Hydraulic pump and method for controlling axial forces of hydraulic pump

Description

Background of the invention

[0001] The invention relates to a hydraulic pump and particularly to controlling axial forces of the hydraulic pump. Document GB 2 048 384 A discloses a hydraulic pump having a gear motor and an impeller on the same axis.

[0002] Axial forces are created in hydraulic pumps, and their management typically requires axial thrust bearings and / or arrangements for compensating the axial forces.Brief description of the invention

[0003] The object of the invention is thus to develop a novel type of a hydraulic pump and a method for controlling the axial forces of the hydraulic pump. The arrangement according to the invention is characterised by what is disclosed in the independent claims. Some embodiments of the invention are disclosed in the dependent claims.

[0004] In the solution presented, the hydraulic pump includes a hydraulic motor and an impeller. The impeller produces a first axial force into a first axial direction. The hydraulic motor is of the gear type including gears with helical teeth. A gear with helical teeth produces a second axial force into a direction opposite in relation to the first axial direction. Furthermore, in the presented solution, the gear with helical teeth in question is arranged into connection with the impeller such that the second axial force produced by the gear with helical teeth is utilized to compensate the first axial force. In this way, axial forces may be controlled and compensated in a simple manner. Additionally, e.g. bearings may be lightened and, according to an embodiment, the impeller may be arranged into connection with the gear with helical teeth even without an axial thrust bearing. All in all, a hydraulic pump is provided with a simple, compact and cost-effective solution.

[0005] According to an embodiment, the gear with helical teeth and the impeller are made up of their construction such that the first axial force and the second axial force compensate each other. This type of solution is particularly simple and reliable.

[0006] According to an embodiment, the hydraulic pump further comprises a hydrostatic compensation arrangement which is configured to produce a third axial force for the axle of the gear with helical teeth into the first axial direction. With such an arrangement, axial forces may be further controlled in an extremely versatile and reliable way.

[0007] According to an embodiment, the hydrostatic compensation arrangement comprises regulating means for regulating the magnitude of the third axial force. In this way, axial forces may be controlled and compensated in an accurate and versatile manner.

[0008] According to an embodiment, the hydrostatic compensation arrangement comprises means for limiting the maximum magnitude of axial force.Brief description of the drawings

[0009] The invention will now be described in closer detail in connection with some embodiments and with reference to the accompanying drawings, in which: Figure 1 is a schematic diagonal front view of a hydraulic pump; Figure 2 is a schematic side view of some important parts of the hydraulic pump of Figure 1 in cross section; Figure 3 is a schematic view of some important parts of the hydraulic pump and axial forces as illustrated; Figure 4 is a schematic view of a second embodiment in a way of Figure 3; and Figure 5 is a schematic view of a third embodiment in a way of Figures 3 and 4. Detailed description of the invention

[0010] Figure 1 shows a hydraulic pump 1. The hydraulic pump 1 in Figure 1 is a submersible pump of the centrifugal type.

[0011] Figure 2 particularly illustrates a hydraulic motor 2 and an impeller 3 of the parts of the hydraulic pump. For clarity, Figure 2 does not show all parts of the hydraulic pump 1, such as body parts and bearings. As illustrated in Figures 3, 4 and 5, the hydraulic motor 2 is a gear pump which comprises gears with helical teeth 4a, 4b or obliquely toothed wheels.

[0012] When rotating, the impeller 3 produces a first axial force Fi into a first axial direction. In a hydraulic pump according to prior art, due to this first axial force Fi, the impeller 3 is typically bearing-mounted stationary in the axial direction.

[0013] The gear pump comprises a driving gear with helical teeth 4a and a driven gear with helical teeth 4b. The driven gear with helical teeth 4b is arranged coaxially with the impeller 3.

[0014] The gear with helical teeth 4b of the hydraulic motor 2 produces a second axial force Ft into a direction opposite in relation to the first axial direction. In the presented solution, the impeller 3 is not bearing-mounted in the axial direction. Therefore, the first axial force Fi and the second axial force Ft produced by the gear with helical teeth 4b compensate each other.

