JPS61132743A - Air-fuel ratio controller of engine - Google Patents

Abstract

PURPOSE:To avoid inconveniences caused by an engine's piecemeal torque fluctuations by installing a control system to step feedback control for a fuel supplying device according to conditions of engine load, condition of power transmission to driving wheels, and engine speed. CONSTITUTION:A throttle valve opening sensor 42 detects load of an engine. A crutch sensor 47 and a speed change gear sensor 61 detects a condition of engine power torque's transmission to driving wheels. An engine sensor 44 detects engine speed. A control unit 50 has a controller to stop feedback control for a fuel supplying system 22. Thus, this can avoid inconveniences caused by the engine's piecemeal torque fluctuations occurred with fluctuations of fuel supply quantity.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides an air-fuel ratio sensor that controls fuel supply to an engine based on an output signal of an air-fuel ratio sensor so that the air-fuel ratio of an air-fuel mixture becomes the stoichiometric air-fuel ratio. The present invention relates to an engine air-fuel ratio control device equipped with feedback control means.

(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 by controlling the When such feedback control is performed, the amount of fuel supplied to form the air-fuel mixture introduced into the combustion chamber of the engine is determined to reach the stoichiometric air-fuel ratio. The air-fuel ratio is lean.
It is assumed that the amount increases and decreases alternately between the amount on the side and the amount on the rich side. For this reason, the engine speed changes in response to changes in the fuel supply amount, which causes the air-fuel ratio to shift from the lean side to the over:tjl (rich) side and vice versa. Therefore, under air-fuel ratio feedback control, the engine always produces relatively small and small torque fluctuations.

The fluctuation in the amount of fuel supplied due to such feedback control of the air-fuel ratio is relatively small, and for example, when the engine output is high and the vehicle is running at high speed, When a large amount of fuel is injected, the amount is sufficiently small compared to the amount of fuel contained in the mixture supplied to the combustion chamber of the engine, and therefore, such fluctuations in the amount of fuel supplied Torque fluctuations that occur as the engine speed changes over time are not a separate problem.

However, for example, when the vehicle is running at low speed with the throttle valve fully closed, the required engine output is small and a small amount of fuel is injected into the engine, causing the engine to run at a low speed. The rotational speed is kept low, and the proportion of the variation in fuel supply amount due to air-fuel ratio feedback control to the total amount of fuel contained in the air-fuel mixture supplied to the combustion chamber of the engine increases.

For this reason, the influence of small torque fluctuations that occur with changes in engine speed due to fluctuations in fuel supply due to air-fuel ratio feedback control becomes large, and this affects the power transmission path from the engine to the drive wheels. There is a risk that undesirable vibrations may occur in the vehicle and be transmitted to the vehicle body while the vehicle is running.

(Object of the Invention) In view of the above, the present invention provides that a vehicle driven by the output of an engine equipped with a feedback control means for performing feedback control of the air-fuel ratio is operated under a light load in which the throttle valve is in a fully closed state. When the vehicle is being driven by an engine operating at a low rotation speed, or when the vehicle is traveling at a low speed, the amount of fuel supplied changes due to feedback control of the air-fuel ratio. An object of the present invention is to provide an air-fuel ratio control device for an engine that can avoid inconveniences caused by small engine torque fluctuations that occur.

(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. Feedhack control means for performing feedback 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; first detection means for detecting the engine load; and transmission of the engine output to the drive wheels. A second detection means for detecting the state, a third detection means for detecting the engine speed or the vehicle speed, and a control means for controlling the operation of the feedback control means based on the detection results of each of these detection means. It consists of The control means includes the first. The second and third detection means determine that the vehicle is running at a predetermined low engine speed or vehicle speed with the engine being operated at a light load and its output being transmitted to the drive wheels. When this is detected, the feedback control I for the fuel supply means by the feedback control means is stopped.

By doing this, when the vehicle is being driven by an engine operating at a low rotation speed under a light load where the throttle valve is fully closed, or When the vehicle is running at a low speed, air-fuel ratio feedback control is canceled, thereby eliminating the inconvenience caused by small engine torque fluctuations that occur due to fluctuations in the amount of fuel supplied due to air-fuel ratio feedback control. can.

(Example) Embodiments of the present invention will be described below 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 an 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). The opening degree of the throttle valve 14 is detected by a throttle opening sensor 42 serving as a means for detecting the load state of the engine, and a detection signal ISv corresponding to the opening degree of the throttle valve 14 is sent to the throttle opening sensor 42 to control the engine load state. Unit 50 is supplied.

