DE102022117155A1 - Hydraulic supply system and aircraft with such a hydraulic supply system - Google Patents

Abstract

The invention relates to a hydraulic supply system for supplying hydraulic consumers of an aircraft with a hydraulic fluid, comprising at least one hydraulic pump, at least one motor and at least one accumulator. To provide the hydraulic fluid with a variable volume flow or constant pressure level, the speed of the motor and the hydraulic pump are variably adjustable.

Description

The present invention relates to a hydraulic supply system according to the features of the preamble of patent claim 1. The invention further relates to an aircraft with such a hydraulic supply system.

Hydraulic supply systems are generally known from the prior art, which supply hydraulic consumers with a variable volume flow. Hydraulic pumps are driven by electric motors. Such hydraulic pumps coupled to an electric motor are referred to as electric motor pumps.

Modern hydraulic supply systems are designed in such a way that very low flows are possible, although this requires a speed below a minimum speed.

A solution known from the prior art to enable a low flow is to create a bypass. Creating a bypass enables a minimum flow in the control circuit. However, the disadvantage of this variant is that the bypass generates additional losses, thereby reducing the maximum flow that can be generated.

A hydraulic pump in a modern hydraulic supply system usually has a capacity of around 5 cc/REV, requiring a minimum speed of around 1000 rpm. Under these conditions, the hydraulic pump is able to deliver a flow of 5 l/min. Small hydraulic supply systems can require flow rates of approx. 1 l/min, so that 4 l/min is converted into heat by the applied bypass. In a modern hydraulic supply system with a system pressure of approximately 210 bar, the heat output generated by the bypass corresponds to approximately 1.4 kW. Such supply systems are designed to be thermally sensitive, so that the heat output generated by the bypass significantly impairs the efficiency and therefore has a detrimental effect on the hydraulic supply system as a whole. Therefore, this solution is not suitable for hydraulic supply systems that require low flows.

Another variant known from the prior art to provide a variable volume flow is to drive a constant hydraulic pump by a controllable electric motor. However, due to the mechanical design of the electric motor pump, a minimum motor speed is required to guarantee a long service life of the hydraulic pump. In smaller hydraulic supply systems, which, as already mentioned above, require flow rates of approx. 1 l/min, the motor speed of the electric motor pump with a constant displacement volume must be reduced significantly in order to enable the low flow rate. At the same time, however, the displacement volume cannot be chosen to be arbitrarily small, since certain requirements are placed on high flow rates. The displacement depends on the flow and the engine speed, so that when very low or very large flows are provided, the displacement is limited by a maximum permissible speed. $$ScHluckvOlumen=\frac{DurcHfluss}{MOtOrdreH\mathrm{e.g}aHl}$$

Speeds that are too low lead to increased wear due to the lack of fluid friction in the hydraulic pump. Furthermore, the dynamics of the hydraulic pump reaction is limited due to the high differences between the minimum and maximum engine speed, which places high demands on the control technology. The ability to limit the engine speed and at the same time dissipate the excess volume flow via an additional throttle between the hydraulic pump outlet and a reservoir leads to high heat loss and overall poorer efficiency. Therefore, this variant is also not suitable for providing very low flows, in particular resting flows, in a hydraulic supply system.

Proceeding from this, the object of the invention is to create an improved hydraulic system of the type mentioned at the outset, to avoid the disadvantages of the prior art and to further develop the latter in an advantageous manner. In particular, both a variable control of the volume flow and the pressure level as well as a constant control of the volume flow and the pressure level should be made possible without putting a lot of strain on the hydraulic pump or the motor. The volume flow is regulated depending on the operation.

According to the invention, this object is achieved by a hydraulic supply system according to claim 1. With regard to the aircraft, the task is solved by the subject matter of claim 10.

Specifically, the task is solved by a hydraulic supply system for supplying hydraulic consumers of an aircraft with a hydraulic fluid, comprising at least one hydraulic pump, at least one motor and at least one accumulator. To provide of the hydraulic fluid with variable volume flow or constant pressure level, the speed of the motor and the hydraulic pump are variably adjustable.

