JP2010048190A - Control device for internal combustion engine - Google Patents

Abstract

In an internal combustion engine having a variable valve operating device, overheating of a motor peripheral portion is suppressed while suppressing a decrease in vehicle comfort.
An engine including a variable valve operating apparatus having a first variable mechanism capable of continuously varying an operating angle and a lift amount of an intake valve by driving control of a switching circuit of an actuator. On the other hand, the ECU 100 executes a switching frequency control process. In this process, the ECU 100 switches the switching circuit 310 related to the PWM control of the drive motor 320 when the engine speed NE is equal to or less than the reference value NE1 or when the operating angle A of the intake valve 201 is equal to or less than the reference value A1. The frequency Fpwm is set to F2, and when the engine speed NE is higher than the reference value NE1 and the operating angle A of the intake valve 201 is larger than the reference value A1, the switching frequency Fpwm is set to F1 (F1 <F2).
[Selection] Figure 5

Description

  The present invention relates to a technical field of a control device for an internal combustion engine including a variable valve operating device that can vary the valve opening characteristics of an intake valve or an exhaust valve by a driving force of a motor.

  As this type of variable valve operating device, a device is disclosed in which a control shaft is rotated by a motor, and the lift amount of an intake or exhaust valve is made variable according to the rotational position of the control shaft (see, for example, Patent Document 1). .

  Further, in an internal combustion engine equipped with this type of variable valve mechanism, when the first intake valve is set to have a greater influence on the combustion state than the second intake valve, and a predetermined deposit removal condition is satisfied A technique for opening the first intake valve before the second intake valve has also been proposed (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 2007-1000056 JP 2007-231741 A

  In this type of variable valve apparatus, PWM control is often used for energizing the motor. At this time, the electromagnetic sound emitted from the motor is an unpleasant sound for the driver and may cause a decrease in the comfort performance of the vehicle, so that it is necessary to take some measures for the suppression. At this time, it is conceivable to increase the switching frequency related to the PWM control.

  However, when the switching frequency is increased, the number of times the motor is turned on and off per unit time increases, so the amount of heat generated by the driving means for driving the motor increases. At this time, in view of the possibility that the operation of the variable valve operating apparatus may be hindered, it is necessary to provide some heat radiating means in order to suppress the heat generation of the drive means. The configuration of the apparatus may be enlarged, resulting in an increase in cost or deterioration in mountability.

  The various conventional techniques mentioned above do not mention anything about the device configuration and the control mode for suppressing both the motor electromagnetic sound and the heat generation of the drive device, which are in a mutually contradictory relationship. There is a technical problem that it is extremely difficult at least in practical terms to suppress overheating of the drive device while suppressing deterioration of the performance.

  The present invention has been made in view of the above-described problems. In an internal combustion engine including this type of variable valve operating apparatus, an internal combustion engine that can suppress overheating of a motor peripheral portion while suppressing a decrease in vehicle comfort. It is an object of the present invention to provide an engine control device.

  In order to solve the above-described problems, a control apparatus for an internal combustion engine according to the present invention includes a motor and drive means capable of driving the motor by PWM control, and an intake valve or an exhaust by a driving force applied from the motor. A control device for an internal combustion engine comprising a variable valve device capable of changing at least one of a working angle and a lift amount in a valve, wherein the specifying means for specifying the at least one and the specified at least one And a first control means for controlling the drive means so that the switching frequency related to the PWM control decreases and increases as the increase and decrease occur, respectively.

  The “variable valve operating device” according to the present invention means an intake valve or an exhaust valve (directly or indirectly) by a driving force applied from a motor (which may be direct current drive or alternating current drive). Hereinafter, it is appropriately expressed as “control target valve.” Note that the control target valve may be both an intake valve and an exhaust valve) and / or a lift amount. A device having a physical, mechanical, electrical, or magnetic configuration that can be changed in a binary, stepwise, or continuous manner, and particularly as a drive system for the motor. This motor can be driven by PWM (Pulse Width Modulation) control (preferably a method of controlling the motor energization amount by the period T and the duty ratio D), including various power supplies, various switching circuits, various electric drive circuits, etc. Drive means Refers to the device comprising.

  The motor electromagnetic noise as a kind of noise generated when the motor is driven by PWM control varies depending on the switching frequency related to the PWM control. More specifically, when the switching frequency is high, the motor electromagnetic noise can be reduced in a binary, stepwise or continuous manner as compared with a case where the switching frequency is low. In particular, if the switching frequency is in a high frequency range exceeding the human audible range, the motor electromagnetic noise can be significantly reduced.

  On the other hand, this switching frequency correlates with the amount of heat generated by driving means (for example, a switching circuit) for driving the motor. More specifically, when the switching frequency is high, the amount of heat generated by the drive means tends to be larger than when the switching frequency is low due to an increase in the number of on / off operations of the motor per unit time. . Thus, the motor electromagnetic noise and the heat generation of the driving means are mutually contradictory when the switching frequency is selected as a control parameter that affects them, and it is difficult to suppress them simultaneously.

