JPH09250368A - Method for controlling start of variable valve timing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling the start of a variable timing device by which the carbon biting is prevented and ignition property and charging efficiency are improved when an internal combustion engine is started. SOLUTION: A variable valve timing device 11 changes the opening time of an intake valve and an exhaust valve and a valve timing according to a driving state. A start detecting means 12 detects the start of an internal combustion engine 10. A complete explosion detecting means 13 detects a complete explosion by the change of rotation of a differential value of the number of revolutions of the internal combustion engine 10. At the start of the engine 10, it prevents the carbon biting at the start and improves fire catching nature, charging efficiency and the ease of starting to set the intake valve closing timing of the variable valve timing device 11 at 25 degree CA behind the bottom dead center from the bottom dead center of a piston from the start detected by the start detecting means 12 to the complete explosion detected by the complete explosion detecting means 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a variable valve timing device, and more particularly to a variable valve timing control method at the time of starting.

[0002]

2. Description of the Related Art Conventionally, a variable valve which obtains an optimum engine torque according to an operating condition by varying an overlapping period of each opening period of an intake valve and an exhaust valve according to an operating condition. Timing devices are known.
In addition, by setting the valve timing of the variable valve timing device to the advanced side at the time of starting, that is, to set the intake valve closing timing to the advanced side, the mixture once sucked into the cylinder is prevented from being pushed back to the intake pipe, and charging is performed. A method of improving efficiency is known (for example, the actual development number 59-
175617, JP 58-8134, and JP 60-15904).

[0003]

In the conventional valve timing setting at the time of starting in the internal combustion engine, only the improvement of the filling efficiency is mentioned, and in the internal combustion engine used for a long time, if carbon is deposited in the combustion chamber. However, there is a problem that the carbon deposited at the time of starting is peeled off, the peeled carbon is caught in the intake valve, the filling efficiency is lowered, and the startability is extremely deteriorated. Further, the conventional internal combustion engine does not consider that the air-fuel mixture distribution in the combustion chamber greatly affects the ignitability at the time of start depending on the intake valve closing timing.

The present invention has been made in view of the above problems, and an object thereof is to prevent carbon from being caught and to improve ignition performance by rich in the vicinity of the ignition plug at the time of starting the internal combustion engine. Further, it is an object of the present invention to provide a control method at the time of starting a variable valve timing device capable of performing optimum valve timing setting capable of improving filling efficiency.

[0005]

[Means for Solving the Problems] In order to solve the above problems, the means described in claim 1 can be adopted. According to this means, it is possible to improve the charging efficiency at the time of starting,
Further, the blowback of the air-fuel mixture becomes small, and it becomes difficult for carbon to be caught in the intake valve. Further, even if the carbon is bitten, the amount of biting is small, so that it is easily removed by the valve closing force of the intake valve, so that it is possible to prevent deterioration of the startability due to the biting. Furthermore, according to this means,
In the combustion chamber, which is a weak flow velocity region at the time of starting, the swirl flow and the tumble flow make the vicinity of the plug rich at the compression top dead center, so that the ignitability is improved and good startability can be secured. Then, after the complete explosion, by operating the variable valve timing device with the conventional setting, it is possible to obtain the optimum engine torque according to the operating state.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a starting control method for a variable valve timing device according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating the principle of the present invention. In the figure, a variable valve timing device 11 varies each valve opening period and valve timing of an intake valve and an exhaust valve of an internal combustion engine 10 according to an operating state. The start detection means 12 detects the start from the number of revolutions of the internal combustion engine 10 or the like. The complete explosion detection means 13 detects the complete explosion of the engine from the rotational fluctuation which is the differential value of the rotational speed of the internal combustion engine 10. For example, when the rotation speed from the compression top dead center of each cylinder until the flank angle reaches a predetermined rotation angle is equal to or higher than a predetermined value, it is determined that an explosion has occurred in that cylinder, and the explosion occurs in a predetermined number or more of cylinders. If yes, it is judged as complete explosion.

FIG. 2 shows a system configuration diagram of the first embodiment of the present invention. In this embodiment, the internal combustion engine 10
As an example applied to a 4-cylinder 4-cycle spark ignition internal combustion engine (engine), FIG. 2 shows a structural cross-sectional view of an arbitrary cylinder. Each part of this internal combustion engine is controlled by a microcomputer 21 described later. In FIG. 2, an engine block 22 accommodates a piston 23 that reciprocates in the vertical direction, and a combustion chamber 24 includes an intake valve 2
While communicating with the intake manifold 25 via 6, the exhaust manifold 27 communicates with the exhaust manifold 28. An ignition plug 29 is provided in the combustion chamber 24 so that a plug gap protrudes. The upstream side of the intake manifold 25 is connected to the intake pipe 31 through the surge tank 30 in common for the four cylinders. Inside the intake pipe 31, a throttle valve 33 and an air flow meter 32 are provided, respectively. Throttle valve 33
Has a configuration in which the opening is adjusted in conjunction with the accelerator pedal, and the opening is detected by the throttle position sensor 34. An intake air temperature sensor 35 for measuring the intake air temperature is provided downstream of the air flow meter 32.

