JP2008025383A - Control system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control system of an internal combustion engine which efficiently and effectively controls the tension caused in a transmission means such as a timing belt and the like under operating conditions. <P>SOLUTION: In the engine system 10, an ECU 100 executes a valve-timing control processing. In the processing, the ECU 100 obtains by a strain sensor 221 a strain in a crank pulley 220 rotating integrally with a crankshaft 219, which is caused in response to changes in effective tension Te of the timing belt 222, and obtains a peak value Tep of the effective tension. If the peak value Tep of the effective tension is greater than a prescribed threshold Tepth, the ECU 100 controls an intake-side VVT controller 300 and an exhaust-side VVT controller 400 to increase the overlap of an intake valve 203 and an exhaust valve 206, and decrease the peak value Tep of the effective tension acted on the timing belt 222. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technical field of a control device for an internal combustion engine that controls an internal combustion engine including a variable valve operating device such as a VVT (Variable Valve Timing).

  An apparatus for controlling the tension of a timing belt in an internal combustion engine has been proposed (see, for example, Patent Document 1). According to the tension adjusting device for an endless conduction band in an engine disclosed in Patent Document 1 (hereinafter referred to as “prior art”), the rotational angular vibration displacement amount is calculated from the rotational state of the cam pulley detected by the rotational state detecting means. The static tension of the timing belt can be controlled to an appropriate value by calculating and controlling the tensioner so that the rotational angular vibration displacement amount falls within a predetermined range.

  In addition, a technique has been proposed in which the contact portion of the tensioner is changed according to the engine speed so that the vibration frequency is outside the resonance range (see, for example, Patent Document 2).

JP-A-10-274052 JP-A-5-18447

  Unlike the static tension, the tension of the timing belt during operation of the internal combustion engine varies, for example, between processes of the internal combustion engine. Therefore, when the tension of the timing belt is simply increased or decreased by the tensioner, there is a possibility that the tension in a certain process exceeds the upper limit value or the tension in the certain process falls below the lower limit value. That is, the conventional technique has a technical problem that it is difficult to appropriately control the tension of a transmission means such as a timing belt during operation of the internal combustion engine.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine that can efficiently and effectively control the tension generated in the transmission means during operation of the internal combustion engine.

  In order to solve the above-described problems, a control apparatus for an internal combustion engine according to the present invention includes a drive shaft that rotates with combustion of fuel, an intake cam shaft, an intake cam fixed to the intake cam shaft, and rotation of the intake cam shaft. An intake valve that is driven by the intake cam to open and close, an exhaust camshaft, an exhaust cam that is fixed to the exhaust camshaft, an exhaust valve that is driven to open and close by the exhaust camshaft, and the intake and Transmission means for transmitting the power of the drive shaft to at least one of the intake and exhaust cam shafts so that the exhaust cam shaft rotates in synchronization with the rotation of the drive shaft, and the intake and exhaust valves An internal combustion engine control apparatus for controlling an internal combustion engine having variable valve operating means capable of changing an opening / closing timing of at least one valve, wherein tension generated in the transmission means during operation of the internal combustion engine Specifying means for specifying an index value corresponding to an effective tension obtained by subtracting a tension generated in the transmission means when the internal combustion engine is stopped; and the variable valve actuating so that the effective tension changes based on the specified index value. And a control means for controlling the means.

  The “internal combustion engine” in the present invention has, for example, a plurality of cylinders, and is generated when an air-fuel mixture containing various fuels such as gasoline, light oil or alcohol is burned in the combustion chamber of each of the plurality of cylinders. It is a concept that encompasses an engine that is configured to be able to convert explosive force into rotation of a drive shaft that can take the form of, for example, a crankshaft, for example, via a piston, a connecting rod, etc. This refers to a 2-cycle or 4-cycle reciprocating engine.

  An internal combustion engine according to the present invention includes an intake valve for defining an intake air amount related to intake air sucked into a cylinder, and an exhaust valve for discharging exhaust gas including burned gas, unburned fuel, and the like out of the cylinder. Are respectively opened and closed by driving a valve lifter, a rocker arm or the like corresponding to each valve according to the cam profile of each cam, for example. The intake and exhaust cams are fixed to the intake and exhaust cam shafts, for example, mechanically, physically, mechanically, or electrically, and are configured to be rotatable according to the rotation of the intake and exhaust cam shafts.

  The intake and exhaust camshafts are configured to rotate in synchronization with the rotation of the drive shaft. Here, “synchronously” is a concept encompassing a state in which there is a considerable correlation between the rotation of the drive shaft and the rotation of the intake and exhaust camshafts. For example, various characteristics such as rotation speed, rotation cycle or rotation phase and various characteristics such as rotation speed, rotation cycle or rotation phase related to the rotation of the intake and exhaust camshafts are maintained and fixed in a preset or estimated relationship. This is a good idea. Such rotation of the intake and exhaust camshafts can be achieved, for example, by transmission means that can take various forms such as a timing belt or a timing chain, so that the power of the drive shaft (that is, the driving force related to the rotation) is This is realized by being transmitted to at least one of the shafts.

  Note that the transmission means may transmit the power of the drive shaft to both the intake and exhaust cams, or to the intake cam shaft or the exhaust cam shaft, as “at least one shaft”. . In the case where the power is transmitted only to one shaft, the power of the drive shaft is transmitted from one shaft to which the power is transmitted to the other shaft through various physical, mechanical, mechanical or electrical means, for example. It may be transmitted to the shaft. Of course, this is also a category of the mode in which each of the intake and exhaust camshafts rotates in synchronization with the rotation of the drive shaft. In view of the fact that the intake and exhaust camshafts rotate in synchronization with the rotation of the drive shaft, the intake and exhaust valves that are driven to open and close by the intake and exhaust camshafts fixed to the intake and exhaust camshafts, respectively, It opens and closes in synchronization with the rotation.

  The internal combustion engine in the present invention is provided with variable valve means such as VVT or various devices equivalent thereto, and is configured to be able to change the opening / closing timing of at least one of the intake and exhaust valves. The mechanical, physical, mechanical or electrical configuration of such variable valve means may be free as long as the opening / closing timing of at least one valve can be changed. For example, the intake and exhaust valves may be Considering that the intake and exhaust cams fixed to the intake and exhaust camshafts open and close the drive shaft, the relative rotation phase of the camshaft with respect to the rotation phase of the drive shaft, for example, the vane rotor fixed to the camshaft The piston is in contact with the inner helical gear fixed to the camshaft via a helical spline, for example, by moving it forward or retarding according to the hydraulic pressure or the electric driving force of the hydraulic fluid or the electric driving force. You may have the structure changed by moving to a cam shaft direction according to typical driving force. Of course, for example, an electric driving force may be applied to the cam fixed to the cam shaft directly or indirectly.

  Here, in view of the fact that the power of the drive shaft is transmitted to at least one of the shafts via the transmission means during the operation of the internal combustion engine, the tension generated in the transmission means during the operation of the internal combustion engine (hereinafter referred to as “during operation”). "Tension" or "Tension during operation of transmission means") must be within an appropriate range. More specifically, the tension during operation ensures at least a value large enough to drive the camshaft without any problem, while the transmission means is damaged or damaged, or a physical or mechanical failure equivalent thereto, or excessive. It is preferable that it is small enough not to generate vibration or the like.

  On the other hand, during the operation of the internal combustion engine, there are various processes such as suction, compression, expansion (explosion), and exhaust for each cylinder, and the operating tension changes between these processes or within these processes. For example, in the valve opening period of the intake and exhaust valves (that is, a period corresponding to the period from the valve opening timing to the valve closing timing), it is necessary to physically drive (for example, push down) the valve lifter, the rocker arm, and the like with a cam, for example. For this reason, a tension is more likely to be required than in other periods, and the operating tension tends to increase. As for the valve opening period, the operating tension is basically maximum at the maximum lift of the valve.

