JP4110534B2 - Variable valve control device for internal combustion engine - Google Patents

Description

  The present invention relates to a variable valve for an internal combustion engine provided with a hydraulically driven variable valve device that varies the valve opening / closing characteristics (valve timing, valve lift amount, valve opening period, etc.) of the intake valve or exhaust valve of the internal combustion engine with hydraulic pressure. The present invention relates to a control device.

  In recent years, in an internal combustion engine mounted on a vehicle, for example, as shown in Patent Document 1 (Japanese Patent Laid-Open No. 2000-179381), for example, an intake valve or an exhaust valve for the purpose of improving output, reducing fuel consumption, and reducing exhaust emissions. Some of them are equipped with a hydraulically driven variable valve device that can vary the valve timing by hydraulic pressure.

  In general, in order to reduce the exhaust emission of an internal combustion engine, the valve overlap amount is achieved by driving the variable valve device from the cold state before warming up the internal combustion engine to advance the valve timing of the intake valve. It is considered effective to increase the amount of internal EGR by increasing.

  However, the hydraulically driven variable valve device, when the temperature of the hydraulic oil (engine oil) is cold and the temperature of the hydraulic oil is low, the viscosity of the hydraulic oil increases and the fluidity of the hydraulic oil decreases. There is a characteristic that the property decreases. For this reason, increasing the target advance amount of the variable valve device from the cold and increasing the valve overlap amount reduces the valve overlap amount during sudden deceleration (decreases the internal EGR amount). Even if the angular amount is reduced, the valve overlap amount cannot be reduced quickly due to the response delay of the variable valve device, the internal EGR amount becomes excessive, the combustibility deteriorates, and the exhaust emission May worsen, or in the worst case, may lead to misfire or engine stall.

As a countermeasure against this, there is one in which the variable valve device is driven within a range in which the advance amount of the variable valve device can be limited by a predetermined drive limit value during cold to prevent adverse effects due to the response delay of the variable valve device. .
JP 2000-179381 A (5th page, etc.)

  By the way, it is inevitable that variations in the responsiveness of the variable valve device occur due to variations in manufacturing of the variable valve device, changes with time, types of hydraulic oil, deterioration with time, and the like. For this reason, in the conventional system, in consideration of such a variation range of the responsiveness of the variable valve device, the drive limit value is strictly set so that a problem due to response delay does not occur even in the variable valve device having the worst responsiveness. For this reason, the variable valve device having a standard response has a drawback that the drive limit value is limited more than necessary, and the performance of the variable valve control at the corner cannot be effectively exhibited. It was.

  The present invention has been made in view of such circumstances. Therefore, the object of the present invention is to set an appropriate drive limit value corresponding to the actual response of the variable valve device. An object of the present invention is to provide a variable valve control device for an internal combustion engine that can effectively exhibit the performance of variable valve control while preventing adverse effects due to delay in response of the device.

In order to achieve the above object, a variable valve control device for an internal combustion engine according to claim 1 of the present invention determines the responsiveness of the variable valve device by the responsiveness determining means, and the variable valve device by the drive limit value learning means. The first feature is to learn a drive limit value for limiting the drive amount of the variable valve device based on the responsiveness of the variable valve device, and further according to the temperature of the hydraulic oil of the variable valve device or information correlated therewith. The drive limit value is learned for each divided oil temperature region, and based on the learned value of the drive limit value, the drive limit is higher or lower than the oil temperature region where the drive limit value is learned. The learning value of the value is corrected, and the second characteristic is that the learning value of the drive limit value in the oil temperature region becomes larger as the oil temperature region becomes higher. . In this way, even if there is a variation in the responsiveness of the variable valve device, it is possible to set an appropriate drive limit value corresponding to the actual responsiveness of the variable valve device. It is possible to drive the variable valve device within the maximum range that can prevent the adverse effects due to the response delay of the control valve or a little narrower than that, making the variable valve control performance effective while preventing the adverse effects due to the response delay of the variable valve device It can be demonstrated.

Since the present invention learns the driving limit value for each oil temperature range which is divided in accordance with the information that correlates temperature or that of the hydraulic oil of the variable valve device, the variable valve in accordance with the oil temperature (temperature of the hydraulic oil) Corresponding to the change in the responsiveness of the apparatus, an appropriate drive limit value can be set for each oil temperature region, and the learning accuracy of the drive limit value can be improved.

