WO2003071099A1

WO2003071099A1 - Device for detachably connecting and displacing two shafts that can be displaced in relation to one another with regard to the rotation angles thereof

Info

Publication number: WO2003071099A1
Application number: PCT/EP2003/000956
Authority: WO
Inventors: Jens Schäfer; Martin Steigerwald
Original assignee: Ina-Schaeffler Kg
Priority date: 2002-02-23
Filing date: 2003-01-31
Publication date: 2003-08-28
Also published as: DE10207760B4; DE10207760A1; AU2003206807A1

Abstract

The invention relates to a device for detachably connecting and displacing the crankshaft and the camshaft (1) of an internal combustion engine, comprising a setting gearing (2), which is constructed as a three-shaft gearing and has a crankshaft-connected input shaft (3), a camshaft-connected output shaft (5), and a setting motor (6, 7) that rotates therewith. The rotor (8) of the setting motor is connected in a fixed manner to a setting shaft (9) of the setting gearing (2), and the stator (10) of the setting motor is connected in a fixed manner to the input shaft (3). The electric power consumption, when maintaining and setting control positions of the camshaft (1), is minimized in that the torque balance of the three shafts (3, 5, 9), which is necessary for fixing a control position of the camshaft (1), or their synchronous speed are achieved by coupling the input shaft (3) and the setting shaft (9), preferably via a holding torque of the setting motor (6, 7) in conjunction with a multiplication ratio, which converts the camshaft torque to the level of the holding torque, between the output shaft (5) and the setting shaft (9) of a low-friction three-shaft gearing.

Description

Name of the invention

Device for releasably connecting and adjusting two shafts that can be rotated relative to one another

Field of the Invention

The invention relates to a device for releasably connecting and adjusting two shafts that can be rotated relative to one another, in particular according to the preamble of claim 1.

Background of the Invention

In modern high-performance engines, the control times of the gas exchange valves improve consumption, emissions and performance over the entire load and speed range. A camshaft adjuster is used for this. This fixes the angular position of the camshaft relative to the crankshaft during approximately 90% of the engine's operating time in certain positions, the so-called control positions, and changes the same during only about 10% of the operating time.

Camshaft adjustment systems with an electric adjustment motor have the potential for high adjustment speed and control accuracy, which is why they are attracting increasing interest. If the respective control position is fixed via the holding torque of the adjustment motor, this requires a considerable amount of electrical energy. This puts a strain on the vehicle's electrical system and means energy loss. The control positions of the camshaft can also be fixed by a self-locking or self-braking adjustment gear. In this way, the high power consumption in regulated operation is eliminated by eliminating the holding torque of the servomotor.

In this case, however, there is the problem of high mechanical

Design compared to one without self-locking has a mechanical efficiency reduced by about half.

Despite these high friction losses, it is difficult to achieve the torque balance required for the control position by self-locking due to the strong impulsive torque of the camshaft. This applies all the more if the gear toothing has torsional backlash, which also increases with the operating time due to wear of the adjusting gear.

Object of the invention

The invention has for its object to provide an electric motor adjustable camshaft adjuster, in which the control position of the camshaft can be fixed and adjusted with little electrical energy expenditure.

Summary of the invention

The object is achieved by the features of claim 1. The ratio of the holding torque to the camshaft torque between the adjusting and output or camshaft enables a torque balance between the three shafts of the adjusting gear and thus synchronism of the same even with a low holding torque. Despite the lack of self-locking of the adjustment gear, this enables a low energy expenditure for coupling the rotor and stator of the adjustment motor. Due to the low friction in the adjustment gear, the electrical energy consumption when adjusting it is also low.

Torque balance and synchronism of the three shafts also increase the torsional rigidity of the camshaft drive in the normal position of the camshaft and thus reduce its angular vibrations.

The reduced power consumption allows the servomotor and the power supply to be reduced in size and increases their service life by lowering the heat load.

As three-shaft gearboxes come e.g. B. planetary or eccentric gear in question. Instead of an electric adjustment motor, a hydraulic or pneumatic actuator is basically also conceivable.

An advantageous embodiment of the invention is that the adjustment motor is a permanent magnet adjustment motor or an externally excited adjustment motor. Permanent magnet adjustment motors are DC motors that generate a self-holding torque when de-energized, which rises to a maximum in both directions of rotation from a center position and then drops again.

