JP2900607B2 - Control device for engine with variable intake and exhaust - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a valve train of an internal combustion engine provided with an intake / exhaust valve operation switching means, and a low speed cam and a high speed cam selectively drive, stop or suppress the intake / exhaust valve by the means. The present invention relates to a control device for an engine with a variable intake / exhaust valve mechanism, which is configured to perform the following.

BACKGROUND ART During operation of an internal combustion engine, a variable intake / exhaust valve capable of selectively switching a low-speed cam or a high-speed cam to drive the intake / exhaust valve at an opening / closing timing suitable for each operation range to improve output. An intake / exhaust valve capable of selectively switching and driving a mechanism or a low-speed cam or a high-speed cam and stopping the supply of intake air and fuel to some cylinders and performing cylinder-stop operation in order to reduce fuel consumption. A variable mechanism and a variable intake / exhaust valve mechanism that stops or suppresses a part of the intake / exhaust valve in order to increase the output by driving the appropriate number of intake / exhaust valves for each operation range. Internal combustion engines are known.

The control means for suppressing the intake / exhaust valve variable mechanism of this type of internal combustion engine sets each operation mode based on various kinds of operation information. In this mode, the opening / closing operation of the intake / exhaust valves of the cylinders is stopped, the fuel supply to the cylinders is stopped, and when the cylinder exits the cylinder mode, the operation of the intake / exhaust valves of the cylinders becomes normal. Then, the fuel supply to the closed cylinder is restarted. In addition, even during all-cylinder operation, the low-speed mode drives the intake and exhaust valves using the low-speed cam to improve the volume efficiency at low speeds, and the high-speed mode uses the high-speed cam to drive the intake and exhaust valves to operate at high speeds. It is configured so that the volumetric efficiency can be improved and the output in each engine operating state can be improved.

By the way, in the internal combustion engine, a fuel cut rotation speed is set to prevent overspeed. For example, in Japanese Patent Application Laid-Open No. 2-161154, the fuel cut rotation speed is set to be relatively low when operated with a cam having a large valve acceleration, and the fuel cut rotation speed is set to be relatively large when operated with a cam having a small valve acceleration. ing.

However, in the above conventional example, since the fuel cut rotation speed is set in consideration of only the valve acceleration,
For example, even in an engine driven by a cam having the same profile and the mass of the valve gear increases, the fuel cut rotation speed is determined only by the acceleration of the cam, and the valve spring does not follow, causing harmful bounce. May occur, causing excessive or frictional or breakage of the part. In order to solve these problems, it is effective to strengthen the valve spring and to reduce the operating mass. However, this causes a new problem that the friction at the sliding contact portion between the cam and the rocker arm increases and the strength of the variable intake / exhaust valve mechanism itself is insufficient.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control device for an engine with a variable intake / exhaust valve mechanism that can prevent damage due to bounce at the time of switching of a valve train without major changes in the mechanism.

DISCLOSURE OF THE INVENTION In order to achieve the above object, the present invention provides a low-speed cam and a high-speed cam provided on a camshaft, a low-speed rocker arm driven by the low-speed cam, and a high-speed rocker arm driven by the high-speed cam, A valve gear that is selectively connected to the low-speed rocker arm or the high-speed rocker arm and has a valve opening / closing arm that opens and closes a valve by the operation of the connected rocker arm; Operating state detecting means for detecting a driving state of the engine; and a low-speed mode in which the intake and exhaust valves of the engine are driven by a low-speed cam, a high-speed mode in which the engine is driven by a high-speed cam, or a low-speed mode based on the output of the operating state detecting means. The operation mode is determined by judging whether the mode has been switched from the high-speed mode immediately after the switching within a certain time. Operating mode information judging means for outputting lock information, and three fuel cut rotation speeds are set in advance in accordance with a connection state between the rocker arm and the valve opening / closing arm in each of the operating modes, and the operation mode information judging means makes a judgment. Fuel cut rotation speed output means for selecting and outputting one of the three fuel cut rotation speeds based on the operation mode information thus obtained; and operating the fuel cut rotation speed output by the fuel cut rotation speed output device in the operation. A fuel injection stop means is provided for outputting a fuel cut command to the fuel supply system of the internal combustion engine when it is determined that the engine rotation speed detected by the state detection means has exceeded.

