The invention relates to a pressure-regulating valve having a valve piston which is subjected to the action of an energy store and which is guided in a longitudinally displaceable manner in a valve housing, which valve housing has connection points such as a supply connection, a utility connection and a tank connection, which connections can be actuated, by means of a control part which closes in a seat-tight manner, such that, in the case of a fluidic connection from the supply connection to the utility connection, a pressure reduction function is realized, and in the case of a fluidic connection from the utility connection to the tank connection, a pressure-limiting function is realized.
Pressure-regulating valves are frequently used in a hydraulic circuit for the purpose of converting a variable primary pressure, which is often applied from a pump or a hydraulic accumulator as the pressure source to a supply connection of the valve, into a constant, reduced secondary pressure. In addition, the increase in the secondary pressure at the assignable utility connection of the regulating valve resulting from external and application-specific influences is prevented with an additional pressure lease to an additional fluidic connection of the valve, commonly in the form of a tank connection or return connection. The design as a seat-tight pressure-regulating valve ensures the sealing of the connection from the primary pressure side to the regulating pressure side or from the regulating pressure side to the afore-mentioned tank connection or return connection of the valve. In this way, once a static regulating pressure has been obtained, an increase in this pressure is prevented by means of the sealing relative to the primary pressure side. The reduction in pressure by means of the relief function commences only once a maximum pressure level is exceeded. The seat-tight construction of a pressure-regulative valve differs from the slide construction, in which the opening cross sections of the through-flow directions are obtained by means of the axial displacement of a valve piston in a valve body provided with radial bores.
One example of this type of pressure-regulating valve is presented in EP 1 970 787 B1. This known pressure-regulating seat valve for hydraulic systems, in particular for machine tool clamping devices, is provided with a main seat arranged between a supply pressure connection and a regulating pressure connection in the form of a utility connection, to which main seat an upstream spring-loaded main closure element is assigned which, for the purpose of setting the regulating pressure by means of the main seat, can be mechanically loaded by means of a regulating piston which, downstream of the seat, is loaded by means of the regulating pressure against a regulating spring. Because in the known solution a discharge valve with a seat valve construction is arranged in a flow path between the regulating pressure connection and a discharge connection or tank connection, which discharge valve can be mechanically controlled to the discharge connection when the regulating pressure set by means of the regulating spring is exceeded until such time as the regulating pressure is restored, and because the activation of both the discharge valve and of the main closure element can be set by means of the regulating spring, this means that a three-way pressure-regulating seat valve is realized, which requires only a single setting opportunity for the regulating pressure setting, namely, for the preloading of the regulating spring. This is achieved in particular by means of the integration of the flow path to the discharge connection and of the discharge valve with a seat valve construction into the flow path, and with the single regulating spring which acts both for the discharge valve and the main seat valve.
On the basis of this prior art, the invention addresses the problem of producing a functionally-reliable pressure-regulating valve in an inexpensive manner, which pressure-regulating valve, in addition to a pressure reduction function, also realizes a pressure-limiting function, with the pressure difference between the respective reduced pressure and the pressure-limiting opening pressure being minimized in order to thus ensure an energy-saving pressure-regulating valve operation. In particular, a maximum regulating pressure variation is to be achieved due to the pressure sensitivity of the connected consumer.
This problem is solved by means of a pressure-regulating valve having the features of Claim 1 in its entirety.
Because, in accordance with the characterizing portion of Claim 1, the control part has a control rod with two control bodies which are kept at a distance from one another, one of which control bodies controls at least one fluidic connection between the supply connection and the utility connection and the other control body controls at least one fluidic connection between the utility connection and the tank connection, a 3-way pressure regulating valve is thus created which, with a functionally-reliable and inexpensive construction, expands a pressure reduction function with which it is provided to also include a pressure-limiting function. Both the pressure reduction function and the pressure-limiting function can be appropriately regulated by means of a single regulating pressure spring. The pressure-regulating valve according to the invention is preferably used in hydraulic clamping of machine tools and, thanks to the additional pressure-limiting function, it ensures maintenance of the clamping pressure in the case of pressure increases due to external influences.