The invention has the essential advantage that in order to provide a variable volume flow, in particular a very low or a very large volume flow, volume flow changes can be compensated for both by adjusting the engine speed, in particular the engine speed, and by adjusting the hydraulic pump. This combination allows the motor-pump unit to be made more compact and therefore lighter overall. With multiple control circuits in an aircraft, such as an airplane, the overall weight of the aircraft is significantly reduced.

A further advantage of the invention is that this combination significantly improves the control dynamics over the entire flow range compared to the prior art. In other words, the response of the hydraulic supply system improves. The supply system does not react as sluggishly to changes in speed, especially to changes in flow, as in the prior art. The improved response behavior in turn prevents pressure peaks.

Another advantage of the invention is that by operating the motor-pump unit at a minimum speed, the service life of the mechanical components is significantly extended and the noise level is significantly reduced.

Preferred embodiments of the invention are specified in the subclaims.

In the present application, the term volume flow, flow rate or flow rate means the quantity, in particular the volume of a hydraulic fluid per unit of time through a defined cross section or, in other words, the quantity of a hydraulic fluid that covers a certain distance in the hydraulic control circuit within a certain time . The unit liters per minute (l/min) is defined for this.

In a preferred embodiment, the motor can be operated at a minimum speed to provide a very low or no volume flow. Under certain conditions it may be necessary to provide the flow completely or to a very small extent. This can be the case, for example, when the actuators and/or control elements are in a de-energized state or standby mode. A very low volume flow is understood to mean a resting flow. The resting flow is a minimum flow that is provided by a speed below the minimum speed or by the minimum speed of the motor itself and corresponds to a volume flow of approximately 1 l/min. The resting flow creates a film on the impellers of the hydraulic pump, so that the hydraulic pump is sufficiently supplied with moisture and, in particular, lubricated. The service life of the hydraulic pump is extended by the quiescent flow or moisture lubrication.

In a further preferred embodiment, the motor can be operated at a maximum speed to provide a very high volume flow. Under certain conditions it may be necessary to provide a very large flow. This can be the case, for example, when the actuators and/or control elements are in an activated state and perform a specific function. A very high volume flow is understood to mean the maximum volume flow that is provided by the maximum speed of the motor and corresponds to a volume flow of approximately 50 I/min. Depending on the design of the hydraulic supply system, the maximum volume flow can be larger or smaller than 50 l/min in a further preferred embodiment.

The volume flow can be continuously regulated or kept constant in the minimum range, maximum range and in between. In other words, a very low, very high or any volume flow can be continuously variably regulated or kept constant.

Preferably, the engine comprises a control device for continuously variable change or constant maintenance of the engine speed, which also includes the case that the engine is connected to such a control device. The displacement volume, the volume flow or flow and the engine speed are dependent on one another. With a constant displacement volume of the hydraulic pump, a very low volume flow requires a very low engine speed and a very high volume flow requires a very high engine speed. Consequently, a constant volume flow requires a constant engine speed. The control device enables a continuously variable change or constant maintenance of the motor speed regardless of the mains frequency of the motor in a predefined speed band.

The engine preferably includes a cooling device. The hydraulic can preferably be used likfluid can be used as a cooling medium to cool the engine. The cooling device may be connected to the control device so that heat losses from the engine can be released into the hydraulic fluid.

In a further preferred embodiment, the hydraulic pump is adjustable by a swivel plate. By adjusting the hydraulic pump using the swash plate, it is possible to operate the engine at a minimum speed and at the same time to provide a very low volume flow of around 1 l/min. On the other hand, by adjusting the swash plate, it is again possible to operate the motor at maximum speed and at the same time provide a very high volume flow of 50 l/min. By adjusting the swash plate, the displacement volume of the hydraulic pump can be adjusted, so that the displacement volume of the hydraulic pump can be increased or reduced. In other words, a resting flow and maximum flow or any other variable flow can be provided by adjusting the hydraulic pump using the swashplate.

Preferably, the swivel plate can be pivoted depending on or independently of the system pressure. The displacement volume, the volume flow or the flow as well as the direction of the volume flow or flow are regulated by the adjustment of the swashplate, in particular by the angle of attack of the swashplate. The volume flow is in turn directly proportional to the pressure, so that increasing the pressure provides a higher volume flow and reducing the pressure provides a reduced volume flow, whereby the swash plate is in a swung-in state.

