JP2015048839A - Valve timing control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve timing control device for an internal combustion engine capable of improving fuel efficiency by effectively suppressing knocking by properly controlling valve closing timing of an intake valve according to rotational frequency of an internal combustion engine, and capable of securing sufficient output especially in a high rotation region, in the internal combustion engine in which the intake valve is delayed in closing.SOLUTION: An internal combustion engine of this invention is an internal combustion engine in which a most delayed angle position of an intake valve 6 at valve closing timing IVC which can be changed by a variable lift mechanism 12 and a variable phase mechanism 13 is set on a further delayed angle side than at the timing when an air amount filled in a cylinder 3a becomes maximum, and in which the intake valve 6 is delayed in closing. In the valve timing control device, the higher the detected rotational frequency NE of the internal combustion engine 3, the further advanced angle side a most advanced angle value IVC1 of the valve closing timing IVC of the intake valve 6 is controlled to (Step 3 of Fig. 6, Fig. 10).

Description

  The present invention relates to a valve timing control device for an internal combustion engine that controls the closing timing of the intake valve via a variable valve mechanism in an internal combustion engine whose intake valve is slowly closed.

  As a conventional valve timing control device for an internal combustion engine, for example, one disclosed in Patent Document 1 is known. This internal combustion engine has a normal valve timing in which the normal closing timing of the intake valve is set to about 30 ° after the bottom dead center of the intake stroke, and the intake valve is not delayed closed. Further, this variable valve mechanism of the internal combustion engine changes the intake valve opening timing and the closing timing to the same amount, the advance side or the retard side, by changing the phase of the intake cam with respect to the crankshaft. It is configured as follows.

  In this valve timing control device, for example, in the medium load region of the internal combustion engine, the valve timing of the intake valve (open / close valve timing) is controlled as follows according to the rotation region of the internal combustion engine. First, in the low rotation region and the high rotation region, the valve timing is set to the retard side. This is because if the valve timing is set to the advance side, combustion tends to become unstable in the low rotation region, and intake inertia cannot be used in the high rotation region, and the charging efficiency is lowered. On the other hand, in the middle rotation region, such a problem is unlikely to occur. Therefore, by setting the valve timing of the intake valve to the advance side, the charging efficiency is improved and a larger output is obtained.

JP-A-7-253032

  However, when the above-described conventional control device is used for an internal combustion engine whose intake valve is slowly closed, the following problems occur. That is, in an internal combustion engine in which the intake valve is closed late, the most retarded position of the valve timing of the intake valve that is changed by the variable valve mechanism is set to the retard side of the timing at which the intake air amount becomes maximum. Compared with the above-described conventional control device, the closing timing of the intake valve is shifted to the retard side as a whole. For this reason, the amount of air blown back to the intake passage is large, and the charging efficiency is originally low. From this state, even if the valve timing of the intake valve is set to the retard side in the high speed region of the internal combustion engine as in the conventional control device, the intake air blowback amount changes to the increase side, and the intake inertia is effective. Therefore, the charging efficiency is rather lowered and the output of the internal combustion engine cannot be obtained sufficiently.

  The present invention has been made to solve the above-described problems, and in an internal combustion engine in which the intake valve is closed late, appropriately controls the closing timing of the intake valve in accordance with the rotational speed of the internal combustion engine. Accordingly, an object of the present invention is to provide a valve timing control device for an internal combustion engine that can improve fuel efficiency by effectively suppressing knocking and can secure a sufficient output particularly in a high rotation region.

  In order to achieve the above object, the invention according to claim 1 of the present application uses a variable valve mechanism (in the embodiment, the valve closing timing IVC of the intake valve 6 that is opened and closed to suck air into the cylinder 3a. Hereinafter, the same in this section) is a valve timing control device for an internal combustion engine controlled via a variable lift mechanism 12 and a variable phase mechanism 13), and the valve closing timing IVC of the intake valve 6 that can be changed by the variable valve mechanism. The most retarded angle position is set to the retarded angle side relative to the timing at which the amount of air charged in the cylinder 3a becomes maximum, and a rotation speed detecting means (crank angle sensor 20) for detecting the rotation speed NE of the internal combustion engine 3 is set. In accordance with the detected rotational speed NE of the internal combustion engine 3, the higher the rotational speed NE of the internal combustion engine 3 is, the higher the rotational speed value IVC1 of the valve closing timing IVC of the intake valve 6 is controlled to the advanced side. ( CU2, Step 3 in FIG. 6, characterized in that it comprises a 10), the.