Compared with the known comparable valve solutions, the valve according to the invention has the advantage that the so-called pressure offset or the pressure difference between the respective reduced pressure and the assignable pressure-limiting opening pressure of the valve is minimal, which results in an energy-saving operation and in particular, hydraulic consumers which are connected to the pressure-regulating valve, such as clamping pressure units in the case of machine tools, can be actuated in an unhindered and direct manner, which also represents a significant safety enhancement. Because the valve construction according to the invention is formed in a seat-tight manner, undesirable leaks during valve operation are avoided, and the respective workpiece is appropriately protected even when high clamping force is applied. In this way, leak losses cannot result in a corresponding clamping pressure loss in the hydraulic clamping of the machine tool.
Because, according to the invention, the control bodies of the control part which are respectively responsible for this are firmly connected to one another via a control rod and are kept at a distance from one another, both the above-mentioned pressure reduction function and the pressure-limiting function can be realized with only one control part in an installation space-saving manner, with the forced coupling of the two control bodies via the control rod ensuring a fail-safe operation.
Due to the direct coupling by means of the single-piece control part between the pressure-regulating seat in the valve housing and the pressure-limiting seat, no additional idle stroke is required in the valve piston via the control part with its control rod and the two control bodies in order to activate the pressure-limiting function. The above-mentioned pressure difference between regulated pressure and limited pressure in the sealing regulating position is minimal because no additional sealing force is required to overcome a certain idle stroke. However, in order to open the pressure-limiting function, the loss of the compressive force, which is transferred via the closing piston from the primary pressure side, must be compensated for.
In a particularly advantageous manner, a change in the seat diameter of the valve piston makes it possible to change the pressure difference until such time as the pressure-limiting function is activated.
The control part formed according to the invention with the control rod and the two control bodies which are kept at a distance from one another by means of the control rod thus create a double-action sealing element and, due to the gimbal-type mounting of the two control bodies in the form of spherical caps in the respective seat geometries of the assignable valve seats on the valve housing and on the valve piston, a tolerance insensitivity is produced with regard to form tolerance and positional tolerance of the valve components which are to this extent connected to one another. This ensures a high level of tightness for the pressure-reduction function and for the pressure-limiting function.
Furthermore, the gimbal mounting provided ensures that the critical loading case of the piston-type closing part with its two control bodies is reduced to pulsating compressive loads. This permits a reduction in the rod diameter of the control rod in the region of the seat feed-through in the valve housing and provides additional advantages in reducing the pressure losses in the case of unloaded through-flow of the pressure-regulating valve. It is also advantageous that the tank connection, return connection or discharge connection of the pressure-limiting function is arranged above the valve piston at the side on the valve housing, in which the valve piston is guided in a longitudinally displaceable manner. This makes it possible to apply atmospheric pressure to the spring side of the valve piston and thus to the spring chamber with the regulating pressure spring accommodated therein, so that to this extent the actual pressure-regulating function is thus virtually independent of the pressure in the discharge line, return line or tank line. The pressure existing in the latter line acts, as a compressive force, against the valve piston on the surface of the pressure-limiting seat, which is arranged in the region of the free front end of the valve piston, which in turn faces the control part.
The pressure-regulating valve according to the invention is explained in detail below with reference to an exemplary embodiment according to the drawings in which, in schematic and not to scale depictions,
The pressure-regulating valve depicted in
A control part 20 serves to actuate said connections or connection points, which control part is depicted magnified in
As is shown in particular in
The control rod 22 penetrates, at a radial distance, a transverse partition wall 32 in the valve housing 12 via a penetration point 34 which opens into the first valve seat 28 at its left-hand end when viewed in the direction of viewing of
The one control body 24 is supported at its left-hand end by means of a step 40 on an energy store in the form of a pressure spring 42, which is penetrated by the fluid supply at the supply connection 14 and the spring stiffness of which is significantly less than the spring stiffness of a regulating pressure spring 44, which permanently applies pressure to the valve piston 10 in each of its regulating positions and which likewise constitutes an energy store.
