CN111219223A

CN111219223A - Electrically actuated variable camshaft timing device controller

Info

Publication number: CN111219223A
Application number: CN201911132508.6A
Authority: CN
Inventors: R·基夫沃尔
Original assignee: BorgWarner Inc
Current assignee: BorgWarner Inc
Priority date: 2018-11-26
Filing date: 2019-11-19
Publication date: 2020-06-02
Also published as: US20200165942A1; DE102019131704A1

Abstract

An electrically actuated VCT device cascade controller comprising: a system processing device configured to receive input from one or more sensors and generate an output signal that is communicated to an electric phaser motor; and a system processing device: receiving data indicative of an angular position of a camshaft relative to an angular position of a crankshaft at a primary control loop; receiving data indicative of an angular velocity of the crankshaft at the secondary control loop; and generates an output signal that controls the electric phaser motor using the primary control loop and the secondary control loop.

Description

Electrically actuated variable camshaft timing device controller

Technical Field

The present application relates to Variable Camshaft Timing (VCT), and more particularly, to a controller for a variable camshaft timing apparatus.

Background

Internal Combustion Engines (ICEs) use an annular ring, such as a chain or belt, that engages the crankshaft and the camshaft to transmit rotational force from the crankshaft to the camshaft. In the past, the angular relationship between the crankshaft and the camshaft was fixed. Many ICEs now use Variable Camshaft Timing (VCT) to change the angular position of the camshaft relative to the crankshaft. The devices used to implement VCT and vary the angular position of the camshaft relative to the crankshaft may vary in design and may be actuated electrically or hydraulically. Electrically actuated VCT devices rely on an electric motor to adjust the angular position of a camshaft relative to a crankshaft. The motor is controlled by a control system which can be implemented in a number of ways. For example, the control system may receive an input identifying an error between a commanded angular relationship and an actual angular relationship of the crankshaft and the camshaft. However, the control system may lag or exceed the commanded angular relationship, and greater accuracy and/or responsiveness may improve engine performance.

Disclosure of Invention

In one implementation, an electrically actuated VCT device cascade controller includes: a system processing device configured to receive input from one or more sensors and generate an output signal that is communicated to an electric phaser motor; the system processes the device: receiving data indicative of an angular position of a camshaft relative to an angular position of a crankshaft at a primary control loop; receiving data indicative of an angular velocity of the crankshaft at the secondary control loop; and generates an output signal that controls the electric phaser motor using the primary control loop and the secondary control loop.

In another implementation, a method for controlling an electrically actuated VCT device having a cascaded controller includes: receiving data indicative of an angular position of a camshaft relative to an angular position of a crankshaft at a primary control loop; receiving data indicative of an angular velocity of the crankshaft at the secondary control loop; generating an output signal for controlling an electric phaser motor using a primary control loop and a secondary control loop; transmitting the output signal to an electric phaser motor; an angular position of the camshaft relative to an angular position of the crankshaft is adjusted based on the output signal.

Drawings

FIG. 1 is a perspective view depicting an implementation of a system in which an electrically actuated Variable Camshaft Timing (VCT) device cascade controller may be implemented;

fig. 2 is a cross-sectional view depicting an implementation of an electric phaser motor of a VCT device that may be used with a cascaded controller;

fig. 3 is a perspective view depicting a portion of an implementation of an electric phaser motor;

fig. 4 is a perspective view depicting an implementation of an assembly including an electric phaser motor and a VCT device; and

fig. 5 is a block diagram depicting an implementation of an electrically actuated VCT (device) cascade controller.

Detailed Description

The following describes an electrically actuated variable camshaft timing device cascade controller ("cascade controller" or "device controller") and a method of controlling an electrically actuated VCT device. The cascade controller receives an input indicative of an angular position of the camshaft relative to the crankshaft, an input indicative of an angular velocity of the crankshaft, and an input indicative of an angular velocity of an output shaft of the motor, which actuates the VCT device to generate a control signal for adjusting the output shaft. The cascade controller uses a cascade control system that includes an external/main controller and an internal/auxiliary controller. The main controller may receive an input indicative of an angular position of the camshaft relative to an angular position of the crankshaft; this may also be referred to as the phase relationship between the camshaft and the crankshaft. And the secondary controller may receive input indicative of crankshaft angular velocity. The device controller may use these inputs to generate or output a control signal directing the motor to actuate the VCT device to increase or decrease the angular velocity of the output shaft of the motor or to maintain the angular velocity of the output shaft. Maintaining the angular velocity of the output shaft may maintain the relative angular position of the camshaft with respect to the crankshaft, while increasing or decreasing the angular velocity of the output shaft may change (advance or retard) the angular position of the camshaft with respect to the crankshaft.