[0015] According to an embodiment, the second axial force Ft produced by the gear with helical teeth 4b equals the fist axial force Fi produced by the impeller 3, that is, Ft = Fi. Then, the first axial force Fi and the second axial force Ft compensate each other and no other compensation arrangements are needed.

[0016] The magnitude of the second axial force Ft produced by the gear with helical teeth 4b is affected by e.g. the helix angle of the teeth. Typically, the motor manufacturer reports the maximum value of external axial force / axial load. From it, it is possible to derive the required need for compensation.

[0017] The impeller 3 is straight-bladed. Therefore, the axial force produced by the impeller arises from differences in pressure in the pump construction in the environment of the impeller 3. When the impeller rotates, there is a vacuum in the inlet of the pump construction and there is fluid pressure as for the chamber. The sum of the pressures gives the calculated force per given surface area. The magnitude of the first axial force Fi produced by the impeller 3 is affected by pressure and flow area. Therefore, it is possible to provide the axial force Fi produced by the impeller 3 as desired by changing the size of the flow area.

[0018] On the other hand, the axial force Fi produced by the impeller 3 is the greater, the greater the load of the pump and, similarly, the magnitude of the second axial force Ft produced by the gear of the gear pump is the greater, the greater the load of the pump. As the rotation speeds of the gear 4b and the impeller 3 increase, the load of the pump also increases because the water pressure and the hydraulic pressure rise. Correspondingly, when the rotation speeds decrease, the load of the pump also decreases as the pressures go down. Thus, when the impeller 3 and the gear 4b are coaxial and their rotation speeds follow each other, the forces will compensate each other in a quite wide range of use.

[0019] Such as stated above, there may not be necessary to provide any other compensation arrangements in addition to the first axial force Fi produced by the impeller 3 and the second axial force Ft produced by the gear with helical teeth 4b. However, Figure 3 shows a hydrostatic compensation arrangement 5 which is configured to produce a third axial force Fc for the axle of the gear with helical teeth 4b into the first axial direction. The hydrostatic compensation arrangement 5 comprises an actuator 6, into which, hydraulic fluid is fed along a hydraulic line 7 from a pressure source P.

[0020] The hydraulic pump according to prior-art has required this hydrostatic compensation arrangement 5 because the axial force Fc produced by it has typically compensated the axial force Ft produced by the gear with helical teeth 4b in its totality. If the hydrostatic compensation arrangement 5 is not needed, it can be thus omitted. On the other hand, if the hydrostatic compensation arrangement 5 is part of the motor supplier's standard product, there is necessarily no need for changing the standard product but it is enough that e.g. the hydraulic line 7 is plugged when the axial force Fc of the compensation arrangement 5 is not required.

[0021] When the hydraulic pump 1 comprises the hydrostatic compensation arrangement 5, the sum of the third axial force Fc produced by it and the first axial force Fi produced by the impeller 3 is set to equal the second axial force Ft produced by the gear with helical teeth 4b, that is, Ft = Fi + Fc.

[0022] In the embodiment of Figure 4, the magnitude of the third axial force Fc is regulated by letting pressure fluid into a tank 8 as determined by an adjustable flow valve 9. The embodiment of Figure 5 is very much similar to that of Figure 4 but, in the embodiment of Figure 5, the maximum magnitude of the third axial force Fc is further limited by an adjustable valve 10 limiting the maximum pressure.

[0023] When the magnitude of the third axial force Fc can be regulated, it is thus possible to increase the magnitude of the third axial force Fc when the first axial force Fi produced by the impeller 3 is smaller and vice versa.

[0024] Even though the magnitude of the axial force Fc was not regulated as such, as shown in Figure 3, it is still possible to limit the maximum magnitude of the axial force Fc. Then, in the embodiment of Figure 3, the hydraulic line 7 can additionally be connected to the tank 8 by a valve limiting the maximum pressure.

