Electric pump actuator, stepless transmission with electric pump actuator and control method for an electric pump actuator

Abstract

An electric pump actuator for a continuously variable transmission includes a gear wheel pump, a first electric motor, a second electric motor, and an electric control unit. The gear wheel pump has a first gear wheel and a second gear wheel meshing with the first gear wheel. The first electric motor is for actuating the first gear wheel, and the second electric motor is for actuating the second gear wheel independent of the first gear wheel. The electronic control unit is arranged to control the first electric motor to transmit a first torque to the first gear wheel, and control the second electric motor to transmit a second torque to the second gear wheel that is set against the first torque in at least one rotation angle range.

Claims

1. An electric pump actuator for a continuously variable transmission comprising: a gear wheel pump comprising: a first gear wheel; and a second gear wheel meshing with the first gear wheel; a first electric motor for actuating the first gear wheel; a second electric motor for actuating the second gear wheel independent of the first gear wheel; and an electronic control unit arranged to: control the first electric motor such that the first electric motor applies a first torque to the first gear wheel; and control the second electric motor such that the second electric motor operates as a generator such that the second electric motor applies a second toque to the second gear wheel that is set against the first torque in at least one rotation angle range so that fluid leakage is reduced or prevented between the first gear wheel and the second gear wheel.

2. The electric pump actuator of claim 1, wherein: the electronic control unit is arranged to control the first electric motor and the second electric motor such that a first absolute value of the first torque is greater than a second absolute value of the second torque; or the electronic control unit is arranged to control the first electric motor and the second electric motor such that: the second absolute value is lower than the first absolute value in a first rotation angle range; and the first torque has a third absolute value greater than the first absolute value and the second torque has a fourth absolute value lower than the third absolute value and higher than the second absolute value in a second rotation angle range.

3. The electric pump actuator of claim 1, wherein: the electronic control unit is arranged to control the first electric motor and the second electric motor such that: a second absolute value of the second torque is lower than a first absolute value of the first torque in a first rotation angle range; the first torque has a third absolute value greater than the first absolute value and the second torque has a fourth absolute value lower than the third absolute value and higher than the second absolute value in a second rotation angle range; and a first delta amount of an increase in the third absolute value from the first absolute value equals a second delta amount of an increase in the fourth absolute value from the second absolute value.

4. The electric pump actuator of claim 1, further comprising: a first inverter for converting a direct current voltage into a first alternating current voltage and providing the first alternating current voltage to the first electric motor in a controlled manner via the electronic control unit; and a second inverter for converting the direct current voltage into a second alternating current voltage and providing the second alternating current voltage to the second electric motor in a controlled manner via the electronic control unit.

5. The electric pump actuator of claim 1, further comprising a third electric motor for actuating one of the first gear wheel or the second gear wheel.

6. The electric pump actuator of claim 1, wherein the first electric motor and the second electric motor are each motor-generators designed to convert mechanical energy into electrical energy in addition to converting electrical energy into mechanical energy.

7. A continuously variable transmission for a vehicle comprising the electric pump actuator of claim 1.

8. The electric pump actuator of claim 1, wherein the second electric motor is configured to provide electric power to the first electric motor in the at least one rotation angle range.

9. A control method for an electric pump actuator comprising: providing a gear wheel pump comprising: a first gear wheel driven by a first electric motor; a second gear wheel driven by a second electric motor; and an electronic control unit for controlling the first electric motor and the second electric motor; applying a first torque to the first gear wheel via the first electric motor; and applying a second torque to the second gear wheel via the second electric motor operating as a generator, wherein the second torque is set against the first torque so that fluid leakage is reduced or prevented between the first gear wheel and the second gear wheel.

10. The control method of claim 9, wherein: absolute values of the first torque and the second torque are constant; or the absolute values of the first torque and the second torque vary over a rotation angle range.

11. The control method of claim 9, wherein: absolute values of the first torque and the second torque vary over a rotation angle range; and a first delta amount by which an absolute value of the first torque is increased equals a second delta amount by which an absolute value of the second torque is increased.

