JPS61132742A - Air-fuel ratio controller of engine - Google Patents

Abstract

PURPOSE:To improve fuel consumption and rid toxic constituents in exhaust gas by installing devices to detect revolving speed of an engine, to detect no-load running condition, and to control functioning or stopping of feedback control. CONSTITUTION:Detection signals (ISn) according to an engine speed are supplied from an engine speed sensor 44 to a control unit 50. A crutch sensor 47 and a speed change gear sensor 61 are installed to detect no-load running condition with no engine power being transmitted to the driving wheels of a car. Feedback control for a fuel supply device 22 is stopped when the engine's no-load running condition is detected in the control unit 50. Consequently, this can improve fuel consumption during idling running, and rid toxic constituents in exhaust gas.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention includes an air-fuel ratio feed bank control means for controlling the fuel supply to the engine so that the air-fuel ratio of the air-fuel mixture becomes the stoichiometric air-fuel ratio based on the output signal of the air-fuel ratio sensor. The present invention relates to an air-fuel ratio control device for an engine. (Prior art) In general, in vehicle engines that purify exhaust gas using a three-way catalytic converter, the air-fuel ratio of the air-fuel mixture used for combustion is maintained near the stoichiometric air-fuel ratio. Therefore, for example, Special Publication No. 55-3289
As described in Publication No. 4, an air-fuel ratio sensor (referred to as an exhaust sensor in the above-mentioned publication) such as the 02 sensor is provided in the exhaust passage, and the air-fuel ratio is determined based on the detection signal obtained from the air-fuel ratio sensor. Feedback control is being carried out. When the air-fuel ratio is maintained near the stoichiometric air-fuel ratio by such feedback control, the three-way catalytic converter smoothly oxidizes HC and CO and reduces NOx, promoting purification of exhaust gas. Such air-fuel ratio feedback control usually controls the amount of fuel supplied to the engine based on the output signal of the air-fuel ratio sensor so that the air-fuel ratio of the mixture introduced into the combustion chamber of the engine converges around the stoichiometric air-fuel ratio. This is done through feedback control. In this way, while feedback control of the air-fuel ratio is performed, for example, when a large engine output is required, such as when accelerating a vehicle, the fuel injection amount is increased and the air-fuel ratio is controlled theoretically. It has been considered that the air-fuel ratio is lower than the vicinity of the air-fuel ratio and shifted to the rich side to facilitate increase in engine output. In order to achieve this, when the engine speed reaches a predetermined high speed range where a large engine output is required, feedback control of the air-fuel ratio is stopped and the intake air amount and intake negative pressure are indicated. The engine is operated with the fuel injection amount calculated based on the engine load Σ engine speed, etc. After that, when the engine speed decreases and falls below the above-mentioned predetermined high speed range, the air-fuel ratio is changed again. An air-fuel ratio control device for an engine is known that performs control to start feedback control of the engine. By the way, when the engine of a vehicle is in an idling state, when the accelerator pedal is depressed relatively rapidly for a short period of time to increase the engine speed, so-called racing, the engine speed is For example, as shown in FIG. 3A, where the vertical axis represents the engine speed Ne and the horizontal axis represents the time t, a high engine speed that exceeds a predetermined idling speed ANe to a predetermined high engine speed TNe is shown. The engine speed rapidly rises to the idling speed ANe, and then quickly returns to the idling speed ANe within a short period of time. In such a case, if an air-fuel ratio control device is provided that stops feedback control of the air-fuel ratio when the engine speed reaches a predetermined high speed range, for example, the engine speed Ne Feedback control of the air-fuel ratio is stopped during the period from time 1 to t2, when TNe is in a high rotational speed region exceeding the high rotational speed TNe.At that time, in FIG. 3B, the vertical axis A fuel correction amount rate (hereinafter simply referred to as fuel correction amount rate) P is taken for the basic injection amount of fuel, and time t is taken on the horizontal axis.
The point in time when 1. Until then, in order to maintain the air-fuel ratio of the air-fuel mixture used for combustion near the stoichiometric air-fuel ratio, feed-hack control of the air-fuel ratio was performed using the fuel correction amount rate Px, and at time t1.
In the period from t2 to time t2 when the engine rotational speed Ne, which has further increased thereafter, decreases and becomes high rotational speed TNe again,
The engine speed Ne is within a predetermined high speed range, the feedback control of the air-fuel ratio is stopped and the fuel correction amount rate P is set to O, and furthermore, the feed bank control of the air-fuel ratio is restarted at time tz, and the Oz sensor Based on the output of , an operation is performed to bring the air-fuel ratio of the air-fuel mixture provided for combustion close to the stoichiometric air-fuel ratio. During the period after this time t2, if the vehicle is running and the engine is in a loaded operating state in which its output is transmitted to the drive wheels, the fuel The correction amount rate P changes from 0 to Px relatively quickly.
