HYDRAULIC UNIT

A hydraulic unit (10) for providing a pressurized hydraulic fluid for driving a coupled hydraulic actuator (12), comprising a motor (30) arranged in a motor housing (28), a hydraulic accumulator (40) arranged in an accumulator housing, a hydraulic pump (36) arranged in a hydraulic housing and a hydraulic block (38), wherein the motor housing (28), the accumulator housing and the hydraulic housing are fluidically connected to one another. It is provided that at least one main flow connection between the hydraulic pump (36) and the actuator (12) is guided through at least one channel (44) of the motor housing (28).

The invention relates to a hydraulic unit for providing a pressurized hydraulic fluid for driving a coupled hydraulic actuator.

A generic type of hydraulic unit is known.

For instance, EP 2 128 446 B1 discloses a hydraulic unit with a motor arranged in a motor housing, a hydraulic accumulator arranged in an accumulator housing, a hydraulic pump arranged in a pump housing and a hydraulic block. These form a rigid module which is able to be handled uniformly, wherein hydraulic fluid circulating in the module passes through all elements of the module in longitudinal direction in certain sections. The hydraulic fluid circulating in the module is an accumulator volume flow which can circulate between the hydraulic accumulator and the hydraulic pump. A main flow connection is guided past the hydraulic unit between the hydraulic block and the hydraulic actuator.

The invention is based on the problem of creating a generic type of hydraulic unit, which has a compact structure and allows improved cooling of the motor.

According to the invention, this problem is solved by a hydraulic unit having the features given in Claim1. The fact that at least one main flow connection between the hydraulic pump and the actuator, which is able to be subjected to high pressure, is guided through at least one channel of the motor, makes it possible advantageously to achieve a very effective cooling of the motor by the flow of the pump main volume flow through the channel of the main flow connection in the motor. In this way there is maximum heat transfer between the motor components of the motor and the housing. The heat can then be dissipated effectively to the external environment via the housing. Within the scope of the invention, high pressure is defined as load pressure or working pressure of the hydraulic pump for pressurizing the actuator.

In a preferred embodiment of the invention it is provided that the main flow connection through the motor is a forward flow or a return flow. In this way it is advantageously achieved that, depending on the control of the hydraulic actuator coupled to the hydraulic unit, the greatest possible volume flow is guided through the motor. This also enables the greatest possible dissipation of heat from the motor and thus the cooling of the motor components.

In a further preferred embodiment of the invention it is provided that the main flow connection is the forward flow or return flow depending on the direction of rotation of the hydraulic pump. Advantageously, this makes it possible for one and the same channel of the main flow connection, which is able to be subjected to high pressure, to be switched by the motor to forward flow or return flow depending on the direction of rotation of the hydraulic pump. In this way it is ensured in any case that the greatest possible volume flows through the motor and is available for cooling the motor components.

In a further preferred embodiment of the invention it is provided that the hydraulic pump is a pump that is able to be operated in a four-quadrant mode which allows delivery and recovery in two directions. This makes it advantageous to combine the hydraulic unit with a four-quadrant hydraulic pump, which is known per se, by which the flow direction of the main volume flow can then be changed in a simple manner according to the direction of rotation. This results in a very advantageous combination of the channel of the main flow connection in the motor, which can be used for forward flow or return flow.

According to the invention, it is preferably provided that the at least one channel is directed through a motor housing of the motor. This makes it easy to integrate the at least one channel and achieve particularly effective heat dissipation.

In a further preferred embodiment of the invention it is provided that the at least one channel of the motor housing for the main power connection comprises a wall that comes into direct contact with the outside of the motor housing. This makes it possible, in a particularly advantageous manner, for the heat of the motor components to dissipate via the medium of the hydraulic fluid to the outside of the motor housing and thus into the environment.

Furthermore, in a preferred embodiment of the invention, it is provided that the at least one channel is guided through the motor housing in a meandering and/or spiral manner. In this way, very advantageously, the greatest possible contact area is obtained between the medium of the hydraulic fluid and the motor housing. The heat dissipation is thereby particularly effective. The heat flow is evenly distributed over the entire surface of the motor housing in order to avoid hot spots on the motor and thermal stresses as a result of uneven temperature distribution.

In a preferred embodiment of the invention it is further provided that power electronics for controlling the motor can also be cooled by the main volume flow. For this purpose, the power electronics can be directly coupled to the motor housing cooled by the main volume flow in a thermally conductive manner. It is also conceivable to direct the main volume flow directly through corresponding channels provided in a housing of the power electronics. This is particularly advantageous if the power electronics cannot be arranged directly on the motor housing for structural reasons.

In addition, in a further preferred embodiment of the invention, it is provided that an accumulator volume flow between an accumulator housing and the hydraulic pump is guided through a channel of the motor which is separate from the main volume flow. This allows the accumulator volume flow to be used for additional cooling of the motor components.

It is provided preferably that the channel for the accumulator volume flow is directed through a rotor shaft of the motor, which is preferably in the form of a hollow shaft. This enables a fluid connection to be created directly for an accumulator volume flow.

Furthermore, in a preferred embodiment of the invention it is provided that the hydraulic accumulator comprises an intermediate chamber which is flange-mounted onto the motor housing or is formed with the latter, which has a large surface area to the environment. In this way, further improved heat dissipation into the environment can be achieved via the intermediate chamber by forced convection on the surface.

Furthermore, according to the invention it is provided that the accumulator volume flow flows through the intermediate chamber between the motor and accumulator in only one direction, depending on the accumulator volume direction, via a non-return valve. This advantageously makes optimum use of the intermediate chamber for heat dissipation to the environment.

Further preferred configurations of the invention are given in the remaining features set out in the dependent claims.

The invention is explained in more detail in the following by way of an exemplary embodiment with reference to the associated drawings,

in which:

FIG.1shows a schematic cross-sectional view of a hydraulic unit denoted as a whole by the number10. This is used to supply a hydraulic actuator12with a pressurized hydraulic fluid. The actuator12has a housing14inside which a piston16is able to be linearly displaced. The piston16is guided in a sealing manner in the housing14via a seal18. A sealing element20connected to the piston16divides the housing14into two separate chambers22and24. Depending on the pressure difference between the chambers22and24the piston16is moved out of or into the housing14. In this way it is possible to perform a travel motion with the piston16. The actual position of the piston16is able to be determined by a position sensor.

The structure and mode of operation of such an actuator12are known in principle.

The structure and function of the hydraulic unit10according to the invention for controlling the actuator12are described in more detail below.

The hydraulic unit10comprises a motor30arranged in a motor housing28which has a stator32and a rotor34.

The motor30is operatively connected to a hydraulic pump36. The hydraulic pump36is formed as a pump that is able to be operated in four-quadrant mode. A hydraulic block38is connected to the side of the hydraulic pump36facing away from the motor30, inside which hydraulic block, valves, not shown in detail here, are used to control a volume flow of hydraulic fluid generated by the hydraulic pump36.

The structure and function of the motor30with an operatively connected hydraulic pump36and coupled hydraulic block38are also known in principle to the person skilled in the art, so that this is not discussed in detail in the description of the present invention.

The hydraulic unit10is also associated with a hydraulic accumulator40, which comprises an intermediate chamber42, which is flange-mounted on the motor housing28or is formed with the latter.

The actuator12, motor housing28, hydraulic pump36, hydraulic block38and accumulator40are connected to one another fluidically in the manner described in the following.

At least one channel44, which forms a main flow connection for the main volume flow of the hydraulic pump36to the actuator12, is guided through the motor housing28.

The channel44is formed inside the motor housing28so that it is arranged close to an outer casing46of the motor housing28. An inner wall of the channel44is thus directly adjacent to the outer wall46of the motor housing28.

The channel44can be formed to be branched inside the motor housing28. The latter can extend along the motor housing28in a meandering and/or spiral manner in its longitudinal direction. It can also be formed to be branched so that a plurality of subchannels of the channel44extend in parallel around the circumference of the motor housing28. In each case the channel44has an inlet side48facing the hydraulic pump36and an outlet side50at its opposite end.

A connecting piece52extends from the outlet50to an inlet54into the chamber24of the actuator12.

The chamber22of the actuator12is connected to the hydraulic pump36via a connection56. The connection56is guided through the hydraulic block38and a fastening portion58. The fastening portion58is used for mechanically fastening the entire device consisting of hydraulic unit10and actuator12.

Both the channel44with connecting piece52and the connection56form main flow connections for a main volume flow of the hydraulic pump36.

Depending on the operating mode of the hydraulic pump36, i.e. depending on the direction of rotation, the channel44is a forward flow and the connection56is a return flow of the hydraulic unit10. When the direction of rotation of the hydraulic pump36is reversed, the channel44is the return flow and the connection56is the forward flow.

FIG.1shows a switching state of the hydraulic unit10, in which the piston16is retracted into the housing14of the actuator12. This means that there is higher pressure in the chamber24of the housing14than in the chamber22. The channel44with its connecting piece52is the forward flow for the hydraulic unit10in this switching state. The hydraulic fluid present in the chamber22is displaced and transferred via the connection56into the hydraulic unit10. The connection56is thus the return flow of the hydraulic unit10in this switching state.

This is indicated by the arrow directions of the main volume flow of the hydraulic fluid.

The main volume flow of the hydraulic pump36which is guided through the channel44(or the system of channels44) in the motor housing28, contributes to an effective and maximum cooling of the motor30by absorbing the heat emitted by the motor30and releasing it to the environment via the external circumference of the motor housing28. This is indicated by a heat arrow60in the region of the motor housing28.

The hydraulic unit10is also associated with the hydraulic accumulator40, into which the hydraulic fluid is returned. As the hydraulic fluid is displaced into the housing14of the actuator12(according to the retraction position inFIG.1from the chamber22), it has to be returned back to the hydraulic accumulator40, from which the hydraulic pump36then builds up the pressure for the forward flow of the main volume flow.

The intermediate chamber42is associated with the hydraulic accumulator40. This is formed by a cavity64formed inside a housing62.

Inside the motor30this storage volume flow (return of hydraulic fluid) is guided through a rotor shaft65of the rotor34. For this purpose, this rotor shaft is formed as a hollow shaft. An intermediate channel66between the rotor shaft (hollow shaft)65opens into the intermediate chamber42. The intermediate chamber42has a lance-like guide68, which results in the storage volume flow inside the cavity64of the intermediate chamber42receiving a predetermined forced guidance. The storage volume flow is thus swirled inside the intermediate chamber42and guided along the housing of the intermediate chamber42. This results in an improved heat dissipation through forced convection on the relatively large available surface of the inner wall of the intermediate chamber42via the housing62to the environment. This is indicated by a heat dissipation arrow70.

The connecting piece52between the channel44and the housing14is guided on the outer casing of the intermediate chamber42.

A control device, not shown in more detail, which can be used to control the motor30and thus the delivery rate of the hydraulic pump36, is associated with the hydraulic unit10. The position sensor is connected to the control device via signal lines. Furthermore, the hydraulic block38can comprise electrically controllable valves, which are also connected to the control device by regulation and/or control technology.

All in all, the configuration of the hydraulic unit10according to the invention enables effective and maximum heat dissipation so that the engine30can be cooled to an optimal degree.

According to a further exemplary embodiment, not shown, the main volume flow can also be guided directly through the interior of the motor30, for example, axially through a motor air gap and/or through bores, recesses or grooves in the rotor and/or stator laminated core.

FIG.2shows a switching state of the hydraulic unit10, in which the piston16of the actuator12is extended out of the housing14.

The same parts as inFIG.1are denoted by the same reference signs and not explained again.

In contrast toFIG.1,FIG.2clearly shows the reverse flow direction of the main volume flow and the accumulator volume flow through the hydraulic unit10. In this switching state, the main flow connection (here a return flow) is guided between the actuator12and hydraulic pump36through the motor housing28.

It is not shown that the accumulator volume flow only flows in one direction via a non-return valve through the intermediate chamber between the motor and accumulator, depending on the direction of the accumulator flow, as shown inFIG.1for example.

According to an exemplary embodiment not shown, it can also be provided that the motor is formed with the motor housing as a separate component, which means that the motor is not connected directly to the hydraulic pump and/or the intermediate accumulator and/or the hydraulic block and/or the power electronics. The channel of the main flow connection for cooling the motor is also guided through the motor housing in these embodiment variants.

REFERENCE SIGNS