JP2001164946A - Intake air amount control device for variable valve system internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent torque difference generated when a throttle valve is full open. SOLUTION: A target air amount and a target boost coefficient are read out (S1, S2) to calculate an amount corresponding to a change in area of the throttle valve generating a predetermined negative pressure (S3). Simultaneously, the target air amount is read out (S4) to calculate an amount corresponding to a change in area of the throttle valve in a case that the only throttle valve according to the target air amount controls the intake air amount. Then the amount corresponding to the change in area of the throttle valve generating the predetermined negative pressure is compared with the amount corresponding to the change in area of the throttle valve in the case that the only throttle valve according to the target air amount controls the intake air amount, and the amount having larger change in area is selected (S6). The selected amount is converted into an opening of the throttle valve (S7), and is outputted (S8).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake air amount control apparatus for a variable valve type internal combustion engine which generates a negative pressure by a throttle valve and controls an intake air amount by a variable valve mechanism. The present invention relates to a technique for preventing a torque step that occurs when is fully opened.

[0002]

2. Description of the Related Art Conventionally, for the purpose of improving fuel efficiency by reducing pump loss, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 10-37727, a variable valve capable of arbitrarily controlling the opening and closing timing of intake and exhaust valves. Mechanisms are known. In an internal combustion engine equipped with a variable valve mechanism, the intake air amount can be controlled by changing the closing timing of the intake valve, and substantially non-throttle operation can be performed.

On the other hand, in an internal combustion engine, a negative pressure is generated in an intake passage for the treatment of an evaporation gas and a blow-by gas. It is necessary to burn. However, simply controlling the amount of intake air by a variable valve mechanism does not produce sufficient negative pressure, so an internal combustion engine equipped with a throttle valve to generate a negative pressure in the intake passage has been devised. I have.

[0004]

By the way, in order to generate a predetermined negative pressure in the intake passage while controlling the intake air amount by the variable valve operating mechanism, the target air amount determined from the operating state of the engine is required. Accordingly, the opening area of the throttle valve may be linearly increased. However, in order to maximize the potential of the engine, the closing timing of the intake valve is fixed by a variable valve mechanism so that the amount of air in the cylinder is maximized while the negative pressure is kept constant, and the variable valve As in a normal internal combustion engine having no mechanism, it is necessary to control the intake air amount through negative pressure control by a throttle valve and fully open the throttle valve. Therefore, when the throttle valve is fully opened, it is necessary to switch from control for generating a predetermined negative pressure to normal control. Since there is a difference in the opening area of the throttle valve between the two, when switching, the negative pressure in the intake passage suddenly changes and the air mass flow rate in the cylinder changes, which may cause a torque step. There is.

In view of the above-mentioned conventional problems, the present invention continuously changes the opening area of the throttle valve in accordance with the target air amount, regardless of control switching, so that the throttle valve can be fully opened. It is an object of the present invention to provide an intake air amount control device for a variable valve type internal combustion engine which prevents a torque step generated when the engine is driven.

[0006]

Therefore, according to the first aspect of the present invention, as shown in FIG.
Variable valve means C capable of arbitrarily controlling the opening / closing timing of the intake valve, intake air amount control means D controlling the closing timing of the intake valve B by the variable valve means C to control the amount of intake air, and the internal combustion engine A Opening / closing control means F for controlling the opening / closing of a throttle valve E interposed in the intake passage of the engine, wherein the opening / closing control means F comprises: A first opening area calculating means G for calculating an opening area of the throttle valve E at which a predetermined negative pressure is generated in the intake passage based on the target air amount, and an intake air amount using only the throttle valve based on the target air amount. The second opening area calculating means H for calculating the opening area of the throttle valve when performing the control, the opening area calculated by the first opening area calculating means G, and the opening area calculated by the second opening area calculating means H. Compare with the opening area, and The intake air amount control device of the variable valve type internal combustion engine includes a selection means I for selecting the opening method and an opening control means J for controlling the opening of the throttle valve based on the selected opening area. It is characterized by having done.

