JP2011196300A - Variable valve train for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To notify that it is necessary to immediately learn a correlation when the presence or absence of the abnormality of the correlation between the turning angles of a motor shaft and a control shaft is detected and there is the abnormality, since when an electronic control unit (ECU) is reset due to momentary disconnection, there is a possibility that the learning value (for example, the reference position (0 degree) of the motor shaft) of the correlation is cleared.SOLUTION: The rotating shaft 71 of the motor 70 of a variable lift mechanism transmits driving force (torque) to the control shaft 66 through a driving force transmission mechanism (gear) 72. The motor 70 includes an MO sensor 36 detecting the turning angle of the motor shaft 71. The motor 70 further includes a current sensor 74 detecting a current value (drive current) for rotatively driving the motor. The turning angle of the motor shaft 71 and the turning angle of the control shaft 66 have a linear relationship. By the correlation, it is possible to calculate the turning angle of the control shaft 66 from the turning angle of the motor shaft 71.

Description

  The present invention relates to a variable valve mechanism provided in an internal combustion engine and capable of varying a lift amount of an intake valve by rotating a control shaft by a motor, and more particularly, a correlation between a rotation angle of a control shaft and a rotation angle of a motor shaft. It relates to detecting abnormalities.

  Conventionally, there has been 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 rotation 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.

JP 2009-36034 A

  When the electronic control unit (ECU) is reset due to a momentary disconnection or the like, the learning value of the correlation (for example, the reference position (0 degree) of the motor shaft) may be cleared. As a result, the rotation angle of the motor shaft In some cases, the rotation angle of the control shaft cannot be estimated.

  Therefore, it is necessary to detect whether an abnormality in the correlation between the rotation angles of the motor shaft and the control shaft has occurred due to instantaneous disconnection or the like.

  However, the apparatus of Patent Document 1 does not particularly take into consideration the detection of abnormality in the correlation between the rotation angles of the motor shaft and the control shaft.

  In view of the above, an object of the present invention is to detect whether or not there is an abnormality in the correlation between the rotation angles of the motor shaft and the control shaft, and to inform that it is necessary to quickly learn the correlation when there is an abnormality. And

The present invention provides a variable valve mechanism that is provided in an internal combustion engine and that can vary the lift amount of an intake valve by rotating a control shaft by a motor. The variable valve mechanism includes a current sensor that detects a drive current of the motor, an angle estimation unit that estimates the rotation angle θ _{1 of the} motor from the drive current when the motor holds the lift amount of the intake valve constant, and Is provided.

According to the present invention, during running of the vehicle, the motor can be estimated rotation angle theta ₁ from the drive current of the motor when the holding constant the amount of lift of the intake valve.

According to one aspect of the present invention, the angle sensor that detects the rotation angle θ ₂ of the motor, the detected rotation angle θ _{2 of the} motor, and the estimated rotation angle θ _{1 of the} motor are compared. Determination means for determining presence or absence of abnormality.

  According to an aspect of the present invention, it is possible to detect an abnormality of the angle sensor, that is, an abnormality in the correlation between the rotation angle of the motor shaft and the control shaft from the rotation angle of the motor.

According to one aspect of the present invention, a variable valve mechanism that is provided in an internal combustion engine and that can vary the lift amount of an intake valve by rotating a control shaft by a motor is provided. Its variable valve mechanism includes a current sensor for detecting the driving current of the motor, the angle estimating means motor estimates the rotational angle theta ₃ from the drive current of the control axis when held in the constant lift amount of the intake valve And comprising.

According to an embodiment of the present invention, during running of the vehicle, the motor can be estimated rotation angle theta ₃ of the control shaft from the drive current when holding constant the amount of lift of the intake valve.

According to one embodiment of the present invention, an angle sensor that detects a rotation angle θ _{2 of the} motor, an estimated rotation angle θ ₃ of the control shaft, and a rotation of the control shaft estimated from the detected rotation angle θ _{2 of the} motor. by comparing the angle theta _4, further comprising determining means for determining whether the angle sensor abnormality, the.

