JPS62165546A - Air-fuel ratio control device for engine - Google Patents

Abstract

PURPOSE:To prevent an output shortage by constituting an air-fuel ratio control means for changing over the ratio in step with two valves within a bypass passage formed bypassing a throttle valve, and keeping the valve for changing over an air-fuel ratio control open when a predetermined high level range is detected. CONSTITUTION:When an engine 1 is running, ECU 22 is inputted with a water temperature signal 'Tw' and a throttle opening signal 'TVtheta'. If 'Tw' is higher than predetermined temperature 'T1' and 'TVtheta' is less than predetermined opening 'theta1', a secondary valve device 18 is made to open and the engine 1 is operated with a lean air-fuel ratio. And when the secondary valve device 18 opens, a primary valve device 19 fitted in series therewith is controlled for the opening and closing thereof interlocked with a throttle valve 5, for keeping constant the ratio of air passing through a bypass passage 17 and the throttle valve 5. Also, when an air-fuel ratip over a predetermined level has been detected from the output of a range sensor 23, the secondary valve device 18 is so controlled as to be kept open independent of an engine operation condition.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects a predetermined operating state of an engine and gradually switches the air-fuel ratio to leaner than the stoichiometric air-fuel ratio without sudden changes in output. The present invention relates to an air-fuel ratio control device for an engine that is capable of improving acceleration performance and the like at high altitudes.

[Prior art]

Mainly to save fuel consumption, an engine air-fuel ratio control device that detects a predetermined operating state of the engine and gradually switches the air-fuel ratio to leaner than the stoichiometric air-fuel ratio has already been disclosed in Japanese Patent Application Laid-Open No. 57-210137. It is generally known from publications such as No.

Normally, conventional engine air-fuel ratio control devices detect operating conditions that do not require much engine output, such as during low rotation and low load, fix the amount of intake air, and supply fuel to this amount of intake air. By reducing the amount, the air-fuel ratio is switched to be leaner than the stoichiometric air-fuel ratio.

However, since the output of an engine is proportional to the amount of fuel supplied, if the fuel is suddenly increased or decreased in order to switch the air-fuel ratio between lean and other regions, sudden fluctuations in output occur, resulting in so-called torque shock and vibration. There is a problem that occurs. Therefore, when an engine employing such a conventional air-fuel ratio control device is installed in a vehicle such as an automobile, a problem arises in that the ride comfort of the vehicle is deteriorated.

In order to change the air-fuel ratio to lean without such sudden output fluctuations, it is possible to gradually change the fuel supply amount to gradually change the air-fuel ratio to lean, but in this case, the exhaust gas This will be disadvantageous when trying to purify the environment. That is, for example, when the air-fuel ratio is gradually changed from the stoichiometric air-fuel ratio (air-fuel ratio 14.7) to a leaner air-fuel ratio of 22, the air-fuel ratio is in the region of about 16 where the amount of nitrogen oxides produced is almost the maximum. As the nitrogen oxides gradually pass through the exhaust gas, the amount of nitrogen oxides produced increases, which is disadvantageous in purifying the exhaust gas. Furthermore, since the air is thin at high altitudes, there is a problem that the output is insufficient, especially when the air-fuel ratio is set to a lean air-fuel ratio.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and is capable of switching the air-fuel ratio without fluctuations in output, preventing insufficient output at high places, and making it possible to reduce exhaust gas. The object of the present invention is to provide an air-fuel ratio control device for an engine that is advantageous in purifying the air-fuel ratio.

[Structure of the invention]

In order to achieve the above object, the air-fuel ratio control device for an engine according to the present invention includes an air-fuel ratio control means that detects a predetermined operating state of the engine and changes the air-fuel ratio stepwise to leaner than the stoichiometric air-fuel ratio. In the air-fuel ratio control device for an engine, the air-fuel ratio control means includes a bypass passage that bypasses a throttle valve, and a first valve device that is provided in the bypass passage and that is opened and closed in conjunction with the throttle valve. A second valve device is provided in the bypass passage in series with the first valve device and opens and closes the bypass passage. The air-fuel ratio is controlled in stages by changing the intake air amount relative to the fuel supply amount without changing the fuel supply amount relative to the intake air amount. At the same time, the altitude detecting means detects the altitude of the engine, and when the altitude detecting means detects that the altitude is above a predetermined altitude, the second valve device is switched regardless of the operating state. The present invention is characterized in that a control means is provided for controlling the valve to be held in an open state, so that when the engine is at a predetermined altitude or higher, the bypass passage can be opened to increase the amount of intake air.

