Hydraulic system with dry sump

Abstract

A hydraulic supply system (100), in particular for a drive machine (115) of a motor vehicle, comprises a storage container (125) for a hydraulic medium (110); a supply line (135) for providing the hydraulic medium (110) from the storage container (125) to a cooling or lubricating point (105), the hydraulic medium (110) which emerges from the cooling or lubricating point (105) being collected in a sump (150); and a bilge pump (130) which is designed to deliver the hydraulic medium (110) from the sump (150) into the storage container (125). The pump capacity of the bilge pump (130) exceeds a volume flow of medium (110) flowing through the supply line (135) such that the bilge pump (130) can deliver a mixture of hydraulic medium (110) and air. The storage container (125) is in the form of a pressure container, the internal pressure of which can exceed the ambient pressure; and a compressed air motor (140) for driving the bilge pump (130) is provided, the compressed air motor (140) being supplied with air from the storage container (125).

Description

[0001] ZF Friedrichshafen AG File 304253 Friedrichshafen 2024-09-13

[0002] Hydraulic system with dry sump

[0003] The present invention relates to a hydraulic system with a dry sump, in particular for a drive motor of a motor vehicle.

[0004] A motor vehicle's engine is lubricated and cooled by means of a hydraulic fluid. This fluid is pumped to the cooling and lubrication points by a pressure pump. Fluid escaping from these points collects in a sump. In a dry sump system, a bilge pump transfers the fluid from the sump to a reservoir, from where the pressure pump can be supplied with fluid.

[0005] DE 10 2016 211 226 B3 proposes such a supply system for a motor vehicle's drive unit. In this system, the bilge pump and the pressure pump are driven on a common shaft by an electric motor.

[0006] To ensure a sufficient supply of fluid from the dry sump at all times, the bilge pump is typically designed for a higher flow rate than the pressure pump. Due to the rigid coupling between the bilge and pressure pumps, the bilge pump can continuously deliver a higher flow rate than the pressure pump. If there is insufficient fluid in the sump to meet this flow rate, the bilge pump may draw air into the hopper. Controlling the system to simultaneously ensure an adequate supply of fluid to a cooling or lubrication point and maintain a predetermined fill level in the sump or hopper can be challenging.

[0007] One object of the present invention is to provide an improved hydraulic supply system, particularly for the drive motor of a motor vehicle. The invention achieves this object by means of the subject matter of the independent claims. Dependent claims describe preferred embodiments. ZF Friedrichshafen AG File 304253 Friedrichshafen 2024-09-13

[0008] A hydraulic supply system, particularly for the drive motor of a motor vehicle, comprises a reservoir for hydraulic fluid; a supply line for delivering hydraulic fluid from the reservoir to a cooling or lubrication point, with hydraulic fluid exiting the cooling or lubrication point being collected in a sump; and a bilge pump configured to pump hydraulic fluid from the sump into the reservoir. The pumping capacity of the bilge pump exceeds the volume flow of fluid through the supply line, enabling the bilge pump to pump a mixture of hydraulic fluid and air. The reservoir is designed as a pressure vessel whose internal pressure can exceed ambient pressure; and a compressed air motor is provided to drive the bilge pump, the compressed air motor being supplied with air from the reservoir.

[0009] The hydraulic medium can be, in particular, oil. The drive unit can be an internal combustion engine or an electric motor. A hybrid drive system with an electric motor and an internal combustion engine can also be powered by the hydraulic system. Optionally, a gearbox connected to the drive unit can also be powered by the hydraulic system.

[0010] Due to the high flow rate of the bilge pump, the reservoir can be pressurized, allowing hydraulic fluid to be drawn from it without the need for a pressure pump. Furthermore, the air that is drawn into the reservoir by the bilge pump during many operating conditions of the hydraulic system can be used to build up pressure. The gaseous component in the reservoir can act as a kind of pressure accumulator, so that the pressure in the reservoir drops only slowly when more hydraulic fluid is discharged than supplied. This allows the hydraulic system to better bridge periods of reduced inflow or increased outflow without significantly reducing the volume of fluid supplied.

[0011] By using air from the reservoir to drive the bilge pump, losses caused by excessive pumping of air from the sump into the ZF Friedrichshafen AG file 304253 Friedrichshafen 2024-09-13

[0012] The need for storage tanks can be reduced. Furthermore, by controlling the volume flow of air into the compressed air motor, the pressure in the storage tank can be easily controlled to a predetermined value.

