JP5020766B2 - Variable valve operating device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently exhibits the performance of a variable valve train by operating the valve train to a heating limit function while preventing an electric actuator and a drive circuit thereof for operating the valve train from being superheated. <P>SOLUTION: The drive current of the electric actuator is detected to calculate effective currents in a plurality of preset periods. Each of the calculated effective currents Ie is compared with the corresponding threshold Limit-current. If any of the effective current is equal to or higher than the corresponding threshold, a drive current reduction control is performed to reduce the drive current of the electric actuator. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a variable valve operating apparatus for an internal combustion engine that includes a variable valve operating mechanism that is operated by an electric actuator and varies at least one of valve characteristics (for example, valve opening / closing timing and valve lift amount) of an intake valve and an exhaust valve.

In Patent Document 1, the temperature of the control device is predicted based on the energization current to the load driving element of the control device and the external temperature of the control device, and the predicted temperature exceeds the upper limit value of the operation guarantee temperature of the control device. It is described that it will transfer to the fail safe state which protects a control apparatus.
JP 2006-189990 A

According to the above prior art, the control device can be protected because the control device can shift to the fail-safe state before the temperature of the control device exceeds the upper limit value of the operation guarantee temperature.
However, since the control is based on the expected temperature finally reached by the control device, the temperature rise time constant, etc. are not considered, and in fact, fail-safe before the temperature of the control device approaches the upper limit of the guaranteed operating temperature. Since the transition to the state, that is, the transition to the fail-safe state is performed earlier, there is a problem that the performance of the control device cannot be used to near its limit. In particular, when the energization current temporarily increases, the state shifts to the fail-safe state at an earlier timing, and there is a possibility that the performance of the control device cannot be fully exhibited. For this reason, the effect which should originally be obtained is reduced or cannot be obtained.

  The present invention has been made paying attention to such problems, and prevents the electric actuator that operates the variable valve mechanism and its drive circuit from being overheated and protects them while maintaining its performance. An object of the present invention is to provide a variable valve operating apparatus for an internal combustion engine that can sufficiently exhibit the above.

For this reason, the variable valve operating apparatus for an internal combustion engine according to the present invention is configured to operate a variable valve mechanism that varies at least one of the valve characteristics of an intake valve or an exhaust valve by an electric actuator, A drive current detection unit that detects each sampling period; and an effective current calculation unit that can calculate an effective current in a plurality of periods based on the detected drive current. At one time, drive current reduction control for reducing the drive current of the electric actuator is executed, and the plurality of periods include a minimum period longer than the sampling period and at least one period obtained by multiplying the minimum period by a plurality of times. The threshold value corresponding to each period is set to a smaller value as the period is longer .

According to the variable valve system for an internal combustion engine having such a configuration, whether or not to reduce the drive current of the electric actuator is determined based on the comparison result between the effective current in each of the plurality of periods and the corresponding threshold value. The Here, the amount of heat generated in the electric actuator and its drive circuit varies depending on the applied current and the application time, so by using the effective current in a predetermined period, which is a substitute value, the heat generation state of the electric actuator and its drive circuit can be changed. It can be accurately grasped.

  Therefore, by setting the threshold value in advance in relation to the heat generation limit of the electric actuator and its drive circuit, the variable valve mechanism can be operated to the vicinity of the heat generation limit that the electric actuator and its drive circuit can withstand. Become. As a result, the variable valve operating apparatus can sufficiently exhibit its performance, and avoid the performance degradation and failure of the electric actuator and its drive circuit due to overheating.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a system configuration diagram of a vehicle internal combustion engine to which a variable valve operating apparatus according to the present invention is applied. In FIG. 1, an electronic control throttle 104 that opens and closes a throttle valve 103 b by a throttle motor 103 a is interposed in an intake pipe 102 of the internal combustion engine 101, and inside the combustion chamber 106 via the electronic control throttle 104 and the intake valve 105. Air (fresh air) is inhaled.

  An electromagnetic fuel injection valve 131 is provided in the intake port 130 on the upstream side of the intake valve 105 of each cylinder. The fuel injection valve 131 is opened by an injection pulse signal output from an engine control module (ECM) 114 described later, and injects fuel adjusted to a predetermined pressure. An air-fuel mixture is formed in the combustion chamber 106 by the fuel injected from the fuel injection valve 131 and the intake air.

