JP2011226331A - Variable valve device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To timely lean a reference position of a variable valve train by monitoring a drive current of an actuator that drives the variable valve train during the traveling of a vehicle.SOLUTION: A variable valve device includes: a variable valve train which can vary a lift amount of an intake valve of an internal combustion engine; an actuator which drives the variable valve train; a default mechanism having a biasing means that biases the variable valve train in one direction so as to hold a lift amount of the intake valve to a default position when the actuator is not driven; a position detecting means which detects a drive position of the variable valve train; a control device which controls the drive of the actuator based on the detected drive position of the variable valve train; and a current sensor which detects a drive current of the actuator. The control device determines that the lift amount of the intake valve corresponds to the default position when a variation in the detected drive current of the actuator is equal to or larger than a specified variation, and then learns the detected drive position of the variable valve train as a reference position of the variable valve train.

Description

  The present invention relates to a variable valve gear that is provided in an internal combustion engine and can vary the lift amount of an intake valve by rotation of a control shaft, and particularly relates to learning of reference positions of a control shaft and a motor shaft of the variable valve gear.

  Conventionally, there is a method of measuring (estimating) the rotation angle of a control shaft of a variable valve mechanism provided in an internal combustion engine from the rotation angle of a motor shaft (motor shaft) that rotationally drives the control shaft. In that case, it is necessary to learn the correlation between the rotation angles of the motor shaft and the control shaft, that is, to clarify the positional relationship between the two angles.

  Patent Document 1 discloses an apparatus for learning a reference position of an intake valve of an internal combustion engine. In this apparatus, the stopper of the control shaft is abutted against the fully closed stopper (fully closed position), and the correlation between the two is learned with the angle at that time as the reference position (0 degree) of the motor shaft and the control shaft.

  Patent Document 2 discloses a default device for an actuator for a variable valve mechanism. In this device, when the actuator of the variable valve mechanism fails, the pressed part of the lever pivoted around the support shaft is urged by the spring force of the coil spring, and the arm is pressed by the lever cam part to control it. The shaft is rotated in one direction to prevent the valve lift from becoming a predetermined value or less.

JP 2009-36034 A JP 2007-224777 A

  However, when an electronic control unit (ECU) reset occurs due to an instantaneous power interruption or the like, the learning value of the correlation may be cleared, and as a result, the rotation angle of the control shaft is estimated from the rotation angle of the motor shaft. It may not be possible.

  As a countermeasure in such a case, it is conceivable to learn the correlation again by the method exemplified in Patent Document 1, but since the acceleration / deceleration unintended by the driver occurs while the vehicle is traveling, Actually it is almost impossible unless the vehicle is stopped.

  Therefore, the present invention uses a default mechanism of an actuator for a variable valve mechanism as disclosed in, for example, Patent Document 2, and controls the rotation angle between the motor shaft and the control shaft due to an instantaneous power interruption while the vehicle is running. It is an object of the present invention to provide a variable valve apparatus that can be re-learned quickly even when the correlation learning value becomes invalid.

  The present invention relates to a variable valve mechanism that can vary the lift of an intake valve of an internal combustion engine, an actuator that drives the variable valve mechanism, and a variable motion that holds the lift of the intake valve at a default position when the actuator is not driven. A default mechanism having an urging means for urging the valve mechanism in one direction, a position detecting means for detecting the driving position of the variable valve mechanism, and controlling the driving of the actuator based on the detected driving position of the variable valve mechanism. And a current sensor that detects the drive current of the actuator. The control device determines that the lift of the intake valve is in the default position when the detected change amount of the drive current of the actuator is equal to or greater than the predetermined change amount, and variably moves the detected drive position of the variable valve mechanism. Learning as the reference position of the valve mechanism.

  According to the present invention, the reference position of the variable valve mechanism can be learned in a timely manner only by monitoring the drive current of the actuator that drives the variable valve mechanism while the vehicle is running. As a result, it is possible to improve the accuracy of learning and the accuracy of lift amount control of the intake valve.