[Embodiment 1] An embodiment of the present invention will be described below based on FIGS. 1 to 5.

An air cleaner 3 is provided at the starting end of the intake passage 2 of the engine 1, and an air flow meter 4 and a throttle valve that sequentially detect the amount of intake air from there toward the end and output an intake air amount signal corresponding to the intake air amount QA. A valve 5, a swirl control valve 6, and a fuel injection device 7 are arranged,
A terminal end of the intake passage 2 is connected to a combustion chamber 9 via an intake valve 8. Further, an exhaust valve 11 is disposed at the starting end of an exhaust path 10 led out from the combustion chamber 9, and in the middle of the exhaust path 10,
An air-fuel ratio sensor 12 that detects gas components in exhaust gas and outputs an air-fuel ratio signal corresponding to the air-fuel ratio, and a power insect medium type exhaust purification device 13 are provided in this order. A spark plug 14 provided in the combustion chamber 9 is connected to an ignition coil 16 via a distributor 15.

The intake passage 2 is further provided with a bypass passage 17 that bypasses the throttle valve 5. This bypass passage 1
7 is provided with a solenoid valve 18 for switching the bypass passage B 17 to close, and a sub-throttle valve 19 arranged in series with this solenoid valve 18. As shown in FIG. 2, this sub-throttle valve 19 is designed so that the ratio of the amount of air passing through the bypass passage 17 and the amount of air passing through the throttle valve 5 is constant when the solenoid valve 18 is open. , common valve stem 2
0 and is interlocked with the throttle valve 5, and is adjusted to open and close in conjunction with the throttle valve 5 by an accelerator operating device (not shown). The throttle valve 5 is provided with a throttle sensor 21 that detects the throttle opening TVθ and outputs a throttle opening signal corresponding to the throttle opening. This throttle sensor 21 also serves as an idling switch that outputs an idling signal when the throttle valve 5 is fully closed.

In addition, the fuel injection IQ is fixed and the solenoid valve 18
The diameter of the bypass passage 17 is set to be 20% of the diameter of the portion of the intake passage 2 where the throttle valve 5 is arranged, so that when the valve is opened, an amount of air can be taken in to ensure an air-fuel ratio of 18 or more for stable idling of the engine. It is set as above. Furthermore, the amount of bypass air passing through the bypass passage 17 may vary due to the opening degree of the sub-throttle valve 19 and manufacturing errors in the bypass passage 17, and this variation may cause the amount of intake air to be extremely low during idling. When the amount of bypass air is small, it may have a large effect on the air-fuel ratio, but in order to reduce the effect on the air-fuel ratio due to variations in the amount of bypass air, the upstream opening of the bypass passage 17 is located as close to the throttle valve as possible. It is placed near 5.

This engine air-fuel ratio control device further includes an engine 1
An altitude sensor 23 for detecting the current altitude of the vehicle is provided, and an electronic control unit (hereinafter referred to as ECU) 22 consisting of, for example, a computer is provided for controlling the operations of the fuel injection device 7 and the solenoid valve 18.

This ECU 22 is connected to the engine 1 from a water temperature sensor (not shown).
It has a water temperature signal input port for inputting a water temperature signal corresponding to the cooling water temperature T, and a throttle opening signal input port for inputting a throttle opening signal from the throttle sensor 21. It is configured such that the operating state of the engine 1 can be determined from the height of L Tw, the magnitude of the throttle opening TVθ, and the presence or absence of an idling signal.