  On the other hand, when resonance conditions determined according to various factors such as the shape, length, mass, and three-dimensional arrangement of various parts and members constituting the internal combustion engine are satisfied, resonance occurs in the transmission means, The operating tension may change significantly. When this kind of resonance occurs, or when the intake or exhaust valve opening period overlaps when this kind of resonance occurs, the operating tension of the transmission means needs to be quickly reduced.

  Here, in particular, with a means such as a belt tensioner which can change the tension generated in the transmission means only uniformly and directly controls the transmission means, for example, the operating tension is relaxed so as not to become excessively large. In such a case, for example, there may occur a situation where the operating tension is insufficiently short, for example, when the process is switched or when the resonance condition is deviated. In addition, at least the driver feels uncomfortable in view of the fact that the operating tension can change in real time, and in some cases it is difficult to follow the changing speed of the tension obtained via the tensioner with the changing speed of the operating tension. There is a high possibility that an unnatural tension change will occur to the extent that occurs. Further, even if it is attempted to finely control the operating tension during one cycle of the internal combustion engine by such means, for example, the load on the drive system for driving the belt tensioner or the control system for controlling the drive system tends to be excessive. In addition, enlargement of the system configuration is inevitable. From a more practical point of view, it is very difficult to control the operating tension in real time. That is, it is technically difficult to properly maintain the operating tension of the transmission means.

  Therefore, in the control apparatus for an internal combustion engine according to the present invention, the operating tension of the transmission means is efficiently and effectively controlled as follows. That is, according to the control apparatus for an internal combustion engine according to the present invention, during operation, for example, various processing units such as an ECU (Electronic Control Unit), various controllers, various computer systems such as a microcomputer device, and the like are employed. The index value corresponding to the effective tension generated in the transmission means during the operation of the internal combustion engine is specified by the action of the specifying means obtained.

  Here, the “effective tension” according to the present invention is a tension generated due to the operation of the internal combustion engine, and the tension of the transmission means during the operation of the internal combustion engine, that is, the tension during the operation, A value obtained by subtracting the tension (hereinafter referred to as “static tension at rest” or “tension at rest of transmission means” as appropriate) acting on the transmission means at times (ie, occurring at the transmission means regardless of whether the internal combustion engine is operating). is there.

  In addition, the “index value corresponding to the effective tension” according to the present invention refers to the effective tension itself, or a change in which the change corresponds to a change in the effective tension one to one, many to one, one to many, or many to many. It is a concept that includes index values such as index values that have a considerable correspondence with the effective tension. Therefore, the index value corresponding to the effective tension can be obtained in real time when the stationary tension is known in advance, or based on the control amount of the means that can change the stationary tension such as a tensioner, etc. In such a case, the operating tension, or the change in operating tension may be one or more index values corresponding to the change in operating tension one-to-one, many-to-one, one-to-many, or many-to-many. The specific operation according to the specifying means of the present invention may have a single type of operation process or a plurality of types of operation processes. For example, the specifying means may specify the effective tension itself, or after specifying various index values other than the effective tension, may finally specify the effective tension based on the specified index value. .

  Note that “specific” in the present invention refers to, for example, detecting a physical numerical value or an electrical signal corresponding to the physical numerical value directly or indirectly via some detecting means, or a suitable storage means in advance. Selecting or estimating a corresponding numerical value from a stored map or the like, deriving from the detected physical numerical value or electrical signal or a selected or estimated numerical value according to a preset algorithm or calculation formula, Alternatively, this is a broad concept encompassing simply obtaining the value detected, selected, estimated or derived as an electric signal or the like.

  When the index value corresponding to the effective tension is specified by the specifying means, for example, the specified index is determined by the control means that can take various aspects such as various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device. The variable valve operating means is controlled so that the effective tension changes based on the value.

  In view of the definition of the effective tension, the change in the operating tension of the transmission means between the respective processes of the internal combustion engine or in each process is significantly brought about by the change in the effective tension. Further, as described above, the change characteristic of the operating tension is closely related to the opening periods of the intake and exhaust valves. Therefore, the effective tension can be changed without directly controlling the transmission means itself by changing the opening / closing timing that defines the valve opening period that can be a variation factor of the effective tension through the control of the variable valve means. In this case, it is possible to control the operating tension of the transmission means more precisely and quickly than in the case where the transmission means itself is a control target. Further, in view of the definition of the effective tension, since the change in the effective tension does not affect the stationary tension, it is possible to optimize the stationary tension in advance, for example. Alternatively, when the tension at rest can be optimized in real time by a tensioner or the like, the tension required to rotationally drive at least one of the shafts in synchronization with the rotation of the drive shaft is ensured when changing the effective tension. . That is, according to the control device for an internal combustion engine according to the present invention, it is possible to efficiently and effectively control the operating tension of the transmission means.

  The control mode of the variable valve means based on the value corresponding to the effective tension is such that the change in operating tension of the transmission means caused by the control of the effective tension of the transmission means is caused by the mechanical, physical or electrical change of the transmission means. The internal, mechanical, physical, electrical, or internal combustion engine that occurs at least without adversely affecting general conditions, preferably as long as these conditions can be improved to some extent or due to the operating tension of the transmission means. It is not limited at all as long as it does not adversely affect the chemical or sensory or sensational state at least to the extent that it cannot be ignored in practice.For example, based on experiments, empirical experiments, simulations, etc. It may be determined so that the operating tension falls within a predetermined range, or the maximum value of the operating tension does not exceed the predetermined value.

  In addition, in terms of other requirements in an internal combustion engine or a vehicle equipped with the internal combustion engine, the opening timings of the intake and exhaust valves are often optimized in advance according to the operating conditions of the internal combustion engine. The control of the opening / closing timing based on the time tension may cause a decrease in torque, a decrease in drivability, and the like depending on circumstances even if the state of the transmission means can be improved. Therefore, in consideration of these other requirements, the control of the opening / closing timing may be suppressed so that any trouble does not occur in practice, or the degree of trouble is suppressed to an acceptable level in practice. Good.

  In one aspect of the control apparatus for an internal combustion engine according to the present invention, the transmission means includes a timing belt or a timing chain.

  The mode of the transmission means is not limited as long as the power of the drive shaft can be transmitted to at least one of the shafts so that at least one of the shafts is synchronized with the rotation of the drive shaft, but when the form of the timing belt or the timing chain is adopted. Is preferable because it can effectively transmit the power of the drive shaft to at least one of the shafts.

  When the transmission means takes the form of a timing chain or a timing chain as described above, the transmission means is wound around, for example, a pulley or a sprocket that rotates integrally with the drive shaft on the drive shaft side, and the cam shaft side. In this case, it may be wound around, for example, a pulley or a sprocket that rotates integrally with the camshaft.

  In another aspect of the control device for an internal combustion engine according to the present invention, the transmission means is wound around a drive shaft side rotation assisting member that can rotate integrally with the drive shaft, and the specifying means includes the index value. As at least a part of the above, an amount of distortion generated in the drive shaft side rotation auxiliary member in accordance with the effective tension during operation of the internal combustion engine is specified.

  According to this aspect, the transmission means is wound around the drive shaft side rotation auxiliary member that can take the form of, for example, a crank pulley or a crank sprocket, and more preferably provided corresponding to at least one of the shafts. It is also wound around a camshaft side auxiliary rotation member that can take the form of a cam pulley or timing sprocket, for example. The specifying means specifies the amount of distortion generated in the drive shaft side rotation auxiliary member. In the drive shaft side rotation auxiliary member, distortion corresponding to the effective tension is generated in the process of transmitting the rotation of the drive shaft to the transmission means, and the amount thereof increases or decreases according to the magnitude of the effective tension, for example. Therefore, the amount of distortion is suitable for use as a criterion for specifying the effective tension or for changing the effective tension.

  “Wound” means that at least a part of the winding target is rotated along the rotation direction of the winding target in order to promote the operation of the transmission means synchronized with the rotation of the winding target (for example, the drive shaft side rotation auxiliary member). This is a concept that includes the state of contact, and includes, for example, a state in which the winding target does not go around.