  According to an aspect of the present invention, it is possible to detect an abnormality in the angle sensor, that is, an abnormality in the correlation between the rotation angle of the motor shaft and the control shaft from the rotation angle of the control shaft.

1 is an overall configuration diagram of an internal combustion engine including a variable valve mechanism of the present invention and a control device thereof. It is a figure which shows an example of the variable lift mechanism of this invention. It is a schematic diagram which shows the relationship between the control shaft and motor shaft of the variable lift mechanism of this invention. It is a figure which shows the relationship between the rotation angle of the motor shaft of this invention, and the rotation angle of a control shaft. It is a flow for detecting an abnormality in the correlation between the rotation angle of the motor shaft and the rotation angle of the control shaft. It is a calculation flow of the integrated amount of the rotation angle of the motor shaft of this invention. It is a figure which shows the relationship between the rotation angle (integral amount) of the motor shaft of this invention, the output of MO sensor, and the rotation angle of a control shaft. It is a calculation flow of the estimated amount of the rotation angle of the motor shaft of this invention. It is a figure which shows the correspondence of the torque amount which hold | maintains the lift of the intake valve of this invention constant, and the estimated angle of a control shaft.

  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”) 10 is a computer including an input / output interface, a central processing unit (CPU), and a memory. The memory can store a computer program for realizing various controls of the vehicle and data necessary for executing the program. Programs for various controls according to the present invention, and data and maps used in executing the programs are stored in a memory. The ECU 10 receives data sent from each part of the vehicle, performs calculation, generates a control signal, and sends it to control each part of the engine.

  The engine 12 is, for example, a four-cylinder four-cycle engine, and one of the cylinders is schematically shown in the figure. The engine 12 is connected to an intake pipe 16 via an intake valve 14 and is connected to an exhaust pipe 20 via an exhaust valve 18. A fuel injection valve 22 that injects fuel in accordance with a control signal from the ECU 10 is provided in the intake pipe 16. Alternatively, the fuel injection valve 22 may be provided in the combustion chamber 24.

  The engine 12 sucks an air-fuel mixture of air sucked from the intake pipe 16 and fuel injected from the fuel injection valve 22 into the combustion chamber 24. The combustion chamber 24 is provided with an ignition plug 26 that discharges a spark in accordance with an ignition timing signal from the ECU 10. The air-fuel mixture is combusted by the spark from the spark plug 26. This combustion increases the volume of the air-fuel mixture and pushes the piston 28 downward. The reciprocating motion of the piston 28 is converted into the rotational motion of the crankshaft 30. In a four-cycle engine, one combustion cycle of the engine consists of intake, compression, combustion, and exhaust strokes. The piston 28 reciprocates twice per combustion cycle.

  In this embodiment, the continuously variable valve mechanism 31 includes a variable lift mechanism 32 and a variable phase mechanism 33. The variable lift mechanism 32 is a mechanism that can continuously change the lift amount of the intake valve 14 in accordance with a control signal from the ECU 10. An example of the variable lift mechanism 32 will be described later.

  The variable phase mechanism 33 is a mechanism that can continuously change the phase of the intake valve 14 in accordance with a control signal from the ECU 10. The variable phase mechanism 33 can be realized by any known method. For example, a method for electromagnetically controlling the phase of the intake valve to advance or retard has been proposed (see, for example, Japanese Patent Laid-Open No. 2000-227033).

  Alternatively, the variable lift mechanism 32 and the variable phase mechanism 33 may be configured integrally. Further, the present invention is not limited to these mechanisms that can continuously change the lift amount and phase, but can also be applied to mechanisms that can change the lift amount and phase in a stepwise manner.

