WO2013131881A1

WO2013131881A1 - Hydrostatic displacement machine

Info

Publication number: WO2013131881A1
Application number: PCT/EP2013/054346
Authority: WO
Inventors: Thomas Fischer; Rudolf Kunze; Lorenz Lippert; Brigitte BERGMANN; Adrian Jerchen
Original assignee: Robert Bosch Gmbh
Priority date: 2012-03-08
Filing date: 2013-03-05
Publication date: 2013-09-12
Also published as: DE102013203701A1

Abstract

Disclosed is a hydrostatic displacement machine having cylinder-piston units. A high and a low pressure valve is in each case assigned to these cylinder-piston units, wherein the high pressure valve is a slide valve which has a valve slide guided in a spool bore. The slide is advantageously designed as a hollow slide.

Description

Hydrostatic positive displacement machine

description

The invention relates to a hydrostatic displacement machine according to the preamble of patent claim 1.

In conventional displacement machines, which may be embodied, for example, as radial piston or as axial piston machines, the control of the inlet and the outlet or the connections to the high and low pressure of the individual cylinder-piston units takes place mechanically. In the case of an axial piston pump, for example, two pressure kidneys are used, via which the connections to the high-pressure side and to the low-pressure side open during a certain region of the circular path and thus during a certain stroke section of the cylinder-piston units. In the case of radial piston pumps, one mechanical high-pressure valve and one mechanical low-pressure valve are provided per cylinder-piston unit. The high-pressure valve of each unit, for example, always opens when a certain pressure built up in the respective cylinder is exceeded, so that the pressure-increased pressure medium can flow to the high-pressure side of the pump.

The publication WO 2008/012558 A2 discloses valve-controlled displacement machines which are digitally adjustable. In this case, each cylinder-piston unit is associated with an electrically operated low-pressure valve and an electrically operated high-pressure valve.

Thus, the units can be controlled separately in pump mode, motor mode and in a so-called idle mode. Through the idle mode, individual units can be deactivated or powerless by permanently opening the low-pressure valve and by permanently closing the high-pressure valve. Thus, the volume flow or the rotational speed of the positive displacement machine can be reduced. The document EP 2 187 104 B1 shows a digitally adjustable radial piston machine with six cylinder-piston units, which are arranged in a radial plane, wherein pistons of the cylinder-piston units are supported on an eccentric shaft. Each cylinder-piston unit is associated with an actively controllable low-pressure valve and a passively controllable high-pressure valve. The valves are in one common

one-piece housing used.

The authors SH Salter, JRM Taylor and NJ Caldwell disclose a digitally adjustable radial piston machine with several radial planes, in the document "Power conversion mechanisms for wave energy" from Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment. Each cylinder-piston unit is associated with an actively controllable low-pressure valve and an actively controllable designed as a check valve high-pressure valve, wherein the valves are arranged in a common housing.

DE 10 2010 004 808 A1 likewise discloses a digitally adjustable radial piston machine. A respective cylinder-piston unit is hereby assigned, in addition to an actively controllable low-pressure valve and an actively controllable high-pressure valve, a passive high-pressure valve which is arranged parallel to the actively controllable high-pressure valve. This results in that the radial piston machine can be used independently of the actively controllable high-pressure valve in a pump operation. The actively controllable high pressure valve has a valve spool which is slidably guided in a spool bore of a valve housing. Via a valve spring of the valve spool is acted upon in the direction of a closed position with a spring force, wherein in the closed position, a pressure medium connection between a working space of the cylinder-piston unit and a high-pressure channel is controlled. Via an electromagnetic actuator of the valve spool can be brought into its open position, in which the working space is connected to the high pressure passage. Further, the valve spool limits with its end faces valve chambers which are connected to leakage lines, whereby the valve spool is pressure balanced in its axial direction.

The disadvantage of such a high-pressure valve is that a mass of the valve spool is extremely large, which is why comparatively high forces are necessary to move the valve spool or to switch. In case of a shift in the tilschiebers this displaced with its front side oil volumes from the decreasing valve space on the leakage line, which disadvantageously has a strong damping result. Due to the high mass of the valve spool and the strong damping, its dynamics are very low. Overall, such a high pressure valve leads to comparatively long switching times.

In contrast, the invention has the object to provide a positive displacement machine, the high pressure valve has a high dynamics.

This object is achieved by a hydrostatic displacement machine according to the features of patent claim 1.

Other advantageous developments of the invention are the subject of further subclaims.

According to the invention, a hydrostatic displacement machine, in particular a digitally adjustable radial piston machine, cylinder-piston units. These are each assigned a high and a low pressure valve. The high pressure valve is designed as a slide valve, which has a guided in a slide bore valve slide. This is designed as a hollow slide.

This solution has the advantage that the valve slide has a comparatively low mass due to its design as a hollow slide. On the one hand, this results in comparatively small forces being necessary for moving the valve spool, and thus the high-pressure valve has a comparatively high degree of dynamics. An inventive high-pressure valve thereby has very short switching times, for example between 2 and 3 ms. It has been shown that such a valve slide despite its lightweight construction as a hollow slide, high pressures, for example, 450 bar, withstands and can be used in a positive displacement machine.