A bypass passage 36 that bypasses the throttle valve 33 and connects the upstream side and the downstream side of the throttle valve 33 is provided, and the degree of valve opening is controlled by a solenoid in the middle of the bypass passage 36. Idle speed control valve (hereinafter referred to as "ISC
37) is attached. A fuel injection valve 38 injects fuel into the air flow passing through the intake manifold 25 in accordance with an instruction from the microcomputer 21 described later. In addition, an oxygen concentration detection sensor (hereinafter referred to as "O
₂ sensor ”) 39 is the exhaust manifold 2
It is provided so as to partially penetrate 8 and detects the oxygen concentration in the exhaust gas before entering the catalyst device. Reference numeral 40 denotes a water temperature sensor which is provided so as to penetrate the engine block 22 and partially project into the water jacket, and detects the temperature of the engine cooling water. An igniter 41 opens and closes a primary current of an ignition coil (not shown).
Reference numeral 42 denotes a distributor, which is a cylinder discrimination sensor 43 that generates a reference position detection signal for the engine flank shaft.
And a rotation angle sensor 44 that generates an engine speed signal for each 30 ° crank angle (hereinafter referred to as “CA”). Reference numeral 45 is a starter, which is turned on by the ignition key to drive the crankshaft 4 through a gear.
Drive 6 to start. Reference numeral 47 is a hydraulic control solenoid valve, which constitutes the variable valve timing device 11 together with the valve operating mechanism 48. The valve mechanism 48
Has a structure in which the opening / closing timing control of the intake valve 26 and the exhaust valve 27 is switched in accordance with the hydraulic pressure on / off signal from the hydraulic pressure control solenoid valve 47.

As shown in FIG. 3, the microcomputer 21 for controlling the operation of each unit having the above-described structure has a hardware structure. In the figure, the same components as those in FIG. 2 are designated by the same reference numerals, and a duplicate description will be omitted. The same applies to other embodiments described below. In FIG. 3, a microcomputer 21 is a central processing unit (hereinafter referred to as “CPU”) 5
0, a read-only memory (ROM) 51 storing a processing program, and a random access memory used as a work area.
An access memory (RAM) 52, a backup RAM 53 that retains data even after the engine is stopped, an input interface circuit 54, an A / D converter 56 with a multiplexer, an input / output interface circuit 55, and the like, and their constituent elements are: They are connected to each other via a bus 57. The A / D converter 56 is the starter 4
5, starter-on signal, intake air amount signal from air flow meter 32, intake air temperature detection signal from intake air temperature sensor 35, detection signal from throttle position sensor 34, water temperature detection signal from water temperature sensor 40, O ₂ sensor Three
The oxygen concentration detection signals from 9 are sequentially switched and fetched through the input interface circuit 54, and these signals are
Bus 5 after analog / digital conversion by the / D converter 56
7 sequentially. A detection signal from the throttle position sensor 34 and a rotation speed signal corresponding to the engine rotation speed (NE) from the rotation angle sensor 44 are input to the input / output interface circuit 55, and these signals are input via the bus 57. Input to the CPU 50.

Further, the CPU 50 executes each arithmetic processing based on various data inputted from the input / output interface circuit 55 and the A / D converter 56 through the bus 57, and obtains the obtained data on the bus 57 and the input / output. ISCV37, fuel injection valve 3 through the interface circuit 55
8, the igniter 41 and the hydraulic control solenoid valve 45 are appropriately selected and output to control the opening of the ISCV 37 to control the idle speed to the target speed, to control the fuel injection time by the fuel injection valve 38, and to control the igniter. The ignition timing control is performed by 41, and the valve timing of the valve operating mechanism 48 is controlled via the hydraulic control solenoid valve 47.

