EP0694693B1 - Method and device for valve control - Google Patents

Description

The invention relates to a device with at least one over one Lifting gripper in the lifting direction on a closing element of a valve of a piston compressor acting control cylinder, which has a control element for influencing the periodic stroke movement of the closing element periodically with Pressure medium can be acted upon and relieved, and a method for Influencing the periodic stroke movement of the closing element of a valve a piston compressor, one using a lifting gripper in the lifting direction control cylinder acting on the locking member periodically with pressure medium is acted upon and relieved.

For mainly in reciprocating machines, such as internal combustion engines and Like. On the one hand and pumps, compressors and the like. On the other hand, for control of the workflow necessary, periodically according to the work cycle Open or closed valves are different types of actuation known. These range from rigid, mechanical override in both Stroke directions (e.g. desmodromic valve control in internal combustion engines) via spring-loaded intermediate forms actuated by cams or the like right down to compressor valves that are only spring-loaded in the closing direction, which are opened by the pressure of the gas flowing through. The last mentioned automatic ones, especially common with piston compressors Valves therefore work with free movement of the valve rings or Valve plate, which is caused solely by the interplay of the attacking Flow or pressure and spring forces is required. The interpretation of a such valve therefore always compromises between minimal flow loss and maximum life expectancy and requires a lot of experience or appropriately sophisticated calculation methods, otherwise there is the risk of unforeseen Malfunctions or undesirable operating behavior of the Valves.

In the history of building piston compressors, therefore, have always been Again attempts have been made that have proven themselves in engine construction, for example use positively controlled valves, which in principle decouple the Allow contradictory interpretation requirements mentioned above. However, such positively controlled valves require a relatively complex one Tax logic according to the required variable tax times for the Compressor control and are with inadequacies of the mechanical used or also hydraulic constructions as well as with high costs for mechanical actuators (such as camshafts, rocker arms, control rods, etc.) afflicted with what has been a further spread of such constructions prevented.

For example, an electromagnetically operated regulation of the Suction valves of piston compressors have been known for a long time, in which an Sealing element of the suction valve engaging lifting gripper via a on the valve cover attached electromagnet is moved, the periodic excitation done by a collector, which is synchronous with the crankshaft of the Compressor rotates. Due to the sometimes very large backflow forces, which on Sealing element of the suction valves act, are large electromagnets with corresponding Power consumption required, which is mostly disadvantageous and undesirable is. Furthermore, there has also been a pneumatic control device for a long time to keep suction valves open during part of the pressure stroke is known in which the influence of the valves to be kept open by the compressing gas itself. The control takes place by means of a rotary valve, over which several individual cylinders in which gripper pistons work, periodically controlled. The complexity of the Appearance of further spread apparently.

In connection with the delivery quantity control of with constant speed running piston compressors has at least partly the so-called Backflow control by keeping open at least one suction valve per cylinder Proven over a certain range of compression stroke, the Pressure forces or flow forces of the suction valve kept open pushed back gas after the closing element of the respective suction valve Overcoming a certain part of the piston stroke can close because of on the other hand this closure organ with a corresponding to the desired one Delivery rate reduction set counterforce is applied. The greater this counterforce, the later the respective suction valve closes in the compression stroke, which reduces the delivery quantity. Since too large The suction valve suddenly suddenly stopped at all closes, the control range for this type of compressor control must be readjusted be limited below, in order to temporarily idle the compressor with all related problems to avoid.

In the latter context, versions are also known at which the loading device for the suction valve to be kept open simply is hydraulically or pneumatically biased, by varying the corresponding preload pressure influence on the delivery rate of the compressor can be taken.

Finally, for example from US Pat. No. 3,104,801 and US Pat 1,798,435 or U.S. Patent 2,657,850 arrangements known in which about centrally located rotary valves or units, the structure of the known diesel injection pumps are similar to that on the closing member acting control cylinder is periodically supplied with pressure medium, which on End the desired influence on the closing element of the valve accordingly is taxed. There are also known designs at which the pressure medium supply by means of a check valve for pressure relief is locked, so that the discharge via a separate, larger one Flow-resistant drain throttled or damped.

