Hydraulic valve unit and hydrostatic unit with such a valve unit

Abstract

Hydraulic valve unit (44) with a valve housing (78) extending along an installation axis (84), which is designed for installation and has a first and a second valve bore (60, 61) in each of which a valve body (58, 59) is movably received between two valve seats (62, 64), wherein a first high pressure can be balanced against a first low pressure via a first (58) valve body (58, 59) from first pressures acting on the valve unit (44) and a second high pressure can be balanced against a second low pressure via a second (59) valve body (58, 59) from second pressures acting on the valve unit (44), wherein the two valve bores (60, 61) extend substantially parallel to the installation axis (84), wherein a third valve body (58) extends substantially parallel to the installation axis (84) in a third valve bore (98) which extends substantially parallel to the installation axis (84) between two valve seats (112, 114). The valve body (100) is movably mounted, characterized in that itthat a maximum pressure can be selected from the first and second high pressure via the third valve body (100), wherein the first, second and third valve bores (60, 61, 98) are arranged substantially equally around the installation axis (84).

Description

The invention relates to a hydraulic valve unit according to the preamble of claim 1 and a hydrostatic unit, in particular a pump unit, thereto. A pressure selection or changeover valve is known for selecting a higher pressure from two. It has a valve body movably guided between two valve seats in a valve bore. The pressures to be weighed against each other are present at its two pressure medium inlets, with the higher of the two pressures displacing the valve body accordingly in the valve bore, thus establishing a pressure medium connection between the respective pressure medium inlet and the pressure medium outlet of the changeover valve. To determine the highest pressure from a multitude of pressures, such changeover valves can be connected in a cascade configuration, with two pressure medium outlets of one cascade stage each fluidically connected to a pressure medium inlet of a changeover valve of the next cascade stage, and so on. At the end of the changeover valve cascade, the highest of the pressures is output as the pressure signal. German patent application DE 10 2012 218 450 A1 discloses a two-stage changeover valve cascade with two changeover valves in a first stage and one changeover valve in the second stage, designed as a compact, installable valve cartridge. The changeover valves of the first stage each select the high pressure from a supply and a return line of a hydraulic pump within a pump unit and transfer it to the changeover valve of the second stage. This second stage, in turn, selects the maximum pressure of the two high pressure lines and signals it to a pressure-cutting valve, which allows the control pressure of the pump unit to be reduced. While the cartridge design of the changeover valve cascade offers a reduction in required installation space compared to the modular design of individual changeover valves, the valve cartridge is wide along its mounting axis. Furthermore, the spherical valve bodies, in conjunction with their valve seats, are relatively prone to wear, which can lead to a decrease in the sealing of the valve seats during operation and potentially distort the pressure balance at the respective changeover valve. DE 198 04 398 A1 discloses a valve arrangement for the working hydraulics of a work vehicle. This includes several changeover valves arranged parallel to a common installation axis. DE 43 96 843 T5 discloses an operating valve assembly with a pressure equalization valve. This assembly comprises two changeover valves arranged in alignment along a common installation axis. DE 39 12 390 A1 discloses a control valve. This comprises several changeover valves arranged parallel to a common installation axis. DE 10 2004 061 861 B4 shows a pressure separating valve unit which includes a changeover valve whose valve body is not spherical but elongated. In contrast, the invention is based on the objective of creating a hydraulic valve unit with changeover valves whose installation space is reduced at least transversely to the installation axis of the valve unit. A further objective of the invention is to create a hydrostatic unit with hydraulic machines and such a valve unit whose required installation space is reduced at least in this direction. The first problem is solved by a hydraulic valve unit having the features of claim 1, the second problem is solved by a hydrostatic unit having the features of claim 11. Advantageous further developments of the valve unit are described in claims 2 to 10, and those of the unit in claims 12 to 14. A hydraulic valve unit has a valve housing, which extends, in