The intake air that has passed through the throttle valve 14 is guided to the combustion chamber 20 of the engine body 18 via the intake valve 16. A fuel injection valve 22 is located at a predetermined position in the intake passage 12.
has been temporarily set up. The fuel injection pulp 22 is controlled to open and close at a predetermined timing by an injection pulse signal OPj supplied from the control unit 50, and the fuel injection pulp 22 is controlled to open and close at a predetermined timing by an injection pulse signal OPj supplied from the control unit 50. The intake air is injected intermittently toward the downstream part (intake port part) of the engine to create a mixture with the intake air that has passed through the throttle valve 14. 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 02 sensor 46 as an air-fuel ratio sensor is installed in the exhaust passage 32, and this 02 sensor 46 is
When the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber 20 for combustion is near the stoichiometric air-fuel ratio, its output characteristics are said to change. That is, the 02 sensor 46 is
The oxygen concentration in the exhaust gas is detected and, for example, two voltage levels are taken that differ depending on whether the air-fuel ratio of the air-fuel mixture used for combustion is on the lean side or rich side with respect to the stoichiometric air-fuel ratio. A value detection signal ISo is generated and supplied to the control unit 50. On the downstream side of the 0□ sensor 46 in the exhaust passage 32, HC, Co, and N in the exhaust gas are
A three-way catalytic converter 34 is provided to purify Ox.

Furthermore, a clutch sensor 47 and a transmission sensor 61 are provided as means for detecting the state of transmission of engine output torque to the drive wheels. The clutch sensor 47 detects the engaged state of the clutch by the movement of a piston in the clutch cylinder 49 that is displaced according to the amount of depression of the clutch pedal 48, and detects, for example, a state in which the clutch is connected and a state in which the clutch is disengaged. The control unit 50 is supplied with a detection signal ISc that takes different voltage levels depending on the respective states of the control unit 50 and the control unit 50. Note that here, a state in which the clutch is not completely connected, a so-called half-clutch state, is also included in a state in which the clutch is connected. 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 a transmission, and is configured to switch between a state where the shift lever is at a position for selecting a neutral position of the transmission and a shift position other than the neutral position. The control unit 50 is provided with a detection signal (I S m) that takes a different voltage level depending on the state of the selected position.

Furthermore, the control unit 50 has an ignition coil 3 whose one end is connected to the positive electrode of the battery 37 and whose other end generates a predetermined high voltage pulse voltage based on the voltage from the battery 37 and supplies it to the distributor 43.
A detection signal ISi is also supplied from the ignition switch 38 to which 9 is connected, and the control unit 50 can detect that the ignition switch 38 is turned on and the engine is started. , it is possible to detect that the engine is in a subsequent operating state, and that the ignition switch 38 is turned off and the engine is placed in a non-operating state.

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 detects that the engine has been started by the detection signal ISi from the ignition switch 38, and detects the detection signal from the air flow sensor 40 (No. 8 ISa, Detection signal IS from throttle opening sensor 42
V, engine rotational speed Detection signal ISn from rotational speed ke 44
Based on the detection signal ISt from the water temperature sensor 45 and the like, 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. Then, when the engine enters 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 02 sensor 46. performs 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.
is further controlled, for example, to change its pulse width in accordance with the detection signal ISo from the 02 sensor 46, thereby changing the fuel injection time at the fuel injection valve 22. This is done by controlling the fuel injection amount so that the 02 sensor 46 detects that the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber 20 is close to the stoichiometric air-fuel ratio.

When feedback control is performed in this manner, as described above, the amount of fuel injected by the fuel injection valve 22 repeats increases and decreases around the amount at which the air-fuel ratio of the air-fuel mixture becomes the stoichiometric air-fuel ratio. This fluctuation in the fuel injection amount causes small fluctuations in the engine rotational speed, and small fluctuations in the output torque of the engine. At this time, the vehicle, which is driven by the engine's output,
When the engine is operating at a light load, such as when the throttle valve 14 is fully open, and the vehicle is running at a low engine speed in a low engine speed range, a small amount of fuel is supplied to the combustion chamber 20, so the combustion The ratio of fluctuations in fuel injection amount due to air-fuel ratio feedback control to the total amount of fuel supplied to the chamber 20 increases, and as a result, small fluctuations in engine output torque due to fluctuations in fuel injection amount occur. A problem arises that produces undesirable vibrations.

Therefore, in this example, in the control unit 50, the throttle valve 14 is brought into the fully closed state by the detection signal ISV from the throttle opening sensor 42, the detection signal TSc from the clutch sensor 47, and the detection signal Ism from the transmission sensor 61. The clutch is connected and the gear shift position of the transmission is at a position other than the neutral position, and furthermore, the engine rotation speed sensor 44 is connected.
When it is detected that the engine speed is in a predetermined low speed range based on the detection signal ISn from 2. When the vehicle is operating under a light load, such as when the throttle valve 14 is fully closed, the output of the engine, which is operated at a predetermined low rotational speed range, is transmitted to the drive wheels via the clutch and transmission. If it is detected that the vehicle is running at a low speed, the control unit 50 stops feedback control of the air-fuel ratio. That is, the control unit 50 receives the detection signal IS from the 0□ sensor 46.

For example, the pulse width of the injection pulse, signal OPj, is changed according to ! II 2B, thereby controlling the fuel injection amount by the fuel injection valve 22, and 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. In other words, the state is such that no control is performed.