A disadvantage in the known, last mentioned and initially The devices mentioned is in particular the fact that the required high pressures for periodically influencing the lifting movement of the closing member Problems with the usually relatively high speeds and thus require short periods of the lifting movement of the closing member. So is easily understand that only a high compressor or compressor speed very short periods of time for the periodic stroke movement of the closing element of a valve to be influenced as described, what is desired large opening cross sections and an associated large stroke of the Locking device high lifting speeds and thus e.g. the danger of Damage and breakage of the closing element at the end of the lifting movement brings itself. The high periodic pressure waves on the control cylinder the pressure medium acting on the closing element can be caused by pressure wave phenomena bring additional problems in the lines that total up previously opposed the use of the known technology.

The object of the present invention is a device and a Process of the type mentioned to improve so that the mentioned Disadvantages of the known devices and methods are avoided and that influencing the periodic, in particular with simple means Stroke of the closing member can be done so that even with large required Pressing the pressure medium acting on the control cylinder and highly dynamic control processes created a reliable arrangement will not reach those mentioned, even over a long period of operation Disorders tends.

This object is achieved with a device of the type mentioned solved in that the control member at least one in supply and / or discharge switched on the print medium and this or its print up and / or -Degradation and thus the lifting movement of the closing member at least gradually has variably accelerating or decelerating control element, and that a check valve between the control element and an upstream pressure medium source is provided. The corresponding embodiment of the invention The method is characterized in that the pressurization and / or relief via the stroke of the closing member at least in stages variable, the reaction of the compressor pressure via the closing element to the pressure medium source is prevented by means of a check valve. In the simplest case, the control element mentioned can be used, for example, for a over the control cylinder for a certain part of the compression stroke open suction valve of a piston compressor, the pressure relief for example, control so that at the beginning of the flow forces released Closing movement of the valve plate of the suction valve relieves this pressure largely unthrottled and thus the corresponding valve plate movement takes place very quickly, whereas before opening the valve plate by reducing the pressure relief on the seat by switching can take place that a braked and at least within limits the valve plate hits the valve seat gently. Similar Movement influences of the closing element of the valve can of course also make sense in the opening direction of the valve plate, for example, if the unbraked stop of the opening valve plate on a catcher should be prevented. The check valve mentioned offers the advantage that the input pump pressure is not the greatest via the closing element retroactive force must correspond to the installed pump capacity and energy consumption can also be reduced.

Overall, with the described features or measures according to the Invention a largely free influence on the pressure build-up or reduction in pressure medium acting on the control cylinder, which is a Wide range of options for influencing the movement characteristics of the closing element of the associated valve. The design of the Control member with at least one in the supply and / or discharge of the pressure medium switched on and this or its pressure build-up and / or reduction and thus the stroke movement of the closing member is accelerated variably at least in stages or delaying control element, for example known from W0-93 / 14339-Al and JP-60-113008. Both of these writings relate to corresponding configurations in connection with the control of Disc valves of internal combustion engines, which - as already mentioned at the beginning - According to the usual, usually practically forced, operations there not with the usually only under the influence of gas exchange forces automatically moving valve plates of piston compressor valves are comparable.

The control member can, for example, at least one variably controllable Switching element, for example a piezo valve, with several switching positions have, which also forms the control element. According to one preferred development of the invention can also be provided that the control member has at least one separate switching element, preferably a Solenoid valve or a piezo valve, with several switch positions and one independent control element, with at least one by means of the pressure medium movable displacement piston, which is a switching element for switching of the pressure medium flow between at least two different actuated throttled ways. In the first case, the controllable Switching element, e.g. about the flow cross-sections that can be directly influenced thereby to the control cylinder acting on the locking element, itself too at the same time the control element for variable acceleration or deceleration the pressure build-up or reduction, which is a relative device simple and therefore inexpensive and reliable construction. In the second case, the formation or arrangement of the separate switching element rather uncritical, since it only controls different pressure medium paths will. Only via the control element, which is constructively independent of the switching element are then made according to that made via the switching element Pressure medium supply the desired effects on pressure build-up or reduction performed. This variant is in terms of the structure of the device and the process the process is cheaper and easier with current technologies to realize. The overall result is a very simple mechanical one Design of the control element with which, for example, the one mentioned above Braking the valve plate of a suction valve that was initially kept open be accomplished before hitting the valve seat can.

