KR20090096465A - Control structure for electro-mechanical camshaft phase shifting device - Google Patents

Abstract

A camshaft phase shifting device (30) includes a coaxially arranged three-shaft gear system, having an input shaft (16), an output shaft (14), and a control shaft (34) for adjusting the phase angle between the input and output shafts (16, 14). The control structure is a torque-based control structure. The dynamic response of the gear system and thus the desired phase angle of a camshaft (12) associated with the output shaft (16) is controlled and adjusted by a controller (40) which produces a torque command based on received signals. These signals include, but are not limited to, cam shaft phase angle error signal, torque load, and/or angular position signal of the camshaft (12), and relative speed signal between the input and output shafts (16, 14). The torque command is converted by an electric machine (32) into an electro-magnetic torque exerting on the control shaft (34) of the camshaft phase shifting device (30), and includes two parts, a feed forward part to compensate for the known disturbances in system torques and a feedback part to compensate for unknown disturbances.

Description

CONTROL STRUCTURE FOR ELECTRO-MECHANICAL CAMSHAFT PHASE SHIFTING DEVICE}

This application claims priority to Application No. 60 / 868,644, filed December 5, 2006 in the United States, which includes all of the contents of such application.

BACKGROUND OF THE INVENTION The present invention generally relates to camshaft adjustment mechanisms for use in internal combustion engines, and more particularly to control structures for electromechanical camshaft phase shifting devices.

Camshaft phase shifting devices are used very frequently in gasoline engines to vary the valve timing to achieve the effect of improving fuel consumption and exhaust gas quality. There are many ways to camshaft phase shifting devices. Hydraulic regulators are common in many applications today. Important attempts have been made on hydraulic regulators, including improving the slew rate in low speed operation, maintaining accurate camshaft angular position, and extending the operating temperature range. Furthermore, it is urgently needed to adjust the cam phase angle before or during the start of the engine to reduce contamination emissions. This is possible only if the camshaft phase shifting device is controlled before or during engine start. These attempts are only possible with electromechanical camshaft phase shifting devices.

The international application No. PCT / US2007 / 078755 (continuous camshaft phase shifting device), filed on September 18, 2007 and which is the basis of the priority covered by the present invention, is an electromechanical camshaft phase shifting device. (eCPS) is disclosed. The eCPS device comprises a three axis gear unit and an electrical machine. According to the request from the engine electrical control unit (ECU), the electric machine is operated in one of three possible modes: neutral mode of operation, motoring mode and power generation mode to achieve the desired target performance. The present invention discloses a control structure that provides explicit means for an eCPS device to implement these three modes. The control structure disclosed may additionally be applied to control the operation of other similar electromechanical camshaft phase shifting devices.

Briefly mentioned, the present invention generally provides a control structure for an electromechanical camshaft phase shifting device, and in particular, a control structure for an electromechanical camshaft phase shifting device with an automatic locking mechanism. .

In one embodiment of the invention, the camshaft phase shifting device is arranged coaxially and has a three-axis gear system having an input shaft, an output shaft and a control shaft for adjusting the phase angle between the input and output shafts. Include. The control structure is a torque based control structure. The mechanical response of the gear system and thus the desired phase angle of the camshaft is controlled and adjusted by a controller (or compensator) that generates a torque command based on the received signal. Such signals include, but are not limited to, camshaft phase angle error signals (deviation of the cam phase shift angle from a reference value), torque rod and / or angular position signals of the camshaft and the relative between the input and output shafts. It includes a speed signal. This torque command (for example a voltage signal) is then converted by the electric machine into electromechanical torque and applied on the control shaft of the camshaft phase shifting device. The torque command includes two parts, a feed forward portion for compensating known disturbances in the system torque, and a feed forward portion for resolving unknown disturbances and tracking reference changes. Optionally, the controller may include an ON / OFF switch to turn off the torque command to save energy if it is determined that the automatic locking mechanism is to be activated.

The features and advantages described above in the preferred embodiments as well as the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

1 is a block diagram showing a preferred control structure for controlling the electromechanical cam phase shifting device of the present invention;

2 is a cross-sectional view of an electromechanical cam phase shifting device,

3 is an input / output diagram of the control structure of FIG. 1;

4 is a block diagram showing an alternative control structure for controlling the electromechanical cam phase shifting device of the present invention.

The accompanying reference numbers indicate corresponding parts throughout the several views of the drawings. It is to be understood that the drawings illustrate concepts that illustrate the subject matter of the present invention and do not represent scale factors.

The detailed description set forth below shows the invention in an illustrative manner rather than a restrictive manner. The detailed description of the present invention is intended to enable those skilled in the art to make and use the invention, and to describe several embodiments, applications, variations, substitutions, and uses of the invention, including preferred embodiments for practicing the invention.

