Positive displacement pump with one rotor

Abstract

A positive displacement pump is proposed, comprising a housing (14), a rotor (20) arranged in the housing (14) and a drive shaft (24), wherein the drive shaft (24) has a pinion (28) with a toothing (30) which is positively coupled to a toothing (32) assigned to the rotor (20), and wherein the central axis (A) of the drive shaft (24) is arranged eccentrically to the central axis (R) of the rotor (20).

Description

[0001] The invention relates to a positive displacement pump with a housing and a rotor arranged in the housing.

[0002] Such positive displacement pumps are also called rotating positive displacement pumps. The rotor is mounted within the housing and is driven by a drive, typically an electric motor.

[0003] Positive displacement pumps are often used to pump liquid media, such as oil or cooling water.

[0004] During operation, the rotor of positive displacement pumps usually rotates at the same speed as the electric motor that drives it.

[0005] Flow requirements are constantly increasing, and with them the displacement volume of the positive displacement pumps used. However, the available installation space for the electric motor is not increasing.

[0006] This means that more power has to be converted by the electric motor in the same installation space, whereby the maximum available (drive) torque of an electric motor is limited.

[0007] Therefore, the speed would inevitably have to be increased to increase the mechanical performance of the electric motor. However, excessively high speed of the positive displacement pump has a negative impact on noise levels.

[0008] It is also advisable to operate the pump at a reduced speed in order to reduce friction losses during pump operation.

[0009] On the other hand, relatively high torques at lower speeds have a negative effect on the efficiency of the electric motor during operation.

[0010] This efficiency disadvantage increases with increasing media viscosity, since an ever higher torque of the electric motor is necessary to maintain a constant speed of the rotor.

[0011] The maximum available (drive) torque of the electric motor depends primarily on the materials used and the motor volume. Materials with particularly high strength and / or those that allow for a high power density of the electric motor, as well as a larger motor volume, lead to increased parts costs.

[0012] The limited maximum usable installation space also limits the maximum available (drive) torque of the electric motor. Furthermore, magnetic materials used to achieve a high power density in the electric motor often contain rare earth metals. These have a negative impact on the environmental balance and are subject to a high risk of raw material shortages.

[0013] Based on this, the object of the invention is to provide a positive displacement pump in which the electric motor used can be operated in a range that positively affects efficiency. Furthermore, media with particularly high viscosity should also be able to be pumped without requiring a larger electric motor. Furthermore, the positive displacement pump should still be simple in design and allow for reliable operation.

[0014] The stated object is achieved according to the invention by a positive displacement pump with a housing, a rotor arranged in the housing and a drive shaft, wherein the drive shaft has a pinion with a toothing which is positively coupled to a toothing assigned to the rotor, and wherein the central axis of the drive shaft is arranged eccentrically to the central axis of the rotor.

[0015] The basic idea of ​​the invention is to create a single-stage transmission between the drive shaft and the rotor of the positive displacement pump through the toothing of the pinion and the toothing of the rotor.

[0016] Only a single pinion is provided, the teeth of which engage with the teeth of the rotor and mesh with them when the drive shaft is driven.

[0017] The gear ratio allows the drive shaft to be driven at higher speeds than if it were coupled to the rotor without gear ratio.

[0018] The drive shaft is coupled to an electric motor, for example.

[0019] Due to the gear ratio, the required torque, which must be applied via the drive shaft of the electric motor, is lower.

[0020] Consequently, an electric motor coupled to the drive shaft can also be operated at a higher speed.

[0021] This allows high hydraulic lines to be provided by the positive displacement pump.

[0022] The gear ratio between the pinion and the rotor must be selected in such a way that the drive coupled to the drive shaft and the positive displacement pump itself are each operated with the highest possible efficiency.

[0023] This design still allows for simple torque transmission from the pinion to the rotor. Furthermore, the positive displacement pump is very compact despite the gear ratio between the pinion and rotor.

[0024] During operation of the positive displacement pump, there is no or only negligible relative movement between the center axis of the pinion or drive shaft and the center axis of the rotor.

[0025] One aspect provides that the rotor is fixed in its position in the radial direction by the pinion.

[0026] Consequently, the pinion allows for radial support of the rotor. This eliminates the need for additional radial bearings.

[0027] The term "fixed in position" means that there is no relative movement between the center axis of the drive shaft or pinion and the center axis of the rotor. The rotor can therefore continue to rotate.

[0028] In addition, the rotor can be supported in the radial direction by the housing and the pinion or by a toothed outer ring rotatably received in the housing, within which the rotor is arranged, and the pinion.

