SE539269C2 - Method for controlling a viscous coupling, a coupling deviceand a vehicule including such a coupling device - Google Patents

Description

METHOD FOR CONTROLLING A VISCOUS COUPLING, A COUPLING DEVICE AND A VEHICLE INCLUDING SUCH A COUPLING DEVICE FIELD OF THE INVENTION The invention relates to a method of controlling a viscous coupling which includes a first rotational part to be connected to a combustion engine and a second rotational part to be connected to a driven element, wherein an operating chamber is defined between the first and the second rotational parts, said method including actuating an opening valve or valves (16) of the operating chamber for: i) supplying viscous fluid to the operating chamber for obtaining a state of engagement of the viscous coupling, and ii) evacuating viscous fluid from the operating chamber for obtaining a state of disengagement of the viscous coupling. The invention also relates to a corresponding device and a vehicle being equipped with such a device.

BACKGROUND OF THE INVENTION Fans for heavy vehicles such as trucks and busses are often controlled with the aid of viscous couplings. Such couplings basically are comprised of two rotating discs whereof one is connected to the combustion engine and the other one is driven by the first disc over an operating chamber which is supplied with or evacuated from oil. Torque delivered to the fan depends on the relative amount of oil currently being present in the operating chamber.

Control of supply of oil to the operating chamber is accomplished by regulating a valve that allows oils to enter between the discs into the operating chamber or to close supply of oil to the operating chamber. In order to avoid control problems, the valve is typically normally open and closes upon actuation of the valve actively by supplying current to a solenoid. The reason for this is to ensure that the fan is fully operative in case of electric failure.

This results in that after engine stop, at occurrences, viscous oil flows from the oil reservoir through the open valve and finds its way to the operating chamber. The result is that the fan will be active directly when the combustion engine is started again. This is a disadvantage which is often referred to as "morning sickness" since the immediately activated fan causes vibrations and noise which is experienced as a comfort problem for the driver. It is also unwanted since it results in energy loss of the magnitude of typically about 7kW for a number of minutes.

Attempts have been made to reduce morning sickness but such solutions have so far been complicated and costly. As examples of the background art can be mentioned US 5,152,383 and US 6,085,881.

AIM AND MOST IMPORTANT FEATURES OF THE INVENTION It is an aim with the present invention to address and at least reduce the above problems. This aim is obtained in respect of the above indicated method in that a representation of a rotational position of an opening valve or valves of the operating chamber is detected after turn-off of the combustion engine, and that a shaft of the combustion engine is rotated to a rotational position where the opening valve or valves is/are above a predetermined level.

The term "after turn-off of the combustion engine" means that the combustion engine has stopped or is in the process of stopping.

Hereby is achieved that oil being present in an oil reservoir up to an oil level being safely below the predetermined level will not have any possibility to flow into the operating chamber and cause the problems indicated above. The inventive solution is simple to realize and it does not require additional components to be installed. The solution is therefore economic and secure.

In particular, the position of the valve or valves as detected is signaled to a control arrangement that has an evaluating means that evaluates whether the valve or valves are below a level where there is a risk for oil present in the oil reservoir to leak into the operating chamber. If the evaluation results in that the valve or valves are indeed below said level, it is initiated to rotate the combustion engine to a rotational position where the opening valve or valves is/are above said level.

There are different ways of detecting a representation of the rotational position of the valve or valves. Firstly, with "a representation of the rotational position of the valve or valves" is meant that typically, the position is detected indirectly. One way is to use the normal position indications on the flywheel together with the normal corresponding flywheel sensor or sensors for obtaining the coupling position. Another way is to provide a sensor besides the viscous coupling which has been provided with one or more indicators and to signal to the control unit for further action.

Preferably, the method is supplemented with a step of verifying that the valve/valves is/are in the desired position. This can be made in different ways and in case it is established that the rotation has failed to position the valve or valves as required, the system can initiate a further attempt.

It is preferred that, in order to rotate the crankshaft, an engine starter motor is initiated to rotate an engine flywheel. In case of a hybrid vehicle, the hybrid electric motor is intended to function as a starter motor in this respect.

Advantageously, the operating chamber is evacuated at engine turn-off. Herby the operating camber has been made free from any remaining oil even in case the fan was operative when the driver stops the engine.

Preferably a crankshaft of the combustion engine is rotated to a rotational position where also a return channel from the operating chamber is above the predetermined level. Hereby is avoided also that oil leaks into the operating chamber through the return channel.

The invention also relates to a coupling device which includes a first rotational part to be connected to a combustion engine and a second rotational part to be connected to a driven element, wherein an operating chamber is defined between the first and the second rotational parts, said device including means for actuating an opening valve or valves of the operating chamber: i) for supplying viscous fluid to the operating chamber for obtaining a state of engagement of the viscous coupling, ii) for evacuating viscous fluid from the operating chamber for obtaining a state of disengagement of the viscous coupling.

