METHOD FOR OPERATING AN ELECTROMECHANICAL CAMSHAFT PHASER

Abstract

An electromechanical camshaft phaser (3) comprises a setting gear (4) and an electric motor (5), which is controlled by means of an electric-motor control unit (6). Data concerning the operation of the electric motor (5) including position changes of its motor shaft are transferred via a data bus (8) from the electric-motor control unit (6) to an engine control unit (7) of the internal combustion engine (1) comprising the camshaft phaser (3). In addition, recurring time signals are transferred from the electric-motor control unit (6) to the engine control unit (7) via a separate line (9), by which harder real-time requirements are met than by the data bus (8). The time signals are used to generate a time difference signal in the engine control unit (7) by comparison with the data received by the engine control unit (7), which time difference signal is fed back to the electric-motor control unit (6) via the data bus (8) and is used there to synchronize the electric-motor control unit (6) with the engine control unit (7).

Description

BACKGROUND

Methods for operating an internal combustion engine with electromechanical camshaft phasing are described, for example, in DE 102 59 133 A1. In this case, the camshaft phaser, that is, the arrangement for adjusting the relative angle of rotation between the camshaft and the crankshaft of the internal combustion engine, has a modular structure, wherein components of the arrangement are partly used by other control and regulating devices of the internal combustion engine. A control unit of the electric motor of the camshaft phaser is connected to a second control unit, which is the engine control unit of the internal combustion engine.

Electromechanical camshaft phasers generally have the advantage over hydraulic camshaft phasers that adjustment of the camshaft is possible even when the internal combustion engine is stationary. In this context, reference is made to DE 10 2012 219 297 A1 as an example.

Further methods for operating camshaft phasers are disclosed, for example, in the documents DE 102 36 507 A1, DE 10 2005 022 714 A1, DE 10 2017 104 015 A1 and DE 102 42 659 A1.

SUMMARY

An object of the present disclosure is to further develop an electromechanical camshaft phaser with regard to the most efficient possible use of resources, in particular with regard to data processing processes, compared to the cited prior art.

This object is achieved according to the present disclosure by a method for operating an electromechanical camshaft phaser with the features of claim 1. The method can be carried out with the aid of a device for controlling an internal combustion engine according to claim 7. The configurations and advantages of the present disclosure explained below in connection with the control device also apply analogously to the operating method, and vice versa. Advantageous further developments of the present disclosure are described in the dependent claims.

The camshaft phaser, which is operated according to the method according to the present disclosure, comprises a setting gear, in particular in the form of a triple-shaft gear mechanism, and an electric motor provided for actuating the setting gear, which is controlled by means of an electric-motor control unit. Data relating to the operation of the electric motor, including position changes of its motor shaft, are transmitted via a data bus from the electric-motor control unit to an engine control unit of the internal combustion engine comprising the camshaft phaser. In addition, recurring time signals are transmitted from the electric-motor control unit to the engine control unit of the internal combustion engine via a separate line, by means of which harder real-time requirements are met than by means of the data bus. Said time signals are used to generate a time difference signal in the engine control unit by comparing it with the data received by the engine control unit from the electric-motor control unit, which is fed back to the electric-motor control unit via the data bus and is used there to synchronize the electric-motor control unit with the engine control unit.

The data bus, which connects the electric-motor control unit with the engine control unit of the internal combustion engine and both control units with further components of the internal combustion engine, is in particular a CAN bus. Although it does not meet any hard real-time requirements, this data bus is used to transmit the time difference signal required for synchronization from the electric-motor control unit to the engine control unit of the internal combustion engine. In the opposite direction, that is from the electric-motor control unit to the engine control unit, the data bus is bypassed, in that time signals are transmitted over the separate line. Overall, a high-precision synchronization is possible with the best possible utilization of the hardware resources.

