JPH0343610A - How to control the engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A.11 Objective of the Invention (Field of Industrial Application) The present invention relates to an engine control method in which valve operating characteristics are variable.

Note that switching the valve operating characteristics refers to switching at least one of the opening/closing timing, opening period, and valve lift amount of the intake valve or exhaust valve, and at least one of the plurality of intake valves or exhaust valves in one cylinder. It also includes reducing the open period of two valves to substantially zero and switching them to a closed state.

(Prior art) An engine in which the valve operating characteristics of both or one of the intake valve and exhaust valve can be freely switched between a low-speed valve operating characteristic suitable for a low-speed range and a high-speed valve operating characteristic suitable for a high-speed range. is disclosed in Japanese Patent Publication No. 49-33289, but in this one, the low-speed valve operation characteristic is changed in the region where the engine speed is below a predetermined value and the intake negative pressure is below a predetermined value (vacuum side). In other areas, it switches to high-speed valve operation characteristics.

Furthermore, in the valve operating characteristic switching control method proposed in Japanese Patent Application No. 83-192239, the output torque when the engine uses the low-speed valve operating characteristic and the output torque when the high-speed valve operating characteristic is used are different. The valve operating characteristics are switched at points that substantially match.

Note that the state in which valve operating characteristics are used refers to a state in which all valves of the engine are operating with valve operating characteristics suitable for the same rotation range.

(Problem M to be Solved by the Invention) When the above-mentioned switching method is used, there is a problem of shock accompanying fluctuations in engine torque at the time of switching, as described below.

First, it is due to hysteresis to stabilize the switching operation. Generally, in order to prevent frequent switching operations, the switching point from one valve operating characteristic usage state to the other is set to the point where the engine output torque in both valve operating characteristics usage states coincide, and vice versa. That is, the switching point from the other to the one is set to be shifted from the torque matching point by providing hysteresis. Then, at the switching point from the other to the one, there is a difference in the output torque of the engine when both pulp operating characteristics are used, so that a sudden torque fluctuation occurs at the time of switching.

Further, when the usage state of the valve operating characteristic is forcibly switched by manual operation or the like, there is often a torque difference at this switching point, and torque fluctuations also occur here.

Furthermore, when selecting a driving mode emphasizing fuel efficiency, the valve operation characteristic usage state is switched at the intersection of the equal fuel consumption curves to optimize for low fuel consumption, but the torques do not match at this intersection, and as a result, Torque fluctuations often occur.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to propose an engine control method that can reduce the shock when changing the operating state of a valve operating characteristic.

8. Structure of the Invention (Means for Solving the Problems) In order to solve the above-mentioned problems, in the present invention, the valve operation characteristics can be freely changed for each cylinder, and the valve operation characteristics of the intake valve in each cylinder can be changed. A plurality of switching modes are set corresponding to the combinations of the valve operating characteristics of the exhaust valve and the valve operating characteristics of the exhaust valve. Valve operating characteristics The output torque of the engine under operating conditions is
The selection order of the switching modes is set so that the output torque of the engine in the other valve operating characteristic usage states is gradually approached through a plurality of switching modes, and according to this selection order, the switching mode is changed from one valve operating characteristic usage state to another. The valve operating characteristics are switched to the usage state.

(Function) If such a control method is used, when the engine switches from a state using one valve operating characteristic to a state using another valve operating characteristic, at this switching point, the engine output when using both valve operating characteristics If there is a difference in torque, the engine shifts from the pre-switching valve operating characteristic usage state to the switching target valve operating characteristic usage state in stages so that the output torque gradually changes. Therefore, smooth switching without sudden torque fluctuations is possible, leading to prevention of shock.

(Embodiments) Hereinafter, preferred embodiments of the control method according to the present invention will be described using the drawings.

FIG. 1 shows the configuration of an engine for using the control method according to the present invention.

In the variable valve timing/lift mechanism VT, cylinders, particularly those for intake valves and those for exhaust valves, are separately disposed on the tenth lever shaft 6 and the twentieth lever shaft 6'.