The air-fuel mixture formed in the combustion chamber 106 is ignited and burned by a spark plug (not shown). The combustion exhaust is discharged from the combustion chamber 106 through the exhaust valve 107, purified by the front catalyst 108 and the rear catalyst 109, and then released into the atmosphere.
The exhaust valve 107 is opened and closed by a cam 111 provided on the exhaust camshaft 110 while keeping the valve characteristics (valve lift amount, valve operating angle and valve timing) constant.

On the other hand, the intake valve 105 is controlled by a variable lift mechanism (VEL-Variable valve Event and Lift-mechanism) 112 and a variable valve timing mechanism (VTC-Variable Timing Control-mechanism) 113 so that the valve characteristics (valve lift amount, valve operating angle and Valve timing) is variable.
Here, the VEL mechanism 112 is a mechanism that continuously varies the maximum valve lift amount of the intake valve 105 together with the valve operating angle. When the maximum valve lift amount is increased (decreased), the valve operating angle is accordingly increased. Increase (decrease). The VTC mechanism 113 is a mechanism that continuously changes the central phase of the valve operating angle of the intake valve 105 by changing the rotational phase of an intake valve drive shaft 3 to be described later with respect to the crankshaft 120. is there.

  Various controls (fuel injection control, ignition timing control, etc.) of the internal combustion engine 101 and drive control of the VTC mechanism 113 are executed by the ECM 114. Therefore, the ECM 114 includes an air flow meter 201 that detects the intake air amount of the engine 101, an accelerator opening sensor 202 that detects the amount of depression of the accelerator pedal, a crank angle sensor 203 that detects a crank rotation signal from the crankshaft 120, a throttle A throttle sensor 204 for detecting the opening degree of the valve 103b, a water temperature sensor 205 for detecting the coolant temperature of the engine 101, and a detected portion provided on a signal plate supported by an intake valve drive shaft 3 described later to detect the intake air A detection signal is input from a cam sensor 128 (see FIG. 2) that outputs a cam signal for each reference rotational position of the valve drive shaft 3. On the other hand, drive control of the VEL mechanism 112 is executed by a VEL controller 115 provided so as to be able to communicate with the ECM 114. The VEL controller 115 will be described later.

FIG. 2 is a perspective view mainly showing the structure of the VEL mechanism (variable valve mechanism) 112. However, this is merely an example, and the present invention is not limited to this structure.
In the present embodiment, the engine 101 has a pair of intake valves 105, 105 for each cylinder, and above these intake valves 105, an intake valve drive shaft 3 that is rotationally driven by a crankshaft 120 extends along the cylinder row direction. It is rotatably supported. A swing cam 4 that contacts the valve lifter 105a of the intake valve 105 and opens and closes the intake valve 105 is fitted on the intake valve drive shaft 3 so as to be relatively rotatable. The VEL mechanism 112 continuously changes the maximum valve lift amount and the valve operating angle of the intake valve 105 by changing the posture of the swing cam 4. In FIG. 2, the VEL mechanism 112 is shown only for one of the pair of intake valves 105, 105, and the other is omitted. The VTC mechanism 113 is disposed at one end of the intake valve drive shaft 3.

  As shown in FIGS. 2 and 3, the VEL mechanism 112 includes a circular drive cam 11 that is eccentrically fixed to the intake valve drive shaft 3 and a ring shape that is externally fitted to the drive cam 11 so as to be relatively rotatable. A link 12, a control shaft 13 extending substantially parallel to the intake valve drive shaft 3 in the cylinder row direction, a circular control cam 14 eccentrically fixed to the control shaft 13, and a relative rotation to the control cam 14 It has a rocker arm 15 that is externally fitted and has one end connected to the tip of the ring-shaped link 12, and a rod-shaped link 16 connected to the other end of the rocker arm 15 and the swing cam 4.

  The control shaft 13 is rotationally driven via a gear train 18 by a motor (electric actuator) 17. When the movable side stopper 13a provided integrally with the control shaft 13 contacts a fixed side stopper (not shown) provided on the cylinder head or the like, the minimum lift position / minimum operating angle position are set in advance. The corresponding rotation angle position is reached, and further rotation in the direction of decreasing the lift amount / operation angle is restricted. A stopper mechanism composed of such a movable side stopper and a fixed side stopper may be provided on the maximum lift side.