1 is an overall configuration diagram of an internal combustion engine including a variable valve device of the present invention and a control device thereof. It is a figure which shows the structure of the variable valve apparatus of this invention. It is a figure which shows an example of the variable valve mechanism of this invention. It is a figure which shows the relationship between the control shaft and motor shaft of the variable valve apparatus of this invention. It is a figure explaining the default mechanism of this invention. It is a figure which shows the relationship between the angle (CS angle) of a control shaft, and the drive torque (CS torque) of the control shaft. It is the figure which showed the time change of the drive current of the motor angle of CS angle and an actuator. It is a figure which shows the learning flow of the reference position of this invention. It is a figure which shows the correlation of the rotation angle of a motor shaft, and the rotation angle of a control shaft.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of an internal combustion engine (hereinafter referred to as an engine) and its control device according to an embodiment of the present invention.

  An electronic control unit (hereinafter referred to as “ECU”) 1 is a computer including a central processing unit (CPU) and a memory. The memory can store a computer program for realizing various controls of the vehicle and data (including a map) necessary for executing the program. The ECU 1 receives a signal from each part of the vehicle and performs an operation according to data and a program stored in the memory to generate a control signal for controlling each part of the vehicle.

  The engine 2 is an engine having, for example, four cylinders. An intake pipe 3 and an exhaust pipe 4 are connected to the engine 2. The intake pipe 4 is provided with a throttle valve 5. The opening degree of the throttle valve 5 is controlled in accordance with a control signal from the ECU 1. By controlling the opening degree of the throttle valve 5, the amount of air taken into the engine 2 can be controlled. A throttle valve opening (θTH) sensor 6 for detecting the opening of the throttle valve is connected to the throttle valve 5, and this detected value is sent to the ECU 1.

  A fuel injection valve 7 is provided for each cylinder between the engine 2 and the throttle valve 5 and slightly upstream of the intake valve (not shown) of the engine 2. The fuel injection valve 7 is connected to a fuel pump (not shown). The fuel injection timing and the fuel injection amount of the fuel injection valve 7 are changed according to a control signal from the ECU 1.

  An air flow meter (AFM) 8 that detects the amount of air flowing through the intake pipe 3 is provided upstream of the throttle valve.

  An intake pipe absolute pressure (PBA) sensor 10 is provided downstream of the throttle valve 5 to detect the pressure in the intake pipe. An intake air temperature (TA) sensor 11 is provided downstream of the intake pipe absolute pressure sensor 10 to detect the temperature in the intake pipe. These detected values are sent to the ECU 1. The engine 2 is provided with an engine water temperature sensor 12 for detecting the engine water temperature TW, and the detected value of the sensor is sent to the ECU 1.

  The engine 2 has a first mechanism 21 capable of continuously changing the lift amount and opening angle (valve opening period) of the intake valve and a phase based on the crankshaft of the cam that drives the intake valve. The variable valve operating apparatus 20 having the second mechanism 22 to be changed automatically is provided. The phase of the cam that drives the intake valve is changed by the second mechanism 22, and thus the phase of the intake valve is changed.

  Connected to the ECU 1 are a crank angle sensor 13 for detecting the rotation angle of the crankshaft of the engine 1 and a cam angle sensor 14 for detecting the rotation angle of the camshaft to which a cam for driving the intake valve of the engine 1 is connected. The detection values of these sensors are supplied to the ECU 1. The crank angle sensor 13 generates one pulse (CRK pulse) every predetermined crank angle (for example, 30 degrees), and can specify the rotational angle position of the crankshaft by the pulse. The cam angle sensor 14 generates a pulse (CYL pulse) at a predetermined crank angle position of a specific cylinder of the engine 2 and a pulse (TDC pulse) at the top dead center (TDC) at the start of the intake stroke of each cylinder. . These pulses are used for detection of various control timings such as fuel injection timing and ignition timing, and engine speed NE. The actual phase CAIN of the camshaft is detected from the relative relationship between the TDC pulse output from the cam angle sensor 14 and the CRK pulse output from the crank angle sensor 13.