In a further preferred embodiment, a reservoir is provided which is connected to the connections of the hydraulic pump. The hydraulic pump has at least two connections, each of which includes a pump line. A pump line means that a line leads to or from the pump. In other words, one connection of the hydraulic pump comprises a hydraulic pump supply line and the other connection includes a hydraulic pump discharge line, so that the reservoir is hydraulically connected to the hydraulic pump through the hydraulic pump supply line and/or the hydraulic pump discharge line.

The accumulator is preferably designed as a piston accumulator, in particular as a spring accumulator. The memory designed as a piston accumulator, in particular as a spring accumulator, can include a level sensor, in particular an integrated level transducer (LVT), which is suitable for compensating the temperature. Furthermore, the memory is designed in such a way that it can maintain a reserve in the event of a leak, in particular supplying and draining the hydraulic fluid from the reservoir.

At this point it should be noted that the terms “a” and “an” do not necessarily refer to exactly one of the elements, although this is a possible embodiment, but can also refer to a plurality of the elements. Likewise, the use of the plural also includes the presence of the element in question in the singular and, conversely, the singular also includes several of the elements in question.

Furthermore, all of the features of the invention described herein can be combined with one another as desired or claimed in isolation from one another.

Further details and advantages of the invention are explained in more detail using an exemplary embodiment shown in the drawing.

• 1: eine schematische Darstellung des erfindungsgemäßen Regelkreises mit einem variabel verstellbaren Motor und einer variaben verstellbaren Hydraulikpumpe.

This shows

• 1 : a schematic representation of the control circuit according to the invention with a variably adjustable motor and a variably adjustable hydraulic pump.

1 shows a control circuit according to the invention with a hydraulic pump 10, a motor 20, a reservoir 30, a memory 40 and a hydraulic consumer 50.

The hydraulic pump 10 has a hydraulic pump supply line 10z and a hydraulic pump discharge line 10a. The hydraulic pump 10 is hydraulically connected to the accumulator 40 and the hydraulic consumer 50 through the hydraulic pump derivative 10a. The hydraulic pump 10 is also hydraulically connected to the reservoir 30 through the hydraulic pump discharge line 10a and through the hydraulic pump supply line 10z. The hydraulic fluid flows through the hydraulic consumer 50 via the hydraulic pump discharge line 10a and flows back through the reservoir 30 via the hydraulic pump supply line 10z to the hydraulic pump 10.

It is conceivable that in a further preferred embodiment a connection of a safety valve is provided between the hydraulic pump 10 and the reservoir 30. It is conceivable that in a further preferred embodiment a device for measuring the output pressure is provided directly in the area of the hydraulic pump outlet. It is It is conceivable that in a further preferred embodiment the hydraulic pump output and the hydraulic pump input are connected by a pressure relief valve or a safety valve. It is conceivable that in a further preferred embodiment one or more filters and/or outlet check valve is provided between the hydraulic pump 10 and the hydraulic consumption 50. It is conceivable that in a further preferred embodiment the accumulator 40 is connected between the outlet check valve and the hydraulic consumer 50 by a corresponding line.

The motor 20 is preferably designed as a permanent magnet synchronous motor and drives the hydraulic pump 10. The engine 20 is controlled via a control device which increases, reduces or keeps the rotational speed, in particular the rotational speed of the engine 20, constant on the basis of an output pressure of the hydraulic pump 10 detected by a sensor, the increase or reduction of the engine speed occurring in particular continuously. The control device can be supplied with electrical energy via a VDC busbar and can also be set up to switch the hydraulic pump 10 on and off, carry out start-up tests, monitor overheating of the hydraulic pump 10 and create error messages.

The control device can be operated in a heating mode in order to avoid the high engine loads that occur when starting the hydraulic pump 10 at a low temperature of the hydraulic fluid, in particular below -20 degrees Celsius. For example, the control device can keep the speed of the motor 20 at a constant value until the temperature of the hydraulic fluid increases and, for example, reaches a value of 0 degrees Celsius.