With such a configuration, when the intake valve drive shaft 3 rotates in conjunction with the crankshaft 120, the ring-shaped link 12 moves substantially in translation through the drive cam 11, and the rocker arm 15 moves around the axis of the control cam 14. The swing cam 4 swings through the rod-shaped link 16 and the intake valve 105 is driven to open and close.
Further, by controlling the drive of the motor 17 (electric actuator) to change the rotation angle of the control shaft 13, the axial center position of the control cam 14 serving as the rocking center of the rocker arm 15 changes, and the rocking cam 4 The posture changes. As a result, the valve lift amount and the operating angle of the intake valve 105 continuously change while the central phase of the operating angle remains substantially constant.

  A detection signal from an angle sensor 127 that detects the rotation angle of the control shaft 13 is input to the VEL controller 115. The VEL controller 115 makes the rotation angle of the control shaft 13 (corresponding to the actual valve characteristics) detected by the angle sensor 127 coincide with the target angle (corresponding to the target valve characteristics) corresponding to the operating state of the engine 101. The motor 17 is feedback controlled. Therefore, the VEL controller 115 corresponds to the “control unit” of the present invention.

  Here, in the present embodiment, a rotation angle sensor on the non-contact side is used as the angle sensor 127. Specifically, for example, as disclosed in Japanese Patent Application Laid-Open No. 2003-194580, it has a magnet attached to the end of the control shaft 13 and a magnetoelectric conversion means arranged to face the outer peripheral surface of the magnet. The sensor is configured to detect the rotation angle of the control shaft 13 based on the change in magnetic flux accompanying the rotation of the control shaft 13. However, the present invention is not limited to this. For example, a contact-type rotation angle sensor using a potentiometer may be used.

FIG. 4 shows the structure of the VEL controller 115.
In FIG. 4, the battery voltage is supplied to the VEL controller 115 and the power is supplied to the CPU 302 via the power supply circuit 301. The power supply voltage from the power supply circuit 301 is supplied to the angle sensor 127 via the buffer circuit 303, and the output (detection signal) of the angle sensor 127 is read into the CPU 302 via the input circuit 304.

In this embodiment, the angle sensor is provided in double (127a, 127b), and the input circuit is also in two systems (304a, 304b) corresponding to this.
A motor drive circuit 305 that drives a motor (electric actuator) 17 includes a pulse width modulation signal PWM in the forward direction, a port output, and a reverse direction in order to drive the motor in the forward direction and the reverse direction. Pulse width modulation signal PWM and port output are input.

The battery voltage is supplied to the motor drive circuit 305 via the relay circuit 306. The relay circuit 306 is ON / OFF driven by a relay drive circuit 307 controlled by the port output of the CPU 302.
In addition, the VEL controller 115 includes a current detection circuit (drive current detection unit) 308 that detects the drive current of the motor 17 and a communication circuit 309 that performs communication with the ECM 114.

Next, processing (fail safe processing) executed by the VEL controller 115 will be described.
The motor 17 and the motor drive circuit 305 generate heat when a current flows. If this heat generation amount increases and the motor 17 or the motor drive circuit 305 is overheated, its performance (including failure) is reduced, and the VEL mechanism 112 cannot be operated properly. Therefore, the VEL controller 115 estimates the heat generation of the motor 17 and the motor drive circuit 305, and when there is a possibility that the motor 17 and the motor drive circuit 305 are overheated, the drive current of the motor 17 is avoided so as to avoid this in advance. Drive current reduction control is performed to reduce the current. Specifically, a threshold value in each period of a plurality of periods is set in advance, an effective current in each period is calculated, and each of these values is compared with a corresponding threshold value. When this is the case, the drive current control is executed.

First, the threshold value in each period of the plurality of periods will be described.
The amount of heat generated by the motor 17 and the motor drive circuit 305 changes according to the effective current, but there is a time delay until the temperature of the motor 17 and the motor drive circuit 305 actually increases. For this reason, the motor 17 and the motor drive circuit 305 are obtained while sufficiently obtaining the effect of using the VEL mechanism 112 by shifting to more effective fail-safe processing, that is, fail-safe processing at a more appropriate timing. In order to prevent performance degradation and failure, it is necessary to consider effective current and elapsed time (current application time).

