DEVICE FOR DETECTING SPEED OF A ROTATABLE ELEMENT, METHOD AND VEHICLE

Abstract

A device for detecting and monitoring crank shaft rotary speed and position in a four stroke engine, wherein a first and a second sensor are arranged to sense passage of reference marks on a rotatable element or elements. The first sensor is a high precision sensor which is arranged to sense passage of reference marks on a crank shaft flywheel of the engine, and the second sensor is a low speed sensor which is arranged to sense passage of reference marks on the crank shaft flywheel or reference marks or a wheel being associated with a cam shaft of the engine. The invention also concerns a method and a vehicle.

Claims

1. A device for detecting and monitoring crank shaft rotary speed and position in a four stroke engine, said device comprising: a first and a second sensor are arranged to sense passage of reference marks on a rotatable element or elements, wherein the first sensor is a high precision sensor which is arranged to sense passage of reference marks on a crank shaft flywheel of the engine, and the second sensor is a low speed sensor which is arranged to sense passage of reference marks on the crank shaft flywheel or reference marks or a wheel being associated with a cam shaft of the engine.

2. A device according to claim 1, wherein the first sensor is an inductive sensor.

3. A device according to claim 1, wherein the second sensor is a Hall effect sensor or a magnetoresitive sensor.

4. A device according to claim 1, wherein the first and second sensors are connected to a control unit which is arranged to emit signals to a fuel injection system.

5. A device according to claim 1, wherein the first and second sensors are pre-installed on a carrier member with determined mutual separation, and the carrier member together with the first and second sensors is installable as an integral unit at a chosen position in association with the flywheel.

6. A device according to claim 1, wherein the reference marks are recesses or protrusions.

7. A method for detecting and monitoring crank shaft position in a four stroke engine, wherein a first and a second sensor senses passage of reference marks on a rotatable element or elements, wherein the first sensor being a high precision sensor senses passage of reference marks on a crank shaft flywheel of the engine, and the second sensor being a low speed sensor senses passage of reference marks on the crank shaft flywheel or reference marks on a wheel being associated with a cam shaft of the engine.

8. A method according to claim 7, wherein reference marks on the wheel being connected to a camshaft for valve control are sensed by the second sensor.

9. A method according to claim 7, wherein reference marks on the flywheel are sensed also by the second sensor.

10. A method according to claim 7, wherein the first sensor senses reference marks inductively.

11. A method according to claim 7, wherein the second sensor senses reference marks through the Hall effect or through magnetoresitive effect.

12. A method according to claim 9, wherein signals from the first and second sensors are led to a control unit which emits signals to a fuel injection system for synchronized fuel injection.

13. A method according to claim 9, further comprising: pre-installing the first and second sensors with determined mutual separation on a carrier member; and installing the carrier member together with the first and second sensors as an integral unit at a chosen position in association with the flywheel.

14. A vehicle comprising a device for detecting and monitoring crank shaft rotary speed and position in a four stroke engine, said device comprising: a first and a second sensor are arranged to sense passage of reference marks on a rotatable element or elements, wherein the first sensor is a high precision sensor which is arranged to sense passage of reference marks on a crank shaft flywheel of the engine, and the second sensor is a low speed sensor which is arranged to sense passage of reference marks on the crank shaft flywheel or reference marks or a wheel being associated with a cam shaft of the engine.

15. A vehicle according to claim 14, wherein the first sensor is an inductive sensor.

16. A vehicle according to claim 14, wherein the second sensor is a Hall effect sensor or a magnetoresitive sensor.

17. A vehicle according to claim 14, wherein the first and second sensors are connected to a control unit which is arranged to emit signals to a fuel injection system.

18. A vehicle according to claim 14, wherein the first and second sensors are pre-installed on a carrier member with determined mutual separation, and the carrier member together with the first and second sensors is installable as an integral unit at a chosen position in association with the flywheel.

19. A vehicle according to claim 14, wherein the reference marks are recesses or protrusions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The invention will now be described in greater detail by way of embodiments and with reference to the annexed drawings, wherein:

[0044] FIG. 1 shows a first variant of the invention in connection with a flywheel,

[0045] FIG. 2 shows a second variant of the invention,

[0046] FIG. 3 shows a third variant of the invention,

[0047] FIG. 4 shows diagrammatically the invention installed for cooperation with a flywheel of an internal combustion engine, and

[0048] FIG. 5 shows diagrammatically a vehicle equipped with an inventive device.