1 generally shows a preferred control structure for controlling an electromechanical cam phase shifting device. The system as seen in FIG. 1 includes an engine 10, an engine control unit (ECU) 20, a phase shifting device 30 and a controller (or compensator 40). The phase shifting device 30 is a three-axis, positive differential gear drive having three coaxially rotatable shafts, as depicted in FIG. 2. The input shaft 16 is connected to the engine crankshaft via a sprocket 18 and a chain drive (not shown). The output shaft 14 is connected to the engine cam shaft 12. The control shaft 34 is connected with the rotor of the electric machine 32.

The phase shifting device has a built-in friction automatic locking mechanism to allow the output shaft 14 to be locked with the input shaft 16 so that torque can be transmitted at a 1: 1 speed ratio between the two shafts. Under these conditions, there is no phase change between the input shaft 16 and the output shaft 14. The friction lock between the input shaft 16 and the output shaft 14 can only be released by applying the appropriate torque to the control shaft 34. The required torque is produced by the electric machine 32 connected to the control shaft 34 in response to the torque command received by the electric machine. When the locked state of the phase shifting device is released, there may be a slight difference between the speeds of the input shaft and the output shaft. This allows the camshaft 16 connected to the output shaft 14 to be translated into angular position with respect to the input shaft.

The controller (or compensator 40) generates the torque command, which may be in the form of a voltage signal or any other suitable signal based on the information received by the controller (or compensator, 40). The received information may include, but is not limited to, camshaft phase shift setpoints (reference), or physical camshaft phase shifts measured and / or calculated from one or more respective position sensing signals. The actual cam phase shift angle is compared with a reference value to produce a differential (error) signal. The differential or error signal is then communicated with the PID compensator 42 to generate a feedback torque (torque adjustment) command. The feedback torque command is used to direct the electrical machine to the input of the PID compensator 42 to control and adjust the cam phase angle in order to reduce the error signal. In this process, the desired cam phase shift can be obtained. For torque based control structures, the PID compensator is primarily a ratio derived controller (PD).

In engine applications, the control system may be faulty. The shaft torque varies as a function of cam phase angle while the valve raises the stage. In order to improve the system in response to a reference input and to improve the system's ability to identify and / or eliminate faults, it is often required that a feed forward configuration be used to compensate for any known fault. Therefore, the controller (or compensator 40) may further include a feed forward branch (or unit) 44 to process and compute the expected torque failure in the system. The result signal is fed forward to the output signal of the PID controller and combined with the output signal of the PID controller to form the torque command signal. The predicted torque disturbance, also called feed forward torque, is determined by two factors, T _{rq_static} and T _{rq_friction} . T _{rq_static} is calculated from the frictionless static equilibrium of the three-axis gear drive, while T _{rq_friction} represents the element required to overcome the friction torque on the current cam shaft torque rod. The symbol of T _{rq_friction} is determined by the relative speed between the control shaft 34 and the input shaft 16 (or the output shaft 14). For the configuration of the phase shifting device shown in FIG. 2, the feed forward torque is calculated by the following equation.

T _ffwd = T _{rq_static} + T _{rq_friction} = (1- SR ₀ ) · T _cam + sgn (v) · f (T _cam )

Where T _cam is the camshaft torque rod which is a function of cam phase angle and can be represented by analytical or fixed tables. The value sgn (v) is a symbol representing the relative speed v between the control shaft 34 and the input shaft 16, while the function f (T _cam ) represents the magnitude of the friction torque T _{rq_friction} . .

SR ₀ is the basic velocity ratio with respect to the input shaft 16 of the output shaft 14 given by the following equation.

Here, N denotes a first sun gear 31 connected to the input shaft 16, a second sun gear 33 connected to the output shaft 14, and a first planetary gear connected to the first sun gear 31. The number of teeth of the gears of the subscripts _{S1, S2, P1,} and _P2 representing 35 and the second planetary gear 37 connected to the second sun gear 33 is indicated. As shown in FIG. 2, the first and second planetary gears 35, 37 are supported by the control shaft 34 and on a common planetary assembly 39 that rotates about the control shaft 34. It is held and formed completely together with the common planetary assembly 39.

As mentioned above, since the phase shaft device has an automatic locking feature, the controller and the electric machine are turned to save energy if the actual cam phase shift angle is close to the desired value (reference value or set value). You can turn it off. This is done by, for example, commanding zero torque to the electric machine. 3 shows the execution of the controller 40 in the situation where the power on logic and power switch are seen as separate blocks.

