Gear Pump

Abstract

The present invention relates to a gear pump (10) with at least three gear wheels (12, 14, 16), which are arranged in a pump housing (18), and a drive shaft (20). With such a device, in which the at least three gear wheels (12, 14, 16) are arranged radially adjacent to one another, and wherein a pump is formed by in each case two adjacent ones of the at least three gear wheels (12, 14, 16) and wherein one of the at least three gear wheels (12, 14, 16) can be driven by the drive shaft (20), a multiple pump is described which is more compact in construction than the known prior art and has a greater level of efficiency. Furthermore, considerable potential savings in system costs result from this.

Claims

1.-13. (canceled)

14. A gear pump comprising: at least three gear wheels arranged in a pump housing and a drive shaft; the at least three gear wheels arranged radially adjacent to one another; a pump is formed by two adjacent ones of the at least three gear wheels and one of the at least three gear wheels can be driven by the drive shaft.

15. The gear pump according to claim 14, wherein each pump comprises a suction side and a pressure side.

16. The gear pump according to claim 14, wherein at least two of the at least three gear wheels have an equal number or a different number of teeth.

17. The gear pump according to claim 14, wherein the drive shaft is driven by a drive motor arranged in a motor housing.

18. The gear pump according to claim 17, wherein the drive motor is an electric motor.

19. The gear pump according to claim 18, wherein the electric motor includes of a stator arranged in the motor housing and a rotor arranged in a motor chamber, the rotor connected to the drive shaft.

20. The gear pump according to claim 19, wherein a side plate fluidically seals the suction sides and the pressure sides of each pump from the motor chamber.

21. The gear pump according to claim 20, wherein at least one of the pumps is associated with at least one valve arranged on the side plate, and a fluid conveyed by the pump is directed into the motor chamber.

22. The gear pump according to claim 17, wherein the drive shaft is formed as a hollow shaft and includes a radial throttle opening to the motor chamber.

23. The gear pump according to claim 17, wherein an end plate is arranged on the side of the pump housing that is facing away from the motor housing.

24. The gear pump according to claim 23, wherein the end plate provides vibration damping and/or sealing.

25. The gear pump according to claim 23, wherein the end plate has at least two suction ports for connecting the suction sides of the pumps and at least two pressure ports for connecting the pressure sides of the pumps.

26. The gear pump according to claim 23, wherein the end plate comprises a servo pressure port for providing servo pressure fed from the motor chamber.

Description

DRAWINGS

[0030] The present invention is explained in detail hereinafter with the aid of its drawing. In the drawing:

[0031] FIG. 1 shows a schematic view of a gear pump in accordance with the invention;

[0032] FIG. 2 shows an end plate-side view of a gear pump in accordance with the invention designed as a double pump;

[0033] FIG. 3 shows an end plate-side view of a gear pump in accordance with the invention designed as a triple pump; and

[0034] FIG. 4 shows a cross-sectional view of a gear pump in accordance with the invention designed as a double pump.

DETAILED DESCRIPTION

[0035] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0036] FIG. 1 shows a schematic cross-sectional view of a gear pump 10 in accordance with the invention. This contains three gear wheels 12, 14, 16 which respectively mesh with each other in twos. In the illustrated embodiment, the centrally arranged gear wheel 12 is directly connected both to the gear wheel 14 and also to the gear wheel 16. All three gear wheels are arranged inside a pump housing 18, in which they are also mounted. The centrally arranged gear wheel 12 is driven and caused to rotate via a drive shaft 20, to which it is connected in a power-transmittable manner. The remaining two gear wheels 14, 16 do not have their own drive. They are caused to rotate in that, by reason of their meshing with the gear wheel 12, they are entrained thereby.

[0037] 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.

[0038] 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.

[0039] 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 FIG. 1, in order to prevent overheating of the electric motor 24, in particular of the rotor 28 and further components such as an ECU arranged in the motor chamber, cooling liquid is fed into the motor chamber 30 in a controlled manner. For this purpose, the side plate 32 is provided with bores both in the region of a pressure side of the pump formed by the gear wheels 12, 14 and also in the region of a pressure side of the pump formed by the gear wheels 12, 16. Valves 34 are provided on the side of these bores in the side plate 32 facing the motor chamber 30. In addition to the cooling of the electric motor 24, this arrangement has the advantage that operation-imposed pressure peaks in the operation of the pumps can be damped because the valves 34 are provided in such a way that they open in the presence of a certain pressure. The physical loading on the components downstream of the gear pump 10 in the cooling liquid circuit can thus be reduced.