The engine 20 has a cooling device that can use the hydraulic fluid as a cooling medium for cooling the engine 20. The cooling device may be connected to the control device so that heat losses from the engine 20 can be released into the hydraulic fluid.

The motor 20 can be connected to other systems such as the on-board computer of an aircraft via a BUS supply (Aircraft BUS Supply).

The housing outlet or the housing drain from the engine 20 can be guided through a housing outlet filter (CD filter), which protects the system from contamination of the hydraulic pump. The temperature of the hydraulic fluid can be measured in an area in front of the CD filter.

In the prior art, the motor is operated at a constant speed depending on the mains frequency. This means that the motor can only have speeds that are dependent on the mains frequency and can be regulated in stages, with the speed levels being very high. For example, the motor in the prior art with a number of pole pairs of 3 has a speed of 8000 rpm at a mains frequency of 400 Hz. In a different speed level or network frequency, the motor has a different speed that is dependent on the network frequency. This results in the maximum flow being reduced at low engine speeds.

In comparison to the prior art, the speed of the motor 20 can be continuously regulated or kept constant by the control device in a predetermined speed band. The continuously variable control or constant maintenance of the motor speed takes place independently of the mains frequency of the motor 20.

The memory 40 is a pressure accumulator or pressure vessel. The memory 40 can preferably be designed as a piston accumulator, in particular preferably as a spring accumulator. The memory 40 makes it possible to maintain the pressure generated by the hydraulic pump 10 and to store the energy generated thereby and to release it back into the control circuit when necessary.

In the case of the embodiment of the memory 40 as a piston accumulator, the hydraulic fluid is pumped by the hydraulic pump 10 into the memory 40, where it is stored under gas pressure, a gas present in the memory 40 and the pumped hydraulic fluid being separated from one another by a piston. When the pressure in the control circuit increases, the hydraulic fluid collects in the reservoir 40, whereby the piston is displaced and thereby compresses the gas present in the reservoir 40. If the pressure drops, the compressed gas expands again and thereby displaces the stored hydraulic fluid from the accumulator 40 back into the hydraulic circuit.

In the case of the embodiment of the accumulator 40 as a spring accumulator, a spring is used for pressure loading, with the release of the hydraulic fluid back into the control circuit depending on the hardness of the spring. This embodiment is particularly suitable for very small memories. Furthermore, the memory allows 40 pressure peaks to be reduced

The hydraulic consumer 50 is shown representatively and can in particular be the primary Flight controls (primary flight controls) such as the elevator, rudder and ailerons and / or buoyancy control devices such as spoilers and ground spoilers. The hydraulic consumer 50 may include the nose and main landing gear including the flap actuators, the high-lift system for flaps and slats, the cargo and passenger doors, the normal and emergency brakes, the steering, controls and thrust reverser and / or the like.

Through the continuous adjustment of the engine speed, in particular the engine speed of the engine 20, independently of the mains frequency and the adjustment of a swashplate, not shown here, of the hydraulic pump 10, which is only adjusted when the flow of the hydraulic consumer 50 is below a minimum speed of equivalent flow, this becomes Hydraulic fluid is provided with a variable volume flow or constant pressure level.

Specifically, the speed of the motor 20 is controlled by a control loop, with the minimum speed of the motor 20 being selected such that the hydraulic pump 10 operates at a stable operating point. The swashplate, not shown here, pivots from a certain pressure until it no longer provides any flow. The engine speed is increased as soon as the hydraulic consumer 50 requires a higher flow than the hydraulic pump discharge. In the event that the hydraulic consumer 50 requires a lower speed than the minimum speed, the flow is ensured by adjusting the swash plate. In other words, the pressure at the hydraulic pump output decreases when the hydraulic consumer 50 requires a flow. This pressure drop at the hydraulic pump output is detected by the control device, in particular an external pressure control circuit, so that an equivalent speed is provided in order to keep the pressure constant. As soon as the flow is below the minimum hydraulic pump outlet, the pressure at the hydraulic pump outlet begins to rise and the swashplate swings back again. Meanwhile, the pressure control circuit sets a minimum speed because the required pressure is below the actual pressure.