The oil supplied from the oil pump OP passes through the first linear solenoid valve V1 and the second linear solenoid valve V2 to the oil passage 31 in the 10th lever shaft e and the oil passage 31' in the 20th lever shaft 6', respectively. connection switching means (21a to 21d) for intake valves and connection switching means (21a' to 21d') for exhaust valves.
) is activated.

Here, the oil pressure in the oil passage 31 and the oil passage 31' is controlled by the linear solenoid valves (Vl, V2),
The control oil pressure is set so as to be balanced with the excitation force of the coils 101 and 102 according to the current value of the switching signal VTS from the control unit CU.

Next, the variable valve timing/lift mechanism VT will be explained with reference to FIGS. 2 and 3. A pair of intake valves 1a+1b is provided for each mechanism of the engine E, and these pair of intake valves 1a+1b are provided integrally with a camshaft 2 that is driven at a rotation ratio of 1/2 in synchronization with the rotation of the engine. The first low speed cam 3. The first cam 3' is pivotally supported by a second low-speed cam 3', a high-speed cam 5, and a rocker shaft 6 parallel to the camshaft 2. 2nd and 3rd
It is opened and closed by the action of the 0-tsuka arm 7.8.9.

The camshaft 2 is rotatably disposed above the engine body, and the first low-speed cam 3 is connected to one intake valve 1a.
is provided integrally with the camshaft 2 at a position corresponding to
The second low-speed cam 3' is integrally provided on the camshaft 2 at a position corresponding to the other intake valve 1b. Further, the high-speed cam 5 is integrally provided on the camshaft 2 at a position corresponding to between both intake valves 1a and 1b. Moreover, the first
The second low speed cams 3, 3' have high portions 3a, 3a' corresponding to low speed operation of the engine.

The high-speed cam 5 has a high portion 5a suitable for high-speed operation of the engine.

First to thirtieth lever arms 7 to 9 are respectively pivotally supported on the rocker shaft 6, and the first to thirtieth lever arms 7.8
is extended to a position above each intake valve la, 1b.

Further, a cam slipper 10 that slides on the low-speed cam 3 is provided at the top of the tenth claw arm 7, and a cam slipper 11 that can come into contact with the second low-speed cam 4 is provided on the top of the 20th claw arm 8. Note that each intake valve 1a+1b is biased toward the valve closing direction, that is, upward, by valve springs IEi and 17.

The 30th claw arm 9 is pivotally supported on the rocker shaft 6 between the first and 20th claw arms 7.8. This 30th
The claw arm 9 slightly extends from the mouth and the claw shaft 6 toward both intake valves la and ib, and is provided with a cam slipper on its upper portion that slides into contact with the high-speed cam 5.

As shown in FIG. 3, the first to 30th claw arms 7.8.
9 are in sliding contact with each other, and a connecting means 21 that can switch between a state that allows relative angular displacement thereof and a state that integrally connects each opening and arm 7 to 9 is connected to the first to Second
It is installed at the 0-tsuka arm 7.8°9.

The connection switching means 21 connects the first and 30th hook arms 7.
．． a first piston 22 that is movable between a position in which the third and twentieth hook arms 9.8 are connected and a position in which the connection is released; A stopper 24 that restricts the movement of the piston 23, the first and second pistons 22, 23, and a return spring 25 that urges the stopper 24 to move the first and second pistons 22, 23 toward the disconnection position. Equipped with.

The movement of these first and second pistons 22.23 is performed by hydraulic pressure supplied into the hydraulic chamber 29 through the oil passages 31.degree. 32.30 in response to the operation of the switching valve 91.

Incidentally, such a variable valve timing/lift mechanism is disclosed in detail in, for example, Japanese Patent Laid-Open No. 82-121811.

Next, the variable valve timing
The operation of the lift mechanism VT will be explained.