In a further embodiment of the invention, the hollow slide is designed like a bush, whereby it has very little mass.

Preferably, the hollow slide has a bottom which is arranged towards a, in particular electromagnetic, actuator of the slide valve. This has the advantage that the bottom has on its side facing away from the actuator side mounting space for a valve spring, whereby the high-pressure valve can be made extremely compact, in contrast to the input explained prior art

DE 10 2010 004 808 A1 in which the valve spring engages outside of the valve slide at its end face. The high pressure valve is thus designed extremely compact, but still can control a comparable flow rate as the said prior art.

In the bottom of the hollow slide one or more openings may be formed for volume balance of bottomed valve spaces. In this way, at least a portion of an oil volume can be displaced in the direction of the decreasing valve space to the increasing valve space at a displacement of the valve spool. Furthermore, a face of the bottom which displaces the oil volume has a comparatively small area through the one or more openings. The hollow slide is thus less dampened by the one or more openings compared to the input explained prior art and thus has a high dynamics.

Preferably, at least one valve chamber is connected on one side of the bottom via a channel in a valve housing of the high-pressure valve with a tank space, whereby the valve chamber is open to the outside to the tank space. As a result, an additional volume of oil to the tank space can be displaced from the valve chamber. Furthermore, it is possible to compensate for a change in a free volume in the slide bore caused by an immersion and removal of a plunger of the actuator actuating the valve slide.

Preferably, both valve chambers are connected on both sides of the bottom via a respective channel on the valve housing with a tank space, whereby in any direction of movement of the valve spool with low resistance oil volumes can be displaced into the tank space.

The channel may simply be designed as a groove introduced into a surface of the valve housing, which preferably opens into the slide bore. For opening and controlling a pressure medium connection between cavities formed in the slide bore, in particular inflow and outflow cavities, the hollow slide has an outer circumferential annular groove. Here, the hollow slide has seen in the axial direction outside the annular groove to its free end a larger inner diameter, as in the region of the annular groove. This leads to the fact that the mass of the hollow slide is further reduced.

In a further embodiment of the invention, the high-pressure valve may have a separate valve housing with a continuous slide bore. As a result, the high-pressure valve forms a structural unit that can be preassembled and can be tested independently of the rest of the displacement machine.

Preferably, a valve spring, in particular a helical spring, of the high-pressure valve is supported and centered on the valve housing via a metal sheet. As a result, the valve spring within the hollow slide, for example, be aligned so that it is spaced from an inner circumferential surface of the hollow slide.

In order to increase the handling of the valve spring together with the sheet, for example, during assembly, the sheet, in particular by an axial projection, with the valve spring force, material and / or positive, in particular by pressing, are connected.

The openings in the bottom of the hollow slide are preferably device-technically easily insertable continuous axial bores, which are arranged in particular on a common bolt circle.

In order for the valve spring formed, in particular as a helical spring, to lie substantially uniformly and over a large area on the bottom of the valve slide and to act on it with a spring force, the openings in the bottom of the valve slide are arranged substantially inside the valve spring, as seen in the radial direction.

Preferably, the valve spool has at least one outer circumferential relief groove whereby an oil film between the valve spool and the spool bore is evenly distributed. Furthermore, the at least one relief groove has a centering effect on the valve spool.

In order to further reduce frictional forces of the valve spool within the spool bore, at least a portion of the outer lateral surface of the valve spool may have a slip coating.

In the following, a preferred embodiment of the invention is explained in more detail with reference to drawings.

Show it

FIG. 1 shows a front view with an outbreak of a radial piston machine according to an exemplary embodiment,

FIG. 2 shows a simplified perspective illustration of the radial piston machine according to the exemplary embodiment,

3 shows an enlarged view of a detail in the outbreak region of the radial piston machine from FIG. 1, FIG.

FIG. 4 shows a schematic cross-sectional view of a valve block of the radial piston machine according to the exemplary embodiment,

FIG. 5 shows an enlarged detail of the valve block of FIG. 4 in the region of a low-pressure valve,

FIG. 6 shows an enlarged detail of the valve block from FIG. 4 in the region of a high-pressure valve,

FIG. 7 is a plan view of the valve block from FIG. 4,

FIG. 8 shows a side view of a valve slide according to the invention,

FIG. 9 shows a front view of the valve slide according to the invention,

Figure 10 is a sectional view of the valve spool along a sectional plane A-A through the valve spool of Figure 9 and

FIG. 11 shows an enlarged detail of the valve slide from FIG. 10.

According to Figure 1, a positive displacement machine according to the invention in the form of a radial piston machine 1 is shown, which is digitally adjustable. Such a radial piston machine is used in particular in the automotive sector for road vehicles, which have a hybrid technology on a hydraulic basis. The radial piston machine 1 has an annular central part 2, which can be seen in Figure 1 by the outbreak of the front view of the radial piston machine 1. The central part 2 surrounds an eccentric shaft 4, which extends substantially coaxially to the central part 2. The eccentric shaft 4 has four eccentrics 6 to 12, which are arranged one behind the other in the axial direction of the eccentric shaft 4. On the eccentric shaft 4 are based on the eccentric 6 to 12 thus in four radial planes from cylinder-piston units from where in Figure 1 for the sake of simplicity, only a single cylinder-piston unit 14 of the first radial plane - in the outbreak - is shown whose piston 16 is supported on the foremost eccentric 6 in FIG. The eccentric shaft 4 has at its end portion a toothing 17 for a toothed shaft connection.

