JP5761572B2 - Control device for electric variable valve timing device - Google Patents

Description

  The present invention relates to a control device for an electric variable valve timing device that changes a valve timing of an internal combustion engine by a motor.

  In recent years, internal combustion engines mounted on vehicles have adopted variable valve timing devices that change the valve timing (open / close timing) of intake valves and exhaust valves for the purpose of improving output, reducing fuel consumption, and reducing exhaust emissions. is there. Currently, a variable valve timing device in practical use is a valve of an intake valve or an exhaust valve that is driven to open and close by a camshaft by changing the rotation phase (camshaft phase) of the camshaft with respect to the crankshaft by a motor or hydraulic pressure. There are many things that change the timing.

  In an electric variable valve timing device using a motor as a drive source, for example, as described in Patent Document 1 (Japanese Patent No. 4678545), an oil temperature (lubricating oil temperature) after the engine is started. In some cases, the current flowing to the motor is made larger than the normal value until the temperature reaches a predetermined temperature, thereby suppressing the deterioration of the responsiveness of the variable valve timing device when the oil temperature is low.

Japanese Patent No. 4678545

  By the way, when the engine is operated under a high load condition, the oil temperature (lubricating oil temperature) may rise to around 130 ° C., so parts that are lubricated with lubricating oil or parts that are mounted near the oil passage The temperature may also rise to around 130 ° C. Further, since many oil passages are provided in the engine head, the electric variable valve timing device mounted on the engine head and its motor drive circuit may be in a high temperature state. The motor drive circuit is equipped with a switching element (such as a MOSFET) for controlling energization of the motor as a component that easily generates heat. When a large current flows through the switching element when the motor drive circuit is at a high temperature, the temperature of the switching element is increased. May exceed the allowable upper limit temperature (for example, 150 ° C.), and the switching element may be overheated.

  The technique of the above-mentioned patent document 1 suppresses the deterioration of the responsiveness of the variable valve timing device by increasing the current supplied to the motor during a period when the oil temperature is low to be larger than the normal value. Can't solve the problem.

  Accordingly, an object of the present invention is to provide a control device for an electric variable valve timing device that can prevent a switching element for energization control of a motor from being overheated.

In order to solve the above-mentioned problems, an invention according to claim 1 is an oil temperature estimation method for estimating a temperature of lubricating oil of an internal combustion engine in a control device for an electric variable valve timing device that changes a valve timing of the internal combustion engine by a motor. Means, a substrate temperature estimating means for estimating the temperature of the board on which the switching element for energization control of the motor is mounted based on the temperature of the lubricating oil estimated by the oil temperature estimating means, and the substrate temperature estimating means Current limit control means for limiting the current flowing through the switching element so that the temperature of the switching element does not exceed a predetermined allowable upper limit temperature based on the temperature of the board, and the board temperature estimation means is estimated by the oil temperature estimation means The base substrate temperature is calculated based on the temperature of the lubricating oil and the cooling water temperature of the internal combustion engine, and the base substrate temperature is smoothed to obtain the substrate temperature. It is obtained by the.

Since the temperature of the substrate of the motor drive circuit changes due to the influence of the temperature of the lubricating oil, if the temperature of the substrate is estimated based on the estimated temperature of the lubricating oil, the temperature of the substrate can be estimated with high accuracy. In addition, since there is a certain degree of correlation between the temperature of the board and the temperature of the switching element mounted on the board, switching is performed so that the temperature of the switching element does not exceed the allowable upper limit temperature based on the estimated board temperature. Limiting the current flowing through the element can prevent the switching element from being overheated. In addition, since it is not necessary to provide a temperature sensor for detecting the temperature of the lubricating oil, the temperature of the substrate, the temperature of the switching element, etc., the demand for cost reduction can be satisfied.
Further, when estimating the temperature of the substrate, the base substrate temperature is calculated based on the temperature of the lubricating oil estimated by the oil temperature estimating means and the cooling water temperature of the internal combustion engine, and the base substrate temperature is smoothed and processed. I want to find the temperature. In this way, the temperature of the substrate can be accurately estimated in consideration of both the temperature of the lubricating oil and the cooling water temperature.

  In this case, as in claim 2, when the substrate temperature estimated by the substrate temperature estimating means becomes higher than a predetermined determination value, the current flowing through the switching element is preferably limited by a predetermined upper limit guard value. . In general, the temperature of the substrate changes more slowly than the temperature of the switching element. Therefore, if current limiting control is performed to limit the current flowing through the switching element by comparing the substrate temperature with the determination value, the current It is possible to prevent hunting in which the restriction control is frequently switched between execution and stop.

  Alternatively, a switching element temperature estimation means for estimating the temperature of the switching element based on the substrate temperature estimated by the substrate temperature estimation means as in claim 3 is provided, and the switching element temperature estimation means estimated by the switching element temperature estimation means You may make it restrict | limit the electric current which flows into a switching element when temperature becomes higher than a predetermined | prescribed determination value with a predetermined | prescribed upper limit guard value. In this way, it is possible to accurately perform current limit control for limiting the current flowing through the switching element so that the temperature of the switching element does not exceed the allowable upper limit temperature based on the estimated temperature of the switching element.