  Here, the degree of influence of the motor electromagnetic sound on the comfort of the vehicle is not uniform, and the allowable amount of heat generated in the driving means by the switching frequency is not uniform. With regard to the former, if the mechanical operation noise of the internal combustion engine including the drive sound of the variable valve operating system is large, the influence of the motor electromagnetic sound on the comfort of the vehicle is reduced (in other words, the operation noise is large. For example, whether the motor electromagnetic noise is loud or small, there is no change in comfort.) Therefore, in a region where the mechanical operation noise is large, the necessity for suppressing motor electromagnetic noise is reduced.

  As for the latter, if the upper limit of the thermal load allowed for the drive means (any kind of thermal load index) is uniquely defined, the heat generated by the drive means is generated regardless of the switching frequency. The smaller the amount of heat generated (in other words, the amount of heat generated as a base), the greater the allowable amount of heat generated by the switching frequency. Therefore, in the region where the amount of heat generation serving as the base is small, the necessity of reducing the switching frequency naturally decreases.

  Here, in particular, when the control element value (that is, the operating angle or the lift amount) is large, the above-described operation noise becomes large and the motor holding current is increased when the control element value is low. Due to the influence of force, the amount of heat generated as a base increases as described above. That is, if the necessity to suppress the motor electromagnetic noise decreases, the allowable value of the amount of heat generated due to the switching frequency decreases, and conversely, if the necessity increases, the allowable value increases.

  Focusing on this point, in the control device for an internal combustion engine of the present invention, for example, specific means that can take the form of various processing units such as an ECU (Electronic Control Unit), various controllers or various computer systems such as a microcomputer device, etc. The control element value is specified by the first control means that can take the form of various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device, and the driving means according to the specified control element value. Is controlled. At this time, the control means is such that the magnitude of the control element value is increased or decreased according to the PWM control, for example, one-to-one, one-to-many, many-to-one or many-to-many, or binary, stepwise or continuous. The driving means is controlled so as to respond to the situation.

  According to the action of the first control means, when the necessity of suppressing the motor electromagnetic noise is low (that is, the allowable value of the heat generation amount is small), the switching frequency is lowered, so that the comfort of the vehicle is lowered. (For example, the above-described mechanical operation noise caused by elements other than motor electromagnetic noise is outside the scope of the present invention, and its magnitude does not hinder the effects of the present invention), and suppresses overheating of the driving means. Can do. Further, according to the action of the first control means, when the necessity of suppressing the motor electromagnetic noise is high (that is, the allowable value of the heat generation amount is large), the switching frequency increases (changes to the high frequency side). It is possible to suppress a decrease in the comfort of the vehicle while suppressing overheating of the driving means. That is, according to the control device for an internal combustion engine of the present invention, it is possible to suppress both a decrease in the comfort of the vehicle and an overheating of the driving means as the motor peripheral portion.

  In other words, the present invention relates to the necessity for motor electromagnetic noise suppression and driving according to the control element value (working angle and / or lift amount or both) of the valve to be controlled (intake valve and / or exhaust valve). The necessity for suppressing overheating of the means has changed, and furthermore, the magnitude of each need has been made with a point of being mutually contradictory, in other words, the control element value On the basis of this, it was made with a focus on the point that it is possible to accurately determine whether to give priority to suppression of motor electromagnetic noise or to suppress overheating of the drive means.

  Therefore, the present invention is completely different from the control mode in which the switching frequency is single, or the switching frequency is simply variable without being based on any guideline. Can provide high practical benefits.

  The “specific” according to the present invention refers to a physical quantity, control amount, or index value correlated with a specific target (in the present invention, at least one of an operating angle and a lift amount) or a specific target via a predetermined detection means. Directly or indirectly detected, stored in advance in appropriate storage means based on physical quantity, control amount or index value correlated with specific object detected directly or indirectly via the detection means Selecting a corresponding value from a map, etc., deriving from a physical quantity, control quantity or index value or a selected value correlated with this type of specific target, or in accordance with a preset algorithm or calculation formula, or this Thus, it is a broad concept that includes simply acquiring the value detected, selected or derived in the form of, for example, an electric signal, etc. Kutomo contrast (i.e., a is the "control element value") may be identified. At this time, the first control means or various controllers configured to be able to communicate with the first control means may control the drive means via feedback control or the like in order to converge the control element value to the target value. For example, the specifying means can specify the control element value relatively easily.

  In one aspect of the control apparatus for an internal combustion engine of the present invention, when the at least one specified is not less than a predetermined value, the at least one specified is less than the predetermined value. The driving means is controlled so that the switching frequency is lowered as compared with the above.

  According to this aspect, the specified control element value is greater than or equal to a predetermined value (“more than” is a concept that can be easily replaced with “greater” depending on the setting of the predetermined value. May belong to any region, and which region does not affect the essence of the present invention), the switching frequency is lowered. That is, in this aspect, the switching frequency is selectively switched among a plurality of candidate values. For this reason, according to this aspect, the practical benefit according to the present invention can be easily enjoyed while suppressing an increase in the control load.