A respective cylinder-piston unit 14 is associated with an actively controllable high-pressure valve 18, an actively controllable low-pressure valve 20 and a passive high-pressure valve 22. The actively controllable high and low pressure valves 18 and 20 are each arranged in a common valve block 24 which is fixed to the central part 2 and serves as a valve housing.

In a radial plane of the radial piston engine 1, six cylinder-piston units 14 are provided, thus a total of six valve blocks 24 are arranged on the central part 2 per radial plane. In FIG. 1, the valve blocks 24 and 28 adjacent to the valve block 24 can be seen in sections. The cylinder-piston units can be activated or deactivated via the high and low pressure valves 18 and 20 for setting a volume flow of the radial piston machine 1.

Furthermore, each cylinder-piston unit 14 of a radial plane of the radial piston machine 1 is associated with an axially extending high-pressure channel 30 to 40, which are seen in the central part 2 in a radial plane each introduced between two cylinder-piston units. Thus, according to the number of cylinder-piston units in a radial plane, a corresponding number of evenly distributed on a bolt circle high-pressure channels provided. The axial-direction successively arranged cylinder-piston units of the radial planes of the radial piston engine 1 are connected to the same high-pressure channel.

FIG. 2 shows the radial piston machine 1 from FIG. 1 in a perspective illustration without a substantially circular-cylindrical, low-pressure region. as tank-limiting jacket 42, see Figure 1, shown. According to FIG. 2, four radial planes 44 to 50 of the radial piston machine 1 with cylinder-piston units can be seen. The central part 2 is designed here as a monoblock. It is conceivable that the central part has cylinder-piston units in only a single radial plane, wherein the central part is then designed as a disk. Together with the valve blocks it would then form a total disc.

The central part 2 is cylindrical and has a cross-section substantially as an equilateral hexagon formed outer lateral surface 52. By this configuration, the central part 2 has six side surfaces, on each of which four valve blocks 24 are arranged in series one behind the other, wherein the better Darstellbarkeit half only a valve block in the figure 2 is provided with a reference numeral. If the radial piston engine per radial plane more or less cylinder-piston units, so the central part would have more or fewer side surfaces accordingly.

Furthermore, an electrical contacting of the electromagnetically actuated actively controllable high and low pressure valves 18 and 20 can be seen in FIG. For this purpose, the high-pressure and low-pressure valves 18 and 20 arranged in series one behind the other are each connected to a common contacting strand 54, which each extend between the rows.

According to FIG. 3, a section of the radial piston machine 1 in the region of the outbreak from FIG. 1 is shown enlarged. In the following, the embodiment of the central part 2 with the valve block 24 will be described, wherein the central part 2 in the region of the valve blocks, not shown, and the valve blocks, not shown, are designed accordingly.

It can be seen that the cylinder-piston unit 14 is supported outwardly on a screwed into a radial bore 55 of the central part 2 socket 56. The piston 16 in turn is supported on the eccentric shaft 4 in a conventional manner. For the support of the cylinder-piston unit 14, for example, a spring, not shown, is provided which biases the piston 16 against the eccentric shaft 4 and the cylinder 58 against the bush 56. The cylinder 58 is pivotally mounted in the sleeve 56 by the cylinder 58 has a convex in cross-section annular end face 60 and the sleeve 56 has a concave cross-section annular end face 62, wherein the annular end faces 60 and 62 slidably abut each other. The bushing 56 extends in the radial direction of the radial piston machine 1 from the outside of the central part 2 ago about to half of the radial bore 55. The cylinder 58 in turn is located for the most part in the radial bore 55th

The bush 56 emerges with a bushing collar 64 that protrudes radially from the central part 2 into a connecting bushing 66 screwed into the valve block 24. In the outer circumference of the bushing collar 64 of the bushing 56 is an annular groove for receiving sealing means, in particular an O-ring, introduced. The bush 56 serves in addition to the support of the cylinder-piston unit 14 as a connecting channel between the valve block 24 and a limited by the cylinder 58 and the piston 16 working space 68th

The radial bore 55 is seen centrally in the sectional plane of Figure 3 seen from the side surface 70 ago introduced into the central part 2. Approximately offset parallel to the radial bore 55 to the right in Figure 3, a blind hole 72 is also introduced from the side surface 70 ago in the central part 2, which intersects the high pressure passage 30. The blind hole 72 serves to connect the high-pressure channel 30 with a high-pressure branch channel 74 formed in the valve block 24. Into the blind bore 72, a check valve 76 is used as a passive high-pressure valve. Whose valve body 78 is tensioned by a spring against a valve seat of the check valve 76. In a pressure medium flow direction from the high-pressure branch passage 74 in the direction of the high-pressure passage 30, the valve body 78 can lift off the valve seat. The high-pressure branch channel 74 is connected to the working chamber 68 of the cylinder-piston unit 14 in pressure medium connection, whereby in the pump operation of the radial piston machine 1 upon reaching a predetermined pressure in the working chamber 68, the check valve 76 can be opened automatically.