  The ECU 10 is connected to a crank angle sensor 34 that detects the rotation angle of the crankshaft 30 of the engine 12 and a cam angle sensor 35 that detects the rotation angle of the camshaft to which the cam that drives the intake valve 14 of the engine 12 is coupled. The detection values of these sensors are supplied to the ECU 10. The crank angle sensor 34 generates one pulse (CRK pulse) every predetermined crank angle (for example, 30 degrees), and can specify the rotational angle position of the crankshaft 30 by the pulse. The cam angle sensor 35 generates a pulse (CYL pulse) at a predetermined crank angle position of a specific cylinder of the engine 12 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 cam shaft relative to the crank shaft is detected from the relative relationship between the TDC pulse output from the cam angle sensor 35 and the CRK pulse output from the crank angle sensor 34. In this embodiment, the phase CAIN has a value that increases as the angle of advance becomes zero with the most retarded angle being zero.

  Further, the continuously variable valve mechanism 31 is provided with an MO sensor 36 for detecting a rotation angle of a motor shaft that drives a control shaft, which will be described later, and the sensor 36 is connected to the ECU 10. The MO sensor 36 will be described later. The detection value of the MO sensor 36 is sent to the ECU 10.

  A throttle valve 42 is disposed in the intake pipe 16. The throttle valve 42 is a drive-by-wire (DBW) type throttle valve that is driven by an actuator (not shown) in accordance with a control signal from the ECU 10.

  A throttle valve opening sensor 44 is provided in the throttle valve 42 and outputs a signal corresponding to the throttle opening TH to the ECU 10.

  In the present embodiment, the amount of intake air to the engine 12 is controlled by controlling the lift amount of the intake valve 14 by the continuously variable valve mechanism 31 and controlling the intake pipe pressure through the control of the opening degree of the throttle valve 42. To control.

  An air flow meter 40 is installed on the upstream side of the throttle valve 42 of the intake pipe 16. The air flow meter 40 outputs an electric signal indicating the intake air amount to the ECU 10.

  An intake pipe pressure sensor 50 and an intake temperature sensor 54 are provided downstream of the throttle valve 42 of the intake pipe 16, and output electrical signals indicating the intake pipe absolute pressure PB and the intake air temperature TA to the ECU 10, respectively. An atmospheric pressure sensor 55 is installed at an arbitrary position outside the engine, and outputs an electric signal indicating the atmospheric pressure PA to the ECU 10.

  The intake pipe pressure can be expressed by an absolute pressure and a gauge pressure, where the gauge pressure represents a differential pressure of the intake pipe absolute pressure PB with respect to the atmospheric pressure PA, and is PB-PA (mmHg).

  Further, an engine water temperature sensor 56 for detecting the water temperature TW of the engine 12 is provided, and an electric signal indicating the engine water temperature is output to the ECU 10.

  A LAF sensor 48 is installed on the upstream side of the catalyst 46 in the exhaust pipe 20. The LAF sensor 48 outputs a signal proportional to the oxygen concentration in the exhaust gas to the ECU 10 over a wide range from lean to rich.

  FIG. 2 is a diagram showing a configuration of the variable lift mechanism 32 according to an embodiment of the present invention. As shown to (a), the cam shaft 61 provided with the cam 62, the control arm 65 supported by the cam holder so that rocking is possible centering on the support part 65a, and the control cam 67 which rocks the control arm 65 are included. A control shaft (control shaft) 66 provided and a control arm 65 are supported by a control cam 65 through a sub camshaft 63b so as to be swingable. And a rocker arm 64 for driving the intake valve 14. The rocker arm 64 is supported in the control arm 65 so as to be swingable by a rocker shaft 68.

  The sub cam 63 has a roller 63 a that abuts the cam 62, and swings about the sub cam shaft 63 b as the cam shaft 61 rotates. The rocker arm 64 has a roller 64a that contacts the sub cam 63, and the movement of the sub cam 63 is transmitted to the rocker arm 64 via the roller 64a. The control arm 65 includes a roller 65b that contacts the control cam 67, and swings about the support portion 65a by the rotation of the control shaft 66.