  The internal combustion engine has a variable valve mechanism for changing the valve closing timing of the intake valve, and the most retarded position of the valve closing timing of the intake valve that can be changed by the variable valve mechanism is filled in the cylinder. The intake valve is set to be retarded from the timing at which the amount of air to be maximized is delayed. In such an internal combustion engine with a late closing of the intake valve, it has been found that the charging efficiency increases as the closing timing of the intake valve is set to the advance side as the rotational speed of the internal combustion engine increases. . As described above, when the intake valve is closed late, the closing timing of the intake valve is shifted to the retard side as a whole compared to the normal case where the intake valve is not closed, and the charging efficiency is improved. Since it is originally in a low state, even if the valve closing timing is changed from this state to the retarded angle side, the intake inertia is not exhibited effectively, but rather the change to the advanced angle side increases the charging efficiency. is there.

  The present invention is based on such a newly discovered technical point of view, and the higher the detected rotational speed of the internal combustion engine, the more the advanced angle value of the closing timing of the intake valve is controlled to the advanced angle side. By doing so, the charging efficiency can be increased, and therefore a sufficient output of the internal combustion engine can be ensured particularly in a high rotation region.

  Further, since the time per combustion cycle becomes longer as the rotational speed of the internal combustion engine is lower, knocking is likely to occur. On the other hand, according to the present invention, as the engine speed is lower, the most advanced value of the closing timing of the intake valve is controlled to the more retarded side, so knocking is effectively suppressed and a stable combustion state By ensuring the fuel consumption can be improved.

  According to a second aspect of the present invention, in the valve timing control apparatus for an internal combustion engine according to the first aspect, the control means controls the valve closing timing IVC of the intake valve 6 in accordance with the increase in the rotational speed NE of the internal combustion engine 3. The most advanced angle value IVC1 is advanced in steps (FIG. 10).

  According to this configuration, the followability of the variable valve mechanism according to the increase / decrease in the number of revolutions of the internal combustion engine is improved, and the operation of another mechanism that controls the internal combustion engine in accordance with the change in the closing timing of the intake valve. And the overall control of the internal combustion engine can be performed smoothly.

  The invention according to claim 3 is the valve timing control device for an internal combustion engine according to claim 1 or 2, further comprising load detection means (accelerator opening sensor 24) for detecting a load (required torque TRQCMD) of the internal combustion engine 3. The control means includes a valve closing timing IVC of the intake valve 6 when the detected load of the internal combustion engine is a full load (full load torque TRQWOT), and the higher the rotational speed NE of the internal combustion engine 3, the more advanced the side It is characterized by controlling to.

  According to this configuration, when the load of the internal combustion engine is a full load, the higher the rotational speed of the internal combustion engine, the closer the intake valve closing timing is controlled to the advance side. The advantage of the invention according to claim 1 that the output can be sufficiently secured according to the rotation speed of the vehicle can be obtained, and the high output demand of the driver can be satisfactorily met.

  According to a fourth aspect of the present invention, in the valve timing control device for an internal combustion engine according to any one of the first to third aspects, the control means is configured such that the load of the internal combustion engine is reduced under the same rotational speed NE of the internal combustion engine 3. When the pressure is smaller than the full load, the valve closing timing IVC of the intake valve 6 is most advanced (FIG. 8).

  When the internal combustion engine is in a full load operation state, if the valve closing timing of the intake valve is advanced too much, knocking is likely to occur and combustion efficiency decreases. According to this configuration, when the internal combustion engine has the same rotational speed, when the load of the internal combustion engine is smaller than the full load, the valve closing timing of the intake valve is advanced most, and at the full load, the most advanced position Since the control is performed more retarded, knocking can be appropriately avoided and combustion stability can be improved in the full load operation state.