12. The control method of claim 9, wherein the second electric motor is configured to provide electric power to the first electric motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure is further explained below with reference to exemplary embodiments with the aid of figures. In the drawings:

(2) FIG. 1 illustrates schematically a view of an example embodiment of an electric pump actuator for a continuously variable transmission,

(3) FIG. 2 illustrates a sectional view of the electric pump actuator in FIG. 1,

(4) FIG. 3 illustrates schematically a sectional view of the electric pump actuator in FIG. 1 and FIG. 2 having two electric motors on one side,

(5) FIG. 4 illustrates schematically a sectional view of an electric pump actuator of a further example embodiment or configuration having a motor on each side,

(6) FIG. 5 illustrates schematically a sectional view of an electric pump actuator of a further example embodiment or configuration having two motors on each side,

(7) FIG. 6 illustrates schematically a continuously variable transmission having a CVT transmission adjusting procedure and a contact pressure force controlling procedure,

(8) FIG. 7 illustrates a diagram, which illustrates the difference between a conventional electric pump actuator and the electric pump actuator in accordance with the first embodiment and also the control of the electronic control unit in dependence upon the rotation angle of the electric pump actuator,

(9) FIG. 8 illustrates schematically a diagram of a flow rate and the associated torque of the electric pump actuator in FIG. 7, and a first control method, and

(10) FIG. 9 illustrates schematically a diagram of an example embodiment of the electric pump actuator in which the electronic control unit controls the first and second electric motor with reference to a second preferred control method.

DETAILED DESCRIPTION

(11) The figures are schematic in nature and are only to be used to facilitate the understanding of the invention. Identical elements are provided with the same reference numerals. The features of the different embodiments are interchangeable.

(12) FIG. 1 and FIG. 2 illustrate an electric pump actuator (EPA) 1 for a continuously variable transmission (CVT) 2 (ref. FIG. 6), for a CVT transmission adjusting procedure, or for a contact pressure force controlling procedure. FIG. 1 illustrates the corresponding longitudinal section through the electric pump actuator 1 and FIG. 2 illustrates the corresponding cross section. The electric pump actuator 1 comprises an external gear wheel pump 3 having a spur toothing arrangement having two meshing gear wheels 4 and 5 in which the first gear wheel 4 may be actuated via a first electric motor 6 independently of the second gear wheel 5 via a second electric motor 7. The two electric motors 6, 7 are electric motor-generators.

(13) The first electric motor 6 is designed so as to transmit a first torque M1 to the first gear wheel 4 and the second electric motor 7 is designed so as to transmit a second torque M2 to the second gear wheel 5 accordingly. An electronic control unit (ECU) 8 in this case controls the two electric motors 6, 7 in such a manner that via meshing the two gear wheels 4, 5, the force that results from the second torque M2 is set against any force that results from the first torque M1 in at least one rotation angle section 9 (cf. FIGS. 7-9). The torque vectors (pointing in the same direction) of the torques M1, M2 in this case prescribe identical rotation directions of the gear wheels 4, 5 (cf. bottom of FIG. 7).

(14) The electric pump actuator 1 comprises, for the control of the two electric motors 6, 7, two inverters 10, which convert a direct current voltage of a conventional car battery 11, in this case a 12 V lead acid battery, into a three-phase alternating current in order to accordingly control and actuate the two electric motors 6, 7. The two inverters 10 are connected electrically on one side via direct current lines 12 to the battery 11, and on the other side via respectively three alternating current lines 13 to the first and second electric motors 6 and 7. Control lines 17 for actuating purposes connect the ECU 8 to the inverters 10. The two gear wheels 4, 5 are mounted in a housing 14, which may be produced from metal or a synthetic material, and are accordingly sealed with respect to fluids from the outside, to the supply ducts and discharge ducts, via shafts 16, which extend coaxially to rotary axles 15 of the gear wheels 4, 5. The rotary axles 15 of the two gear wheels 4, 5 in this case lie parallel to one another and the gear wheels 4, 5 essentially lie in a plane with the result that their teeth 18 (cf. also FIG. 7) engage in one another and are in operative engagement. The first electric motor 6 generates the torque M1, the absolute value of said first torque being higher than the absolute value of the torque M2 with the result that the second electric motor 7 is operated as a generator and provides an electric power to the first electric motor 6. This is illustrated for clarity with the dashed lines as the power flow.