When engine E is operating at low speed, the switching valve 91 is turned OFF.
As shown in FIG. 3, the communication between the oil passage 31 and the oil pressure source (not shown) is cut off, and oil pressure is not supplied to the oil pressure chamber 29 of the connection switching means 21, and the stopper 24 is closed to the return spring. 25 toward the 30th claw arm 9 side. Each rocker arm 7.8.9 is therefore independently displaceable.

When the connection switching means 21 is in the disconnected state,
Due to the rotational movement of the camshaft 2, the tenth lever arm 7
swings in response to sliding contact with the first low-speed cam 3, and the 20th claw arm 8 swings in response to sliding contact with the second low-speed cam 3'. Therefore, both intake valves la and lb are opened and closed by the first and second low-speed Jl rams 3, 3''.At this time, the 30th lever arm 9 swings due to sliding contact with the high-speed cam 5; The rocking operation is for both intake valves 1a, 1
It has no effect on the operation of b.

In this way, when the engine E is operating at low speed, the 5th A
As shown by a broken line 3 and a dashed-dotted line 3' in the figure, one intake valve 1a opens and closes at a timing and lift amount according to the shape of the first low-speed cam 3, and the other intake valve 1b operates as a second low-speed cam 3. It opens and closes with timing and lift amount depending on the shape of the cam 3'. Therefore, a mixture flow rate suitable for low-speed operation can be obtained, reducing fuel consumption and preventing sparkling, and allows optimum low-speed operation to be performed.

In addition, in order to obtain a mixture flow speed suitable for low-speed operation,
For example, as shown in FIG. 5B, the high part 3a' of the second low-speed cam 3' is lowered to lower the intake valve 1b during low-speed operation.
The opening time and amount of the intake valve 1b may be made extremely small, and furthermore, the above-mentioned high portion 3a' may be set to zero so that the intake valve 1b is not opened at all during low speed operation to create a valve rest state. You can also do it.

When the engine E is operated at high speed, the switching valve 91 is
As shown in FIG. 4, a hydraulic pressure source (not shown) and the oil passage 31 are communicated with each other by a switching valve 91, and the hydraulic pressure is supplied to the hydraulic chamber 29 of the connection switching means 21. As a result, as shown in FIG. 4, the first and second pistons 22 .
23 moves, and the first piston 22 causes the first and third pistons to move.
The 0th lever arm 7.9 is connected, and the 3rd and 20th lever arms 9.8 are connected by the second piston 23.

In this manner, when the first to thirtieth lever arms 7°8.9 are connected to each other by the connection switching means 21,
Since the amount of swing of the 30th claw arm 9 in sliding contact with the high speed cam 5 is the largest, the first and 20th claw arms 7.8 swing together with the 30th claw arm 9. Therefore, during high-speed operation of the engine E, both intake valves 1atlb are moved to the high-speed cam 5, as shown by the solid line 5 in FIG. 5A.
It opens and closes with timing and lift amount depending on the shape of the door. The timing and lift amount in this case are larger than those during low-speed operation, so that intake air suitable for high-speed operation can be obtained, and the engine output can be improved.

In the above-described operation, the opening/closing timing and riff) flt of the intake valves 1a and 1b based on the first and second low-speed cams 3 and 3' are referred to as low-speed valve operating characteristics, and the intake valve 1a based on the high-speed cam 5 , 1b and the lift amount are referred to as high-speed valve operation characteristics. Both valve operating characteristics are used separately for a low-speed operation region and a high-speed operation region, and the relationship between the engine output torque and the engine rotational speed at this time is as shown in FIG. In this figure, the line indicates the characteristic when the low-speed valve operating characteristic is used, and the line H indicates the characteristic when the high-speed valve operating characteristic is used. Normally, switching of the valve operating characteristic is done by following these lines. , H at the intersection C. However, as mentioned above, there are cases where hysteresis is provided between the switching point from the low-speed valve operating characteristic usage state to the high-speed valve operating characteristic usage state and the reverse switching point, or when the switching is forced by manual operation etc. In this case, for example, switching is performed at a point such as point C' where there is a difference in the output torque between the two valve operating characteristics in use, and in this case there is a sudden torque fluctuation.