[0013] The hydraulic system can be manufactured and operated economically. A drive motor, particularly a motor vehicle, powered by the hydraulic system can be maintained with improved operational reliability.

[0014] Preferably, in addition to the pneumatic motor, an additional drive for the bilge pump is provided. This additional drive can supply mechanical power to the bilge pump, while the pneumatic motor can relieve the load on the additional drive.

[0015] In one embodiment, the hydraulic system includes a drive shaft to which an additional drive, external to the system, can be connected. The additional drive can originate from an external source, in particular from the engine or another component of a motor vehicle. In another embodiment, the additional drive is integrated into the hydraulic system.

[0016] It is particularly preferred that the additional drive comprises an electric motor. The drive power of the electric motor can be controlled with minimal effort, allowing the system to be flexibly controlled, for example, with regard to different flow rates of medium supplied at the supply line or with regard to the fill level of medium in the sump or reservoir. Preferably, the electric motor is controlled in concert with other components of the hydraulic system.

[0017] A hydraulic fluid separator is preferably provided for the air from the reservoir. The pneumatic motor can be configured to tolerate a certain amount of hydraulic fluid in the supplied air. The separator ensures that this amount is not exceeded. Thus, as documented in ZF Friedrichshafen AG file 304253, Friedrichshafen, September 13, 2024, it can be prevented that the pneumatic motor is supplied with incompressible hydraulic fluid instead of compressible air.

[0018] In a simple embodiment, the separator can be integrated into the storage tank. For example, a mixture of hydraulic fluid and air can be introduced into an upper section of the storage tank, while hydraulic fluid for the supply line is drawn from a lower section. The shape and vertical extent of the storage tank can be chosen such that the gaseous and liquid phases separate. A foam can form in a central section of the storage tank, where segregation occurs due to the effects of gravity and / or the surface tension of the hydraulic fluid.

[0019] In a preferred embodiment, the separator comprises a centrifugal separator, which can also be called a cyclone, cyclone filter, or cyclone separator. An inflowing mixture of air and hydraulic medium is set into rotational motion by its own flow velocity through a suitably designed stationary separator. Liquid medium has a higher density than gaseous medium and is forced radially outwards within the separator, so that the gaseous component remains radially inside.

[0020] In another embodiment, a centrifuge can also be used, in which a rotational movement of a container acts on the incoming mixture. The centrifuge can be driven by a drive motor of the bilge pump or another drive. Alternatively, an air-permeable and pressure-resistant membrane can act as a separator. Another possibility for implementing the separator is a poppet valve, which can optionally be actuated by a float. If the level of hydraulic medium in a container of the separator rises, the float can be driven upwards and close the poppet valve. The same effect can occur if a foam consisting of air and hydraulic medium loses density because the air-to-medium ratio decreases. Closing the poppet valve prevents larger [ZF Friedrichshafen AG File 304253 Friedrichshafen 2024-09-13]

[0021] Quantities of the hydraulic medium may enter the supply line. This may cause a temporary increase in pressure in the reservoir.

[0022] In another embodiment, at least one additional bilge pump is provided, which draws fluid from a different point in the sump. The drives of the bilge pumps are rigidly coupled to each other. Such a design can be particularly advantageous if the sump can be tilted so that the hydraulic fluid can collect at different points. This can be the case, for example, on board a motor vehicle. The delivery capacity of each bilge pump can be at least as high as the flow rate through the supply line; however, a bilge pump is usually dimensioned for a larger flow rate, for example, approximately 120% or more of the flow rate through the supply line. In this example, the combined delivery capacity of both bilge pumps can be approximately 240% of the discharged flow rate, so a large quantity of air must be expected to be pumped.

[0023] The described hydraulic system can function without a pressure pump to deliver hydraulic fluid from the reservoir to a cooling or lubrication point. The fluid can be moved to the points of use solely due to the overpressure in the reservoir, which is generated by the bilge pump.

[0024] To prevent the reservoir from emptying when the system is shut down, i.e., when the bilge pump is stationary, a drain valve can be installed between the reservoir and the supply line. This ensures that hydraulic fluid is immediately available via the supply line when the hydraulic system is started. The drain valve can, for example, include a siphon. The siphon can have a predetermined volume that is available at the supply line when the system starts, before new fluid is pumped from the sump into the reservoir. In another embodiment, a space-saving pre-tensioned poppet valve can be used as a drain valve. The poppet valve can be pre-tensioned with an elastic element so that it only opens at a predetermined volume. ZF Friedrichshafen AG File 304253 Friedrichshafen 2024-09-13

[0025] The pressure difference between the inlet side facing the storage tank and the outlet side facing the supply line opens.