[0040] 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 FIG. 1. Furthermore, it comprises a throttle opening 36 to the motor chamber 30, through which cooling liquid from the motor chamber 30 can enter the hollow shaft. The cooling liquid exits the hollow shaft to a suction-side cooling liquid port which is provided e.g. outside the gear pump 10.

[0041] 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 FIGS. 2 and 3.

[0042] FIG. 2 shows an end plate-side view of a gear pump 10 in accordance with the invention. The indicated illustration of the gear wheels 12, 14, 16 shows that the depicted gear pump is a double pump. The centrally arranged gear wheel 12 is driven in the clockwise direction by the drive shaft 20, not illustrated. The two gear wheels 14, 16 meshing with the gear wheel 12 accordingly rotate in the anti-clockwise direction. This means that the suction port 40 of the pump formed by the gear wheels 12, 14 is on the left side in FIG. 2, and the associated pressure port 42 is opposite it on the right side. For the pump formed by the gear wheels 12, 16, the ports are accordingly arranged in a mirror-inverted manner, thus the suction port 40 is located on the left and the pressure port 42 on the right [sic]. In addition, the end plate 38 also comprises a servo pressure port 44. This is directly connected to the motor chamber 30, now shown, and serves e.g. for hydraulic actuation of further valves of the cooling liquid circuit.

[0043] Analogously to FIG. 2, FIG. 3 shows an end plate-side view of a gear pump 10 in accordance with the invention, which is formed as a triple pump. One of the gear wheels 14 driven by the gear wheel 12, which is driven by the drive shaft 20, drives a further gear wheel 16. A particular feature of this arrangement is that neither of the two gear wheels 14, 16 which jointly form a pump is itself driven via a drive shaft. Instead of this, the gear wheel 14 is entrained by the gear wheel 12 and the gear wheel 16 is entrained by the gear wheel 14. The direction of rotation of gear wheel 16 therefore corresponds to that of gear wheel 12 which, in the illustrated example, is driven in the anti-clockwise direction. In terms of the position of the suction port 40 and of the pressure port 42 of the pump formed by the upper gear wheels 14, 16, this means that this position is the same as the position of the suction port 40 and of the pressure port 42 of the pump formed by the lower gear wheels 12, 14. The gear pump 10 according to FIG. 3 also contains a servo pressure port 44.

[0044] FIGS. 2 and 3 also show that the gear wheels 12, 14, 16 can be of different sizes and therefore have different numbers of teeth from each other. Smaller gear wheels are easier to produce and have a smaller inert mass, which has a positive effect on efficiency, in particular in the case of varying rotational speeds. In contrast, larger gear wheels require a lower rotational speed in order to achieve the same delivery quantity, whereby friction losses can be reduced. Suitable gear wheels should therefore always be selected taking account of individual usage conditions.

[0045] FIG. 4 shows a schematic motor-side view of a side plate 32. This shows, in particular, the valves 34 which make possible a connection to the motor chamber 30 and, in the present example, are formed as tongue valves. Both the pump formed from the gear wheels 12, 14 and also the pump formed from the gear wheels 12, 16 are associated with a respective tongue valve. These are subjected on the one hand to the pump pressure and on the other hand to the pressure prevailing in the motor chamber 30. The tongue valves are preferably selected because they open only once a preset minimum pressure difference is reached. In this way, it is possible to prevent deficient supply to the components in the cooling liquid circuit through quasi-permanently open valves, and instead of this it is possible to ensure that the valves 34 open in particular in order to damp pressure peaks. This reduces the loading on the components downstream in the cooling liquid circuit. Furthermore, the side plate 32 comprises an opening for the servo pressure port 44. On the side of the side plate 32 facing the pump housing 18, this opening is adjoined by a duct which is directly connected to the above-described servo pressure port 44 of the end plate 38. The servo pressure port 44 of the end plate 38 is accordingly directly subjected to the pressure present in the motor chamber 30, which pressure is sufficient to hydraulically actuate further valves in the cooling liquid circuit.

[0046] 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.