  (A), (b), and (c) show the high lift state, the middle lift state, and the low lift state of the intake valve 14, respectively, as indicated by arrows. By changing the position of the control arm 65 via the control shaft 66, it is possible to continuously transition between the high lift state as shown in (a) and the low lift state as shown in (c). In the state shown in (a), the movement of the sub cam 63 is transmitted to the intake valve 14 via the rocker arm 64, and the intake valve 14 opens to the maximum lift amount LFTMAX. In the state shown in (b), the amount of movement of the sub cam 63 to the intake valve 14 via the rocker arm 64 is smaller than that in (a), and therefore the valve is opened with a lift amount smaller than (a). In the state shown in (c), since the movement of the sub cam 63 is hardly transmitted to the rocker arm 64, the intake valve 14 is in a low lift state.

  An actuator motor is connected to the control shaft 66, and the lift amount of the intake valve 14 can be continuously changed by rotating the control shaft 66 by the motor.

  FIG. 3 is a schematic diagram showing the relationship between the control shaft of variable lift mechanism 32 and the motor (shaft) according to one embodiment of the present invention. A rotation shaft (hereinafter referred to as “motor shaft”) 71 of the motor 70 transmits a driving force (rotational force) to the control shaft 66 via a driving force transmission mechanism (gear) 72. The motor 70 is provided with the MO sensor 36 that detects the rotation angle of the motor shaft 71 already described in the description of FIG. The motor 70 is further provided with a current sensor 74 that detects a current value (drive current) for rotating the motor. Under the control of the ECU 10, detection signals from the MO sensor 36 and the current sensor 74 are sent to the ECU 10 at predetermined timings.

  Next, the relationship between the rotation angle of the motor shaft 71 and the rotation angle of the control shaft 66 and a method for detecting an abnormality in the correlation between the two will be described below.

  FIG. 4 is a diagram showing the relationship between the rotation angle of the motor shaft 71 and the rotation angle of the control shaft 66. This is an example in which the reduction ratio r of the driving force transmission mechanism (gear) 72 is set to 36. As shown in the figure, the rotation angle of the motor shaft 71 and the rotation angle of the control shaft 66 are in a linear relationship, and the rotation angle of the control shaft 66 is 180 degrees (half rotation) corresponds to the rotation angle of the motor shaft 71 is 6480 degrees. . That is, when the motor shaft 71 rotates once (360 degrees), the control shaft 66 rotates 10 degrees. Based on this correlation, the rotation angle of the control shaft 66 can be calculated from the rotation angle of the motor shaft 71.

  FIG. 5 is a diagram showing a flow for detecting an abnormality in the correlation between the rotation angle of the motor shaft and the rotation angle of the control shaft. The processing flow in FIG. 5 is executed by the ECU 10 at a predetermined cycle (for example, 100 μs).

  In step S1, it is determined whether or not the lift of the intake valve 14 of the variable lift mechanism 32 is kept constant. This determination is performed so that the correlation abnormality is not detected when the lift of the intake valve 14 is moving. If this determination is No, the process ends. When this determination is Yes, in step S2, the integrated amount θ1 of the rotation angle is calculated from the rotation angle of the motor shaft 71 which is the detection value of the MO sensor 36. The calculation flow of this angle θ1 will be described later.

  In step S <b> 3, the estimated amount θ <b> 2 of the rotation angle of the motor shaft 71 is calculated from the drive current of the motor 70 that is the detection value of the current sensor 74. The calculation flow of this angle θ2 will be described later.

  In step S4, it is determined whether or not the absolute value (| θ1−θ2 |) of the difference between the calculated angles θ1 and θ2 is larger than a predetermined angle. The predetermined angle can be arbitrarily set, but is, for example, 5 degrees. When this determination is Yes, in step S5, it is recognized that there is a correlation abnormality, that is, there is an abnormality (shift) in the detection angle of the MO sensor 36. In this case, the reference position (0 degree) of the motor shaft 31 and the control shaft 66 is reset (learned) using a method using a stopper (not shown) of the control shaft 66. If the determination in step S4 is No, it is certified in step S6 that there is no correlation abnormality.