[0026] In yet another embodiment, a control valve is provided to regulate the flow rate of medium from the storage tank to the supply line. The control valve can also function as a dry-run prevention valve by closing when the system is switched off. The flow rate of medium through the supply line or the pressure of the medium in the supply line can be appropriately controlled during system operation.

[0027] In another embodiment, a nebulizer nozzle is provided for supplying a mist of air and hydraulic fluid. The nebulizer nozzle can be supplied with air from the reservoir. If an air separator is provided, the nebulizer nozzle can be supplied with air from which the hydraulic medium has already been largely separated. This allows the fact that the separated air always contains a residual amount of hydraulic medium, which can be used, in particular, for cooling or lubricating a low-stress area, to be utilized.

[0028] In yet another embodiment, a further pressure sink can be supplied with air. This further pressure sink can comprise any device. On board a motor vehicle, for example, the pressure sink can comprise another compressed air motor or a pneumatic actuator.

[0029] A control device for regulating the flow rate of the medium through the supply line is preferably provided. The control device can operate an additional drive motor for the bilge pump and / or a control valve for the flow rate through the supply line. The control device can operate based on sensor values ​​that can be provided by the system. In one embodiment, a temperature sensor and / or a pressure sensor are provided on the storage tank. Additional temperature or pressure sensors can be provided at other locations, for example, on the supply line or at a lubrication or cooling point. ZF Friedrichshafen AG File 304253 Friedrichshafen 2024-09-13

[0030] The hydraulic supply system can further include a switching valve for controlling the flow of hydraulic fluid from the supply line to different lubrication or cooling points. For example, a first point can be provided that is supplied with hydraulic fluid only in one position of the switching valve, and a second point that is supplied in both positions. In another embodiment, only the first point can be supplied with fluid from the supply line when the valve is not actuated, and only the second point when the valve is actuated. Other distribution strategies are also possible. Naturally, multiple first and / or multiple second points can also be provided.

[0031] The compressed air motor can, for example, be a vane motor. Alternatively, a piston motor or another positive displacement motor that can be driven by a gaseous medium can be used. A fluid motor can also be used, but is less preferred due to the expected fluctuating flow conditions.

[0032] Optionally, a bypass valve can be provided that allows airflow from the outlet side to the inlet side of the compressed air motor if the outlet pressure exceeds the inlet pressure.

[0033] According to yet another aspect of the present invention, a drive axle for a motor vehicle comprises a hydraulic supply system as described herein. The drive axle is designed to propel a motor vehicle and may include an electric drive motor and / or a transmission. Optionally, an input shaft for an internal combustion engine is also provided. A drive axle with an electric drive motor may also be called an electric drive axle.

[0034] According to yet another aspect of the invention, a motor vehicle comprises a drive axle as described herein. The motor vehicle can, in particular, comprise a motorcycle or a passenger car; other possible motor vehicles include a construction machine, an agricultural machine, a truck, or a bus.

[0035] The invention will now be described in more detail with reference to the attached figures, in which:

[0036] Figure 1 shows a hydraulic supply system in a first embodiment;

[0037] Figure 2 shows a hydraulic supply system in a second embodiment; and

[0038] Figure 3 shows a hydraulic supply system in a third embodiment.

[0039] Figure 1 shows a hydraulic supply system 100 in an exemplary first embodiment. The supply system 100 is configured to supply a number of lubrication or cooling points 105 with a hydraulic medium 110, which typically comprises oil. The points 105 are preferably located by a drive motor 115 for a motor vehicle 120.

[0040] The supply system 100 comprises a storage tank 125 for medium 110, a bilge pump 130, a supply line 135, and a compressed air motor 140. For illustrative purposes only, two bilge pumps 130 are shown connected in parallel, capable of drawing from different suction points. Instead of bilge pumps 130, appropriately designed internal gear pumps or a double-stroke vane pump with separate suction lines can also be used. More than two bilge pumps 130 or a corresponding multi-acting bilge pump 130 can also be provided.