Externally excited adjusting motors are DC motors that do not have a holding torque inherently. This only forms when current is applied to them. While the self-holding torque of the permanent magnet adjustment motor is a passive one that acts in both directions of rotation, the holding torque of the externally excited adjustment motor is an active one that only acts in one direction of rotation. This leads to increased torsional vibrations of the camshaft at camshaft torques with zero crossings. These are to be compensated with a corresponding construction effort by rapidly reversing the polarity of the excitation current in time with the zero crossings. The same effect also acts when the self-holding torque of the permanent magnet variable motor is increased by energizing it. However, there is no need to reverse the polarity of the excitation current since the self-holding torque has a stabilizing effect. Through the use of permanent magnets, the material of which contains rare earths, an increased magnetic force and thus a correspondingly increased self-holding torque are achieved. Comes as a servomotor

If the self-holding torque of a permanent magnet adjustment motor is greater than the torque required to adjust the camshaft (e.g. at low camshaft speeds), the adjustment can only take place when the electrical torque is greater than the self-holding torque. This leads to the fact that after its maximum is exceeded, the rate of adjustment becomes very high with the subsequent drop and an adjustment with low speed and small control jumps is hardly possible. These difficulties are avoided by the control motor being subjected to short current pulses in the control position, which can be varied in height, frequency and direction and thus enable a gradual adjustment in both directions of adjustment.

The increase in the holding torque by means of a braking device offers the advantage that the braking torque, similar to the frictional moments, is a passive one that is effective in both directions of rotation. In addition, the structure of the braking devices is comparatively simple and inexpensive.

Because the braking device can be implemented with mechanical, electromagnetic, hydraulic or pneumatic actuation and control, it can be adapted to the prevailing boundary conditions.

A particularly simple embodiment of the braking device consists in that it is designed as a spring-loaded brake and is attached to or in the adjusting motor. is ordered and automatically intervenes when it is almost de-energized.

The power of the servomotor is designed in such a way that when the camshaft is adjusted early, it can be adjusted from 30 ° to 80 ° cam angle per second.

As a result of the fact that the adjusting motor can be designed as an outer, intermediate or inner rotor motor with a roller or disc rotor and that the rotor and the stator are interchangeable, there is great flexibility in the design of the device.

Brief description of the drawing

Further features of the invention will become apparent from the following description and the drawing, in which an embodiment of the invention is shown schematically. The single figure shows a cross section through the device according to the invention with a braking device but without a control unit.

Detailed description of the drawing

The device according to the invention serves for releasably connecting and adjusting the crankshaft (not shown) and camshaft 1, which can be rotated relative to one another, by means of an adjusting gear 2 designed as a three-shaft gearbox. This has a drive shaft 3 connected to the crankshaft with a camshaft drive wheel 4 driven by the crankshaft via chain, toothed belt or gearwheel and a camshaft-connected output shaft 5 and a co-rotating electrical adjustment motor 6, 7. Its rotor 8 is fixedly connected to an adjusting shaft 9 of the adjusting gear 2 and its stator 10 to the drive shaft 3 and a gear housing 11. The camshaft is fixed in so-called control positions in approx. 90% of the operating time of the internal combustion engine and is only adjusted in approx. 10% of the operating time. The fixing of a control position is achieved by a torque balance of the three shafts 3, 5, 9 or by their synchronism. For this purpose, the drive shaft 3 is coupled to the adjusting shaft 9 via a holding torque of the adjusting motor 6, 7 and / or via the frictional torque of a braking device

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Adjusting motors 6, which have a permanent magnet rotor (e.g. a permanent magnet direct current motor) or a permanent magnet in the stator (magnetically excited direct current motor), generate a self-holding or cogging torque. The self-holding torque is the maximum torque with which a non-energized adjustment motor 6 can be statically loaded on its drive shaft 9 when the stator 10 is held in place, without causing a non-uniform but continuous rotation.

Actuators that are constructed without permanent magnets (e.g. reluctance motors without slip rings or externally excited actuators 7) have almost no self-holding torque. They only generate a holding torque when excited. The holding torque is the maximum torque with which one can statically load an excited adjusting motor 7 without causing a continuous rotation.

When the camshaft 1 rotates, the camshaft torque converted via the adjustment gear 2 acts on the rotor shaft of the adjustment motor 6, 7. In order to fix the camshaft and crankshaft positions to each other, there must be no relative movement between the three gear shafts 3, 5, 9, that is, the three shafts must rotate at the same speed. This means that there must also be no relative movement between the rotor 8 and the stator 10 of the adjusting motor 6, 7. There are different ways to fix the three gear shafts 3, 5, 9 to each other. If the self-holding torque of the servomotor 6 with permanent magnets is greater than the converted camshaft torque, there is only a relative movement between the stator 10 and the rotor 8 of the servomotor 6 until the moment equilibrium position with a small amplitude is reached.

is connected, the rotor 8 of the adjusting motor 6 and thus the adjusting shaft 9 has the same speed as the camshaft drive wheel 4. In this case, the camshaft 1 also rotates with the speed of the camshaft driving wheel 4, that is to say that none occurs when the adjusting motor 6 is deenergized Adjustment between camshaft 1 and crankshaft instead.