According to this configuration, the opening area in which a predetermined negative pressure corresponding to the target air amount is generated and the opening area in the case where the intake air amount is controlled only by the throttle valve corresponding to the target air amount. The opening control of the throttle valve is performed based on the opening area being large. That is, even if the characteristics of the opening area with respect to the target air amount are different, the one with the larger opening area is selected, so that the control is always switched at the intersection of both characteristics, and the value of the target air amount in the engine operation region is continuously changed. Becomes

[0008] In the invention described in claim 2, the intake air amount control means corrects the target air amount based on the volume flow ratio at the closing timing of the intake valve, and the corrected target air amount. And intake valve control means for controlling the closing timing of the intake valve based on

Here, the term "volume flow ratio" refers to a ratio with respect to the cylinder maximum volume, and is a state quantity that changes according to the closing timing of the intake valve. According to this configuration, even if the volume flow ratio at the intake valve closing timing changes due to the change in the closing timing of the intake valve, the intake air amount is prevented from changing by performing the correction in consideration of the change.

According to a third aspect of the present invention, the predetermined negative pressure is a constant value. According to a fourth aspect of the present invention, the predetermined negative pressure is set based on an engine body temperature.

[0011]

As described above, according to the first aspect of the present invention, the control is always switched at the intersection of the two characteristics, the opening area with respect to the target air amount becomes a continuous value, and the step at the time of control switching is reduced. Therefore, the occurrence of a torque step can be reliably prevented.

According to the second aspect of the present invention, a change in the air-fuel ratio due to a change in the amount of intake air can be prevented, and the exhaust properties can be further improved. According to the third aspect of the invention, the control for generating the predetermined negative pressure can be simplified.

According to the fourth aspect of the present invention, even when the engine body temperature is low immediately after the start of the engine, the generated negative pressure is increased (for example, -30 mmHg during warm-up and -300 mmHg during cold).
g) The closing timing of the intake valve for introducing the same mass of air into the cylinder can be delayed. For this reason, the valve opening time of the intake valve is lengthened, and the in-cylinder gas flow is improved, so that combustion is stabilized.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the attached drawings. FIG. 2 is a system diagram showing one embodiment of the present invention.

In the cylinder head 2 of the internal combustion engine 1, a spark plug 4 and electromagnetically driven valves 5, 6
(Variable valve operating means) is provided. In each intake port 7,
A fuel injection valve 8 that injects fuel according to the engine operating state is provided. An air flow meter 9 for detecting an amount of intake air Q sucked into the combustion chamber 3 and an electronically controlled throttle valve 10 for generating a negative pressure in the intake port 7 are provided upstream of the intake port 7. . The electronically controlled throttle valve 10 is provided with a throttle sensor 11 for detecting an opening TVO of the throttle valve. Further, the crank pulley 12 is provided with a crank angle sensor 13 that outputs a reference angle signal Ref at a reference crank angle and outputs a unit angle signal Pos for each unit crank angle. In addition, an accelerator pedal sensor 14 for detecting the accelerator opening (accelerator pedal depression amount) APO and a water temperature sensor 15 for detecting a cooling water temperature Tw representing the engine body temperature are provided.

Air flow meter 9, throttle sensor 1
1, crank angle sensor 13, accelerator pedal sensor 14
The output signal of the water temperature sensor 15 is input to a control unit 16 containing a microcomputer. The control unit 16 calculates the engine speed Ne and determines the cylinder based on the signal from the crank angle sensor 13 (determines which cylinder is at the top dead center).
And controls the fuel injection valve 8, the spark plug 4, the electromagnetically driven valves 5, 6, and the electronically controlled throttle valve 10 based on the signals from the sensors.

The control unit 16 includes intake air amount control means, opening / closing control means, first opening area calculation means, second opening area calculation means, selection means, opening degree control means, target air amount correction means, The intake valve control means is realized by software.

Next, the structure of the electromagnetically driven valves 5 and 6 will be described with reference to FIG. A plate-like movable element 22 is attached to a shaft portion 21 of a valve body 20 serving as an intake / exhaust valve. Springs 23 and 24 are provided above and below the mover 22 so that the valve body 20 is elastically supported at the neutral position when not in operation. A valve closing electromagnet 25 and a valve opening electromagnet 26 are disposed above and below the mover 22, respectively.

In order to open the valve body 20, the energization of the valve closing electromagnet 25 is stopped, and then the valve opening electromagnet 26 is turned off.
, The lower surface of the mover 22 is attracted to the valve-opening electromagnet 26 against the urging force of the spring 24, and the valve body 20 is separated from the seat portion. On the other hand, in order to close the valve element 20, the energization of the valve-opening electromagnet 26 is stopped, and then the valve-closing electromagnet 25 is energized so that the upper surface of the movable element 22 is
The valve closing electromagnet 25 is attracted against the urging force of No. 3, and the valve body 20 is seated on the seat portion. By repeating such operations periodically, a function as a valve train of the internal combustion engine is exhibited.