  In this case, as in claim 4, the temperature rise due to self-heating of the switching element is calculated based on the current flowing through the switching element, and the temperature rise of the switching element is added to the temperature of the board estimated by the board temperature estimating means. Thus, the temperature of the switching element is preferably obtained. In this way, the temperature of the switching element can be accurately estimated in consideration of the temperature increase due to the self-heating of the switching element.

When estimating the temperature of the lubricating oil, as described in claim 5 , the temperature rise of the lubricating oil relative to the cooling water temperature of the internal combustion engine is calculated based on the operating state of the internal combustion engine, and the lubricating oil temperature is calculated as the cooling water temperature. A value obtained by adding the temperature rise may be smoothed to obtain the temperature of the lubricating oil. In this way, even in a region where the temperature of the lubricating oil is higher than the cooling water temperature, the temperature of the lubricating oil can be accurately estimated in consideration of the temperature rise of the lubricating oil with respect to the cooling water temperature.

Further, as in claim 6 , the combustion temperature of the internal combustion engine is calculated based on the operating state of the internal combustion engine, the temperature rise of the lubricating oil with respect to the cooling water temperature is calculated based on the combustion temperature, and lubrication is performed to the cooling water temperature. A value obtained by adding the oil temperature rise may be smoothed to obtain the temperature of the lubricating oil. In this way, the temperature of the lubricating oil can be estimated with higher accuracy in consideration of the combustion temperature that changes according to the operating state of the internal combustion engine, and the estimation accuracy of the substrate temperature based on the oil temperature is improved. be able to.

FIG. 1 is a diagram showing a schematic configuration of the entire valve timing control system in Embodiment 1 of the present invention. FIG. 2 is a schematic configuration diagram of the variable valve timing device. FIG. 3 is a time chart for explaining an execution example of the current limiting control based on the substrate temperature in the first embodiment. FIG. 4 is a flowchart showing the flow of processing of the substrate temperature estimation routine of the first embodiment. FIG. 5 is a flowchart showing the flow of processing of the current limit control routine of the first embodiment. FIG. 6 is a time chart for explaining an execution example of the current limiting control based on the substrate temperature in the second embodiment. FIG. 7 is a flowchart showing the flow of the substrate temperature estimation routine of the second embodiment. FIG. 8 is a time chart for explaining an execution example of the current limiting control based on the MOS temperature of the third embodiment. FIG. 9 is a flowchart showing the flow of processing of the MOS temperature estimation routine of the third embodiment. FIG. 10 is a flowchart showing the flow of processing of the current limit control routine of the third embodiment. FIG. 11 is a time chart illustrating an execution example of current limit control based on the MOS temperature of the fourth embodiment. FIG. 12 is a flowchart showing the flow of processing of the MOS temperature estimation routine of the fourth embodiment.

  Hereinafter, several embodiments in which the mode for carrying out the present invention is applied to a variable valve timing apparatus for an intake valve will be described.

A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire system will be described with reference to FIG.
The engine 11 that is an internal combustion engine transmits power from the crankshaft 12 to the intake side camshaft 16 and the exhaust side camshaft 17 via the sprockets 14 and 15 by the timing chain 13 (or timing belt). It has become. However, the intake side camshaft 16 is provided with an electric variable valve timing device 18. The variable valve timing device 18 changes the rotation phase (cam shaft phase) of the intake side cam shaft 16 with respect to the crankshaft 12 to change the valve of an intake valve (not shown) driven to open and close by the intake side cam shaft 16. The timing (opening / closing timing) is changed.

  A cam angle sensor 19 that outputs a cam angle signal for each predetermined cam angle in synchronization with the rotation of the intake side cam shaft 16 is attached to the outer peripheral side of the intake side cam shaft 16. On the other hand, a crank angle sensor 20 that outputs a crank angle signal at every predetermined crank angle in synchronization with the rotation of the crankshaft 12 is attached to the outer peripheral side of the crankshaft 12.

  Next, a schematic configuration of the electric variable valve timing device 18 will be described with reference to FIG. The configuration of the electric variable valve timing device 18 is not limited to the configuration shown in FIG. 2 and may be changed as appropriate.

  The phase variable mechanism 21 of the variable valve timing device 18 includes an outer gear 22 with inner teeth arranged concentrically with the intake side camshaft 16, and an outer gear with outer teeth arranged concentrically on the inner peripheral side of the outer gear 22. An inner gear 23 and a planetary gear 24 disposed between the outer gear 22 and the inner gear 23 and meshing with each other are constituted. The outer gear 22 is provided so as to rotate integrally with the sprocket 14 that rotates in synchronization with the crankshaft 12, and the inner gear 23 is provided so as to rotate integrally with the intake side camshaft 16. Further, the planetary gear 24 functions to transmit the rotational force of the outer gear 22 to the inner gear 23 by turning around the inner gear 23 in a state of meshing with the outer gear 22 and the inner gear 23, and also to play the outer gear 22. The rotational phase (cam shaft phase) of the inner gear 23 with respect to the outer gear 22 is adjusted by changing the turning speed (revolution speed) of the planetary gear 24 with respect to the rotational speed of 22.