  The “predetermined value” may be a single value or a plurality of values, and if there are at least two types of switching frequency candidate values regardless of whether they are preset or stored. Good. The predetermined value may be a value that is conceptually within a range that can be taken by the control element value. As a preferable form, it is experimentally, empirically, theoretically, or based on a simulation or the like. The engine noise of the internal combustion engine can be more dominant in practice than the motor electromagnetic noise in the region beyond that, or the heat generation amount of the drive means can be increased to a level that is practically not negligible in the region beyond it. It may be determined as follows.

  In this aspect, the first control means reduces the switching frequency when at least one of the specified values is equal to or greater than the predetermined value and the engine rotation speed of the internal combustion engine is in a predetermined high rotation range. You may let them.

  When the engine rotation speed belongs to, for example, a high rotation region distinguished by an appropriate value, the engine rotation sound as the engine noise described above increases. Therefore, in this case, it is possible to more reliably prevent a decrease in vehicle comfort associated with a reduction in motor electromagnetic noise.

  In another aspect of the control device for an internal combustion engine of the present invention, the engine noise suppression sound is generated by synchronizing the engine noise with the frequency and reversing the phase by continuously changing the switching frequency. Further comprising second control means for controlling the driving means.

  According to this aspect, for example, the switching frequency is periodically and continuously changed by the second control means that can take the form of various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device. The periodic sound (that is, engine noise suppression sound) is synchronized with the frequency of the engine noise (preferably, it is a periodic sound corresponding to the engine rotation speed). In addition, since the sound is generated as an anti-phase sound, the comfort of the vehicle can be further improved. The practical benefit relating to the action of the second control means is not in conflict with the practical benefit relating to the action of the first control means described above, and the first and second control means cooperate with each other. Each operation may be performed.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

<Embodiment of the Invention>
Various preferred embodiments of the present invention will be described below with reference to the drawings.
<1: First Embodiment>
<Configuration of Embodiment>
First, the configuration of the engine system 10 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of the engine system 10.

  1, the engine system 10 is mounted on a vehicle (not shown) and includes an ECU 100, an engine 200, an actuator 300, an angle sensor 400, and an accelerator opening sensor 500.

  The ECU 100 is an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM, and the like, and is configured to be able to control the entire operation of the engine system 10. It is an example of an “engine control device”. The ECU 100 is configured to execute a switching frequency control process, which will be described later, according to a control program stored in the ROM. In this embodiment, the ECU 100 is an integrated electronic control unit configured to function as an example of each of the “specifying unit” and the “first control unit” according to the present invention, and corresponds to each of these units. Each operation is performed by the ECU 100. However, the physical, mechanical, and electrical configurations of each of the units according to the present invention are not limited to this. For example, each of these units includes a plurality of ECUs, various processing units, various controllers, a microcomputer device, and the like. It may be configured as various computer systems.

  The engine 200 is an in-line four-cylinder gasoline engine that is an example of an “internal combustion engine” according to the present invention that is configured to function as a power source for a vehicle. The engine 200 burns the air-fuel mixture through an ignition operation by an ignition device in which a part of a spark plug is exposed in the combustion chamber inside each cylinder, and the piston reciprocates in response to the explosive force caused by the combustion. The movement is converted into the rotational movement of the crankshaft via the connecting rod.

  The engine 200 is a gasoline engine, but the “internal combustion engine” according to the present invention includes at least one cylinder, and in each of the cylinders, gasoline, light oil, alcohol, or a mixture in which these are appropriately mixed. Power generated when fuel that can take various forms, such as fuel, is combusted (preferably, a mixture of fuel and air is combusted) is transmitted to the vehicle via mechanical transmission paths such as pistons, connecting rods, and crankshafts. It is a concept that encompasses an engine that can be extracted as a driving force, and its detailed configuration can take various forms regardless of whether it is known or not known.

  The engine 200 has two intake valves 201 (not shown in FIG. 1) for each cylinder, and due to the action of the variable valve device 210, the operating angle and lift of each intake valve 201 for each cylinder. The amount can be continuously changed. Here, with reference to FIG. 2, the detailed structure of the variable valve apparatus 210 is demonstrated. FIG. 2 is a schematic side cross-sectional view conceptually showing the cross-sectional configuration of the periphery of the variable valve operating apparatus 210. In the figure, the same reference numerals are assigned to the same parts as those in FIG. 1, and the description thereof is omitted as appropriate.

  In FIG. 2, the variable valve operating apparatus 210 includes a first variable mechanism 600 provided corresponding to one intake valve 201 and a second variable mechanism (not shown) provided corresponding to the other intake valve 201. With. The first variable mechanism 600 and the second variable mechanism have substantially the same configuration, and only the configuration of the first variable mechanism 600 will be described here.

  The first variable mechanism 600 extends in the depth direction of the drawing and is connected to a crankshaft (not shown) via a timing belt, so that the engine 200 is driven to rotate in the direction indicated by the arrow A along with the rotation of the crankshaft. The rotational motion of the first intake cam 203 having an elliptical cross-sectional view that is fixed to the intake cam shaft 202 so as to be integrally rotatable with the intake cam shaft 202 is converted into a linear motion (see arrow B in the figure). It can be transmitted to the intake valve 201.

