US20050169773A1

US20050169773A1 - Oil pump for an automatic transmission of a motor vehicle

Info

Publication number: US20050169773A1
Application number: US11/050,277
Authority: US
Inventors: Josef Schwarz; Gerd Frotscher; Thilo Schmidt
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2004-02-04
Filing date: 2005-02-03
Publication date: 2005-08-04
Also published as: JP2005220910A; DE102004005430A1

Abstract

An oil pump for a motor vehicle automatic transmission comprising a gear housing (2), a pump housing (1) and a pump rotor (3) that can be driven by a motor of the motor vehicle. In order to improve the application possibilities in a motor vehicle, in this pump the pump housing (1) can be driven such that the relative rotational speed between the pump rotor (3) and the pump housing (1) can be modified.

Description

The invention relates to an oil pump for a motor vehicle automatic transmission pursuant to the preamble of patent claim 1.
For supplying the lubricating device and the control and actuating devices, automatic transmissions in motor vehicles require an oil pump, which often is designed as a positive-displacement pump and is driven by the rotational speed of the driving motor of the motor vehicle.
Today oil pumps are still primarily designed as so-called fixed displacement pumps, the flow rate of which increases proportionally to the speed for the driving motor. The pump is generally designed based on the idle speed of the motor. The flow rate supplied must already meet the requirements of the gear devices that need to be supplied. In the case of higher rotational speeds of the motor such a fixed displacement pump, however, conveys a multiple of the quantity that is required as such. Consequently such fixed displacement pumps require too much power, cavitate and generate too high a noise level. Additionally, the oil line cross-sections' dimension has to be oversized. Moreover, oil flow is not possible when the motor is shut off.
From DE 197 50 675 C1 we already know of an oil pump, which apart from the drive by the internal combustion engine is equipped with an additional electric drive. This way it is possible to convey an oil flow even when the internal combustion engine is shut off or to increase the flow rate at low rotational speeds.
Against this background, therefore, it is the object of the invention to create an oil pump for motor vehicle transmissions with improved efficiency across the entire working range, wherein the flow rate should be as independent as possible from the rotational speed of the internal combustion engine.
The solution to this object results from the features of the main claim, while beneficial embodiments and further developments of the invention are revealed in the dependent claims.
The invention is based on the knowledge that the flow rate of an oil pump can be changed independently from the rotational speed of the pump rotor by rotating the pump housing. Accordingly, the oil pump itself together with the corresponding intake and pressure channels can be designed for a certain operating point, which is defined by a certain nominal speed of the pump rotor, wherein the flow rate, then in the case of a rotational speed of the pump rotor that deviates from the nominal speed, can be modified by rotating the pump housing.
When the rotational speed of the pump rotor is below the nominal rotational speed, the pump housing is rotated against the sense of rotation of the pump rotor, so that the relative rotational speed between the pump housing and pump rotor is increased. Since the relative rotational speed between the pump housing and the pump rotor determines the flow rate, thus the flow rate increases also. The pump housing, in this case, acts like a second pump rotor and increases the driving pressure differential between the pump rotor input and the pump housing output.
When the actual rotational speed of the pump rotor is above the nominal rotational speed, the pump housing is rotated in the same direction as the pump rotor with a reverse effect so that the flow rate is reduced.
Due to the possibility of adjusting the flow rate by rotation of the pump housing, the design area of the entire oil pump is reduced significantly so that the efficiency increases overall and the oversizing required so far for the intake and pressure channels can be eliminated. Furthermore, according to the invention, the solution offers the advantage that an oil current can be generated even when the pump rotor is standing still. The standstill of the pump rotor can either be caused by the fact that the motor of the vehicle is shut off or that the pump rotor or its drive has failed due to a technical defect.
An especially simple possibility for driving the pump housing and/or the pump rotor is in the use of an electric motor with simple control. Additionally, it can be provided that the rotor of the electric motor is arranged in the pump housing or the pump rotor and the stator in the stationary gear housing. This results overall in an especially compact design.
Apart from this, it can be provided that the housing drive is implemented by means of a tooth system on the housing or by directly flange-mounting a separate electric motor on the pump housing.
The oil current is preferably guided in bores of the pump housing, wherein the bores join into ring grooves that are incorporated on the pump housing and/or the gear housing. The ring grooves are preferably arranged axially and/or radially adjacent to each other. The object of the ring grooves is to establish a permanent flow connection between the stationary gear housing and the rotating pump housing.