  On the other hand, the engine 11 is provided with a motor 26 for changing the turning speed of the planetary gear 24. The rotation shaft 27 of the motor 26 is arranged coaxially with the intake side cam shaft 16, the outer gear 22 and the inner gear 23, and the rotation shaft 27 of the motor 26 and the support shaft 25 of the planetary gear 24 are connected to extend in the radial direction. It is connected via a member 28. Thus, as the motor 26 rotates, the planetary gear 24 can turn (revolve) on the circular orbit on the outer periphery of the inner gear 23 while rotating (spinning) around the support shaft 25. In addition, a motor rotation angle sensor 29 (see FIG. 1) that outputs a motor rotation angle signal at every predetermined rotation angle in synchronization with the rotation of the motor 26 is attached to the motor 26. Based on the output signal of the motor rotation angle sensor 29, the rotation angle and rotation speed of the motor 26 are detected.

  In the variable valve timing device 18, an outer gear 22, an inner gear 23, and a planetary gear 24 are configured so that the intake side camshaft 16 is driven at a rotational speed that is half the rotational speed of the crankshaft 12 in a steady state. The rotational speed of the motor 26 is adjusted with respect to the rotational speed ½ of the rotational speed of the motor 26 (in the steady state, ½ of the rotational speed of the crankshaft 12 = the rotational speed of the intake camshaft 16). The valve timing of the valve (camshaft phase on the intake side) is changed.

  When the valve timing is not changed, the rotational speed of the motor 26 is made to coincide with the rotational speed of the outer gear 22 (a rotational speed that is 1/2 of the rotational speed of the crankshaft 12), and the turning speed of the planetary gear 24 is set to the rotational speed of the outer gear 22. By matching the speed, the difference in rotational phase between the outer gear 22 and the inner gear 23 is maintained, and the valve timing (cam shaft phase) is maintained. In addition, when the motor 26 is not driven, the rotation shaft of the motor 26 is configured to rotate in synchronization with the outer gear 22 so that the rotation speed of the motor 26 is the rotation speed of the outer gear 22 (1/0 of the rotation speed of the crankshaft 12). 2 rotation speed).

  When changing the valve timing, the rotational speed of the motor 26 is changed with respect to the rotational speed of the outer gear 22, and the turning speed of the planetary gear 24 is changed with respect to the rotational speed of the outer gear 22. The valve timing (cam shaft phase) is changed by changing the difference in rotational phase between the inner gear 23 and the inner gear 23.

  For example, when the valve timing is advanced, the rotational speed of the motor 26 is made faster than the rotational speed of the outer gear 22, and the turning speed of the planetary gear 24 is made faster than the rotational speed of the outer gear 22. The valve timing (cam shaft phase) is advanced by advancing the rotational phase of the inner gear 23 with respect to.

  On the other hand, when retarding the valve timing, the rotational speed of the motor 26 is made slower than the rotational speed of the outer gear 22, and the turning speed of the planetary gear 24 is made slower than the rotational speed of the outer gear 22. The valve timing (cam shaft phase) is retarded by retarding the rotational phase of the inner gear 23 relative to the inner gear 23.

  Outputs of the various sensors described above are input to an electronic control unit (hereinafter referred to as “ECU”) 30. The ECU 30 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount and the ignition timing are determined according to the engine operating state. The throttle opening (intake air amount) and the like are controlled.

  Further, the ECU 30 calculates the actual rotation phase (actual cam shaft phase) of the intake cam shaft 16 with respect to the crankshaft 12 based on the output signals of the cam angle sensor 19 and the crank angle sensor 20 during engine operation, and the engine. The target camshaft phase is calculated according to the operating conditions, and the target motor speed is calculated based on the deviation between the target camshaft phase (target valve timing) and the actual camshaft phase (actual valve timing) and the engine speed. The calculated target motor rotation speed signal is output to a motor drive circuit (hereinafter referred to as “EDU”) 31. The EDU 31 feedback-controls the energization duty ratio (energization control amount) of the motor 26 so as to reduce the deviation between the target motor rotation speed and the actual motor rotation speed, thereby feedbacking the actual cam shaft phase to the target cam shaft phase. Control. Note that the function of the EDU 31 may be incorporated in the ECU 30.

  The EDU 31 for controlling the energization of the motor 26 of the variable valve timing device 18 is assembled to the variable valve timing device 18 mounted on the engine 11 or installed in the vicinity of the variable valve timing device 18. A substrate 33 on which a MOSFET 32 (Metal Oxide Semiconductor Field Effect Transistor) is mounted is provided as a switching element for energization control.

