SPRING RETURN THROTTLE ACTUATOR, METHOD OF CONTROL THEREOF AND THROTTLE ASSEMBLY

Abstract

A spring return throttle actuator including: an electric, plural-coil DC motor having an output shaft, a throttle return spring, a gear transmission connected to the output shaft, a control unit adapted to control power supply to the DC motor, wherein the spring return throttle actuator has a movement range between closed throttle and opened throttle. The control unit is arranged to short-circuit at least two DC motor coils in order to create a DC motor return resist torque, and the return spring is balanced such that generated spring return torque over the whole movement range of the actuator does not exceed said DC motor return resist torque. The invention also relates to a method and a throttle assembly.

Claims

1. A spring return throttle actuator having a movement range between a closed throttle and an opened throttle: an electric, plural-coil DC motor having an output shaft; a throttle return spring; a gear transmission connected to the output shaft; and a control unit adapted to control power supply to the DC motor, wherein the control unit is configured to short-circuit at least two DC motor coils of said DC motor to create a DC motor return resist torque, and wherein the return spring is balanced such that generated spring return torque over a whole movement range of the actuator does not exceed said DC motor return resist torque.

2. An actuator according to claim 1, wherein the DC motor comprises.

3. An actuator according to claim 1, wherein the control unit comprises a circuit comprising a plurality of branches, with one branch connected to each one of the coils.

4. An actuator according to claim 3, wherein each branch of said circuit includes a transistor switch connected to each one of the coils.

5. An actuator according to claim 1, wherein at least one movement sensor is positioned to detect DC motor rotor movements.

6. An actuator according to claim 5, wherein a plurality of Hall sensors are positioned to detect DC motor rotor movements, said plurality of Hall sensors being rotationally distributed to increase measurement accuracy.

7. A method of controlling a spring return throttle actuator having a movement range between a closed throttle and an opened throttle, wherein said actuator comprises: an electric, plural-coil DC motor having an output shaft, a throttle return spring a gear transmission connected to the output shaft and a control unit adapted to control power supply to the DC motor, wherein said method comprises: short-circuiting at least two DC motor coils of said DC motor to create a DC motor return resist torque being of such a magnitude that a generated spring torque, from a balanced return spring, over a whole movement range of the actuator does not exceed said DC motor return resist torque.

8. A method according to claim 7, wherein the DC motor includes three coils, wherein short-circuiting comprises short-circuiting all three coils.

9. A method according to claim 7, wherein further comprising supplying power to the coils of said DC motor with power from a circuit comprising a plurality of branches, with one branch connected to each one of the coils.

10. A method according to claim 9, wherein each branch of said circuit is switched through separate transistor switches.

11. A method according to claim 7, further comprising monitoring movement of the rotor of said DC motor using at least one movement sensor.

12. A method according to claim 11, wherein monitoring movement of the rotor of said DC motor are performed using a plurality of Hall sensors distributed around the rotor to increase measurement accuracy.

13. A throttle assembly including a throttle, a spring return throttle actuator having a movement range between a closed throttle and an opened throttle, said actuator comprising: an electric, plural-coil DC motor having an output shaft; a throttle return spring; a gear transmission connected to the output shaft; and a control unit adapted to control power supply to the DC motor, wherein the control unit is configured to short-circuit at least two DC motor coils of said DC motor to create a DC motor return resist torque, and wherein the return spring is balanced such that generated spring return torque over a whole movement range of the actuator does not exceed said DC motor return resist torque.

14. An actuator according to claim 13, wherein the DC motor comprises three coils.

15. An actuator according to claim 13, wherein the control unit comprises a circuit comprising a plurality of branches, with one branch connected to each one of the coils.

16. An actuator according to claim 15, wherein each branch of said circuit includes a transistor switch connected to each one of the coils.

17. An actuator according to claim 13, wherein at least one movement sensor is positioned to detect DC motor rotor movements.