Next, the valve timing control will be described. FIG. 4 is a characteristic diagram of the variable valve timing device when the internal combustion engine is in the operating state (after starting), in which the vertical axis represents the throttle opening and the horizontal axis represents the engine speed (unit rpm). As shown in FIG. 4, in the low load operating state in which the throttle opening is equal to or less than the predetermined value and in the high operating state I in which the engine speed is equal to or more than the predetermined value N, the exhaust valve 27 is provided as shown in FIG. Valve opening period T27 and intake valve 26 opening period T2
The period θ _{1 in} which 6 overlaps is made small to prevent blow-through of gas in the combustion chamber and suppress the engine torque. Further, in the operating region II in which the throttle opening is greater than or equal to the predetermined value and the engine speed is less than or equal to the predetermined value N in FIG. 4, as shown in FIG.
And the opening period T26 ′ of the intake valve 26 overlap with each other to increase the period θ ₂ (θ ₂ > θ ₁ ) to secure a sufficient intake and exhaust period to improve the charging efficiency and improve the engine torque. ing.

Next, at the time of starting, the microcomputer 21 is used to change the setting of the variable valve timing by using the starting detecting means 12 and the complete explosion detecting means 13. As one embodiment of the changing method, FIG. 6 shows a flowchart showing in detail the start-up time of the variable valve timing device control. First, in step 101, the microcomputer starts up when the ignition key is turned on, and starts control. After starting, RA
A flag ST (described later) for initializing M52 and determining starter on / off at this time is also ST = 0 which is starter off.
(Step 102). Next, in step 103, it is determined whether the starter is on or off. This corresponds to the start detection means 12 of FIG. 1, and proceeds to step 104 when the starter is off and sets ST = 0, and proceeds to step 105 when the starter is on and sets ST = 1. Step 10
4, when ST = 0, the start completion is determined by whether or not the rotation speed NE calculated from the input from the rotation angle sensor 44 is, for example, 400 rpm or more (step 10).
7). When NE> 400 rpm in step 107, it is determined that the start is completed, and the process proceeds to the variable valve timing setting after start according to the engine speed and the throttle opening shown in FIG. 4 (step 108). If NE ≦ 400 in step 107, it is determined that the engine is still starting, and the process returns after initialization (step 102).
On the other hand, when ST = 1 (step 105), the variable valve timing is controlled in the starting control routine (step 106), and the completion of starting is confirmed in step 204 in FIG.

Next, the control routine at the time of starting is shown in FIG.
In this routine, first, the intake valve closing timing is set to be advanced, that is, in the present embodiment, the valve timing is set in step 202 of FIG. 5B (θ ₄ <θ ₃ ). Next, the rotation fluctuation ΔNE, which is the number of rotations per unit time, is calculated for each 30 ° CA from the time required to rotate 30 ° CA, for example (step 203). This calculated ΔNE is a set value (in the present embodiment, 50 rpm /
Whether or not there is a complete explosion is determined by whether or not it is larger than (s) (step 204). This corresponds to the complete explosion detection means 13 in FIG. When ΔNE> 50 in step 204, it is determined that the complete explosion has occurred in the engine, and this routine is ended. When ΔNE ≦ 50, it is determined that the complete explosion has not occurred in the engine, and the process returns to step 203.

In an internal combustion engine that operates as described above
In this embodiment, θ in FIG. _FourIntake valve equivalent to
Set the closing time to the optimum value. Figure 8 shows the intake valve at startup
It shows the relationship between the closing timing and the maximum cylinder pressure. Sucking
The air valve closing timing is θ in FIG. 5 (B)._FourIs equivalent to maximum
The in-cylinder pressure corresponds to the piston bottom dead center when the intake valve is closed.
From 0 ° (BDC) to 30 ° CA after piston bottom dead center
It reaches its maximum at 30 ° CA, and within this period
The filling efficiency is improved.

FIG. 9 shows the relationship between the intake valve closing timing and the starting time of the internal combustion engine in which carbon has accumulated in the combustion chamber. When the intake valve closing timing is later than 30 ° CA after bottom dead center, the air is blown back and carbon is easily trapped, and the start-up time increases sharply. On the other hand, when the intake valve closing timing is earlier than 30 ° CA after bottom dead center, the blowback of the air-fuel mixture becomes small, and it becomes difficult for carbon to be trapped in the intake valve. Further, even if carbon is bitten, the amount of biting is small, so that it is easily removed by the valve closing force of the intake valve. From these, in order to suppress the start-up time of the internal combustion engine in which carbon is accumulated in the combustion chamber within 1 second, the intake valve closing timing is from -20 ° CA to 25 ° CA in FIG. 9, that is, 20 ° before piston bottom dead center. 25 ° after bottom dead center of piston from CA
Must be set to CA.