The valve block 24 together with the low-pressure valve 20 and the high-pressure valve 18 will be explained in more detail below with reference to FIG. For connecting the valve block 24 to the side surface 70 of the central part 2 of Figure 3, this has a connection surface 80. From this forth is seen in cross section approximately centrally a valve body 24 passing through stepped bore 82 introduced. Starting from the connection surface 80 is a first bore portion 84 of the stepped bore 82 with a Provided internal thread into which the socket 66 is screwed. A screwed-in portion of the connecting sleeve 66 is radially stepped back, wherein this then has an annular end face 86 facing the valve block 24, which substantially bears in the screwed-in state on a countersink base surface of a countersink 88 introduced into the valve block 24. The socket 66 has a substantially cylindrical inner surface 90 having rounded edges. In the space spanned by the inner lateral surface 90, the bushing 56 of FIG. 3 sealingly engages with its bushing collar 64 and extends approximately as far as a rounded edge 92 of the connecting bushing 66 facing the low-pressure valve 20. The connection bushing 66 is in the position of the low-pressure valve 20 pointing away side introduced a counterbore 94, whereby an outer annular end face 96 is formed, which may rest against the bush 56 of Figure 3 in the assembled state.

The stepped bore 82 is seen in the axial direction after the threaded portion 84 of the high-pressure branch passage 74 passes through. Thus, the working space 68 from FIG. 3 is connected via the bushing 56 and the connecting bushing 66 to the high-pressure branch channel 74.

The stepped bore 82 has seen in the axial direction after the high-pressure branch channel 74, a smaller diameter than the threaded portion 84 having receiving stage 100 for receiving a valve housing 102 of the low pressure valve 20. After the receiving stage 100 is then a smaller diameter than the receiving stage 100 having bore stage 104 is provided , which then opens in the side facing away from the connection surface 80 top 106 of the valve body 24.

The valve housing 102 of the low-pressure valve 20 is inserted into the receiving stage 100 from the connection surface 80 and has an axial length which corresponds approximately to the axial length of the receiving stage 100. Thus, the valve housing 102 adjacent to about the stepped bore 82 passing through the high-pressure branch passage 74 at. From an outer circumferential surface of the valve 102 ago an annular groove 108 is inserted into the valve housing 102 for the arrangement of an O-ring seal. The valve housing 102 further has an axial projection 110 extending in the direction of the bore step 104 of the valve body 24, which projects into the bore step 104. In the middle, the valve housing 102 is approximately coaxial with the stepped bore 82 penetrated by a guide bore 1 12, in which a guide pin 1 14 is slidably guided. This projects with its two end sections from the valve housing 102. At its in the direction of the connection surface 80 facing end portion 1 16 a plate-shaped valve body 1 18 is fixed, which is arranged approximately coaxially with the guide pin 1 14. The valve body 1 18 has an annular sealing surface 120 facing the valve housing 102, which sealingly bears against an underside 122 of the valve housing 102 pointing away from the upper side 106 of the valve block 24. In the position shown in Figure 4, the sealing surface 120 is spaced from the bottom 122, whereby the low-pressure valve 20 is in its open position. As a result, three kidney-shaped low-pressure channels 124 introduced into the valve housing 102 are fluidically connected to the high-pressure branch channel 74. The low-pressure channels 124 are arranged on a pitch circle, enforce the valve housing 102 in the longitudinal direction completely and include the guide bore 1 12 of the valve housing 102. If the sealing surface 120 at the bottom 122 on, so a pressure medium connection between the low-pressure channels 124 and the high-pressure branch passage 74 is interrupted the low pressure valve 20 is closed. The low-pressure channels 124 each open into a respective kidney-shaped low-pressure channel 126 introduced into the valve block 24. Thus, three low-pressure channels 126 are likewise provided in the valve block 24, only one of which can be seen in FIG. The low pressure passages 126 are open toward the bore step 104, as seen in the radial direction of the low pressure valve 24, and have the same axial length as the bore step 104, thereby opening into the top 106 of the valve block 24. The low-pressure channels 126 are thus connected to the low-pressure space of the radial piston machine 1 bounded by the jacket 42 from FIG.

To actuate and move the guide pin 1 14 together with the valve body 1 18, an electric actuator 128 is provided. This is arranged in a cup-shaped actuator housing 130 from the opening side of the axial projection 1 10 of the valve housing 102 is immersed and this determines. The actuator housing 130 extends through the bore stage 104 and protrudes from the valve block 24. In the actuator housing 130, a magnetic coil 132 is arranged, which surrounds an axially displaceable armature 134. The armature 134 is connected to the guide pin 1 14. For the sake of clarity, a more detailed explanation of the configuration of the actuator 128 of the low-pressure valve 20 is given with reference to FIG. 5, which shows a section of the valve body 24 from FIG. 4 in the region of the low-pressure valve. According to FIG. 5, the guide pin 1 14 projects with its end portion 136 out of the valve housing 102 in the direction of the actuator 128. The end portion 136 is thereby expanded radially with a radial collar 138, which is engaged behind by an inner collar 139 formed in a through bore 140 of the magnet armature 134.