18. An actuator according to claim 17, wherein a plurality of Hall sensors are positioned to detect DC motor rotor movements, said plurality of Hall sensors being rotationally distributed to increase measurement accuracy.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0033] The invention will now be described in greater detail by way of embodiments and with reference to the annexed drawings, wherein:

[0034] FIG. 1 illustrates a throttle assembly including a spring return throttle actuator according to the invention,

[0035] FIG. 2 shows a control circuit for the inventive throttle actuator, and

[0036] FIG. 3 shows a simplified flow chart over an inventive method.

DETAILED DESCRIPTION OF THE INVENTION

[0037] FIG. 1, shows a throttle assembly whereof a spring return throttle actuator is generally depicted with reference number 1. The actuator 1 includes a DC motor 2 having three coils C1, C2 and C3 in its stator S. The rotor R is as usual provided with a permanent rotor magnet 3 and an output shaft 4.

[0038] A gear transmission 5 is connected to the output shaft 4 and an outgoing shaft 6 from the gear transmission 5 is coupled with its distal end to a throttle shaft 7 of a throttle 8. The actuator has a movement range between closed throttle and fully opened throttle.

[0039] It should be noted that the motor also could be directly connected to the throttle.

[0040] The throttle 8 is arranged in a channel 9 to control a gas stream flowing through the channel 9.

[0041] A throttle return spring 10 is positioned around the outgoing shaft 6 and functions to provide a spring torque urging the outgoing shaft 6 to rotate towards a normal position of the throttle 8 which may be fully open or fully closed depending on the nature of the throttle as explained above.

[0042] A control unit CPU is connected to the DC motor and is adapted to control supply of power to the DC motor and thereby to control the throttle position. Movement sensors, preferably Hall effect sensors, are indicated with D.

[0043] FIG. 2 illustrates a bridge circuit 11 positioned between a 24 Volts current source 12 for the supply of power to the three coils C1, C2 and C3 of the DC motor 3.

[0044] The bridge circuit includes a set of transistor switches T.sub.1-T.sub.6 that are made conductive-nonconductive to controllably power supply the DC motor 3.

[0045] In order to short-circuit all coils C1, C2 and C3, the transistor switches T.sub.1-T.sub.6 are made conductive and electric voltage is cut off. It is possible to make variations of the duration of conductivity of the transistor switches in order to apply force of different magnitudes by varying and by controlling transistor switches. It is also possible to short-circuit only two of the coils, whereby obviously a reduced rotation resist torque will arise compared to when all three coils are short-circuited.

[0046] It is possible to receive information from the DC motor and associated cables about its operation. If the motor is rotated, the rotational speed is directly proportional to the voltage. It is also possible to measure voltage which momentarily results in knowledge of rotational speed. For detection of rotational position of the rotor of the motor, a plurality of detectors are preferably being used. This gives information about throttle position.

[0047] The detectors are suitably stationary co-operate for example with a ring being rotationally associated with the rotor or with one of the shafts, said ring having a great number of evenly distributed marks or holes. Monitoring the durations between pulses from three distributed mark or hole detectors results in information of position and rotational speed. There is also a possibility to detect rotor acceleration if required for some reason.

[0048] In the simplified flow chart in FIG. 3, an exemplary method sequence related to the invention is briefly illustrated.

[0049] 13 indicates start of sequence.

[0050] 14 indicates evaluating flow requirements through a channel.

[0051] 15 indicates calculating desired throttle position.

[0052] 16 indicates initiating DC motor to position throttle in desired position.

[0053] 17 indicates verifying that throttle has reached the desired position.

[0054] 18 indicates initiating circuit to short-circuit DC motor coils to lock throttle.

[0055] 19 indicates end of sequence.

[0056] The sequence may be supplemented with additional steps and is repeated as required.

[0057] The invention can be modified within the scope of the annexed claims. For example, the control circuitry can be laid out differently as can be the DC motor, for instance, the number of coils of the DC motor can be other than three. The feature closed throttle is intended to include a case with totally blocked opening as well as a case with a certain minimum opening that might exist. With the feature opened throttle is intended the maximum opening achievable for the throttle in question.

[0058] Different kinds of sensors may be employed and they can be positioned in various places in association with the throttle assembly, for example close to the throttle itself.