Various configurations are possible with regard to the distribution of data processing processes to the two control units, that is to say on the one hand, the engine control unit of the internal combustion engine, and on the other hand, the electric-motor control unit controlling the camshaft phaser. For example, successive processes which relate to the camshaft phaser are processed both in the electric-motor control unit and in the engine control unit, wherein the respective data on the processes are recorded in a ring memory integrated in the electric-motor control unit, or in the engine control unit. In a preferred embodiment of the method, the evaluation of the data stored in the ring memories takes place, for the most part, within the electric-motor control unit.

The duration of each process, which is also generally referred to as a task, is typically at least twice, in particular at least three times, the time difference used for synchronization between the various control units.

The data recorded and transmitted by the electric-motor control unit can include trigger signals which relate to a specific camshaft position and are provided with a time stamp.

Hall sensors, for example, can be used in a known manner known to detect the angular position and/or direction of rotation of the rotor of the electric motor. The electric motor is preferably a brushless direct current motor. The setting gear, which is actuated by means of the electric motor, is designed, for example, as a harmonic drive. With regard to the design features, reference is made, for example, to the documents DE 10 2017 119 860 A1 and DE 10 2017 126 527 A1.

BRIEF SUMMARY OF THE DRAWINGS

In the following, an exemplary embodiment of the present disclosure is explained in more detail by means of a drawing. In the figures:

FIG. 1 shows a symbolized representation of an internal combustion engine with a camshaft phaser and control units,

FIG. 2 shows a diagram explaining the operation of the internal combustion engine according to FIG. 1.

DETAILED DESCRIPTION

An internal combustion engine 1, shown merely symbolically in FIG. 1, the engine block of which is denoted by 2, has an electromechanical camshaft phaser 3. A setting gear 4 of the camshaft phaser 3 is designed as a triple-shaft gear mechanism, for example a harmonic drive. In this case, a first shaft of the setting gear 4 is identically or permanently connected to a belt or chain wheel and rotates in a known manner at half the crankshaft speed of the internal combustion engine 1. A second, output-side shaft of the setting gear 4 is connected in a rotationally-fixed manner to the camshaft which is to be phased. To adjust the angle between the input-side shaft connected to the chain or belt wheel and the output-side shaft of the setting gear 4, the setting gear 4 has a third shaft in the form of a setting shaft which is connected in a rotationally-fixed manner to the motor shaft of an electric motor 5, which is assigned to the camshaft phaser 3. The electric motor 5 is controlled by means of an electric-motor control unit 6, which is also referred to as a driver box, via a line 9.

The electric-motor control unit 6 is linked, to the engine control unit, labeled 7, of the internal combustion engine 1, via a data bus 8, namely a CAN bus. The control units 6, 7 are designed to process processes, which are generally referred to as tasks and are illustrated in FIG. 1 using diagrams. Each control unit 6, 7 comprises a data memory designed as a ring memory 10, 11. Individual data packets which are kept ready for evaluations in the ring memory 10, 11 of the respective control unit 6, 7 are illustrated in FIG. 1 by parallel lines. The processing of this data is to be understood as batch processing of data. As illustrated in FIG. 1, the number of data processing tasks to be processed by the electric-motor control unit 6 exceeds the number of data processing tasks to be carried out by the engine control unit 7. In the exemplary embodiment illustrated, the ratio between the number of data packets to be processed stored in the ring memory 10 of the electric-motor control unit 6 to the number of data packets to be processed in an analog manner by the engine control unit 7 is 4:3. In modified variants, not shown, other ratios, for example the ratio 4:1, are also possible. In all cases, the evaluation of the data stored in the various ring memories 10, 11, insofar as they relate to the camshaft phaser 3, takes place, for the most part, within the electric-motor control unit 6. This means that the engine control unit 7 is only burdened to a minor extent with the processing of data relating to the operation of the camshaft phaser 3.

In addition to the CAN bus 8, there is a line 9, with which a data connection is established between electric-motor control unit 6 and the engine control unit 7. The line 9 is used to send time signals from the electric-motor control unit 6 to the engine control unit 7. The data volume of the transmitted time signals is only a small fraction of the data transmitted between the electric-motor control unit 6 and the engine control unit 7 via the CAN bus 8. However, in contrast to the CAN bus 8, hard real-time requirements can be met with the aid of the line 9.