, and appropriate feedback control of the air-fuel ratio is performed. However, in this case, in the period after time t2,
The engine enters an idling state, which is a no-load operating state in which its output is not transmitted to the drive wheels, so the third
As shown by the solid line in FIG.
At time t3, which is a predetermined time after Px, py is stopped and fixed at py, which is smaller than Px, resulting in the inconvenience that proper feedback control of the air-fuel ratio is no longer performed. The reason for this inconvenience is as follows. When the vehicle is in a running state, the air-fuel ratio control signal (PI multiplication signal Qd in air-fuel ratio feed-back control is
For example, it has a waveform as shown in FIG. 4A, where the period is Td and the slope of the integral part (1st part) is θ. On the other hand, when the vehicle is stopped and the engine is in an idling operating state, the waveform of the PI multiplier signal a in the air-fuel ratio feedback control is as shown by the solid line in FIG. 4B, when the vehicle is in a running state. PI signal Q
It has a period Ta longer than the period Td of d, and has a partial slope θ° smaller than a partial slope θ of the PI signal Qd. Here, the slope θ゛ of the PI multiplied signal a is the PI signal Qd
The reason why the slope θ of a part of the PI signal a is smaller than the slope θ of a part of the PI signal a is because the period Ta of the PI multiplied signal a is longer than the period Td of the PI signal Qd. Similarly, if θ is set as θ, as shown by the dashed line in FIG. This is because it becomes impossible to control the fuel supply amount with high precision. And like this, P

[Since the slope θ' of a part of the signal Qa is smaller than the slope θ of a part of the PI signal Qd, when feedback control of the air-fuel ratio is started while the engine is idling, the fuel correction amount The increase in the ratio P becomes gradual, and normally a predetermined period of time (for example, 20
seconds) have elapsed (when the vehicle is in a running state,
Up to this point, a sufficient value of the fuel correction amount rate P corresponding to the stoichiometric air-fuel ratio can be obtained), and the fluctuation of the fuel correction amount rate P is suppressed and fixed at a constant value. At time t2 shown in FIG. 3B, when feedback control of the air-fuel ratio is started with the engine in an idling state, a predetermined period of time (for example, 20 seconds) starts from time t2.
At a certain point in time t3, a situation occurs in which the increase in the fuel correction amount rate P is stopped. In this way, in an engine equipped with an air-fuel ratio control device that stops feedback control of the air-fuel ratio when the engine speed reaches a predetermined high-speed range, there is a problem in air-fuel ratio control when racing is performed. will occur. (Object of the Invention) In view of the above, the present invention is provided with a feedback control means that performs feedback control of the air-fuel ratio, and in order to effectively increase the output when the rotation speed is in a predetermined high rotation speed range. , when racing is carried out in a no-load operating state in which the engine's output is not transmitted to the drive wheels of the vehicle in which the engine is installed, after which the air-fuel ratio feedback control is stopped. It is an object of the present invention to provide an air-fuel ratio control device for an engine that can eliminate the inconvenience that feedback control of the air-fuel ratio is not performed properly. (Structure of the Invention) The air-fuel ratio control device for an engine according to the present invention adjusts the air-fuel ratio of a mixture to be combusted to the stoichiometric air-fuel ratio based on a signal obtained from an air-fuel ratio sensor provided in connection with a vehicle engine. Feedback control means performs feedbank control on the fuel supply means for supplying fuel to the engine in order to maintain a fuel ratio close to that of the engine; a first detection means detects the rotational speed of the engine; a second detection means for detecting a no-load operating state that is not transmitted to the second detection means; and a control means for controlling the operation of the feedback control means based on the detection results of the first and second detection means. configured. The control means causes the feedback control means to perform feedback control on the fuel supply means regardless of the engine load condition when the engine speed detected by the first detection means is below a predetermined value; When the engine rotational speed detected by the second detection means exceeds a predetermined value, the feed hack control means is caused to perform feedback control on the fuel supply means when the second detection means detects a no-load operating state of the engine. If the no-load operating state of the engine is not detected by the second detection means, the feedbank control means is configured to stop the feedbank control over the fuel supply means. By doing this, even if the engine speed reaches a predetermined high speed range, when the engine is in a no-load operating state, that is, when the engine is racing, the air-fuel ratio It is possible to continuously perform the feedback control of the air-fuel ratio, thereby preventing the occurrence of a situation where the feedback control of the air-fuel ratio is not performed properly after the racing. (Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an example of an engine air-fuel ratio control device according to the present invention together with the main parts of a vehicle engine to which the device is applied. In FIG. 1, an air intake passage 1 is connected through an air cleaner 10.