[0029] Consequently, the eccentricity of the central axis of the drive shaft relative to the central axis of the rotor is equal to the eccentricity of the central axis of the rotor relative to the central axis of the tooth outer ring.

[0030] Furthermore, at least one radial bearing may be provided, by which the rotor is mounted in the radial direction. Alternatively or additionally, an axial bearing may be provided, by which the rotor is mounted in the axial direction.

[0031] If a radial bearing is provided, this also allows the eccentricity of the center axis of the drive shaft relative to the center axis of the rotor to be designed in the opposite direction to the eccentricity of the center axis of the rotor relative to the center axis of the outer tooth ring.

[0032] In addition, an additional radial bearing means that the rotor does not necessarily have to be supported by the pinion and the housing or the outer tooth ring accommodated in the housing, so that any forces acting in the radial direction on the pinion are also reduced.

[0033] If an axial bearing is provided, the axial forces acting on the rotor can be absorbed and, if necessary, friction can be reduced, so that the efficiency of the displacement pump is further increased and wear is reduced at the same time.

[0034] If both types of bearings are provided, the advantages are combined accordingly.

[0035] The teeth of the pinion and the teeth of the rotor can each be straight-toothed.

[0036] This provides a particularly stable and robust gearing. Furthermore, no axial forces are generated that act on the rotor.

[0037] Alternatively, the teeth of the pinion and the teeth of the rotor can each be helically toothed.

[0038] This ensures particularly quiet operation of the displacement pump.

[0039] Furthermore, it is theoretically possible that the toothing of a helical pinion has only a single tooth.

[0040] Furthermore, the pinion may have fewer than 7 teeth, in particular 6 or 5 teeth.

[0041] Thus, even a straight-toothed pinion can have fewer than 7 teeth, in particular 6 or 5 teeth, if the toothing deviates accordingly from standard toothing.

[0042] This can be achieved by a low tooth tip height and a large tooth root form height.

[0043] If there is a corresponding deviation from standard toothing, the pinion can also have fewer than 7 teeth; if the tooth tip height is small and the tooth root height is large, versions with 5 teeth are possible.

[0044] This number of teeth has proven to be particularly advantageous.

[0045] Furthermore, the pinion can be made integrally with the drive shaft. This eliminates the need for additional assembly to attach the pinion to the drive shaft.

[0046] The drive shaft can be gearless, i.e. directly coupled to the motor shaft without any gear ratio.

[0047] The drive shaft is, for example, a motor shaft of an electric motor or is directly coupled to it.

[0048] Consequently, only a small number of components are required and production can be carried out particularly easily.

[0049] Furthermore, the drive shaft can be mounted at its free end in the housing. This allows radial forces acting on the drive shaft to be absorbed.

[0050] This allows the transmission of relatively large torques between the pinion and the rotor.

[0051] The toothing of the rotor can have at least one tooth more than the toothing of the pinion.

[0052] In extreme designs, the rotor teeth can have only one tooth more than the pinion.

[0053] However, a larger number of teeth is advantageous in order to increase the gear ratio.

[0054] Such a number of teeth has proven to be particularly advantageous.

[0055] Furthermore, the rotor's toothing can extend only over a portion of the rotor's entire width in the axial direction. This allows for simpler and faster production than if the second rotor toothing were created across the entire rotor width.

[0056] In addition, additional installation space is available within the rotor, which can be used for other purposes, for example for radial bearings of the rotor.

[0057] Alternatively, the rotor's teeth can extend across the entire width of the rotor. This provides a particularly stable toothing that is less susceptible to wear and allows for a more even power transmission from the pinion to the rotor.

[0058] Furthermore, the rotor's gearing can be made integral with the rotor. Consequently, no additional component with gearing that must be torsionally coupled to the rotor is required.

[0059] In addition, the positive displacement pump can comprise a plurality of rotors arranged along the drive shaft and each having an associated toothing via which the rotors are positively coupled to the drive shaft.

[0060] It would also be possible for all axially arranged rotors to be driven with the same gearing on the shaft, provided that the shaft is designed to be sufficiently long.

[0061] Alternatively, the positive displacement pump may comprise a plurality of rotors arranged along the drive shaft, some of which have associated gearing and some of which are rotationally fixedly coupled to the drive shaft.

[0062] This allows the rotors to be operated at different speeds.

[0063] In addition, a radial bearing of the shaft can be realized in this way.

[0064] The positive displacement pump can be a gerotor pump or a vane pump.

[0065] In this type of pump, the gear ratio between pinion and rotor according to the invention has a particularly beneficial effect on efficiency.

[0066] It is also conceivable that the positive displacement pump is a rotary vane pump or a gear pump.