  The first variable mechanism 600 includes a control shaft 601, a rocker arm 603 that is supported at one end by a hydraulic lash adjuster 602 and swings in conjunction with the intake valve 201, and can rotate integrally with the control shaft 601 with respect to the control shaft 601. And a control arm 604 fixed to the head. The control arm 604 projects in the radial direction of the control shaft 601, and an arcuate link arm 605 is attached to the projecting portion.

  The base end portion of the link arm 605 is rotatably connected to the control arm 604 by a pin 606. The position of the pin 606 is eccentric from the center of the control shaft 601, and this pin 606 serves as a fulcrum for swinging the link arm 605. A connecting shaft 607 that connects the link arm 605 and the link arm of the second variable mechanism is provided at the distal end of the link arm 605 opposite to the base end. The connecting shaft 607 is provided with a first roller 608 and a second roller 609 that are rotatably supported by the connecting shaft 607. The first roller 608 is in contact with the first intake cam 203.

  The first variable mechanism 600 includes a swing cam arm 610 that is swingably supported on the control shaft 601. A slide surface 610a that contacts the second roller 609 provided at the tip of the link arm 605 is formed on the swing cam arm 610 on the side facing the first intake cam 203, and on the opposite side of the slide surface 610a. Is formed with a rocking cam surface 610b that comes into contact with a rocker roller 611 rotatably provided at an intermediate portion of the rocker arm 603. The illustrated cross-sectional shape of the slide surface 610a is such that the gap between the slide surface 610a and the intake cam 203 gradually narrows as the second roller 609 moves from the axial center side of the control shaft 601 toward the distal end side of the swing cam arm 610. It is formed with such a curve. The swing cam surface 610b has a non-acting surface 610ba formed so as to have a constant distance from the swing center of the swing cam arm 610, and a position away from the non-acting surface 610ba from the axis center of the control shaft 601. The working surface 610bb is formed so as to be far away.

  According to the first variable mechanism 600 described above, when the first intake cam 203 drives the first roller 608, the slide surface 610a is pushed by the second roller 609, so that the swing cam arm 610 is centered on the control shaft 601. Rotate 2 downward. When the contact position between the rocking cam surface 610b and the rocker roller 611 moves from the non-working surface 610ba to the working surface 610bb along with the rotation of the rocking cam arm 610, the rocker arm 603 is pushed down and the intake air 201 is opened. . That is, the rotational motion of the intake camshaft 202 is converted into the linear motion of the intake valve 201.

  Further, according to the first variable mechanism 600, the lift amount and the operating angle of the intake valve 201 can be changed by changing the rotation angle of the control shaft 601. FIG. 2 shows a state in which the lift amount L and the operating angle A of the intake valve 201 are maximized within a range that can be changed by the first variable mechanism 600 (hereinafter, referred to as “large lift state” as appropriate). Has been. Here, when the control shaft 601 is rotated counterclockwise in FIG. 2 from the state shown in FIG. 2, the second roller provided at the tip of the link arm 605 by the control arm 604 that rotates integrally with the control shaft 601. 609 moves to the distal end side of the swing cam arm 610 along the slide surface 610a. In this case, since the position of the second roller 609 is away from the center of the control shaft 601, the amplitude at which the swing cam arm 610 swings is reduced. This reduction in amplitude reduces the amount of movement of the rocker arm 603 when the rocker arm 603 is pushed down, and as a result, the lift amount of the intake valve 201 decreases.

  In such a state where the lift amount is relatively small (hereinafter, referred to as “small lift state” as appropriate), the roller rocker 611 and the swing cam surface 610b before the swing cam arm 610 starts swinging. The contact position is changed clockwise from the large lift state in which the lift amount is maximized around the control shaft 601, that is, the position moved to the non-operation surface 610 ba side. Therefore, in the small lift state, the timing at which the contact position between the rocker roller 611 and the rocking cam surface 610b moves from the non-working surface 610ba to the working surface 610bb after the rocking cam arm 610 starts swinging is later than in the large lift state. . Since the intake valve 201 is opened while the rocker roller 611 is in contact with the working surface 610bb, the timing of moving from the non-working surface 610ba to the working surface 610bb is delayed in this manner, so that in the small lift state In this case, the opening timing of the intake valve 201 is later than that of the large lift state, and the closing timing of the intake valve 201 is advanced. That is, the operating angle of the intake valve 201 is reduced.

  Since the intake camshaft 202 rotates clockwise as shown in the figure, in the small lift state, the connecting shaft 607 moves upstream in the rotational direction of the first intake cam 203 than in the large lift state. . Therefore, the timing at which the swing cam arm 610 starts swinging by the first intake cam 203 is earlier in the small lift state than in the large lift state. As a result, the opening timing of the intake valve 201 is earlier in the small lift state than in the large lift state. As a result, the delay in the closing timing of the intake valve 201 due to the delay in the timing at which the contact position between the rocker roller 611 and the swing cam surface 610b moves from the non-operating surface 610ba to the operating surface 610bb is almost offset. . In this way, in the first variable mechanism 600, the lift amount and the operating angle of the intake valve 201 can be changed without substantially changing the valve opening timing (valve timing) of the intake valve 201.

