Patent Application
20050169773
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:
a,
1
b are an oil pump with integrated electric motor;
a,
2
b are sectional and top plan views, respectively, of an oil pump with external drive; and
a-3d are different variations of oil pumps with pump housing, or rotor driven by separate drives C and D, as well as
Accordingly
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.
a and 2b illustrate an oil pump that essentially has an identical design compared with
In
Another possibility is in that a brake 16 is provided or that the blockage is implemented directly in the drive C.
a-4c 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 005 430.4 | Feb 2004 | DE | national |