To prevent the two control loops from competing, the control point of the pressure control loop must be below the minimum setting point of the swashplate. In other words, the control point specification of the pressure control circuit is below the setting point of the swash plate. For example, the swash plate begins to swing in at a system pressure of approx. 200 bar until the system pressure rises to 210 bar. At this pressure the swash plate is almost fully swiveled in. This is ensured via a cylinder and a spring that are mechanically connected to the swash plate.

Specifically, the control pressure is selected at 195 bar, for example. If the flow of the hydraulic pump 10 exceeds the flow of the hydraulic consumer 50, the pressure increases at a measuring point of the pressure control circuit and also at an adjusting mechanism of the swash plate. The pressure control circuit detects an actual value that is above its target value, so that the minimum speed is provided. This remains until the flow of the hydraulic consumer 50 is higher than the maximum flow at minimum speed. In other words, as long as the flow of the hydraulic consumer 50 is below the hydraulic pump outlet, equivalent to the minimum speed, the motor 20 rotates at a constant speed and the hydraulic pump swash plate compensates for the changes in flow.

A fully swiveled swivel disk is understood to mean a relative swivel of 0%, with the swivel disk in this state operating in a speed range that is critical for the service life of the hydraulic pump 10 or the motor 20.

A fully swiveled swivel disk is understood to mean a relative swivel of 100%, with the swivel disk in this state having a negative effect on the efficiency of the hydraulic pump 10. In general, the further the swashplate is swiveled in, the more the efficiency of the hydraulic pump 10 decreases.

The swivel disk according to the invention is almost fully swiveled in and preferably has a relative swivel of 92%, with the motor 20 having a speed between preferably 1000 rpm and 2500 rpm to provide a very low volume flow and the motor 20 to provide a very high volume flow has a speed of preferably 10,000 rpm. When providing a very high volume flow, the system pressure corresponds to 210 bar.

In comparison to the invention, in the prior art an engine speed of 8000 rpm is required to provide a very low volume flow, so that this high engine speed leads to a shortened service life of the hydraulic pump or the motor and an increased noise level.

The combination according to the invention of the variable adjustment of the engine speed and the hydraulic pump eliminates exactly these problems. Furthermore, this makes constant pressure control possible for all control ranges. Furthermore, the control dynamics are significantly improved and pressure peaks are prevented.

Reference symbol list

10

hydraulic pump

10a

Hydraulic pump derivation

10z

Hydraulic pump supply line

20

engine

30

reservoir

40

Storage

50

Hydraulic supplier

Claims (10)

Hydraulic supply system for supplying hydraulic consumers (50) of an aircraft with a hydraulic fluid, comprising at least one hydraulic pump (10), at least one motor (20) and at least one accumulator (40), characterized in that for providing the hydraulic fluid with a variable volume flow or constant Pressure level, the speed of the motor (20) and the hydraulic pump (10) are variably adjustable. Hydraulic supply system Claim 1 , characterized in that the motor (20) can be operated at a minimum speed to provide a very low or no volume flow. Hydraulic supply system Claim 1 or 2 , characterized in that the motor (20) can be operated at a maximum speed to provide a very high volume flow. Hydraulic supply system according to one of the preceding claims, characterized in that the motor (20) comprises a control device for continuously variable change or constant maintenance of the motor speed. Hydraulic supply system according to one of the preceding claims, characterized in that the motor (20) comprises a cooling device with a hydraulic fluid as a cooling medium for cooling the motor (20). Hydraulic supply system according to one of the preceding claims, characterized in that the hydraulic pump (10) is designed with a swivel plate for its adjustment. Hydraulic supply system Claim 6 , characterized in that the swivel plate can be pivoted depending on or independently of the system pressure. Hydraulic supply system according to one of the preceding claims, characterized in that a reservoir (30) is provided which is connected to the connections of the hydraulic pump (10). Hydraulic supply system according to one of the preceding claims, characterized in that the accumulator (30) is designed as a piston accumulator, in particular as a spring accumulator. Aircraft, in particular aircraft, characterized in that the aircraft has at least one hydraulic supply system according to one of Claims 1 until 9 is executed.

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