As described above, according to the present invention, the operating state of the engine is detected by the operating state detecting means, and the output of the operating state detecting means determines whether the mode is the low-speed mode or the high-speed mode, or the mode immediately after switching from the low-speed mode to the high-speed mode within a predetermined time. It is determined whether or not the engine rotation speed detected by the operating state detection means has exceeded the fuel cut rotation speed set for each operation mode. By outputting the fuel cut command, it is possible to prevent the engine valve device from being over-rotated, and in particular, from being damaged due to over-rotation in the mode immediately after the switching of the operation mode within a certain period of time.

In this invention, in particular, the fuel cut rotation speed is determined according to the mass of the lever member and both rocker arms, the spring force of the valve spring or the arm spring, and the acceleration of the cam. The most suitable fuel cut rotation speed can be set at the time of operation, and overspeed can be prevented.

Further, according to the present invention, the fuel cut rotation speed output means also outputs the fuel return rotation speed for stopping other fuel cut commands other than the fuel cut rotation speed, so that the fuel cut can be stopped at the time of the optimal rotation descent.

Here, in particular, by setting the fuel return rotation speed to be lower than the fuel cut rotation speed, hunting can be reliably prevented when the rotation speed increases and when the rotation speed decreases.

Here, in particular, the difference between the fuel return rotation speed and the fuel cut rotation speed is set according to the operation mode,
Hunting prevention characteristics more suitable for the operation mode can be set.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram of a device used in a control device of an engine with a variable intake / exhaust valve mechanism according to one embodiment of the present invention.

FIG. 2 is a partial perspective view of a valve train controlled by the engine control device of FIG.

 FIG. 3 is a sectional view taken along line AA of FIG.

FIG. 4 (a) is an operation explanatory diagram when the valve train in FIG. 1 is in a low speed mode.

FIG. 4 (b) is an operation explanatory diagram when the above device is in a high speed mode.

FIG. 4 (c) is an operation explanatory view when the above device is in the cylinder-stop mode.

 FIG. 5 is a sectional view taken along line CC of FIG.

FIG. 6 is a diagram showing the relationship between the operating mass and the rotational speed applied to the valve spring of the valve train in the engine control device of FIG.

FIG. 7 is an operating range calculation map used by the ECU of the engine control device of FIG.

FIG. 8 is a flowchart of a main routine of the engine control device of FIG.

FIG. 9 is a flowchart of an overspeed determination routine of the engine control device of FIG.

FIG. 10 is a flowchart of an overspeed determination routine of the engine control device of FIG.

FIG. 11 is a flowchart of an injector drive routine of the engine control device of FIG.

BEST MODE FOR CARRYING OUT THE INVENTION The control device for an engine with a variable intake / exhaust valve mechanism shown in FIG. 1 is mounted on an in-line four-cylinder internal combustion engine (hereinafter simply referred to as engine 1).

In the cylinder head 2 of the DOHC type engine 1, an intake path and an exhaust path (not shown) that can communicate with each cylinder are formed, respectively, and each flow path is provided with an intake valve 3 (an example of which is shown in FIG. 2) and the illustration. Each of the intake and exhaust valves is driven by a valve train 4. Here, the valve train 4 includes suction and discharge camshafts 5 and 6 and a rocker shaft section on the cylinder head 2.
Attach 7,8. Each cam shaft 5, 6 has a timing gear 9,
10, both timing gears are connected to a crankshaft (not shown) via a timing belt 11, whereby both camshafts are rotated at half the engine speed. ing. In addition,
The rocker shaft portions 7, 8 are divided for each cylinder.