particular substantially cylindrically or stepped cylindrically, along an installation axis and is designed for installation. The valve housing is designed, in particular, for press-fitting or shrink-fitting. It has at least two valve bores, in each of which a valve body is movably received between two valve seats. A first high pressure can be balanced against a first low pressure via a first valve body based on first pressures acting on the valve unit. A second high pressure can be balanced against a second low pressure via a second valve body based on second pressures acting on the valve unit. According to the invention, the two valve bores extend, in particular with their bore or longitudinal axis, substantially parallel to the installation axis. Compared to the state of the art, where the valve bores extend transversely to the installation axis of the valve unit, a valve unit with a narrower design relative to the installation axis can thus be realized. According to the invention, the valve unit has a third valve bore that extends essentially parallel to the installation axis. A third valve body is movably mounted in this bore between two valve seats, allowing the higher of the two previously measured pressures, i.e., a maximum pressure, to be selected. In addition to the two pressure signals already mentioned – the first high pressure and the second high pressure – the valve unit can thus generate a further pressure signal and make it available for further processing. In a preferred embodiment, the valve unit has two first pressure medium inlets, each carrying one of the aforementioned first pressures. It also has two second pressure medium inlets, each carrying one of the aforementioned second pressures. At least one, and preferably all, of the pressure medium inlets opens transversely to the installation axis, particularly radially, into a surface of the valve housing. This surface is particularly well-suited as a transfer interface for the aforementioned first and second pressures, as it extends around the entire valve unit and offers a multitude of possible flow directions. For a peripheral device, such as a housing into which the valve unit is intended to be installed, the advantage lies in the fact that the pressure medium channels supplying the pressure medium inlets can be flexibly designed. In a preferred embodiment, the pressure medium inlets associated with the respective valve bores – the first pressure medium inlets into the valve bore of the first valve body and the second pressure medium inlets into the valve bore of the second valve body – open into the respective valve bores essentially transversely to the installation axis. The opening can be oriented radially and / or tangentially. In a preferred embodiment, each valve bore has a pressure medium outlet at which the respective measured high pressure or maximum pressure is present. One of the pressure medium outlets, preferably two, and in particular all three, exits its valve bore in essentially the same direction. This allows the valve unit to be narrower relative to its installation axis. In a preferred embodiment, the two pressure medium outlets to which the aforementioned high pressures are reported are each fluidically connected via a connecting channel to one of two pressure medium inlets of the third valve bore. At least one of the connecting channels runs entirely within the valve housing. This connecting channel therefore has no interface to the outside of the valve unit, to the periphery, before reaching the pressure medium inlet of the third valve bore. This reduces the effort required for the design coordination of the periphery with the valve unit, and vice versa, compared to the prior art, where such interfaces are provided. Preferably, the connecting channel(s) are formed via internal connections of the valve housing. According to the invention, the valve bores are arranged essentially equally around the installation axis. The valve unit then has a homogeneous distribution of material, valve bores, and pressure medium channels. In a preferred embodiment, an edge seat is formed over at least one of the valve seats and the valve body that can be brought into sealing contact with it. If the valve bodies are guided longitudinally in the valve bores as elongated parts and can only rotate about a longitudinal axis, they always contact the seat edge at the same point, so that a good sealing effect is achieved through the line contact between a spherical or spherical seat surface and the seat edge. Preferably the valve body(s) and the valve seat(s) are metallic. To enable the installation of a valve body in its valve bore, in a preferred embodiment at least one of the two valve seats, with which the valve body can be brought into sealing contact, is formed on a press-fit or screw-in part arranged in the respective valve bore. The other of the