DETAILED DESCRIPTION OF THE INVENTION

[0049] FIG. 1 illustrates the invention in connection with a rotatable element in the form of a flywheel 1 of an internal four stroke combustion engine. The flywheel 1 has a plurality of reference marks 9 distributed around its circumference. In the shown example, the reference marks 9 are surface recesses such as holes drilled in an envelope surface of the flywheel 1.

[0050] A first sensor 3 and a second sensor 4 are arranged to sense passage of the reference marks 9 and to issue signals to a control unit 100.

[0051] The first sensor 3 is high precision sensor being an inductive sensor which senses the reference marks 9 inductively so as to obtain high positioning precision. The second sensor 4 is a low speed sensor which senses reference marks 9 through the Hall effect or through magnetoresitive effect already at very low rotary speeds.

[0052] Signals from the first and second sensors are led to the control unit 100 which emits signals to a fuel injection system for synchronized fuel injection.

[0053] In order to obtain information about where in the 720° working cycle the engine is so as to obtain full synchronization, the device in FIG. 1 is advantageously supplemented for example with a sensor sensing cam shaft position (not shown) or more sophisticated logic evaluating engine response e.g. to fuel injections (not shown). This is previously known in the art and therefore not explained further here.

[0054] FIG. 2 illustrates a variant of the invention wherein a first sensor 3 being a high precision sensor is arranged in association with the flywheel 1 to sense passage of the reference marks 9 and to issue signals to a control unit 100. A second sensor 4 being a low speed sensor is in this embodiment instead associated with a wheel 1′ which is coupled to a cam shaft of the engine in question.

[0055] In order to obtain high quality positioning, the first sensor 3 is also in this case arranged to sense the reference marks 9 on the flywheel because of the rotational stability thereof which is explained with the high weight and high moment of inertia.

[0056] The second sensor 4 is also in this case a low speed sensor which with reasonable quality senses reference marks 9′ through the Hall effect or through magnetoresitive effect already at very low rotary speeds. The signals from the second sensor will be used for quick synchronization and for that purpose, cooperation with the cam shaft wheel, which has lower rotational stability than the flywheel, is sufficient.

[0057] In FIG. 3, 10 indicates an integral sensor unit including a carrier member 2 which carries a first sensor 3, a high precision sensor being an inductive sensor and a second sensor 4. The second sensor 4 is a low speed sensor which senses reference marks 9 on the flywheel 1 through the Hall effect or through magnetoresitive effect already at very low rotary speeds.

[0058] The integral sensor unit 10 is assembled in advance which means that the first and second sensors 3, 4 are preinstalled on the carrier member 2 while carefully attending to obtaining a determined distance between the first and the second sensors. The first 3 and second 4 sensors are connected to the control unit 100.

[0059] A separation 5 between the first sensor 3 and the second sensor 4 can be such that when the second sensor 4 faces a reference mark 9, the centre of the first sensor 3 is exactly between two adjacent reference marks. This way it is possible to obtain the better precision as if having one single sensor and the same number of reference marks.

[0060] It is also possible to position two sensors so as to simultaneously face and detect a reference mark.

[0061] The carrier member 2 is preferably bent or curved so as to as closely as possible adapt to a circumference of the flywheel 1, thereby allowing the sensors to come close to the flywheel 1.

[0062] In practice the integral sensor unit 10 can be precision mounted on a flywheel housing with a recess into which the integral sensor unit 10 can be inserted, possibly so as to be adjustable in a rotational direction of the flywheel.

[0063] The carrier member 2 can also be arranged to support more than two sensors for increase precision.

[0064] FIG. 4 illustrates the invention in connection with a four stroke internal combustion engine 11 having a flywheel 1 with reference marks 9 and the first 3 and second 4 sensors connected to the control unit 100.

[0065] FIG. 5 shows diagrammatically a vehicle 12 having a four stroke internal combustion engine 11 equipped according to the invention. 13 indicates a gear box and 14 a drive line.