Next, the switching modes preset in this control method will be explained.

In this engine, as mentioned above, the valve operating characteristics of the intake valve and the valve operating characteristics of the exhaust valve can be selected separately, and they can also be selected separately for each cylinder. For example, when switching the engine from a state in which low-speed valve operating characteristics are used to a state in which high-speed valve operating characteristics are used, a switching mode as shown in FIG. 9 can be set.

In switching mode M1, only the exhaust valve of cylinder #1 has a fast valve operating characteristic, and the other valves remain in a slow valve operating characteristic. In the next switching mode M2, the exhaust valves of cylinder #1 and cylinder #2 have high-speed valve operation characteristics. In switching mode M5, all exhaust valves and the intake valve of cylinder #1 have high-speed valve operation characteristics.

In this way, as the switching mode number increases, the number of valves switched to the high-speed valve operating characteristic increases, and in the final switching mode M7, only the intake valve of cylinder #4 has the low-speed valve operating characteristic.

Next, using the control flow shown in FIG. 7, a control method according to the present invention will be described for a case where the engine is switched from a state in which the low-speed valve operating characteristic is used to a state in which the high-speed valve operating characteristic is used.

First, in step Sl, the engine speed Ne and throttle opening θth are detected, and from these parameters, in step S2, it is determined whether the switching condition is satisfied. When the switching condition is satisfied, the process proceeds to step S3,
Here, the engine output torque is set as shown in Figure 9 so that the engine output torque gradually approaches the engine output torque when the current low-speed valve operating characteristic is used and the engine output torque when the high-speed valve operating characteristic is used, which is the switching target. The selection order n MOD[+ is set by rearranging each switching mode in the order in which it is used. At this time, if the difference in engine output torque in the operating state of the valve operating characteristics before and after switching is relatively small, for example,
Among the switching modes shown in FIG. 9, Ml, M3. M5・
You can set the selection order for every other item, such as...
If the torque difference is relatively large, Ml, ML, M2. M2
．． M3. The selection order may be set such that all switching modes are repeated several times, such as M3....

Next, in step S4, according to the selection order nMODI+ set in step S3, nMooFl=1
switching mode is selected. In step S5, this switching mode selection order n MODI! is the final selection order nL
It is determined whether or not it is MT, and if it is not nLMA, the process advances to step S6. In step S6, in order to set the valve operating characteristics of each valve according to the selected switching mode, a switching signal VTS is sent to the first linear solenoid valve 1 and the second linear solenoid valve V2 shown in FIG. The oil pressure in the passage 31 and the oil passage 31' is changed. In addition, each connection switching means (2) for the intake valve shown in FIG.
1a to 21d) have return springs (25a to 25d) each having a different spring constant. for example,
Let the spring constants of the return springs (2-5a to 25d) be , , , , kd, respectively, and ka < kb
If <ko<kd, as mentioned above, the connection switching means 21
The operation starts when the hydraulic pressure in the hydraulic chamber 29 overcomes the reaction force of the return spring 25, so the operation starting hydraulic pressure of each connection switching means (21a to 21d) is p as shown in FIG. , <Pb <P. becomes Pd. This means that the exhaust valve connection switching means (21a' to 2Ld')
is the same, so let each /(ne constant be, , kb
, , , , is acceptable. Therefore, by appropriately setting the current value of the switching signal VTS sent to the first linear solenoid valve v1 and the second U linear solenoid valve V2, and changing the oil pressure in the oil passage 31 and the oil passage 31', the intake valve, Valve operating characteristics can be set for each exhaust valve as well. For example, in the switching mode M1 in FIG. 9, the oil pressure in the oil passage 31' is set to P in order to bring only the connection switching means 21a' into the connected state as shown in FIG. If switching mode M5, oil path 3
The oil pressure in the oil passage 31' may be set to Pa and the oil pressure in the oil passage 31' to Pd.