1 is a diagram schematically showing a configuration of an internal combustion engine to which the present invention is applied. It is a figure which shows schematically the structure of a valve timing control apparatus. It is a figure which shows the valve lift curve of an exhaust valve, and the valve lift curve of the intake valve in a low lift mode and a high lift mode. It is a figure which shows the valve lift curve of an intake valve when it exists in the most retarded angle position and the most advanced angle position in low lift mode in the valve lift curve of an exhaust valve. It is a figure which shows the valve lift curve of the intake valve when it exists in the most retarded angle position and the most advanced angle position in the high lift mode in the valve lift curve of an exhaust valve. It is a flowchart which shows the valve timing control processing of an intake valve. It is a map for determining the lift mode of an intake valve. It is a figure which shows the relationship between a request | requirement torque and the valve closing timing of an intake valve when engine speed is the same conditions in a medium and high load area | region. It is a figure which shows the relationship between the valve closing timing of an intake valve, and a net fuel consumption rate for every load area | region. It is a figure which shows the relationship between an engine speed and the most advanced angle value of the valve closing timing of an intake valve. It is a figure which shows the relationship between an engine speed, the valve closing timing of an intake valve, and a net fuel consumption rate for every rotation area | region. It is a figure which shows the relationship between engine speed, the valve closing timing of an intake valve, and charging efficiency.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. An internal combustion engine (hereinafter referred to as “engine”) 3 shown in FIG. 1 is a DOHC type gasoline engine having, for example, four cylinders 3a (only one is shown), and is mounted on a vehicle (not shown). In each cylinder 3a, a combustion chamber 3d is formed between the piston 3b and the cylinder head 3c. In this engine 3, the geometric compression ratio based on the volume of the combustion chamber 3d and the like is relatively large and is set to 13.0 or more. An intake passage 4 and an exhaust passage 5 are connected to the combustion chamber 3d, and an intake valve 6 and an exhaust valve 7 for opening and closing these are provided at the intake port of the intake passage 4 and the exhaust port of the exhaust passage 5, respectively. .

  The engine 3 also includes a variable valve mechanism 10 that opens and closes the intake valve 6 and changes the valve timing, and a valve mechanism 11 that opens and closes the exhaust valve 7. This exhaust-side valve mechanism 11 is of a normal cam drive type, and is composed of an exhaust camshaft and an exhaust cam (not shown) integral with the exhaust camshaft, and with the rotation of the crankshaft 3e, The exhaust valve 7 is driven. Thereby, as shown in FIG. 3, the exhaust valve 7 opens at a constant valve timing according to a constant valve lift curve by the exhaust cam.

  For example, the lift (maximum lift amount) of the exhaust valve 7 is smaller than the lift of the intake valve 6 described later, and the valve opening timing EVO is set before the bottom dead center at the start of the exhaust stroke. They are set before the top dead center at the start of the intake stroke (hereinafter referred to as “intake TDC”). As shown in FIG. 3 and the like, the opening and closing of the exhaust valve 7 are defined based on the lift amount = 1 mm, and this is the same for the intake valve 6.

  On the other hand, the variable valve mechanism 10 that opens and closes the intake valve 6 includes a variable lift mechanism 12 that changes the lift of the intake valve 6 and a variable phase mechanism 13 that changes the phase of the intake valve 6.

  The variable lift mechanism 12 switches the lift of the intake valve 6 in two stages, a low lift and a high lift. The variable lift mechanism 12 includes an intake camshaft, a low-speed cam and a high-speed cam integrated with the intake camshaft, and a hydraulic switching mechanism (both not shown). The switching mechanism includes a hydraulic circuit (not shown) and A switching control valve 12a (see FIG. 2) is included. The switching control valve 12a is composed of an electromagnetic valve or the like, and controls the hydraulic pressure supplied to the hydraulic circuit according to a control signal from the ECU 2 described later, thereby driving the intake valve 6 with a low speed cam. Switch between mode and high lift mode driven by high speed cam.