  In the first embodiment, the ECU 30 (or the ECU 30 and the EDU 31) executes the routines shown in FIGS. 4 and 5 to be described later, so that the oil temperature of the engine 11 (the temperature of the lubricating oil) is based on the engine operating state and the like. ) And the substrate temperature (the temperature of the substrate 33) is estimated based on the estimated oil temperature, and the MOS temperature (the temperature of the MOSFET 32) is set to a predetermined allowable upper limit temperature (for example, 150) based on the estimated substrate temperature. Current limit control is performed to limit the MOS current (current flowing through the MOSFET 32) so as not to exceed (° C.).

  Since the substrate temperature changes due to the influence of the oil temperature, the substrate temperature can be accurately estimated by estimating the substrate temperature based on the estimated oil temperature. In addition, since there is a certain degree of correlation between the substrate temperature and the MOS temperature, if the MOS current is limited so that the MOS temperature does not exceed the allowable upper limit temperature based on the estimated substrate temperature, the MOSFET 32 becomes overheated. Can be prevented.

  Specifically, as shown in the time chart of FIG. 3, during a period in which the coolant temperature of the engine 11 is equal to or less than a predetermined value (a period in which the oil temperature changes following the coolant temperature), the estimated value of the oil temperature is used as the coolant temperature. To the same value (or a value obtained by smoothing the cooling water temperature).

  Thereafter, during a period when the cooling water temperature is higher than the predetermined value (period during which the oil temperature is higher than the cooling water temperature), the oil temperature rise relative to the cooling water temperature (the lubricating oil temperature) Temperature rise) is calculated from a map or the like, the oil temperature rise is added to the cooling water temperature to obtain the base oil temperature, the base oil temperature is smoothed to obtain the oil temperature, and the oil temperature is estimated. Thereby, even in a region where the oil temperature is higher than the cooling water temperature, the oil temperature can be accurately estimated in consideration of the oil temperature increase with respect to the cooling water temperature.

  Furthermore, the substrate temperature is estimated by calculating the base substrate temperature based on the estimated oil temperature and the cooling water temperature (substitute information of the temperature in the engine room), and calculating the substrate temperature by smoothing the base substrate temperature. To do. Thereby, the substrate temperature can be accurately estimated in consideration of both the oil temperature and the cooling water temperature.

  Then, at the time t1 when the estimated substrate temperature becomes higher than a predetermined upper determination value (for example, a temperature slightly lower than the substrate temperature at which the MOS temperature becomes the allowable upper limit temperature), the MOS current is limited by the predetermined upper limit guard value. Thus, current limit control is performed to limit the MOS current so that the MOS temperature does not exceed the allowable upper limit temperature.

  Thereafter, at the time t2 when the substrate temperature becomes lower than a predetermined lower determination value (for example, a temperature lower than the upper determination value by a predetermined hysteresis), the limitation on the MOS current is released and the current limitation control is stopped.

  The current limiting control based on the substrate temperature of the first embodiment described above is executed by the ECU 30 (or the ECU 30 and the EDU 31) according to the routines shown in FIGS. Hereinafter, the processing content of each of these routines will be described.

[Substrate temperature estimation routine]
The substrate temperature estimation routine shown in FIG. 4 is repeatedly executed at a predetermined period during the power-on period of the ECU 30. When this routine is started, first, at step 101, it is determined whether or not the coolant temperature of the engine 11 detected by a coolant temperature sensor (not shown) is higher than a predetermined value. Here, the predetermined value is set to a temperature at which the oil temperature overtakes the cooling water temperature, for example.

If it is determined in step 101 that the cooling water temperature is equal to or lower than the predetermined value, it is determined that the oil temperature is a period that changes following the cooling water temperature, and the process proceeds to step 102 where the oil temperature (i) is determined. Is set to the same value as the cooling water temperature (or a value obtained by smoothing the cooling water temperature).
Oil temperature (i) = Cooling water temperature

  Thereafter, when it is determined in step 101 that the cooling water temperature is higher than the predetermined value, it is determined that the oil temperature is higher than the cooling water temperature, the process proceeds to step 103, and the oil temperature relative to the cooling water temperature is determined. With reference to the map of the increase, the oil temperature increase corresponding to the engine operating state (for example, engine speed and load) is calculated. The oil temperature rise map is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 30. Furthermore, the oil temperature increase may be corrected according to at least one of the outside air temperature, intake air temperature, ignition timing, air-fuel ratio, valve timing, and the like.

Thereafter, the process proceeds to step 104, and the base oil temperature is obtained by adding the oil temperature increase to the cooling water temperature.
Base oil temperature = Cooling water temperature + Oil temperature rise

Thereafter, the process proceeds to step 105, where the base oil temperature is smoothed by the following equation using the previous oil temperature (i-1) and the annealing rate a to obtain the current oil temperature (i). Estimate the temperature (i).
Oil temperature (i) = oil temperature (i-1) × a + base oil temperature × (1-a)
The processing of these steps 103 to 105 serves as oil temperature estimating means in the claims.