  On the other hand, a second intake cam (not shown) having an elliptical cross-sectional view as in the first intake cam 203 is fixed to the intake camshaft 202, and the second variable mechanism swings through a lock mechanism (not shown). It is configured to be appropriately connected to a moving cam arm (that is, a configuration equivalent to that of the swing cam arm 610). The lock mechanism has a large lift arm provided on the control shaft 601 along with the swing cam arm of the second variable mechanism and swingable independently of the swing cam arm, and a coupling device. ing.

  The large lift arm is rotatably fixed to the large lift arm and an input roller that contacts the second intake cam is driven by the second intake cam, whereby the first variable mechanism 600 described above is in the large lift state. In this case, the swing cam arm 610 swings with an amplitude equivalent to that of the swing cam arm 610.

  In addition, the coupling device includes a hydraulic chamber formed in the large lift arm, an oil control valve that can supply hydraulic oil to the hydraulic chamber via a predetermined hydraulic path, and a protruding and retracting state according to the hydraulic pressure of the hydraulic chamber And a lock pin that is variable. The lock pin is configured to fit into a lock hole formed on the large lift arm side of the swing cam arm of the second variable mechanism when a predetermined hydraulic pressure is applied to the hydraulic chamber. When the lock pin is fitted in the lock hole, the swing cam arm of the second variable mechanism is fixed to the large lift arm.

  That is, the swing cam arm of the second variable mechanism is driven by the second intake cam in a state where it is fixed to the large lift arm by the lock mechanism, and is previously described in a state where it is not fixed to the large lift arm by the lock mechanism. It is driven by the first intake cam 203 in the same manner as the swing cam arm of the first variable mechanism. In other words, in the variable valve operating apparatus 210, when the large lift arm and the swing cam arm of the second variable mechanism are connected, the change in the lift amount L and the working angle A due to the change in the rotation angle of the control shaft 601 is as follows. When acting only on one intake valve 203 corresponding to the first variable mechanism 600 and the connection between the large lift arm and the swing cam arm of the second variable mechanism is released, lift by changing the rotation angle of the control shaft 601 The change of the amount L and the operating angle A acts on both intake valves 203.

  The variable valve device 210 is provided with a VVT (Variable Valve Timing) independently of these variable mechanisms. The VVT is configured to change the phase relationship between the intake camshaft 202 and the crankshaft of the engine 200, and to change the opening timing and closing timing of each intake valve. However, the VVT may have a configuration in which, for example, a vane rotor that can rotate in synchronization with the intake camshaft 202 is rotated to the advance side or the retard side according to the hydraulic pressure of hydraulic fluid such as oil, for example. Alternatively, a shaft body or piston that is connected to the intake camshaft 202 through a helical gear or a helical spline as appropriate, and can be reciprocated in the camshaft direction, is driven by an actuator that uses hydraulic pressure as a drive source, The reciprocating motion may be converted into the rotational motion of the camshaft. The configuration is well known and has little correlation with the present invention, and therefore detailed description thereof will be omitted here.

  Returning to FIG. 1, the actuator 300 is a driving device configured to be able to rotationally drive the control shaft 601 described above in the variable valve operating device 210. Here, the actuator 300 will be described with reference to FIG. Here, FIG. 3 is a schematic circuit diagram of the actuator 300.

  In FIG. 3, the actuator 300 includes a switching circuit 310 including FETs 311, 312, 313, and 314 that function as switching elements, and a DC drive type drive motor 320.

  In the switching circuit 310, an FET 311 and an FET 313 are connected in series, and an FET 312 and an FET 314 are connected in series, and these are connected in parallel to an in-vehicle battery (shown as + B) as a driving force source. The switching circuit 310 is constructed as a so-called H-bridge circuit in which a drive motor 320 is connected between a connection point between the FET 311 and the FET 313 and a connection point between the FET 312 and the FET 314. Further, each FET constituting the switching circuit 310 is electrically connected to the ECU 100, and an on / off state as a driving state is controlled by the ECU 100.

  In such a configuration, one of the upstream side element group composed of the FET 311 and the FET 312 is selectively turned on and the other is turned off, and the energization direction to the drive motor 320 is switched. Further, the downstream side element group including the FET 313 and the FET 314 is switched on and off according to a duty ratio determined separately by a PWM pulse signal supplied from the ECU 100. That is, in the actuator 300, the energization amount to the drive motor 320 is controlled by so-called PWM control. At this time, the switching frequency Fpwm in the PWM control is controlled by a switching frequency control process executed by the ECU 100.