  By the way, depending on the running pattern, temperature environment, etc., there may be a bias in the oil temperature region for determining the responsiveness of the variable valve device, so the drive limit value in the oil temperature region for which the responsiveness of the variable valve device is determined is learned. In the case of a system, in the oil temperature region where the responsiveness judgment frequency is high, the drive limit value learning frequency increases and the drive limit value learning accuracy increases, but in the oil temperature region where the responsiveness judgment frequency is low, the drive limit value The learning frequency of the drive limit value may be deteriorated because the learning frequency of the value is decreased.

As a countermeasure, in the present invention, based on the learning value of the drive limit value learned for each oil temperature region, the drive limit value on the higher temperature side or the lower temperature side than the oil temperature region where the drive limit value is learned. The learning value is corrected so that the learning value of the drive limit value in the oil temperature region increases as the oil temperature region becomes higher. In general, there is a relationship that the responsiveness of the variable valve device becomes better as the oil temperature becomes higher. Therefore, the drive limit value can be relaxed (the drive amount of the variable valve device can be increased) as the oil temperature becomes higher. . Using this relationship, when learning the drive limit value based on the responsiveness of the variable valve device in a certain oil temperature region, based on the learned value of the drive limit value in that oil temperature region, Alternatively, if the learning value of the drive limit value in the oil temperature region on the low temperature side is corrected so that the learned value of the drive limit value in the oil temperature region with the higher oil temperature is increased, the frequency of determining the responsiveness is increased. The learning accuracy of the drive limit value can be increased even in a low oil temperature region.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. On the downstream side of the air flow meter 14, a throttle valve 15 whose opening is adjusted by a DC motor or the like and a throttle opening sensor 16 for detecting the throttle opening are provided.

  Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. Yes. A spark plug 21 is attached to each cylinder of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each spark plug 21.

  The intake valve 28 of the engine 11 is provided with a hydraulically driven variable valve timing device 29 that varies the valve timing of the intake valve 28 with hydraulic pressure. The variable valve timing device 29 changes the valve timing of the intake valve 28 that is driven to open and close by the intake side camshaft by changing the rotation phase (camshaft phase) of the intake side camshaft with respect to the crankshaft. ing. The hydraulic circuit of the variable valve timing device 29 is supplied with hydraulic oil (engine oil) in an oil pan (not shown), and the hydraulic pressure is controlled by the hydraulic control valve 30 (OCV), so that the intake valve timing ( The valve timing of the intake valve 28) is controlled.

  On the other hand, the exhaust pipe 22 of the engine 11 is provided with a catalyst 23 such as a three-way catalyst that purifies CO, HC, NOx, etc. in the exhaust gas. / An exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting lean or the like is provided.

  A cooling water temperature sensor 25 for detecting the cooling water temperature is attached to the cylinder block of the engine 11, and a crank angle sensor 26 for outputting a crank angle signal for each predetermined crank angle is attached to the outer peripheral side of the crankshaft. ing. Based on the output signal of the crank angle sensor 26, the crank angle and the engine speed are detected.

  On the other hand, a cam angle sensor 31 that outputs a cam angle signal for every predetermined cam angle is attached to the outer peripheral side of the intake cam shaft. Based on the output signal of the cam angle sensor 31 and the output signal of the crank angle sensor 26, the actual advance value of the intake valve timing (actual advance value of the cam shaft phase) is detected.

  Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 27. The ECU 27 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 20 according to the engine operating state. The ignition timing of the spark plug 21 is controlled.

  Further, the ECU 27 executes a variable valve timing control program (not shown) to calculate the actual advance value of the intake valve timing based on the output signal of the cam angle sensor 31 and the output signal of the crank angle sensor 26, and A target advance value of the intake valve timing is calculated based on the engine operating state and the like, and the variable valve timing device 29 is feedback-controlled so that the actual advance value of the intake valve timing matches the target advance value. Control the amount of lap. At that time, in order to prevent an adverse effect due to the response delay of the variable valve timing device 29, the drive amount of the variable valve timing device 29 (by the card processing of the target advance value of the intake valve timing with a drive limit value Vmax described later) The advance value of the intake valve timing) is limited to the drive limit value Vmax or less, and the valve overlap amount is limited.