As can be seen in particular from the detail drawing according to
The two control bodies 24, 26 each have spherical shaped body sections in the form of partial spherical caps and in
The valve housing 10 has, in the region of the supply connection 14 and connected thereto in a fluid-conducting manner, a recess in the form of the first fluid chamber 36, into which a holding device 56 is inserted for receiving the pressure spring 42, on which the one control body 24 of the control part 20 is supported. The holding device 56 is formed as a receiving pot and is inserted via connecting bars (not depicted) into the fluid chamber 36 of the valve housing 12 in such a way that a radial distance is formed between the inner wall of the fluid chamber 36 and the outer wall of the holding device 56 which permits the entry of pressurized fluid in the direction of the valve piston 10. Furthermore, the holding device 56 has on its bottom side a through hole 58, which opens into a channel 60, which fully penetrates the holding device 56 viewed in the longitudinal direction. In the region of the dome-like broadening of the control body 24, this channel 60 is likewise correspondingly broadened and to this extent forms a cavity 62 for the purpose of receiving the control body 24.
If the valve piston 10 is, in accordance with the depiction of
The above-mentioned regulating pressure spring 44 for the valve piston 10 is guided, according to the depiction of
As can also be seen from
The regulating function of the pressure-regulating valve according to the invention can be graphically represented with the aid of the diagram of
The first quadrant I presents the regulated, in particular reduced pressure in a defined valve setting of the pressure-regulating valve according to the invention dependent on the volume flow. Upon transition into the second quadrant II, the delivery volume from the primary side 14 towards the secondary side 16 drops to zero. The closing operation of the regulating element which is responsible for this drop is realized with the seat-tight closing element 20 with the cap-shaped control bodies 24, 26. This ensures that, once the regulated pressure and the zero-volume flow intake are achieved at the secondary connection 16, no fluid can flow from the primary side 14 to the secondary side 16 and produce an undesirable pressure increase. If the pressure increases with a closed regulating element, the pressure-limiting function to the tank connection or discharge connection 18 opens in the second quadrant II. This pressure-limiting function also operates using a specified volume flow range.
This function has applications for example in hydraulic clamping of machine tools. The supply pressure of a hydraulic system is reduced to the desired clamping pressure, which is responsible for realizing the clamping of a workpiece by means of hydraulic cylinders. When the desired preloading of the cylinder is achieved, the control part 30 in the form of the first control body 24 seals the primary pressure side 14 (supply pressure side) relative to the secondary pressure side (clamping pressure side) 16. During the machining of the thus firmly clamped workpiece, temperature increases or machining forces can result in pressure increases on the secondary pressure side 16. This pressure increase is dissipated without an additional valve via the pressure-limiting function in the pressure-regulating valve according to the invention. The important thing here is that the regulated primary pressure at the supply connection 14 and the opening pressure of the pressure-limiting function can both be set by means of a spring, in this case the regulating pressure spring 44, which spring acts upon the regulating element in the form of the valve piston 10 and pushes against the primary pressure. The goal here is to maintain as low as possible the pressure difference between regulated pressure at zero-volume flow and the opening pressure of the pressure-limiting function, irrespective of the setting pressure of the valve according to the invention, which is represented in a schematic manner in
By comparison with the prior art, the pressure-regulating valve solution according to the invention thus provides a valve in which the shown pressure offset range 82 between reduced pressure and pressure-limiting opening pressure is minimal, and this constitutes a significant safety feature when using the pressure-regulating valve according to the invention, in particular in the context of hydraulic clamping of machine tools. The advantages of the valve thus include the energy efficiency when used in hydraulic clamping of machine tools due to the seat-tight construction by comparison with pressure-regulating valves with a slide construction, in particular no losses resulting from long-lasting leak flow occur in the solution according to the invention.
Number | Date | Country | Kind |
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10 2015 007 689.2 | Jun 2015 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2016/000744 | 5/6/2016 | WO | 00 |