  Returning to FIG. 1, the angle sensor 400 is a Hall sensor configured to be able to detect the rotation angle of the control shaft 601 described above in the variable valve apparatus 210. The angle sensor 400 is electrically connected to the ECU 100, and the detected rotation angle θ of the control shaft 610 is referred to by the ECU 100 at a constant or indefinite timing.

<Operation of Embodiment>
<Control of working angle and lift amount>
As described above, in the engine system 10, the operating angle A and the lift amount L of the intake valve 201 can be continuously changed by the action of the first variable mechanism 600 in the variable valve apparatus 210. . At this time, control target values for the operating angle A and the lift amount L are determined based on the load state of the engine 200. More specifically, the ECU 100 is based on an accelerator opening detected by an accelerator opening sensor (not shown in FIG. 1) or an intake air amount detected by an air flow meter (not shown in FIG. 1). The load state of the engine 200 is discriminated, and as a qualitative tendency, the control target values of the operating angle A and the lift amount L are set so that the operating angle A and the lift amount L increase as the load increases from light load to high load. decide.

  Here, the control target values of the operating angle A and the lift amount L are practically equivalent to the target values of the rotation angle of the control shaft 610. Therefore, a control map in which the load state of the engine 200 and the rotation angle of the control shaft 610 are associated in advance is stored in the ROM of the ECU 100, and the target rotation of the control shaft 610 is selectively selected as appropriate from the control map. Corners are acquired.

  The ECU 100 thus determines the target rotation angle of the control shaft 610 corresponding to the current load state of the engine 200 based on the control map, and is detected by the current rotation angle of the control shaft 610 (ie, the angle sensor 400). ) To perform feedback control according to the deviation. At this time, as described above, the drive motor 320 of the actuator 300 is PWM-controlled. Basically, the larger the deviation, the higher the duty ratio (that is, the switching period 310 determined according to the switching frequency Fpwm). (The ratio of the ON time of the FET 313 or FET 314 constituting the downstream element group) is set large. It should be noted that a known feedback method such as PID control or PI control can be applied to the feedback control of the rotation angle of the control shaft 610, and details thereof will not be described here.

  On the other hand, when PWM control is performed on the drive motor 320 via the switching circuit 310 in this way, noise generated from the actuator 300 (mainly electromagnetic noise of the drive motor 320 (hereinafter referred to as “motor electromagnetic noise” as appropriate)) and heat generation ( It is necessary to consider mainly the heat generation amount of the FET constituting the switching circuit 310 (hereinafter referred to as “FET heat generation amount” as appropriate) On the other hand, the motor electromagnetic noise and the FET heat generation amount correspond to the switching frequency Fpwm of the switching circuit 310. There is a correlation.

  Here, with reference to FIG. 4, the relationship between the switching frequency Fpwm, motor electromagnetic noise, and FET heat generation will be described. FIG. 4 is a schematic characteristic diagram illustrating one characteristic of the motor electromagnetic sound and the FET heat generation amount with respect to the switching frequency Fpwm.

  In FIG. 4, the characteristics of the motor electromagnetic noise are shown in FIG. 4A, and the characteristics of the FET heat generation amount are shown in FIG. 4B.

  As is apparent from FIG. 4A, the motor electromagnetic noise decreases as the switching frequency Fpwm increases. Further, as apparent from FIG. 4B, the amount of heat generated from the FET increases as the switching frequency Fpwm increases (ie, regardless of the duty ratio) due to the fact that the on / off state of each FET does not switch instantaneously. The number of on / off increases). That is, both are in a contradictory relationship with the switching frequency Fpwm. For this reason, when the motor electromagnetic noise is reduced to reduce the noise emitted from the actuator 300 and improve the comfort of the vehicle, overheating of the actuator 300 due to an increase in the amount of heat generated by the FET becomes difficult to avoid. When it is attempted to suppress overheating of the actuator 300 by reducing the FET heat generation amount, it becomes difficult to avoid a decrease in vehicle comfort due to an increase in motor electromagnetic noise. Therefore, in the present embodiment, such a problem is preferably solved by the switching frequency control process executed by the ECU 100.

<Details of switching frequency control processing>
Here, with reference to FIG. 4, the details of the switching frequency control process will be described as the operation of the present embodiment. FIG. 5 is a flowchart of the switching frequency control process.

  In FIG. 4, the ECU 100 determines whether or not the engine speed NE of the engine 200 is higher than a predetermined reference value NE1 (step S11). The reference value NE1 will be described later. When the engine speed NE is higher than the reference value NE1 (step S11: YES), the ECU 100 further determines that the operating angle A of the intake valve controlled by the first variable mechanism 600 of the variable valve device 210 is It is determined whether or not it is larger than the reference value A1 (step S12). The reference value A1 will be described later. Note that the index value used for the determination process in step S12 may be the lift amount L instead of the operating angle A. In view of the fact that the operating angle A and the lift amount L are defined by the rotation angle of the control shaft 610, the index value may be the rotation angle.