two valve seats is preferably formed on the valve bore, but can alternatively also be designed as a plug-in or screw-in part. In a preferred embodiment, at least one of the valve bodies is designed as a valve piston with a central section that slides within the valve bore and with radially tapered or stepped end sections. The end sections can each be pressurized with pressure medium from one of the pressure medium inlets of the valve bore of this valve body and are fluidically separated from each other via the central section. By using the more massive valve piston compared to the prior art (balls), destructive acceleration forces can be dampened, thereby increasing the service life of the valve unit. A structurally simple solution for fluidically connecting the pressure medium inlet of the valve bore, which is located far from the pressure medium outlet, to its pressure medium outlet is provided if the valve piston is penetrated by a through-hole, in particular a coaxial one. For assembly and / or disassembly purposes, and in particular for providing further interfaces to the periphery, the valve housing in a preferred embodiment has a radially tapered or stepped pin extending in the opposite direction to the installation direction. Preferably, the pressure medium outlet of the third valve bore opens into a cylindrical surface of the pin and / or into a transition surface extending from the pin to the rest of the valve housing, in particular an annular end face. To press out the valve unit that has been pressed into a peripheral component, a preferred embodiment incorporates a blind hole with an internal thread on the end face of the pin. A tool can be attached here during removal. A hydrostatic unit has a housing in which two hydraulic machines, in particular hydraulic pumps, are coupled to each other, especially via their drive shafts. At least one of the hydraulic machines has an adjustable displacement volume. A first hydraulic machine has two pressure chambers, one of which is fluidically connected to an inlet and the other to a return of a hydraulic consumer. A second hydraulic machine has two other pressure chambers, one of which is fluidically connected to the inlet and the other to the return. The hydrostatic unit also has a valve unit, which is designed according to at least one aspect of the preceding description. The valve housing is installed in a valve receptacle in the housing, which is in particular cylindrical or stepped-cylindrical, and is in particular pressed or shrunk in place.Pressing or shrinking is preferably achieved by first immersing the valve unit in a refrigerant, for example, liquid nitrogen. The first and second pressure chambers open into a circumferential surface of the valve housing. The first pressure chambers are each connected to one of the first pressure medium inlets, and the second pressure chambers are each connected to one of the second pressure medium inlets. This offers the advantage for the hydrostatic unit, particularly the pump unit, that the valve unit has a narrow profile relative to its installation axis, thereby reducing the installation space required by the hydrostatic unit, depending on the valve unit's arrangement on the housing. Preferably, the housing has a first pot or pot-shaped section in which the first hydraulic machine is at least partially housed. Correspondingly, the housing preferably has a second pot, in particular arranged approximately diametrically opposite the first pot, in which the second hydraulic machine is at least partially housed. The housing is therefore preferably designed as a double-pot housing, with each pot preferably closed by a housing lid. Preferably, the valve unit is installed in a central section of the housing, for example between the two pots. This central arrangement makes it possible to keep the pressure medium channels provided for transferring the first and second pressures to the valve unit and the pressure medium channels provided for transferring the weighed high pressures or the weighed maximum pressure to the housing short. In a preferred embodiment, the valve unit can output the high pressure of the first hydraulic machine and / or the high pressure of the second hydraulic machine and / or the maximum pressure of the hydraulic machines as a pressure signal. Preferably, a valve device, in particular a pressure regulating or pressure cutting valve, of the unit can be acted upon with the pressure signal(s), wherein a control pressure of the unit provided for adjusting the displacement volume can be changed by the valve device in the direction of a reduction of the displacement volume. In a preferred embodiment, the unit has a sealing screw that closes the valve receptacle in a pressure-tight manner and is seated on the end face of the valve housing's pin. This creates an annular space, fluidically connected to the valve