DE10235533A1 - Drive belt system for IC engine with which single machine function as starter and generator has computer controlled tensioning pulley - Google Patents

Abstract

The drive belt (5) links a starter/generator pulley (3) with a crankshaft pulley (2). Tensioning pulley (4) is provided between the two. A tensioning lever (8) rotates about a pivot (10) driven by a rack (15) and computer controlled pinion (9). At the other end the lever has an arc-shaped profile (12) in contact with the tensioning roller so that as the lever pivots the distance between the point of contact and the roller varies, so adjusting the belt tension. An Independent claim is also included for method for tensioning it.

Description

The invention relates to a traction mechanism for an internal combustion engine and a method for tensioning a traction device in a traction mechanism according to the generic term the independent one Claims.

For vehicles with belt-driven starter generator it requires a traction means of the traction device in two directions of action for the motor and generator operation of the starter generator. In conventional Belt drives of alternators, the belt tensioner is usually in the empty section of the generator. This balances the strapless, caused and prevented by the generator operation of the generator such a belt slip. For However, the motor operation of the starter generator must be the resulting Leertrumm be stretched on the other side of the starter generator. It is known for this to provide double belt tensioners before and after the starter generator. This represents a compromise between the requirements for the regenerative and the motor operation, however, requires a permanent increased Belt tension, which leads to an increased load on all bearings in the belt drive leads.

From the DE 100 00 970 A1 a tensioner for a belt-driven starter generator is known. A starter generator and an internal combustion engine are frictionally connected via a drive. connected with each other. The traction means of the drive is for example a chain or a belt. In the tensioning device, with which the tension of the drive is adjusted, a pivot-mounted tensioner arm is provided on which a first, the belt under bias deflecting tension roller is arranged. In addition, a second tension roller is provided which has a shorter lever arm than the first tension roller. The belt is deflected at the two tension rollers in such a way that the resultant of the deflection forces result in a pair of opposing torque pairs with respect to the pivot bearing. With a stronger application of a tension roller, the other tension roller is pressed with increasing force in the belt.

It is an object of the invention to provide a Specify clamping device and arrange so that an optimal Tension of the traction device for the operation of a starter generator is guaranteed.

According to the invention the object is in a device by the features of claim 1 and by a method the features of claim 5 solved.

It is about an actively adjustable Preload gear achieved that set a Zugmittelvorspannung that can be transferred Moments are adapted especially in critical operating points.

The special advantage of this is that in a so-called start-stop operation of the internal combustion engine the moment required to crank the engine only must be applied for a limited period of time. This will wear the traction device as well as the bearing load reduced. The active control allows a needs-based variation of the belt tension.

There are no permanently increased bearing forces. The Traction means voltage is only increased in the starting case of the internal combustion engine. In generator mode There are no disadvantages, since the belt tension is carried out as before can. The traction mechanism can be diagnosed and actively influenced become.

Further embodiments and advantages The invention is the description and the other claims to remove.

The invention is based on the following a drawing closer describe.

Showing:

1 an arrangement of pulleys and pulleys in a drive with an additional tensioner arm according to the invention,

2 the positioning of the tensioner arm when stopping and running the internal combustion engine (a) and when starting the internal combustion engine (b) and

3 example activation times of the actuator at different operating conditions of the internal combustion engine.

In 1 an arrangement of Zugmittelscheiben and pulleys is shown in a drive. A traction mechanism 1 an internal combustion engine, not shown, has a plurality of traction pulleys, which via a traction means 5 , preferably a belt, are in frictional connection with each other.

A first pulley 2 a crankshaft, not shown, is provided with a biasing roller 4 a biasing device connected. The biasing means includes the biasing roller 4 , a tensioner arm 8th and a drive roller 9 for the tensioner arm 8th , and an electric actuator for driving the drive roller 9 , The electrical actuator is controlled by a control unit, not shown, depending on operating parameters of the vehicle. The first pulley 2 is with a second pulley 3 connected to a starter generator, not shown. The Zugmit tel 5 via a pulley 7 be guided. Subsequently to the second pulley 3 is a third pulley 6 arranged. Furthermore, further Zugmittelscheiben can be arranged, which by the traction means 5 are assigned to be driven aggregates. From the first pulley 2 and the third pulley 6 lead the first end and the second end of the traction device 5 to any other units, not shown, or pulleys.

By a rotation of the first pulley 2 Thus, all other traction pulleys and the traction pulleys, not shown further aggregates are set in rotation. In this case, the starter generator operates in generator mode. In starter mode of the starter generator offset the rotation of the second pulley 3 all other traction pulleys and the traction pulleys, not shown further aggregates and in particular the crankshaft in rotation.

According to the invention, a preferably electromotive driven tensioner arm 8th when stopping the internal combustion engine, the biasing roller 4 started and suppressed when starting the engine. This will be the traction means 5 strained in the train. In normal regenerative operation with the engine running, the tensioner arm 8th extended, so that in this state, the tensioning of the traction means can be carried out in the usual manner.