FIG. 5A shows the allowable effective current characteristics of the motor 17 and the motor drive circuit 305. In FIG. 5A, the “A” area is an area where the motor 17 and the motor drive circuit 305 do not exceed the limit temperature (operable area), and the “B” area is an area where the limit temperature exceeds the limit temperature (inoperable area). is there. The lower the effective current, the longer the motor 17 can be operated.
In the present embodiment, based on such allowable effective current characteristics, as shown in FIG. 5B, a plurality of periods are set, and thresholds (effective current upper limit values) in each period are set. It is determined whether or not to execute the drive current reduction control in accordance with the comparison result with the effective current in each period actually calculated.

  Here, as shown in FIG. 5B, in the present embodiment, as the “plurality of periods”, the first period (10 ms: minimum period), the second period (30 ms = 10 ms × 3), the third period Period (50 ms = 10 ms × 5), fourth period (150 ms = 10 ms × 15), fifth period (250 ms = 10 ms × 25), sixth period (750 ms = 10 ms × 75), seventh period Seven periods (1250 ms = 10 ms × 125: maximum period) are set, and threshold values {Limit-Current (1) to Limit-Current (7)} are set for the respective periods. However, the present invention is not limited to this, and the number of periods and the threshold value in each period may be set as appropriate.

6 and 7 are flowcharts showing the fail-safe process executed by the VEL controller 116. FIG.
FIG. 6 is a flowchart showing the calculation process of the effective current (Ie10) in 10 ms that is the first period (minimum period). This flow is started when the engine 101 is started, and is executed every predetermined sampling period (a period that can be a divisor of the minimum period (10 ms) is preferable, and in this embodiment, 2 ms).

In FIG. 6, in step S1, the drive current (I) of the motor (electric actuator) 17 is read and stored.
In step S2, it is determined whether or not 10 ms which is the minimum period has elapsed (whether or not the stored drive current (I) has become five). If the drive current (I) stored after 10 ms, which is the minimum period, has been stored, the process proceeds to step S3, and the drive current (I) stored without passing the minimum period, 10ms. If it is less than 5, this flow is terminated. Here, the number of the stored drive currents (I) is determined by the minimum period (10 ms) and the sampling period (2 ms) (minimum period / sampling period), and naturally changes if these differ. To do.

In step S3, an effective current (Ie10) is calculated. Specifically, each of the five drive currents (I _1-5 ) read (stored) so far is squared, and the square root of the value obtained by averaging these is calculated as the effective current (Ie10). And Hereinafter, the effective current (Ie10) in the first period (10 ms) is referred to as “first effective current”.
Ie10 = {(I ₁ ² + I ₂ ² + I ₃ ² + I ₄ ² + I ₅ ² ) / 5} ^1/2
In step S4, the first effective current (Ie10) calculated in step S3 is stored, and the driving current (I _1-5 ) stored so far is cleared.

Thus, the first effective current (Ie10) is calculated every 10 ms from the start of the engine 101, and these are sequentially stored (Ie10 _n (latest calculated value), Ie10 _n−1 , Ie10 _n−2 ,...・). Therefore, the VEL controller 115 functions as the “effective current calculation unit” of the present invention. Since the read drive current (I) is cleared when used for the calculation of the first effective current (Ie10), only five drive currents (I), that is, sampling currents are stored.

FIG. 7 is a flowchart of drive current reduction control. This flow is started when the engine 101 is started, and is executed every the minimum period (10 ms).
In FIG. 7, in step S11, the latest value (Ie10 _n ) of the first effective current Ie10 is read.
In Step S12, the read latest value (Ie10 _n ) of the first effective current is compared with the threshold value (Limit-Current (1)) at 10 ms which is the first period.

If Ie10 _n <Limit-Current (1), the process proceeds to step S13, and if Ie10 _n ≧ Limit-Current (1), the process proceeds to step S25.
In step S13, an effective current (hereinafter referred to as “second effective current”) Ie30 at 30 ms, which is the second period, is calculated. Specifically, the three most recent first effective currents (Ie10 _n , Ie10 _n−1 , Ie10 _n−2 ) are read, and the second effective current Ie30 is calculated according to the following equation based on these read values.
Ie30 = {(Ie10 _n ² + Ie10 _n-1 ² + Ie10 _n-2 ² ) / 3} ^1/2
In step S14, the second effective current Ie30 calculated in step S13 is compared with a threshold value (Limit-Current (2)) at 30 ms. If Ie30 <Limit-Current (2), the process proceeds to step S15. If Ie30 ≧ Limit-Current (2), the process proceeds to step S25.