A valve spring 142 arranged approximately coaxially with the guide pin is supported on a pole piece 144 encompassed by the magnet coil 132 and fixed in the actuator housing 130, dips into the through bore 140 of the magnet armature 134 and acts on an end face 146 pointing in the direction of the upper side 106 of the valve block 24 of the guide pin 1 14 with a spring force.

The armature 134 is disposed axially displaceable between the valve housing 102 and the pole piece 144. The valve spring 142 is supported on the pole piece 144 via a step of a continuous stepped bore 150 of the pole piece 144 from. The pole piece 144 passes through the actuator housing 130 axially in its bottom surface, whereby the stepped bore 150 of the pole piece 144 is connected to the low-pressure region of the radial piston machine 1 bounded by the sheath 42 of FIG. An intermediate space 152 formed between the pole piece 144 and the magnet armature 134 is thus likewise connected to the low-pressure region via the stepped bore 150 of the pole piece 144. For pressure equalization of axial surfaces of the armature 134 this is penetrated by a plurality of axial bores 154, which are connected to the intermediate space 152. For electrical contacting of the actuator 128, this, outwardly cantilevered contact lugs 156.

In the position shown in FIG. 5, the low-pressure valve 20 is in its open position. Here, the solenoid 132 of the actuator 128 is de-energized, whereby the guide pin 1 14 is moved together with the armature 134 away from the pole piece 144 by a spring force of the valve spring 142. To limit a displacement of the guide pin 1 14 of the armature 134 is located on the axial projection 1 10 of the valve housing 102 at. To close the low-pressure valve 20, the solenoid 132 of the actuator 128 is energized, whereby the armature 134 is moved by a magnetic force of the solenoid 132 against the spring force of the valve spring 142 away from the valve housing 102 in the direction of the pole piece 144. The armature 134 takes on its inner collar 139, the guide pin 1 14 via the radial collar 138 with. The valve body 118 of the low-pressure valve 20, see also FIG. 4, arrives here with its ner sealing surface 120 to the underside 122 of the valve housing 102, thereby sealing the low-pressure channels 124 to the high-pressure branch passage 74.

The designed as a slide valve high pressure valve 18 of Figure 4 is added to the left parallel to the low pressure valve 20 in the valve block 24, wherein this is used as a valve housing for the high pressure valve 18. The high pressure valve 18 has a sleeve-shaped designed as a hollow slide valve according to the invention 158, which is guided in a slide bore 160 slidably. The valve spool 158 is explained in more detail below in the figure description of Figures 8 to 1 1.

The slide bore 160 passes completely through the valve block 24 approximately at a parallel distance from the stepped bore 82 of the low-pressure valve 20, wherein the valve block 24 in the region of the slide bore 160 is approximately half as thick as in the region of the stepped bore 82. The slide bore 160 thus extends from the connection surface 80 approximately in the longitudinal direction as far as the central region of the receiving step 100 of the stepped bore 82. An inlet cavity 162 and a discharge cavity 164 open out into the slide bore 160 and are arranged offset relative to one another in the longitudinal direction of the slide bore 160 are. With the valve spool 158 while a pressure medium connection between the cavities 162 and 164 is opened and closed. The Anströmhöhlung 162 is disposed between the terminal surface 80 of the valve block 24 and the Abströmhöhlung 164. The cavities 162 and 164 introduced radially into the slide bore 160 completely surround them. The upper outflow cavity 164 in FIG. 4 is connected to the high-pressure branch channel 74. The lower Anströmhöhlung 162, however, is connected to not shown in the figure 4 approximately coaxially with the slide bore 160 in the direction of the connection surface 80 of the valve block 24 extending channels. These continue over the connection surface 80 in the central part 2 of FIGS. 1 and 3 and are connected to the high pressure passage 40 arranged adjacent to the valve block 24. Thus, the working space 68 of the cylinder-piston unit 14 in Figure 3 via the check valve 76 with the high pressure passage 30 and via the high pressure valve 18 of Figure 1 to the high pressure passage 40 are fluidly connected.

A more detailed explanation of the high-pressure valve 18 is made with reference to FIG. 6, which shows a detail from FIG. 4 in the region of the high-pressure valve 18. According to Figure 6 is the Valve spool 158 designed as a hollow slide sleeve-like, wherein it is configured open towards the connection surface 80 of the valve block 24 and toward the top 106 and toward an electromagnetic actuator 180 has a bottom 166. The valve spool 158, which is explained in more detail in the description of Figures 8 to 1 1, has a formed from its outer circumferential surface annular groove 168, whereby a control edge 170 is formed. With this a pressure medium connection between the cavities 162 and 164 is opened and closed. In the position shown in Figure 6, the valve spool 158 is in a closed position in which the pressure medium connection between the cavities 162 and 164 is closed. The valve spool 158 is acted upon in the direction of its closed position by a valve spring 172 designed as a helical spring with a spring force. This is supported on a spring plate 174 in the form of a sheet, which abuts in the assembled state of the valve block 24 on the side surface 70 of the central part 2 of Figure 3. The valve spring 172 extends from the spring plate 174 through the hollow valve spool 158 and acts on this via its bottom 166 with a spring force. The spring plate 174 has centrally an axial or centering projection 176 for centering the valve spring 172. It is conceivable to press the spring plate 174 with the valve spring 172, in particular the fact that the centering projection 176 non-positively dips into the valve spring 172.