In other words, this ECU 22 maintains the above water temperature T. a water temperature determination unit that determines whether or not the water temperature exceeds a predetermined temperature T1 corresponding to the lowest temperature at which the engine can be operated stably in a lean region, for example, approximately 50°C to 60°C; When MT exceeds the above predetermined temperature T1, throttle opening TV
a throttle opening determination unit that determines whether θ exceeds a predetermined opening θ1 opened to obtain a predetermined output; and when the water temperature T8 is equal to or lower than the predetermined temperature T1;
The water temperature T8 exceeds the predetermined temperature T, and
It has an idling determination section that determines whether or not an idling signal is present when the throttle opening degree TVθ exceeds the above-mentioned predetermined opening degree θ1.

The ECU 22 sets the water temperature T8 to the predetermined temperature T.
an altitude signal input port for inputting an altitude signal corresponding to the altitude HA of the engine 1 from the altitude sensor 23 when the altitude H4 exceeds a predetermined reference altitude HI, e.g.
It has an altitude determination section that determines whether or not it is above 1000 meters above sea level. The ECU 22 further operates when the throttle opening determination section determines that the throttle opening TVθ is equal to or less than the predetermined opening θ, or when the idling determination section determines that the idling signal is present. It has a drive section that opens the solenoid valve 18 and closes the solenoid valve 18 when the idling discrimination section determines that there is no input of an idling signal.

Further, the ECU 22 includes an intake air amount signal input boat that inputs an intake air amount signal from the air flow meter 4, and the distributor 15, in order to control the fuel injection amount corresponding to the intake air 1- and the engine rotational speed N.
a rotational speed signal input port for inputting a rotational speed signal corresponding to the engine rotational speed N, and the water temperature T9 is the predetermined temperature T.

, the throttle opening TVθ exceeds the above predetermined opening θ.
, a lean operation map that stores in advance a lean target air-fuel ratio that is read out corresponding to the intake air 'J o A and engine speed N in the following cases, and the water temperatures T and l are below the predetermined temperature T1. or the above water fAT
When w exceeds the predetermined temperature T1 and the throttle opening TVθ exceeds the predetermined opening θ1, the stoichiometric air-fuel ratio corresponding to the intake air amount QA and the engine speed N or an air-fuel ratio close to this is set. The normal operation map stored in advance as the target air-fuel ratio, the water temperature T exceeds the predetermined temperature T1, the throttle opening TVθ is equal to or less than the predetermined opening θ, and the altitude of the engine 1 is A high-altitude operation map that stores in advance a stoichiometric air-fuel ratio at that altitude corresponding to intake air IQA and engine rotation speed N when HA exceeds the predetermined reference altitude H, as a target air-fuel ratio;
Above water temperature T. , throttle opening TVθ and engine 1
Corresponding to the intake air amount QA detected by the air flow meter 4 and the engine rotation speed N detected via the distributor 15 from the lean operation map, normal operation map, or high altitude operation map corresponding to the state of altitude HA, In addition, when driving at high altitudes, these intake air IQA
, a target air-fuel ratio determination unit that reads out a target air-fuel ratio corresponding to the engine rotational speed N and its altitude HA, and determines the target air-fuel ratio; and a fuel injection unit that controls the fuel injection amount of the fuel injection device 7 according to the target air-fuel ratio. and a quantity control section. In addition,
The ECU 22 is also provided with a vehicle speed signal input boat that inputs a vehicle speed signal corresponding to the vehicle speed of a vehicle (not shown) driven by the engine 1, and an air-fuel ratio signal input boat that inputs the air-fuel ratio signal of the air-fuel ratio sensor 12. There is.

In the above configuration, the air-fuel ratio is controlled inside the ECU 22 according to the sequence shown in FIG.

That is, first, the water temperature T is determined from the water temperature sensor.