  The ECU 27 measures the response time T of the variable valve timing device 29 by executing the drive limit value learning programs shown in FIGS. 2 and 3, and based on the response time T, the variable valve timing device 29 A drive limit value Vmax for limiting the drive amount is learned. The drive limit value Vmax is set so that the drive permission range of the variable valve timing device 29 is within the maximum range where the adverse effect due to the response delay of the variable valve timing device 29 can be prevented or a range slightly narrower than that. The drive limit value Vmax is learned for each oil temperature region divided according to the oil temperature (the temperature of the hydraulic oil) and stored in a rewritable nonvolatile memory such as a backup RAM (not shown) of the ECU 27. Is done. Here, the oil temperature may be detected by an oil temperature sensor (not shown), or may be estimated based on the cooling water temperature detected by the cooling water temperature sensor 25. Alternatively, the coolant temperature may be used as it is as the substitute information of the oil temperature.

  Hereinafter, the processing contents of each program for driving limit value learning shown in FIGS. 2 and 3 executed by the ECU 27 will be described.

[Drive limit value learning program]
The drive limit value learning program shown in FIG. 2 is executed after an ignition switch (not shown) is turned on, for example, and serves as a drive limit value learning means in the claims. When this program is started, first, in step 101, it is determined whether or not the backup power from an in-vehicle battery or the like (not shown) is turned off while the engine is stopped.

  If it is determined that the backup power supply is turned off, it is determined that the learning value of the drive limit value Vmax stored in the rewritable nonvolatile memory such as the backup RAM of the ECU 27 has disappeared, and the process proceeds to step 102. Using the table of initial values of the drive limit value Vmax shown in FIG. 4, the initial value a1 is set to the drive limit value Vmax (i) in each oil temperature region divided according to the oil temperature. Here, (i) in the drive limit value Vmax (i) is a number set according to the oil temperature region, and means any one of (1) to (m).

  The table of initial values of the drive limit value Vmax shown in FIG. 4 is set so that the drive limit values Vmax (i) in each oil temperature region are all set to the same initial value a1 (for example, the minimum value). It is remembered. This initial value a1 is set so as not to cause a problem due to a response delay even when the response is the worst in consideration of the variation range of the response of the variable valve timing device 29.

  When the initial value a1 is set to the drive limit value Vmax (i) of each oil temperature region in this step 102, the learning value table of the drive limit value Vmax shown in FIG. The initial value a1 is set as the learning value of the drive limit value Vmax (i).

  On the other hand, if it is determined in step 101 that the backup power supply is not turned off, it is determined that the learning value of the drive limit value Vmax is stored in a rewritable nonvolatile memory such as the backup RAM of the ECU 27. Thus, the process skips the process of setting the initial value a1 to the drive limit value Vmax (the process of step 102) and proceeds to step 103.

  In step 103, it is determined whether or not the engine start is completed. When it is determined that the engine start is completed, the process proceeds to step 104, and a learning value table of the drive limit value Vmax shown in FIG. 5 is used. Then, the learning value a (n) of the drive limit value Vmax (i) in the oil temperature range corresponding to the current oil temperature is calculated. Here, the oil temperature may be detected by an oil temperature sensor (not shown), or may be estimated based on an output signal of the cooling water temperature sensor 25 or the like.

  In the learning value table of the drive limit value Vmax shown in FIG. 5, the learning value a (n) of the drive limit value Vmax (i) is set for each oil temperature region divided according to the oil temperature, and the backup RAM of the ECU 27 is set. Is stored in a rewritable nonvolatile memory. Here, (n) in the learning value a (n) is a number indicating the magnitude of the learning value a, and means any one of (1) to (z).

  Thereafter, the process proceeds to step 105, where the actual advance value Vcurrent of the intake valve timing is calculated based on the output signal of the cam angle sensor 31 and the output signal of the crank angle sensor 26, and then the process proceeds to step 106, where the actual advance value is obtained. Whether or not Vcurrent coincides with the drive limit value Vmax (i) [the target advance value is guarded with the drive limit value Vmax (i), and the target advance value = drive limit value Vmax (i). Whether or not] is determined.