(15) FIGS. 3-5 illustrate different configurations of an electric pump actuator 1 in accordance with different embodiments. FIG. 3 illustrates the configuration in accordance with the first example embodiment (cf. FIGS. 1 and 2) having two separate electric motors 6, 7 that are arranged on the same side of the gear wheel pump 3 (on the right-hand side in FIG. 3). The right-hand side part of FIG. 1, therefore the electronic system, for the sake of clarity has not been illustrated. FIG. 4 illustrates an electric pump actuator 1 of a further embodiment or configuration, wherein the electric motors 6, 7 are arranged on different sides (in FIG. 4 on the left-hand side and right-hand side) of the gear wheel pump 3. FIG. 5 illustrates a further embodiment of an electric pump actuator 1 having four separate electric motors 6, 7 or two first electric motors 6 and two second electric motors 7, which accordingly engage on the respective rotary axle 15 of the gear wheels 4, 5, wherein two electric motors 6, 7 are respectively arranged on one side.

(16) FIG. 6 illustrates schematically a first embodiment of a continuously variable transmission 2 having an electric pump actuator 1 that is used for a CVT transmission adjusting procedure and an electric pump actuator 1 that is used for a contact pressure force controlling procedure. The lower (cf. FIG. 6) electric pump actuator 1 is used mainly for the purpose of providing a relatively constant pressure to the continuously variable transmission 2 for a defined contact pressure force controlling procedure, whereas the other electric pump actuator 1 is used as a CVT transmission adjusting procedure and accordingly regulates a transmission ratio by means of the different contact pressure forces on the first CVT shaft and the second CVT shaft. In the case of this embodiment, only one individual battery 11 is necessary. A main controller accordingly controls the electronic control units 8 of the two electric pump actuators 1. Alternatively, the two separate electronic control units 8 may also be integrated into a single main controller.

(17) The electronic control unit 8 of the first embodiment of the electric pump actuator 1 is controlled according to a control method for the electric pump actuator 1 and is explained below together with the electric pump actuator 1.

(18) FIG. 7 illustrates in a diagram a comparison of a conventional electric pump actuator 1′ (dashed line), which comprises an individual electric motor (individual E-motor), with an electric pump actuator 1 (solid line, double E-motor) in which the ECU 8 controls the first and second electric motor 6, 7 as described above. This control forms the basis of the control method for an electric pump actuator.

(19) The first and the second gear wheel 4, 5 comprise respectively the same number of teeth 18, as a result of which for an individual tooth segment a period/a specific period angle 20 of, in this case, 36° occurs in the case of an entire rotation of 360°. In this period 20 or this period angle 20, as is apparent with reference to the upper diagram in FIG. 7, a curve of a flow rate 21 and also an engagement of the gear wheels 4, 5 repeats. In the figure, eight teeth 18 are illustrated per gear wheel 4 or 5. Ten teeth 18 would however be suitable for the diagram that is illustrated at the top.

(20) In the case of a conventional electric pump actuator 1′ according to the prior art having a single electric motor/individual E-motor, as illustrated in the middle region of FIG. 7, in the case of defined rotation angles of the electric pump actuator, a leakage would occur, since the teeth of the first and the second gear wheel do not lie against one another here. If, conversely, the electric pump actuator 1 is operated and by means of the electronic control unit 8, for example via the control method in accordance with the disclosure, said electric pump actuator is controlled in such a manner that the first electric motor 6 is influenced with a first torque M1, and the second electric motor 7 is influenced with a torque M2, the force that results from the second torque M2 is set against any force that results from the first torque M1 in at least one rotation angle section 9 (ref. FIG. 8). The second gear wheel 5 is thus actively rotated in the region of the leakage against the first gear wheel 4 and the two teeth 18 of the gear wheels 4, 5 that are respectively in operative engagement, lie against one another and prevent a leakage. As is apparent in the upper diagram in FIG. 7, the flow rate 21, in the case of a pump actuator 1, remains stable and relatively constant, and a return flow, such as is the case in conventional electric pump actuators 1′, may be avoided.