[0025] The order of magnitude of the presented axial forces can be e.g. 5-20 kN.

[0026] Those skilled in the art will find it obvious that, as technology advances, the basic idea of the invention may be implemented in many different ways. The invention and its embodiments are thus not restricted to the examples described above but can vary within the scope of the claims.

Claims

1. A hydraulic pump, which includes a hydraulic motor (2) and an impeller (3), which impeller (3) produces a first axial force (Fi) into a first axial direction, characterized in that the hydraulic motor (2) is of the gear type including gears with helical teeth (4a, 4b), that the gear with helical teeth (4a, 4b) produces a second axial force (Ft) into a direction opposite in relation to the first axial direction, and that gear with helical teeth (4a, 4b) in question is arranged into connection with the impeller (3) such that the second axial force (Ft) in question produced by the gear with helical teeth (4a, 4b) is utilized to compensate the first axial force (Fi).

2. A hydraulic pump according to claim 1, wherein the impeller (3) is arranged into connection with the gear with helical teeth (4a, 4b) without an axial thrust bearing.

3. A hydraulic pump according to claim 1 or 2, wherein the gear with helical teeth (4a, 4b) and the impeller (3) are made up of their construction such that the first axial force (Fi) and the second axial force (Ft) compensate each other.

4. A hydraulic pump according to any one of the previous claims, which further comprises a hydrostatic compensation arrangement (5) which is configured to produce a third axial force (Fc) for the axle of the gear with helical teeth (4) into the first axial direction.

5. A hydraulic pump according to claim 4, wherein the hydrostatic compensation arrangement (5) comprises regulating means for regulating the magnitude of the third axial force (Fc).

6. A hydraulic pump according to claim 4 or 5, wherein the hydrostatic compensation arrangement (5) comprises means for limiting the maximum magnitude of the third axial force (Fc).

7. A hydraulic pump according to any one of the previous claims, wherein the gear pump comprises a driving gear with helical teeth (4a) and a driven gear with helical teeth (4b) and the driven gear with helical teeth (4b) in question is arranged coaxial with the impeller (3).

8. A method for controlling axial forces of a hydraulic pump, which hydraulic pump (1) includes a hydraulic motor (2) and an impeller (3), in which method, making up a first axial force (Fi) by the impeller (3) into a first axial direction, characterized in that using as the hydraulic motor (2) a gear pump which includes helical teeth (4a, 4b), whereby the gear with helical teeth (4a, 4b) produces a second axial force (Ft) into a direction opposite in relation to the first axial direction, and arranging the gear with helical teeth (4a, 4b) in question into connection with the impeller (3) and compensating the first axial force (Fi) by the second axial force (Ft) of the gear with helical teeth (4).

9. A method according to claim 8, wherein arranging the impeller (3) into connection with the gear with helical teeth (4) without an axial thrust bearing.

10. A method according to claim 8 or 9, wherein compensating the first axial force (Fi) substantially in its totality by the second axial force (Ft) of the gear with helical teeth (4).

11. A method according to claim 8 or 9, wherein producing a third axial force (Fc) by a hydrostatic compensate arrangement (5) on the axle of the gear with helical teeth (4) into the first axial direction and arranging the first axial force (Fi) and the third axial force (Fc) to together compensate the second axial force (Ft).

12. A method according to claim 11, wherein regulating the third axial force (Fc) such that the first axial force (Fi) and the third axial force (Fc) together compensate the second axial force (Ft).

13. A method according to claim 11 or 12, wherein limiting the magnitude of the third axial force (Fc) on a specific level.

14. A method according to any one of claims 8-13, wherein the gear pump comprises a driving gear with helical teeth (4a) and a driven gear with helical teeth (4b) and the driven gear with helical teeth (4b) in question is arranged coaxial with the impeller (3).

Images