  When it is determined that [target advance angle value = drive limit value Vmax (i)] in which the actual advance value Vcurrent matches the drive limit value Vmax (i), the routine proceeds to step 107 and sudden deceleration (not shown) is performed. By executing the operating state determination program, it is determined whether or not the vehicle is in the rapid deceleration operating state, for example, as shown in FIG. 6, the target advance value is the latest from the drive limit value Vmax (i) within a predetermined time Δt. Judgment is made based on whether or not the angular position has been changed.

  Thereafter, the process proceeds to step 108, where it is determined whether or not the vehicle is suddenly decelerated based on the determination result of the rapid deceleration operation state determination process (step 107). As the response time T of the variable valve timing device 29, for example, the actual advance value Vcurrent is 90% of the change amount of the target advance value [change amount from the drive limit value Vmax (i) to the most retarded position]. Measure the time it took to change. The process of step 109 serves as a responsiveness determination means in the claims.

  Thereafter, the process proceeds to step 110, where it is determined whether or not the response time T is equal to or shorter than the determination value t. The determination value t is set to a value t (n) corresponding to the learning value a (n) of the drive limit value Vmax (i) using the determination value t table shown in FIG. Response time that can prevent adverse effects (deterioration of exhaust emission, misfire, engine stall, etc.) due to response delay of the variable valve timing device 29 when the target advance value changes from the drive limit value Vmax (i) to the most retarded position. The maximum value or a value slightly smaller than that is set.

  If it is determined in step 110 that the response time T is less than or equal to the determination value t, the process proceeds to step 111, where the drive limit value Vmax (i) is a value that is larger by one step than the current value a (n). The driving permission range of the variable valve timing device 29 is expanded by changing to a (n + 1). On the other hand, if it is determined that the response time T is greater than the determination value t, the process proceeds to step 112, where the drive limit value Vmax (i) is a value a (n) that is smaller by one step than the current value a (n). -1) to reduce the drive permission range of the variable valve timing device 29. As a result, the drive limit value Vmax (i) is set so that the drive permission range of the variable valve timing device 29 is within the maximum range where the adverse effect due to the response delay of the variable valve timing device 29 can be prevented or a range slightly narrower than that. .

  Thereafter, the process proceeds to step 113, where the learning value of the drive limit value Vmax (i) in the current oil temperature region (the oil temperature region in which the response time T is determined) in the learning value table of the drive limit value Vmax shown in FIG. Is updated with the learning value of the current drive limit value Vmax (i).

  Thereafter, the routine proceeds to step 114, where a drive limit value update program shown in FIG. 3 to be described later is executed, based on the drive limit value Vmax (i) in the current oil temperature region (the oil temperature region in which the response time T is determined). Thus, the drive limit value in the oil temperature region on the higher temperature side and the oil temperature region on the lower temperature side is corrected and updated.

  Thereafter, the process proceeds to step 115, where it is determined whether or not the engine is stopped. If it is determined that the engine is not stopped (engine is running), the processing of steps 104 to 115 is repeated. When finished, exit this program.

[Drive limit value update program]
Next, the processing contents of the drive limit value update program shown in FIG. 3 executed in step 114 of FIG. 2 will be described. When this program is started, first, in step 201, k is set to an initial value i, and then the process proceeds to step 202 where the drive limit value Vmax in the current oil temperature region (the oil temperature region in which the response time T is determined). It is determined whether or not (i) is greater than the previous drive limit value Vmaxold (i), that is, whether or not the drive limit value Vmax (i) in the current oil temperature region has been updated in the increasing direction.

  As a result, when it is determined that the drive limit value Vmax (i) in the current oil temperature region is updated in the increasing direction, the process proceeds to step 203, where the drive limit value Vmax (k) in the current oil temperature region is It is determined whether or not it is larger than the drive limit value Vmax (k + 1) in the oil temperature region on the high temperature side by one step.

  If the drive limit value Vmax (k) in the current oil temperature region is larger than the drive limit value Vmax (k + 1) in the high temperature side oil temperature region, the routine proceeds to step 204 and the drive limit value shown in FIG. In the learned value table of Vmax, the learned value of the drive limit value Vmax (k + 1) in the oil temperature region on the high temperature side is set to the learned value of the drive limit value Vmax (k) in the current oil temperature region or slightly less. Update with a larger value.