The water temperature signal corresponding to
1 to the throttle opening (K) is input to the throttle opening determination section via the throttle opening signal input port (
F2). Next, the water temperature determining section determines whether or not the water temperature T exceeds the predetermined temperature T1 (F3). Here, if the water temperature Tw exceeds the predetermined temperature T1, an altitude signal corresponding to the altitude HA of the engine 1 is input from the altitude sensor 23 (F4), and the altitude HA exceeds the reference altitude H, The altitude discriminator determines whether or not (F
5). When the altitude HA of the engine 1 is below the reference altitude H8, the throttle opening determination unit determines whether the throttle opening TVθ exceeds the predetermined opening θ (F6). If the water temperature determination section determines that the water temperature T9 is below the predetermined temperature TI, the engine temperature has not risen sufficiently, and if the air-fuel ratio is set to a lean region higher than the stoichiometric air-fuel ratio, the engine This is the case when the engine rotation becomes unstable during operation. Further, when the water temperature T9 exceeds the predetermined temperature T, and the throttle opening TVθ exceeds the predetermined opening θ1, the throttle valve 5 is closed in order to obtain an output corresponding to the engine load. This is the case when the valve is opened. Therefore, when it is determined that the water temperature T8 is equal to or lower than the predetermined temperature T, or the water temperature T1 is equal to or lower than the predetermined temperature T.

and when the throttle opening degree TVθ exceeds the above-mentioned predetermined opening degree θ, air-fuel ratio control is executed according to the stoichiometric air-fuel ratio or an air-fuel ratio close to it. In these cases, first, the presence or absence of an idling signal is determined in the idling determining section (F7). If it is determined that the idling signal is present, the water temperature is set to T. is below the above-mentioned predetermined temperature T, and it is preferable to supply a large amount of air and fuel in order to improve the stability of idling operation and shorten the warm-up time. Therefore, in this case, the solenoid valve 18 is opened via the drive section (F8). If the idling determination unit determines that there is no idling signal, it means that the throttle valve 5 is opened to obtain an output corresponding to the load of the engine 1, and the stoichiometric air-fuel ratio is Alternatively, it is necessary to execute air-fuel ratio control at an air-fuel ratio close to this. Therefore, in this case, the solenoid valve 18 is closed via the drive section in order to execute the air-fuel ratio control using the normal throttle valve 5 (F9).

In these cases, after executing the opening/closing control (F8 or F9) of the solenoid valve 18, an intake air amount signal is inputted from the air flow make 4 through the intake air amount signal input port. A rotation speed signal corresponding to the engine rotation speed N is inputted from F10 through the rotation speed signal input port, and the target air-fuel ratio corresponding to the intake air amount QA and the engine rotation speed N is determined from the F10 normal operation map in the target air-fuel ratio determination section. determined (Fil),
The fuel injection amount injected from the fuel injection device 7 is controlled by the fuel amount control section according to this target air-fuel ratio (F1
2). The water temperature QA exceeds the predetermined temperature T1,
If it is determined that the altitude HA of the engine 1 is below the reference altitude H2 and the throttle opening TVθ is below the predetermined opening θ1 (F3 to F6), the engine temperature has risen sufficiently. The engine is able to operate stably at low altitudes with a warm, lean air-fuel ratio, and when the engine load is light, the air-fuel ratio is leaner than the stoichiometric air-fuel ratio to save fuel consumption. This is a case where driving is permitted. Therefore, in this case, the solenoid valve 18 is opened via the drive section (F1a), and a large amount of intake air is drawn into the combustion chamber 9 through the intake passage 2 and the bypass passage 17. Then, an intake air amount signal is inputted from the air flow meter 4 through the intake air amount signal (manual input) port, and a rotational speed signal corresponding to the engine rotational speed N is inputted from the distributor 15 through the rotational speed signal input port. (F1a). On the other hand, if the altitude determination section determines that the altitude HA of engine 1 exceeds the reference altitude H, the E CTJ
After the flag bit flag of the data processed in 22 is set (F15), the solenoid valve 18 is opened to increase the amount of intake air (F1a).

After this, the intake air ff1 (;q-) is inputted from the air flow meter 4 through the signal input port, and the rotational speed corresponding to the engine rotational speed N is inputted from the distributor 15 through the rotational speed signal input port. Input a signal (F1a).