[0041] A bilge pump 130 can be driven by a pneumatic motor 140 and a further drive motor 145. The pneumatic motor 140 is preferably designed as a vane motor; other embodiments are also possible. The further drive motor 145 is, by way of example, designed as an electric motor; other types of drive motor 145 are also possible. A bilge pump 130 pumps medium 110 from a sump 150 into the storage tank 125. The pumping capacity of a bilge pump 130 is sufficient to pump a mixture of medium 110 and a gaseous medium, usually air, from the sump 150 during normal operation of the supply system 100 or the drive motor 115. The two bilge pumps 130 can draw in water from different points in the sump 150, which may or may not carry medium 110 in different operating states of the drive machine 115.Optional filters 155 are preferably assigned individually to the bilge pumps 130.

[0042] The storage container 125 is pressure-resistant up to a predetermined pressure, for example, approximately 2-3 bar. An air separator 160 is preferably mounted in or on the storage container 125, separating a mixture of medium 110 and air. In one embodiment, the air separator 160 is designed as a centrifugal separator; other embodiments are also possible. Outgoing air is directed to an air distributor 165, which in a simple embodiment can be formed by a single pipe. If required, an atomizer nozzle 170 can be supplied with air. The air is usually not completely free of medium 110, and the atomizer nozzle 170 can be used to cool or lubricate a component that does not require a flow rate of medium 110.

[0043] Compressed air can be directed from the air distributor 165 to the pneumatic motor 140 to drive it. An optional pressure relief valve 175 can release air from the reservoir 125 to the pneumatic motor 140 as needed.

[0044] Medium 110 exiting the storage tank 125 can be directed into the supply line 135 via a throttle 180. A dry-run protection device 185 prevents the storage tank 125 from emptying due to gravity when the bilge pump 130 is not running. In this case, the dry-run protection device 185 is formed by a siphon; other embodiments are also possible. ZF Friedrichshafen AG File 304253 Friedrichshafen 2024-09-13

[0045] The medium 110 can then be passed through a heat exchanger 190 to cool it to a predetermined temperature. An optional filter 195 ensures that no foreign matter reaches the cooling or lubrication points 105.

[0046] Figure 2 shows a hydraulic supply system 100 in a second embodiment, which is based on the embodiment of Figure 1. Here, a controllable valve 205 is used instead of the throttle 180 to control the flow rate of medium 110 exiting the reservoir 125. The valve 205 can be controlled to block the flow rate when the supply system 100 is switched off and the bilge pump 130 is not running. A separate idle prevention device 185 is therefore unnecessary.

[0047] Optionally, the cooling or lubrication points 105 are divided into two groups, and a switching valve 210 is provided to control the flow of medium 110 to the points 105. The switching valve 210 can be actuated electrically or pressure-controlled. In a first position of the switching valve 210, only the cooling or lubrication points 195 shown in a lower row are supplied with medium 110, as shown in Figure 2. When the switching valve 210 is actuated, it assumes a second position in which the cooling or lubrication points 195 shown in an upper row are also supplied with medium 110.

[0048] Figure 3 shows a hydraulic supply system 100 in a third embodiment, which is based on the embodiments of Figures 1 and / or 2. For improved clarity, only those elements of the supply system 100 that are mentioned in the following text are provided with reference numerals. In this embodiment, for example, no compressed air motor 140 is provided.

[0049] In the illustrated embodiment, a control unit 305 is provided, which preferably operates electronically, in particular on the basis of a microcomputer or microcontroller. The control unit comprises at least one input 310 and at least one output 315. Signals at the inputs 310 and the outputs 315 are preferably electrical. ZF Friedrichshafen AG File 304253 Friedrichshafen 2024-09-13

[0050] The control unit 305 is configured to control the drive power of the additional drive motor 145. A speed signal from the additional drive motor 145 can be fed to the control unit 305 for feedback purposes. Furthermore, the control unit 305 can control the controllable valve 205 to regulate the flow rate of the medium 110 to the cooling or lubrication points 105.

[0051] The control unit 305 can control the additional drive motor 145 such that a predetermined pressure is established in the reservoir 125. Additionally, the control unit can ensure that a predetermined level of medium in the sump 150 is not exceeded. Optionally, the air separator 160 can be controlled to release air from the reservoir 125. A controllable or switchable valve can also be provided instead of the air separator 160.

[0052] Controls can be implemented based on sensor values ​​acquired by sensors on the supply system 100. In particular, a temperature sensor 320 and / or a pressure sensor 325 can be provided on the storage tank 125.