  Thereafter, the process proceeds to step 205, the value of k is increased by “1”, and then the process proceeds to step 206 to determine whether or not k has reached the upper limit value m. If k has not yet reached the upper limit value m, the process returns to step 203, where the drive limit value Vmax (k) in the low temperature side oil temperature region is one step higher than the drive limit value in the high temperature side oil temperature region. If it is larger than Vmax (k + 1), the learned value of the drive limit value Vmax (k + 1) in the oil temperature region on the high temperature side is set to the learned value of the drive limit value Vmax (k) in the oil temperature region on the low temperature side or The process of updating with a value slightly larger than that is repeated (steps 203 to 206).

  In this way, based on the drive limit value Vmax (i) in the current oil temperature region (the oil temperature region in which the response time T is determined), the drive limit value Vmax (i +) in the oil temperature region on the higher temperature side. By correcting and updating 1) to Vmax (m), the drive limit values Vmax (i + 1) to Vmax (m) in the oil temperature region higher than the current oil temperature region become the current oil temperature. Correction is made so that the drive limit value Vmax (i) in the region is greater than or equal to.

  On the other hand, when it is determined in step 202 that the drive limit value Vmax (i) in the current oil temperature region has been updated in the decreasing direction, the process proceeds to step 207 and the drive limit value Vmax ( It is determined whether or not k) is smaller than the drive limit value Vmax (k-1) in the oil temperature region on the low temperature side by one step.

  If the drive limit value Vmax (k) in the current oil temperature region is smaller than the drive limit value Vmax (k-1) in the low temperature side oil temperature region, the routine proceeds to step 208 and the drive limit value shown in FIG. In the learned value table of Vmax, the learned value of the drive limit value Vmax (k-1) in the low temperature side oil temperature region is set to the learned value of the drive limit value Vmax (k) in the current oil temperature region or slightly less. Update with a smaller value.

  Thereafter, the process proceeds to step 209, the value of k is decreased by “1”, and then the process proceeds to step 210 to determine whether or not k has reached the lower limit value 1. If k has not yet reached the lower limit value 1, the process returns to step 207, where the drive limit value Vmax (k) in the oil temperature region on the high temperature side is the drive limit value in the oil temperature region on the low temperature side by one step. If it is smaller than Vmax (k−1), the learned value of the drive limit value Vmax (k−1) in the low temperature side oil temperature region is set to the learned value of the drive limit value Vmax (k) in the high temperature side oil temperature region or The process of updating with a value slightly smaller than that is repeated (steps 207 to 210).

  In this way, based on the drive limit value Vmax (i) in the current oil temperature region (the oil temperature region in which the response time T is determined), the drive limit value Vmax (i− By correcting and updating 1) to Vmax (1), the drive limit values Vmax (i-1) to Vmax (1) in the oil temperature region lower than the current oil temperature region become the current oil temperature. It is corrected so as to be equal to or less than the drive limit value Vmax (i) in the region.

  Through the above processing, as shown in FIG. 8, the learning correction is performed so that the drive limit value Vmax increases as the oil temperature increases and the responsiveness of the variable valve timing device 29 improves. Increase the drive permission range.

  In the present embodiment described above, the response time T of the variable valve timing device 29 is measured, and the drive limit value Vmax of the variable valve timing device 29 is learned based on the response time T. Therefore, the variable valve timing device 29 Even if there is a situation in which the responsiveness of the variable valve timing device 29 varies due to variations in manufacturing, changes over time, types of hydraulic oil, deterioration over time, etc., the actual responsiveness of the variable valve timing device 29 is supported. An appropriate drive limit value Vmax can be set. As a result, it becomes possible to drive the variable valve timing device 29 within the maximum range that can prevent adverse effects due to the response delay of the variable valve timing device 29 or a slightly narrower range, and the exhaust emission reduction effect by the variable valve timing control can be sufficiently achieved. In addition, it is possible to prevent adverse effects (deterioration of exhaust emission, misfire, engine stall, etc.) due to response delay of the variable valve timing device 29 during sudden deceleration during cold weather.

  In addition, in this embodiment, since the drive limit value Vmax is learned for each oil temperature region divided according to the oil temperature, the responsiveness of the variable valve timing device 29 changes according to the oil temperature. Correspondingly, an appropriate drive limit value Vmax can be set for each oil temperature region, and the learning accuracy of the drive limit value Vmax can be improved.