With regard to the backflow control already mentioned above, one Piston compressor by keeping at least one suction valve open at least a portion of the compression stroke by pressurizing the closing element of the suction valve via a lifting gripper is another Embodiment of the inventive method is advantageous, according to which on Pressure relief at the end of the periodically kept section initially at least largely unthrottled and then more restricted he follows. This also results in this type of compressor control Advantage that the locking device which is initially open is not under the influence the backflow forces that are already too great at the time of release high speed hits the valve seat without braking, which too Damage to the valve seat and valve plate or lead to spring breaks could.

The invention is explained in more detail below with reference to the drawing. 1 and 2 show schematic embodiments of the invention and FIG. 3 shows curves of the speed v and the pressure p for different operating points of a suction valve control according to the invention on the one hand and the state of the art on the other.

In the embodiments shown in FIGS. 1 to 2, the Movement of the sealing element 12 of a valve not shown Piston compressor by means of a so-called lifting gripper 11 transmit a control piston 10 of a control cylinder. Because forces in here only control direction 8 is to be transmitted, the control cylinder 8 designed as a single-acting cylinder with workrooms 9. Such The arrangement is suitable, for example, for closing suction valves or the opening of pressure valves of piston compressors in the invention Kind of influencing.

For example with a pump, motor, tank and adjustable pressure relief valve equipped hydraulic unit 1 supplies via supply lines 3 a magnetically operated 3/2-way valve 5 with pressure medium, for example. As long as the magnet 6 remains de-energized, a spring 7 presses the valve 5 in the shift position shown. Pressure fluid thus flows into the work space 9 of the control cylinder 8 and acts on the control piston 10. This presses the Power transmission device 11 to the sealing element 12 of the compressor valve.

In the case of the suction valve shown in Fig. 1, this is Valve opened or if the sealing element 12 already bears against the catcher 14 fixed in the open position. At the end of the intake stroke of the valve associated compressor cylinder, i.e. when bottom dead center is reached, return to the sealing element 12 exerted by the working medium of the compressor Flow forces in their direction of action and now try that Close sealing element 12. These forces are created by the action of general closing spring 15 of the valve reinforced. The pressure in Working space 9 of the control cylinder 8 increases and then generally exceeds the pressure supplied by the hydraulic unit 1, because that in the supply line 3 upstream of the 3/2-way valve 5 check valve 4 den Backflow of the pressure medium blocks, so that the position of the control piston 10th remains fixed.

Only when the solenoid 6 of the valve 5 is energized does it control and releases the reflux of the pressure medium. The back pressure fluid flows an auxiliary cylinder 16, which has a piston 17 and working spaces 18, 19th having. The working space 18 of the auxiliary cylinder 16 is shown in the Example chosen so that except for losses on the bypass through the Throttle 21 receives the stroke movement of the piston 17 that part of the pressure medium, that during the first part of the movement of the control piston thereof is ousted. The pressure medium displaced by the piston 17 from the working space 19 flows through the throttle 22, which is the flow resistance here The overall arrangement symbolizes and is designed with as little loss as possible.

As soon as the piston 17 has reached its end position, this is from the control piston 10 from the control cylinder 8 displaced pressure medium only the Outflow via the throttle 21 is available, which is considerably higher here Resistance than the throttle 22, so that from this point in time of movement of the control piston 10 opposed to a multiple increased force and thus a considerable delay in the movement of the sealing element 12 is initiated. The sealing element 12 only hits in the sequence at greatly reduced speed on the valve seat 13.