In subsequent routines, step 31. After S2,
In step S7, the selection order is nM. Seeing that 08≠O, it is determined that the switching mode is in progress, and the process proceeds to step S4, where the next switching mode in the selection order is selected.

FIG. 10 shows the change in output torque when the engine is switched from a state using the low-speed valve operating characteristic to a state using the high-speed valve operating characteristic. The engine output torque while the switching mode is in progress starts from the output torque Tt in the low-speed valve operating characteristic usage state LVT, and gradually approaches the switching target output torque TH in the high-speed valve operating characteristic usage state HVT as the switching mode progresses. .

Thus, in step S5, the final selection order n
Ended LMT switching mode (n 5oots>
n LMT), the process proceeds to step S8, where a switching signal VTS is outputted to change the valve operating characteristics of all valves to high-speed valve operating characteristics, and the switching operation is ended.

As described above, in this control method, when the engine switches from a state using low-speed valve operating characteristics to a state using high-speed valve operating characteristics, at this switching point, there is a difference in engine output torque between the states using both valve operating characteristics. If there is
The engine gradually transitions from a state using a low speed valve operating characteristic to a state using a high speed valve operating characteristic so that the output torque gradually changes. Therefore, smooth switching without sudden torque fluctuations is possible, and collisions can be prevented.

In addition, in the case of switching from a state in which high-speed valve operating characteristics are used to a state in which low-speed valve operating characteristics are used, the same effect can be obtained by using the switching mode shown in Fig. 9 for this switching, so we will not discuss it here. The explanation will be omitted.

Furthermore, in this embodiment, a linear solenoid valve was used to control the hydraulic pressure of each coupling switching means, but as another method, for example, a solenoid valve may be used to supply and drain hydraulic oil to each coupling switching means. Also good. In this case, the return springs of each connection switching means may have the same spring constant, and the operating oil pressure may also be constant.

(Effect) If the above control method is used, when the engine switches from a state in which one valve operating characteristic is used to a state in which another valve operating characteristic is used, at this switching point, the engine in the state in which both valve operating characteristics are used If there is a difference in output torque,
As the output torque gradually changes, the engine gradually transitions from the state in which the valve operating characteristics are used before switching to the state in which the valve operating characteristics are used as the switching target. Therefore, the engine output torque also changes gradually, allowing smooth switching without sudden torque fluctuations and preventing shock.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of an engine for using the control method according to the present invention; FIGS. 2, 3, and 4 are sectional views showing the variable valve timing/lift mechanism of the engine; Figures 5A and 5B are graphs showing the relationship between valve timing and lift amount of the variable valve timing/lift mechanism, and Figure 8 is a graph showing the relationship between engine output torque and engine speed due to the variable valve timing/lift mechanism. 7 is a graph showing the relationship; FIG. 7 is a control flow of the engine control method; FIG. 8 is a graph conceptually showing the starting oil pressure of the connection switching means of the variable valve timing/lift mechanism; The figure shows a switching mode used in the control method according to the present invention, and FIG. 10 is a graph conceptually showing changes in engine output torque using the above control method. 1a+1b...Intake valve 3.3'...Low speed valve 5...High speed valve 2
1... Connection switching means 25... Return spring

Claims (1)

[Claims] 1) The valve operating characteristics of at least one of the intake valve and the exhaust valve are switchable, and the valves whose valve operating characteristics are switchable can independently select the valve operating characteristics for each valve. In an engine, a plurality of switching modes are set corresponding to the combination of the valve operating characteristic of the intake valve and the valve operating characteristic of the exhaust valve in each cylinder, and the switching mode is changed from a state in which one valve operating characteristic is used to another valve operating characteristic. When the conditions for switching to the usage state are satisfied, the output torque of the engine in the usage state of this one valve operating characteristic becomes the output torque of the engine in the usage state of the other valve operating characteristic via the plurality of switching modes. The selection order of the switching modes is set so that the switching modes gradually approach each other, and the switching mode is switched from the first valve operating characteristic usage state to the other valve operating characteristic usage state according to the set selection order. How to control the engine.