In step S15, an effective current (hereinafter referred to as “third effective current”) Ie50 at 50 ms that is the third period is calculated. Specifically, the five most recent first effective currents (Ie10 _n , Ie10 _n-1 , Ie10 _n-2 , Ie10 _n-3 , Ie10 _n-4 ) are read, and based on these read values, The third effective current Ie50 is calculated.
Ie50 = {(Ie10 _n ² + Ie10 _n-1 ² +... + Ie10 _n-4 ² ) / 5} ^1/2
In step S16, the third effective current Ie50 calculated in step S15 is compared with the threshold value (Limit-Current (3)) at 50 ms. If Ie50 <Limit-Current (3), the process proceeds to step 17, and if Ie50 ≧ Limit-Current (3), the process proceeds to step S25.

In step S17, an effective current (hereinafter referred to as “fourth effective current”) Ie150 at 150 ms that is the fourth period is calculated. Specifically, the 15 most recent first effective currents (Ie10 _n , Ie10 _n−1 ,... Ie10 _n-14 ) are read, and based on these read values, the fourth effective current Ie150 is calculated by the following equation. Calculate.
Ie150 = {(Ie10 _n ² + Ie10 _n-1 ² +... + Ie10 _n-14 ² ) / 15} ^1/2 .

In step S18, the fourth effective current Ie150 calculated in step S17 is compared with the threshold value (Limit-Current (4)) at 150 ms. If Ie150 <Limit-Current (4), the process proceeds to step 19, and if Ie150 ≧ Limit-Current (4), the process proceeds to step S25.
In step S19, an effective current (hereinafter referred to as “fifth effective current”) Ie250 at 250 ms, which is the fifth period, is calculated. That is, the 25 most recent first effective currents (Ie10 _n , Ie10 _n−1 ,... Ie10 _n-24 ) are read, and the fifth effective current Ie250 is calculated according to the following equation based on these read values.
Ie250 = {(Ie10 _n ² + Ie10 _n−1 ² +... + Ie10 _n−24 ² ) / 25} ^1/2 .

In step S20, the fifth effective current Ie250 calculated in step S19 is compared with the threshold value (Limit-Current (5)) at 250 ms. If Ie250 <Limit-Current (5), the process proceeds to step 21. If Ie250 ≧ Limit-Current (5), the process proceeds to step S25.
In step S21, an effective current (hereinafter referred to as “sixth effective current”) Ie750 at 750 ms that is the sixth period is calculated. That is, the latest 75 first effective currents (Ie10 _n , Ie10 _n−1 ,... Ie10 _n-74 ) are read, and the sixth effective current Ie750 is calculated according to the following equation based on these read values.
Ie750 = {(Ie10 _n ² + Ie10 _n−1 ² +... + Ie10 _n−74 ² ) / 75} ^1/2 .

In step S22, the sixth effective current Ie750 calculated in step S21 is compared with a threshold value (Limit-Current (6)) at 750 ms. If Ie750 <Limit-Current (6), the process proceeds to step 23. If Ie750 ≧ Limit-Current (6), the process proceeds to step S25.
In step S23, an effective current (hereinafter referred to as “seventh effective current”) Ie1250 at 1250 ms, which is the seventh period, is calculated. That is, the latest 125 first effective currents (Ie10 _n , Ie10 _n−1 ,... Ie10 _n-124 ) are read, and the seventh effective current Ie1250 is calculated according to the following equation based on these read values.
Ie1250 = {(Ie10 _n ² + Ie10 _n-1 ² +... + Ie10 _n-124 ² ) / 125} ^1/2 .

In step S24, the seventh effective current Ie1250 calculated in step S23 is compared with the threshold value (Limit-Current (7)) at 1250 ms. Then, if Ie1250 <Limit-Current (7), this flow is terminated, and if Ie1250 ≧ Limit-Current (7), the process proceeds to step S25.
In step S25, since one of the effective currents in each set period is equal to or greater than the corresponding threshold value, it is determined that at least one of the motor 17 and the motor drive circuit 305 may be overheated, and the drive current Perform reduction control. Here, examples of such drive current reduction control include the following.

First, as the first drive current reduction control, when the valve characteristic of the intake valve 105 is controlled to the target valve characteristic, the current (actual) valve characteristic is (re) set as the target valve characteristic (in other words, Then, the target valve characteristic is changed to the current valve characteristic).
Accordingly, when it is determined that at least one of the motor 17 and the motor drive circuit 305 may be overheated, the valve characteristic is maintained at the valve characteristic (state) at that time, and the drive current of the motor 17 is Is reduced. This is because the driving force (driving current) of the motor 17 may be smaller than changing the valve characteristics if only the valve characteristics are maintained.