The actual angular position of the camshaft relative to the crankshaft may reflect the primary variable used to generate the control signal as compared to the target angular position of the camshaft relative to the crankshaft. However, as operating conditions of an Internal Combustion Engine (ICE) change, providing an output signal to the electric motor based solely on the actual/measured angular relative position of the camshaft may not reflect the current operating conditions of the ICE, but may reflect past operation. Outputting a control signal based on the rearview data can reduce the responsiveness of the control system and delay the identification and arrival of the target phase. In one example of varying operating conditions, an ICE operating at a relatively high Revolutions Per Minute (RPM) may then be quickly brought into an idle state. In the past, control systems have monitored the actual angular position of the camshaft relative to the target angular position of the camshaft, and have not detected a difference between these two values despite a rapid drop in engine RPM. Past control systems continue to detect zero error between the actual phase and the target phase despite the reduction in crankshaft RPM. Past systems output control signals that direct the motor to maintain the angular speed of the output shaft that has been selected for higher RPM camshaft angular speeds. As the RPM of the crankshaft decreases, the RPM of the camshaft also decreases. However, the maintained output shaft angular velocity may inadvertently advance the camshaft angular position relative to the crankshaft angular position. The error value between the measured angular position and the target angular position may increase and the controller may respond, but may respond after a period of time, during which the adjusted angular position of the camshaft is not optimal.

In contrast, the cascade controller implementing the cascade control system described herein uses the phase error and the angular speed of the crankshaft to output a control signal for the motor that is more sensitive to changes in RPM even when there is zero error between the actual relative angular position of the camshaft relative to the target relative angular position of the camshaft (e.g., as would exist during a stable RPM value).

Turning to fig. 1-4, embodiments of a system 10 are shown in which an electrically actuated VCT device cascade controller and a method of controlling an electrically actuated VCT device may be implemented. The system 10 includes electronic hardware that monitors angular motion of the crankshaft and camshaft of the internal combustion engine 12. Angular movement of the crankshaft and camshaft relative to each other may be used to generate motor control signals from a machine controller for advancing, retarding, or maintaining a phase relationship between the crankshaft and camshaft through a VCT machine (also referred to as a camshaft phaser 14). The internal combustion engine 12 includes a crankshaft 16 and one or more camshafts 18 (one shown). Attached to each camshaft 18 is a cam sprocket 20. The camshaft 18 may be mechanically driven by a crankshaft sprocket 22, the crankshaft sprocket 22 being connected to a nose portion 24 of the crankshaft 16 by a cam sprocket 20. As crankshaft 14 rotates, a driven member 26, such as a chain or belt, drives camshaft 18 by converting the rotational motion of crankshaft 16 into rotational motion of camshaft 18. The number of teeth of the crankshaft sprocket 22 is half that of the cam sprocket, so two 360 degrees of rotation of the crankshaft 16 results in one 360 degree rotation of the camshaft 18. Rotational movement of the crankshaft 16 may occur in response to the starter motor selectively engaging the flywheel during cranking or in response to piston movement during engine operation.

The crankshaft 16 includes a crank wheel 28 that may be used to identify an angular position and/or angular velocity of the crankshaft 16. A crank wheel 28 is mounted on the nose portion 24 of the crankshaft 16 adjacent the crankshaft sprocket 22 and may be implemented as a 60-2 crank wheel. This means that the crank wheel 28 comprises 58 evenly spaced teeth around the circumference of the wheel 28 and a spacing along the circumference where two teeth are deliberately omitted. This space, also referred to as crank throw 30, identifies a crankshaft rotation point defined relative to combustion, such as Top Dead Center (TDC). Although this embodiment is described with respect to a 60-2 crank wheel, it will be appreciated that crank wheels having different numbers of teeth and indexing dimensions may be used instead to the same effect. As the crank wheel 28 rotates with the crank axle 16, a crank position sensor 32 located near the teeth on the crank wheel 28 generates a signal indicating the absence or presence of teeth on the crank wheel 28. The crank position sensor 32 may be implemented as a hall effect sensor that generates a high voltage level when a tooth passes the sensor 32 and a low voltage level when the indexer 30 passes the sensor 32 or when the sensor 32 is located between teeth on the crank wheel 28. The output of the crank position sensor 32 may be sent to a microcontroller that implements various computational processes, including but not limited to the device controller disclosed herein. This will be discussed in more detail below. In response to the indexing on the crank wheel 28 having removed teeth from the regularly spaced pattern, the microcontroller may recognize the change and provide a signal to replace the missing signal. If the microcontroller is counting crank pulses, the microcontroller may add the missing teeth to the count after passing and identifying the index position.