The flow rate of the intake air introduced into the air flow sensor 4
The detection signal I is detected by 0 and corresponds to the intake air flow rate.
Sa is supplied from the air flow sensor 40 to a control unit 50, which will be described later. The intake air flow rate is regulated by a throttle valve 14 provided in the intake passage 12, and the throttle valve 14 changes its opening degree in response to depression of an accelerator pedal (not shown). There is. The opening degree of the throttle valve 14 is detected by the throttle opening sensor 42, and a detection signal ISv corresponding to the opening degree of the throttle valve 14 is generated.
From the throttle opening sensor 42 to the control unit 5
0. The intake air that has passed through the throttle valve 14 is sent to the engine body 18 via the intake valve 16 for combustion chamber 2.
It leads to 0. A fuel injection valve 22 is provided at a predetermined position in the intake passage 12 . The fuel injection valve 22 is
The injection pulse signal OPj supplied from the control unit 50 causes the fuel to be opened and closed at predetermined timing, and the fuel, which is pumped by a fuel conveyance system (not shown), is transferred to the downstream part of the intake passage 12 near the combustion chamber 20 (intake The engine is injected intermittently toward the throttle valve 1.
A mixture is created with the intake air that has passed through step 4. This air-fuel mixture is then drawn into the combustion chamber 20, ignited by the spark plug 24, and combusted, thereby operating the engine. The rotational speed of the engine that operates in this way is controlled by the distributor 43 that is engaged via a gear with the camshaft 28 that interlocks with the crankshaft of the crank mechanism that converts the reciprocating motion of the piston 26 into rotational motion. A detection signal Isn corresponding to the engine rotation speed is supplied from the engine rotation speed sensor 44 to the control unit 50. Further, a water temperature sensor 45 is attached to the engine body 18, and a detection signal ISt corresponding to the engine cooling water temperature is supplied from the water temperature sensor 45 to the control unit 50. The air-fuel mixture combusted in the combustion chamber 20 is then discharged into the exhaust passage 32 via the exhaust valve 30 as exhaust gas. An 0□ sensor 46 as an air-fuel ratio sensor is installed in the exhaust passage 32, and this O2 sensor 46 detects when the air-fuel ratio of the mixture supplied to the combustion chamber 20 for combustion is near the stoichiometric air-fuel ratio At some point, its output characteristics change. That is, the 0□ sensor 46 detects the oxygen concentration in the exhaust gas and determines whether, for example, the air-fuel ratio of the mixture subjected to combustion is on the lean side or rich side with respect to the stoichiometric air-fuel ratio. A binary detection signal ISo having different voltage levels is generated and supplied to the control unit 1-50. 02 sensor 46 in exhaust passage 32
A three-way catalytic converter 34 for purifying HC, Co, and NOx in the exhaust gas is provided downstream of the exhaust gas. Further, as means for detecting a no-load operating state of the engine in which the engine output is not transmitted to the driving wheels of the vehicle, or a state in which the engine output is transmitted to the driving wheels of the vehicle, the thalassochi sensor 47 and the transmission are used. A sensor 61 is provided. The latch sensor 47 moves the clutch cylinder 4 according to the amount of depression of the clutch pedal 48.
The on/off state of the clutch is detected by the movement of the piston in 9, and the detection signal ISc takes different voltage levels depending on the state where the clutch is connected and the state where the clutch is disengaged, for example. It is supposed to be supplied to the control unit 50. In addition, here,
A state in which the clutch is not fully connected, so-called
A state in which the clutch is partially engaged is also included in a state in which the clutch is engaged. On the other hand, the transmission sensor 61 is provided, for example, in association with a shift lever device 62 for selecting a gear shift position of the transmission, and the shift lever device 62 is provided between a state where the shift lever is at a position for selecting a neutral position of the transmission and a state where the shift lever is at a position for selecting a neutral position of the transmission. Detection signal IS that takes a different voltage level depending on the state at the position where a shift position other than the position is selected
m is supplied to the control unit 50. Further, an ignition switch 38 has one end connected to the positive electrode of the battery 37 and the other end connected to an ignition coil 39 that generates a predetermined high voltage pulse voltage based on the voltage from the battery 37 and supplies it to the distributor 43. It is provided. Note that the high-voltage pulse voltage from the ignition coil 39 supplied to the distributor 43 is further supplied from the distributor 43 to the spark plug 24 . Based on the above configuration, the ignition switch 3
8 is turned on and the engine is operated, the control unit 50 outputs the detection signal ISa from the air flow sensor 40, the detection signal ISv from the throttle opening sensor 42, and the detection signal I from the engine speed sensor 44.