The inventive device is distinguished by a control unit including: sensor means capable of detecting a representation of a rotational position of an opening valve or valves of the operating chamber after turn-off of the combustion engine, and means arranged to initiate rotation of a crankshaft of the combustion engine to a rotational position where the opening valve or valves is/are above a predetermined level, starting out from said detected representation.

It is preferred that the valve or valves is/are maintained closed until the coupling has been rotated to position the valve or valves above the predetermined level. This can be ensured by maintaining current supply to hold the valve or valves until the said rotation is completed.

In order to rotate the crankshaft, preferably an engine starter motor is arranged to be initiated to rotate an engine flywheel. At occasions, a hybrid electric motor can be arranged to fulfill the same function.

Also preferably the operating chamber is arranged to be evacuated at engine turn-off.

Further features and advantages will be explained in the following detailed description.

BRIEF DESCRIPTION OF DRAWINGS The invention will now be explained by way of embodiments and with reference to the annexed drawings, wherein: Fig. 1 diagrammatically illustrates a vehicle with an engine equipped with a viscous coupling unit according to the invention, Fig. 2 shows an axial section through a viscous coupling unit according to the invention, Figs. 3 and 4 diagrammatically illustrate the function of the invention in respect of two embodiments, and Fig. 5 shows a simplified flow chart over a method sequence according to the invention.

DESCRIPTION OF EMBODIMENTS Fig. 1 indicates with interrupted lines a vehicle 1, said vehicle including an engine 2 having an outgoing shaft being connected to a viscous coupling unit 6, which transmits rotational power to a fan 4 assisting in creating an air flow through a radiator 3. A crankshaft 27 of the engine is connected to a flywheel which, as usual, has position indications co-operating with a flywheel sensor SI. A starter motor for engagement with a (not shown) flywheel of the engine 2 is denoted reference number 7. CU indicates a control unit which preferably is part of a control system of the vehicle 1.

The viscous coupling unit 6 in Fig. 2 is driven through an input shaft 8 having an axis A and being connectable to an outgoing shaft of the combustion engine over a flange 8'.

The input shaft 8 transmits rotation to a disc-shaped first rotational part 9 which together with a second rotational part 10 form an intermediate operating chamber 14.

The second rotational part 10 further includes a housing for the complete viscous coupling unit 6 said housing containing i.a. an oil reservoir 15 and also housing parts enclosing the first rotational part 9.

A fan 4 is bolted to the second rotational part 10 and is arranged to rotate in a state of engagement of the viscous coupling. In a state of disengagement of the viscous coupling, the fan is rotating at idle speed which typically is about 100 rpm.

The first rotational part 9 is at its side facing the second rotational part provided with a first group of annual protrusions 12, said annular protrusions forming between them a plurality of ring-shaped grooves.

The second rotational part 10 forms a second group of annual protrusions 13 which fit into the grooves formed by the first group of annular protrusions in such a way that there are no contacts between the first and second groups of annular protrusions. In fact the space formed forms a meandering structure as seen in the axial section.

The formed operating chamber 14 between the first and second groups of annular protrusions comprises a shear space whereinto oil is supplied or wherefrom oil is evacuated. When oil is present in the operating chamber, rotation of the first rotational part causes the second rotational part to rotate through friction forces being transmitted in the operating chamber. Hereby the second rotational part will follow the first rotational part in rotation. 15 indicates an oil reservoir from where oil can be supplied to the operating chamber 14. Between the oil reservoir 15 and the operating chamber 14 there is a valve 16 which is normally open and thereby allows a flow of oil from the oil reservoir 15 to the operating chamber 14.

The valve 16 can, however, be controlled and actuated by a solenoid (not shown) so as to close the path between the oil reservoir 15 and the operating chamber 14. The closed condition of the valve 16 is shown in Fig. 2 with the valve member indicated with 16' and shown in uninterrupted lines. In that condition, oil being present in the operating chamber 14 will be evacuated through centrifugal force and be subsequently led back to the oil reservoir 15 through pumping action effected by the relative speed difference between the rotating members. The valve 16 can be operated in different ways for example through electromagnetic force or through any other per se known method.

The open condition of the valve 16 is shown in Fig. 2 with the valve member shown in interrupted lines and indicated with 16 ' ' .

It has been discovered that morning sickness occurs because the valve 16 has been left in a position where it is below an oil level 18 of the oil reservoir 15 when the combustion engine is shut off. This results in that oil in the oil reservoir 15 can easily find its way into the operating chamber 14 which is thereby in the state of engagement of the viscous coupling. This results in unwanted coupling engagement and thereby fan operation already at engine start which, as is explained above, results i.a. in noise and unnecessary energy consumption.

According to the invention it is arranged that the engine, at shut down, is rotated in order to position the valve 16 above the liquid level 18 of oil in the oil reservoir 15 thereby preventing oil from entering into the operating chamber 14 when the vehicle is stopped and the engine is finally shut off and is in the process of stopping.

A sensor S2 is used in a variant of the invention for detecting rotational position of the viscous coupling unit.