Here, all the intake and exhaust valves of each cylinder are similarly opened and closed by a valve operating mechanism.
A low-speed rocker arm 14 (mass M _LR ) driven by 12, a high-speed rocker arm 15 (mass M _HR ) driven by a high-speed cam 13, and a substantially T-shaped plan view integrally provided at an intermediate portion of the rocker shaft 7. And a T-shaped lever 50 (mass M _TL ) as a valve opening / closing arm having the arm portion 16 of FIG. Of these, one end of the arm portion 16 is formed in a bifurcated shape, and drives the pair of intake valves 3, 3 to open and close. Low and high rocker arms 14,
Rollers 55, 55 are pivotally supported at one end of 15 and low-speed and high-speed cams 12, 13 are opposed to each other. At the other end, intake / exhaust air forming an essential part of a variable intake / exhaust valve mechanism as shown in FIG. Low and high switching means KL and KH as valve operation switching means are mounted. The low and high switching means KL and KH are provided with pins 17 and 18 slidably supported by the accommodation portion of the rocker shaft portion 7 and springs 19 and 20 respectively.
Hydraulic chambers 21 and 22 that are switched by hydraulic pressures fo1 and fo2 against the elastic forces fs1 and fs2 of each other, switching oil paths 23 and 24 that communicate with each hydraulic chamber, and a hydraulic pump 25 that connects each switching oil path.
And low and high solenoid valves 26 and 27 which are connected to each other in an intermittent manner. The hydraulic pump 25 is connected to an oil tank as shown. The low and high solenoid valves 26 and 27 are three-way valves that supply hydraulic oil to the respective hydraulic chambers 21 and 22 when turned on, and connect the hydraulic chambers to drains when turned off. The low and high solenoid valves 26 and 27 are connected to an engine control unit (ECU) 30 described later.

As is clear from FIGS. 3, 4 and 5, when the low and high solenoid valves 26 and 27 are both off, the elastic forces fs1 and fs2 of the springs 19 and 20 act as shown in FIGS. Pin 17 at locking position L1
The rocker shaft 7 with only the low-speed rocker arm 14 through
The intake valve 3 is driven in a low-speed mode via the arm 16 (see FIG. 4 (a)). At this time, the pin 18 is held in an unlocked position H1, is capable of operation at low speed mode, the operation mass M _L according to the valve spring 53 is small as shown in Figure 6.

On the other hand, when the low and high solenoid valves 26 and 27 are both on, the pressing forces fo1 and fo2 work against each spring force, the pin 17 reaches the unlocking position L2, and the pin 18 reaches the locking position H2 and Only the rocker arm 15 is integrated with the rocker shaft 7, and drives the intake valve 3 in the high-speed mode via the arm 16 (see FIG. 4 (b)). Prior to reaching the high-speed mode, the mode is switched from the low-speed mode to the high-speed mode to enter a mass increasing mode as a mode immediately after the switching within a predetermined time. In this case, pin 1
7 and 18 have both reached the locking positions L1 and H2. At this time, the intake valve 3 is operated according to the profile of the high-speed cam 13, and in particular, the low and high rocker arms 14, 15 and the T-shaped lever 50 are integrated. Operating mass M applied to the valve spring 53
_HA is largest as shown in FIG.

Further, when only the low solenoid valve 26 is on, the pressing force fo1 of the hydraulic chamber 21 is
The elastic force fs2 of the spring 20 acts, the pin 17 retreats to the non-locking position L2, and the T-type lever 50 is held inoperative. At this time, the operating mass _MHB applied to the valve spring 53 is small as shown in FIG. An injector 28 for injecting fuel into an intake port (not shown) of each cylinder is provided in the cylinder head 2 shown in FIG.
Each injector receives the fuel whose pressure has been adjusted by the fuel pressure adjusting means 29 from a fuel supply source 40, and controls its injection drive by an engine control unit (ECU) 30.
Done by

The engine control unit (ECU) 30 has a microcomputer as a main part, and performs an operation control process of the engine. In this embodiment, the engine control unit (ECU) 30 particularly has the following functions. That is, the operation mode information determining means determines whether the intake / exhaust valve of the engine is driven by the low-speed cam, the high-speed mode is driven by the high-speed cam, or the switching between the low-speed mode and the high-speed mode within a certain period of time from the output of the operating state detecting means. , And outputs the operation mode information. Furthermore, three fuel cut rotational speeds are set in advance as fuel cut rotational speed output means in accordance with the connection state between each rocker arm and the valve opening / closing arm in each operation mode, and the operation mode information determined by the operation mode information determining means is set as the fuel cut rotational speed. One of the three fuel cut rotational speeds is selected and output based on the selected one. Further, when it is determined that the engine rotation speed detected by the operating state detection means exceeds the fuel cut rotation speed output by the fuel cut rotation speed output means as fuel injection stop means, a fuel cut command is output to the fuel supply system of the internal combustion engine. I do.