  The control mode of the control means based on the specified strain amount is not limited as long as the operating tension can be changed efficiently and effectively through the change in the effective tension. If the amount and the control amount of the variable valve means are associated with each other one-to-one, many-to-one, one-to-many, or many-to-many, it is possible based on the control amount corresponding to the specified amount of distortion. The variable valve means may be controlled, or the control means may determine the control amount of the variable valve means individually and specifically based on the amount of distortion in consideration of the operating state of the internal combustion engine each time. . Alternatively, the specified amount of strain is used only as a criterion for determining whether or not the effective tension is changed, for example, and preferably, and the control of the variable valve means is, for example, constant or indefinite. It may be performed according to feedback control based on the feedback gain, and may be gradually changed until the effective tension satisfies a predetermined condition.

  In this aspect, the specifying unit may further specify the effective tension as at least a part of the index value based on the specified amount of strain.

  In this case, since the specifying unit finally specifies the effective tension through a plurality of types of specifying steps, the control unit may, for example, make the effective tension fall within a desired value, within a desired range, or exceed the upper limit value. Thus, the variable valve operating means can be controlled more accurately.

  In another aspect of the control device for an internal combustion engine according to the present invention, the control device further includes a determination unit that determines whether the effective tension is larger than a predetermined type upper limit value based on the specified index value, When it is determined that the effective tension is greater than the upper limit value, the control means controls the variable valve means so that the effective tension decreases.

  According to this aspect, for example, it is determined whether or not the effective tension is greater than the upper limit value by the determination unit that can take various aspects such as various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device. The control means controls the variable valve operating means so that the effective tension decreases when it is determined that the effective tension is larger than the upper limit value. The opening and closing timing of the intake and exhaust valves can affect not only the effective tension but also the power performance of the internal combustion engine and environmental performance such as emissions and fuel consumption. There is a possibility that it will not be satisfied.

  Therefore, when the variable valve mechanism is controlled for the purpose of lowering the effective tension when the effective tension is larger than the upper limit value in this way, there is a practical problem with the influence on power performance and environmental performance. It is possible to control the tension during operation of the transmission means to a desired value or within a desired range while suppressing to a certain extent, which is extremely beneficial.

  Note that the “predetermined upper limit value” means, for example, that a physical or mechanical load applied to the transmission means due to the operating tension causes a physical or mechanical failure to the transmission means immediately or in the near future. The value of the effective tension that can be determined or estimated to be so large that it may be inviting to the driver, or that the vibration of the internal combustion engine due to the operating tension may be transmitted to the driver as a sense of incongruity Alternatively, it is a concept that includes values for which there is a reasonable reason that the effective tension should be reduced, including the value of the effective tension that can be estimated.

  Such an upper limit value of the effective tension can be estimated or estimated in advance, for example, experimentally, empirically, or based on a simulation or the like, and the correlation between the effective tension and the above-described problems occurring in the transmission means is known. In this case, it may be one or a plurality of fixed values set in advance based on such correlation, and each time, for example, various processing units such as ECU, various controllers or various computer systems such as a microcomputer device Depending on the setting means that can take various aspects such as the above, it may be an indefinite value that is specifically set individually based on an appropriate algorithm or calculation formula based on the state of the internal combustion engine or the transmission means at that time.

  For example, if the operating tension that may cause a problem in the transmission means is a fixed value, the upper limit value of the effective tension may inevitably change according to the stationary tension. Therefore, in such a case, a plurality of upper limit values of the effective tension may be set using the stationary tension as a parameter. In this case, the stationary tension may be grasped in advance as a fixed value, or when the stationary tension is maintained at an appropriate value each time by a tensioner or the like, it is grasped based on the control amount of the tensioner. Also good.

  In another aspect of the control apparatus for an internal combustion engine according to the present invention, a predetermined type of control amount related to the variable valve means when the variable valve means is controlled to change the effective tension is set in the internal combustion engine. Learning means is further provided for learning in association with the operating condition defined as related to the effective tension, and the control means controls the variable valve means based on the learned control amount.

  According to this aspect, for example, when the effective tension is changed by, for example, decreasing the effective tension by a learning unit that can take various aspects such as various processing units such as an ECU, various controllers or various computer systems such as a microcomputer device, it is possible. The control amount of the variable valve means, for example, the target value (for example, target angle) of the opening / closing timing of at least one valve, the amount of displacement between the opening / closing timing value and the target value at that time, etc. correspond to the operating conditions of the internal combustion engine Along with learning. The control means controls the variable valve operating means based on the learned control amount. Such a control amount is not limited as long as it has some correspondence with the opening / closing timing of at least one of the valves.

  Here, “learn” means that the corresponding value is temporarily or permanently stored in an appropriate storage means and is updatable, and at a constant or indefinite update timing or when a certain condition is satisfied. Is a concept representing updating the corresponding value. Therefore, the learning performed by the learning means in this embodiment is, for example, when the opening / closing timing of at least one valve is changed via the control of the variable valve means at the timing when the effective tension should be reduced, This is intended to include storing the operating conditions such as the engine speed and the final control amount related to the variable valve operating means in association with each other and updating them as appropriate.

  The operating condition of the internal combustion engine related to learning is a concept encompassing operating conditions related to the effective tension, and refers to, for example, the engine speed of the internal combustion engine. As described above, the generation condition of the resonance that can change the effective tension relatively large can be defined by the engine speed. In this case, it is detected in advance that the resonance is generated by such learning. It is also possible to do. In addition, even when there is another factor that causes a change in the effective tension in the transmission means, not only resonance, it is possible to detect the occurrence in advance from the operating conditions of the internal combustion engine.

  Therefore, according to this aspect, for example, when the operating condition of the internal combustion engine satisfies an operating condition that can cause a resonance or other change in effective tension, preferably an excessively large change, or in the near future In the case of estimation, etc., it becomes possible to quickly control the variable valve means using the control amount learned in the past.For example, a change amount of the effective tension or a period in which the effective tension is in an undesirable range, for example, The opening / closing timing can be reduced as compared with the case where feedback control is performed so that the effective tension converges to a predetermined value according to a preset initial value, feedback gain, and the like. Such an effect related to learning is remarkably effective, for example, when the internal combustion engine is in a transition period and the control of the effective tension cannot follow the normal opening / closing timing control.

  In another aspect of the control apparatus for an internal combustion engine according to the present invention, the storage for storing the operating condition defined as related to the effective tension in the internal combustion engine, wherein the effective tension is greater than a predetermined type of upper limit value. The control means controls the variable valve operating means so that the effective tension decreases when the operating condition corresponds to the stored operating condition.

  For example, the operating tension (substantially equivalent to the effective tension) in a state in which the internal combustion engine is operating normally indicates in advance how the operating tension changes in accordance with, for example, various operating conditions of the internal combustion engine. It is possible to obtain in advance by experiments or simulations performed to clarify whether the transmission means resonates under what operating conditions of the internal combustion engine. It can be obtained in advance by experiments or simulations conducted to clarify the presence or absence of the resonance with respect to the operating conditions and the degree thereof. In such a case, whether or not the effective tension becomes larger than the upper limit value can be predicted to some extent in advance.

  According to this aspect, the operation condition of the internal combustion engine in which the effective tension exceeds the upper limit value is stored in the storage means (the operation condition such as the engine speed described above may be used), and the control means has the operation condition of the internal combustion engine. When this stored operating condition is met, the variable valve means is controlled to reduce the effective tension. Note that “applicable” is not limited to matching the real-time operating conditions at that time, but is a broad concept including cases where the operating conditions are likely to match in the near future. For example, when a certain engine speed is known as a resonance condition and the engine speed of the internal combustion engine starts to rise suddenly from a region below the engine speed (for example, a transient period, etc.), It can be considered that the engine speed passes. Such a case also falls under the “applicable” category according to this aspect.

