Patent Application
20240254988
This application claims the benefit and priority of German Application No. 10 2023 102 039.0, filed Jan. 27, 2023. The entire disclosure of the above application is incorporated herein by reference.
The present invention relates to a gear pump with at least three gear wheels, which are arranged in a pump housing, and a drive shaft, wherein the at least three gear wheels are arranged radially adjacent to one another, and wherein a pump is formed by two adjacent ones of the at least three gear wheels in each case and wherein one of the at least three gear wheels can be driven by the drive shaft.
In vehicles driven by an internal combustion engine, the extent of temperature control was essentially limited to the cooling of the internal combustion engine and of the transmission. In the most complex case, this could be achieved with two separate cooling circuits, with respective dedicated coolant pumps. In hybrid electric vehicles (HEVs) and battery electric vehicles (BEVs), the extent of temperature control is considerably greater than in the former case. By reason of the comparatively distinctly lower heat losses of the drive train, it may be necessary, particularly in winter, to heat the battery module because the battery module must operate within the optimal temperature window in order to ensure a maximum range for the vehicle. However, at the same time, cooling of the electric motor is necessary, in particular during lengthy operation. Furthermore, the complexity of the temperature-control arrangement is increased in that many of the additionally provided control devices must also be cooled.
For this purpose, modern motor vehicles have a thermo-management system. In particular, this regulates the supply of cooling liquid in the required temperature range to the components requiring temperature control. Within the scope of the present document, for the sake of better readability, the term “cooling liquid” is also used for the liquid which heats components such as the battery module.
There is usually one cooling liquid circuit in each case per temperature level of the cooling liquid. This already means a doubling of all components, in particular also of the pumps and of the heating/cooling elements. If the volume stream requirement for cooling liquid through a plurality of systems to be cooled is very large, or if the physical distance between two different components which require the same temperature level is large, a plurality of cooling circuits of the same temperature level can also be used. This leads to an even greater number of components, which on the one hand leads to higher costs and on the other hand takes up precious installation space.
At present, centrifugal pumps are commonly used as cooling liquid pumps in HEVs and BEVs. These are designed in such a way that in extreme situations they are suitable for quickly providing the required temperature level. The cooling liquid pump allocated to battery temperature control runs e.g. under full load when the temperature of the battery module must be controlled within its optimal operating window in winter under hard freezing conditions. However, this means that the cooling liquid pumps are operated in the partial-load operational range for the majority of their service life. Even in the above-mentioned example, the pump is controlled back into the partial-load operational range after initial heating of the battery module, since the requirement for cooling liquid to maintain the temperature is lower than for heating.
However, there are a number of disadvantages with centrifugal pumps: in the dominant partial-load operational range they have a comparatively poor level of efficiency. Their energy requirement thereby increases, which has a negative effect both on the real range as well as on the range and therefore the rating in the cycle of the Worldwide harmonized Light vehicles Test Procedure. In addition, the construction of centrifugal pumps makes them prone to cavitation. In order to avoid damage caused thereby, they require a preferably long straight intake as a calming path. This conflicts with the ever more stringent requirements for installation space. In addition, their decoupling in terms of vibration technology proves to be demanding, since a rubber damper element located in the fastening plane affects the sealing gap of the pump. A combination of a plurality of pumps into a module which has a common drive represents a high level of outlay in terms of cost and technical complexity, for which reason such a design has not been produced thus far.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
Therefore, the object of the present invention is to describe a multiple pump with a common drive, the system costs of which are reduced in comparison to existing devices and which takes up less installation space. Furthermore, the multiple pump is to contain pumps which have a considerably improved level of efficiency compared with the prior art.
Such a pump is the subject of independent claim 1. Advantageous developments are provided in the dependent claims.
The device in accordance with the invention is a gear pump with at least three gear wheels which are arranged in a common pump housing. The device further comprises a drive shaft, by means of which one of the at least gear wheels is driven. These are arranged radially with respect to each other, preferably in a common plane, in such a way that the teeth of two respectively adjacent gear wheels mesh with one another and in this way form a pump. Therefore, in the simplest embodiment of the gear pump in accordance with the invention, its three gear wheels form two pumps which are able to deliver two separate fluid streams. This is achieved in that one of the gear wheels meshes with the two other gear wheels and in so doing forms a pump in each case. In arrangements with four gear wheels, this is true of both gear wheels which each mesh with two other gear wheels. As a whole, three pumps are thus formed. Generally speaking, the number of pumps is thus always one lower than the number of gear wheels.