The angular position of the camshaft phaser 14 relative to the crankshaft 16 controls the angular position of the camshaft 18. The electric phaser motor 34 adjusts the phase of the camshaft 18 relative to the crankshaft 16 by driving a mechanical gear box of the camshaft phaser 14 via an output shaft 46 of the electric phaser motor 34 in accordance with the received motor control signal. The system 10 may be used with a variety of different cam phasers controlled by an electric motor to rotate the motor to maintain phase, such as the split ring gear planetary cam phaser described in U.S. patent application publication No. 2015/0315939, the contents of which are incorporated by reference. The motor-driven cam phaser 14 includes a cam sprocket 20 and an electric phaser motor 34 that may be rotatably engaged with a sun gear of a planetary gear set (not shown) to vary the angular position of the camshaft relative to the angular position of the crankshaft. The planetary gear sets mesh with two ring gears having different numbers of teeth. One ring gear is included on the portion of the camshaft phaser 14 that is attached to the cam sprocket 20, while the other ring gear is attached to the camshaft 18. When the sun gear is rotated by the electric phaser motor 34 at the same speed as the two ring gears, a constant cam phase is maintained. However, when the electric phaser motor 34 drives the sun gear at a different speed than the ring gears, a slight difference in speed of one ring gear from the other results in a change in cam phase. Camshaft 18 may be phase shifted over a range of angles defined by a stop that limits the change in the angular position of camshaft 18 between a fully retarded position and a fully advanced position. In some implementations, the range may be up to 140 degrees. It should be appreciated that this is one particular implementation of a cam phaser controlled by a motor, and other cam phaser designs including a motor may also be successfully used.

The electric phaser motor 34 of the camshaft phaser 14 includes a number of magnets 38 on a rotor 40 connected to an output shaft 46. Fig. 2 depicts a cross-section of the motor 34 having magnets 38, a rotor 40, a stator 42, and coils 44. The number of magnets 38 used in the electric phaser motor 34 may depend on the design of the electric phaser motor 34. In the embodiment shown in fig. 2, ten magnets 38 are included on the rotor 40. When current is applied to the electric phaser motor 34, the magnet 38 rotates about an axis (x) that is coaxial with the output shaft 46. As shown in fig. 3, a defined number of motor sensors 48 are located near the rotational path (p) of the magnets 38 of the electric phaser motor 34 such that when the motor 34 is running and the output shaft 46 is rotating, the sensors 48 detect the presence or absence of those magnets 38 as the rotor 40 moves. Fig. 3 also shows a motor cover 50, which motor cover 50 is removed from the electric phaser motor 34 to expose the interior of the cover 50 that houses the rotor 40 of the motor 34. The interior of the cover 50 includes the motor sensor 48 and the stator poles 52 of the stator 42. Although the hall sensor is shown in the cover as interacting with the magnet of the rotor, the sensor may be of any type, including a hall sensor that interacts with a separate sensor magnetic ring having any number of magnetic north and south poles facing the sensor when the motor is rotating. Optical sensors may also be used to determine the position or angular velocity of the output shaft 46. The hall sensor may be the same as the sensor used to commutate the brushless dc motor.