  In this case, it is preferable that the valve characteristic at that time is held for a predetermined time, and then the valve characteristic is changed to a predetermined valve characteristic (state) set in advance and held at the predetermined valve characteristic. This is because the influence on the operability of the engine 101 by fixing the valve characteristic as a valve characteristic that can cope with a wider operating range is minimized. For this reason, the predetermined valve characteristic is a reference valve characteristic of the intake valve 105 that can achieve both startability and operability, for example, the valve characteristic of the intake valve 105 that is set if the VEL mechanism 112 is not provided (a normal valve characteristic) Characteristic). However, the valve characteristic is not limited to this, and the predetermined valve characteristic may be a valve characteristic that can cope with an operating range wider than at least the valve operating characteristic that is initially maintained.

  Next, as the second drive current reduction control, when the valve characteristic of the intake valve 105 is controlled to the target valve characteristic, a predetermined valve characteristic set in advance is set as the target valve characteristic (that is, The target valve characteristic is changed to a predetermined valve characteristic set in advance). As described above, the predetermined valve characteristic set here is also a valve characteristic that can cope with a wider operating range, for example, the valve characteristic of the intake valve 105 that is realized when the VEL mechanism 112 is not provided. is there.

  In this case, when it is determined that at least one of the motor 17 and the motor driving circuit 305 may be overheated, the valve characteristic is retained after the valve characteristic is changed. Since there is a time lag before the temperature of the servo motor 121 and the motor drive circuit 305 rises, they do not immediately overheat. Therefore, the drive current of the motor 17 is reduced by changing the valve characteristic (predetermined valve characteristic) that can correspond to a wider operating range in advance and maintaining the predetermined valve characteristic (state).

  Further, as the third drive current reduction control, the drive current itself to the motor 17 is (directly) limited to less than a predetermined value. For example, when it is determined that at least one of the motor 17 and the motor drive circuit 305 may be overheated, the drive current is limited to a threshold value (Limit-Current (7)) in the maximum period 1250 ms. Thus, by setting the drive current to be less than the threshold value in the maximum period, it is possible to avoid the motor 17 and the motor drive circuit 305 from being overheated. In the third drive current reduction control, the drive current is limited to less than a predetermined value instead of immediately setting the drive current to 0 (stopping the drive of the motor 17). This is because when there is no risk of overheating, the control is returned (from the fail-safe process to the original state) so that the valve characteristic can be quickly controlled to the target valve characteristic.

  When it is determined that at least one of the motor 17 and the motor drive circuit 305 may be overheated by the above processing, drive current reduction control for reducing the drive current of the motor 17 is executed. For this reason, it is possible to prevent the motor 17 and the motor drive circuit 305 from being overheated, and to prevent performance degradation and failure of the motor 17 and the motor drive circuit 305. Here, the determination of whether or not to execute the drive current reduction control is effective in each period considering not only the instantaneous current value flowing through the motor 17 (and the motor drive circuit 305) but also the elapsed time (application time). Since it is performed based on the current, it becomes possible to operate the VEL mechanism 112 to near the heat generation limit that the motor 17 and the motor drive circuit 305 can withstand, and the effects obtained by mounting the VEL mechanism 112 can be sufficiently extracted. it can.

Moreover, in the said embodiment, the following effects can be acquired further.
In other words, whether or not at least one of the motor 17 and the motor drive circuit 305 is likely to be overheated is determined by comparing the effective current in a predetermined period with a corresponding threshold value. There is no need to provide a temperature sensor or the like for detecting the temperature of the circuit 305, and the cost can be reduced accordingly.

  In addition, the effective current in a plurality of periods is calculated, and the effective current in each period is compared with the corresponding threshold value to determine whether to execute the drive current reduction control. Therefore, the motor 17 and the motor drive circuit 305 are determined. Can be more reliably avoided from becoming overheated. Here, the plurality of periods include a first period (10 ms) which is a minimum period and a period obtained by multiplying the minimum period by an integer. Therefore, if the effective current is calculated and stored for each minimum period, the minimum period The effective current in all periods can be calculated based on the effective current at. For this reason, it is only necessary to store as many drive currents (sampled) as are necessary for calculating the effective current in the minimum period (five in this embodiment), and an increase in memory capacity can be prevented.