(21) FIG. 8 again illustrates, in the upper part, the diagram in FIG. 7 and also, in the lower part, a corresponding control method for the electric pump actuator 1 of a first variant, according to which the ECU 8 influences the electric motors 6, 7 with the first torque M1 and the second torque M2. As already shown in FIG. 7, the two diagrams comprise a period 20 of 36°/36 degrees/36 deg. in which the graph periodically repeats. In the lower part of FIG. 8, it is apparent that the absolute value of the first torque M1 of the first electric motor 6 of the electric pump actuator 1 has been increased by a delta amount 19 with respect to the individual E-motor (conventional EPA according to the prior art), whereas the absolute value of the second torque M2 of the second electric motor 7 has also been increased by precisely this delta amount 19. The first electric motor 6 requires an accordingly higher power for the higher absolute value of the first torque M1, or the higher first torque M1, and operates in the drive mode, whereas, although the second electric motor 7 applies a specific torque M2, owing to the higher absolute value of the first torque M1 and the throughflow with the fluid, said second electric motor operates in a regenerative mode or generator mode and provides the electrical power that is generated by means of said regenerative or generator mode to the first electric motor 6. The control method therefore controls the first electric motor 6 and generates a constant absolute value of the first torque M1, while the second electric motor 7 is controlled in such a manner that this generates a constant absolute value of the torque M2, and the force that results from the second torque M2 counteracts any force resulting from the first torque. As is apparent in the diagram in the upper part in FIG. 8, the flow rate 21 is stabilized by means of the electric pump actuator 1 or the control method for an electric pump actuator.

(22) FIG. 9 illustrates an electric pump actuator 1 of a further embodiment or a control method for an electric pump actuator 1 according to a further (control) variant. In the first predetermined rotation angle ranges 22 of the gear wheels 4, 5 or the gear wheel pump 3, the first torque M1 is controlled in such a manner that said first torque adopts a constant absolute value 23, while, simultaneously, the second torque M2 adopts the value zero or the second electric motor 7 is passive. In the second predetermined second rotation angle ranges 9 of the gear wheels 4, 5, the first torque M1 adopts an absolute value that is greater than the constant absolute value 23 of the first predetermined rotation angle ranges 22, and the second torque M2 simultaneously adopts an absolute value that remains lower than the absolute value of the first torque M1 but is greater than the absolute value of the second torque M2 in the first rotation angle range 22. The delta amount 19 by which the electronic control unit 8 increases the constant absolute value 23 of the first torque M1 of the first predetermined rotation angle ranges 22 is identical to the delta amount 19 by which the absolute value of the second torque M2 is increased.

(23) As a consequence, the electric pump actuator 1 may be operated in a similar manner to the conventional electric pump actuator 1′ in the case of the first rotation angle ranges 22 having only the first electric motor 6 having a first torque M1 having the constant absolute value 23, and only in the second rotation angle ranges 9 or rotation angle sections 9 in which a leakage occurs, is an accordingly higher power or greater absolute value of the first torque M1 or higher first torque M1 and an associated higher absolute value of the second torque M2 of the second electric motor 7 controlled in order to efficiently prevent a return flow of the fluid (in this case oil) and in order to stabilize the electric pump actuator 1. This procedure, as is apparent in FIG. 9, is periodically repeated with the period 20 that is dependent upon the number of teeth 18 of the gear wheels 4, 5 of the gear wheel pump 3.

(24) An operation of the electric pump actuator 1 is also conceivable in which in predetermined time sections the control is applied in accordance with FIG. 8 and in other time sections the control is applied in accordance with FIG. 9. Therefore the two control methods are combined in dependence upon time.

REFERENCE NUMERALS

(25) 1′ Conventional electric pump actuator 1 Electric pump actuator 2 Continuously variable transmission 3 Gear wheel pump 4 First gear wheel 5 Second gear wheel 6 First electric motor 7 Second electric motor 8 Electronic control unit 9 Second rotation angle section/rotation angle range 10 Inverter 11 Battery 12 Direct current line 13 Alternating current line 14 Housing 15 Rotary axle 16 Shaft 17 Control line 18 Tooth 19 Delta amount/difference value 20 Period 21 Flow rate 22 First rotation angle section/rotation angle range 23 Constant absolute value M1 First torque M2 Second torque