  The variable valve operating apparatus 20 is provided with a control shaft rotation angle sensor (CSA) sensor 15 for detecting the rotation angle position of the control shaft that controls the lift amount of the intake valve. The variable valve apparatus 20 further includes an MO sensor 16 that detects a rotation angle of a rotation shaft (hereinafter referred to as a “motor shaft”) of a motor 23 (FIGS. 2 and 4) of an actuator 24, which will be described later, and driving of the motor 23. A current sensor 17 for detecting current is provided. Detection signals from the sensors are sent to the ECU 1.

  The ECU 1 detects the operating state of the engine 2 in accordance with programs and data (including a map) stored in a memory in accordance with input signals from various sensors, and also detects a throttle valve 5, a fuel injection valve 7, a variable valve. A control signal for controlling the device 20 is generated.

  FIG. 2 shows a more specific configuration diagram of the variable valve gear 20. As shown in the figure, the variable valve apparatus 20 includes a first mechanism 21 that can continuously change the lift amount and opening angle of the intake valve (hereinafter simply referred to as lift amount), and the phase of the intake valve. , A second mechanism 22 that can continuously change, an actuator 24 that includes a motor 23 for continuously changing the lift amount LFT of the intake valve via the first mechanism, and the second In order to continuously change the phase of the intake valve via the mechanism, an actuator 26 including an electromagnetic valve 25 whose opening degree can be changed continuously is provided.

  As a parameter indicating the phase of the intake valve, the cam axis phase CAIN of the intake valve is used. Lubricating oil in the oil pan 28 is pressurized and supplied to the solenoid valve 25 by the oil pump 27. The motor 23 and the electromagnetic valve 25 operate according to a control signal from the ECU 1.

  The first mechanism 21 will be described with reference to FIG. As shown to (a), the cam shaft 31 provided with the cam 32, the control arm 35 supported by the cylinder head so that rocking is possible centering on the shaft 35a, and the control cam 37 which rocks the control arm 35 are provided. The control shaft 36 provided and the control arm 35 are supported so as to be swingable via a support shaft 33b, and are also driven by a cam 32 to swing and a sub cam 33. And a rocker arm 34 to be driven. The rocker arm 34 is swingably supported in the control arm 35.

  The sub cam 33 has a roller 33 a that contacts the cam 32, and swings about the shaft 33 b as the cam shaft 31 rotates. The rocker arm 34 has a roller 34a that contacts the sub cam 33, and the movement of the sub cam 33 is transmitted to the rocker arm 34 via the roller 34a.

  The control arm 35 has a roller 35b that contacts the control cam 37, and swings about the shaft 35a by the rotation of the control shaft 36. In the state shown in (a), since the movement of the sub cam 33 is hardly transmitted to the rocker arm 34, the intake valve 40 is maintained in a substantially fully closed state. In the state shown in (b), the movement of the sub cam 33 is transmitted to the intake valve 40 via the rocker arm 34, and the intake valve 40 opens to the maximum lift amount LFTMAX (for example, 12 mm).

  Therefore, the lift amount LFT of the intake valve 40 can be continuously changed by rotating the control shaft 36 by the motor 23 (FIG. 2) of the actuator 24. In this embodiment, the first mechanism 21 is provided with a CSA sensor 15 (FIG. 1) that detects the rotation angle position of the control shaft 36, and detects the rotation angle position CSA of the control shaft 36. The detected rotation angle position CSA is used as a parameter indicating the lift amount LFT.

  FIG. 4 is a diagram illustrating a relationship between a control shaft that controls the lift amount of the intake valve and a motor shaft of the actuator motor. The control shaft 36 is connected to the actuator 24 including the motor 23 shown in FIG. 2 via a worm gear mechanism. The worm gear mechanism includes a worm 43 fixed to the motor shaft 42 of the motor 23 of the actuator 24 and rotating integrally with the motor shaft 42, and a worm wheel 44 fixed to the control shaft 36 and rotated together with the control shaft 36. Has been. A worm gear that meshes with the worm 43 is formed on the outer periphery of the worm wheel 44.

  The motor 23 of the actuator 24 rotationally drives the motor shaft 42 according to the control signal from the ECU 1, and thereby rotationally drives the control shaft 36 via the worm gear mechanism. At this time, the rotation angle of the motor shaft 42 is detected by the MO sensor 16, the drive current of the motor 23 is detected by the current sensor 17, and a detection signal is sent to the ECU 1. Thus, the lift amount LFT of the intake valve 40 is controlled by controlling the rotation amount of the control shaft 36.