  When the operating angle A is larger than the reference value A1 (step S12: YES), the ECU 100 sets the switching frequency Fpwm to F1 (step S13), and whether the operating angle A is equal to or less than the reference value A1 (step S12: NO). ), Or when the engine speed NE is equal to or lower than the reference value NE1 (step S11: NO), the switching frequency Fpwm is set to F2 (F2> F1) (step S14). When step S13 or step S14 is executed, the switching frequency control process ends. Note that the switching frequency control process is repeatedly executed at a predetermined cycle, and the processes after step S11 are repeatedly executed after an appropriate time has elapsed.

  Here, as shown in FIG. 4, the level of the switching frequency Fpwm corresponds to the magnitude of the motor electromagnetic sound and the magnitude of the FET heat generation. Therefore, according to the switching frequency control process, (1) when the engine speed NE is relatively low or the operating angle A is relatively small, the motor electromagnetic noise is relatively small and the FET heat generation amount is (2) When the engine rotational speed NE is relatively high and the operating angle A is relatively large, the motor electromagnetic noise is relatively loud and the FET heat generation is relatively large. Become small.

  Here, in particular, the operating sound of the engine 200 is louder as the engine rotational speed is higher, and is larger as the operating angle of the intake valve 201 is larger. Therefore, the degree of the influence of the motor electromagnetic noise on the noise of the entire vehicle becomes lower as the engine rotational speed NE is higher and the operating angle A is larger, and the allowable amount of the motor electromagnetic noise is increased. For this reason, when step S12 branches to the “YES” side, the comfort of the vehicle is not impaired even if the switching frequency Fpwm is set relatively low. On the other hand, since the valve reaction force of the intake valve 201 increases as the operating angle A increases, the value of the holding current to be supplied to the drive motor 320 to maintain the rotation angle of the control shaft 610 increases, and the switching frequency Fpwm Regardless of the amount of heat generated, the amount of heat generated according to the power consumption increases, so that the allowable amount of FET heat generated by the switching frequency Fpwm decreases. For this reason, when step S12 branches to the “YES” side, it is possible to determine that priority should be given to reducing the amount of heat generated from the FET, and setting the switching frequency Fpwm to F1 suppresses overheating of the switching circuit 310. Is planned.

  On the contrary, the smaller the operating angle A is, the smaller the valve reaction force of the intake valve 201 becomes. Therefore, the value of the holding current to be supplied to the drive motor 320 in order to maintain the rotation angle of the control shaft 610 becomes small, and the switching frequency Fpwm Regardless of the amount of heat generated according to the power consumption, the allowable amount of heat generated by the FET due to the switching frequency Fpwm increases. For this reason, when step S11 or S12 branches to the “NO” side, the switching circuit 310 is not overheated even if the switching frequency Fpwm is set relatively high. On the other hand, the degree of influence of motor electromagnetic noise on the noise of the entire vehicle increases as the engine rotational speed NE decreases and the operating angle A decreases, and the allowable amount of motor electromagnetic noise decreases. For this reason, when step S12 branches to the “YES” side, it is possible to make a determination that the reduction of motor electromagnetic noise should be prioritized, and the motor electromagnetic noise can be reduced by setting the switching frequency Fpwm to F2. It is planned.

  In view of the above points, the reference value NE1 set for the engine speed NE and the reference value A1 set for the operating angle A are, for example, experimentally, empirically, theoretically or simulated in advance. Based on the above, it is assumed that a sufficiently loud engine operation sound is generated with respect to the electromagnetic noise of the motor, or that the switching circuit may fall into an overheated state, or various factors that are set cooperatively in consideration of these factors. The value may be a conforming value, and the exact value has a property that can be appropriately changed according to the required performance, specifications, or destination of the vehicle, and does not affect the gist of the present invention.

  In addition, as long as the relationship of F2> F1 is established between the switching frequencies F1 and F2, the effect according to the present invention is sufficiently obtained, and specific numerical values of these switching frequencies Fpwm are described in the present invention. Does not affect

  The effect of the switching frequency control process is reasonable from the viewpoint of the response speed of the engine 200. Here, the relationship between the switching frequency Fpwm and the response of the intake valve 201 will be described with reference to FIG. FIG. 6 is a schematic characteristic diagram illustrating one characteristic of the response of the intake valve 201 to the switching frequency Fpwm. In the figure, the same parts as those in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  In FIG. 6, the response of the intake valve 201 (in short, the time required to return from the open (closed) state to the open (closed) state via the closed (open) state, in other words, The response speed is higher as the switching frequency Fpwm is higher.

  Here, when the load state of the engine 200 is accelerated from a light load to a high load or the like, the intake valve 201 is required to have a relatively high response speed. However, the switching frequency control process according to the present embodiment is used. Accordingly, since the switching frequency Fpwm is set to F2 in a light load state (that is, a small operating angle), the responsiveness of the engine 200 is improved. Further, when the load state of the engine 200 goes from a high load to a light load, the intake valve 201 is not required to have a high response speed, and the switching frequency Fpwm is set to F1 by the switching frequency control process according to the present embodiment. Even if done, there will be no problems in practice. That is, the switching frequency control process is also effective from the viewpoint of the responsiveness of the intake valve 201.