  According to this aspect, at least a part of the operating conditions for reducing the effective tension is known in advance, and the effective tension is set to a desired value or a desired range as compared with the case where no memory of this kind is made. The time for convergence can be shortened. That is, the operating tension can be controlled efficiently and effectively.

  The concept according to this aspect does not contradict the concept related to learning described above, and can be executed cooperatively. That is, for example, the stored operating condition according to this aspect can be used as at least a part of the initial value related to learning by the learning means described above, and the physical or mechanical configuration of the internal combustion engine can be used. This is particularly suitable when the environmental conditions surrounding the internal combustion engine change over time from the time of adaptation, because high reliability is ensured by such learning.

  In another aspect of the control apparatus for an internal combustion engine according to the present invention, when the effective tension is reduced, the control means has a period in which the valve opening period of the intake valve and the valve opening period of the exhaust valve overlap each other. The variable valve means is controlled so that the overlap amount to be expressed increases.

  For example, in an internal combustion engine having four or more cylinders, there are many cylinders that enter the exhaust process at the timing when one cylinder enters the intake process. In this case, from the viewpoint of the effective tension of the transmission means, the conditions for increasing the effective tension overlap. In addition, since there is a high possibility that any cylinder will reach the intake stroke at a constant cycle, the effective tension will inevitably repeat increasing and decreasing periodically for each period corresponding to each step. The peak value will be reached at maximum lift.

  According to this aspect, when reducing the effective tension, the amount of overlap between the intake and exhaust valves is increased. When increasing the overlap amount, the opening timing of the intake valve is advanced or the closing timing of the exhaust valve is delayed. Alternatively, the opening timing of the intake valve is advanced and the closing timing of the exhaust valve is retarded. Therefore, when viewed as the whole internal combustion engine, the amount of deviation in the maximum lift timing increases between the cylinder that has undergone the intake process and the cylinder that has undergone the exhaust process.

  Therefore, it is avoided that the peak value of the effective tension overlapping with the maximum lift timing or relatively large values according to the peak value overlap, and the peak value decreases as the entire effective tension. At this time, in view of the change characteristic of the effective tension, for example, the minimum value is higher and the maximum value is lower than in the case where the overlap amount is zero, and the flat change characteristic is drawn as a whole. That is, the degree of change in the effective tension during the operation of the internal combustion engine is reduced, and various problems that can occur in the transmission means or vibrations that can occur in the internal combustion engine are effectively suppressed.

  When the overlap amount is increased, the control amount of the variable valve means corresponding to the overlap amount or the overlap amount and the change amount of the effective tension are associated with each other and stored in advance in the appropriate storage means. Alternatively, at least as long as the overlap amount increases, the actual overlap amount may be derived in a feedback manner based on the effective tension specified each time. Further, as long as the overlap amount can be increased, the advance angle amount and the retard angle amount of each of the intake valve and the exhaust valve, the control ratio of both, and the like are not limited at all.

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

<Embodiment>
Preferred embodiments of the present invention will be described below with reference to the drawings as appropriate.

<1: First Embodiment>
<1-1: 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.

  In FIG. 1, the engine system 10 includes an ECU 100 and an engine 200.

  The ECU 100 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown), and controls the overall operation of the engine system 10. It is comprised so that it may function as an example of an apparatus. The ECU 100 is configured to be able to execute a valve timing control process to be described later according to a control program stored in the ROM.

  The engine 200 is a gasoline engine as an example of the “internal combustion engine” according to the present invention configured to function as a power source of a vehicle (not shown). As shown in the figure, the engine 200 is an in-line four-cylinder engine in which four cylinders 202 are arranged in series in a cylinder block 201. The engine 200 uses a connecting rod (not shown) and a crankshaft 219 (an example of the “drive shaft” according to the present invention) to reciprocate a piston (not shown) that occurs when a mixture of air and fuel burns inside each cylinder. And is configured to be able to be converted into a rotational motion via (not shown in FIG. 1). In the following, an essential configuration of the engine 200 will be described together with an outline of its operation. For the purpose of preventing the explanation from becoming complicated, in the following explanation, only one cylinder will be explained unless otherwise specified.

  In the combustion chamber in the cylinder 202, an air-fuel mixture of air supplied through the intake manifold 216 and fuel injected from an injector (not shown) in an intake port (not shown) communicating with the intake manifold 216 is mixed. The air is sucked through the individual intake valves 203 (that is, an example of the “intake valve” according to the present invention). At this time, the air-fuel mixture is supplied to the combustion chamber while the intake valve 203 is open.

  Inside the cylinder, the air-fuel mixture burns by the ignition operation by the spark plug 205 in the combustion process. The burned air-fuel mixture is discharged to the exhaust port as exhaust during the valve opening period of two exhaust valves 206 communicating with an exhaust port (not shown). Such exhaust is discharged to the exhaust pipe 210 via an exhaust manifold 208 communicating with the exhaust port. In the exhaust pipe 210, for example, a catalyst device 209 such as an HC adsorption cylinder, a three-way catalyst, an oxidation catalyst, or a NOx occlusion reduction catalyst is installed, and the exhaust exhausted through the exhaust manifold 208 is purified. It has a configuration.

  The intake pipe 211 is a tubular member that communicates with the intake manifold 216 described above. The intake air guided to the intake manifold 216 through the intake pipe 211 is configured to be filtered in the process of passing through the air cleaner 212 installed on the intake pipe 211.

  In addition, an air flow meter 213 is installed at the rear stage (cylinder side) of the air cleaner 212. The air flow meter 213 is configured to be able to detect the mass flow rate of the intake air, and the detected mass flow rate is always grasped by the ECU 100 electrically connected to the air flow meter 213.

  A throttle valve 214 is installed in the intake pipe 211. The throttle valve 214 is an electronically controlled valve, and is configured such that its opening / closing operation is controlled by a throttle valve motor (not shown). The throttle valve motor is electrically connected to the ECU 100, and the driving force is controlled by the ECU 100. The ECU 100 can control the opening / closing state of the throttle valve 214 by drivingly controlling the throttle valve motor according to the accelerator opening degree, the vehicle speed, the engine speed of the internal combustion engine, etc. It is configured. Since the throttle valve 214 is not mechanically connected to the accelerator pedal, the ECU 100 can also control the open / close state of the throttle valve 214 regardless of the driver's accelerator pedal operation. The opening of the throttle valve 214 (throttle opening) is detected by a throttle opening sensor 215 provided in the vicinity of the throttle valve 214, and is electrically connected to the throttle opening sensor 215. The ECU 100 is always grasped.

  The opening / closing operation of the intake valve 203 is controlled by an intake cam 204 fixed to an intake camshaft 217 (an example of an “intake camshaft” according to the present invention). The intake camshaft 217 is rotatably supported by a cylinder head and a bearing cap disposed on the cylinder block 201. An intake side VVT controller 300 is provided at one end of the intake camshaft 217. The intake side VVT controller 300 is electrically connected to the ECU 100 and has a configuration in which the operation is controlled by the ECU 100 at a higher level. The intake cam associated with the rotation angle of the crankshaft 219 is controlled by the ECU 100. The valve timing of 204 (that is, an example of the “opening / closing timing” according to the present invention) can be changed. That is, the intake side VVT controller 300 constitutes an example of “variable valve operating means” according to the present invention. An intake side timing pulley 225 is fixed to a part of the intake side VVT controller 300. The intake side timing pulley 225 and the intake side VVT controller 300 will be described later.

  The opening / closing operation of the exhaust valve 206 is controlled by an exhaust cam 207 fixed to an exhaust camshaft 218 (an example of an “exhaust camshaft” according to the present invention). The exhaust camshaft 218 is rotatably supported by a cylinder head and a bearing cap disposed on the cylinder block 201. An exhaust side VVT controller 400 is provided at one end of the exhaust camshaft 218. The exhaust-side VVT controller 400 is electrically connected to the ECU 100, and has an arrangement in which the operation is controlled by the ECU 100. The exhaust cam associated with the rotation angle of the crankshaft 219 is controlled by the ECU 100. The valve timing 207 (that is, an example of the “opening / closing timing” according to the present invention) can be changed. That is, the exhaust side VVT controller 400 constitutes another example of the “variable valve operating means” according to the present invention. An exhaust side timing pulley 226 is fixed to a part of the exhaust side VVT controller 400. The exhaust side timing pulley 226 and the exhaust side VVT controller 400 will be described later.