[0053] Additionally, a further temperature sensor 330 can be provided in the area of ​​a supply to the cooling or lubrication points 105. The control unit 305 can control the switching valve 210 depending on the temperature of the supplied medium 110. The temperature of the supplied medium can also be taken into account for controlling the additional drive motor 145 and / or the controllable valve 205. Conversely, the switching valve 210 can also be controlled depending on a pressure or a temperature at the reservoir 125.

[0054] ZF Friedrichshafen AG File 304253 Friedrichshafen 2024-09-13

[0055] Reference mark

[0056] 100 hydraulic supply system

[0057] 105 Cooling or lubrication point

[0058] 110 Medium

[0059] 115 Drive machine

[0060] 120 motor vehicles

[0061] 125 storage containers

[0062] 130 bilge pump

[0063] 135 Supply line

[0064] 140 compressed air motor

[0065] 145 additional drive motor

[0066] 150 swamp

[0067] 155 filters

[0068] 160 air separators

[0069] 165 air distributors

[0070] 170 Nebulizer nozzle

[0071] 175 Pressure relief valve

[0072] 180 Throttle

[0073] 185 Idle fuse

[0074] 190 heat exchangers

[0075] 195 filters

[0076] 205 controllable valve

[0077] 210 switching valve

[0078] 305 Processing unit

[0079] 310 Entrance

[0080] Exit 315

[0081] 320 temperature sensor

[0082] 325 Pressure sensor

[0083] 330 temperature sensor

Claims

ZF Friedrichshafen AG File 304253 Friedrichshafen 2024-09-13 Patent claims 1. Hydraulic supply system (100), in particular for a drive motor (115) of a motor vehicle, wherein the supply system (100) comprises the following elements: - a reservoir (125) for hydraulic medium (110); - a supply line (135) for providing hydraulic medium (110) from the reservoir (125) to a cooling or lubrication point (105), wherein hydraulic medium exiting from the cooling or lubrication point (105) (110) is collected in a swamp (150); - a bilge pump (130) designed to pump hydraulic medium (110) from the sump (150) into the reservoir (125); - wherein the delivery capacity of the bilge pump (130) exceeds the volume flow of medium (110) flowing through the supply line (135), so that the bilge pump (130) can pump a mixture of hydraulic medium (110) and air; - wherein the storage container (125) is designed as a pressure vessel whose internal pressure can exceed ambient pressure; and - a compressed air motor (140) is provided to drive the bilge pump (130), wherein the compressed air motor (140) is supplied with air from the reservoir (125).

2. Supply system (100) according to claim 1, wherein, in addition to the compressed air motor (140), an additional drive for the bilge pump (130) is provided.

3. Supply system (100) according to claim 2, wherein the additional drive comprises an electric motor.

4. Supply system (100) according to one of the preceding claims, further comprising a separator (160) for hydraulic medium (110) from the air from the storage tank (125). ZF Friedrichshafen AG File 304253 Friedrichshafen 2024-09-13 5. Supply system (100) according to claim 4, wherein the separator (160) comprises a centrifugal separator.

6. Supply system (100) according to one of the preceding claims, wherein at least one further bilge pump (130) is provided which draws from another location in the sump (150), wherein the drives of the bilge pumps (130) are rigidly coupled to each other.

7. Supply system (100) according to one of the preceding claims, wherein an idle prevention device (185) is provided between the storage container (125) and the supply line (135).

8. Supply system (100) according to one of the preceding claims, further comprising a control valve (205) for controlling a volume flow of medium (110) from the storage container (125) to the supply line (135).

9. Supply system (100) according to one of the preceding claims, further comprising a nebulizer nozzle (170) for providing a mist of air and hydraulic fluid.

10. Supply system (100) according to one of the preceding claims, further comprising a control device (305) for controlling a volume flow of the medium (110) through the supply line (135).

11. Supply system (100) according to one of the preceding claims, further comprising a switching valve (210) for controlling hydraulic medium (110) from the supply line (135) to different lubrication or cooling points.

12. Supply system (100) according to one of the preceding claims, wherein the compressed air motor (140) comprises a vane motor. ZF Friedrichshafen AG File 304253 Friedrichshafen 2024-09-13 13. Drive axle for a motor vehicle, comprising a supply system (100) according to any of the preceding claims.

14. Motor vehicle (120) comprising a drive axle according to claim 13.

Images