The tensioner arm 8th the pretensioner has a head part 11 and a foot part 14 on. The tensioner arm 8th is about a pivot axis 10 floating. The foot part 14 the lever arm 8th stands with a contact surface 15 in operative connection with a drive wheel 9 , The drive wheel 9 is preferably a gear and contact surface 15 preferably a sprocket segment. The drive wheel 9 is preferably driven by an electric actuator, not shown, preferably in dependence on the operating state of the internal combustion engine. By turning the drive wheel 9 becomes the tensioner arm 8th around the fulcrum 10 pivoted.

The headboard 11 the tensioner arm 8th is designed in such a way that it has a variable effective length. The upper part of the tensioner arm 8th is approximately wedge-shaped, with an oblique or curved guide surface 13 is provided. Virtually every point on the guide surface 13 has a different distance to the pivot axis 10 on, resulting in a variable effective length R of the tensioner arm 8th along the longitudinal extent of the contact surface 13 results. Will the tensioner arm 8th so far swung to the right that he is just at the Vorspannrolle 4 , preferably at the contact surface 16 , comes to a concern in a contact point, the distance to the pivot axis 10 a first length R1. This length R1 corresponds to the effective length of the tensioner arm 8th in this pivot position. The tensioner arm 8th does not exert any force on the preload roller here 4 out. Will the tensioner arm 8th however, further pivoted to the right, the effective length R of the tensioner arm decreases 8th to. Due to the increasing length of the tensioner arm 8th becomes the preload roll 4 pushed upward, causing the tension of the traction device 5 elevated. In the area 12 the guide surface 13 points the tensioner arm 8th the largest effective length R on. Will the tensioner arm 8th swung back to the left, shortens the effective length of the tensioner arm 8th and the tension means decreases again.

Preferably, the material is in the region of the guide surface 13 particularly hard or provided with a hardened support, so that the least possible abrasion when applying the tensioner arm 8th to the leader roll 4 arises. The guide surface may also be coated with a corresponding sliding coating to reduce abrasion.

An advantage is that the tensioner arm 8th can be used as an additional tensioning device with a conventional series belt tensioner.

The position of the tensioner arm 8th in 1 corresponds to the normal operating state of the internal combustion engine, in which the starter generator is driven by the internal combustion engine and operates as a generator. The tensioner arm 8th is disengaged and is not at the Vorspannrolle 4 on. In regenerative operation, therefore, no additional belt or bearing forces arise.

In 2a is the preferred positioning of the tensioner arm 8th when stopping and running the engine and in 2 B when starting the internal combustion engine shown.

When stopping and / or leakage of the internal combustion engine, the tensioner arm is almost force-free to the biasing roller 4 or the contact surface 16 created. Thus, the time can be reduced to reach the maximum tension mean stress in the starting process of the internal combustion engine. With the towing of the internal combustion engine is the tensioner arm 8th activated and by turning the drive wheel 9 overpressed until the tensioner arm 8th with the maximum effective length against the pretensioning roller 4 pushes and the traction means 5 is stretched maximum. When the engine is started, the tensioner arm becomes 8th according to his position 1 disengaged.

In 3 is exemplified the actuator current as a function of time. The actuator moves directly or indirectly the tensioner arm 8th depending on the operating state of the internal combustion engine. Thus, when stopping or running out of the internal combustion engine within 250 msec of the tensioner arm 8th to the leader roll 4 be created where it remains virtually free of force until the internal combustion engine is started. In the graph, the state corresponds to the time range of 0 to about 250 msec. To start the internal combustion engine, the actuator is activated for example 100 msec and the tensioner arm 8th About suppressed. The starter generator now acts as an electric motor and can with the by pressing the tensioner arm 8th increased Zugmit telspannung the internal combustion machine via the traction means 5 start. In the graph, this corresponds to the range of approximately 250 msec to 350 msec, in which the actuator current points approximately at a plateau. After the start of the engine, the tensioner arm 8th brought into his disengaged position and held there. The starter generator is then in generator mode and is driven by the internal combustion engine. This corresponds in the diagram to the range from about 350 msec.

The device according to the invention allows the operation of the internal combustion engine in the so-called start-stop operation by means of a belt-driven starter generator. The different per se requirements of the electric machine as a starter of the internal combustion engine and as a generator for the electrical system of the vehicle can be met in this way with little effort. The influence of the outside temperature the traction means 5 and / or elasticity differences between different traction means 5 and / or pressure differences can be compensated automatically when the tension of the traction means required for starting the internal combustion engine 5 is adjusted according to the invention via the actuator current.

Furthermore, the active operation of the tensioner arm 8th be used very particularly advantageous for the diagnosis of the condition of belt tensioners and / or the actuator itself.

By monitoring the Aktorstromes, preferably by means of a control unit, In particular, the failure of the actuator can be detected. Of the Failure can be indicated by an alarm signal.

Likewise, a failure of the traction device 5 be recognized. When overpressing the tensioner arm 8th the actuator current is at least approximately a measure of the force with which the traction means 5 is tense. This temporal operating range is hereinafter referred to as "pressure range" to indicate that then the tensioner arm 8th to the leader roll 4 or the contact surface 16 created and pressed under the exercise of force. This corresponds to the example in 3 the time range between 250 and 350 msec, in which the course of the Aktorstroms essentially shows a plateau.