assembly, defined at least by the sealing screw, the pin, and the valve receptacle. The pressure medium outlet of the third valve bore preferably opens into this annular space. The annular space is preferably fluidly connected to, and in particular, directly connected to, the aforementioned valve assembly. Preferably, the unit has an anti-rotation device that secures the valve unit in the housing against rotation about its installation axis. This ensures that the pressure medium inlets of the valve unit are reliably connected to their associated pressure chambers. In particular, the anti-rotation device has a locking projection, for example, a pressed-in or screwed-in pin, which engages with a locking recess, especially a groove, extending in the installation direction. The locking projection can be located on the valve housing and the locking recess on the housing, or vice versa. An embodiment of a hydraulic valve unit and a hydrostatic unit according to the invention are shown in the drawings. The invention will now be explained in more detail with reference to the figures in these drawings. Fig. 1 shows a hydraulic circuit diagram of a hydrostatic unit according to an embodiment of the invention, Fig. 2 shows a longitudinal section of the hydrostatic valve unit according to the invention from Fig. 1, Fig. 3 shows a hydraulic circuit diagram of the valve unit from Fig. 1 and Fig. 2, Fig. 4 shows a longitudinal section of the valve unit from Fig. 1, Fig. 2 to Fig. 3, spaced apart from an installation axis of the valve unit, Fig. 5 shows a further longitudinal section of the valve unit of the preceding figures, Fig. 6 shows a partial section of the hydrostatic unit as it results from the section plane according to Fig. 4, and Fig. 7 shows a partial section of the hydrostatic unit as it results from the section plane according to Fig. 5. As shown in Fig. 1, a hydrostatic unit 1 has a housing 2 in which a first hydraulic machine 4 and a second hydraulic machine 6 are accommodated. Both hydraulic machines 4 and 6 have adjustable displacement volumes and are designed to pivot through zero. They are coupled to each other via a drive shaft 8, which projects from the housing 2 with a stub shaft 10, through which the hydraulic machines 4 and 6 can be driven as pumps. Due to the pivotability of the two hydraulic machines 4 and 6, the direction of the hydraulic medium delivery can be reversed by the hydraulic machines 4 and 6 while maintaining the same direction of rotation of the drive shaft 8. The first hydraulic machine 4 has a first working line 12 and another first working line 14. Accordingly, the second hydraulic machine 6 has a second working line 16 and another second working line 18. A hydraulic consumer (not shown) can be supplied with pressure medium via the working lines 12, 14, 16, 18. Each working line 12, 14, 16, 18 is protected against overpressure by a pressure relief valve 20. A check valve for inlet is integrated into the pressure relief valve 20. While the first hydraulic pump 4 delivers fluid into one first working line 12 or the other first working line 14, which are marked on the housing 2 with connections A1 and B1 respectively, the second hydraulic pump 6 delivers fluid into one second working line 16 or the other second working line 18. The latter are marked on the housing with working connections A2 and B2. The displacement volumes of the hydraulic pumps 4 and 6 are each adjustable via an adjusting device 22 and 24, respectively, which is designed as a double-acting hydraulic cylinder. The opposing piston chambers of the adjusting devices 22 and 24 can be pressurized with control fluid, for example, via an electroproportional 4 / 3-way valve 26 and 28, respectively, as shown.The 4 / 3-way valve 26 is fluidically connected to a control pressure port X of the hydrostatic unit 1 via a first control pressure line 30, and the 4 / 3-way valve 28 is fluidically connected to a control pressure port X of the hydrostatic unit 1 via a second control pressure line 32. A valve assembly 34 is provided in the pressure medium flow path from the control pressure port X to the control pressure lines 30, 32, via which a pressure medium connection of the control pressure lines 30, 32 with the control pressure port X and with a pressure medium sink T, in particular a tank, can be controlled depending on the highest of the pressures present in the working lines 12, 14, 16, 18. The valve assembly 34 is designed as a pressure-cutting valve. Its pressure medium outlet 36 is connected to the control pressure lines 30 and 32, and its pressure medium outlet 38 is connected to the tank T. Furthermore, the valve assembly 34 has a pressure medium inlet 40, which is connected to a pressure medium outlet 42 of a hydraulic valve unit 44 according to the invention. This unit has two first pressure medium inlets 46, 48 and two second pressure medium