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 control unit includes a movement monitoring circuit being arranged to monitor actuator movement forced by the throttle return spring and resisted by the 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, 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 control unit comprises a movement monitoring circuit configured to monitor actuator movement forced by the throttle return spring and resisted by the DC motor return resist torque.

2. An actuator according to claim 1, wherein the DC motor includes three coils.

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 comprises 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. An actuator according to claim 1, wherein the control unit comprises an evaluation circuit arranged to evaluate output signals from the movement monitoring circuit for deviations from stored values.

8. A method of controlling a spring return throttle actuator, wherein the actuator has a movement range between a closed throttle and a fully 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, said method comprising: short-circuiting at least two DC motor coils of said DC motor to create a DC motor return resist torque; and monitoring movement forced by the spring and resisted by the return resist torque over a whole movement range of the actuator.

9. A method according to claim 8, wherein the DC motor comprises three coils, wherein short-circuiting comprises short-circuiting two or three coils of said DC motor.

10. A method according to claim 8, 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.

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

12. A method according to claim 8, further comprising monitoring movement of the rotor of said DC motor using at least one movement sensor.

13. A method according to claim 12, 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.

14. A method according to claim 12, further comprising evaluating output signals from the movement sensor using an evaluation circuit to determine deviations from stored values.

15. A method according to claim 8, supplementing a result obtained from movement forced by the spring being monitored with at least two DC motor coils being short-circuited with movement forced by the spring being monitored without DC motor coils being short-circuited in order to create DC motor return resist torques of different levels.

16. A throttle assembly including a throttle and 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 the DC motor to create a DC motor return resist torque, and wherein the control unit comprises a movement monitoring circuit configured to monitor actuator movement forced by the throttle return spring and resisted by the DC motor return resist torque.

17. A throttle according to claim 16, wherein the control unit comprises a circuit comprising a plurality of branches, with one branch connected to each one of the coils.

18. A throttle according to claim 17, wherein each branch of said circuit comprises a transistor switch connected to each one of the coils.

19. A throttle according to claim 16, wherein at least one movement sensor is positioned to detect DC motor rotor movements.

20. A throttle according to claim 16, wherein the control unit comprises an evaluation circuit arranged to evaluate output signals from the movement monitoring circuit for deviations from stored values.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0056] The invention will now be described in greater detail by way of embodiments and with reference to the annexed drawings, wherein:

[0057] FIG. 1 illustrates a throttle assembly including a spring return throttle actuator according to the invention,

[0058] FIG. 2 shows a control circuit for the inventive throttle actuator, and

[0059] FIG. 3 shows a simplified flow chart over an inventive method.

DETAILED DESCRIPTION OF THE INVENTION

[0060] 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.

[0061] 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.

[0062] The throttle 8 is arranged in a channel 9 to control a gas stream flowing through the channel 9.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] The bridge circuit includes a set of transistor switches T.sub.1-T.sub.6 that are made conductivenon conductive to controllably power supply the DC motor 3.

[0067] 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.

[0068] 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 is preferably being used. This gives information about throttle position.

[0069] The detectors are suitably stationary and for example co-operating 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.

[0070] In the simplified flow chart in FIG. 3, an exemplary method sequence related to the invention is briefly illustrated.

[0071] 13 indicates start of sequence.

[0072] 14 indicates initiating DC motor to position throttle in desired position where the return spring is strained and stretched and verifying that throttle has reached the desired position.

[0073] 15 indicates cutting current to DC motor and initiating circuit to short-circuit DC motor coils to obtain a resist torque.

[0074] 16 indicates monitoring throttle or rotor movements effected by the return spring with short-circuited coils.

[0075] 17 indicates evaluating monitored throttle movement pattern in relation to a stored exemplary movement curve.

[0076] 18 indicates amending and adapting engine control values to established prevailing throttle actuation conditions.

[0077] 19 indicates issuing a condition message to the user and ending of sequence.

[0078] The sequence may be supplemented with additional steps and is repeated as required.

[0079] 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.

[0080] 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.

[0081] 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.