  Next, an embodiment of the default mechanism of the present invention will be described with reference to FIG. FIG. 5 is a side view of the default mechanism as viewed from one direction, and there is a similar (symmetric) configuration on the opposite side. Here, the operation of the configuration on this one side will be described, but the same operation is performed on the configuration on the opposite side at the same time.

  (A) is when the variable valve apparatus 20 is in a high lift state, and the control shaft 36 connected to the control arm 35 is stopped at the counterclockwise limit rotation position (rotation angle 94 degrees). At this time, the pressed portion 73b of the first lever 73 is in contact with the stopper 83 by the elastic force of the first coil spring 75 and stopped. The cam portion 73 c of the first lever 73 is separated from the roller 86 at the tip of the arm 85 of the control shaft 36.

  As shown in FIG. 5B, when the control valve 36 connected to the control arm 23 is rotated to the limit rotation position in the clockwise direction (rotation angle 0 degree) and the variable valve apparatus 20 is brought into the low lift state, the control valve 36 is rotated in the clockwise direction. The roller 86 at the tip of the arm 85 of the rotating control shaft 36 presses the cam portion 73 c of the first lever 73. As a result, the first lever 73 swings around the support shaft 72, and the pressed portion 73 b pushes up the first slider 78 to compress the first coil spring 75.

  In this state, if the actuator 24 is not driven due to a failure or the like and the control shaft 36 stops at the position (b), the intake valve 20 is fixed to a low lift (lift amount zero) state, so the engine is started. You will not be able to drive or drive. However, according to the present embodiment, as shown in (c), even when the actuator 24 is not driven, the compressed first coil spring 75 is pressed by the first lever 73 via the twelfth slider 78. By depressing the portion 73b, the first lever 73 rotates clockwise by a predetermined angle. As a result, the arm 85 whose roller 86 is pressed by the cam portion 73c of the first lever 73 rotates the control shaft 36 by a predetermined angle (36 degrees in the embodiment) in the counterclockwise direction. The required amount (for example, 2 mm) greater than zero is ensured, and the engine can be started and operated. The predetermined angle of the control shaft 36 corresponds to the default position referred to in the present invention.

  FIG. 6 is a diagram illustrating the relationship between the angle (CS angle) of the control shaft 36 and the drive torque (CS torque) of the control shaft 36. In the graph A showing the relationship between the two in FIG. 6, the CS torque suddenly reverses at the CS angle Θ1. The CS angle Θ1 corresponds to a predetermined angle of the control shaft 36 in FIG. 5C described above, and this sudden inversion phenomenon occurs every time the control shaft 36 passes the predetermined angle (CS angle Θ1). This inversion phenomenon will be further described.

  When the CS angle is smaller than Θ1, the arm 85 presses the cam portion 73c of the first lever 73 and the pressed portion 73b compresses the first coil spring 75 as illustrated in FIG. (CS torque) is required for the control shaft 36. The amount of torque decreases as the CS angle decreases (lower lift). This is because the contact angle between the cam portion 73c of the first lever 73 and the roller 86 becomes shallower as the lift becomes lower. The characteristics of the CS torque change according to the setting of the contact angle.

  When the CS angle is larger than Θ1, no load is generated by the default mechanism as illustrated in FIG. 5A, but the control cam 37 (FIG. 3) swings the control arm 35 (FIG. 3). Torque is required. Since the control arm 35 is urged by a lost motion spring (not shown) in the direction of low lift, the CS torque increases as the CS angle increases.

  In order to change the CS angle from Θ1 to small or large, it is necessary to overcome the biasing force in the reverse direction by the default mechanism (first coil spring 75) or the lost motion spring, depending on the direction of the change. Therefore, the CS torque suddenly reverses as shown in FIG. 6 at the CS angle Θ1.