The pump housing is designed such that it can be blocked from rotation at least in one sense of rotation when it is shut off so that the torque applied by the pump rotor on the pump housing can be introduced into the gear housing.
Blockage can be implemented by a freewheel or by a brake that acts in one or both rotational directions.
Alternatively, blockage can also be formed by a force that is applied onto the pump housing by an electric motor. Through an appropriate design of the electric machine, a detent torque can be generated during a short circuit of the stator coils, which generates a braking effect and thus can act as a brake.
To illustrate the invention, a drawing is attached to the description. It shows:
FIGS. 1 a, 1 b are an oil pump with integrated electric motor;
FIGS. 2 a, 2 b are sectional and top plan views, respectively, of an oil pump with external drive; and
FIG. 3 a-3 d are different variations of oil pumps with pump housing, or rotor driven by separate drives C and D, as well as FIG. 4 a-4 c different variations of oil pumps with integrated electric motor.
Accordingly FIGS. 1 a and 1 b show an oil pump with integrated electric motor in a sectional view and top plan view. A pump housing 1 is arranged rotational in a stationary gear housing 2 and accommodates a pump rotor 3. The pump rotor 3 is driven in the familiar fashion, e.g., directly by an internal combustion engine, which is not shown. Upon rotation of the pump rotor 3, oil is taken in by an intake channel 14 via a ring groove 9, a bore 7 and an intake pocket 5.
Additionally, the pump rotor 3 comprises a pump sickle 8 which, during rotation of the pump rotor 3, moves the oil current from the intake pocket 5 into a pressure pocket 4. From the pressure pocket 4, the oil current is conveyed via a bore 11 and a ring groove 12 into a pressure channel 13 from where the various actuators can be supplied with oil current, which can be actuated by the applied oil pressure. The pressure channel 13 and the intake channel 14 are preferably arranged in an axial direction opposite from each other in the pump or in the gear housing 2.
Several bores 7 and 11 (preferably four) can be provided, distributed about the circumference. The pump rotor 3 is arranged in the pump housing 1 which, in turn, is rotatably seated in the stationary gear housing 2. The pump housing 3 comprises a rotor 6 of an electric motor integrated in the housing's outer circumference surface, wherein a stator 10 of the motor is located in the stationary gear housing 2.
In the case of the stationary pump housing 1, the flow rate of the oil pump is determined solely by the rotational speed of the pump rotor 3. However, since the relative rotational speed between the pump rotor 3 and the pump housing 1 is decisive for the flow rate, according to the invention, the design of the oil pump now allows for the flow rate to be modified by rotating the pump housing 1. Therefore, rotation of the pump housing 1, in the sense of rotation of the pump rotor 3 (sense of rotation A), results in a decrease of the flow rate and, in the opposite direction (sense of rotation B), in an increase in the flow rate.
Since the gear housing 2 is a stationary part and the pump housing 1 rotates, it is especially beneficial to provide the ring groove 9 and 12, both in the intake path and in the pressure path, so that a constant flow connection exists between the bores 7 and 11 and the intake channel 14 and the pressure channel 13.
The now created possibility of modifying the flow rate by way of rotating the pump housing 1 allows to design both the intake channel 14 and the pressure channel 13 in accordance with the optimal flow rate and only a relatively narrow working range must be provided for the design of the oil pump. Overall, this leads to an improvement in the efficiency across the entire working range and to a compact design, since the oversizing required until now can be eliminated.
FIGS. 2 a and 2 b illustrate an oil pump that essentially has an identical design compared with FIG. 1, wherein both the pump rotor 3 as well as the pump housing 1 are driven by driving shafts 19, and 20 of external drives C, D. Such drives can be of mechanical or electro-mechanical nature. To the extent that the electric drive is not integrated in the pump housing, the housing drive can be implemented via a gear step by way of a tooth system on the pump housing, by direct flange-mounting of a separate electric motor to the same or the pump rotor.
In FIG. 3 a-3 d, various possibilities are illustrated as to how blockage of the pump housing 1 in the gear housing 2 can take place. Blockage of the pump housing 1 is important here in that the pump housing 1 is not driven and the torque applied onto the pump housing 1 by the pump rotor 3 has to be introduced directly into the gear housing 2. One design possibility consists of a freewheel 17, which is arranged either on the outer circumference of the pump housing 1 or offset radially inward on a step 18 of the gear housing 2. The freewheel 17, 18 must be designed such that it blocks against the sense of rotation of the pump rotor 3.
Another possibility is in that a brake 16 is provided or that the blockage is implemented directly in the drive C.
FIG. 4 a-4 c illustrate various possibilities as to how the pump housing 1 can be driven by the stator 10 and the rotor 6, as well as how it can be blocked by way of the freewheel 17 or the brake 16. The use of the electro-motor drive moreover offers the advantage that it can also be used to brake or block the pump housing 1.
The brake 16 offers an additional benefit in that the support force can be lowered and the rotation of the pump housing 1 is achieved by releasing the brake 16. The rotation of the pump housing 1 automatically leads to a decrease in the flow rate.