In particular, as shown in FIG. 1, the ECU 30 is provided with an engine rotation speed Ne, a throttle opening degree θs as a load, and a unit based on an engine rotation sensor 31, a load sensor 32, a crank angle sensor 33, a water temperature sensor 34, and an atmospheric pressure sensor 35, as shown in FIG. Crank angle signal Δθ
, Water temperature Twt, and atmospheric pressure Pa, respectively.

Here, a control device for an engine with a variable intake / exhaust valve mechanism according to one embodiment of the present invention will be described with reference to a control program shown in FIGS.

The ECU 30 enters the control of the main routine by turning on a main switch (not shown).

Here, first, an initial function set such as a check of each function, an initial value set, and the like is performed. Subsequently, various operation information of the engine is read, and then the process proceeds to step a2. And
An operating range map that calculates the operating range from the engine speed Ne and A / N as load information (an example is shown in FIG. 7)
More fuel cut zone is determined, in the fuel cut area, proceed to step a3, clear the air-fuel ratio feedback FLG,
The fuel cut FLG is set to 1 and the routine returns.

On the other hand, when reaching step a5 as being not in the fuel cut area in step a2, the fuel cut FLG is cleared, and then it is determined whether or not the air-fuel ratio feedback condition is satisfied,
At the time of a transient operation range such as the power operation range or before the completion of the warm-up, in step a7, the air-fuel ratio correction coefficient KMAP according to the current operation information (A / N, Ne) and the warm-up according to the cooling water temperature Tw. The machine increase correction coefficient Ka is calculated from an appropriate warm-up increase correction coefficient calculation map, these values are stored in the address KAF, and the process proceeds to step a10.

If the air-fuel ratio feedback condition is satisfied from step a6, a target air-fuel ratio according to the current operation information (A / N, Ne) is calculated, and a fuel amount correction coefficient KFB that can achieve the air-fuel ratio is calculated. In step a9, The fuel amount correction coefficient KFB is stored in the address KAF, and the process reaches step a10.

Here, other fuel injection pulse width correction coefficients KDT
Also, the correction value TD of the dead time of the fuel injection valve is set according to the operating conditions, and further, each correction coefficient used for calculating the ignition timing θadv is calculated. Here, the correction value is calculated according to the water temperature correction value θwt advanced in accordance with the water temperature decrease, the acceleration retardation −θacc corresponding to the differential value Δθs obtained by differentiating the throttle valve opening θs, and the intake air temperature decrease. There is an intake air temperature correction value θat to be advanced, a knock retardation −θk value in accordance with an increase in the knock signal Kn, and a battery correction value tb in which the energization time is increased in accordance with a decrease in the battery voltage VB is also calculated. move on. In step a11, a dwell angle calculation map (not shown) is used and set so that the dwell angle increases in accordance with the engine rotation speed Ne. After that, other known control is performed, and the process returns.