In the actual process of comparing each effective current with the corresponding threshold value, each threshold value is squared and the value before the root calculation (1/2 power) (hereinafter referred to as “effective current equivalent value”). ). This is for reducing the calculation load and efficiently performing the calculation process.
Specifically, in step S3 of FIG. 6, Ie10 ² (= (I ₁ ² + I ₂ ² + I ₃ ² + I ₄ ² + I ₅ ² ) / 5) is calculated, and this is set as the first effective current equivalent value. Store in S4. The first reads the effective current value corresponding IE10 ² in step S11 in FIG. 7, in step S12, the first effective current equivalent value I This read IE10 ^2, 2 squared value of the corresponding threshold {(Limit-Current (1)) ² } is compared. In step S13, the latest three first effective current equivalent values (Ie10 _n ² , Ie10 _n-1 ² , Ie10 _n-2 ² ) are read, and based on these, the second effective current equivalent value Ie30 ² (= _{^{(Ie10 n 2 + Ie10 n-}} 1 2 + Ie10 n-2 2) / 3) is calculated, in step S14, and the second effective current value corresponding Ie30 ^2, 2 squared value of the corresponding threshold {(Limit-current (2)) ² } is compared. Similarly, the third to seventh effective current equivalent values may be calculated and compared with the square values of the corresponding threshold values.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to this, and it goes without saying that various modifications are possible. Several modifications will be described below, but these are also included in the scope of the present invention.
In the above-described embodiment, the variable valve mechanism is the VEL mechanism 112 that varies the valve lift amount and valve operating angle of the intake valve 105, but the valve lift amount and valve operating angle of the exhaust valve 109 may be variable. Good. Further, any valve actuator may be used as long as it is operated by an electric actuator to change the valve characteristics, and is not limited to the VEL mechanism 112. For example, the present invention may be applied to a VTC mechanism that is operated by an electric actuator to change the rotation phase of the intake cam shaft or the exhaust cam shaft with respect to the crankshaft to vary the opening / closing timing of the intake valve or the exhaust valve.

  Further, the effective current is calculated and stored every first period (10 ms) which is the minimum period, and the drive current (sampling value) used for the calculation of the effective current is cleared. You may make it calculate from the drive current (sampling value) which memorize | stored the effective current in each period, without clearing (sampling value). In this case, when the effective current in the maximum period is calculated, the oldest drive current (sampling current value) may be cleared.

In addition to the first period (10 ms), the effective current is calculated and stored every second period (30 ms) and every third period (50 ms). The effective current during the period may be calculated. In this case, the effective current Ie150 in the fourth period (150 ms) is the five most recent second effective currents (Ie30 _n , Ie30 _n−1 ,... Ie10 _n-4 ) or the three most recent third currents. Based on the effective currents (Ie30 _n , Ie30 _n−1 , Ie10 _n-3 ), the effective current Ie250 in the fifth period (250 ms) is the five most recent third effective currents (Ie50 _n , Ie50 _{n). −1} ,... Ie50 _n−4 ). Similarly, the effective current Ie 750 in the sixth period (750 ms) is based on the 15 most recent third effective currents, and the effective current Ie 1250 in the seventh period (1250 ms) is the most recent 25 third effective currents. What is necessary is just to calculate based on an electric current.

  Further, in the above embodiment, one threshold value (Limit-Current (1) to (7)) is set for each period, but the threshold value is set according to the ambient temperature of the motor 17 or the motor drive circuit 305. You may comprise so that it may variably set. As shown in FIG. 8A, the higher the ambient temperature, the lower the effective current at which at least one of the motor 17 and the motor drive circuit 305 approaches the limit temperature. By doing so, it is possible to sufficiently extract the effect obtained by mounting the VEL mechanism 112 while more reliably avoiding the motor 17 and the motor drive circuit 305 from being overheated.

  Specifically, a temperature sensor 129 (indicated by a broken line in FIG. 2) for detecting the ambient temperature of the motor 17 and the motor drive circuit 305 is provided, and a detection signal of this temperature sensor is input to the VEL controller 115. To do. For example, as shown in FIG. 8 (b), the threshold value in each period is for high temperatures above a predetermined temperature (Limit-Current (1H) to (7H)) and low temperatures below a predetermined temperature (Limit-Current (1L) to (7L)) is set, and the VEL controller 115 switches the threshold based on the input detection signal (ambient temperature). Here, the ambient temperature is preferably an ambient temperature as close as possible to the motor 17 and the VEL controller 115, but may be any value that can be correlated with the ambient temperature, for example, an engine room temperature or an outside temperature can be substituted. May be.