Based on Sn, the detection signal ISt from the water temperature sensor 45, etc., an injection pulse signal OPj for injecting a predetermined amount of fuel from the fuel injection valve 22 is formed and supplied to the fuel injection valve 22. When the engine is in a predetermined operating state, the control unit 50 controls the air-fuel ratio to maintain the air-fuel ratio of the mixture to be combusted near the stoichiometric air-fuel ratio based on the detection signal ISO from the 0□ sensor 46. Performs fuel ratio feedback control. This air-fuel ratio feedback control is performed by the control unit 50 using an injection pulse signal OPj generated based on detection signals ISa, ISv, ISn, ISt, etc.
Further, in accordance with the detection signal ISo from the 0□ sensor 46, for example, the pulse width is controlled to be changed, thereby changing the fuel injection time at the fuel injection valve 22. As a result, the 0□ sensor 46 detects that the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber 20 is near the stoichiometric air-fuel ratio. For example, when the accelerator pedal is depressed while the vehicle is running, and thereby the engine speed Ne increases and reaches a high engine speed range beyond a predetermined high engine speed TNe, the control unit 50 This is the detection signal TS from the engine rotation speed sensor 44.
n is detected, and feedback control of the air-fuel ratio is stopped. That is, the control unit 5o controls the injection pulse signal OPj in accordance with the detection signal ISo from the 02 sensor 46, for example, so as to change its pulse width,
This controls the amount of fuel injected by the fuel injection valve 22 so that the 02 sensor 46 detects that the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber 20 is near the stoichiometric air-fuel ratio. It takes a state of not doing it. As a result, the injection pulse signal OPj obtained from the control unit 5o is no longer controlled by the detection signal ISo from the O2 sensor 46. Under such air-fuel ratio feedback control, even when racing is performed with the engine in a no-load operating state, the engine speed Ne
If the feedback control of the air-fuel ratio is stopped when the engine speed exceeds the high engine speed TNe and reaches the high engine speed range, then after racing, the engine speed Ne will rise again, as described above. When the rotational speed becomes lower than TNe and further reaches the rotational speed of the idling state of the engine, a problem arises in which the resumed feedbank control of the air-fuel ratio is not performed properly.For this reason, in this example, in the control unit 50, the engine The engine rotation speed Ne detected based on the detection signal ISn from the rotation speed sensor 44 is the high rotation speed TN.
When it is below e, feedback control of the air-fuel ratio is performed regardless of the engine load condition, and the high rotational speed T
When exceeding Ne, the detection signal ■Sc from the clutch sensor 47 and the detection signal ISm from the transmission sensor 61
If it is detected that the clutch is engaged, the transmission is in a position other than the neutral position, and the engine output is being transmitted to the vehicle's drive wheels, Feedback control of the air-fuel ratio is stopped, but if the clutch is disengaged or the gear shift position of the transmission is in the neutral position according to the detection signal ISc from the clutch sensor 47 and the detection signal ISm from the transmission sensor 61, If it is detected that the engine output is not being transmitted to the vehicle's drive wheels, that is, the engine is racing, the air-fuel ratio feedback control is continued without stopping. Control is performed. By performing such control, when racing is performed with the engine in a no-load operating state, even if the engine rotation speed Ne exceeds the high rotation speed TNe and reaches a high rotation speed range due to racing, the engine will not be idle. Feedback control of the fuel ratio is continuously performed, and a situation in which the feedback control of the air-fuel ratio is not properly performed in an idling operating state of the engine after racing is avoided. The air-fuel ratio feedback control and the control to stop the air-fuel ratio feedback control as described above are mainly performed by the operation of the microcomputer built in the control unit node 50, but the program executed by the microcomputer is An example of this will be explained with reference to the flowchart in FIG. In this program, after the program starts, it is determined in decision 5 whether or not the clutch is in the disengaged state. This determination is made by determining the amount of depression of the clutch pedal based on the voltage level of the detection signal ISc from the clutch sensor 47, and indicates that the clutch is in the disengaged state.