Will the traction means 5 maximum tension, the actuator current I is high in the pressure range and assumes a mean maximum value I _max , the traction means 5 less tensioned, the actuator current is less than the maximum value I _max . In case of breakage of the traction device 5 the Aktorstrom in the Andrückbereich is much lower than in normal operation.

Accordingly, by measuring the Aktorstroms also a temporal change in the properties of the traction device 5 be easily recognized. Starting from an actuator current I ₀ , which is intended to characterize a normal operation with normal belt tension under normal operating conditions, a change in the traction means can result from a change in the actuator current value in the pressure range 5 be recognized. Conveniently, for this purpose, the Aktorstromwert is averaged in this area to obtain a reliable reference value.

The exact position of the tensioner arm is particularly preferred by means of a position sensor, not shown 8th preferably registered in the pressure range and compared with the associated actuator current. This can cause aging of the traction device 5 be recognized when, for example, a long-term Zugmittel-elongation occurs. For the same positioning of the tensioner arm 8th the average actuator current decreases in the pressure range over longer periods of time when the traction means 5 gets longer. This allows an impending slippage of the traction means 5 to recognize in time and eg via an alarm signal.

The specification of the Aktorstroms and thus the active adjustment of the traction means voltage also makes it possible to set a relatively low tension mean, which is just sufficient for the reliable start of the engine. In this case, an actuator current is set, which is less than the maximum value of the actuator current at maximum tension mean voltage, but still reliably fires the internal combustion engine. This avoids that the traction means 5 to start the internal combustion engine must always be stretched maximum, which is beneficial to the life of the traction device 5 and the other components of the tensioning device. Likewise, a favorable traction means voltage can be adjusted approximately as a function of the engine oil temperature and so the traction means for the cold start and the warm start can be adjusted.

Claims (17)

Traction mechanism ( 1 ) an internal combustion engine with a rst pulley ( 2 ) on a crankshaft, a second pulley ( 3 ) a starter-generator unit and a biasing device with a biasing roller ( 4 ), wherein the first pulley ( 2 ), the second pulley ( 3 ) and the pretensioning roller ( 4 ) via a traction means ( 5 ), characterized in that a tensioner arm ( 8th ) is provided, which is pivotally mounted and has a dependent on the pivot position effective length. Apparatus according to claim 1, characterized in that the tensioner arm ( 8th ) is connected to an electrical actuator, the tensioner arm ( 8th ) is positioned depending on the operating state of the internal combustion engine. Apparatus according to claim 1, characterized in that the tensioner arm ( 8th ) at the power transmission to the pretensioning roller ( 4 ) Headboard ( 11 ) is approximately wedge-shaped and an inclined or curved guide surface ( 13 ), along which the contact point with the biasing roller ( 4 ) is feasible. Apparatus according to claim 3, characterized in that the tensioner arm ( 8th ) along the guide surface ( 13 ) has an abrasion-reducing coating. Apparatus according to claim 3, characterized in that a position sensor for detecting the position of the tensioner arm ( 8th ) is provided. Method for tensioning a traction device ( 5 ) by means of a biasing device in a traction mechanism ( 1 ) of an internal combustion engine according to one of the preceding claims, characterized in that a tensioner arm ( 8th ) is controlled such that it assumes a dependent on the operating condition of the internal combustion engine position. A method according to claim 6, characterized in that an actuator, the tensioner arm ( 8th ). Method according to claim 6, characterized in that the effective length of the tensioner arm ( 8th ) is changed depending on the operating state of the internal combustion engine. Method according to claim 6, characterized in that the effective length of the tensioner arm ( 8th ) depending on the aging state of the traction device ( 5 ) is changed. Method according to claim 6, characterized in that the tensioner arm ( 8th ) is suppressed to start the Brennkraftmaschi ne, so that he has the greatest effective length against the biasing roller ( 4 ) presses. Method according to claim 6, characterized in that the tensioner arm ( 8th ) is disengaged during generator operation of the starter generator. Method according to claim 6, characterized in that the tensioner arm ( 8th ) when stopping or running out of the internal combustion engine almost force-free to the biasing roller ( 4 ) is created. Method according to claim 6, characterized in that the traction means ( 5 ) is tensioned in response to an electric current of the actuator. A method according to claim 13, characterized in that the Aktorstrom at least in the phase in which the tensioner arm ( 8th ) the traction means ( 5 ), is monitored. A method according to claim 13, characterized in that a positioning of the tensioner arm ( 8th ) in the phase in which the tensioner arm ( 8th ) the traction means ( 5 ), is compared with the actuator current. A method according to claim 15, characterized in that at the same positioning of the tensioner arm ( 8th ) in the phase in which the tensioner arm ( 8th ) the traction means ( 5 ) and an impending belt slippage is detected over longer operating times of sinking actuator current. A method according to claim 13, characterized in that the actuator current in the phase in which the tensioner arm ( 8th ) the traction means ( 5 ), is set to a value below a maximum possible Aktorstromwertes, so that the traction means voltage is sufficient to start the internal combustion engine.