  By the way, depending on the traveling pattern, temperature environment, etc., there may be a bias in the oil temperature region for determining the response time T of the variable valve timing device 29. In the case of a system that learns the drive limit value Vmax, as shown in FIG. 9, in the oil temperature region where the determination frequency of the response time T is high, the learning frequency of the drive limit value Vmax increases and the drive limit value Vmax is quickly and appropriately set. However, in the oil temperature region where the determination time of the response time T is low, the learning frequency of the drive limit value Vmax may decrease and the drive limit value Vmax may not be easily set to an appropriate value.

  In this regard, in the first embodiment, when the drive limit value Vmax is learned based on the response time T of the variable valve timing device 29 in a certain oil temperature region, it is determined based on the drive limit value Vmax in that oil temperature region. By correcting and updating the drive limit value Vmax in the oil temperature region on the higher temperature side and the lower temperature side, the oil temperature becomes higher and the responsiveness of the variable valve timing device 29 is improved as shown in FIG. Since the drive limit value Vmax is corrected so as to increase, even in the oil temperature region where the determination time of the response time T is low, the drive limit value Vmax can be quickly brought close to the appropriate value.

As a result, the drive limit value Vmax can be smoothly changed with respect to the change in the oil temperature, so that it is possible to prevent the variable valve timing device 29 from changing suddenly when the oil temperature changes. It is possible to prevent exhaust emission and drivability from deteriorating due to sudden fluctuations.
In the above embodiment, the drive limit value Vmax is set for each oil temperature region. However, only the drive limit value Vmax in a region below a predetermined oil temperature (for example, 0 ° C. or less) may be set. .

  Further, in the above embodiment, as the response time T of the variable valve timing device 29, the time required for the actual advance value Vcurrent to change by 90% of the change amount of the target advance value during rapid deceleration is measured. However, the responsiveness determination method of the variable valve timing device 29 may be changed as appropriate. For example, when the target advance value is forcibly changed, the actual advance value Vcurrent changes by a predetermined amount. It is also possible to measure the time required for the change and the rate of change.

  In the above embodiment, the oil temperature detected by the oil temperature sensor, the oil temperature estimated based on the output signal of the cooling water temperature sensor 25, etc. is used. At least one of air temperature, intake air temperature, and the like may be used.

  In the above embodiment, the present invention is applied to a variable valve timing device that varies the valve timing of the intake valve. However, the present invention relates to a variable valve device that varies the valve lift amount and valve opening period of the intake valve, exhaust gas, and the like. The present invention can be widely applied to a hydraulically driven variable valve device such as a variable valve device that varies a valve opening / closing characteristic (at least one of valve timing, valve lift amount, and valve opening period).

It is a schematic block diagram of the whole engine control system in one Example of this invention. It is a flowchart which shows the flow of a process of a drive limiting value learning program. It is a flowchart which shows the flow of a process of a drive limiting value update program. It is a figure which shows notionally the table of the initial value of the drive limiting value Vmax. It is a figure which shows notionally the table of the learning value of drive limiting value Vmax. It is a time chart for demonstrating the determination method of the rapid deceleration driving | running state. It is a figure which shows notionally the table of the judgment value t. It is a figure which shows the execution example of the drive limit value learning of a present Example. It is a figure which shows the execution example of the drive limit value learning of a comparative example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 15 ... Throttle valve, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 27 ... ECU (responsiveness determination means, drive limit value learning means), 28 ... Intake valve, 29 ... Variable valve timing device

Claims (1)

In a variable valve control device for an internal combustion engine comprising a hydraulically driven variable valve device that varies the valve opening / closing characteristics of an intake valve or an exhaust valve of the internal combustion engine with hydraulic pressure,
Responsiveness determining means for determining the responsiveness of the variable valve device;
Drive limit value learning means for learning a drive limit value for limiting the drive amount of the variable valve device based on the responsiveness of the variable valve device determined by the responsiveness determination means;
The drive limit value learning means learns the drive limit value for each oil temperature region divided according to the temperature of hydraulic oil of the variable valve device or information correlated therewith, and based on the learned value of the drive limit value Thus, the learning value of the drive limit value on the higher temperature side or the lower temperature side than the oil temperature region in which the drive limit value has been learned is corrected, and the oil temperature region increases as the oil temperature region becomes higher. A variable valve control device for an internal combustion engine, wherein the learning value of the drive limit value is corrected so as to increase.

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