Adjustment motors 7 that do not have permanent magnets must be excited to generate a holding torque, that is to say that current must flow through them. If the holding torque generated in this way is equal to the converted camshaft torque, there is no relative movement between the rotor 8 and the stator 10 of the adjusting motor 7 in this case too. The camshaft drive wheel 4, adjusting shaft 9 and camshaft 1 thus rotate at the same speed, which means that the camshaft 1 and the crankshaft are not rotated relative to one another.

An electromagnetically generated holding torque can only compensate for a converted camshaft torque that does not have a zero crossing (change of direction), or a converted friction torque without large oscillation angle amplitudes. At moments with zero crossings, the excitation current would have to be varied quickly and appropriately in size and direction in order to achieve a similar one To achieve the same effect as with a self-holding moment.

In principle, the position of the rotor 8 can also be maintained on average in the case of a camshaft moment with zero crossing with current flowing in one direction. between rotor 8 and stator 10. By contrast, self-holding torques generated by permanent magnets can compensate camshaft torques with and without zero crossing without large oscillation angle amplitudes.

5 If the converted camshaft torque exceeds the self-holding torque of an adjusting motor 6 with a permanent magnet, the rotor 8 is re-

Camshaft 1 and crankshaft instead.

10 In this case, in order to fix the camshaft 1 and the crankshaft to one another, as explained above, an additional torque must be applied either electromagnetically by energizing the adjusting motor 6 or / and externally, for example by means of a mechanical braking device 12.

15 In the case of an externally excited adjusting motor 7, the motor must be supplied with a correspondingly higher current in order to increase the holding torque, which leads to increased thermal stress, or an external torque, for example a braking torque, must be applied.

20 Likewise, with camshaft adjusters in which camshaft 1 and. Crankshaft mainly due to an external moment, e.g. B. fixed by the braking device 12 to each other, an additional holding torque can be applied by energizing the adjusting motor 6, 7 to accommodate the peaks of the camshaft torque.

25

To adjust the camshaft 1 relative to the crankshaft, the adjustment motor 6, 7 is energized until the engine torque exceeds the converted camshaft torque and the camshaft 1 to the crankshaft at the desired adjustment speed (preferably 30 ° to 130 ° cam angle per second)

30 is adjusted. The adjustment motor 6, 7 requires different directions of rotation for adjustment in the “early” or “late” direction. Furthermore, for adjustment requires more power in the direction of rotation of the camshaft than against the direction of rotation of the camshaft, since the camshaft friction torque must also be overcome in the direction of rotation of the camshaft.

According to the invention, in a first variant, the adjusting motor 6 is dimensioned such that the self-holding torque of the permanent magnets when idling ιjncLnied] J ^ ec J ^ ehzahIa ^ dιas A ^

1 and fix the crankshaft to each other. Then the adjusting motor 6 only has to be supplied with low current and / or an external torque (for example that of the braking device 12) for fixing the crankshaft to the camshaft 1 only at higher loads.

In principle, it is also possible to dimension the adjusting motor 6 in such a way that the self-holding torque is always greater than the converted camshaft torque.

If the self-holding torque of a servomotor 6 with permanent magnets is greater than the torque required for the adjustment (eg at low camshaft speeds), the adjustment can only take place when the electromagnetic torque is greater than the self-holding torque of the servomotor 6. This means that the adjustment speeds are very high, which means that it cannot be adjusted at low adjustment speeds and it is difficult to make small control jumps. In order to avoid this, short current surges are fed to the adjusting motor 6 in the control position, which can be varied with regard to frequency, amount and direction. This means that even small changes in the rules can be achieved.

The adjustment gear 2 has no self-locking, but instead has a high mechanical efficiency and thus achieves favorable energetic conditions in the adjustment operation. In a second variant, the externally excited adjusting motor 7 is dimensioned such that its holding torque is sufficient at low current when idling and at low engine speed to fix the camshaft 1 and the crankshaft to one another. Here, higher oscillation angle amplitudes occur at camshaft torques with zero crossing. The adjusting motor 7 only has to be supplied with current at higher loads and / or an exrernesπ o erϊrτzrEr ron αer BremsvorπcrTtung T2 for ixieren the cam shaft to camshaft 1.

In this variant too, the adjusting motor 7 can be dimensioned such that the holding torque is always greater than the converted camshaft torque when the current is low. Here too, the adjustment gear 2 is used without self-locking and with a high degree of efficiency in order to maintain favorable energetic conditions in the adjustment operation.