Data processing processes which relate to specific, similar signal patterns and which are to be carried out in the electric-motor control unit 6 and in the engine control unit 7 are illustrated in FIG. 2. Here, the upper diagram in FIG. 2 relates to the electric-motor control unit 6. Signals to be processed by the electric-motor control unit 6 are denoted by S_V. The lower diagram in FIG. 2 relates to the data processing carried out by the engine control unit 7. In this case, signals to be processed are denoted by S_M. A process to be processed by the electric-motor control unit 6 is expected, which begins at time t₀ and lasts until time t₁. The duration of this process, that is to say task, is denoted by T_T. Data that is to be assigned to the task of duration T_T includes information relating to the electric motor 5 and the camshaft to be phased. This includes, for example, the detection of reference marks on the camshaft or a part that has a fixed angular relationship to the camshaft. The direction of rotation of the setting shaft, which is identically or permanently connected to the motor shaft of the electric motor 5, is also recorded and evaluated within the context of the task. The same applies to any changes in the state or the duration of individual states of components of the electric motor 5. A component of the electric motor 5 that should be mentioned in particular is its rotor, wherein its angular position and change in angle, if stored in the ring memory 10, is included in the data processing within the electric-motor control unit 6.

Insofar as data of the task with which the electric-motor control unit 6 is concerned are transmitted to the engine control unit 7, the corresponding signal patterns also appear in the engine control unit 7, as can be seen from FIG. 2. Timings in the engine control unit 7 that can be assigned to the timings t₀, t₁ and t₂ are denoted by t₀′, t₁′ and t₂′. Due to the given properties of the CAN bus 8, a time difference occurs between the data received in the engine control unit 7 and the data sent by the electric-motor control unit 6, which is denoted by T_D in FIG. 2. The time difference T_D is less than half the task duration T_T. The value of the time difference T_D is used to set the clock of the electric-motor control unit 6 according to the engine control unit 7 and thus to synchronize the data processing processes in the control units 6, 7.

LIST OF REFERENCE SYMBOLS

• • 1 Internal combustion engine
  • 2 Engine block
  • 3 Camshaft phaser
  • 4 Setting gear
  • 5 Electric motor
  • 6 Electric-motor control unit
  • 7 Engine control unit of the internal combustion engine
  • 8 CAN data bus
  • 9 Line
  • 10 Ring memory in the electric-motor control unit
  • 11 Ring memory in the engine control unit
  • S_M signal, processed by engine control
  • S_V signal processed by electric-motor control
  • t Time
  • t₀, t₁, t₂ timings relating to the data processing in the electric-motor control unit
  • t₀′, t₁′, t₂′ timings relating to the data processing in the engine control unit
  • T_D time difference
  • T_T Duration of a task

Claims

1. A method for operating an electromechanical camshaft phaser, the electromechanical camshaft phaser comprising a setting gear and an electric motor provided for actuating the setting gear, which is controlled by an electric-motor control unit, the method comprising: transmitting data concerning the operation of the electric motor, including position changes of a motor shaft of the electric motor, via a data bus from the electric-motor control unit to an engine control unit of an internal combustion engine comprising the camshaft phaser;transmitting recurring time signals from the electric-motor control unit to the engine control unit via a separate line, by which harder real-time requirements are met than by the data bus;using the time signals to generate a time difference signal in the engine control unit by comparison with the data received by the engine control unit;feeding the time difference signal back to the electric-motor control unit via the data bus; andusing the time difference signal in the electric-motor control unit to synchronize the electric-motor control unit with the engine control unit.

2. The method according to claim 1 further comprising processing successive processes which relate to the camshaft phaser both in the electric-motor control unit and in the engine control unit; and recording the respective data on the processes in a ring memory integrated in the electric-motor control unit or in the engine control unit.