  Here, with reference to FIG. 2, detailed configurations of the engine 200, the intake side VVT controller 300, and the exhaust side VVT controller 400 will be described. FIG. 2 is a schematic cross-sectional view of the engine 200 as viewed from the VVT controller side in FIG. 1 when the cylinder block is viewed in the extending direction of the intake and exhaust camshafts. In the figure, the same reference numerals are given to the same portions as those in FIG. 1, and the description thereof will be omitted as appropriate.

  In FIG. 2, a crank pulley 220 is fixed to an end of a crankshaft 219 that extends in a direction perpendicular to the paper surface. The crank pulley 220 is an example of the “drive shaft side rotation assisting member” according to the present invention that is configured to be able to rotate integrally with the crankshaft 219. In the vicinity of the crank pulley 220, a strain sensor 221 configured to be able to detect the amount of physical strain generated in the detection target portion set on the crank pulley 220 is disposed. The strain sensor 221 is electrically connected to the ECU 100, and the detected amount of strain of the crank pulley 220 is configured to be provided to a valve timing control process described later by the ECU 100.

  A timing belt 222 which is an example of the “transmission means” according to the present invention is wound around the crank pulley 220. A plurality of gear teeth (not shown) are formed on the surface of the timing belt 222 that is in contact with the crank pulley 220, and these gear teeth are the crank pulley in a state where the timing belt 222 is wound around the crank pulley 220. 220 is engaged with gear teeth (not shown) formed on the outer peripheral surface of the crank pulley 220 at a contact portion with 220. Therefore, the timing belt 222 is configured to be sent in a certain direction along with the rotation of the crank pulley 220 accompanying the rotation of the crankshaft 219.

  The timing belt 222 is wound around the intake-side timing pulley 225 and the exhaust-side timing pulley 226 in a state where appropriate tension is maintained by the auxiliary pulleys 223 and 224 that can be rotated in the same manner as the crank pulley 220. A plurality of gear teeth (not shown) are formed on the outer periphery of each of the intake side timing pulley 225 and the exhaust side timing pulley 226 similarly to the crank pulley 220, and is fitted to the above-described gear teeth of the timing belt 222. is doing. Accordingly, the intake side timing pulley 225 and the exhaust side timing pulley 226 can rotate in a certain direction as the timing belt 222 is sent out.

  Next, the configuration of the intake side VVT controller 300 and the exhaust side VVT controller 400 will be described with reference to FIG. The intake side VVT controller 300 includes a housing 310, a vane rotor 320, and a liquid chamber 330. The exhaust-side VVT controller 400 includes a housing 410, a vane rotor 420, and a liquid chamber 430.

  The housing 310 is a rotating body fixed to the intake side timing pulley 225 with, for example, a bolt or the like. The housing 310 is configured to be able to rotate integrally with the intake side timing pulley 225 as the intake side timing pulley 225 rotates.

  The vane rotor 320 is a rotating body that is fixed to one end portion of the intake-side camshaft 217 with a bolt through a stopper, and is rotatably accommodated in the housing 310. The vane rotor 320 is configured to be able to rotate integrally with the intake side camshaft 217.

  A plurality of (three chambers in FIG. 2) liquid chambers 330 are formed inside the housing 310, and are configured to be filled with hydraulic fluid. Each of the plurality of liquid chambers 330 is formed by a plurality of (three in FIG. 2) vanes formed on the outer peripheral portion of the vane rotor 320, and an advance chamber and a retard chamber (reference numerals are omitted, respectively). The lead-out line according to (1) shows a retarded angle chamber). The advance chamber and the retard chamber are each supplied with hydraulic fluid via a hydraulic fluid supply system (not shown) including a flow path (not shown).

  The housing 410 is a rotating body fixed to the exhaust side timing pulley 226 with, for example, a bolt or the like. The housing 410 is configured to be able to rotate integrally with the exhaust side timing pulley 226 as the exhaust side timing pulley 226 rotates.

  The vane rotor 420 is a rotating body fixed to one end of the exhaust-side camshaft 218 with a bolt via a stopper, and is rotatably accommodated in the housing 410. The vane rotor 420 is configured to be able to rotate integrally with the exhaust camshaft 218.

  A plurality of liquid chambers 430 are formed inside the housing 410 (three chambers in FIG. 2), and are configured to be filled with hydraulic fluid. Each of the plurality of liquid chambers 430 is formed by a plurality of (three in FIG. 2) vanes formed on the outer peripheral portion of the vane rotor 420, so that an advance chamber and a retard chamber (reference numerals are omitted respectively). The lead line indicates a retarding chamber). The advance chamber and the retard chamber are each supplied with hydraulic fluid via a hydraulic fluid supply system (not shown) including a flow path (not shown).

  Although not shown in FIG. 2, the above-described hydraulic fluid supply system in the intake-side VVT controller 300 and the exhaust-side VVT controller 400 is generally configured as follows. The hydraulic fluid supply system may be provided independently of each other for the intake side VVT controller 300 and the exhaust side VVT controller 400, or at least a part of them may be shared.

  The hydraulic fluid supply system includes an advance chamber delivery including a flow channel for supplying the hydraulic fluid to the advance chamber, a retard chamber delivery including a flow channel for supplying the hydraulic fluid to the retard chamber, and the hydraulic fluid. For circulating and supplying the oil to these deliveries, hydraulic pressure control valves such as OCV (Oil Control Valve) for switching the supply mode of hydraulic fluid, and driving the valve body of the hydraulic pressure control valve, such as solenoid It comprises a valve body drive means that can take the form of such a drive means, a control system that controls the drive state of the hydraulic fluid supply system, and the like. In addition, the control system is configured to be controlled by the ECU 100 at a higher level.

  The pump and the valve body drive means are driven by a drive system such as a motor or an actuator, which is a part of the control system. In the hydraulic fluid supply system, it is possible to supply hydraulic fluid to each of the advance chamber and the retard chamber in each of the plurality of fluid chambers according to the valve body position of the hydraulic pressure control valve driven by the drive system. It has become.

<1-2: Operation of Embodiment>
<1-2-1: Valve timing control by VVT controller>
In the intake-side VVT controller 300 and the exhaust-side VVT controller 400, valve timing control is executed mainly according to the two types of control modes described below by the action of the hydraulic fluid supply system described above under the control of the ECU 100. The intake side VVT controller 300 and the exhaust side VVT controller 400 have the same operation related to the valve timing control. Therefore, for the purpose of preventing the explanation from becoming complicated, the following description will be made with respect to the intake side VVT controller 300. I will do it.

<1-2-1-1: Holding mode>
In FIG. 2, the valve body of the hydraulic pressure control valve is controlled to a predetermined holding position in a state where a hydraulic pressure of a predetermined value or more is applied to the advance chamber and the retard chamber of the liquid chamber 330 via the hydraulic fluid supply system. When it is done, the hold mode is activated. In the holding mode, since the hydraulic pressure in the advance chamber and the retard chamber is maintained, the vane rotor 320 is fixed to the housing 310 by the hydraulic pressure in both the advance chamber and the retard chamber. Accordingly, the rotation of the housing 310 accompanying the rotation of the crankshaft 219 is transmitted to the vane rotor 320 via the hydraulic fluid, and the vane rotor 320 rotates in synchronization with the crankshaft 219. At this time, since the vane rotor 320 is fixed to the intake-side crankshaft 217, in the holding mode, the intake camshaft 217 is integrated with the vane rotor 320 while maintaining a constant rotational phase difference from the rotational phase of the crankshaft 219. Driven by rotation. That is, in the holding mode, the valve timing of the intake valve 203 is held.