inlets 50, 52. One first pressure medium inlet 46 is connected to one first working line 12, and the other first pressure medium inlet 48 is connected to the other first working line 14. Correspondingly, one second pressure medium inlet 50 is connected to one second working line 16, and the other second pressure medium inlet 52 is connected to the other second working line 18. The hydraulic valve unit 44 weighs the higher of the two working pressures present in the first working lines 12, 14, as well as the higher of the two working pressures present in the second working lines 16, 18. Both determined high pressures are weighed against each other again via the hydraulic valve unit 44, and the higher of the two, i.e., the maximum pressure of the hydrostatic unit 1, is transferred via the pressure medium outlet 42 of the valve unit 44 to the pressure medium inlet 40 of the pressure-cutting valve 34. There, the determined maximum pressure acts in the closing direction of the pressure medium connection from port X to the control pressure lines 30, 32 and in the opening direction of the pressure medium connection of the control pressure lines 30, 32 with the tank T. The pressure-cutting valve 34 is actuated against a setpoint adjustable by a spring 54.When the pressure-cutting valve 34 is actuated by the maximum pressure, the control pressure effectively supplied to the adjusting devices 22 and 24 decreases. If the force resulting from the control pressure, which acts in the direction of increasing the displacement volume, becomes smaller, a restoring force, for example a respective spring force of the adjusting devices 22, 24, predominates, thereby reducing the respective displacement volume of the hydraulic machines 4, 6 until a force equilibrium is restored. The design of the hydraulic valve unit 44 is explained in more detail below with reference to Figures 2, 3, 4 to 5. According to Figure 3, the valve unit 44 has a first changeover valve 56 with a first valve body 58, which is movably mounted in a first valve bore 60 between two first valve seats 62, 64. The first valve body 58 is subjected to the pressure at one first pressure medium inlet 46 in the direction of the valve seat 64 and to the pressure at the other first pressure medium inlet 48 in the direction of the valve seat 62. Furthermore, the first changeover valve 56 has a pressure medium outlet 66, at which the higher of the pressures at the first pressure medium inlets 46, 48 is indicated.A second changeover valve 68 of the valve unit 44, identical in construction to the first changeover valve 56, processes the pressures present at the second pressure medium inlets 50, 52 in the same manner and signals the higher of the two to a pressure medium outlet 70. The second changeover valve 68 has a valve body 59 which is movably received in a second valve bore 61 between two valve seats. The high pressures present at the pressure medium outlets 66 and 70 are each reported to a third pressure medium inlet 72 or 74 of a third changeover valve 76, which is identical in construction to the first two changeover valves 56 and 68. This third changeover valve determines the higher of the two and thus reports the maximum pressure of the four pressures to the pressure medium outlet 42 of the valve unit 44. From there, it is transferred, as mentioned, to the pressure-cutting valve 34. Fig. 2 shows the valve unit with the three changeover valves 56, 68, 76 in a perspective view. The valve unit 44 has a valve housing 78 with a circular cylindrical base body 80 in the illustrated embodiment and a circular cylindrical pin 82 radially stepped back at one end section of the base body 80. An annular end face 86 remains between the base body 80 and the pin 82. The base body 80 and the pin 82 extend rotationally symmetrically along an installation axis 84, which corresponds to an installation direction of the valve unit 44 into a periphery, for example into the housing 2 of the hydrostatic unit 1. The changeover valves 56, 68, and 76 are arranged approximately equally around the installation axis 84 in the circumferential direction. The two changeover valves 56 and 68 are positioned at approximately the same height within the base body 80, relative to the installation axis 84. The third changeover valve 76, however, has an offset in the direction of the pin 82 of approximately half a valve length. As shown in Fig. 2, the first pressure medium inlets 46, 48 of the first changeover valve 56 open transversely to the installation axis 84 into a cylindrical surface 88 of the base body 80. They do not open strictly radially into the cylindrical surface 88, but approximately parallel to a plane defined by the central axes of the changeover valves 56 and 68. As shown in Fig. 2, the third pressure medium inlets 72, 74 of the third changeover valve 76 open radially into its valve bore. Both third pressure