In the internal combustion engine 1, the opening and closing timing of the intake and exhaust valves is controlled by the electromagnetically driven valves 5 and 6, particularly the closing timing (IVC) of the intake valve, for the purpose of improving fuel efficiency by reducing pump loss. By performing (early closing control), the amount of intake air is controlled to perform substantially non-throttle operation. In this case, the electronically controlled throttle valve 10 is used for obtaining a negative pressure in the intake passage under predetermined operating conditions.

Specifically, the opening timing of the intake valve (IVO)
Is a substantially constant timing near the top dead center (TDC) of the exhaust gas, and the closing timing (IVC) of the intake valve is determined according to a target air amount corresponding to a target torque determined based on the accelerator opening APO and the engine speed Ne. Thus, the control is performed in consideration of the throttle opening TVO. On the other hand, the opening timing (EVO) and closing timing (EVC) of the exhaust valve are controlled so as to be the timing having the highest thermal efficiency.

Next, control of the intake air amount of the variable valve type internal combustion engine will be described. As shown in FIG. 4, the control block includes a target air amount calculating unit 30, a throttle calculating unit 40 functioning as an opening / closing control unit, and an EMV (electromagnetic valve) calculating unit 5 functioning as an intake air amount controlling unit.
0. The target air amount calculation unit 30
Based on the accelerator opening APO and the engine speed Ne,
For example, the target air amount is calculated with reference to a map. The throttle calculation unit 40 calculates the opening degree of the electronically controlled throttle valve 10 for achieving both negative pressure generation and full opening performance based on the target air amount. The EMV calculation unit 50 calculates the closing timing of the intake valve by the electromagnetically driven valve 5 that controls the intake air amount based on the target air amount.

The throttle operation unit 40 includes a first opening area operation unit 41, a second opening area operation unit 42,
The configuration includes a selection unit 43 and an opening calculation unit 44. The first opening area calculation unit 41 functions as a first opening area calculation unit, and based on a target boost coefficient and a target air amount described later, for example, changes in the area of the throttle valve that generates a predetermined negative pressure by the following equation. Calculate the equivalent. Here, “the area change equivalent” is calculated by A / NV, where A is the opening area of the throttle valve, N is the engine rotation speed, and V is the cylinder volume, and the engine rotation speed N and the cylinder volume V are calculated. This is a state quantity corresponding to the opening area of the throttle valve when considered.

(Equivalent area change) = (Target air volume) ×
(Target Boost Coefficient) Here, the target boost coefficient refers to a target air amount-area change equivalent characteristic as shown in FIG. 5 for generating a predetermined negative pressure (for example, -50 mmHg) in the intake passage. This is the slope of the straight line. That is, the area change equivalent is calculated as a linear function that simply increases in accordance with the target air amount.

The predetermined negative pressure may take a variable value according to the cooling water temperature Tw. That is, when the cooling water temperature Tw is low, it is considered that the engine is cold immediately after the start of the engine, and a negative pressure is required from the combustion request. Specifically, when introducing the same mass of air into the cylinder, when the negative pressure is developed (in a state where the air density is low), the closing timing of the intake valve is increased in order to lengthen the opening time of the intake valve. This must be slowed down, and as a result, the gas flow time in the cylinder becomes longer and the combustion becomes stable.

The second opening area calculation section 42 functions as a second opening area calculating means, and based on the target air amount, the second opening area calculating section 42 shown in FIG.
With reference to the target air amount-area change equivalent conversion map as shown in (1), an area change equivalent of the throttle valve corresponding to the target air amount is calculated. That is, the second opening area calculation unit 42 calculates the opening of the throttle valve when the intake air amount is controlled only by the throttle valve as in the conventional internal combustion engine.

The selector 43 functions as a selector, and compares the area change calculated by the first opening area calculator 41 with the area change calculated by the second opening area calculator 42. The one with the larger area change is selected. That is,
The signal output from the selection unit 43 is, as shown in FIG.
It is the larger of the area change corresponding to the generation of the predetermined negative pressure and the area change corresponding to the case where the intake air amount is controlled only by the throttle valve. Therefore, control is always switched at the intersection of the two characteristics, and the area change is always a continuous value, so that there is no torque step at the time of control switching.

Based on the area change output from the selector 43, the opening calculation section 44 refers to the area change-to-opening conversion map as shown in FIG. Is calculated.

On the other hand, specifically, the EMV calculation unit 50
The correction operation unit 51 includes an EMV operation limit operation unit 52, a selection unit 53, and an IVC operation unit 54.
The correction calculation unit 51 corrects the target air amount based on a boost correction coefficient and a target air amount described later, for example, by the following equation.