  As a result, as shown in FIG. 3, in the low lift mode, the intake valve 6 opens with a lower lift according to the valve lift curve by the low speed cam. On the other hand, in the high lift mode, the intake valve 6 opens with a larger lift according to the valve lift curve by the high speed cam. Further, in the high lift mode, the opening angle period of the intake valve 6 is slightly wider than in the low lift mode, the valve opening timing IVO is on the advance side, and the valve closing timing IVC is on the retard side. Change.

  The variable phase mechanism 13 changes the relative phase (hereinafter referred to as “intake phase”) CAIN of the intake valve 6 with respect to the crankshaft 3e steplessly, and includes a phase control motor 13a (see FIG. 2) and the like. I have. The phase control motor 13a rotates the intake camshaft relative to the crankshaft 3e in accordance with a control signal from the ECU 2, and changes the relative angle between the two to change the intake phase CAIN to a predetermined latest delay. Steplessly change between the angle value and the most advanced angle value.

  4 and 5 show an example of the valve timing of the intake valve 6 set by the variable lift mechanism 12 and the variable phase mechanism 13. When the intake phase CAIN is at the most retarded angle value in the low lift mode, the valve opening timing IVO of the intake valve 6 is about 43 ° after the intake TDC, as shown by the solid line in FIG. , Approximately 76 ° after bottom dead center at the end of the intake stroke (hereinafter referred to as “intake BDC”).

  Similarly, when the intake phase CAIN is the most retarded value in the high lift mode, the valve opening timing IVO of the intake valve 6 is about 38 ° after the intake TDC, as shown by the solid line in FIG. Timing IVC is approximately 86 ° after intake BDC. Further, as shown by the one-dot chain line in FIGS. 4 and 5, in both the low lift mode and the high lift mode, when the intake phase CAIN is the most advanced angle value, compared with the most retarded angle value. The valve timing of the intake valve 6 as a whole shifts to the advance side with a magnitude equal to the operating range (about 40 °) of the variable phase mechanism 13.

  As described above, the closing timing IVC of the intake valve 6 when the intake phase CAIN is the most retarded value is about 76 ° and 86 ° after the intake BDC in the low lift mode and the high lift mode, respectively. It is set on the retard side to be larger than the timing at which the amount of air filled in is maximized. That is, in this embodiment, the engine 3 is configured as a high compression ratio engine (Miller cycle engine) in which the intake valve 6 is slowly closed. Further, the opening timing IVO of the intake valve 6 when the intake phase CAIN is the most retarded value is about 43 ° and 38 ° after the intake TDC in the low lift mode and the high lift mode, respectively. It opens slowly.

  Returning to FIG. 1, the engine 3 is provided with a spark plug 15 and a fuel injection valve 16 for each cylinder 3a. The spark plug 15 is attached to the cylinder head 3c and ignites the air-fuel mixture in the cylinder 3a by generating a spark. The fuel injection valve 16 is attached to the intake manifold of the intake passage 4 and injects fuel toward the intake port. The ignition timing of these spark plugs 15 and the fuel injection amount of the fuel injection valve 16 are set by the ECU 2 and controlled by a control signal from the ECU 2.

  A throttle valve mechanism 17 is provided in the intake passage 4. The throttle valve mechanism 17 includes a rotatable throttle valve 17a and a TH actuator 17b for driving the throttle valve 17a. The TH actuator 17b is a combination of a motor and a gear mechanism (both not shown), and the throttle valve 17a is driven in accordance with a control signal from the ECU 2 to change the opening thereof. The flow rate of air passing through 17a is controlled.

  Further, the engine 3 is provided with an EGR device 18. The EGR device 18 executes external EGR for returning a part of the exhaust gas discharged from the combustion chamber 3d to the exhaust passage 5 to the intake passage 4 side. The EGR device 18 includes an EGR passage 18a connected to the exhaust passage 5 downstream of the throttle valve 17a in the intake passage 4, an EGR valve 18b provided in the EGR passage 18a, and an EGR actuator 18c that drives the EGR valve 18b. Etc.