medium inlets 72, 74 are formed by a transverse bore extending from the cylindrical surface 88 towards the valve bore of the third changeover valve 76. The bore of the other third pressure medium inlet 74 is formed by a radial bore. Both bores are closed by a sealing plug in the region of the cylindrical surface 88. According to Fig. 4, the first valve body 58 of the first changeover valve 56 is slidably mounted in the first valve bore 60, and the second valve body 59 of the second changeover valve 68 is slidably mounted in the second valve bore 61. Fig. 4 shows the longitudinal section AA as defined in Fig. 2. It is clearly visible that the pressure medium outlets 66, 70 of the changeover valves 56, 68 initially exit in the same direction as the respective valve bores 60, 61, in the illustrated embodiment essentially parallel to the installation axis 84. According to Fig. 4, the bore of one of the third pressure medium inlets 72 (compare Fig. 2) intersects the pressure medium outlet 66, thus fluidically connecting it to the third pressure medium inlet 72. The pressure medium outlet 70 of the second changeover valve 68 is first crossed by a transverse bore 94, which is also closed on the outer surface 88 by a sealing plug, as shown in Fig. 2, and which in turn is crossed by aThe longitudinal bore 96, which runs parallel to the installation axis 84, is crossed by the transverse bore of the other third pressure medium inlet 74 of a third valve bore 98 of the third changeover valve 76, so that, according to Fig. 5, the pressure medium outlet 70 is ultimately fluidically connected to the other third pressure medium inlet 74 of the third valve bore 98. A third valve body 100, identical in construction to the aforementioned valve bodies 58, 59, is slidably guided in the third valve bore 98. Due to their identical construction, the description of valve bodies 58, 59, and 100 is given by way of example using the third valve body 100 as shown in Fig. 5. The valve body 100 is designed as a valve piston with a cylindrical central section 102 and radially stepped end sections 104 and 106. The end sections 104 and 106 are provided with a spherical seat surface 108 and 110, respectively, on their end faces. The seat surface 108 interacts with a circular seat edge 112 on the housing side, and the seat surface 110 interacts with a circular seat surface 114 on the housing side. The latter, however, is not formed directly on the base body 80 of the housing 78, but rather on a press-fit part 116, which is pressed into a radially enlarged section of the third valve bore 98. When a conical seat surface 108 or 110 rests on the corresponding seat edge 112 and 144, the corresponding fluidic connection is largely sealed without leakage. The valve piston 100 is penetrated in its longitudinal direction, parallel to the installation axis 84 in the illustrated embodiment, by a through-hole 118. This through-hole connects the other third pressure medium inlet 74 to the pressure medium outlet 42 of the third changeover valve 76 when the valve piston 100 is lifted from the seat surface 114. To enable the conical seat surface 110 of the end section 106 to come into contact with the conical seat surface 114 of the screw-in part 116, the screw-in part 116 has a blind hole 120 facing the end section 106, at the end edge of which the conical seat surface 114 is formed. The pressure medium outlet 42 of the third changeover valve 76 extends in the same direction as the third valve bore 98 towards the pin 82 and opens section by section into the annular end face 86 of the base body 80 and section by section into a lateral surface 122 of the pin 82. The pin 82 has a blind bore 124 with internal thread, designed coaxially to the installation axis 84, into which a threaded section of a tool can be screwed for the purpose of dismantling the valve unit 44 from the hydrostatic unit 1. A hollow pin 126 is inserted radially into the base body 80 of the valve housing 78, via which, in conjunction with a groove or recess of the hydrostatic unit 1 extending parallel to the installation axis 84, an anti-rotation device is formed. Fig. 6 shows a partial section of the hydrostatic unit 1 in a section plane as already defined according to Figs. 2 and 4. The housing 2 is designed as a double-pot housing, with the first hydraulic machine housed in a first pot 128 and the second hydraulic machine housed in a second pot 130. Both hydraulic machines are not shown for clarity. The adjusting devices 22, 24 of the hydraulic machines 4, 6 are arranged on the upper side of the housing 2. In a central section 132 of the housing 2, located between the two pots 128, 130, the valve unit 44 is pressed into a valve receptacle 134. As shown in Fig. 7, a retaining recess 136 in the form of a groove is formed in the valve receptacle 134 parallel to the installation axis 84, into which the hollow