  Furthermore, during the execution of the drive current reduction control, the motor 17 may be forcibly stopped when the effective current in each period becomes equal to or greater than the corresponding threshold value. In such a case, there is a possibility that the drive current reduction control may not be appropriately performed. Therefore, by stopping the drive of the motor 17, that is, by setting the drive current of the motor 17 to 0, the motor 17 and This is to ensure the protection of the motor drive circuit 305. Specifically, when any of the effective currents in each period is equal to or greater than the corresponding threshold value even when the drive current reduction control is executed, the effective current in each period is less than the corresponding threshold value by executing the drive current reduction control. However, when any of the effective currents again exceeds the corresponding threshold value, the relay circuit 306 is turned off to cut off the supply of the battery voltage to the motor drive circuit 305 or to generate the pulse width modulation signal PWM. The driving of the motor 17 is stopped as 0.

1 is a system configuration diagram of an internal combustion engine in an embodiment of the present invention. It is a perspective view which shows the structure of the VEL (Variable valve Event and Lift) mechanism in embodiment. It is a fragmentary sectional view of a VEL mechanism. It is a circuit block diagram which shows the structure of a VEL controller. It is a figure which shows the allowable effective current characteristic (a) of a DC servomotor and a motor drive circuit, and the threshold value (b) in each period. It is a flowchart which shows the calculation process of the effective current in the minimum period. It is a flowchart which shows drive current reduction control (fail safe process). It is a figure which shows the allowable effective current characteristic (a) of the DC servomotor and motor drive circuit by ambient temperature, and the threshold value (b) in each period by ambient temperature.

Explanation of symbols

  13 ... Control shaft, 17 ... Motor (electric actuator), 101 ... Internal combustion engine, 105 ... Intake valve, 107 ... Exhaust valve, 112 ... VEL mechanism (variable valve mechanism), 114 ... Engine control module (ECM), 115 ... VEL controller (control unit), 127 ... angle sensor, 129 ... temperature sensor, 302 ... CPU, 305 ... motor drive circuit, 306 ... relay circuit, 307 ... relay drive circuit, 308 ... current detection circuit

Claims (6)

A variable valve mechanism that varies at least one of the valve characteristics of the intake valve and the exhaust valve;
An electric actuator for operating the variable valve mechanism;
A variable valve operating apparatus for an internal combustion engine, comprising: a control unit that controls the electric actuator so that the valve characteristic becomes a target valve characteristic corresponding to an operating state of the engine.
A drive current detector for detecting the drive current of the electric actuator for each sampling period;
An effective current calculation unit capable of calculating an effective current in each of a plurality of periods based on the detected drive current, and
The control unit has a threshold corresponding to each period, and when the calculated effective current is equal to or greater than the corresponding threshold, executes a drive current reduction control for reducing the drive current of the electric actuator ,
The plurality of periods include a minimum period longer than the sampling period and at least one period obtained by multiplying the minimum period by a plurality of times.
The variable valve operating apparatus for an internal combustion engine, wherein the threshold corresponding to each period is set to a smaller value as the period is longer . The threshold value corresponding to each period, the electric actuator and the at least one of the variable valve device for an internal combustion engine according to claim 1, characterized in that is variably set according to the ambient temperature of the drive circuit of the electric actuator . 3. The variable valve operating apparatus for an internal combustion engine according to claim 1, wherein the control unit reduces the drive current of the electric actuator by maintaining the valve characteristic in a state at that time. 4. 4. The internal combustion engine according to claim 3 , wherein the control unit changes the valve characteristic to a predetermined state after the valve characteristic is maintained at the current state, and maintains the predetermined state. 5. Variable valve gear. The variable valve operating apparatus for an internal combustion engine according to claim 1 or 2 , wherein the control unit reduces the drive current of the electric actuator by maintaining the valve characteristic in a predetermined state set in advance. . 3. The internal combustion engine according to claim 1, wherein the control unit limits the drive current of the actuator to be greater than 0 and less than a threshold value in a maximum period among the plurality of periods. Variable valve gear.

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