In the closed position of the high-pressure valve 18 shown in FIG. 6, the valve slide 158 is supported with its bottom 166 on a pole piece 178 of an electromagnetic actuator 180. The pole piece 178 has an end portion 182, the sections seen in the longitudinal direction in the slide bore 160, see Figure 4, immersed. Subsequent to the end section 182, the pole piece 178 is widened with a radial collar 184 and is supported thereon by a cup-shaped actuator housing 186 in the radial and axial directions. The actuator housing 186 is bolted to the valve block 24 via a fastener 188. Furthermore, the actuator housing 186 is configured open toward the valve slide 158 and has a countersink 190 introduced from this side, against which the pole piece 178 is supported with its radial collar 184. The pole piece has seen after the radial collar 184 in the longitudinal direction another end portion 192 which is encompassed by a magnetic coil 194. An end face 196 of the pole piece 178 pointing away from the valve slide 158 serves as a stop face for a magnet armature 198 which can be displaced in the longitudinal direction in the actuator housing 186. Via this valve slide 158 is moved into its open position. pushed by the armature 198 engages via a plunger 200 on the bottom 166 of the valve spool 158. According to FIG. 4, the plunger 200 is guided in a guide bore 202 of the pole piece 178, which passes completely through the pole piece 178. The plunger 200 further has an armature 198 penetrating end portion 204 which is radially stepped back, whereby an annular valve face 158 facing away from the annular end face 206 on the plunger 200 is formed, against which the armature 198 for moving the plunger 200.

In the closed position of the high-pressure valve 18 according to FIG. 4, a gap 208 is connected between the magnet armature 198 and the pole piece 178, which is connected to the low-pressure region of the radial piston machine 1 via a channel formed in the actuator 180 from FIG. 6 and through through bores 210 introduced in the actuator housing 186.

According to FIG. 4, the bottom 166 of the valve slide 158 is limited on the magnet side, ie towards the actuator 180, see also FIG. 6, a valve space 21 1, which has a minimal volume in the position of the valve slide 158 shown in FIG. On the spring side, the valve spool 158 delimits a further valve space 213, which has its maximum volume in FIG.

Via a channel formed as a groove 212, the spring-side valve chamber 213 is connected to the tank space or low-pressure region of the radial piston machine 1. The groove 212 is introduced into the surface or connection surface 80 of the valve block provided as a valve housing 24 and extends radially to the high pressure valve 18. It opens on the one hand in the slide bore 160 and on the other hand in an obliquely to the connection surface 80 formed side surface 215 of the valve block 24. Die Nut 212 is limited in the assembled state of the valve block 24 on the connection surface side according to Figure 3 of the central part 2.

The magnet-side valve chamber 21 1 is also connected via a groove formed as a channel 214 with the tank space. This is from the top 106 ago approximately radially to the slide bore 160 and approximately at a distance parallel to the groove 212 in the valve block 24 is used and flows on the one hand in the slide bore 160 and the other in a subsequent to the obliquely formed side surface side surface 217th Die Nut 214 wird in the slide bore 160 in an inserted into the pole piece 178 th and to the valve chamber 21 1 open transverse groove 216 away.

In the bottom 166 of the valve spool 158 openings in the form of axial bores 218 are introduced, via which the valve chambers 21 1 and 213 are connected.

Through the axial bores 218 in the bottom 166, a displacement of the valve spool 158, a volume balance between the valve chambers 21 1 and 213 takes place by the shortest route. This has an extremely low damping of the valve spool 158 result. Through the grooves 212 and 214, there is an additional compensation of the change in the free volume in the slide bore 160 caused by the insertion and removal of the plunger 200.

According to FIG. 6, the actuator 180 of the high-pressure valve 18 is electrically contacted via contact lugs 220.

According to FIG. 4, the high-pressure branch channel 74 extends from the pressure chamber 164 via the stepped bore 82 of the low-pressure valve 20 and subsequently along a curve to the connection surface 80. An orifice 222 of the high-pressure branch channel 74 is introduced from a valve block 24 from the connection surface 80 Ring groove 224 embraced to receive an O-ring seal.

In the figure 7 is a plan view of the valve block 24 of Figure 4 is shown. Here, the fastener 188 of Figure 6 can be seen. This is designed plate-shaped and has a recess 226, via which the fastening element 188 surrounds the actuator housing 186. The fastening element 188 rests on an outer collar 228 of the actuator housing 186 and is fastened to the valve block 24 via two screws 230. Furthermore, the groove 214 can be seen in FIG. 7, which extends approximately centrally in the longitudinal direction of the valve block 24 as far as the slide bore 160 in FIG. In an upper side of the actuator housing 186 of the high-pressure valve 20, three kidney-shaped recesses 232 are introduced. These are used according to the figure 6 for connecting a gap 234 with the low pressure region of the radial piston machine 1, wherein the gap 234 from the actuator housing 186 and a side facing away from the valve spool 158 side of the armature 198 is limited.