An interrupt is made for each predetermined crank angle in the middle of the main routine, and the routine enters an overspeed determination routine. This step
When b1 and b2 are reached, here, the operation mode switching condition set according to the current operation information (A / N, Ne) and the cooling water temperature Tw (eg, the relationship between the load information A / N and the rotation speed Ne is a predetermined condition) Or the rotation speed Ne is equal to or higher than a predetermined rotation speed, or the cooling water Tw
May be functioning as an operation mode judging means for judging that a predetermined temperature or more has been established. Alternatively, the on / off information of the first and second solenoid valves 26 and 27 may be fetched to determine whether the current operation mode is low speed, high speed, It may function as an operation mode sensor for determining one of the cylinder rest modes. However, since the latter requires a sensor, the cost is high, and there is a problem that the determination of the change of the operation mode is delayed. After the determination of the current operation mode, the process returns if the current operation mode is the cylinder-stop mode, otherwise proceeds to step b3. In the low-speed mode in step b4, the high-speed rocker arm is supported only by the arm spring 51 having a weaker biasing force than the valve spring, and a harmful bounce is generated at the high-speed rotation. And its hysteresis h1 is set small. In steps b7 and b8, the current rotation speed Ne is measured. If the value exceeds the fuel cut rotation speed Ne1 '(= Ne1 + h1) actually set here, the process reaches step b9, and the FCFLG as a fuel injection stop command is turned on. If the current rotation speed Ne does not fall below the fuel return rotation speed Ne1 (using the reference fuel cut rotation speed), the process returns to step b15. If the current rotation speed Ne falls below this value, the FCFLG is turned off in step b18. And return.

If the predetermined time has not elapsed after the switching condition is satisfied from step b5, the process proceeds to step b6 to perform the mass increasing mode as the mode immediately after switching. Mass increase mode driven by the high-speed cam in step b6 (both pins 17 and 18 are
6, the operating mass M _HA applied to the valve spring 53 is the largest, and its reference fuel cut rotation speed Ne 2 and its hysteresis h 2 are relatively high, as shown in FIG. Set smaller. Step b11,
At b12, the current rotation speed Ne is measured, and if the value exceeds the fuel cut rotation speed Ne2 '(= Ne2 + h2) actually set here, the process reaches step b9, and FC as the fuel injection stop command is issued.
When the FLG is turned on, the process proceeds to step b16 while the speed is lower, and if the current rotation speed Ne does not fall below the fuel return rotation speed Ne2 (using the reference fuel cut rotation speed), the flow returns as it is. Turn off and return.

If a predetermined time has elapsed after the switching condition is satisfied from step b5, the process proceeds to step b10, and when the high speed mode of step b10 (when pin 17 is disengaged L2 and pin 18 is engaged H2) is reached, As shown in FIG. 6, the transition period of the low-high switching has elapsed, and the operating mass applied to the valve spring 53 has been relatively reduced.
3 and its hysteresis h3 are set relatively large. In steps b13 and b14, the current rotation speed Ne is measured, and the value is used as the fuel cut rotation speed Ne3 '(= Ne3) actually set here.
If it exceeds + h3), it reaches step b9, turns on the FCFLG as a fuel injection stop command, and if it falls below it, it proceeds to step b17, where the current rotation speed Ne is the fuel return rotation speed Ne3 (using the reference fuel cut rotation speed) If the value does not fall below), the flow returns as it is. If the value falls below, the FCFLG is turned off in step b18 and the flow returns.

As described above, the low speed mode and the high speed mode are selectively entered here, and the mass increasing mode having the largest operating mass is transiently entered within a certain period of time after switching between these two modes.
At this time, each reference fuel cut rotation speed Ne1, Ne2, Ne3 and each hysteresis h1, h2, h corresponding to the operating mass in each mode
Each fuel cut rotation speed Ne1 ', Ne as a threshold value by adding 3
2 ′, Ne3 ′ are set, and the fuel cut control is performed according to these values, so that an appropriate overspeed prevention process can be performed, and in particular, the reference fuel cut rotation speeds Ne1, Ne2, Ne3 have respective hysteresis h1, h3.
The actual fuel cut rotation speed Ne1 ',
Ne2 'and Ne3' were set, and the fuel return rotation speed at the time of reduction (using the standard fuel cut rotation speed) was set except for each hysteresis h1, h2, and h3. Can be prevented. Moreover, since the values of the hysteresis h1, h2, and h3 are individually set, the switching responsiveness can be ensured particularly during the transition while maintaining the hunting prevention characteristics.

The following formula (1) is available as a method for obtaining the above-described reference fuel cut rotation speeds Ne1, Ne2, and Ne3.