Thereafter, the process proceeds to step 106, where the current oil temperature (i), the previous substrate temperature (i-1), the cooling water temperature (substitute information on the temperature in the engine room), and the reflection rate b are used to calculate Determine the substrate temperature.
Base substrate temperature = oil temperature (i) − {substrate temperature (i−1) −cooling water temperature} × b

Thereafter, the process proceeds to step 107, and the base substrate temperature is smoothed by the following equation using the previous substrate temperature (i-1) and the annealing rate c to obtain the current substrate temperature (i). Estimate temperature (i).
Substrate temperature (i) = Substrate temperature (i−1) × c + Base substrate temperature × (1-c)
The processing in these steps 106 and 107 serves as substrate temperature estimation means in the claims.

[Current limit control routine]
The current limit control routine shown in FIG. 5 is repeatedly executed at a predetermined period during the power-on period of the ECU 30, and serves as current limit control means in the claims. When this routine is started, first, in step 201, it is determined whether or not the estimated substrate temperature is higher than a predetermined upper determination value. Here, the upper determination value is set to a temperature slightly lower than the substrate temperature at which the MOS temperature becomes the allowable upper limit temperature, for example.

  If it is determined in step 201 that the substrate temperature is equal to or lower than the upper determination value, this routine is terminated without executing the processing from step 202 onward.

  Thereafter, when it is determined in step 201 that the substrate temperature is higher than the upper determination value, the process proceeds to step 202, where the MOS current does not exceed the allowable upper limit temperature by limiting the MOS current with a predetermined upper limit guard value. Thus, current limit control for limiting the MOS current is executed. Further, the variable valve timing device 18 (motor 26) is controlled so that the cam shaft phase is forcibly changed to the limit position (for example, the most retarded position) of the movable range of the variable valve timing device 18, and the cam shaft at that time is controlled. The MOS current may be limited by prohibiting reference position learning in which the phase is learned as a reference position (for example, the most retarded angle position).

  Thereafter, the process proceeds to step 203, where it is determined whether or not the substrate temperature is lower than a predetermined lower determination value. Here, the lower determination value is set to a temperature lower than the upper determination value by a predetermined hysteresis, for example.

If it is determined in step 203 that the substrate temperature is equal to or higher than the lower determination value, the process returns to step 202 and the current limit control is continued.
Thereafter, when it is determined in step 203 that the substrate temperature is lower than the lower determination value, the process proceeds to step 204, where the limitation of the MOS current is released and the current limit control is stopped.

  In the first embodiment described above, the oil temperature of the engine 11 is estimated based on the engine operating state and the like, the substrate temperature is estimated based on the estimated oil temperature, and the estimated substrate temperature is determined from the upper determination value. Since the current limit control is performed to limit the MOS current so that the MOS temperature does not exceed the allowable upper limit temperature by limiting the MOS current with the upper limit guard value, the MOSFET 32 is in an overheated state. Can be prevented. In addition, since there is no need to provide a temperature sensor for detecting the oil temperature, the substrate temperature, the MOS temperature, etc., it is possible to satisfy the demand for cost reduction.

  In general, since the substrate temperature changes more slowly than the MOS temperature, if the current limit control is executed by comparing the substrate temperature with the determination value, the execution and stop of the current limit control are determined. Even if the difference between the upper judgment value and the lower judgment value (hysteresis) is not increased too much, hunting in which the current limit control is frequently switched between execution and stop can be prevented. (Axis phase) fluctuations and engine output fluctuations can be prevented.

  Next, Embodiment 2 of the present invention will be described with reference to FIGS. However, description of substantially the same parts as those in the first embodiment will be omitted or simplified, and different parts from the first embodiment will be mainly described.

  In the second embodiment, the ECU 30 (or the ECU 30 and the EDU 31) executes a substrate temperature estimation routine of FIG. 7 to be described later, so that the cooling water temperature is higher than a predetermined value as shown in the time chart of FIG. When estimating the oil temperature, the combustion temperature of the engine 11 is calculated by a map or the like based on the engine operating state (for example, the engine speed and load), and the oil temperature increase with respect to the cooling water temperature is calculated based on the combustion temperature. . Then, the base oil temperature is obtained by adding the oil temperature increase to the cooling water temperature, and the oil temperature is estimated by smoothing the base oil temperature to obtain the oil temperature.

  The routine of FIG. 7 executed in the second embodiment is obtained by changing the process of step 103 of the routine of FIG. 4 described in the first embodiment to the processes of steps 103a and 103b. The processing is the same as in FIG.

  In the substrate temperature estimation routine of FIG. 7, when it is determined in step 101 that the cooling water temperature is higher than the predetermined value, the process proceeds to step 103a, and the engine operating state (for example, engine rotation) is referred to by referring to the combustion temperature map. Calculate the combustion temperature according to the speed and load. The combustion temperature map is created in advance based on test data, design data, and the like, and is stored in the ROM of the ECU 30. Furthermore, the combustion temperature may be corrected according to at least one of the outside air temperature, intake air temperature, ignition timing, air-fuel ratio, valve timing, and the like.