In implementations in which the electric phaser motor 34 includes ten magnets 38 and three hall effect sensors 48, positioned such that when the motor 34 is operating, as the magnets 38 pass along path (p), the magnets 38 induce a voltage in the hall effect sensors 48, and a 360 degree rotation of the output shaft 46 generates thirty high voltage pulses from the sensors 48. The signals from the three sensors may be combined to generate a signal having 30 pulses. Alternatively, a signal with 15 pulses may be generated, with the microcontroller interpreting each rising or falling edge as an event for calculating motor motion and pulse frequency. In this context, the term high voltage may refer to 5 volts (V), while low voltage may refer to a 0V value output by the hall effect sensor 48, although other values are possible. A microprocessor in the form of a motor controller 54 may receive the output from the sensor 48, the sensor 48 detecting the passing magnet 38 of the electric phaser motor 34, and outputting a motor position signal indicative of the frequency at which the magnet 38 is detected. The output from the sensor 48 may be used to determine the angular or rotational speed of the output shaft 46 of the electric phaser motor 34. In one embodiment, the motor controller 54 may be implemented using a three-phase brushless direct current (BLDC) motor controller and MOSFET drivers.

In addition to the motor controller 54, the system 10 may also include a system processing device 56, the system processing device 56 being another independent microprocessor/microcontroller, such as an Electronic Control Unit (ECU), that receives the motor position signal from the motor controller 54 and the output of the crankshaft position sensor 32 and the electrical controller 54. The system processing device 56 may use this information to execute the cascade controller disclosed herein. The system processing device 56 may be any type of device capable of processing electronic instructions including microprocessors, microcontrollers, host processors, controllers, vehicle communication processors, and Application Specific Integrated Circuits (ASICs). It may be a dedicated processor for performing only the described method or it may be shared with other systems of the combustion engine or vehicle. The system processing device 56 may be included within the motor controller 54 or the device 56 may be implemented as a separate and independent processing device. The system processing device 56 executes various types of digitally stored instructions, such as software or firmware programs stored in memory. Communication between the

sensors

32, 48, the motor controller 54, and the system processing device 56 may be performed over a communication bus 58, such as a communication bus implemented using a Controller Area Network (CAN) protocol. However, it should be understood that other implementations are possible, wherein at least some of these elements may be implemented together on a printed circuit board.

Turning to fig. 5, a block diagram depicts an implementation of a cascade controller 500 implemented using the system processing device 56. The cascade controller 500 includes a primary control loop 600 that processes phase-related inputs and a secondary control loop 700 that processes inputs related to the angular velocity of the crankshaft 16. Both the primary control loop 600 and the secondary control loop 700 may be implemented as Proportional Integral (PI) controllers. The primary control loop 600 and the secondary control loop 70 may also be implemented using Proportional Integral Derivative (PID) controllers. The cascade controller 500 may receive a plurality of inputs for ultimately generating an output control signal that is sent to the motor controller 54 to adjust the angular velocity of the output shaft 46. These inputs may include a target phase of camshaft 18, an actual/measured phase of camshaft 18, a temperature value, a measured angular velocity of crankshaft 16, and a measured angular velocity of output shaft 46 of electric phaser motor 34. The input may be determined and communicated to the system processing device 56 as described above.

The main control loop 600 includes an error calculator 602, which error calculator 602 calculates a phase error between the measured camshaft angular position and the target camshaft angular position. Main control loop 502 also includes a proportional phase control element 604, an integral phase control element 606, a proportional temperature element 608, an integral temperature element 610, a main proportional multiplier 612, and a main integral multiplier 614. The phase error may be provided to a proportional phase control element 604 and an integral phase control element 606. The temperature inputs may be provided to a proportional temperature element 608 and an integral temperature element 610. The proportional element may generate an output proportional to the phase error and the integral element may calculate an integral output of the past phase error. The main scale multiplier 612 may receive outputs from the proportional phase control element 604, the proportional temperature element 608, and the phase error and generate an output signal. Main integral multiplier 614 may receive outputs from integral phase control element 606, integral temperature element 610, and the phase error. A main proportional multiplier 612 generates a main proportional output signal and a main integral multiplier 614 generates a main integral output signal. The main control loop 600 may also generate speed change commands for the electric phaser motor 34.