The water temperature QA exceeds the predetermined temperature T, and the altitude H0 of the engine 1 is less than or equal to the reference altitude H1,
and when the throttle opening degree TVθ is less than or equal to the predetermined angle θ1, or when the water temperature QA exceeds the predetermined temperature T, and the altitude HA of the engine 1 exceeds the reference altitude H1. After opening the solenoid valve 18 (F1a), it is determined whether the flag is present or not, so that the water temperature QA exceeds the predetermined temperature T1, and the altitude HA of the engine 1 meets the above standard. It is determined whether the altitude exceeds H1 (F16);
If the flag is not set at this stage, the target air-fuel ratio is determined based on the lean operation map and the intake air amount QA and the engine speed N.
7), the fuel injection amount is controlled according to this target air-fuel ratio (F12). If the above flag is set, the target air-fuel ratio is determined based on the stoichiometric air-fuel ratio at that altitude HA based on the above-mentioned altitude operation map (F1a), and the fuel injection amount is determined according to this target air-fuel ratio. controlled (F12). After finally lowering the flag (F19), the process returns to the beginning of the sequence. In this way, when the altitude HA of the engine 1 exceeds the reference altitude H1, the bypass passage 17 is opened to suck in a sufficient amount of air, thereby preventing a decrease in output. Furthermore, since the air-fuel ratio is brought to the stoichiometric air-fuel ratio at that altitude at the same time as the bypass passage is opened, a decrease in output at high altitudes can be more reliably prevented.

Now, assuming that the water temperature T8 exceeds the predetermined temperature T1, for example, as shown in FIG. For example, if the throttle opening is changed uniformly up to the range, as shown in FIG.
The solenoid valve 18 is opened while θ is less than the predetermined opening θ1, and when the throttle opening TVθ exceeds the predetermined opening θ1, the solenoid valve 18 is closed, and the intake air JtQA is as shown in FIG. As shown in (C) and FIG. 5, the intake air IQ corresponding to a lean air-fuel ratio rapidly decreases to the intake air 〒Q2 corresponding to the stoichiometric air-fuel ratio. The change in fuel injection lQr when this air-fuel ratio region is switched is zero as shown in FIG. 4 (D), and when the air-fuel ratio is switched, fuel injection NQt is changed to fuel injection N p + corresponding to a lean air-fuel ratio Unlike the conventional system in which the fuel injection amount is increased from P2 to the stoichiometric air-fuel ratio, the output of the engine 1 does not change. Further, since the air-fuel ratio is changed so as to instantaneously pass through an air-fuel ratio region in which a relatively large amount of nitrogen oxides are generated, less nitrogen oxides are generated, which is advantageous in purifying the exhaust gas. Further, the throttle valve 5 and the sub-throttle valve 19 are connected to the bypass passage 17 when the solenoid valve 18 is open.
Since the ratio of the amount of air passing through the throttle valve 5 to the amount of air passing through the throttle valve 5 remains constant,
The air-fuel ratio can be controlled easily and accurately in the same way as controlling the air-fuel ratio using a single throttle valve 5 during lean operation.

The throttle opening degree TVθ is set to the above-mentioned predetermined opening degree θ.

When changing from a region exceeding θ1 to a region below the predetermined opening θ1, conversely, the intake air amount Q2 corresponding to the stoichiometric air-fuel ratio suddenly increases to the intake air amount Q1 corresponding to a lean air-fuel ratio, but the same is true. Since there is no change in the fuel injection amount Q, there is no output fluctuation and less nitrogen oxides are generated.

In each of the embodiments described above, during warm-up of the engine 1, the solenoid valve 18 is opened to increase the amount of intake air and correspondingly increase the amount of fuel supplied.
Although it is configured to increase the idling speed and shorten the warm-up time, during warm-up operation, the opening degrees of the throttle valve 5 and sub-throttle valve 19 are small, and the amount of intake air tends to be small. It is preferable to form a notch in the sub-throttle valve 19 to further increase the amount of intake air and, correspondingly, further increase the amount of fuel supplied, further increasing the idling speed and shortening the warm-up time.