pin 126 engages. This ensures that, when the valve unit 44 is mounted in the valve receptacle 134, the hydraulic inlets 46, 48, 50, 52 of the valve unit 44 come into hydraulic contact with the working lines 12, 14, 16 and 18 (see Fig. 1). As already mentioned, the pressure medium inlets 46, 48, 50 and 52 open transversely to the installation axis 84 into the lateral surface 88 of the base body 80.The working lines 12, 14, 16 and 18 are aligned approximately tangentially with respect to the shell surface 88, with the pressure medium inlets 48, 52 each opening directly into the working line 14 and 18 respectively, and the pressure medium inlets 46, 50 each opening into the working bore 12 and 16 respectively via a short transverse and a longer longitudinal bore. The valve receptacle 134 has a base 138 with which a terminal face of the base body 80 furthest from the pin is in contact. One opening of the valve receptacle 134 is closed by a sealing screw 140, which is screwed in to such an extent that its end face is in contact with the pin 82. Thus, an annular space 142 is defined by the outer surface of the pin 82, a base surface of the sealing screw 140, an inner outer surface of the valve receptacle 134, and the annular end face 86. The previously mentioned pressure medium outlet 42 of the third changeover valve 76 opens into this space, as does a pressure medium channel 144, through which, as shown in Figures 1 and 7, the pressure medium outlet 42 is connected to the pressure medium inlet 40 of the pressure-cutting valve 34. Here, the maximum pressure is transferred to the pressure-cutting valve 34. A hydraulic valve unit with a valve housing designed for installation is disclosed, in which at least two changeover valves are provided for selecting two high pressures from two available pressure pairs. According to the invention, valve bores in which the valve bodies of the changeover valves are received extend essentially parallel to an installation axis of the valve unit. A hydrostatic unit with two coupled hydraulic machines, in particular hydraulic pumps, and a housing with a valve receptacle into which the valve unit is installed is also disclosed. Each of the two valve bodies of the valve unit has working lines assigned to one of the hydraulic machines for selecting their respective high pressure. Reference symbol list 1 hydrostatic unit 2 housing 4 first hydraulic machine 6 second hydraulic machine 8 drive shaft 10 shaft stub 12, 14, 16, 18 working line 20 pressure relief valve 22, 24 adjusting device 26, 28 4 / 3-way valve 30, 32 control pressure line 34 valve assembly 36, 38 hydraulic outlet 40 hydraulic inlet 42 third hydraulic outlet 46, 48 first hydraulic inlet 50, 52 second hydraulic inlet 54 spring 56 first changeover valve 58 first valve body 59 second valve body 60 first valve bore 61 second valve bore 62, 64 valve seat 66 first hydraulic outlet 68 second changeover valve 70 second hydraulic outlet 72 hydraulic inlet 74 hydraulic inlet 76 third changeover valve 78 valve housing 80 base body 82 pin 84 mounting shaft 86 Ring face 88 Circular surface 94 Transverse bore 96 Longitudinal bore 98 Third valve bore 100 Third valve body 102 Middle section 104, 106 End section 108, 110, 112,114 Seat surface 116 Press-in part 118 Through-hole recess 120 Blind hole recess 122 Circumferential surface 124 Blind hole bore 126 Hollow pin 128 First cup 130 Second cup 132 Center section 134 Valve receptacle 136 Groove 138 Base 140 Sealing screw 142 Annular space 144 Pressure medium channel A1, A2, B1, B2 Working port X Control pressure port

Claims

Hydraulic valve unit (44) with a valve housing (78) extending along an installation axis (84), which is designed for installation and has a first and a second valve bore (60, 61) in each of which a valve body (58, 59) is movably received between two valve seats (62, 64), wherein a first high pressure can be balanced against a first low pressure via a first (58) valve body (58, 59) from first pressures acting on the valve unit (44) and a second high pressure can be balanced against a second low pressure via a second (59) valve body (58, 59) from second pressures acting on the valve unit (44), wherein the two valve bores (60, 61) extend substantially parallel to the installation axis (84), wherein a third valve body (58) extends substantially parallel to the installation axis (84) in a third valve bore (98) which extends substantially parallel to the installation axis (84) between two valve seats (112, 114). The valve body (100) is movably mounted, characterized in that itthat a maximum pressure can be selected from the first and second high pressure via the third valve body (100), wherein the first, second and third valve bores (60, 61, 98) are arranged substantially equally around the installation axis (84). Valve unit according to claim 1 with first pressure medium inlets (46, 48) at