[0067] The invention is described below with reference to an embodiment illustrated in the accompanying drawings, in which: - Fig. 1 a front view of a positive displacement pump according to the invention; - Fig. 2 a sectional view of the positive displacement pump according to the invention according to a first variant; - Fig. 3 a sectional view of the positive displacement pump according to the invention according to a second variant; - Fig. 4 an exploded view of the positive displacement pump according to the invention; - Fig. 5 the displacement pump according to the invention Fig. 1 in a sectional view along the plane VV in Fig. 1; - Fig. 6 the positive displacement pump according to the invention Fig. 2 in a sectional view along the plane IV-IV in Fig. 2; and - Fig. 7 the positive displacement pump according to the invention Fig. 2 in a sectional view along the plane IV-IV in Fig. 2 according to an alternative.

[0068] In the Fig. 1 to 7, a positive displacement pump 10 in the form of a gerotor pump 12 is shown. However, the following explanations can generally be applied to any type of positive displacement pump, for example, vane pumps.

[0069] The positive displacement pump 10, designed as a gerotor pump 12, comprises a housing 14 with a central axis G.

[0070] The housing 14 is formed from a housing ring 16 and two housing covers 18. The housing covers 18 are each arranged on the end face of the housing ring 16 (see the Fig. 5 to 7).

[0071] A rotor 20 is arranged within the housing 14, as well as a toothed outer ring 22 surrounding the rotor 20, which is rotatable relative to the housing 14 (see Fig. 2 and Fig. 3).

[0072] The tooth outer ring has a central axis Z which lies in the central axis G of the housing 14.

[0073] However, it is also conceivable that the central axis Z of the tooth outer ring 22 does not lie in the central axis G of the housing 14.

[0074] For other types of positive displacement pumps, the outer tooth ring 22 could be omitted accordingly.

[0075] In addition, the positive displacement pump 10 comprises a drive shaft 24 with a central axis A. The central axis A of the drive shaft 24 is arranged eccentrically to the central axis R of the rotor 20 (see in particular Fig. 2, Fig. 3, Fig. 6 and Fig. 7).

[0076] The drive shaft 24 is directly coupled to an electric motor 26 at the end opposite the housing 14, so that the drive shaft 24 simultaneously corresponds to the motor shaft of the electric motor 26 (see the Fig. 5 to 7).

[0077] Alternatively, the drive shaft can also be coupled directly and without a gear to the motor shaft of the electric motor 26.

[0078] In addition, the drive shaft 24 has a pinion 28 with a toothing 30 (see the Fig. 2 and Fig. 3).

[0079] The pinion 28 is formed integrally with the drive shaft 24.

[0080] Alternatively, the pinion 28 can also form a separate component and be arranged on the drive shaft 24 in a rotationally fixed manner by means of a form and / or frictional engagement.

[0081] The free end of the drive shaft 24 arranged within the housing 14 ends with the pinion 28.

[0082] Alternatively, however, it is also possible for the free end of the drive shaft 24 to be mounted in the housing 14 or in the housing cover 18.

[0083] Furthermore, a toothing 32 is provided, which is associated with the rotor 20. Consequently, the rotor 20 has a ring gear section 34 formed by the toothing 32.

[0084] The toothing 32 of the rotor 20 is designed as one piece with the rotor 20, so that the ring gear section 34 does not form a separate component.

[0085] Alternatively, however, it is also possible for the ring gear section 34 together with the toothing 32 to be formed separately from the rotor 20.

[0086] The toothing 30 of the pinion 28 engages with the toothing 32 of the rotor 20.

[0087] Consequently, the drive shaft 24 is positively coupled to the rotor 20 via the toothing 30 of the pinion 28 and via its toothing 32.

[0088] The gears 30, 32 are each helical.

[0089] Alternatively, the gears 30, 32 can also be straight-toothed.

[0090] The toothing 30 of the pinion 28 can have fewer than 7 teeth, while the toothing 32 of the rotor 20 has at least one tooth more than the pinion teeth.

[0091] It is possible that the pinion has 5 teeth.

[0092] The toothing 32 of the rotor 20 extends in the axial direction only over a part of the width B of each rotor (see in particular Fig. 5 to 7).

[0093] Alternatively, however, it is also conceivable that the toothing 32 is provided over the entire width B of the rotor.

[0094] According to a first variant, the rotor 20 is mounted in the radial direction by the toothed outer ring 22 rotatably received in the housing 14 and by the pinion 28 in the radial direction.

[0095] This is done by the rotor contacting the toothed outer ring 22 in a radially outward direction, so that a movement of the rotor 20 radially outward is prevented, while a movement radially inward is blocked by the pinion 28 of the drive shaft 24 (see Fig. 2).