  FIG. 7 is a diagram showing the change over time of the CS angle and the drive current of the motor 23 of the actuator 24. In FIG. 7, when the CS angle graph B passes through the position P of the predetermined angle Θ <b> 1 in the process of increasing with time, the motor current graph C rapidly reverses in the same manner as the CS torque change of FIG. 6. This sudden reversal phenomenon of the motor current is observed every time the control shaft 36 passes a predetermined angle (CS angle Θ1) for the same reason as in the case of CS torque. Therefore, by detecting this sudden change in the motor current, it can be recognized that the control shaft 36 is at the position P, that is, the predetermined angle (CS angle Θ1), and this position (angle) is determined as the reference position (learning). It is the intent of the present invention to learn as value).

  FIG. 8 is a diagram showing a learning flow of the reference position according to the present invention. The flow in FIG. 8 is executed by the ECU 1 at every predetermined timing. In step S10, the CSA sensor 15 detects the angle of the control axis (CS angle). In step S11, the current Im of the motor 23 of the actuator 24 is detected by the current sensor 17. In step S12, a difference ΔI between the current value of the current Im and the previous value at the previous timing is calculated. The current Im value detected at each timing is stored in the memory of the ECU 1 and is called up and used. In step S13, it is determined whether or not the current value difference ΔI is equal to or greater than a predetermined value ΔI1. The predetermined value ΔI1 is determined as one threshold value for detecting that a rapid change in the motor current time T1 in FIG. 7 has occurred. If this determination is No, the process ends. If Yes, the process proceeds to the next step S14.

  In step S14, the reference position is learned. Specifically, first, the CS angle detected in step S10 is correlated to the predetermined angle (CS angle Θ1) in FIG.

  FIG. 9 is a diagram showing the relationship between the rotation angle of the motor shaft 42 and the rotation angle of the control shaft 36. This figure (map) is stored in advance in the memory of the ECU 1. This is an example in which the reduction ratio r of the driving force transmission mechanism (worm 43 and worm wheel 44) is set to 36. As shown in the figure, the rotation angle of the motor shaft 42 and the rotation angle of the control shaft 36 are in a linear relationship, and the rotation angle of the control shaft 36 (half rotation) corresponds to the rotation angle 6480 degrees of the motor shaft 42. . That is, when the motor shaft 42 rotates once (360 degrees), the control shaft 36 rotates 10 degrees.

  Next, referring to the correlation diagram (map) in FIG. 9, the obtained predetermined angle (CS angle Θ1) of the control shaft 36 and the rotation angle of the motor shaft 42 are correlated. The obtained correlation between the two is stored in the memory of the ECU 1 and used as a reference value.

  Thus, according to the embodiment of the present invention, the drive current of the motor of the actuator that drives the variable valve mechanism is monitored while the vehicle is running, and each time it is detected that the amount of change exceeds a predetermined value. The reference position (angle) of the variable valve mechanism can be learned. As a result, it is possible to improve the learning accuracy of the reference position and the accuracy of lift amount control of the intake valve.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and can be modified and used without departing from the spirit of the present invention. For example, in the above-described embodiment, the correlation with the rotation angle of the motor shaft is acquired based on the detected CS angle. However, the rotation angle of the motor shaft is detected by the MO sensor 16, and the CS angle is detected based on the detected value. You may acquire the correlation with.

1 ECU
2 Engine 15 CSA sensor 16 MO sensor 17 Current sensor 20 Variable valve operating device 23 Motor 24 Actuator 36 Control shaft 40 Intake valve 42 Motor shaft

Claims (1)

A variable valve mechanism that can vary the lift of the intake valve of the internal combustion engine;
An actuator for driving the variable valve mechanism;
A default mechanism having biasing means for biasing the variable valve mechanism in one direction so as to hold the lift of the intake valve at a default position when the actuator is not driven;
Position detecting means for detecting a driving position of the variable valve mechanism;
A control device for controlling the drive of the actuator based on the detected drive position of the variable valve mechanism;
A variable valve device comprising a current sensor for detecting a drive current of the actuator,
The control device determines that the lift of the intake valve is at a default position when the detected change amount of the drive current of the actuator is equal to or greater than a predetermined change amount, and detects the detected drive position of the variable valve mechanism Is learned as a reference position of the variable valve mechanism.

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