retracted position, method step 6 follows in which, by venting via the 3 / 2-way valve ( 4 ) and the throttle ( 9 ), the storage pressure p _{1 is} reduced to the original value, which is monitored by the pressure sensor ( 16 ), Method step 6 is completed when the storage pressure p _{1 is reached} by switching off the 3 /2-way valve ( 4 ) and the 2/2-way valve ( 5 ) and a cyclic start of the process can be carried out by optionally choosing process steps 1-6 or 2-6 be run through. 2. The method according to claim 1, characterized in that method step 3 and / or 4 is not performed. 3. The method according to claim 1, characterized in that in step 5 of the piston chamber ( 12 ) via the 3/2 way valve ( 8 ) is connected to a pressure intensifier ( 20 ) and this in turn via the 3/2 way valve ( 10 ) and that 2/2 way valve ( 5 ) is in operative connection with the accumulator ( 1 ) and the piston rod space ( 13 ) and method step 5 is ended, after which the cylinder ( 6 ) is retracted and by briefly opening the 2/2 way valve ( 21 ) the piston chamber ( 12 ) of the cylinder ( 6 ) has been vented. 4. The method according to claim 1, characterized in that the throttle check valve ( 15 ) with the piston rod chamber ( 13 ) and the 3/2 way valve ( 18 ) with the piston chamber ( 12 ) of the cylinder ( 6 ) is connected.