[0096] The eccentricity of the central axis A of the drive shaft 24 relative to the central axis R of the rotor 20 is the same as the eccentricity of the central axis R of the rotor 20 relative to the central axis Z of the tooth outer ring or relative to the central axis G of the housing 14.

[0097] Consequently, the rotor 20 is supported in the axial direction solely by the pinion 28 and the toothed outer ring 22.

[0098] Alternatively, there may also be an opposite eccentricity, as described in Fig. This is the case in the second variant shown in Figure 3. In this variant, the rotor 20 is accordingly not supported in the radial direction by the pinion 28 or the housing 14 or the outer toothed ring 22.

[0099] In addition, the rotor 20 can be designed according to an alternative described in Fig. 6, are additionally supported in the radial direction by one or more radial bearings 36.

[0100] For example, the rotor 20 may have a bearing shoulder 38 projecting in the axial direction, by means of which the rotor 20 is mounted in a receptacle 40 within the housing 14.

[0101] Alternatively or additionally, a bearing pin 42 may also be provided, which extends from the housing cover 18 into a cylindrical bearing receptacle 44 within the rotor 20.

[0102] The radial bearings 36 are designed as plain bearings. However, it is also possible that the radial bearings 36 are roller bearings.

[0103] Additionally or alternatively, the rotor 20 can also be supported in the axial direction by axial bearings 46, which are formed by the contact of the end faces of the rotor 20 to the housing 14 or to its housing ring 16 and / or its housing cover 18.

[0104] Accordingly, the axial bearings 46 are also designed as plain bearings.

[0105] Alternatively, it is also conceivable that the axial bearing 46 is a rolling bearing.

Claims

[1] Positive displacement pump with a housing (14), a rotor (20) arranged in the housing (14) and a drive shaft (24), wherein the drive shaft (24) has a pinion (28) with a toothing (30) which is positively coupled to a toothing (32) assigned to the rotor (20), and wherein the central axis (A) of the drive shaft (24) is arranged eccentrically to the central axis (R) of the rotor (20). [2] Positive displacement pump according to claim 1, characterized by that the rotor (20) is fixed in its position in the radial direction by the pinion (28). [3] Positive displacement pump according to claim 1 or 2, characterized by that the rotor (20) is mounted in the radial direction by the housing (14) and the pinion (28) or by a toothed outer ring (22) rotatably received in the housing (14), within which the rotor (20) and the pinion (28) are arranged. [4] Positive displacement pump according to one of the preceding claims, characterized bythat at least one radial bearing (36) is provided, by which the rotor (20) is mounted in the radial direction, and / or that at least one axial bearing (46) is provided, by which the rotor (20) is mounted in the axial direction. [5] Positive displacement pump according to one of the preceding claims, characterized by that the teeth (30) of the pinion (28) and the teeth (32) of the rotor (20) are each straight-toothed. [6] Positive displacement pump according to one of claims 1 to 4, characterized by that the teeth (30) of the pinion (28) and the teeth (32) of the rotor (20) are each helical. [7] Positive displacement pump according to one of the preceding claims, characterized by that the pinion (28) has less than 7 teeth, in particular 6 or 5 teeth. [8] Positive displacement pump according to one of the preceding claims, characterized by that the pinion (28) is made in one piece with the drive shaft (24). [9] Positive displacement pump according to one of the preceding claims, characterized by that the drive shaft (24) is coupled to the motor shaft without a gear. [10] Positive displacement pump according to one of the preceding claims, characterized by that the drive shaft (24) is mounted at its free end in the housing (14). [11] Positive displacement pump according to one of the preceding claims, characterized by that the toothing (32) of the rotor (20) has at least one tooth more than the toothing (30) of the pinion (28). [12] Positive displacement pump according to one of the preceding claims, characterized by that the toothing (32) of the rotor extends only over a part of the total width (B) of the rotor (20) in the axial direction. [13] Positive displacement pump according to one of claims 1 to 11, characterized by that the toothing (32) of the rotor (20) extends over the entire width (B) of the rotor (20). [14] Positive displacement pump according to one of the preceding claims, characterized bythat the toothing (32) of the rotor (20) is made in one piece with the rotor (20). [15] Positive displacement pump according to one of the preceding claims, characterized by that the positive displacement pump (10) comprises a plurality of rotors (20) which are arranged along the drive shaft (24) and each have an associated toothing (32) via which the rotors (20) are positively coupled to the drive shaft (24). [16] Positive displacement pump according to one of the preceding claims, characterized in that the positive displacement pump (10) is a gerotor pump (12) or a vane pump.

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