The power transmission device 11 is only with the sealing element 12 occasionally in contact. Therefore, the power transmission device 11 lifts off Sealing element 12 as soon as it has reached its end position on the seat 13. The Residual movement of the power transmission device 11 is due to the strong Throttling the outflow of the pressure medium is strongly damped, so that the power transmission device 11 then came to a standstill by the shortest route. It can thus safely be avoided that the control piston 10 him assigned stroke limit actually reached, thus damaging the Control piston 10 and the associated control cylinder 8 is avoided. Out For safety reasons, such a stroke limitation becomes constructive, for example designed so that a hydraulic cushioning is guaranteed. In practical operation of the arrangement, the control piston 10 reaches it However, not the end position, so that the known disadvantage of hydraulic End position damping, namely the difficult breakaway from the end position at Initiation of the counter movement, can be avoided.

As soon as the outflow of pressure medium from the work space 9 has ended, the piston 17 begins under the action of the spring 20 in its initial position to move back. This spring 20 must on the one hand the compressive forces Result of the overflow from the work space 19 into the work space 18 through the Throttle 21 and on the other hand overcome the inertia of the piston 17 itself. A working cycle of the arrangement is then completed.

The rest position of the 3/2-way valve 5 is the safety requirements to choose according to. Advantageously, the 3/2-way valve 5 in the de-energized state, the connection between control cylinder 8 and hydraulic unit 1 free, so that the control piston 10 is fixed in the lower position and the compressor is idling.

For the sake of completeness, here is still pressure fluid reservoir 2 or 23 as a pulsation damper in the supply and return of the pressure medium, the avoidance of liquid hammer and associated undesirable Effects on the movement of the control piston 10 and thus the power transmission device 11 and the sealing element 12 serve.

In the case of the embodiment for the control of Pressure valves of a piston compressor, the movement of the sealing element 12th by the catcher 14 by means of the power transmission device 11 on the Transfer control piston 10. The 3/2-way valve 5 is in its rest position the connection of the working space 9 of the control cylinder to the working space 18 of the auxiliary cylinder 16 free. As soon as those attacking the sealing element Gas forces overcome the closing spring 15 of the valve, it starts To drain pressure medium. In a manner similar to that for the above Suction valve according to FIG. 1, the movement of the sealing element 12 braked only a little at first. Just before hitting the Catcher 14, the weakly throttled outflow of the pressure medium is interrupted. The pressure medium must now overcome the throttle 21, creating a strong Delay in the movement of the sealing element 12 is reached. In analogy to Description for the suction valve can also be the force transmission element 11 run out heavily braked.

To initiate the closing movement of the sealing element 12 becomes a appropriately chosen time before reaching the top dead center of the Compressor piston the 3/2-way valve 5 by energizing the magnet 6 switched. This allows pressure medium to flow in and the sealing element against the Press valve seat 13. It is essential that the infeed movement of the Power transmission device 11 when top dead center is reached Most of the compressor piston has already taken place, but is not yet completely finished is. This can be a compression of the working medium of the compressor and additional losses caused thereby are avoided. On the other hand, it will also the possibility of a late closure of the sealing element 12 and thus associated danger of high impact speeds limited. When turning back the direction of flow of the compressed gas is thus the sealing element 12 only a very small remaining stroke available, so that from one any closing speed resulting in closing speed with regard to any increase in wear is insignificant.

With regard to other features and functional details of those shown in FIG. 2 Arrangement is made to avoid repetitions on the above Reference made to Fig. 1.

3a shows curves of the speed v of the power transmission device 11 or the sealing element 12 during a compression cycle of Duration T for different operating points of a suction valve control. Curves 1.1 and 1.2 apply to full load curves 2.1, 2.2 and 3.1 and 3.2 for Partial load. The curves are based on the maximum impact velocity v-max Sealing element 12 on the valve seat (determined over all load cases).

In Fig. 3b are the corresponding curves of the pressure p in the work area of the compressor over time t. The designated 1.1, 2.1 and 3.1 Curves represent the behavior of a compressor stage, whose suction valves are equipped with variable movement damping. The dashed curves marked with 1.2, 2.2 and 3.2 stand for Suction valves with constant movement damping (according to the state of the art), wherein the damping is designed so that the maximum impact speed of the sealing element 12 on the valve seat for variable and constant damping is about the same size.