  In step S4, instead of using the absolute value of the difference between the rotation angles θ2 and θ2 of the motor shaft 71, the rotation angle θ3 (= θ1 / r) of the control shaft is obtained from the angle θ1 using the relationship of FIG. The determination may be made using the absolute value (| θ3−θ4 |) of the difference from the estimated amount θ4 (θcs) of the rotation angle of the control shaft, which will be described later. In that case, it is determined whether or not the absolute value (| θ3-θ4 |) is larger than a predetermined angle.

  Next, a method of calculating the integrated amount θ1 of the rotation angle of the motor shaft 71 in step S2 of FIG. 5 will be described with reference to FIGS. In the following description, the accumulated amount θ1 of the rotation angle is expressed using the notation of MOTΘ, but both have the same meaning (θ1 = MOTΘ).

  FIG. 6 is a calculation flow of the integrated amount MOTΘ (= θ1) of the rotation angle of the motor shaft 71. FIG. 7 is a diagram showing the relationship among the rotation angle (integrated amount) A of the motor shaft 71, the output B of the MO sensor 36, and the rotation angle (horizontal axis) of the control shaft 66. The calculation flow in FIG. 6 is executed by the ECU 10 at a predetermined cycle (for example, 100 μs).

  In step S21 in FIG. 6, the current output value of the MO sensor 36 is set to Mnow. The output value of the MO sensor 36 takes a value of 0 to 359.9 degrees. In step S22, the difference between the current output value Mnow of the MO sensor 36 and the previous output value Mold is set to Mdelta. In step S23, it is determined whether or not the difference Mdelta is smaller than “−180”.

  If this determination is Yes, in step S24, 360 is added to the difference Mdelta to obtain a new Mdelta. In the example of FIG. 7, the flow (a) for calculating the new Mdelta is that the output B of the MO sensor 36 advances over 360 degrees from the previous angle 360 degrees before (for example, 350 degrees), and the current angle ( For example, it corresponds to (a).

  When the determination in step S23 is No, the process proceeds to step S25 to determine whether or not the difference Mdelta is greater than “180”. When this determination is Yes, in step S26, 360 is subtracted from the difference Mdelta to obtain a new Mdelta. In the example of FIG. 7, the flow (b) for calculating the new Mdelta returns from the previous angle (for example, 10 degrees) where the output B of the MO sensor 36 is 0 degrees beyond 0 degrees (360 degrees). This corresponds to (b) when the current angle (for example, 350 degrees) is reached.

  If the determination in step S25 is No, the process proceeds to step S27. In the example of FIG. 7, this flow (c) is when the output B of the MO sensor 36 in (c) moves between 0 degrees and 360 degrees (for example, the previous 260 degrees to the current 280 degrees) (c). It corresponds to.

  In step S27, Mdelta obtained in step S22, step S24 or step S26 is added to the rotation angle MOTΘ of the motor shaft 71 to obtain a new MOTΘ. In the case of (a), MOTΘ is as follows, for example, and an angle of 370 degrees on the graph (straight line) of the rotation angle (integrated amount) A of the motor shaft 71 in FIG. 7 can be obtained. That is, the integrated amount MOTΘ (= θ1) of the rotation angle of the motor shaft 71 can be obtained.

Step S22: Mdelta = 10−350 = −340
Step S24: Mdelta = −340 + 360 = 20
Step S27: MOTΘ = 350 + 20 = 370

Similarly, in the cases of (b) and (c), MOTΘ (= θ1) can be obtained.

  Finally, in step S28, the current output value Mnow of the MO sensor 36 is set as Mold to prepare for calculation in the next cycle.