Thereafter, the process proceeds to step 103b, and the oil temperature increase with respect to the cooling water temperature is obtained by the following equation using the combustion temperature, the previous oil temperature (i-1) and the reflection rate f.
Oil temperature rise = {combustion temperature-oil temperature (i-1)} × f

Thereafter, in step 104, the oil temperature increase is added to the cooling water temperature to obtain the base oil temperature, and in step 105, the base oil temperature is calculated using the previous oil temperature (i-1) and the rate of a. The oil temperature (i) is estimated by calculating the oil temperature (i).
The processing of these steps 103a to 105 serves as oil temperature estimation means in the claims.

  Thereafter, in step 106, the base substrate temperature is obtained using the current oil temperature (i), the previous substrate temperature (i-1), the cooling water temperature, and the reflection rate b, and then in step 107, the previous substrate temperature. (i-1) The substrate temperature (i) is estimated by smoothing the base substrate temperature using the annealing rate c and obtaining the current substrate temperature (i).

  In the second embodiment described above, when estimating the oil temperature, the combustion temperature of the engine 11 is calculated based on the engine operating state, and the oil temperature increase with respect to the cooling water temperature is calculated based on the combustion temperature. The oil temperature is estimated by adding the oil temperature rise to the cooling water temperature, and the base oil temperature is smoothed to obtain the oil temperature. The oil temperature can be estimated with higher accuracy in consideration of the combustion temperature to be performed, and the estimation accuracy of the substrate temperature based on the oil temperature can be improved.

  Next, Embodiment 3 of the present invention will be described with reference to FIGS. However, description of substantially the same parts as those in the first embodiment will be omitted or simplified, and different parts from the first embodiment will be mainly described.

  In the third embodiment, the substrate temperature is estimated by the same method as in the first embodiment by executing a MOS temperature estimation routine of FIG. 9 and a current limit control routine of FIG. 10 described later by the ECU 30 (or ECU 30 and EDU 31). Then, the MOS temperature is estimated based on the estimated substrate temperature, and the current limiting control is performed to limit the MOS current so that the MOS temperature does not exceed the allowable upper limit temperature based on the estimated MOS temperature. Yes.

  Specifically, as shown in the time chart of FIG. 8, during a period when the cooling water temperature is higher than a predetermined value, an oil temperature increase with respect to the cooling water temperature is calculated based on the engine operating state (for example, engine speed and load). The base oil temperature is obtained by adding the oil temperature rise to the cooling water temperature, and the oil temperature is estimated by smoothing the base oil temperature to obtain the oil temperature. A base substrate temperature is calculated based on the estimated oil temperature and cooling water temperature, and the substrate temperature is estimated by performing a smoothing process on the base substrate temperature to obtain the substrate temperature.

  Further, a MOS temperature rise (temperature rise due to self-heating of the MOSFET 32) is calculated based on the MOS current, and the MOS temperature is estimated by adding the MOS temperature rise to the substrate temperature to obtain the MOS temperature. As a result, the MOS temperature can be accurately estimated in consideration of the temperature rise due to the self-heating of the MOSFET 32.

  Then, at the time t1 when the estimated MOS temperature becomes higher than a predetermined upper determination value (for example, a temperature slightly lower than the allowable upper limit temperature of the MOS temperature), the MOS current is limited by the predetermined upper limit guard value. Current limit control is performed to limit the MOS current so that does not exceed the allowable upper limit temperature.

  Thereafter, at the time t2 when the MOS temperature becomes lower than a predetermined lower determination value (for example, a temperature lower than the upper determination value by a predetermined hysteresis), the limitation on the MOS current is released and the current limitation control is stopped.

  The current limiting control based on the MOS temperature of the third embodiment described above is executed by the ECU 30 (or the ECU 30 and the EDU 31) according to the routines shown in FIGS. Hereinafter, the processing content of each of these routines will be described. The processing of steps 301 to 307 of the routine of FIG. 9 executed in the third embodiment is substantially the same as the processing of steps 101 to 107 of the routine of FIG. 4 described in the first embodiment. To simplify.

  In the MOS temperature estimation routine shown in FIG. 9, first, in step 301, it is determined whether or not the cooling water temperature is higher than a predetermined value. If it is determined that the cooling water temperature is equal to or lower than the predetermined value, step 302 is executed. Then, the estimated value of the oil temperature (i) is set to the same value as the cooling water temperature (or a value obtained by smoothing the cooling water temperature).

  Thereafter, if it is determined in step 301 that the cooling water temperature is higher than the predetermined value, the process proceeds to step 303, and the engine operating state (for example, the engine speed) is referred to with reference to the map of the oil temperature increase with respect to the cooling water temperature. And the oil temperature rise according to the load). Furthermore, the oil temperature increase may be corrected according to at least one of the outside air temperature, intake air temperature, ignition timing, air-fuel ratio, valve timing, and the like.