(Correction value) = (target air amount) / (boost correction coefficient) The reason why the EMV calculation unit 50 needs to correct the target air amount is as follows. That is, in an internal combustion engine in which the intake air amount is controlled by the closing timing of the intake valve, the relationship between the volume flow ratio, which is the ratio to the maximum volume of the cylinder, and the area change is as shown in FIG. In this state, the closing timing of the intake valve changes and the volume flow ratio becomes 90%.
%, The characteristic of the volume flow ratio-corresponding to the area change is shown in FIG.
As shown in FIG. 9, the characteristic curve of FIG.

In the calculation of the closing timing of the intake valve, the point at which the cylinder volume becomes maximum in the atmospheric pressure state where the throttle valve is fully opened is considered to be the volume flow ratio = 1. However, even if the same target air amount is given, the density is reduced by the negative pressure, and the air amount actually sucked into the cylinder is reduced. Therefore, the cylinder volume must be increased by the amount reduced by the negative pressure. A coefficient for performing such correction is the above-described boost correction coefficient.

The boost correction coefficient is determined through the following process. Throttle calculator 40 and EMV calculator 5
Since the same target air amount (equivalent to the volume flow rate ratio) is input to 0, as shown in FIG.
When 0.9 is given, the throttle operation unit 40 generates a predetermined negative pressure by calculating the area change of the volume flow ratio 0.9 on the curve that maximizes the volume flow ratio = 1. Must take. On the other hand, the EMV calculation unit 5
In the case of 0, it is necessary to realize the characteristic indicated by the curve that maximizes the volume flow ratio = 1 for the input volume flow ratio = 0.9. Therefore, the value of the volume flow ratio at the intersection of the curve that maximizes the volume flow ratio = 0.9 and the straight line that generates the predetermined negative pressure may be used as the boost correction coefficient. Here, in the case of FIG. 11, assuming that the point at which the predetermined negative pressure on the characteristic curve at which the amount corresponding to the area change becomes the maximum when the volume flow ratio = 1 is 0.9 is 0.9, the volume flow ratio is 0.9. The point at which the predetermined negative pressure is on the characteristic curve where the area change is the largest at the time of is 0.9 × 0.9 = 0.81. Thereafter, the target air amount is divided by the boost correction coefficient, thereby correcting the negative pressure. That is, the target air amount controlled by the electromagnetically driven valves 5 and 6 is corrected based on the cylinder volume at the closing timing of the intake valve without correcting the target air amount by the throttle valve 10. In addition, such correction is
It corresponds to a target air amount correcting means.

The EMV operation limit calculation unit 52 calculates the target air amount at the operation limit of the electromagnetically driven valves 5 and 6, and specifically, based on the engine rotation speed Ne, for example, as shown in FIG.
Referring to the characteristic map shown in FIG. 2, a target air amount serving as an operation limit is calculated.

The selection unit 53 compares the target air amount corrected by the correction calculation unit 51 with the target air amount calculated by the EMV operation limit calculation unit 52, and selects the one with the larger target air amount.

The IVC calculation section 54 calculates the closing timing of the intake valve based on the target air amount selected by the selection section 53. FIG. 13 is a flowchart of the control contents in the throttle calculation unit 40. Since the specific contents are the same as those of the control block described above, only the outline will be described here (the same applies hereinafter).

The target air amount and the target boost coefficient are read (S1, S2), and the first opening area calculator 41 calculates a change in the area of the throttle valve for generating a predetermined negative pressure (S3). In parallel with this, the target air amount is read (S4), and the second opening area calculation unit 42 calculates an amount corresponding to a change in the area of the throttle valve when the intake air amount is controlled only by the throttle valve corresponding to the target air amount. (S5).
Then, by comparing the area change corresponding to the generation of the predetermined negative pressure with the area change corresponding to the case where the intake air amount is controlled only by the throttle valve, the one corresponding to the larger area change is selected (S6). The selected area change equivalent is converted into the opening of the throttle valve by the opening calculating section 44 (S7) and output to the control unit 16 (S8).

In this way, as shown in FIG. 7, the control is always switched at the intersection of the two characteristics, and the area change corresponding to the target air amount becomes a continuous value. In addition, it is possible to reliably prevent the occurrence of a torque step. Therefore, the feeling is improved over the entire operation range of the engine, and a smoother operation is possible.