Here, M represents the operating mass, and g represents the gravitational acceleration.

First, calculation method of the fuel cut-off rotation speed Ne1 in the low speed mode, the load applied to the valve spring when the valve lift amount is maximum, which is driven by the low speed cam 12 as a spring load P, T-type lever as the operating mass M _L 50 (Mass M
_TL ), the low-speed rocker arm 14 (mass M _LR ), the mass obtained by adding all the mass of the valve and the mass of the arm spring 51, and the maximum negative acceleration β of the cam is from the cam generated when the lift amount of the low-speed cam 12 is almost maximum. Is the acceleration that is going to separate. From these values and equation (1), the fuel cut rotation speed Ne1 _A that can prevent the bounce of the valve spring in the low speed mode is obtained. The load applied to the arm spring when the lift amount of the high-speed rocker arm driven by the high-speed cam 13 is the maximum as the spring load P, the mass of the high-speed rocker arm 15 (mass M _HR ) as the operating mass, and the maximum negative acceleration β of the cam are This is the acceleration that occurs when the lift amount of the high-speed cam 13 is almost maximum and the rocker arm moves away from the cam. From these values and equation (1), the fuel cut rotation speed Ne1 _B that can prevent the bounce of the arm spring 51 that urges the high-speed rocker arm in the low-speed mode is obtained, and Ne1 _A
And a smaller value compared to Ne1 _B is set as the fuel cut rotation speed Ne1 in the low speed mode.

Next, the calculation method of the fuel cut rotation speed Ne2 in the mass increasing mode is as follows. The spring load P is the load applied to the valve spring when the lift amount of the valve driven by the high-speed cam 13 is the maximum, and the operating mass M _HA is the T-shaped lever. 50 (mass M _TL ), low and high speed rocker arms 14, 15 (mass M _LR , M
_HR ), the mass obtained by adding the mass of the valve and the mass of the arm spring 51, and the maximum negative acceleration β of the cam are accelerations at which the rocker arm moves away from the cam generated when the lift amount of the high-speed cam 13 is almost maximum. From these values and equation (1), the fuel cut rotation speed Ne2 in the mass increase mode is obtained.

Furthermore, method of calculating the fuel cut-off rotation speed Ne3 in the high-speed mode, load lift amount of the valve to be driven by the high speed cam 13 as a spring load P is applied to the valve spring at the maximum, T-type lever as the operating mass M _HB 50 (Mass M _TL ), mass of the high-speed rocker arm 15 (mass M _HR ), mass of the valve and the mass of the arm spring 51, and the maximum negative acceleration β of the cam occur when the lift amount of the high-speed cam 13 is almost maximum. This is the acceleration at which the rocker arm moves away from the cam. From these values and equation (1), the fuel cut rotation speed Ne3 _A that can prevent the bounce of the valve spring in the high-speed mode is obtained. Also, the load applied to the arm spring when the lift amount of the low-speed rocker arm driven by the low-speed cam 12 is the maximum as the spring load P, and the mass of the low-speed rocker arm 14 (mass M _LR ) as the operating mass,
The maximum negative acceleration β of the cam is an acceleration at which the rocker arm moves away from the cam which is generated when the lift amount of the low-speed cam 12 is almost maximum. From these values and equation (1), the fuel cut rotation speed Ne3 _B that can prevent the bounce of the arm spring 51 that biases the high-speed rocker arm in the high-speed mode is obtained.
The smaller value of Ne3 _A and Ne3 _B is set as the fuel cut rotation speed Ne3 in the high-speed mode.

An injector drive routine as shown in FIG. 11 is executed by such an overspeed determination routine and an interruption at a different crank angle.

Here, the engine rotational speed Ne and the target intake air amount A / N calculated in other routines are taken in, and the process proceeds to step c3. Here, the on / off information of the FCFLG processed in step a2 on the main routine side and step b9 on the overspeed determination routine side is fetched, and it is determined whether or not fuel cut is to be performed. Reach Here, the basic fuel pulse width Tf is calculated from the target intake air amount A / N, and then the target fuel pulse width Tf is calculated.
Tinj is the basic fuel pulse width Tf air-fuel ratio correction coefficient KAF, atmospheric temperature and atmospheric pressure correction coefficient KDT, injector operation delay correction value
It is calculated by TD or the like.