  Thereafter, in step 304, the oil temperature increase is added to the cooling water temperature to obtain the base oil temperature, and in step 305, the base oil temperature is calculated using the previous oil temperature (i-1) and the rate of a. The oil temperature (i) is estimated by calculating the oil temperature (i).

  Thereafter, in step 306, the base substrate temperature is obtained using the current oil temperature (i), the previous substrate temperature (i-1), the cooling water temperature, and the reflection rate b, and then in step 307, the previous substrate temperature. (i-1) The substrate temperature (i) is estimated by smoothing the base substrate temperature using the annealing rate c and obtaining the current substrate temperature (i).

Thereafter, the process proceeds to step 308, in which the MOS current is multiplied by a coefficient d (temperature increase rate of the MOSFET 32 with respect to the MOS current) to obtain a base MOS temperature increase.
Base MOS temperature rise = MOS current x d

  Thereafter, the process proceeds to step 309, where the base MOS temperature increase is smoothed by the following equation using the previous MOS temperature increase (i-1) and the annealing rate e, and the current MOS temperature increase ( i)

MOS temperature rise (i) = MOS temperature rise (i-1) xe
+ Base MOS temperature rise x (1-e)

Thereafter, the process proceeds to step 310, where the MOS temperature is estimated by adding the MOS temperature increase to the substrate temperature to obtain the MOS temperature.
MOS temperature = substrate temperature + MOS temperature increase The processing of these steps 308 to 309 serves as switching element temperature estimation means in the claims.

  In the current limit control routine shown in FIG. 10, first, in step 401, it is determined whether or not the estimated MOS temperature is higher than a predetermined upper determination value. Here, the upper determination value is set to a temperature slightly lower than the allowable upper limit temperature of the MOS temperature, for example.

  If it is determined in step 401 that the MOS temperature is equal to or lower than the upper determination value, this routine is terminated without executing the processing from step 402 onward.

  Thereafter, when it is determined in step 401 that the MOS temperature is higher than the upper determination value, the process proceeds to step 402, where the MOS current does not exceed the allowable upper limit temperature by limiting the MOS current with a predetermined upper limit guard value. Thus, current limit control for limiting the MOS current is executed. Further, the MOS current may be limited by prohibiting the reference position learning.

  Thereafter, the process proceeds to step 403, where it is determined whether or not the MOS temperature is lower than a predetermined lower determination value. Here, the lower determination value is set to a temperature lower than the upper determination value by a predetermined hysteresis, for example.

  If it is determined in step 403 that the MOS temperature is equal to or higher than the lower determination value, the process returns to step 402 and current limit control is continued.

  Thereafter, when it is determined in step 403 that the MOS temperature is lower than the lower determination value, the process proceeds to step 404, where the limitation of the MOS current is released and the current limit control is stopped.

  In the third embodiment described above, the MOS temperature is estimated based on the estimated substrate temperature, and when the estimated MOS temperature becomes higher than the upper determination value, the MOS current is limited by the upper limit guard value. Since the current limit control for limiting the MOS current is performed so that the MOS temperature does not exceed the allowable upper limit temperature, the current limit control for limiting the MOS current is performed with high accuracy so that the MOS temperature does not exceed the allowable upper limit temperature. be able to.

  Next, Embodiment 4 of the present invention will be described with reference to FIGS. However, description of substantially the same parts as in the third embodiment will be omitted or simplified, and different parts from the third embodiment will be mainly described.

  In the fourth embodiment, the ECU 30 (or the ECU 30 and the EDU 31) executes a MOS temperature estimation routine shown in FIG. 12, which will be described later, so that the cooling water temperature is higher than a predetermined value as shown in the time chart of FIG. When estimating the oil temperature, the combustion temperature of the engine 11 is calculated by a map or the like based on the engine operating state (for example, the engine speed and load), and the oil temperature increase with respect to the cooling water temperature is calculated based on the combustion temperature. . Then, the base oil temperature is obtained by adding the oil temperature increase to the cooling water temperature, and the oil temperature is estimated by smoothing the base oil temperature to obtain the oil temperature.

  The routine of FIG. 12 executed in the fourth embodiment is obtained by changing the process of step 303 of the routine of FIG. 9 described in the third embodiment to the processes of steps 303a and 303b. The processing is the same as in FIG.

  In the MOS temperature estimation routine of FIG. 12, when it is determined in step 301 that the cooling water temperature is higher than a predetermined value, the process proceeds to step 303a, and the engine operating state (for example, engine rotation) is referred to by referring to the combustion temperature map. Calculate the combustion temperature according to the speed and load. Furthermore, the combustion temperature may be corrected according to at least one of the outside air temperature, intake air temperature, ignition timing, air-fuel ratio, valve timing, and the like.

Thereafter, the process proceeds to step 303b, and the oil temperature increase with respect to the cooling water temperature is obtained by the following equation using the combustion temperature, the previous oil temperature (i-1) and the reflection rate f.
Oil temperature rise = {combustion temperature-oil temperature (i-1)} × f

  Thereafter, in step 304, the oil temperature increase is added to the cooling water temperature to obtain the base oil temperature, and in step 305, the base oil temperature is calculated using the previous oil temperature (i-1) and the rate of a. The oil temperature (i) is estimated by calculating the oil temperature (i).