In the area of the low-pressure valve 20, the valve block 24 has a cylindrical outlet. Section 236, see also Figure 4. In this, the kidney-shaped low-pressure channels 126 are formed. Furthermore, in the cylindrical portion 236 three threaded bores 238 are introduced approximately between the low-pressure channels 126 in the axial direction, which serve to attach an electrical contact for the contact lugs 156 and 220.

The valve block 24 is fastened to the central part 2, see FIG. 3, by way of screws via four through-bores 240 which are introduced from the upper side 106 in the latter.

For centering the valve block 24 on the central part 2, a centering pin 242 is provided in accordance with FIG. This is inserted from the connection surface 80 of the valve block 24 ago in this and immersed in a mounting of the valve block 24 in a corresponding center hole of the central part 2 a.

The valve slide 158 according to the invention, see also FIG. 4, will be explained in more detail below with reference to FIGS. 8 to 11. According to FIG. 8, the annular groove 168 is encircling from an outer circumferential surface 244 of the valve slide 158. This has a, viewed in the axial direction of the valve spool 158, in cross-section substantially circular cylindrical surface portion 246. The surface portion 246 is followed in the direction of a free end 248 of the valve spool 158 a further surface portion 250, which extends to the outer surface 244 and in Cross section has a radius. The middle surface portion 246 is followed in the direction of the bottom 166 of the valve slide 158 by a first surface section 252 having a radius in cross-section and a second surface section 254 having an approximately frustoconical outer surface. The annular groove 168 subdivides the outer lateral surface 244 into a lateral lateral surface section 256 and a lateral surface portion 258 on the side of the free end 248 of the valve spool 158. The lateral surface portion 258 on the side of the free end 248 is seen approximately in the longitudinal direction of the valve spool 158 three times as wide as the bottom lateral surface portion 256th

In the bottom-side lateral surface portion 256, two circumferential, axially spaced relief grooves 260, 262 are introduced. Two further, circumferentially spaced relief grooves 264 and 266 are introduced into the lateral surface portion 258, which are arranged towards the free end 248 of the valve spool 158. The relief grooves 260 to 266 are thus introduced in the edge region of the valve slide 158 in the outer circumferential surface 244 seen in the axial direction. By this, an oil film between the valve spool 158 and the spool bore 160 of Figure 4 is evenly distributed, whereby a friction of the valve spool 158 is reduced. Furthermore, the relief grooves 260 to 266 have the effect of centering the valve spool 158 in the spool bore 160.

In the front view in Figure 9 on the valve spool 158, the axial bores 218 of Figure 4 can be seen. These are evenly distributed on a common bolt circle 268. Overall, five axial bores 218 are introduced into the valve slide 158.

FIG. 10 shows, in a longitudinal sectional view along the sectional plane AA from FIG. 9, an inner lateral surface 270 of the valve slide 158. A width of the bottom 166 seen in the axial direction corresponds approximately to a width of the lateral surface portion 256 of Figure 8. From the bottom 166 extending from the inner surface 270 has a substantially circular cross-section surface portion 272, which has the smallest inner diameter of the valve spool 158. This extends approximately in the axial direction to the central surface portion 246 of the annular groove 168 of Figure 8. The inner diameter of the surface portion 272 corresponds to approximately an outer diameter of the valve spring 172 of Figure 6, whereby it is centered with its bottom end portion within the valve spool 158. Starting from the surface portion 272, the inner lateral surface 270 widened slightly with a likewise substantially circular cross-section surface portion 274. As a result, then the inner lateral surface 270 with the exception of the bottom-side surface portion 272 spaced from the valve spring 172 of Figure 6 in the radial direction. The surface portion 274 then extends in the axial direction approximately to the end of the annular groove 168. After the annular groove 168, the inner circumferential surface 270 widened with a frusto-conical surface portion 276, wherein a width of this surface portion 276 seen in the axial direction corresponds to about one third of the lateral surface portion 258 of Figure 8 , Subsequent to the surface section 276, the inner lateral surface 270 has a surface section 278 which is substantially circular in cross-section and has the largest inner diameter. The valve spool 158 thus has in the axial direction outside of the annular groove 168 to its free end 248th towards a larger inner diameter than in the region of the annular groove 168, resulting in a comparatively low mass of the valve spool 158.

Seen in the radial direction between the bottom-side surface portion 272 and the axial bores 218, one of which can be seen in the figure, in the valve spool 158 to the free end 248 facing annular surface 280 is formed. Preferably, the valve spring 172 from FIG. 6 is essentially supported on this annular surface 280, as a result of which a spring force is transmitted comparatively uniformly to the valve slide 158.

FIG. 11 shows an enlarged section A of the valve slide 158 from FIG. Here, a cross section of the relief groove 266 can be seen. As seen in the axial direction, the relief groove 266 broadens in the radial direction with two frustoconical wall surfaces 284 and 286. As seen in the axial direction, these relief grooves have approximately the same width. A distance of the wall surfaces 284 and 286 thus increases in the radial direction.