  The EGR actuator 18c uses a linear solenoid, and drives the EGR valve 18b in accordance with a control signal from the ECU 2 to change its lift, whereby the exhaust gas recirculation amount (hereinafter referred to as "external EGR amount"). ) Is controlled.

  A crank angle sensor 20 is provided on the crankshaft 3e. The crank angle sensor 20 outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft 3e rotates. The CRK signal is output every predetermined crank angle (for example, 1 °). The TDC signal is a signal indicating that the piston 3b is in a predetermined crank angle position slightly before the top dead center at the start of the intake stroke in any of the cylinders 3a, as in this embodiment. When the engine 3 has four cylinders, it is output every crank angle of 180 °.

  The ECU 2 calculates the engine speed NE (hereinafter referred to as “engine speed”) NE based on the CRK signal, and calculates the crank angle based on the TDC signal and the CRK signal.

  An air flow sensor 21 is provided upstream of the throttle valve 17 a in the intake passage 4, and an intake pressure sensor 22 is provided downstream. The air flow sensor 21 detects the flow rate GAIR of the air flowing through the intake passage 4 and outputs a detection signal to the ECU 2. The intake pressure sensor 22 detects the pressure PB in the intake chamber 4 a of the intake passage 4 and outputs a detection signal to the ECU 2.

  Further, the ECU 2 receives from the water temperature sensor 23 a detection signal indicating the temperature of the cooling water of the engine 3 (hereinafter referred to as “engine water temperature”) TW, from the accelerator opening sensor 24 to the depression of the accelerator pedal (not shown) of the vehicle. A detection signal representing an amount (hereinafter referred to as “accelerator opening”) AP and a detection signal representing a vehicle speed (vehicle speed) VP are input from the vehicle speed sensor 25 (see FIG. 2).

  The ECU 2 is composed of a microcomputer including a CPU, a RAM, a ROM, an I / O interface (all not shown), and the like. ECU2 discriminate | determines the driving | running state of the engine 3 according to the detection signal of various sensors 20-25 mentioned above. Further, the ignition timing of the spark plug 15, the fuel injection amount of the fuel injection valve 16, the opening degree of the throttle valve 17a, the external EGR amount by the EGR device 18 and the like are controlled according to the determined operating state, and the variable lift mechanism. 12 and the variable phase mechanism 13 are used to control the valve timing of the intake valve 6. In the present embodiment, the ECU 2 corresponds to the control means.

  FIG. 6 shows a control process of the valve timing of the intake valve 6 that is executed by the ECU 2. This process is executed every predetermined time. In this process, first, in step 1 (illustrated as “S1”, the same applies hereinafter), a required torque TRQCMD required for the engine 3 is calculated. The required torque TRQCMD is calculated by searching a predetermined map (not shown) according to the detected accelerator opening AP and vehicle speed VP.

  Next, the lift mode of the intake valve 6 by the variable lift mechanism 12 is determined to be the low lift mode or the high lift mode (step 2). The determination of the lift mode is performed by searching the map shown in FIG. 7 according to the required torque TRQCMD and the engine speed NE and taking into account the detected engine water temperature TW.

  The upper line of this map represents the full load torque TRQWOT. The full load torque TRQWOT corresponds to the required torque TRQCMD when the engine 3 is full load, that is, the accelerator pedal is fully opened. In this map, the lift mode is set to the low lift (Lo) mode in the low speed range where the engine speed NE is smaller than a first predetermined value NREF1 (for example, 1100 rpm), and the engine speed NE is set to the first predetermined value NREF1. In the middle and high rotation range which is equal to or higher than the third predetermined value NMAX corresponding to the maximum rotation speed, the high lift (Hi) mode is basically set in order to ensure a larger intake air amount.

  Further, when the engine speed NE is in a high rotation range where the second predetermined value NREF2 (for example, 3500 rpm) or more and the required torque TQRCMD is in a predetermined high load range including the full load torque TRQWOT, the lift mode is low. The lift mode is set.

  Next, a target intake phase CAINCMD that is a target value of the intake phase CAIN is calculated based on the required torque TRQCMD calculated in step 1 and the engine speed NE in accordance with the lift mode determined in step 2 (step 3). ).

  Next, by outputting a control signal based on the determined lift mode to the switching control valve 12a of the variable lift mechanism 12, the variable lift mechanism 12 is driven (step 4), and the intake valve 6 is set to the low lift mode or the high lift mode. Control to lift mode.

  Finally, the variable phase mechanism 13 is driven by outputting a control signal based on the target intake phase CAINCMD calculated in step 3 to the phase control motor 13a of the variable phase mechanism 13 (step 5), and this process is terminated. To do. Thereby, the intake phase CAIN is controlled to the target intake phase CAINCMD, and the valve timing of the intake valve 6 is controlled.

  Next, the relationship between the required torque TRQCMD and engine speed NE obtained by the valve timing control described above and the valve closing timing IVC of the intake valve 6 will be described in detail. First, in the low load region where the required torque TRQCMD is small, the valve closing timing IVC of the intake valve 6 is controlled to the most retarded angle position regardless of the engine speed NE. As shown in FIG. 9A, in the low load region, the external EGR by the EGR device 18 is not executed, and the pumping loss becomes smaller as the valve closing timing IVC is delayed. This is because the net fuel consumption rate BSFC is minimized at the retard position.

  FIG. 8 shows the relationship of the closing timing IVC of the intake valve 6 with respect to the required torque TRQCMD when the engine speed NE is the same in the middle and high load region. As shown in the figure, under this condition, the valve closing timing IVC is controlled to be more advanced as the required torque TRQCMD is larger in a region where the required torque TRQCMD is equal to or smaller than a predetermined value TRQ1 smaller than the full load torque TRQWOT. The This is due to the following reason.

  That is, in the medium load and high load regions, external EGR is executed, and a fuel efficiency effect is obtained by reducing the pumping loss, and the external EGR amount is controlled to increase as the load increases. When the valve timing IVC is on the more advanced side, the charging efficiency of air (fresh air) is increased and a good combustion state is obtained. As a result, as shown in FIGS. 9B and 9C, the valve closing timing IVC at which the minimum net fuel consumption rate BSFC can be obtained as the load increases in the medium load and high load regions is more advanced. This is to shift to. 9C and 9D, the region on the retarded angle side from the cross mark X is too late, so the amount of air to be filled is insufficient, so that stable combustion and output are maintained. Indicates an area that cannot.

  As shown in FIG. 8, the closing timing IVC of the intake valve 6 is controlled to the most advanced angle value IVC1 when the required torque TRQCMD is the predetermined value TRQ1, and the required torque TRQCMD is equal to the predetermined value TRQ1 and the full load torque. In the region between TRQWOT, the greater the required torque TRQCMD, the more retarded control is performed. This is because, in the full load state, the external EGR is stopped. Therefore, as shown in FIG. 9D, if the valve closing timing IVC is advanced too much, knocking occurs, and the combustion efficiency is reduced due to the energy loss caused thereby. This is because the valve closing timing IVC at which the minimum net fuel consumption rate BSFC is obtained as a result of the decrease is on the retard side from the high load region. The dotted line in FIG. 9 (d) shows the net fuel consumption rate BSFC when the influence of knocking is ignored as a reference.

  Note that the valve closing timing IVC is controlled with the same tendency as in FIG. 8 with respect to the required torque TRQCMD under the same engine speed NE with respect to the engine speed NE other than that illustrated in FIG. The In this case, the predetermined value TRQ1 at which the valve closing timing IVC is controlled to the most advanced angle value IVC1 is set to a higher required torque TRQCMD as the engine speed NE is higher.

  As described above, by controlling the valve closing timing IVC of the intake valve 6 according to the required torque TRQCMD, it is possible to obtain the best fuel efficiency according to the required torque TRQCMD.

  Next, the relationship between the engine speed NE and the valve closing timing IVC of the intake valve 6 obtained by the valve timing control described above will be described. First, as described above, in the low load region, the valve closing timing IVC of the intake valve 6 is controlled to the most retarded position with respect to all the engine speeds NE. An effect is obtained.

  FIG. 10 shows the relationship between the engine speed NE and the most advanced value IVC1 of the closing timing IVC of the intake valve 6 controlled as described above. NREF1 in the figure is a first predetermined value of the engine speed NE that is used as a threshold value when the lift mode of the intake valve 6 is switched between the low lift mode and the high lift mode in the map of FIG. . As shown in the figure, the most advanced angle value IVC1 of the valve closing timing IVC is controlled stepwise toward the advanced angle side as the engine speed NE is higher. Although not shown, when the engine 3 is at full load, the valve closing timing IVC of the intake valve 6 is gradually increased toward the advance side as the engine speed NE is higher, as in the case of the most advanced value IVC1. Be controlled. Hereinafter, the reason will be described with reference to FIGS.

  FIG. 11 shows the relationship between the valve closing timing IVC of the intake valve 6 and the net fuel consumption rate BSFC for each rotation region. First, when the geometric compression ratio is high as in the engine 3 of the present embodiment, knocking is likely to occur originally in the middle and high load regions, and particularly in the low rotation region shown in FIG. Therefore, knocking is likely to occur even when the amount of intake air is small. For this reason, the net fuel consumption rate BSFC considering the knocking effect is minimized when the valve closing timing IVC is on the retard side.

  On the other hand, in the middle and high speed regions shown in FIGS. 11B and 11C, the higher the engine speed NE, the shorter the time per combustion cycle and the less likely knocking occurs. The valve closing timing IVC at which the net fuel consumption rate BSFC is obtained shifts further to the advance side.

  FIG. 12 shows the relationship between the engine speed NE and the efficiency of charging air into the cylinder 3a ηc for each valve closing timing IVC of the intake valve 6. Among these, FIG. 7B is a comparative example in a normal case where the intake valve is not delayed closed. In this case, the charging efficiency ηc is larger in the low rotation region as the intake valve closing timing is advanced, whereas in the high rotation region, the charging efficiency ηc increases as the intake inertia increases. The relationship is reversed, and the charging efficiency ηc increases as the closing timing of the intake valve is retarded.

  On the other hand, when the intake valve 6 is slowly closed as in the present embodiment, the charging efficiency ηc is equal to the intake valve 6 regardless of the engine speed NE, as shown in FIG. The closer the valve closing timing IVC is, the larger the delay timing becomes. As described above, when the intake valve 6 is closed late, the valve closing timing is shifted to the retard side as a whole, and the charging efficiency ηc is originally in a low state. This is because even if the timing is changed to the retard side, the intake inertia is not effectively exhibited, but rather, the charging efficiency ηc is increased when the timing is changed to the advance side.

  Therefore, in the middle and high load region, the higher the engine speed NE is based on the relationship between the valve closing timing IVC of the intake valve 6 corresponding to the engine speed NE, the net fuel consumption rate BSFC, and the charging efficiency ηc as described above. By setting the most advanced angle value IVC1 of the closing timing IVC of the intake valve 6 and the closing timing IVC of the intake valve 6 when the engine 3 is fully loaded to the more advanced side, the minimum considering the knocking The net fuel consumption rate BSFC can be obtained, and higher filling efficiency ηc can be obtained.

  As described above, according to the present embodiment, as shown in FIG. 10, as the engine speed NE is higher, the most advanced value IVC1 of the closing timing IVC of the intake valve 6 is controlled to the more advanced side. . As a result, knocking is effectively suppressed and a stable combustion state is ensured, thereby improving fuel efficiency and obtaining a higher charging efficiency, thereby ensuring sufficient output of the engine 3 particularly in a high rotation region. Can do.

  Further, when the engine 3 is at full load, the higher the engine speed NE is, the more the valve closing timing IVC of the intake valve 6 is controlled to be advanced, so that in the full load operation state, according to the engine speed NE. The effect of sufficiently securing the output of the engine 3 can be obtained, and the high output demand of the driver can be satisfactorily met.

  Further, as described above, when the engine 3 is in the high rotation / high load region, the lift mode of the intake valve 6 is set to the low lift mode with the later valve opening timing IVO. By reducing the amount of internal EGR due to overlap with the intake valve 6, the charging efficiency ηc can be further increased and a higher output can be obtained.

  Further, as the engine speed NE increases, the most advanced angle value IVC1 of the closing timing IVC of the intake valve 6 or the closing timing IVC of the intake valve 6 when the engine 3 is fully loaded is stepwise. Advance to. As a result, the followability of the variable phase mechanism 13 according to the increase / decrease in the engine speed NE is improved, and other mechanisms for controlling the engine 3 according to the change in the valve closing timing IVC, such as the throttle valve mechanism 17 and the EGR device. 18 can be suppressed, and the overall control of the engine 3 can be performed smoothly.

  In the middle and high load range, when the required torque TRQCMD is smaller than the full load torque TRQWOT under the same engine speed NE, the valve closing timing IVC of the intake valve 6 is advanced most, and the full load torque TRQWOT Since control is sometimes performed on the retard side with respect to the most advanced value, knocking can be appropriately avoided and combustion stability can be improved in the full load operation state.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the embodiment, the required torque TRQCMD is used as the load of the engine 3, but instead, it is detected by another appropriate parameter representing the load of the engine 3, for example, the accelerator opening AP or the airflow sensor 21. An air flow rate GAIR or the like may be used.

  In the embodiment, the most advanced angle value IVC1 of the closing timing IVC of the intake valve 6 is controlled as shown in FIG. 10 according to the engine speed NE, and the closing timing IVC of the intake valve 6 is Although control is performed as shown in FIG. 8 according to the required torque TRQCMD, the latter control may be omitted. Furthermore, although the variable lift mechanism 12 is used in combination with the variable phase mechanism 13 as the variable valve mechanism of the intake valve 6 in the embodiment, the latter may be omitted.

  Further, the embodiment is an example in which the present invention is applied to a gasoline engine for a vehicle. However, the present invention is not limited to this, and various industrial industrial applications such as a diesel engine for a vehicle and an internal combustion engine for a ship are also included. The present invention can be widely applied to internal combustion engines. Furthermore, the detailed configuration shown in the embodiment is merely an example, and can be appropriately changed within the scope of the gist of the present invention.

2 ECU (control means)
3 Internal combustion engine 3a Cylinder 6 Intake valve 12 Variable lift mechanism (variable valve mechanism)
13 Variable phase mechanism (Variable valve mechanism)
20 Crank angle sensor (rotational speed detection means)
24 Accelerator opening sensor (load detection means)
IVC Intake valve closing timing IVC1 Intake valve closing timing maximum advance value CAIN Intake phase NE Engine speed (speed of internal combustion engine)
TRQCMD Required torque (load of internal combustion engine)

Claims (4)

A valve timing control device for an internal combustion engine that controls a valve closing timing of an intake valve that is opened and closed to suck air into a cylinder via a variable valve mechanism,
The most retarded position of the closing timing of the intake valve that can be changed by the variable valve mechanism is set to be retarded from the timing at which the amount of air charged in the cylinder becomes maximum,
A rotational speed detection means for detecting the rotational speed of the internal combustion engine;
Control means for controlling the most advanced angle value of the closing timing of the intake valve to a more advanced side as the rotational speed of the internal combustion engine is higher in accordance with the detected rotational speed of the internal combustion engine. An internal combustion engine valve timing control device.   2. The control unit according to claim 1, wherein the most advanced value of the closing timing of the intake valve is advanced in a stepwise manner as the rotational speed of the internal combustion engine increases. The valve timing control device for an internal combustion engine. A load detecting means for detecting a load of the internal combustion engine;
The control means controls the valve closing timing of the intake valve when the detected load of the internal combustion engine is full load to a more advanced side as the rotational speed of the internal combustion engine is higher. The valve timing control device for an internal combustion engine according to claim 1 or 2.   The control means is configured to advance the closing timing of the intake valve the most when the load of the internal combustion engine is smaller than a full load under the same rotational speed of the internal combustion engine. Item 4. The valve timing control device for an internal combustion engine according to any one of Items 1 to 3.

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