<1-2-1-2: Feedback mode>
When the hydraulic pressure in the advance chamber and the retard chamber is changed, the vane rotor 320 rotates in the advance direction and the retard direction in accordance with the degree of both of the fluid pressures within a predetermined movable range. At this time, the rotation phase of the intake camshaft 217 inevitably changes to the advance side or the retard side with respect to the rotation phase of the crankshaft 219, and the intake air defined by the intake cam 204 fixed to the intake camshaft 217. The valve timing of the valve 203 changes.

  In feedback mode (hereinafter referred to as “F / B mode” where appropriate), ECU 100 refers to a map stored in advance in ROM and obtains optimal valve timing according to the operating conditions of engine 200 at that time. The target displacement angle corresponding to the difference with the valve timing of the current intake valve 203 is calculated, and a signal corresponding to the feedback current value is supplied to the drive system that drives the valve drive means to control the valve drive means To do. As a result, in the F / B mode, the rotational phase difference between the intake camshaft 217 and the crankshaft 219 converges in a feedback manner to a value corresponding to the target displacement angle, and the valve timing converges to the target value.

<1-2-2: Effective tension of timing belt>
The tension of the timing belt 222 is maintained at a constant value (or a constant range) by a tensioner (not shown) in FIG. 2 when the engine 200 is stationary. On the other hand, during the operation period of the engine 200, an effective tension due to the structure and operation of the engine 200 acts on the timing belt 222 in addition to the stationary tension. Unlike the stationary tension, the effective tension changes according to the operating state of the engine 200. Therefore, the operating tension obtained by adding the effective tension to the stationary tension also changes according to the operating state of the engine 200.

  Here, with reference to FIG. 3, the change in the effective tension acting on the timing belt 222 will be described. FIG. 3 is a schematic diagram showing the change characteristic of the effective tension of the timing belt 222 in the engine 200 for each cylinder.

  In FIG. 3, four types of characteristic diagrams in which the vertical axis represents the effective tension Te and the horizontal axis represents the crank angle are arranged in the vertical direction. These correspond to each of the four cylinders 202 (here, expressed as first, second, third, and fourth cylinders for convenience), and the first cylinder ("#" 1 "), the fourth cylinder (" # 4 "in the figure), the second cylinder (" # 2 "in the figure), and the third cylinder (" # 3 "in the figure). In FIG. 3, when the crank angle is 0 ° (hereinafter, referred to as “reference point” where appropriate), the piston in the first cylinder is in an expansion BDC (Bottom Death Center), and the exhaust process is performed. The state of being greeted is shown. The engine 200 is configured such that each cylinder sequentially reaches each step in a state where the crank angle is 180 degrees out of phase. Therefore, at the reference point, the fourth, second and third cylinders are undergoing expansion, compression and intake processes, respectively.

  In FIG. 3, the valve timings of the intake and exhaust valves are set so that the intake valve 203 and the exhaust valve 206 are opened at the start of the intake process and the exhaust process, respectively, and are closed at the end. This shows a case where the valve overlap amount between the intake valve 203 and the exhaust valve 206 is zero.

  In the engine 200, as already described, the intake side timing pulley 225 and the exhaust side timing pulley 226 are rotationally driven by the timing belt 222. Each pulley is indirectly fixed to the corresponding camshaft (that is, via the housing, the hydraulic fluid, the vane rotor, etc. described above). On the other hand, the load applied to the cam fixed to the camshaft changes when the intake and exhaust valves are driven. Accordingly, the effective tension Te acting on the timing belt 222 wound around each timing pulley changes according to the driving state of each valve. More specifically, as shown in the figure, the effective tension Te changes in the intake process and the exhaust process, and takes a peak value Te1 at the maximum lift time of the intake and exhaust valves.

  The effective tension Te is also generated in processes other than the intake and exhaust processes (that is, mainly the compression and expansion processes), but the effective tension is significantly increased in the intake and exhaust processes. In order to prevent complication, the timing belt 222 has a steady effective value Te0 (Te0 << Te1) other than the period during which the intake and exhaust valves are driven (corresponding to the intake and exhaust processes in FIG. 3). Is acting.

  Next, the effective tension acting on the timing belt 222 will be further described with reference to FIG. FIG. 4 is a schematic diagram showing a change characteristic of the resultant effective tension generated in the timing belt 222. 4 that are the same as those in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  In FIG. 4, the vertical axis and the horizontal axis are the effective tension Te and the crank angle as in FIG. As shown in FIG. 3, in the period corresponding to the crank angle of 180 ° from the reference point, the first cylinder is in the exhaust process and the third cylinder is in the intake process, which is in the middle of each period. When the crank angle is 90 °, the lift amount of each valve is maximized. Accordingly, the peak value of the effective tension Te acting on the timing belt 222 at the time corresponding to the crank angle of 90 ° is the illustrated Te2 corresponding to “2Te1 + 2Te0” obtained by adding the peak value Te1 and the steady value Te0 for each cylinder. Become.

  Here, in the engine 200, one of the cylinders sequentially enters the intake and exhaust processes with the crank angle being 180 ° out of phase, so the effective tension Te is (90 + 180 × j) ° (however, from the reference point) , J = 0, 1, 2,..., N) The peak value Te2 is taken at a crank angle apart. On the other hand, the effective tension Te takes the lowest value at a crank angle away from the reference point by (180 × k) ° (where k = 0, 1, 2,... N), and the value is steady for each cylinder. The resulting Te3 is equivalent to 4Te0 obtained by adding the values Te0.

  On the other hand, the factor causing the change in the effective tension is not limited to the driving of the intake and exhaust valves. For example, the timing belt 222 may resonate when a resonance condition determined by the shape, material, arrangement, and the like of the component members constituting the engine 200 is satisfied. For example, if the peak of effective tension that changes with the change characteristics described above at the time of such resonance overlaps, the value of effective tension becomes excessive, and the amount of change in tension at rest is small enough to be regarded as zero, constant, or constant. If considered, the value of the operating tension is inevitably excessive.

  If the operating tension is excessive, there is a high possibility that various problems such as damage or breakage of the timing belt 222 or acceleration of wear will occur. Therefore, the operating tension acting on the timing belt 222 is at least this kind. It needs to be controlled to such an extent that no malfunction occurs. Therefore, in the present embodiment, the ECU 100 efficiently and effectively controls the operating tension by controlling the effective tension of the timing belt 222 by executing the valve timing control process.

  Here, the details of the valve timing control process will be described with reference to FIG. FIG. 5 is a flowchart of the valve timing control process.

  In FIG. 5, the ECU 100 acquires the basic valve timing (step A10). Here, the basic valve timing is associated in advance with the operating conditions of the engine 200 (for example, the engine speed, the accelerator opening degree, the required output, etc.), and is stored in the ROM as a map. The valve timing is obtained from the map. Further, the ECU 100 controls the intake side VVT controller 300 and the exhaust side VVT controller 400 as described above so that the valve timings of the intake valve 203 and the exhaust valve 206 become the basic valve timing (that is, the F / B mode). And switching the holding mode as appropriate).

  When the valve timing is controlled to the basic valve timing, the ECU 100 acquires the distortion amount of the crank pulley 220 from the output value of the distortion sensor 221 (step A11). When the strain amount of the crank pulley 220 is acquired, the ECU 100 further acquires the peak value Tep of the effective tension Te of the timing belt 222 (step A12).

  Here, the amount of distortion generated in the crank pulley 220 changes according to the effective tension of the timing belt 222 wound around the crank pulley 220. The ECU 100 holds in advance a map that prescribes a correspondence relationship between the strain amount and the effective tension in the ROM, and in the processing according to step A12, the effective tension corresponding to the obtained strain amount is referred to the map. The peak value Tep is acquired by acquiring Te and monitoring the acquired effective tension Te continuously for a certain period.