When step c6 is reached, ICFLG =
It is determined whether it is 1 or not.
The program proceeds to c8, in which the target fuel pulse width Tinj is set in the driver for driving the injectors 28 of all the cylinders # 1 to # 4.
The target fuel pulse width Tinj is set only in the driver for driving the injectors # 2 and # 3, the cylinders are operated to stop, and the process proceeds to step c9. In step c9, each driver is triggered and returns. As a result, the injectors 28 of only 2 and 3 cylinders are used when the cylinder is closed, and the injectors of 1 to 4 cylinders are used when the cylinder is not closed.
28 performs the injection drive at the predetermined injection timing, and in particular, when the fuel is cut, the fuel cut of all the cylinders can be reliably executed, and the overspeed can be prevented.

In particular, here, the engine 1 has four cylinders, but the present invention can be applied to engines having other numbers of cylinders, and the number of cylinders to be stopped is fixed to two cylinders. Good, and there is no need for a cylinder rest mechanism.

As described above, the present invention determines whether the low-speed mode driven by the low-speed cam is the high-speed mode driven by the high-speed cam, and if the current operation mode set according to the operation information is different from the previous operation mode, When the current engine rotation speed exceeds the allowable fuel cut rotation speed set for each operation mode, fuel cut processing can be performed, and overspeed of the valve train, especially during switching, can be reliably prevented.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02D 41/22 F02D 13/02 F02D 43/00

Claims (5)

(57) [Claims] A low-speed cam and a high-speed cam provided on a cam shaft; a low-speed rocker arm driven by the low-speed cam; a high-speed rocker arm driven by the high-speed cam; and the low-speed rocker arm or the high-speed rocker arm. A valve operating device capable of driving at least one of an intake / exhaust valve of an engine having a valve opening / closing arm that is connected and that opens and closes a valve by the operation of the connected rocker arm; and an operating state that detects a driving state of the engine. Detection means; and a low-speed mode in which the intake and exhaust valves of the engine are driven by a low-speed cam, a high-speed mode driven by a high-speed cam, or switching between low-speed mode and high-speed mode within a predetermined time from the output of the operating state detection means. Operation mode information judgment that outputs the operation mode information by judging whether the mode is immediately after And three fuel cut rotation speeds are set in advance in accordance with the connection state between each rocker arm and the valve opening / closing arm in each of the operation modes, and based on the operation mode information determined by the operation mode information determination means, Fuel cut rotation speed output means for selecting and outputting one of the three fuel cut rotation speeds; and an engine speed detected by the operating state detection means, the fuel cut rotation speed output by the fuel cut rotation speed output means. A control device with a variable intake / exhaust mechanism, comprising: fuel injection stop means for outputting a fuel cut command to the fuel supply system of the internal combustion engine when it is determined that the speed has exceeded. 2. The fuel cut rotation speed is determined by the mass of the low-speed rocker arm, the high-speed rocker arm, and the valve opening / closing arm, the spring force of a valve spring for urging the intake / exhaust valve in the valve closing direction, the low-speed rocker arm and the high-speed rocker arm. 2. The control device for an engine with a variable intake / exhaust valve mechanism according to claim 1, wherein the control value is determined in accordance with a spring force of an arm spring biased in a direction in which the cam comes into contact with the cam and an acceleration of each cam. 3. A variable intake / exhaust valve mechanism according to claim 1, wherein said fuel cut rotation speed output means also outputs a fuel return rotation speed for stopping a fuel cut command from said fuel injection stop means. Engine control unit with 4. The control device for an engine with a variable intake / exhaust valve mechanism according to claim 3, wherein the fuel return rotational speed is lower than the fuel cut rotational speed. 5. The control of an engine with a variable intake / exhaust valve mechanism according to claim 3, wherein a difference between the fuel return rotation speed and the fuel cut rotation speed is set according to the operation mode. apparatus.