That is, if it is determined that the engine output is not in a state where it can be transmitted to the drive wheels, the process proceeds to process 56, and the clutch is not in the disengaged state but in the connected state, that is, the engine power can be transmitted to the drive wheels. If it is determined that the condition exists, the process advances to decision 52. In decision 52, it is determined whether the shift position of the transmission is in the neutral position. This judgment is made based on the voltage level of the detection signal ISm from the transmission sensor 61.
This is done by determining whether or not the second shift lever is in the position for selecting the neutral position of the transmission.
If it is determined that the engine is in the neutral position, that is, the engine output is not being transmitted to the drive wheels, the process proceeds to step 56, and the engine is not in the neutral position, that is, the engine output is being transmitted to the drive wheels. If it is determined that there is, the process advances to decision 53. In decision 53, the actual engine speed N
It is determined whether e is greater than the high rotational speed TNe. This determination is made based on a comparison between the engine rotation speed indicated by the detection signal ISn from the engine rotation speed sensor 44 and, for example, the above-mentioned high rotation speed TNe that is preset and stored in the control unit 5o. If it is determined that the engine rotational speed Ne is higher than the high rotational speed TNe, the process proceeds to process 57, in which the air-fuel ratio feed pump control is stopped, and then,
Return to decision 51. Also, in decision 53, the actual engine speed Ne
If it is determined that the rotational speed is less than or equal to the high rotational speed TNe, the process proceeds to process 54. Then, in process 54, conditions are set to perform feedback control of the air-fuel ratio in the range of engine rotation speed Ne below high rotation speed TNe, and in process 5
Proceed to step 5. On the other hand, in a process 56 that proceeds when the engine is determined to be in a no-load operating state by decision 51 or 52, conditions are set to perform feedback control of the air-fuel ratio over the entire range of engine speed Ne. Then, proceed to process 55. Then, in process 55, a state is set in which feedback control of the air-fuel ratio is executed, and then the process returns to decision 51. (Effects of the Invention) As is clear from the above description, according to the air-fuel ratio control device for an engine according to the present invention, a feedback control means for performing feedback control of the air-fuel ratio is provided, and the output thereof is transmitted to the driving wheels of the vehicle. In order to effectively increase output, feedback control of the air-fuel ratio is stopped when the engine's rotation speed is within a predetermined high rotation speed range. When racing is performed in a no-load operating state in which no transmission is carried out, feedback control of the air-fuel ratio is performed continuously, so that feedback control of the air-fuel ratio is properly performed in the idling operating state after racing. It is possible to avoid a situation where the event is not performed. Therefore, it is possible to effectively improve the fuel efficiency and the ability to remove harmful components from exhaust gas when the engine is idling.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an engine air-fuel ratio control device according to the present invention together with an engine to which the device is applied, and FIG. 2 shows a microcomputer used in the control unit of the example shown in FIG. A flowchart showing an example of a program to be executed, FIGS. 3A and B, and FIGS. 4A and B are characteristic diagrams and waveform diagrams used to explain the operation of an engine in which air-fuel ratio feedback control is performed. In the figure, 14 is a throttle valve, 18 is an engine body,
20 is a combustion chamber, 22 is a fuel injection valve, 34 is a three-way catalytic converter, 42 is a throttle opening sensor, 44 is an engine speed sensor, 46 is a 0□ sensor, 47 is a clutch sensor, 50 is a control unit, 61 is a It is a transmission sensor. Figure 2 Figure 3 tltz t t1t2t3t

Claims (1)

[Claims] Fuel supply for supplying fuel to the engine based on a signal obtained from an air-fuel ratio sensor provided in connection with the engine of the vehicle so that the air-fuel ratio of the air-fuel mixture provided for combustion is near the stoichiometric air-fuel ratio. a feedback control means for performing feedback control on the means; a first detection means for detecting the rotational speed of the engine; and a second detection means for detecting a no-load operating state in which the output of the engine is not transmitted to the driving wheels of the vehicle. When the engine rotational speed detected by the detection means and the first detection means is below a predetermined value, the feedback control means is caused to perform feedback control on the fuel supply means regardless of the load condition of the engine, and , when the engine rotational speed detected by the first detection means exceeds a predetermined value, and when the no-load operating state of the engine is detected by the second detection means, the fuel supply to the feedback control means is performed. control means for performing feedback control on the fuel supply means, and causing the feedback control means to stop feedback control on the fuel supply means when the no-load operating state of the engine is not detected by the second detection means; An air-fuel ratio control device for an engine, comprising: