DE102007053263A1 - Electrohydraulic vehicle steering system for use in heavy vehicle e.g. heavy passenger car, has housing attached to hydraulic circuit and filled with hydraulic fluid that passes through housing during operation of pump - Google Patents

Abstract

The system (6) has a hydraulic circuit (8) with a pump (24) and a cylinder/piston unit (26). An electric motor (22) is accommodated in motor housing (34), where the motor drives the pump. The pump is reversibly formed, and a working chamber (28) or another working chamber (30) of the cylinder/piston unit acts upon with hydraulic pressure depending on drive direction of the motor. The housing is attached to the hydraulic circuit and is filled with hydraulic fluid used as cooling agent. The fluid passes through the housing during operation of the pump.

Description

The The invention relates to an electro-hydraulic vehicle steering system with a hydraulic circuit comprising a pump and a cylinder / piston unit includes, as well as an electric motor, in a motor housing is housed and drives the pump, the pump being reversible is formed and dependent on a drive direction the electric motor optionally a first working chamber or a second Working chamber of the cylinder / piston unit with a hydraulic pressure applied.

Such a vehicle steering system according to the preamble of claim 1 is generally known from the prior art. For example, shows the DE 40 40 003 A1 a power steering, in which an electric motor is controlled by an electronic control unit and drives a reversible hydraulic pump. As a reversible pump, a pump is referred to in this context, which can be operated bidirectionally, that has two different flow directions for hydraulic fluid. Depending on the drive direction of the electric motor or conveying direction of the pump, a hydraulic actuator of the power steering is subjected to a pressure medium, so that he selectively applies a left-handed or right-handed torque on a steering column and thus supports a steering movement of the driver.

There the electro-hydraulic vehicle steering system during of the plant is usually a cooling, usually provided an air cooling. It can in one Housing of the electric motor, for example, cooling fins be formed to a housing surface enlarge and thus the air cooling to improve. Nevertheless, the electric motor heats up especially and the electronic control unit so strong that the life of this Components can be affected. Thus, the use this electro-hydraulic vehicle steering systems in particular at powerful power steering for trucks or heavy passenger cars due to the undesirable high heat development problematic.

task The invention is the cooling of an electro-hydraulic To improve the vehicle steering system so that an insert of the Vehicle steering system even in large, heavy vehicles easily possible.

According to the invention the task by an electro-hydraulic vehicle steering system of the beginning solved type mentioned, in which the motor housing connected to the hydraulic circuit and filled with hydraulic fluid is. The hydraulic fluid is thus in the motor housing and thus in the area of the main heat source of the vehicle steering system used as a coolant, resulting in a very effective cooling of the electro-hydraulic vehicle steering system results.

Especially is the motor housing during operation of the pump of a hydraulic fluid flows through. By this flow of hydraulic fluid can the heat energy generated by the electric motor is particularly good be removed, which continues the cooling effect improved.

Preferably is an electronic housing adjacent to the motor housing Control unit provided by the electric motor through wall elements is separated, which has a good thermal conductivity exhibit. As a result of this measure are also heat-generating Electronic components of the electronic control unit by the hydraulic fluid cooled. As with the electric motor and the electronic Control unit the main heat sources well cooled The electro-hydraulic vehicle steering system can be more efficient trained and larger or heavier vehicles be used without causing overheating comes.

In In one embodiment, a hydraulic fluid reservoir is provided, the over the motor housing, particularly preferred exclusively via the motor housing, communicates with the hydraulic circuit. By the delivery of Hydraulic fluid through the motor housing in the hydraulic fluid reservoir (eg as a result of volume changes, pump leakage, or similar) as well as corresponding suction from the hydraulic fluid reservoir, is a "basic flow" during operation of the power steering system in the motor housing and thus an advantageous cooling ensured.

Preferably the hydraulic fluid reservoir is designed as a low-pressure accumulator and pressurizes the hydraulic circuit with a desired hydraulic pressure. As a result, in particular, the motor housing and a The suction side of the pump is preloaded with this hydraulic pressure. This bias is particularly advantageous in electro-hydraulic vehicle steering systems, because they largely cavitation phenomena in the area of the pump prevented.

In Another embodiment includes the hydraulic circuit a valve unit with at least one hydraulic valve, wherein the Valve unit is part of a motor-pump unit. In a special embodiment is the valve unit it is housed directly in the motor housing. This carries to a particularly compact design of the electro-hydraulic vehicle steering system at.

The hydraulic circuit preferably has two non-return valves, which releases a hydraulic connection to the motor housing on the pump suction side ben and pump pressure side lock a hydraulic connection to the motor housing. These valves allow the suction of hydraulic fluid through the motor housing, whereby a corresponding cooling takes place, while preventing a backflow from the pump pressure side into the motor housing. With respect to a necessary tightness of the engine and the motor housing must therefore be designed only to the existing under certain circumstances biasing pressure, which is less bar in the range.

Further the hydraulic circuit can have two non-return valves, the pump suction on a hydraulic direct connection to the cylinder / piston unit lock and release a hydraulic connection to the cylinder / piston unit on the pump pressure side. Depending on the direction of the pump, such a check valve provides So either for a sufficient hydraulic fluid flow in the motor housing, as it pumpenaugseitig a parallel Direct connection with lower flow resistance blocks, or it allows pump pressure side a simple, direct and rapid pressurization of the cylinder / piston unit.

In Another embodiment, the hydraulic circuit two check valves biased in their blocking position on, each starting from a predeterminable pressure difference between a suction side of the pump and the respective associated working chamber release a hydraulic direct connection. Open these check valves If necessary, a bypass to a suction-side load of the pump to limit and possible cavitation phenomena in the area to prevent the pump.

Further can the hydraulic circuit alternatively or additionally also have two throttles that both pump suction side and pump pressure side Ensure a restricted direct connection to the cylinder / piston unit. Pump suction side, the respective throttle sets, in which ratio the Total delivery volume of the pump through the throttle or through the pump housing is sucked. Pump pressure side has the throttle hardly a function, since usually a parallel hydraulic line provided with significantly lower flow resistance is.

The Motor housing can via a directional control valve with the Cylinder / piston unit are in hydraulic communication with, the directional valve preferably a hydraulically controlled 3/3-way valve is. With this way valve is ensured in a simple manner, that the motor housing always with that working chamber the cylinder / piston unit communicates with the lower one Hydraulic pressure has.

Especially Preferably, the directional control valve is a shuttle valve with throttled open center. Through this open center takes place in an advantageous manner Way, a pressure balance between the working chambers instead when the vehicle steering system is in a neutral position, So no power assistance is desired (for Example when driving straight ahead). Furthermore, through the open Center a continuous response of the shuttle valve reached.

In In a preferred embodiment, the pump is over a leakage oil connection with the motor housing in conjunction so that the motor housing during operation the pump flows through a leakage fluid of the hydraulic pump is. As a result of this flow through the motor housing with hydraulic fluid is in system operation, a cooling of the Motors guaranteed.

Preferably is in the motor housing coupled to the electric motor and provided by the hydraulic fluid flowing around the rotating element. The rotation element is particularly preferably in a rotor of Electric motor integrated and ensures a circulation of the hydraulic fluid within the motor housing, thereby the cooling effect improves.

The Rotation element can be z. B. a grooved rotor of the electric motor or be an impeller.

Around the cooling of the engine and possibly the electronic Further improve control unit, in housing walls be integrated into the motor housing hydraulic channels, these hydraulic channels being part of a connecting line between the pump and the working chambers of the cylinder / piston unit are. Thus, on the one hand, the motor housing with hydraulic fluid filled, on the other hand are hydraulic channels in the Housing walls of the motor housing of hydraulic fluid flows through. Consequently, with a suitable choice of the Housing material excellent heat conduction, wherein the hydraulic lines of the hydraulic circuit as a cooling loop be used.

Further Features and advantages of the invention will become apparent from the following Description of preferred embodiments with reference to the painting. In these show:

1 a schematic view of a first embodiment of the vehicle steering system according to the invention;

2 a schematic view of a second embodiment of the vehicle steering system according to the invention;

3 a schematic view of a third embodiment of the vehicle steering system according to the invention;

4 a schematic view of a fourth embodiment of the vehicle steering system according to the invention; and

5 a schematic view of a fifth embodiment of the vehicle steering system according to the invention.

In the 1 to 5 are hydraulic circuit diagrams for a vehicle steering system 6 shown schematically. Specifically, the circuit diagrams each show a closed hydraulic circuit 8th for an electro-hydraulic vehicle steering system 6 ,

The electrohydraulic steering system 6 has a steering wheel 10 on, which in a known manner via a steering gear 12 with a rack 14 coupled, which in turn interacts with steerable wheels of a motor vehicle (not shown). At the steering gear 12 is a steering torque and / or steering angle sensor 16 provided its sensor data to an electronic control unit 18 a motor-pump unit 20 passes. The engine-pump unit 20 is the interface between the electrical and the hydraulic part of the electrohydraulic steering system 6 and points next to the electronic control unit 18 another engine 22 and a reversible pump 24 on. As a reversible pump 24 is referred to in this context, a bidirectional pump having two different directions of delivery of hydraulic fluid. The steering system 6 further comprises a cylinder / piston unit 26 with two working chambers 28 . 30 , which depends on the conveying direction of the pump 24 be pressurized and correspondingly an axial movement of the rack 14 effect or assist in a first or an opposite second direction.

The 1 also shows a fail-safe valve 32 which the working chambers 28 . 30 the cylinder / piston unit 26 shorts in the event of a system failure, so that no hydraulic blockage occurs. The motor vehicle steering then works purely mechanically in this case.

Of the basic structure of an electro-hydraulic vehicle steering system as well as its operation are already generally out of the state known in the art, which is why in the following only fiction relevant Details will be received.

A special feature of the vehicle steering system 6 according to 1 is the design of the motor-pump unit 20 , in particular of the electric motor 22 as a motor housing 34 of the electric motor 22 to the hydraulic circuit 8th connected and filled with hydraulic fluid. The electric motor 22 is thus a so-called wet-rotor engine. During operation of the hydraulic pump 24 is the motor housing 34 even flows through hydraulic fluid, so that sets a particularly good engine cooling.

In addition, the to the motor housing 34 adjacent electronic control unit 18 from the electric motor 22 through wall elements 36 separated, which have a good Wärmeleiffähigkeit. These wall elements 36 are, for example, sections of a housing 38 the electronic control unit 18 and / or the motor housing 34 , Preferably, heat-emitting electronic components 40 the electronic control unit 18 on these wall elements 36 attached, so that a good heat conduction to the hydraulic fluid in the motor housing 34 given is. This also makes the electronic control unit 18 in a simple manner by the hydraulic fluid in the motor housing 34 cooled.

In a first embodiment according to 1 is a hydraulic fluid reservoir 42 provided solely through the motor housing 34 with the hydraulic circuit 8th communicates. The hydraulic fluid reservoir 42 may be an open pressure medium reservoir standing under atmospheric pressure. The 1 However, shows a variant of the electro-hydraulic vehicle steering system 6 with closed hydraulic circuit 8th , without "open tank", that is to say without a pressure medium reservoir which is under atmospheric pressure 42 provided, which in the entire hydraulic circuit 8th , especially in the motor housing 34 , maintains a minimum hydraulic pressure, which is preferably between the atmospheric pressure and about 10 bar, in particular about 3 to 5 bar.

Although the hydraulic fluid reservoir 42 in 1 separate from the motor-pump unit 20 In alternative embodiments, it can also be incorporated into the engine-pump unit 20 be integrated. Furthermore, in the hydraulic circuit 8th Also, a valve unit may be provided with at least one hydraulic valve, wherein the valve unit also in the motor-pump unit 20 can be integrated, more preferably even in the motor housing 34 is housed. This valve unit preferably comprises the electromagnetically actuated fail-safe valve 32 ,

According to 1 indicates the hydraulic circuit 8th two check valves 44 on the pump suction side, a hydraulic connection to the motor housing 34 release and pump pressure side a hydraulic connection to the motor housing 34 lock. This allows these valves 44 a suction of Hydraulic fluid through the motor housing 34 , but at the same time prevent a high pressure load on the motor housing on the pump pressure side 34 , With regard to its tightness, the motor housing 34 accordingly only for the low pressure in the hydraulic fluid reservoir 42 be designed.

The hydraulic circuit 8th according to 1 has two more check valves 46 on the pump suction side a hydraulic direct connection to the cylinder / piston unit 26 Lock and pump pressure side a hydraulic direct connection to the cylinder / piston unit 26 release. These valves 46 ensure a sufficient hydraulic fluid flow through the motor housing on the pump suction side 34 by blocking the parallel, lower flow resistance direct connection. At the same time they allow pump pressure side a simple and fast fluid supply to the respective working chamber 28 . 30 ,

Because the direct connection between the hydraulic pump 24 and the cylinder / piston unit 26 Pump suction through the check valves 46 is locked, the hydraulic fluid via a directional control valve 48 and the motor housing 34 and one of the check valves 44 be supplied to the pump suction. In the present example, the directional control valve 48 a hydraulically controlled 3/3-way valve with a throttled open center. Through the open center takes place in an advantageous manner, a pressure equalization between the working chambers 28 . 30 instead, when the vehicle steering system 6 is in a neutral position, so no power assistance is desired (eg when driving straight ahead). Furthermore, by the open center, a continuous response of the way valve designed as a shuttle valve 48 reached. The 3/3-way valve 48 is by springs 50 acted upon in its central basic position, in which the motor housing 34 and the working chambers 28 . 30 each throttled connected to each other.

If the pressure in one of the working chambers rises 28 . 30 due to a pump actuation, the directional valve becomes 48 switched so that the motor housing due to its hydraulic control 34 always with the working chamber 28 . 30 communicates, which has the lower hydraulic pressure.

In the first embodiment of the vehicle steering system 6 according to 1 So flows through the entire of the hydraulic pump 24 sucked hydraulic fluid, the motor housing 34 before applying increased pressure to one of the working chambers 28 . 30 can be delivered. The flow in the motor housing 34 of the trained as Naßläufer electric motor 22 in this case provides a particularly good cooling of the engine 22 as well as the electronic control unit 18 for sure.

The 2 shows a second embodiment of the electro-hydraulic vehicle steering system 6 according to the first embodiment according to 1 very similar. To avoid repetition, the above description of the 1 referenced and only on two additional, preloaded check valves 52 more specifically, through which the first and second embodiments differ. The two preloaded check valves 52 are each parallel to the check valves 46 switched and give from a pre-definable pressure difference between a suction side of the pump 24 and the respective associated working chamber 28 . 30 a hydraulic direct connection free. From this predeterminable pressure difference therefore no longer has the entire delivery volume of the pump 24 through the motor housing 34 flow, but may alternatively via the preloaded check valve 52 to the suction side of the pump 24 reach. This creates a suction load on the pump 24 limited and prevents excessive pressure drop at the pump suction, so that occurrence of cavitation is largely excluded.

The 3 shows a third embodiment of the electro-hydraulic vehicle steering system 6 , which differs from the second embodiment according to 2 only differs in that the preloaded check valves 52 by throttling 54 are replaced. In contrast to the second embodiment, the direct connection between the suction side of the pump 24 and the cylinder / piston unit 26 not pressure-dependent opened or closed, but has pressure-independent on a constant throttle cross section. That of the pump 24 pumped hydraulic fluid volume is thus always composed of a volume fraction, via the motor housing 34 was promoted, and a volume fraction over one of the chokes 54 was sucked. This measure also relieves the pressure on the pump 24 On its suction side and on the suction side ensures a minimum hydraulic pressure at which the occurrence of cavitation phenomena is largely excluded.

The 4 shows a fourth embodiment of the electro-hydraulic vehicle steering system 6 in which, unlike the aforementioned embodiments, the hydraulic fluid does not have the motor housing 34 is sucked. The hydraulic circuit 8th has a opened in both directions direct connection between the working chambers 28 . 30 the cylinder / piston unit 26 and the pressure or suction side of the pump 24 on, so that hydraulic fluid directly from a working chamber 28 . 30 over the pump 24 to the other working chamber 30 . 28 is encouraged. The hydraulic pump 24 points in this case a leak oil connection 56 on, about the leak oil from the pump 24 over the motor housing 34 in the hydraulic fluid reservoir 42 arrive and from there via the motor housing 34 and one of the check valves 44 to the suction side of the pump 24 can flow back. The hydraulic fluid reservoir 42 is also in this embodiment exclusively on the motor housing 34 with the hydraulic circuit 8th in conjunction so that all through the hydraulic fluid reservoir 42 To be compensated volume fluctuations in the hydraulic circuit 8th (eg, due to temperature changes) hydraulic fluid flow in the motor housing 34 cause. However, since the leakage flow and the volume balance flow in the motor housing 34 compared to the hydraulic fluid flow according to the embodiments 1 to 3 lower fails, is in the motor housing 34 one with the electric motor 22 coupled and lapped by the hydraulic fluid rotation element 58 intended. The rotation element 58 can either a z. B. by grooving or bore specially designed rotor of the electric motor 22 be, or a rotor, by suitable gap widths in combination with fixed guide ribs within the motor housing 34 generates a drag flow, or an impeller, with the rotor of the electric motor 22 is coupled. In any case, the hydraulic fluid in the motor housing 34 during operation of the pump 22 through the rotation element 58 circulated, this circulation of the hydraulic fluid to an improved cooling of the engine 22 as well as the electronic control unit 18 contributes and thus the reduced flow through the motor housing 34 balances.

A fifth embodiment of the electro-hydraulic vehicle steering system 6 according to 5 indicates a further improved cooling of the engine 22 and the electronic control unit 18 and otherwise corresponds to the embodiment according to 4 , For better cooling of the hydraulic fluid are in housing walls 60 of the motor housing 34 hydraulic channels 62 formed, these hydraulic channels 62 Part of a connection line 64 between the pump 24 and the working chambers 28 . 30 the cylinder / piston unit 26 are. About the circulated hydraulic fluid in the motor housing 34 is in this embodiment, a good heat conduction between the electronic control unit 18 or the electric motor 22 on the one hand and the hydraulic fluid in the hydraulic channels 62 of the hydraulic circuit 8th on the other hand. Thus, the connecting lines 64 used as a cooling loop to the electric motor 22 and the electronic control unit 18 to cool.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4040003 A1 [0002]

Claims (20)

Electrohydraulic vehicle steering system with a hydraulic circuit ( 8th ), which is a pump ( 24 ) and a cylinder / piston unit ( 26 ), and an electric motor ( 22 ) housed in a motor housing ( 34 ) and the pump ( 24 ), whereby the pump ( 24 ) is reversible and dependent on a drive direction of the electric motor ( 22 ) optionally a first working chamber ( 28 ) or a second working chamber ( 30 ) of the cylinder / piston unit ( 26 ) subjected to a hydraulic pressure, characterized in that the motor housing ( 34 ) to the hydraulic circuit ( 8th ) is connected and filled with hydraulic fluid. Vehicle steering system according to Claim 1, characterized in that the motor housing ( 34 ) during operation of the pump ( 24 ) is flowed through by a hydraulic fluid. Vehicle steering system according to claim 1 or 2, characterized by a to the motor housing ( 34 ) adjacent, electronic control unit ( 18 ), by the electric motor ( 22 ) by wall elements ( 36 ) is separated, which have a good thermal conductivity. Vehicle steering system according to one of the preceding claims, characterized by a hydraulic fluid reservoir ( 42 ), via the motor housing ( 34 ) to the hydraulic circuit ( 8th ) connected. Vehicle steering system according to one of the preceding claims, characterized by a hydraulic fluid reservoir ( 42 ), which is exclusively via the motor housing ( 34 ) with the hydraulic circuit ( 8th ). Vehicle steering system according to claim 4 or 5, characterized in that the hydraulic fluid reservoir ( 42 ) is designed as a low-pressure accumulator and the hydraulic circuit ( 8th ) is applied with a desired hydraulic pressure. Vehicle steering system according to one of the preceding claims, characterized in that the hydraulic circuit ( 8th ) a valve unit with at least one hydraulic valve ( 48 ), wherein the valve unit is part of a motor-pump unit. Vehicle steering system according to one of the preceding claims, characterized in that the hydraulic circuit ( 8th ) a valve unit with at least one hydraulic valve ( 48 ), wherein the valve unit in the motor housing ( 34 ) is housed. Vehicle steering system according to one of the preceding claims, characterized in that the hydraulic circuit ( 8th ) two check valves ( 44 ), the pump suction on a hydraulic connection to the motor housing ( 34 ) and on the pump pressure side a hydraulic connection to the motor housing ( 34 ) lock. Vehicle steering system according to one of the preceding claims, characterized in that the hydraulic circuit ( 8th ) two check valves ( 46 ), the pump suction on a hydraulic direct connection to the cylinder / piston unit ( 26 ) lock and pump pressure side a hydraulic connection to the cylinder / piston unit ( 26 ). Vehicle steering system according to one of the preceding claims, characterized in that the hydraulic circuit ( 8th ) two biased in their blocking position check valves ( 52 ), in each case from a predeterminable pressure difference between a suction side of the pump ( 24 ) and the respective associated working chamber ( 28 . 30 ) release a hydraulic direct connection. Vehicle steering system according to one of the preceding claims, characterized in that the hydraulic circuit ( 8th ) two throttles ( 54 ), which both pump suction side and pump pressure side a throttled direct connection to the cylinder / piston unit ( 26 ) to ensure. Vehicle steering system according to one of the preceding claims, characterized in that the motor housing ( 34 ) via a directional control valve ( 48 ) with the cylinder / piston unit ( 26 ) is in hydraulic communication. Vehicle steering system according to claim 13, characterized in that the directional control valve ( 48 ) is a hydraulically controlled 3/3-way valve. Vehicle steering system according to claim 13 or 14, characterized in that the directional control valve ( 48 ) is a shuttle valve with throttled open center. Vehicle steering system according to one of the preceding claims, characterized in that the pump ( 24 ) via a leakage oil connection ( 56 ) with the motor housing ( 34 ). Vehicle steering system according to one of the preceding claims, characterized in that in the motor housing ( 34 ) with the electric motor ( 22 ) coupled and surrounded by hydraulic fluid rotary element ( 58 ) is provided. Vehicle steering system according to claim 17, characterized in that the rotation element ( 58 ) a grooved rotor of the electric motor ( 22 ). Vehicle steering system according to claim 17, characterized in that the rotation element ( 58 ) is an impeller. Vehicle steering system according to one of the preceding claims, characterized in that in housing walls ( 60 ) of the motor housing ( 34 ) Hydraulic channels ( 62 ) are integrated, these hydraulic channels ( 62 ) Part of a connection line ( 64 ) between the pump ( 24 ) and the working chambers ( 28 . 30 ) of the cylinder / piston unit ( 26 ) are.