The secondary control loop 700 includes a crankshaft angular velocity divided by 2 acceleration change command summer 702, a speed limit regulator 704, a motor speed error calculator 706, a proportional speed element 708, a proportional temperature element 710, an integral speed element 712, an integral temperature element 714, a secondary proportional multiplier 716, a secondary integral multiplier 718, and an integral summer 720. The secondary control loop 700 receives a plurality of inputs. The inputs include the main integrated output signal, the calculated phase error, the speed change command, the measured angular velocity of the crankshaft 16, and the measured angular velocity of the output shaft 46. The angular velocity of the crankshaft may be provided to an electric phaser motor error calculator through a speed change command. The secondary control loop 700 may consider both the angular velocity of the crankshaft 16 and the commanded angular velocity of the output shaft 46. The motor speed summer 702 outputs a target speed signal for controlling the output shaft 46 based on the speed of the crankshaft 16 divided by 2 and the angular speed of the output shaft 46. The target speed signal and the measured angular velocity of the crankshaft 16 divided by 2 are input to a motor speed error calculator 706, which motor speed error calculator 706 may output a motor control command. The phase error is provided to a proportional velocity element 708 and an integral velocity element 712; the temperature is provided to proportional temperature element 710 and integral temperature element 714. The outputs of proportional speed element 708 and proportional temperature element 710 are provided to secondary proportional multiplier 716 along with the motor speed command. The outputs from the integral speed element 712 and the integral temperature element 714 are provided to a secondary integral multiplier 718 along with the motor speed command. The integral integrator adder 720 combines the outputs from the primary and secondary

integral multipliers

614, 718. The integral accumulator 722 stores the accumulated output of the integral adder 720.

The feed-forward module 800 may include a feed-forward temperature gain element 802, a feed-forward crankshaft angular velocity element 804, and a feed-forward summer 806. Module 800 may receive the angular velocity and temperature values of crankshaft 16 at a feed-forward crankshaft speed element 802 and a feed-forward speed gain element 804, respectively. The outputs from these elements may be passed to a feedforward adder 806 to generate a feedforward output signal. The main adder 900 receives outputs from the feedforward module 800, the main proportional multiplier 612, the secondary proportional multiplier 716, and the integral accumulator 722. These signals may be combined into an output control signal that is communicated to the motor controller 54 where it is used to control the output shaft 46.

It is to be understood that the foregoing is a description of one or more embodiments of the invention. The present invention is not limited to the specific embodiments disclosed herein, but is only limited by the following claims. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments as well as various changes and modifications to the disclosed embodiments will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to fall within the scope of the appended claims.

As used in this specification and claims, the terms "such as," "for example," "for instance," "such as," and "like," and the verbs "comprising," "having," "including," and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that listing is not to be considered as excluding other, additional components or items. Unless other terms are used in a context that requires a different interpretation, they should be interpreted using their broadest reasonable meaning.

Claims

1. An electrically actuated Variable Camshaft Timing (VCT) device cascade controller comprising:

a system processing device configured to receive input from one or more sensors and generate an output signal that is communicated to an electric phaser motor, wherein the system processing device:

(a) receiving data indicative of an angular position of a camshaft relative to an angular position of a crankshaft at a primary control loop;

(b) receiving data indicative of angular velocity of the crankshaft at a secondary control loop; and

(c) generating the output signal for controlling the electric phaser motor using the primary control loop and the secondary control loop.

2. The electrically actuated VCT device cascade controller of claim 1, further comprising receiving temperature values at the primary control loop and the secondary control loop.

3. The electrically actuated VCT device cascade controller of claim 1, further comprising generating a speed change command at the master control loop.

4. The electrically actuated VCT device cascade controller of claim 1, further comprising calculating a phase error at the main control loop.

5. The electrically actuated VCT device cascade controller of claim 1, wherein the cascade controller further comprises a proportional-integral configuration.

6. A method of controlling an electrically actuated Variable Camshaft Timing (VCT) device with a cascaded controller, the steps comprising:

(b) receiving data indicative of angular velocity of the crankshaft at a secondary control loop;

(c) generating an output signal for controlling the electric phaser motor using the primary control loop and the secondary control loop;

(d) transmitting the output signal to the electric phaser motor; and

(e) adjusting the camshaft angular position relative to the crankshaft angular position based on the output signal.

7. The method of claim 6, further comprising the step of receiving temperature values at the primary control loop and the secondary control loop.

8. The method of claim 6, further comprising the step of generating a speed change command at the primary control loop.

9. The method of claim 6, further comprising the step of calculating a phase error at the master control loop.

10. The method of claim 6, further comprising the step of implementing the cascaded controller in a proportional-integral configuration.