As a result, the injection pulse signal OPj obtained by the control unit 50 is no longer controlled by the detection signal ISo from the 02 sensor 46, and the injection pulse signal OPj obtained by the control unit 50 is no longer controlled by the detection signal ISo from the 02 sensor 46,
The fuel injection according to No. 2 is performed without causing small engine torque fluctuations.

The air-fuel ratio feedback control and the control to stop the air-fuel ratio feedback wI control as described above are mainly performed by the operation of the microcomputer built in the control unit 50. This will be explained with reference to the flowchart in FIG.

In this program, after starting, it is determined in decision 51 whether or not the throttle valve 14 is in a fully closed state. This determination is made based on the detection signal ISv from the throttle opening sensor 42, and if it is determined that the throttle valve 14 is not fully closed, that is, the accelerator pedal is depressed, the process 56 is performed. the throttle valve 14 is fully closed, i.e.
If it is determined that the accelerator pedal is not depressed, the process advances to decision 52. In decision 52, it is determined whether the clutch is in an engaged 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. If it is determined not to be present, the process proceeds to process 56, and if it is determined that the clutch is in the engaged state, that is, the engine output can be transmitted to the drive wheels, the process proceeds to decision 53. Next, in decision 53, it is determined whether the shift position of the transmission is at a position other than the neutral position. This judgment is made using the detection signal IS from the transmission sensor 61.
This is done by determining whether or not the shift lever of the shift lever device 62 is in a position for selecting the neutral position of the transmission based on the voltage level of m. If it is determined that the engine is not in the neutral position, the process proceeds to process 56, and if it is determined that the engine is in a position other than the neutral position, that is, the engine output is being transmitted to the drive wheels, the process proceeds to decision 54. .

In decision 54, the actual engine speed N
It is determined whether or not e is less than or equal to the set rotational speed TNe. The set rotation speed TNe is determined by the low rotation speed range where vibrations due to the small torque fluctuations described above occur when air-fuel ratio feedback control is performed when the vehicle is driven by the original engine output, and It is assumed that the setting is made to define a higher rotation speed range. This judgment is based on the detection signal ISn from the engine rotation speed sensor 44.
This is performed based on a comparison between the engine rotation speed indicated by and, for example, the above-mentioned set rotation speed TNe that is preset and stored in the control unit 50, and if the engine rotation speed Ne is larger than the set rotation speed TNe. If it is determined that there is, the process proceeds to process 56, and if it is determined that the engine rotation speed Ne is equal to or lower than the set rotation speed TNe, the process proceeds to process 55.

When the process 55 is reached through the above-described flow, the vehicle is driven by an engine that operates at a predetermined low engine speed range determined by the set engine speed TNe with the throttle valve 14 fully open. A determination is made that it is in a running state, and therefore process 55
The injection pulse signal OPj is controlled according to the detection signal ISo from the 02 sensor 46, thereby controlling the fuel injection amount by the fuel injection valve 22, and the 02 sensor 4
6, the feedback control of the air-fuel ratio, which detects that the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber 20 is near the stoichiometric air-fuel ratio, is stopped. Then, the process returns to decision 51.

On the other hand, in process 56, the running state of the vehicle at that time is such that even if the air-fuel ratio feedback control is performed, there will be no inconvenience of separate installation, so the air-fuel ratio feedback control is not performed. Continue a and return to decision 51.

Note that the determination in decision 54 in the above-described flow may be made based on the traveling speed of the vehicle, and in this case, when it is determined that the actual traveling speed of the vehicle is less than or equal to a predetermined low vehicle speed. Only the process 55 is assumed to proceed.

Further, in the above embodiment, the throttle opening sensor 42 is used as a means for detecting the load state of the engine, but an intake negative pressure sensor that detects the intake negative pressure downstream of the throttle valve is provided, and this intake negative pressure sensor detects the engine load. Alternatively, the load state of the controller may be detected.

(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 vehicle driven by the output of an engine equipped with a feedback control means that performs feedback control of the air-fuel ratio can be used. , when the vehicle is being driven by an engine running at low rotation speeds under light load conditions such as when the throttle valve is fully closed, or when the vehicle is traveling at low speeds, the air-fuel ratio may change. Since feedback control is stopped, it is possible to avoid inconveniences caused by small engine torque fluctuations that occur due to fluctuations in fuel supply amount due to air-fuel ratio feedback control, and when the vehicle is running at low engine speed or It is possible to improve stability and smoothness when the vehicle is running at high speed.

[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. 3 is a flowchart showing an example of a program to be executed. 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 1

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 load of the engine; a second detection means for detecting the state of transmission of the output of the engine to the drive wheels; a third detection means for detecting the
, the second and third detection means determine that the vehicle is running at a predetermined low engine speed or vehicle speed while the engine is being operated at a light load and its output is being transmitted to the drive wheels. An air-fuel ratio control device for an engine, comprising: control means for stopping feedback control of the fuel supply means by the feedback control means when the condition is detected.