3. The method according to claim 1 wherein each of the electric-motor control unit and the engine control unit includes a ring memory, the method further comprising evaluating the data stored in the ring memories, for the most part, within the electric-motor control unit.

4. The method according to claim 1, wherein the data recorded and transmitted by the electric-motor control unit comprises trigger signals which relate to a specific camshaft position and are provided with a time stamp.

5. The method according to claim 4, further comprising detecting the position changes of the rotor of the electric motor by Hall sensors.

6. A device for controlling an internal combustion engine having at least one electromechanical camshaft phaser, the electromechanical camshaft phaser comprising a setting gear and an electric motor provided for actuating the setting gear, the device comprising: an engine control unit for controlling the internal combustion engine; andan electric-motor control unit for controlling the electric motor, the engine control unit and the electric-motor control unit being programmed to: transmit data concerning the operation of the electric motor, including position changes of a motor shaft of the electric motor, via a data bus from the electric-motor control unit to the engine control unit;transmit recurring time signals from the electric-motor control unit to the engine control unit via a separate line;use the recurring time signals to generate a time difference signal in the engine control unit by comparison with the data received by the engine control unit;feeding the time difference signal back to the electric-motor control unit via the data bus; anduse the time difference signal in the electric-motor control unit to synchronize the electric-motor control unit with the engine control unit.

7. The device is as recited in claim 6, wherein the separate line has a lesser volume of data transmitted than the data bus.

8. An internal combustion engine comprising: an engine block;the device as recited in claim 6;the data bus;the separate line; andthe electromechanical camshaft phaser comprising the setting gear and the electric motor provided for actuating the setting gear.

9. The internal combustion engine as recited in claim 8, wherein the data bus is configured to transmit data between the electric-motor control unit and the engine control unit and between the engine control unit and the engine block, and the separate lines is configured to transmit data between the electric-motor control unit and the engine control unit and between the electric-motor control unit and the electric motor.

10. A method for operating an electromechanical camshaft phaser, the electromechanical camshaft phaser comprising a setting gear and an electric motor provided for actuating the setting gear, the electric motor being controlled by an electric-motor control unit, the method comprising: transmitting data concerning the operation of the electric motor, including position changes of a motor shaft of the electric motor, via a data bus from the electric-motor control unit to an engine control unit of an internal combustion engine comprising the camshaft phaser;transmitting recurring time signals from the electric-motor control unit to the engine control unit via a separate line;using the recurring time signals to generate a time difference signal in the engine control unit by comparison with the data concerning the operation of the electric motor transmitted by the electric-motor control unit to the engine control unit;feeding the time difference signal back to the electric-motor control unit via the data bus; andusing the time difference signal in the electric-motor control unit to synchronize the electric-motor control unit with the engine control unit.

11. The method is as recited in claim 10, wherein the separate line has a lesser volume of data transmitted than the data bus.

12. The method as recited in claim 10, wherein the recurring time signals are stored in a memory of the electric-motor control unit and a memory of the engine control unit, a timing of the time signals stored in the memory of the electric-motor control unit being offset from a timing of the time signals stored in the memory of the engine control unit by a time difference represented by the time difference signal.

13. The method as recited in claim 10, wherein time signals of the recurring time signals represent tasks to be processed by the electric-motor control unit, at least one of the tasks having a task duration, the time difference being less than half of the task duration.

14. The method as recited in claim 10, wherein the data concerning the operation of the electric motor includes detection of reference marks on the camshaft or a part that has a fixed angular relationship to the camshaft.

15. The method as recited in claim 10, wherein the data concerning the operation of the electric motor includes a direction of rotation of a setting shaft connected to the motor shaft of the electric motor.

16. The method as recited in claim 10, further comprising controlling the internal combustion engine using the synchronized electric-motor control unit and engine control unit.

17. The method as recited in claim 10, wherein each of the recurring time signals represent a task to be processed by the electric-motor control unit, the method further comprising controlling the electric motor via the electric-motor control unit to perform the task.