FIG. 10 shows the relationship between the intake valve closing timing and the air-fuel ratio of the plug portion in the combustion chamber. The air-fuel ratio in FIG. 10 is the air-fuel ratio measured at the compression top dead center. If the intake valve closing timing is advanced from 15 ° CA before bottom dead center (that is, −15 ° CA), the fuel is not sufficiently sucked and the vicinity of the plug becomes lean. When the intake valve closing timing is from 15 ° CA before bottom dead center to 30 ° CA after bottom dead center (that is, in the range of -15 ° to 30 ° CA),
In the combustion chamber, which is a weak flow velocity region at the time of starting, the swirl flow and the tumble flow make the vicinity of the plug rich at the compression top dead center and improve the ignitability. 3 after bottom dead center for closing intake valve
If it is delayed from 0 ° CA, rich fuel is unevenly distributed on the intake valve side due to blowback into the intake pipe, and the intake valve closing timing around the plug is from 15 ° CA before bottom dead center to 30 ° CA after bottom dead center. And become lean. As described above, in this embodiment, the intake valve closing timing (θ _{4 in} FIG. 5B) at the time of starting is set to the valve timing from the piston bottom dead center to 25 ° CA after the piston bottom dead center.

Next, a second embodiment of the present invention will be described. FIG. 11 is a system configuration diagram of the second embodiment of the present invention, and the same components as those in FIG. 2 showing the above-described first embodiment are denoted by the same reference numerals, and redundant description will be omitted. In FIG. 11, the variable valve timing device 11 includes an electric motor 50 and a valve mechanism 48.
The timing is shown in FIG. 12 (A).
It is possible to set at any timing from to FIG. 12 (B). The electric motor 50 sets the valve timing based on a signal output from the microcomputer shown in FIG. 13 (the description of the components having the same reference numerals as in FIG. 3 is omitted). The valve timing device control at the time of starting is the same as the flowchart shown in FIG. FIG. 14 shows details of the startup control routine similar to that of FIG. 7 of the present embodiment.
In FIG. 14, components having the same reference numerals as those in FIG. 7 have similar operations, and description thereof will be omitted. The valve timing at the time of starting is set to FIG. 12C (θ ₈ <θ ₁₀ <θ ₇ ), and the control is performed in step 205 of FIG. 14. In the present embodiment, the intake valve closing timing at the time of starting is shown in FIG.
(C) θ ₁₀ from piston bottom dead center 2 after piston bottom dead center
The valve timing is set to 5 ° CA, and the effect is the same as that of the first embodiment.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is a system configuration diagram of the first embodiment of the present invention.

FIG. 3 is a hardware configuration diagram of the microcomputer in FIG. 2;

FIG. 4 is a characteristic explanatory diagram of the variable valve timing device in the first embodiment.

FIG. 5 is an explanatory diagram of opening timings of intake and exhaust valves by the variable valve timing device according to the first embodiment.

FIG. 6 is a flowchart showing a variable valve timing device control routine at the time of starting in the first embodiment.

FIG. 7 is a flowchart showing a control routine at the time of starting in FIG.

FIG. 8 is a diagram showing the relationship between the intake valve closing timing and the maximum in-cylinder pressure at the time of startup in the first embodiment.

FIG. 9 is a diagram showing an intake valve closing timing and a starting time of an internal combustion engine in which carbon is accumulated in a combustion chamber in the first embodiment.

FIG. 10 is a diagram showing a relationship between an intake valve closing timing at the time of starting and an air-fuel ratio near a combustion chamber plug in the first embodiment.

FIG. 11 is a system configuration diagram of a second embodiment of the present invention.

FIG. 12 is an explanatory diagram of opening timing of intake / exhaust valves by the variable valve timing device according to the second embodiment.

13 is a hardware configuration diagram of the microcomputer in FIG.

FIG. 14 is a flowchart showing a start-up control routine in the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 11 ... Variable valve timing device 12 ... Start detection means 13 ... Complete explosion detection means 26 ... Intake valve 27 ... Exhaust valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location F02N 17/08 F02N 17/08 Z (72) Inventor Hiroshi Shimo 1 Toyota-cho, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (1)

[Claims] Claim: What is claimed is: 1. A variable valve timing device for varying the valve opening period and valve timing of an intake valve and an exhaust valve of an internal combustion engine according to operating conditions, a start detection means for detecting the start of the internal combustion engine, and an internal combustion engine In the control method at the time of start of the variable valve timing device, which has a complete explosion detection means for detecting complete explosion, and sets the valve timing so that the valve timing is on the advance side when it is determined at the time of starting, A method for controlling the start-up of a variable valve timing device, characterized in that the intake valve closing timing during the period until is detected is set to a valve timing from the piston bottom dead center to a crank angle of 25 degrees after the piston bottom dead center.