In the following, the operation of the radial piston machine 1 will be explained. In the pump operation of the radial piston machine 1, the cylinder-piston unit 14 of FIG. 3 is sucked in by pressure from the low-pressure region via the opened low-pressure valve 20 in the suction stroke, ie in the direction of the increasing working space 68. In this case, pressure medium flows via the low-pressure channels 126, see FIG. 4, via the low-pressure channels 124, via the connection socket 66 and the socket 56, see FIG. 3, into the working space 68. The high-pressure valves 18 and 22 are closed in this case. In the displacement stroke of the piston 16 of the cylinder-piston unit 14, the pressure medium with the high pressure valve 18 closed, see Figure 4, and closed low pressure valve 20 via the high-pressure branch passage 74, see Figure 3, via the check valve 76 in the high-pressure passage 30 promoted.

In engine operation, the piston 16 is acted upon by a high pressure in a stroke movement in the direction of the increasing working space 68 of Figure 3. For this purpose, the low pressure valve 20 of Figure 4 is closed, and the high pressure valve 18 is opened, whereby pressure fluid from the high pressure passage 40 of Figure 1 via the pressure chamber 162 and 164 flows into the high-pressure branch passage 74 and from there to the working space 68. During a movement of the piston 16 in the direction of the decreasing working chamber 68 from FIG. 3, the pressure medium is expelled via the low-pressure channels 124 and 126 into the low-pressure region of the radial piston machine 1 when the high-pressure valve 18 and the low-pressure valve 20 are opened.

Through the valve block 24, the high and low pressure valves 18 and 20 of Figure 4 can be pre-assembled and tested independently of the radial piston engine 1 of Figure 2. During maintenance of the radial piston machine 1, the valve block 24 can be easily unscrewed, and the high and low pressure valves 18 and 20 are also checked and maintained independently of the other radial piston engine 1.

For example, if the arrangement or configuration of the high and / or low pressure valve 18 and 20 are changed from Figure 4, it is only necessary in the radial piston engine 1, the valve block 24 to adjust accordingly. An adaptation of the central part 2 is not necessary, as long as the interfaces between the valve block 24 and the central part 2 remain the same.

Disclosed is a hydrostatic displacement machine with cylinder-piston units. These are each associated with a high and a low pressure valve, wherein the high pressure valve is a spool valve having a guided in a slide bore valve slide. The slider is advantageously designed as a hollow slide.

Claims

claims

1 . Hydrostatic displacement machine with cylinder-piston units (14), each associated with a high and a low pressure valve (18, 20), wherein the high pressure valve (18) is a slide valve having a in a slide bore (160) guided valve slide (158 ), characterized in that the valve spool (158) is a hollow slide.

2. Displacement machine according to claim 1, wherein the hollow slide (158) is formed like a bush.

3. A displacement machine according to claim 1 or 2, wherein the hollow slide (158) has a bottom (166) which is arranged towards an actuator (180) of the high-pressure valve (18).

4. Displacement machine according to claim 2 or 3, wherein in the bottom (166) of the hollow slide (158) at least one opening (218) for a volume compensation of the bottom limited valve spaces (21 1, 213) is formed.

5. Displacement machine according to claim 3 or 4, wherein a valve chamber (21 1, 213) on one side of the bottom (166) via a in a valve housing (24) of the high pressure valve (18) introduced channel (212, 214) connected to a tank space is.

6. Displacement machine according to one of claims 3 to 5, wherein valve spaces (21 1, 213) on both sides of the bottom (166) via a respective channel (212, 214) in the valve housing (24) is connected to a tank space.

7. A displacement machine according to claim 5 or 6, wherein the channel (212, 214) in a surface (80, 106) of the valve housing (124) introduced groove (212, 214).

8. Displacement machine according to one of the preceding claims, wherein the hollow slide (158) has an outer circumferential annular groove (168) and in the axial direction outside of the annular groove (168) to its free end (248) out with a larger inner diameter than in the region of the annular groove ( 168) is formed.

9. Displacement machine according to one of the preceding claims, wherein the high-pressure valve (18) has a separate valve housing (24) with a continuous slide bore (160).

10. Displacement machine according to one of the preceding claims, wherein a valve spring (172) of the high-pressure valve (18) for acting on the valve spool (158) is supported and centered with a spring force via a plate (174).

1 1. Displacement machine according to claim 10, wherein the sheet (174) with the valve spring (172) non-positively, material and / or positively connected.

12. displacement machine according to one of claims 4 to 1 1, wherein the at least one opening (218) as a continuous axial bore (218) is formed.

13. Displacement machine according to one of claims 10 to 12, wherein the at least one opening (218) seen in the radial direction of the valve spool (158) is arranged substantially within the helical spring designed as a valve spring (172).

14. A displacement machine according to one of the preceding claims, wherein the valve spool (158) has at least one outer circumferential relief groove (260 to 266).

15. Displacement machine according to one of the preceding claims, wherein a to the slide bore (160) facing outer surface (244) of the valve slide (158) at least partially has a lubricious coating.