In a third variant, an external holding torque, e.g. B. generated by the switchable and controllable mechanical braking device 12. When the internal combustion engine is idling and at low engine speeds, this is sufficient to fix the camshaft 1 and the crankshaft to one another, so that the adjusting motor 6, 7 has to be energized to fix the camshaft 1 to the crankshaft only at higher loads. Here, too, it is possible to apply an external torque that is always greater than the converted camshaft torque. In this case too, an adjustment gear 2 is used without self-locking and with a high degree of efficiency in order to maintain favorable energy conditions in the adjustment mode.

Alternatively, the external moment can also be applied by a braking device 12 designed as a spring pressure brake, which is integrated in or on the adjusting motor 6, 7 and which automatically intervenes in an almost de-energized state. For the different torques, the following ranges of values should preferably be selected based on the output shaft of the adjusting motor 6, 7 or on the adjusting shaft 9:

^■ Self-holding torque with permanent magnets:

0.05 to 1.4 Nm, preferably 0.1 to 0.7 Nm,

^■ Electromagnetically generated moment:

0.1 to 10 Nm, preferably 0.3 to 0.5 Nm,

^External moment of the braking device 12:

0.05 to 10 Nm, preferably 0.1 to 5 Nm.

In summary, the device according to the invention offers the following advantages:

1. Improvement in efficiency due to lower power consumption when

Keeping the camshaft adjusting device in the normal position and more favorable energetic conditions in the adjusting operation by using an adjusting gear 2 without self-locking; 2. little or no additional thermal load on the adjusting motor 6, 7 when fixing the camshaft 1 to the crankshaft. As a result, the adjustment motor 6, 7 can be dimensioned smaller, which reduces costs. With the same size, its service life increases;

3. The rigidity of the camshaft drive is increased by an effective holding torque, whereby the rotational angle vibrations in the control positions are reduced. LIST OF REFERENCE NUMBERS

camshaft

variator

drive shaft

camshaft drive wheel

Δ triohcλA / ΩllΩ

Actuator with permanent magnet

Variable motor with external excitation

rotor

adjusting

stator

gearbox

braking device

Claims

claims

1. Device for releasably connecting and adjusting two mutually adjustable angle of rotation shafts, in particular the crankshaft and the camshaft (1) of an internal combustion engine, with an adjusting gear (2) designed as a three-shaft gearbox, that a crankshaft-connected πe- ^ πτπeDsweτre-r ^ -ern ^" e ^" τiO ^" c eπ A live TS) and a rotating electric adjusting motor (6, 7), the rotor (8) with an adjusting shaft (9) of the adjusting gear (2) and the stator (10) with the drive shaft (3) are firmly connected, characterized in that the torque balance of the three shafts (3, 5, 9) required for fixing a control position of the camshaft (1) or their synchronization can be achieved by coupling the drive shaft (3) and the adjusting shaft (9) , preferably via a holding torque of the adjusting motor (6, 7) in connection with a transmission ratio of the camshaft torque to the level of the holding torque between the output drive elle (5) and the adjusting shaft (9) of a low-friction three-shaft transmission.

2. Device according to claim 1, characterized in that the adjusting motor is a permanent magnet adjusting motor (6) or an externally excited adjusting motor (7).

3. Device according to claim 2, characterized in that the material of the permanent magnets preferably has rare earths.

4. The device according to claim 3, characterized in that the permanent magnet adjustment motor (6) is adjustable by current pulses which are variable in their height, frequency and direction.

5. The device according to claim 4, characterized in that the holding torque of the adjusting motors (6, 7) by a the rotor (8) and the stator (10) brake device (12) releasably connecting by means of frictional forces can be enlarged.

6. The device according to claim 5, characterized in that the braking device (12) with mechanical, electromagnetic, hydraulic or pneumatic actuation and control can be carried out.

7. The device according to claim 6, characterized in that the mechanically actuated braking device (12) is designed as a spring pressure brake and is arranged on or in the adjusting motor (7).

8. The device according to claim 7, characterized in that the braking device (12) is used automatically with mechanical actuation when the adjusting motor (6, 7) is in an almost de-energized state.

9. The device according to claim 8, characterized in that the adjusting motor (6, 7) has a power that allows an adjustment speed of 30 ° to 130 ° cam angle per second when the camshaft (1) is adjusted.

10. The device according to claim 9, characterized in that the adjusting motor (6, 7) as an outer, intermediate or inner rotor motor with a roller or disc rotor can be formed and that the rotor (8) and the stator (10) are interchangeable.