  Thereafter, in step 306, the base substrate temperature is obtained using the current oil temperature (i), the previous substrate temperature (i-1), the cooling water temperature, and the reflection rate b, and then in step 307, the previous substrate temperature. (i-1) The substrate temperature (i) is estimated by smoothing the base substrate temperature using the annealing rate c and obtaining the current substrate temperature (i).

  Thereafter, in step 308, the MOS current is multiplied by a coefficient d (the rate of temperature rise of the MOSFET 32 with respect to the MOS current) to obtain the base MOS temperature rise, and in step 309, the previous MOS temperature rise (i-1). ) The base MOS temperature rise is smoothed using the annealing rate e to obtain the current MOS temperature rise (i). Thereafter, in step 310, the MOS temperature is estimated by adding the increase in the MOS temperature to the substrate temperature to obtain the MOS temperature.

  In the fourth embodiment described above, the oil temperature can be estimated with higher accuracy in consideration of the combustion temperature that changes in accordance with the engine operating state as in the second embodiment. In addition, the estimation accuracy of the substrate temperature and the estimation accuracy of the MOS temperature can be improved.

  In each of the first to fourth embodiments, the present invention is applied to a system using the MOSFET 32 as a switching element for energization control of the motor 26. However, the present invention is not limited to this, and the switching element for energization control of the motor 26 is used. The present invention may be applied to a system using an FET (electrolytic effect transistor) or a transistor other than the MOSFET.

  In the first to fourth embodiments, the present invention is applied to a variable valve timing device for an intake valve. However, the present invention may be applied to a variable valve timing device for an exhaust valve. Furthermore, the phase variable mechanism of the variable valve timing device is not limited to the configuration described in the above embodiment (see FIG. 2), and other types of phase variable mechanisms may be used. Any electric variable valve timing device that changes the valve timing by changing the rotational phase of the cam shaft may be used.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 18 ... Variable valve timing apparatus, 26 ... Motor, 30 ... ECU (oil temperature estimation means, board | substrate temperature estimation means, current limiting control means, switching element temperature estimation means), 31 ... EDU, 32 ... MOSFET (switching element), 33 ... Substrate

Claims (6)

In a control device for an electric variable valve timing device that changes a valve timing of an internal combustion engine by a motor,
Oil temperature estimating means for estimating the temperature of the lubricating oil of the internal combustion engine;
Board temperature estimating means for estimating the temperature of the board on which the switching element for energization control of the motor is mounted based on the temperature of the lubricating oil estimated by the oil temperature estimating means;
Current limit control means for limiting the current flowing through the switching element so that the temperature of the switching element does not exceed a predetermined allowable upper limit temperature based on the substrate temperature estimated by the substrate temperature estimation means ;
The substrate temperature estimating means calculates a base substrate temperature based on the temperature of the lubricating oil estimated by the oil temperature estimating means and the cooling water temperature of the internal combustion engine, and performs a smoothing process on the base substrate temperature. A control device for an electric variable valve timing device characterized by obtaining a temperature .   The current limit control means limits a current flowing through the switching element with a predetermined upper limit guard value when the substrate temperature estimated by the substrate temperature estimation means becomes higher than a predetermined determination value. The control device for the electric variable valve timing device according to claim 1. Switching element temperature estimating means for estimating the temperature of the switching element based on the substrate temperature estimated by the substrate temperature estimating means,
The current limit control means limits the current flowing through the switching element with a predetermined upper limit guard value when the temperature of the switching element estimated by the switching element temperature estimation means becomes higher than a predetermined determination value. The control device for the electric variable valve timing device according to claim 1.   The switching element temperature estimation means calculates a temperature increase due to self-heating of the switching element based on a current flowing through the switching element, and adds the temperature increase of the switching element to the substrate temperature estimated by the substrate temperature estimation means. The control device for an electric variable valve timing device according to claim 3, wherein the temperature of the switching element is obtained by adding. The oil temperature estimating means calculates a temperature rise of the lubricating oil with respect to a cooling water temperature of the internal combustion engine based on an operating state of the internal combustion engine, and adds a value obtained by adding the temperature rise of the lubricating oil to the cooling water temperature. smoothing process to the control device of an electric variable valve timing apparatus according to any one of claims 1 to 4, wherein the determination of the temperature of the lubricating oil. The oil temperature estimating means calculates a combustion temperature of the internal combustion engine based on an operating state of the internal combustion engine, calculates a temperature rise of the lubricating oil with respect to the cooling water temperature based on the combustion temperature, and The control of the electric variable valve timing device according to any one of claims 1 to 4 , wherein the temperature of the lubricating oil is obtained by smoothing a value obtained by adding a temperature rise of the lubricating oil to a water temperature. apparatus.

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