FIG. 14 is a flowchart of the control contents in the EMV calculation unit 50. The target air amount and the boost correction coefficient are read (S11, S12), and the correction calculation unit 5
The target air amount is corrected according to 1 (S13). And
The target air amount at the operation limit of the electromagnetically driven valve 5 is calculated by the EMV operation limit calculation unit 52 (S14). afterwards,
The corrected target air amount and the target air amount at the operation limit are compared, and the one with the larger target air amount is selected, and the closing timing of the intake valve is calculated by the IVC calculation unit 54 (S15). Output (S16).

In this way, even if the volume flow ratio at the intake valve closing timing changes due to the change of the intake valve closing timing, the total intake air amount can be changed by performing the correction in consideration of the change. Therefore, a change in the air-fuel ratio can be prevented. For this reason, it is possible to prevent the deviation from the ideal air-fuel ratio according to the engine operating state, and it is possible to further improve the exhaust property.

In the present embodiment, the opening / closing timing of the intake valve is changed by the electromagnetically driven valve. However, the closing timing of the intake valve may be changed by a mechanical mechanism. That is, the present invention can be applied if the opening / closing timing of the intake valve can be changed by some means.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a system diagram showing an embodiment of the present invention.

FIG. 3 is a basic structural diagram of an electromagnetically driven valve.

FIG. 4 is a configuration diagram of a control block.

FIG. 5 is a characteristic diagram corresponding to an area change of an electromagnetically driven valve with respect to a target air amount for generating a predetermined negative pressure

FIG. 6 is a characteristic diagram corresponding to an area change of a throttle valve corresponding to a target air amount.

FIG. 7 is an explanatory diagram of an operation in the embodiment.

FIG. 8 is an explanatory diagram of a conversion map of an opening degree corresponding to an area change.

FIG. 9 is a characteristic diagram corresponding to an area change when a volume flow ratio is set to 1;

FIG. 10 is a characteristic diagram corresponding to an area change when a volume flow ratio is set to 0.9.

FIG. 11 is an explanatory diagram of a boost correction coefficient.

FIG. 12 is an explanatory diagram of a map for determining a target air amount at an operation limit of an electromagnetically driven valve.

FIG. 13 is a flowchart of throttle opening control;

FIG. 14 is a flowchart of the closing timing control of the electromagnetically driven valve.

[Explanation of symbols]

 Reference Signs List 1 internal combustion engine 5 electromagnetically driven valve 10 electrically controlled throttle valve 11 throttle sensor 13 crank angle sensor 15 water temperature sensor 16 control unit 30 target air amount calculation unit 40 throttle calculation unit 41 first opening area calculation unit 42 second opening area calculation unit 43 Selection section 44 Opening degree calculation section 50 EMV calculation section 51 Correction calculation section 52 EMV operation limit calculation section 53 Selection section 54 IVC calculation section

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G065 CA13 DA04 DA15 EA08 GA05 GA09 GA10 GA41 GA46 HA22 JA04 JA09 JA11 KA02 3G092 AA01 AA05 AA11 DA07 DC03 EA11

Claims (4)

[Claims] 1. Variable valve operating means for arbitrarily controlling the opening and closing timing of an intake valve of an internal combustion engine, and intake air amount control for controlling the intake air amount by controlling the closing timing of the intake valve by the variable valve operating means. Means for controlling the opening and closing of a throttle valve interposed in an intake passage of the internal combustion engine. An apparatus for controlling the intake air amount of a variable valve type internal combustion engine, comprising: Means for calculating an opening area of the throttle valve at which a predetermined negative pressure is generated in the intake passage based on the target air amount; and an intake air amount using only the throttle valve based on the target air amount. Calculating the opening area of the throttle valve when controlling the throttle valve
Opening area calculating means, and selecting means for comparing the opening area calculated by the first opening area calculating means with the opening area calculated by the second opening area calculating means, and selecting a larger opening area. An opening control means for controlling an opening of a throttle valve based on the selected opening area; and an intake air amount control device for a variable valve type internal combustion engine, comprising: 2. The intake air amount control means includes: a target air amount correction means for correcting a target air amount based on a volume flow ratio at a closing timing of an intake valve; 2. The intake air amount control device for a variable valve type internal combustion engine according to claim 1, further comprising: intake valve control means for controlling a closing timing. 3. The intake air amount control device for a variable valve type internal combustion engine according to claim 1, wherein the predetermined negative pressure is a constant value. 4. The intake air amount control device for a variable valve type internal combustion engine according to claim 1, wherein the predetermined negative pressure is set based on an engine body temperature.