An arrangement of this type renders possible considerable advantages in terms of installation space over the known prior art. A more compact construction can be achieved just by reducing the components. In addition, gear pumps are less prone to cavitation compared with centrifugal pumps. Therefore, they do not require a calming path in the intake but rather can also be used in an axially limited installation space. The fact that the different pumps of the gear pump acting as a multiple pump are not arranged axially one behind the other but radially with respect to each other is also favorable to such an arrangement.
The use of a gear pump which, depending on use, is operated predominantly in the partial-load operational range increases the range of the HEV or BEV both in the WLTP and also in actual operation on the road. For the manufacturer of such a vehicle an advantage can therefore be achieved in advertising and possibly in the tax benefit of its products, for the end customer, convenience is increased owing to extended usage times.
Furthermore, the lower number of components brings technical and economic advantages. On the one hand, system costs are reduced owing to the lower number of components, on the other hand there are fewer components which can potentially be defective. As a whole, this leads to greater reliability in the gear pump in accordance with the invention, while at the same time reducing costs.
According to one advantageous embodiment, each pump comprises a suction side and a pressure side. The manner of construction means that these are always arranged in such a manner that the suction side and the pressure side of adjacent pumps alternate. For example, if, in a first pump the suction side is on the left, when viewed axially, and the pressure side in the same view is on the right, then in an adjacent pump, owing to the opposing direction of rotation of the neighboring gear wheel, the suction side is arranged on the right and the pressure side on the left.
The manner of construction means that, in gear pumps, the volume flow delivered can be regulated exclusively by means of the rotational speed. The fluid delivered per rotation of a gear wheel depends on the number of teeth and the delivery volume per tooth pair. In the gear pump in accordance with the invention, the rotational speeds of the different pumps cannot be regulated independently of each other. The rotational speeds of all further gear wheels inevitably result from the rotational speed of the drive shaft and therefore of the driven gear wheel. According to one embodiment of the gear pump, only gear wheels of the same size, i.e. the same diameter and the same number of teeth, are used when all pumps of the gear pump are to deliver the same volume flow. In contrast, if it is desired to provide volume flows of different extents, then gear wheels of different size, i.e. with tooth numbers which differ from each other, can be used in part or entirely, which is the subject of a further embodiment.
In addition to the desired volume flows, efficiency may also be a factor in the dimensioning of the gear wheels. Larger gear wheels can be operated at lower rotational speeds, whereby friction losses can be reduced. However, at the same time, they are heavier and therefore also have a greater inert mass and are potentially more expensive to produce owing to the greater use of material. Therefore, the selection and dimensioning of the gear wheels should always be effected in a manner tailored to the individual case and taking into account all influencing factors.
According to a preferred embodiment, in order to drive a gear wheel by means of the drive shaft this shaft is driven by a drive motor. This can be arranged in a motor housing which is connected to the pump housing e.g. via a flange connection, or is even fastened on the vehicle side.
According to a preferred embodiment, an electric motor is used as the drive motor. This is compact, has a high level of efficiency and is, in particular, able to provide the required torque even at low rotational speeds.
According to a further preferred embodiment, a stator of the electric motor is arranged in the motor housing. Radially inwards thereof, a motor chamber is further formed through the motor housing, a rotor of the electric motor being arranged in this motor chamber. The rotor is connected to the drive shaft of the gear pump and therefore drives it.
In accordance with a preferred embodiment, in order to prevent uncontrolled entry of cooling liquid into the motor chamber a side plate is arranged between the pump housing and motor housing. This seals the pump chamber, through which fluid flows, off from the motor chamber on both the suction side and also the pressure side.
In particular, during lengthy operation of the gear pump, the rotor of the electric motor can require cooling. For this reason, according to a preferred embodiment, at least one of the pumps is associated with a valve which is arranged on the side plate. This valve makes it possible to introduce cooling liquid, delivered by means of the pump, into the motor chamber. If the pumps deliver cooling liquid with the same temperature level the provision of a respective valve per pump is appropriate. In such a way, it is possible to ensure that the cooling liquid under the highest pressure is always fed into the motor chamber. This increases the cooling performance for cooling the electric motor.