REFERENCE NUMERALS

1 pump housing
2 gear house
3 pump rotor
4 pressure pocket
5 intake pocket
6 rotor
7 bore
8 pump sickle
9 ring groove
10 stator
11 bore
12 ring groove
13 pressure channel
14 intake channel
15 intermediate plate
16 brake
17 freewheel
18 step
19 driving shaft
20 driving shaft
C drive for the pump housing
D drive for the pump rotor

Claims

1-14. (canceled)

15. A oil pump for a motor vehicle automatic transmission, comprising a gear housing (2), a pump housing (1), and a pump rotor (3), that can be driven by a motor of the motor vehicle, the pump housing (1) can be driven such that a relative rotational speed between the pump rotor (3) and the pump housing (1) can be modified:

16. The oil pump according to claim 15, wherein one or more of the pump rotor (3), and the pump housing (1) can be driven by means of an electric motor, a rotor (6) of the electric motor is integrated in one or more of the pump rotor (3), and the pump housing (1).

17. The oil pump according to claim 15, wherein bores (7, 11) are provided in the pump housing (1) for guiding an oil flow.

18. The oil pump according to claim 17, wherein the bores (7, 11) join into ring grooves (9, 12) that are incorporated on one or more of the pump housing 1 and the gear housing (2).

19. The oil pump according to claim 18, wherein the ring grooves (9,12) in a pump are arranged one of axially or radially opposite from each other in the pump housing (1).

20. The oil pump according to claim 15, wherein the pump housing (1) can be blocked from torsion at least in one sense of rotation when a drive is shut off.

21. The oil pump according to claim 20, wherein blockage consists of a freewheel (17) that blocks against a sense of rotation of the pump rotor (3).

22. The oil pump according to claim 20, wherein blockage consists of a brake (16).

23. The oil pump according to claim 20, wherein blockage occurs by an electro-motor force exercised by the electric motor on the pump housing (1).

24. The oil pump according to claim 15, wherein a housing drive (C) can be implemented by means of one of a tooth system on the pump housing (1) or by directly flange-mounting a separate electric motor.

25. The oil pump according to claim 15, wherein a reducing gear is provided between the pump housing (1) and a drive.

26. The oil pump according to claim 15, wherein the pump housing (1) can be driven in a sense of rotation of the pump rotor (3) when a flow rate is greater than a designed flow rate of the pump rotor (3).

27. The oil pump according to claim 15, wherein the pump housing (1) can be driven against a sense of rotation of the pump rotor (3) when a flow rate is smaller than a designed flow rate of the pump rotor (3).

28. The oil pump according to claim 15, wherein a pressure channel (13) and an intake channel (14) are arranged in an axial direction opposite from each other in one of the pump or the gear housing (2).