  As described above, according to the switching frequency control process according to the present embodiment, based on the engine rotational speed NE and the operating angle A of the intake valve 201, between the suppression of overheating of the switching circuit and the suppression of motor electromagnetic noise. Therefore, when the engine 200 is at a high speed and the intake valve 201 has a large working angle, the switching frequency Fpwm is relatively small, which impairs vehicle comfort. Without overheating of the switching circuit 310, the switching frequency Fpwm is relatively large when the engine 200 is at a low speed or the intake valve 201 has a small working angle, and the motor does not cause overheating of the switching circuit. Electromagnetic sound is reduced. That is, it is possible to suppress the overheating of the motor peripheral portion while suppressing a decrease in vehicle comfort.

In the present embodiment, the switching frequency Fpwm is controlled in a binary manner between F1 and F2, but this is an example, and the ECU 100 is stepwise according to the operating angle A, the lift amount L, or the like. The switching frequency Fpwm may be changed continuously or continuously. Further, in this embodiment, the engine rotational speed NE is taken into account together with the operating angle A, but the practical benefit according to the present invention is when the switching frequency Fpwm is controlled based only on the operating angle (or lift amount). Needless to say, it is also enjoyed.
<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a schematic characteristic diagram illustrating the relationship between engine sound and motor electromagnetic sound.

  In FIG. 7, FIG. 7A illustrates one change characteristic of the switching frequency Fpwm in the switching circuit 310. When the switching frequency Fpwm is changed between FpwmA and FpwmB (FpwmB> FpwmA) as shown in the figure (FpwmA → FpwmB → FpwmA...) The motor electromagnetic sound Nmt illustrated in the broken line is generated. The frequency of the motor electromagnetic sound Nmt is variable depending on the values of FpwmA and FpwmB and the switching cycle thereof.

  Here, in FIG. 7B, when the engine sound Neng changes with the characteristic illustrated in the chain line in the figure, the motor electromagnetic sound Nmt (broken line) described above has the same amplitude and reverse phase with respect to the engine sound Neng. Thus, the illustrated synthesized sound Nmix can be generated. The synthesized sound Nmix is ideally zero when the engine sound Neng and the motor electromagnetic sound Nmt have the same amplitude and a phase difference of 180 degrees.

  Thus, according to the present embodiment, by switching the switching frequency Fpwm, it is possible to generate a motor electromagnetic sound that suppresses engine sound (that is, an example of “engine noise suppression sound” according to the present invention). It is possible to suppress at least vehicle noise and ideally to zero. Therefore, it is possible to further improve the comfort of the vehicle.

  The generation of the motor electromagnetic sound Nmt according to the present embodiment does not conflict with the switching frequency control process according to the first embodiment, and may be executed in cooperation with each other.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and the control of the internal combustion engine accompanying such a change. The apparatus is also included in the technical scope of the present invention.

It is a mimetic diagram of an engine system concerning a 1st embodiment of the present invention. FIG. 2 is a schematic side cross-sectional view conceptually showing a cross-sectional configuration of the periphery of the variable valve operating apparatus in the engine system of FIG. 1. FIG. 2 is a schematic circuit diagram of an actuator in the engine system of FIG. 1. It is a typical characteristic diagram which illustrates one characteristic with respect to switching frequency Fpwm of each of a motor electromagnetic sound and FET calorific value. It is a flowchart of a switching frequency control process. It is a typical characteristic diagram which illustrates one characteristic of the response of an intake valve with respect to switching frequency Fpwm. It is a typical characteristic figure which illustrates the relation between engine sound and motor electromagnetic sound.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine system, 100 ... ECU, 200 ... Engine, 201 ... Intake valve, 210 ... Variable valve apparatus, 300 ... Actuator, 310 ... Switching circuit, 320 ... Drive motor, 400 ... Angle sensor, 600 ... First variable mechanism .

Claims (4)

A motor and driving means capable of driving the motor by PWM control, and at least one of an operating angle and a lift amount in the intake valve or the exhaust valve can be changed by a driving force applied from the motor; A control device for an internal combustion engine equipped with a variable valve gear,
A specifying means for specifying the at least one;
First control means for controlling the drive means so that the switching frequency related to the PWM control decreases and increases as at least one of the specified increases and decreases is provided. Control device. The first control unit is configured to reduce the switching frequency when at least one of the specified values is equal to or greater than a predetermined value, as compared with a case where at least one of the specified values is less than the predetermined value. The control apparatus for an internal combustion engine according to claim 1, wherein: The first control means reduces the switching frequency when at least one of the specified values is equal to or greater than the predetermined value and the engine rotation speed of the internal combustion engine is in a predetermined high rotation region. The control apparatus for an internal combustion engine according to claim 2. And further comprising second control means for controlling the driving means so as to produce engine noise suppression sound in which the frequency is synchronized with the engine noise of the internal combustion engine and the phase is reversed by continuously changing the switching frequency. The control device for an internal combustion engine according to any one of claims 1 to 3, wherein:

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