The curves 1.1 and 1.2 apply in the event that the closing movement of the Sealing element 12 at the bottom dead center of the respective compressor cylinder is initiated by switching the control element. With increasing piston speed and the beginning of compression the working medium of the compressor an increasing closing force on the sealing element 12, which the Force of the closing springs 15 (see FIGS. 1 and 2) is superimposed. In case of variable damping, the pressure medium can initially flow out almost undamped, so that the closing force largely to accelerate the sealing element and Power transmission device is available. With constant damping the throttle should be chosen many times smaller, so that at the beginning one Most of the closing force is required to overcome the throttle resistance becomes. Accordingly, the sealing element approaches with variable damping according to the present invention, the valve seat faster than the constant State-of-the-art damping.

At a distance of about 20% of the stroke from the seat variable damping the throttling of the pressure medium outflow by a multiple increased, so that the movement suddenly opposed much more resistance and this is delayed accordingly. The sealing element then moves with significantly reduced speed to the seat, the power transmission device lifts off the sealing element and then loses in the described Get up to speed quickly.

The same impact speed of the sealing element in both cases assuming the closing process takes a long time with constant damping longer than with variable damping. During the duration of the closing process the gas to be compressed flows back, which on the one hand undesirable loss of delivery quantity and on the other hand additional work losses result, for example, from FIG. 3b by comparing curves 1.1 and 1.2 can be easily removed.

If the control element is actuated at a later time (Curves 2.1, 2.2, 3.1 and 3.2), the delivery rate is reduced and thus the drive power consumed by the compressor.

In all the illustrated and discussed exemplary embodiments is only the variable throttling of the pressure relief of the working spaces of the control cylinder realized or addressed. That being said, it would be natural also possible, the pressure build-up in the respective working space of the control cylinder to be variable, for example at the beginning of the corresponding working stroke this control cylinder has a greater adjustment speed than available at the end. It can also differ from the ones described Embodiments may be advantageous for different applications, for example, smaller at the beginning of the respective stroke of the control cylinder Adjustment speeds and then towards the end too larger available to have. Mixed forms with graded or variable speed increases and are reductions over the entire stroke of the control cylinder possible and easy to implement according to the present invention.

Furthermore, with correspondingly fast switching control units or Switching elements, for example in combination with suitable pressure sensors solutions can also be realized in which pressure waves in the pressure medium either eliminated or influenced accordingly or also reinforced can, so that a wide variety of influences on the movement characteristics of the controlled locking devices are possible.

Claims (4)

1. A device with at least one control cylinder (8) which stresses a closure member (12) of a valve of a piston compressor by way of a lift-off gripper (11) in the direction of the stroke and which can be periodically stressed by and relieved from pressure medium by way of a control member (5) in order to control the periodic reciprocating movement of the closure member (12), characterized in that the control member (5, 16) comprises at least one control element (16) which is connected in the supply and/or removal line (3, 24) of the pressure medium and which accelerates or retards the said pressure medium or its build-up and/or reduction and thus the reciprocating movement of the closure member (12) in a variable manner at least in stages, and a non-return valve (4) is provided between the control member (5) and a pressure-medium source (1) arranged upstream thereof.
2. A device according to Claim 1, characterized in that the control member (5, 16) comprises at least one separate switching element (5), preferably a solenoid valve or a piezo valve, with a plurality of switching positions and a control element (16) dependent thereon, with at least one displacement piston (17) which is movable by means of the pressure medium and which actuates a change-over element for changing over the pressure-medium flow between at least two paths throttled in different ways.
3. A method of controlling the periodic reciprocating movement of the closure member of a valve of a piston compressor, wherein a control cylinder stressing the closure member by way of a lift-off gripper in the direction of the stroke is periodically stressed by and relieved from pressure medium, characterized in that the stressing with and/or relief from pressure takes place in a variable manner at least in stages by way of the stroke of the closure member, wherein the returning action of the compressor pressure by way of the closure member upon the pressure-medium source is prevented by means of a non-return valve.
4. A method according to Claim 3 for regulating the return flow of a piston compressor by keeping open at least one suction valve by way of at least one partial area of the compression stroke by means of stressing the closure member of the suction valve with pressure by way of a lift-off gripper, characterized in that at the end of the partial area kept open periodically in each case the pressure relief takes place first at least substantially unthrottled and then more strongly throttled.

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