  Next, a method for calculating the estimated amount θ2 of the rotation angle of the motor shaft 71 in step S3 in FIG. 5 will be described with reference to FIGS. FIG. 8 is a flowchart for calculating the estimated amount θ2 of the rotation angle of the motor shaft 71. FIG. 9 is a diagram showing a correspondence relationship between the torque amount for keeping the lift of the intake valve 14 constant and the estimated angle of the control shaft 66. The relationship of FIG. 9 is stored in the memory of the ECU 10 as one table, and is read out and used by the CPU of the ECU 10. The calculation flow in FIG. 8 is executed by the ECU 10 at a predetermined cycle (for example, 100 μs).

  In step S31 of FIG. 8, the engine speed NE is acquired. The engine speed NE is obtained by a conventional method using the CRK pulse, CYL pulse, or TDC pulse described in the description of FIG.

  In step S32, the amount of torque that keeps the lift of the intake valve 14 constant is acquired. Specifically, first, the drive current of the motor 10 is acquired from the current sensor 74. This drive current is a drive current (holding current) of the motor 10 when the lift of the intake valve 14 is held constant. Next, a holding torque (N · m) is obtained by multiplying the acquired drive current (mA) by a predetermined conversion coefficient or referring to a conversion table obtained in advance. The drive current (mA) and the holding torque (N · m) have a one-to-one relationship, and both increase as the lift amount of the intake valve 14 increases.

  In step S33, the estimated angle of the control shaft 66 is calculated from the earned engine speed NE and holding torque (N · m) using the relationship shown in FIG. For example, when the holding torque is T1 (N · m) and the engine speed is NE2 (rpm), as shown in FIG. 9, the estimated angle of the control shaft 66 is θcs. In FIG. 9, graphs for three rotation speeds NE1, NE2, and NE3 are shown. However, these are merely examples, and torque and control corresponding to each of a larger number of rotations are actually shown. The relationship with the estimated angle of the axis is stored in a memory as a table. As is apparent from FIG. 9, the holding torque tends to decrease as the engine speed NE increases.

  In step S34, the estimated amount θ2 of the rotation angle of the motor shaft 71 is calculated from the estimated angle of the control shaft 66 obtained. Specifically, for example, using the correlation between the rotation angle of the motor shaft 71 and the rotation angle of the control shaft 66 as shown in FIG. 4, the estimated angle θcs of the control shaft 66 is multiplied by the reduction ratio r, An estimated amount θ2 (= θcs × r) of the rotation angle of the motor shaft 71 is calculated. This estimated amount θ2 corresponds to an amount obtained by integrating the rotation angle of the motor shaft 71, in a manner similar to the integrated amount θ1 of the rotation angle of the motor shaft 71 described above.

  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.

10 ECU
14 Intake valve 31 Variable valve mechanism 32 Variable lift mechanism 36 MO sensor 66 Control shaft 70 Motor 71 Motor shaft 74 Current sensor

Claims (4)

A variable valve mechanism provided in an internal combustion engine and capable of varying a lift amount of an intake valve by rotating a control shaft by a motor,
A current sensor for detecting a driving current of the motor;
Variable valve mechanism and an angle estimating means that estimates the rotation angle theta ₁ of the motor from the drive current when the motor is held constant lift amount of the intake valve. An angle sensor for detecting a rotation angle θ _{2 of the} motor;
And the rotation angle theta ₂ of said detected motor, by comparing the rotational angle theta ₁ of the motor estimated, further comprising a determining means for determining whether the abnormality in the angle sensor, in claim 1 The variable valve mechanism described. A variable valve mechanism provided in an internal combustion engine and capable of varying a lift amount of an intake valve by rotating a control shaft by a motor,
A current sensor for detecting a driving current of the motor;
Variable valve mechanism and an angle estimating means that estimates the rotation angle theta ₃ of the control shaft from the drive current when the motor is held constant lift amount of the intake valve. An angle sensor for detecting a rotation angle θ _{2 of the} motor;
Comparing the estimated rotation angle θ _{3 of the} control shaft with the detected rotation angle θ _{4 of the} control shaft estimated from the detected rotation angle θ _{2 of the} motor, it is determined whether or not there is an abnormality in the angle sensor The variable valve mechanism according to claim 3, further comprising a determination unit that performs the determination.

Images