  When the peak value Tep of the effective tension is acquired, the ECU 100 determines whether or not the peak value Tep is larger than a preset threshold value Tepth (step A13). Here, the threshold Temperature is a value that is defined in advance as the possibility of causing the above-described various problems in the timing belt 222, and is based on experiments or simulations that can correlate the effective tension with the occurrence state of the timing belt defects. For example, the value is set to a value corresponding to the occurrence limit of the malfunction, or a value having a certain margin less than the occurrence limit.

  Note that the tension acting on the timing belt 222 when the engine 200 is operating is the operating tension, and if any malfunction occurs in the timing belt 222, the operating tension significantly affects. However, the stationary tension is normally a fixed value, and even if it is variable, it is usually not changed in a range that is large enough to cause a malfunction of the timing belt 222. In practice, the operating tension is substantially the same as the timing belt 222. Whether or not it is large enough to cause the above problem can be sufficiently defined by the effective tension irrespective of the stationary tension. However, the determination mode of the threshold is not limited to that of the present embodiment, and may be variable according to the value of the stationary tension, for example.

  As a result of the determination, if the peak value Tep of the effective tension is equal to or less than the threshold value Tepth (step A13: NO), the ECU 100 determines the valve timing as the valve timing at that time (that is, the basic valve timing at this time) ( Step A15), valve timing is not changed.

  On the other hand, when the peak value Tep of the effective tension is greater than the threshold value Tepth (step A13: YES), the ECU 100 increases the valve overlap amount between the intake valve 203 and the exhaust valve 206 (step A14). Here, the relationship between the valve overlap amount and the effective tension will be described with reference to FIG. FIG. 6 is a schematic diagram showing the correlation between the peak value of the effective tension and the valve overlap amount.

  In FIG. 6, the vertical axis and the horizontal axis represent the peak value Tep and the valve overlap amount VOL of the effective tension Te, respectively. As shown in the figure, the peak value Tep tends to decrease as the valve overlap amount VOL increases. The effective tension Te is, for example, Tea in the illustrated VOLa, and Teb (Teb <Tea <Tea in the illustrated VOLb (VOLa <VOLb)). ).

  Here, with reference to FIG. 7, the relationship between the valve overlap amount and the effective tension will be described. FIG. 7 is a schematic diagram showing the change characteristic of the effective tension in the timing belt 222 of the engine 200 for each cylinder when the valve overlap amount is increased. In the figure, the same reference numerals are given to the same portions as those in FIG. 3, and the description thereof will be omitted as appropriate.

  In FIG. 7, the valve timing of the intake valve 203 is changed to the 45 ° advance side compared to that illustrated in FIG. 3 (see the thick broken line in the drawing), and the valve timing of the exhaust valve 206 is also set to the 45 ° delay side. It has been changed (see thick broken line in the figure). Therefore, the valve overlap amount of both is 90 °. Note that the valve overlap amount according to FIG. 7 is a schematic diagram for clearly illustrating the change in the effective tension, and the valve overlap amount actually controlled is not limited to this.

  As shown in the figure, when the peak value Tep of the effective tension Te is seen for each cylinder, the amount of increase in the valve overlap amount (the amount of valve overlap exists in comparison with FIG. 3) It increases from the peak value Te1 and becomes Te4 in the figure. However, by increasing the valve overlap amount of the intake and exhaust valves in this way, a situation in which the peak value Te1 overlaps between the first to fourth cylinders is avoided, so that it actually acts on the timing belt 222. The peak value Tep of the effective tension to be reduced is smaller than Te2 according to FIG.

  Here, this will be described with reference to FIG. FIG. 8 is another schematic diagram showing a change characteristic of the resultant effective tension generated in the timing belt 222. 8 that are the same as those in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  As shown in FIG. 4, since the peak time between the cylinders is shifted due to an increase in the valve overlap amount, the peak value Tep of the effective tension acting on the timing belt 222 is Te4 shown in FIG. However, as the valve overlap amount increases, the peak time increases, and the crank angle corresponding to the peak time is (90 + 90 × l) ° (where l = 0, 1, 2,... n) Distant crank angle. On the other hand, the minimum value of the effective tension is Te5 in the figure corresponding to “Te1 + 3Te0”, and occurs at a crank angle away from the reference point by (45 + 90 × m) ° (where m = 0, 1, 2,... N). It will be. As described above, by increasing the valve overlap amount, it is possible to shift the peak timing of the effective tension in different cylinders, so that the peak value of the effective tension acting on the timing belt 222 can be decreased. Become.

  Returning to FIG. 5, when each VVT controller is controlled so that the valve overlap amount increases in the process according to step A14, the ECU 100 returns the process to step A11 and acquires the amount of distortion generated in the crank pulley 220. Then, a series of processes relating to the comparison of the peak values Tep of the effective tension is repeated. In the course of such a loop process, when the peak value Tep falls below the threshold value Tepth (step A13: NO), the process proceeds to step A15.

  Here, the valve overlap amount is gradually changed by the valve timing control in the F / B mode described above. For example, the ECU 100 sets the target displacement angle of the valve timing based on the current valve timing, and controls each VVT controller to obtain the target displacement angle, thereby gradually advancing the intake and exhaust valves, respectively. And retard. At each valve timing corresponding to the target displacement angle, a comparison is made between the peak value Tep and the threshold Tepth. Finally, the valve timing is a value corresponding to the target displacement angle at which the effective tension peak value Tep is less than or equal to the threshold Tepth. To be determined. Further, for example, the correspondence between the difference between the peak value and the threshold value and the overlap amount to be realized is experimentally, empirically, or based on simulations in advance, while minimizing the change in effective tension and When the peak value is set so as not to exceed the threshold value, the target displacement amount of the valve timing may be set more appropriately based on the corresponding relationship. That is, as long as the peak value of the effective tension can be decreased by finally increasing the valve overlap amount, the control mode of each VVT controller and the control timing ratio of the intake and exhaust valves are not limited at all.

  When the valve timing related to the intake and exhaust valves is set to a value that can reduce the peak value Tep of the effective tension of the timing belt 222 to be equal to or less than the threshold Tepth by the process related to Step A15, the ECU 100 determines the operating conditions of the engine 200. It is determined whether or not has been changed (step A16). Since the unexpected change in the effective tension peak value Tep is mainly caused by resonance, the effective tension Te increases or decreases when the operating conditions associated with the occurrence of resonance, such as the engine speed, change, for example. Etc., it is possible to change. Therefore, when the operating condition of engine 200 has not changed (step A16: NO), ECU 100 repeatedly executes the process according to step A16, substantially waits for the process, and operates the operating condition of engine 200. Is changed (step A16: YES), the processing is returned to step A10, the valve timing is once returned to the basic valve timing, and a series of processing is repeated.

  As described above, according to the valve timing control process according to the present embodiment, the effective tension acting on the timing belt 222 is acquired in real time, and the peak value of the effective tension is applied to the timing belt 222 in some physical or mechanical manner. When it is determined that a problem occurs or the vibration state of the engine 200 is large enough to deteriorate beyond the allowable value, the valve overlap amount of the intake valve 203 and the exhaust valve 206 is increased, and the effective tension Te is increased. The peak value can be reduced. At this time, since the change in effective tension does not affect the stationary tension, the operating tension of the timing belt 222 does not fall below the required value required to drive each camshaft. That is, the operating tension of the timing belt 222 can be controlled efficiently and effectively.

<2: Second Embodiment>
In the first embodiment, in the valve timing control process, the ECU 100 acquires the peak value Tep of the effective tension at a constant or indefinite period and uses it for comparison with the threshold value Tepth. Is unique due to the shape, mass, spatial arrangement, etc. of components and members in the engine 200. The peak value Tep of the effective tension of the timing belt 222 can exceed the above-described threshold value mainly at the time of resonance of the timing belt 222. Therefore, by storing the resonance condition in an appropriate storage unit in advance, the efficiency can be improved. Valve timing control is possible. Here, with reference to FIG. 9, a second embodiment of the present invention based on such a purpose will be described. FIG. 9 is another flowchart of the valve timing control process. In the figure, the same reference numerals are given to the same portions as those in FIG. 5, and the description thereof will be omitted as appropriate.