Also, during deceleration, an idling signal is input to the ECU 22, and a deceleration determination section uses this idling signal and rotational speed signal as parameters to determine whether or not deceleration is in progress, and determines whether or not it is within a predetermined time after the start of deceleration. It is advantageous to provide a deceleration time determination section in the ECU 22 to close the solenoid valve 18 when it is determined that the vehicle is decelerating after the predetermined time has elapsed, thereby enhancing the braking effect of the engine 1.

Furthermore, when the solenoid valve 18 is locked in the closed state for some reason, this locked state is detected,
It is advantageous to configure the ECU 22 to change the fuel supply amount to switch the air-fuel ratio range between the lean range and other ranges.

It is also advantageous to configure the ECU 22 to forcibly stop the fuel supply in order to prevent the engine from locking up when the solenoid valve 18 is locked in the open state for some reason.

The present invention is applicable not only to fuel injection engines but also to engines with a carburetor, and in fuel injection engines, an existing air valve is used to increase the amount of bypass air.
It is also possible to change the air-fuel ratio to lean. Furthermore, it is also possible to perform idle rotation speed control by duty-controlling the solenoid valve 18.

〔Effect of the invention〕

As described above, the engine air-fuel ratio control device of the present invention is provided with a bypass passage that bypasses the throttle valve, and by opening and closing this bypass passage with the second valve device, it is possible to change the fuel supply amount relative to the intake air amount. Since it is configured to switch the air-fuel ratio by changing the intake air amount relative to the fuel supply amount without changing the air-fuel ratio, it is possible to eliminate output fluctuations caused by changes in the air-fuel ratio, and to reduce torque shock and so-called torque shock when changing the air-fuel ratio. Can prevent vibration. Further, when switching the air-fuel ratio, the air-fuel ratio region where a large amount of nitrogen oxides are generated is instantaneously passed through, so the amount of nitrogen oxides generated is small, which is advantageous in purifying exhaust gas. Furthermore, when the altitude of the engine is higher than a predetermined reference altitude, the second valve device is held open regardless of the operating state, so the output is reduced, especially when operating with a lean air-fuel ratio. Shortages can be prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing an embodiment of the present invention;
Figure 2 is a longitudinal sectional view of the intake passage and bypass passage, Figure 3 is a flow diagram of the control sequence executed within the ECU, and Figure 4 (A) is a time chart showing the opening and closing operations of the throttle valve over time. The chart, FIG. 4(B) is a time chart showing over time the opening/closing operation of a solenoid valve that opens and closes in response to the opening/closing operation of the throttle valve, and FIG. 4(C) corresponds to the opening/closing operation of the throttle valve. FIG. 4(D) is a time chart showing how the amount of fuel injection changes over time in response to the opening/closing operation of the throttle valve; FIG. 5 is a fuel supply amount-air amount-engine output relationship diagram showing the relationship between the air amount, fuel supply amount, and engine output when changing the air-fuel ratio range. In the figure, 1 is an engine, 5 is a throttle valve, 17 is a bypass passage, 18 is a knob device (solenoid valve), 22 is a control means (electronic control unit, ECLI), and 23 is an altitude detection means ( altitude sensor). Figure 2 Figure 3

Claims (1)

[Claims] 1. An engine air-fuel ratio control device comprising air-fuel ratio control means for detecting a predetermined operating state of the engine and switching the air-fuel ratio stepwise to a leaner air-fuel ratio than the stoichiometric air-fuel ratio, wherein the air-fuel ratio control means includes a throttle control means. a bypass passage that bypasses the valve; a first valve device that is provided in the bypass passage and is opened and closed in conjunction with the throttle valve; and a first valve device that is provided in the bypass passage in series with the first valve device that controls the bypass passage. a second valve device that switches to open and close; and a second valve control that controls the second valve device to open in the predetermined operating state in which the air-fuel ratio is leaner than the stoichiometric air-fuel ratio and close in other operating states. an altitude detecting means for detecting the altitude of the engine; and when the altitude detecting means detects that the altitude is above a predetermined altitude, the second valve device is opened regardless of the operating state. 1. An air-fuel ratio control device for an engine, comprising a control means for controlling the air-fuel ratio to maintain the same.