In Fig. 3 there is shown diagrammatically a viscous coupling unit 6 with a valve 16 being above the liquid level 18. Furthermore, also the return channel 17 has been arranged to be positioned above the liquid level 18, since it is possible for oil to find its way from the oil reservoir to the operating chamber also through the return channel 17.

In Fig. 4 another embodiment is shown where the viscous coupling unit includes two valves 16 which are positioned diametrically opposite each other. In this case according to the invention it is ensured that both valves 16 are positioned above the oil level 18 through rotation of the combustion engine crankshaft at vehicle stop.

Also in the embodiment where the viscous coupling unit has two valves 16 the return channel 17 can be positioned so as to extend above the oil level 18.

In order to accomplish rotation of the engine it is preferred that the engine starter motor 7 in Fig. 1 is initiated so as to rotate the crank shaft and thereby the shaft that drives the first rotational part is rotated correspondingly.

Fig. 5 illustrates a method sequence wherein: position 20 indicates start of the sequence, position 21 indicates actuating an opening valve or valves of the operating chamber for supplying viscous fluid to the operating chamber for obtaining a state of engagement, position 22 indicates actuating the opening valve or valves for evacuating viscous fluid from the operating chamber for obtaining a state of disengagement, position 23 indicates detecting a representation of a rotational position of the valve or valves of the operating chamber is when the combustion engine is in the process of stopping, position 24 indicates that a crankshaft of the combustion engine is rotated to a rotational position where the opening valve or valves is/are above a predetermined level, position 25 indicates verifying that the valve/valves is/are in the desired position and thereupon releasing the valve or valves into open position, position 26 indicates the end of the sequence.

The sequence can be modified and steps be repeated as required.

The invention can be modified within the scope of the invention and a viscous coupling unit according to the invention is applicable also for other components than fans. For example it is fully possible to arrange an inventive coupling unit in respect of a water pump of the vehicle.

The position of the part of the viscous coupling unit including the valve can be detected directly of by detecting rotation for example the flywheel position of the engine in case there is a direct coupling between these members.

The invention is described at the background of road vehicle combustion engines. It is, however, also applicable in respect of stationary combustion engines, combustion engines for ships etc.

Claims (12)

1. Method of controlling a viscous coupling (6) which includes a first rotational part (9) to be driven by a combustion engine and a second rotational part (10) to be connected to a driven element (4), wherein an operating chamber (14) is defined between the first and the second rotational parts, said method including actuating an opening valve or valves (16) of the operating chamber for: i) supplying viscous fluid to the operating chamber (14) for obtaining a state of engagement of the viscous coupling, or ii) evacuating viscous fluid from the operating chamber for obtaining a state of disengagement of the viscous coupling, characterized in - that a representation of a rotational position of the valve or valves (16) of the operating chamber is detected after turn-off of the combustion engine, and - that a crankshaft (27) of the combustion engine is rotated to a rotational position where the opening valve or valves (16) is/are above a predetermined level (18).

2. Method according to claim 1, characterized in that the crankshaft (27) of the combustion engine is rotated to a rotational position where also a return channel (17) from the operating chamber (15) is above the predetermined level.

3. Method according to claim 1 or 2, characterized in that the operating chamber (14) is evacuated at engine turn-off.

4. Method according to any one of claims 1-3, characterized in that in order to rotate the crankshaft, an engine starter motor (7) is initiated to rotate an engine flywheel.

5. Method according to any one of claims 1-3, characterized in that the crankshaft is rotated to a rotational position where the opening valve or valves (16) is/are above a predetermined level by a motor.

6. Method according to any one of claims 1-5, characterized by the step of verifying that the valve/valves is/are in the desired position.

7. Method according to claim 6, characterized by the step of initiating a further attempt in case it is established that the rotation has failed to position the valve or valves as required.

8. Coupling device which includes a first rotational part (9) to be connected to a combustion engine and a second rotational part (10) to be connected to a driven element (4), wherein an operating chamber (14) is defined between the first and the second rotational parts, said device including means for actuating an opening valve or valves (16) of the operating chamber: i) for supplying viscous fluid to the operating chamber (14) for obtaining a state of engagement of the viscous coupling, or ii) for evacuating viscous fluid from the operating chamber (14) for obtaining a state of disengagement of the viscous coupling, characterized by a control arrangement (CU) including: - sensor means (S1;S2) capable of detecting a representation of a rotational position the valve or valves (16) after turn-off of the combustion engine, and - means arranged to initiate rotation of a crankshaft (27) of the combustion engine to a rotational position where the valve or valves (16) is/are above a predetermined level (18).

9. Device according to claim 8, characterized in that in order to rotate the crankshaft, an engine starter motor (7) is arranged to be initiated to rotate an engine flywheel.

10. Device according to claim 8 or 9, characterized in that it is arranged to evacuate the operating chamber (14) at engine turn-off.

11. Device according to claim 8, 9 or 10, characterized in that it is connected to any one from the group: a fan and a water pump.

12. Vehicle with an internal combustion engine, characterized in that it includes a device according to any one of claims 8 - 11.