Optionally, the inductive portion of the PID compensator can be moved to the feedback path to reduce the effect of the impact (sudden change) at the reference input. 4 shows the corresponding control structure for this optional configuration.

Also, in order to replace the PID compensator 42, other compensators can be used with alternative control laws such as model prediction controller (MPC), and the present invention can be derived from a control structure based on the current torque. It may include embodiments.

The invention may be implemented as part of a computer-implemented process and a form of apparatus for executing such a process. The invention may also be embodied as part of a computer program code including instructions embodied in a tangible medium such as a floppy diskette, CD-ROM, hard drive, or computer readable storage medium. Here, when the computer program code is loaded into or executed by an electric device such as a computer, a microprocessor or a logic circuit, the device may be a device for practicing the present invention.

The invention also relates to whether it is stored in a storage medium, loaded into a computer and / or executed by a computer, or transmitted to some transmission medium such as an electric wire or cable, or an optical fiber, electromagnetic radiation. It may be implemented as part of the form of computer program code, such as whether or not. Here, when the computer program code is loaded into the computer and executed by the computer, the computer may be an apparatus for the execution of the present invention. When executed as a versatile microprocessor, the computer program code segments constitute a microprocessor that creates a particular logic circuit.

Since various changes may be made in the above configuration without departing from the spirit of the present invention, it should be construed that the embodiments are not intended to limit everything included in the detailed description or shown by the accompanying drawings.

Claims (12)

A three-axis gear system arranged coaxially and having an input shaft, an output shaft and a control shaft configured to adjust a phase angle between the input shaft and the output shaft; A controller operating in connection with the control shaft and controlling an applied electromagnetic torque source to the control shaft in response to at least one input signal to unlock the phase angle of the input shaft relative to the output shaft; Camshaft phase shifting device comprising a. The method of claim 1, And said controller operates in a torque-based control structure. The method of claim 1, And the controller is configured to generate a torque command as a source of the applied electromagnetic torque in response to the at least one input signal of the plurality of input signals. The method of claim 1, The at least one input signal includes, but is not limited to, a set of input signals including a camshaft phase angle error signal, a torque load signal, an angular position signal of the camshaft and a relative velocity signal between the input and output shafts. Camshaft phase shifting device, characterized in that is selected from. The method of claim 1, The source of applied electromagnetic torque is an electrical machine configured to exert the electromagnetic torque on the control shaft, And said electric machine is controlled by a torque command from said controller. The method of claim 5, wherein And said torque command comprises a feed forward component for compensating for known disturbances at least in system torque and a feed forward component for compensating for at least unknown disturbances and tracking reference inputs. The method of claim 6, The feed forward component of the torque command is calculated as T _ffwd = T _{rq_static} + T _{rq_friction} = (1- SR ₀ ) · T _cam + sgn (v) · f (T _cam ) here, T _{rq_static} is a static equilibrium state without friction of the phase shifting device; T _{rq_friction} is the force needed to overcome the friction torque on the current control shaft torque rod; SR ₀ is the basic velocity ratio of the output shaft to the input shaft; T _cam is the control shaft torque rod; sgn (v) represents the sign of the relative speed v between the control shaft and the input shaft; and f (T _cam ) represents the magnitude of the friction torque T _{rq_friction} . The method of claim 7, wherein SR ₀ is calculated according to the following equation,

here, N is a subscript representing each of a first sun gear connected to the input shaft, a second sun gear connected to the output shaft, a first planetary gear connected to the first sun gear, and a second planetary gear connected to the second sun gear. _The number of teeth of the gears of _{S1, S2, P1} and _P2 is shown; And the first and second planetary gears are integrated with a common planetary carrier connected to the control shaft. The method of claim 1, The control shaft includes a friction autolock mechanism configured to phase lock the input shaft and the output shaft, The friction self-locking mechanism transmits torque from the input shaft to the output shaft, The application of torque to the friction autolock mechanism selectively unlocks the phase angle of the input shaft relative to the output shaft. For changing a camshaft phase angle for a camshaft driven through a camshaft phase shifting device comprising an input shaft coaxially aligned, an output shaft and a control shaft which phase locks the input shaft and the output shaft with friction. As a way, Controlling the torque applied to the control shaft, Applying said torque to said control shaft unlocks said input shaft phase from said output shaft phase. The method of claim 10, The controlling of the torque applied to the control shaft includes, but is not limited to, a camshaft phase angle error signal, a torque rod signal, a position signal of the cam shaft, and a relative speed signal between the input and output shafts. And responsive to at least one input signal selected from the set of input signals comprising. The method of claim 10, Controlling the torque applied to the control shaft comprises controlling an electrical machine configured to apply electromagnetic torque on the control shaft.

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