which the first pressures are present, and with second pressure medium inlets (50, 52) at which the second pressures are present, wherein the pressure medium inlets (46, 48, 50, 52) open transversely to the installation axis (84) into a cylindrical surface (88) of the valve housing (78). Valve unit according to claim 2, wherein the pressure medium inlets (46, 48, 50, 52, 72, 74) associated with the respective valve bore (60, 61, 98) open into the valve bore (60, 61, 98) substantially transversely to the installation axis (84). Valve unit according to one of the preceding claims, wherein a pressure medium outlet (66, 70, 42) opens out of each of the valve bores (60, 61, 98), and wherein at least one of the pressure medium outlets (66, 70, 42) is substantially in the same direction as the valve bore (60, 61, 98) from which it opens. Valve unit according to claim 4, wherein the two pressure medium outlets (66, 70), to which the high pressures are reported, are each fluidically connected via a connecting channel (94, 96) to a pressure medium inlet (72, 74) of the third valve bore (98), wherein at least one of the connecting channels (94, 96) is formed completely within the valve housing (78). Valve unit according to one of the preceding claims, wherein an edge seat is formed over at least one of the valve seats (62, 64, 112, 114) and the valve body (58, 59, 100) that can be brought into sealing contact with it. Valve unit according to claim 2 or according to claims 2 and 5, wherein at least one of the valve bodies is designed as a valve piston (58, 59, 100) with a central section (102) guided slidably in the valve bore (60, 61, 98) and radially tapered or stepped end sections (104, 106), and wherein the end sections (104, 106) are each supplied with pressure medium from one of the pressure medium inlets (46, 48, 50, 52, 72, 74) of the valve bore (60, 61, 98) of this valve piston (58, 59, 100) and are fluidically separated from each other via the central section (102). Valve unit according to claims 4 and 7, wherein the valve piston (58, 59, 100) is penetrated by a through-hole (118) through which the pressure medium inlet (46, 50, 74) of the valve bore (60, 61, 98) arranged remotely from the pressure medium outlet (66, 70, 42) can be fluidically connected to the pressure medium inlet (46, 50, 74). Valve unit according to one of the preceding claims, wherein the valve housing (78) has a radially tapered or stepped pin (82) extending in the opposite direction of installation. Valve unit according to claims 4 and 9, wherein the pressure medium outlet (42) of the third valve bore (98) opens into a shell surface (122) of the pin (82) and / or into a transition surface (86) extending from the pin (82) to the rest of the valve housing (80). Hydrostatic unit (1) with a housing (2) in which two coupled hydraulic machines (4, 6) are accommodated, at least one of which (4, 6) has an adjustable displacement volume, wherein a first (4) of the hydraulic machines (4, 6) has two first pressure chambers (12, 14), one of which is fluidically connectable to an inlet and the other to a return of a hydraulic consumer, and wherein a second (6) of the hydraulic machines (4, 6) has two second pressure chambers (16, 18), one of which is fluidically connectable to the inlet and the other to the return of a hydraulic consumer, and with a valve unit (44) configured according to one of the preceding claims, wherein the valve housing (78) is installed in a valve receptacle (134) of the housing (2) into which the first and second pressure chambers (12, 14, 16, 18) open, so that the first pressure chambers (12, 14) each with one of the first pressure medium inlets (46,48) and the second pressure chambers (16, 18) are each connected to one of the second pressure medium inlets (50, 52) in pressure medium connection. Unit according to claim 11, wherein the high pressure of the first hydraulic machine (4) and / or the high pressure of the second hydraulic machine (6) and / or the maximum pressure of the hydraulic machines (4, 6) can be output as a pressure signal from the valve unit (44). Unit according to claim 12, wherein a valve device (34) of the unit (1) can be acted upon by the pressure signal(s), from which a control pressure provided for adjusting the displacement volume can be changed in the direction of a reduction of the displacement volume. Unit according to one of claims 11 to 13, wherein the valve unit (44) is configured according to claim 10, with a sealing screw (140) which closes the valve receptacle (134) in a pressure-medium-tight manner and which sits on the end face of the pin (82) of the valve housing (78), whereby an annular space (142) which can be fluidically connected to the valve assembly (34) is defined at least by the sealing screw (140), the pin (82) and the valve receptacle (134).

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