  In FIG. 9, when the basic valve timing is acquired, the ECU 100 determines the presence or absence of a learning value (step B10). In the present embodiment, the ECU 100 stores in advance a value of the engine speed of the engine 200 in which resonance can occur as a resonance condition in the ROM, and separately in a rewritable storage means such as a RAM. The engine speed when the valve timing has been changed in order to reduce the effective tension in the past (that is, the processing equivalent to that in the first embodiment is executed) is the control amount of each VVT controller at that time, for example, The valve timing (or displacement amount from the basic valve timing) of the intake valve 203 and the valve timing (or displacement amount from the basic valve timing) of the exhaust valve 206 are stored in an updatable manner in association with each other. That is, the ECU 100 continuously learns various conditions regarding the reduction of the peak value of the effective tension.

  In the process related to step B10, the ECU 100 learns by determining whether the engine speed at that time is a condition learned in the past or a resonance condition already stored in the ROM in advance. Determine if a value exists. Note that the initial value of the valve timing is set in advance in the resonance condition stored in the ROM.

  When the learning value does not exist (step B10: NO), the ECU 100 shifts the process to step A11, and the peak value Tep of the effective tension is set to the threshold value Teth based on the distortion amount of the crank pulley 220 as in the first embodiment. The valve timings of the intake valve 203 and the exhaust valve 206 are controlled so as not to exceed (that is, the valve overlap amount is appropriately increased). On the other hand, when the learning value exists (step B10: YES), the ECU 100 reflects the learning value (step B11).

  Here, “reflect the learned value” means that the final valve timing of the intake and exhaust valves realized by the control executed in the past or the initial value or the like associated with the resonance condition described above is used as a control target. It means setting and realizing such valve timing through control of each VVT controller. That is, by reflecting the learning value in this way, the effective tension Te of the timing belt 222 ideally converges to an appropriate value that is equal to or lower than the threshold value Temperature and near the threshold value Temperature.

  However, since the actual change in the effective tension may not necessarily coincide with such a learning value or a matching value, after reflecting the learning value in this way, the ECU 100 executes the processing after step A11, By reflecting the learning value, it is determined whether or not the peak value Tep of the effective tension is an appropriate value. Of course, when the value does not converge to an appropriate value, the peak value is reduced by the control related to the F / B mode of each VVT controller as in the first embodiment.

  Finally, when the valve timing is determined by the processing according to step A15, the ECU 100 determines whether or not the learning value is being updated (step B12). The learning value update condition is a condition that requires the learning value to be updated.For example, when the effective tension is reduced at an engine speed that has not been learned in the past, or the learning value is appropriate. This refers to cases where there was no such thing. When it is not the learning value update condition (step B12: NO), the ECU 100 executes the process according to step A16, and when it is the learning value update condition (step B12: YES), the ECU 100 updates the learning value. (Step B13). When the learning value is updated, the process proceeds to step A16.

  As described above, according to the valve timing control process according to the second embodiment, the intake and exhaust valves when the resonance condition is stored in advance and the valve overlap amount adjustment control related to the reduction of the effective tension has been performed in the past. Therefore, the operation time until the desired valve timing based on the effective tension is reached can be shortened.

  Therefore, for example, even during a period in which it is difficult to follow the above-described feedback control of valve timing in accordance with changes in engine operating conditions, such as a transition period, the effective tension can be quickly reduced, and the physical or mechanical timing belt 222 can be reduced. Generation of excessive malfunction and excessive vibration of the engine 200 is suppressed. That is, by controlling the effective tension more efficiently and effectively, the operating tension can be controlled more efficiently and effectively.

  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.

1 is a block diagram of an engine system according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the engine when the cylinder block is viewed from the VVT controller side in the extending direction of the intake and exhaust camshafts in FIG. 1. It is a schematic diagram showing the change characteristic of the effective tension of a timing belt for every cylinder. It is a schematic diagram showing the change characteristic of the resultant force of the effective tension generated in the timing belt. It is a flowchart of the valve timing control process which ECU performs in the engine system of FIG. It is a schematic diagram showing the correlation between the peak value of the effective tension and the valve overlap amount. It is a schematic diagram showing the change characteristic of the effective tension of a timing belt for every cylinder when the valve overlap amount is increased. It is another schematic diagram showing the change characteristic of the resultant force of the effective tension generated in the timing belt. It is a flowchart of the valve timing control process which concerns on 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine system, 100 ... ECU, 200 ... Engine, 203 ... Intake valve, 206 ... Exhaust valve, 217 ... Intake camshaft, 218 ... Exhaust camshaft, 219 ... Crankshaft, 220 ... Crank pulley, 221 Strain sensor, 222 ... timing belt, 225 ... intake side timing pulley, 226 ... exhaust side timing pulley, 300 ... intake side VVT controller, 310 ... housing, 320 ... vane rotor, 400 ... exhaust side VVT controller, 410 ... housing, 420 ... vane rotor.

Claims (8)

A drive shaft that rotates as the fuel burns, an intake cam shaft, an intake cam that is fixed to the intake cam shaft, an intake valve that is driven by the intake cam as the intake cam shaft rotates and opens and closes, an exhaust cam shaft, and the exhaust An exhaust cam fixed to the camshaft, an exhaust valve that is driven by the exhaust cam to open and close as the exhaust camshaft rotates, and the intake and exhaust camshafts rotate in synchronization with the rotation of the drive shaft. Transmission means for transmitting the power of the drive shaft to at least one of the intake and exhaust camshafts, and variable valve operating means capable of changing the opening and closing timing of at least one of the intake and exhaust valves A control device for an internal combustion engine for controlling the internal combustion engine provided,
A specifying means for specifying an index value corresponding to an effective tension obtained by subtracting a tension generated in the transmission means when the internal combustion engine is stopped from a tension generated in the transmission means during operation of the internal combustion engine;
And a control means for controlling the variable valve means so that the effective tension changes based on the specified index value. The control device for an internal combustion engine according to claim 1, wherein the transmission unit includes a timing belt or a timing chain. The transmission means is wound around a drive shaft side rotation auxiliary member that can rotate integrally with the drive shaft,
The specification unit is configured to specify, as at least a part of the index value, an amount of distortion generated in the drive shaft side rotation auxiliary member according to the effective tension during operation of the internal combustion engine. 3. A control device for an internal combustion engine according to 2. The control device for an internal combustion engine according to claim 3, wherein the specifying unit further specifies the effective tension as at least a part of the index value based on the specified amount of strain. Further comprising a determination means for determining whether or not the effective tension is greater than a predetermined type upper limit value based on the specified index value;
5. The control unit according to claim 1, wherein when the effective tension is determined to be greater than the upper limit value, the control means controls the variable valve operating means so that the effective tension decreases. The control apparatus for an internal combustion engine according to claim 1. When the variable valve means is controlled to change the effective tension, a predetermined type of control amount related to the variable valve means corresponds to an operating condition defined as related to the effective tension in the internal combustion engine. And further includes a learning means for learning,
The control device for an internal combustion engine according to any one of claims 1 to 5, wherein the control means controls the variable valve means based on the learned control amount. Further comprising storage means for storing operating conditions defined as related to the effective tension in the internal combustion engine, wherein the effective tension is greater than a predetermined type of upper limit;
The control means controls the variable valve means so that the effective tension decreases when the operating condition corresponds to the stored operating condition. The control apparatus for an internal combustion engine according to the item. When the effective tension is reduced, the control means controls the variable valve means so that an overlap amount representing a period in which the intake valve opening period and the exhaust valve opening period overlap is increased. It controls. The control apparatus of the internal combustion engine as described in any one of Claim 1 to 7 characterized by the above-mentioned.

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