At the same time, the motor chamber functions as a pulsation damper. Pressure peaks which arise through the operation of the pump or pumps effect opening of the valves to the motor chamber. Therefore, these pressure peaks are not introduced into the cooling system disposed downstream of the gear pump, whereby the components thereof are exposed to lower loading. The pressure peaks can be damped very effectively through the volume of the motor chamber, for which reason no negative multiple loads act on the components arranged in the motor chamber.
In order to ensure continuous cooling of the electric motor, the cooling liquid located in the motor chamber should be discharged. For this purpose, according to a preferred embodiment, the drive shaft is formed as a hollow shaft. The cooling liquid from the motor chamber can enter the hollow shaft via a radial throttle opening. It is thereby associated with a non-pressurized portion of the cooling liquid circuit. This can be e.g. the suction side of one of the pumps or a common cooling liquid reservoir which is arranged outside the gear pump.
According to a preferred embodiment, an end plate is arranged on the side of the pump housing facing away from the motor housing and the side plate. This end plate serves to connect the gear pump to the vehicle.
The end plate is preferably produced from a vibration-damping material. In this way, the gear pump can be decoupled in terms of vibration technology from the rest of the vehicle, whereby noises which are irritating to the vehicle occupants can be avoided. Alternatively or additionally, the end plate can also serve to seal the gear pump because it prevents egress of cooling liquid on the side of the pump housing facing away from the motor housing.
In order to achieve a particularly compact design for the gear pump, the end plate according to a preferred embodiment comprises at least two suction ports for connecting the suction sides and at least two pressure ports for connecting the pressure sides of the pumps. This makes possible a particularly space-saving integration of the gear pump into e.g. a power train space of a vehicle, since, after it is installed, the gear pump must remain accessible only from one side in order to connect the corresponding hoses for the cooling liquid circuits.
In addition to the above-mentioned openings for connecting the suction sides and the pressure sides of the pumps, the end plate can, according to a preferred embodiment, comprise a further connection to provide a servo pressure. This can be used e.g. to hydraulically actuate valves of the cooling liquid circuit which are arranged outside the gear pump. For this purpose, the servo pressure connection is connected to the motor chamber of the gear pump and is continuously acted upon from there. In addition to the advantage that it is possible to dispense with a further hydraulic pump in order to actuate external valves, this also increases the coolant volume flow through the motor chamber. This improves the cooling performance for the electric motor and can thereby have a positive effect on its service life.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The present invention is explained in detail hereinafter with the aid of its drawing. In the drawing:
Example embodiments will now be described more fully with reference to the accompanying drawings.
The drive shaft 20, via which the centrally arranged gear wheel 12 is mounted in the pump housing 18, extends into a motor chamber 30 formed by a motor housing 22. At that location, it is connected to the rotor 28 of an electric motor 24 in a power-transmittable manner. The associated stator 26 of the electric motor 24 is arranged in the motor housing 22, radially outside the motor chamber 30 and fluidically sealed with respect thereto.
Between the pump housing 18 and the motor housing 22 a side plate is provided which prevents uncontrolled ingress of cooling liquid from the space within the pump housing 18, in which the gear wheels 12, 14, 16 are arranged, into the motor chamber 30. In order to counteract the egress of cooling liquid from the gear pump 10, seals are provided in a radially outer contact region between the side plate 32 and the pump housing 18 and the motor housing 22 respectively.
In particular, during lengthy operation of the gear pump 10, operation-imposed friction arises in the moving components and there is a corresponding development of heat as a result thereof. This is non-critical for the gear wheels 12, 14, 16 since these are permanently in contact with cooling liquid and are cooled thereby. According to the embodiment shown in
The cooling of the electric motor 24 by cooling liquid delivered by the pumps can be take place effectively only if this cooling liquid is not fed into the motor chamber 30 just once but is continuously renewed. In order to discharge cooling liquid from the motor chamber 30, the drive shaft 20 is formed as a hollow shaft in accordance with the embodiment shown in
An end plate 38 is provided on the side of the pump housing 18 facing away from the motor housing 22. This end plate serves to connect the gear pump 10 to a vehicle-side structure. For this purpose, the end plate 38 preferably has vibration-damping properties, e.g. it is produced from a vibration-damping material. This makes it possible to decouple the gear pump 10 from the vehicle in terms of vibration-technology and thereby increases the comfort of the occupants of the vehicle concerned. Furthermore, the end plate 38 serves to connect the hoses of the cooling liquid system, more detailed discussion of this being given in light of
Analogously to
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2023 102 039.0 | Jan 2023 | DE | national |
