JP2712153B2 - Load detection device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for detecting a load on an engine such as an automobile. (Prior Art) Recently, there has been a tendency that higher fuel economy and operability are required for engines. From such a viewpoint, a microcomputer or the like is applied to more precisely control the fuel supply amount. . In such control, detecting the operating state of the engine more accurately may lead to an improvement in control accuracy.
The engine load is also one of important data indicating the operating state. A conventional air-fuel ratio control device using such an engine load is disclosed in, for example, JP-A-59-51147. In this device, an air-fuel ratio is detected by an oxygen sensor provided in an exhaust pipe, and a fuel injection amount is operated based on the detection result and an operation state to feedback-control the air-fuel ratio to a target value. In this case, the amount of air sucked into the cylinder per one stroke (the amount of intake air) is used as a representative of the engine load. That is, in order for the intake air amount to represent the engine load, it is necessary to assume that fuel having a correlation with the torque generated by the engine is supplied in an amount corresponding to the intake air amount. (Problems to be Solved by the Invention) However, in such a conventional load detection device, it is premised that fuel correlated with generated torque is always accurately supplied by an amount corresponding to the intake air amount. Standing,
Since the intake air amount is detected as the engine load as described above, the air-fuel ratio changes, and accordingly, even if the amount of fuel changes with respect to the intake air amount, the air-fuel ratio changes. No correction for the amount of fuel is taken into account. Therefore, in such a case, since the generated torque varies depending on the air-fuel ratio even with the same intake air amount, the intake air amount does not always represent an accurate load. For example, when the engine is operated leaner than the stoichiometric air-fuel ratio, the amount of fuel involved in combustion is small even with the same intake air amount, so that the generated torque is small. Therefore, the actual value is smaller than the load based on the intake air amount at the stoichiometric air-fuel ratio. As a result, an accurate engine load cannot be detected, which may adversely affect control using the detected result of the load, for example, control accuracy such as air-fuel ratio control and ignition timing control. Thus, using the intake air amount for engine load detection,
If load detection is performed on the assumption that the amount of fuel accompanying the amount of intake air does not always change, a slight problem occurs in terms of control accuracy. That is, in order to aim for more accurate detection of the engine load, it is desirable to take into account the difference in the amount of fuel with respect to the amount of intake air. For these reasons, it is desired to realize a device that can accurately detect the value of the engine load. However, at present, a device that detects a load suitable for air-fuel ratio control or the like has not been realized. (Object of the Invention) Accordingly, an object of the present invention is to provide a load detection device capable of always detecting an accurate engine load even if the air-fuel ratio changes. (Means for Solving the Problems) The load detection device for an internal combustion engine according to the present invention, as shown in FIG. Amount detection means a;
Operating state detecting means b for detecting an operating state of the engine;
Air-fuel ratio detection means c for detecting the current air-fuel ratio of the engine
A current fuel-air ratio determining means d for obtaining a current fuel-air ratio from a ratio between the current air-fuel ratio and the stoichiometric air-fuel ratio; and a current fuel-air ratio determined by the current fuel-air ratio determining means d. Load detecting means e for obtaining an engine load correlated with the generated torque from the intake air amount detected by the intake air amount detecting means a.
And (Operation) In the present invention, while the intake air amount of the engine is detected by the intake air amount detection means, the current fuel-air ratio is determined from the ratio between the stoichiometric air-fuel ratio and the current air-fuel ratio by the current fuel-air ratio determination means. Then, the detected value of the intake air amount is corrected to a value corresponding to the load using the current fuel-air ratio. Therefore, it is possible to accurately detect the value of the engine load despite the change of the current value of the air-fuel ratio. Hereinafter, the present invention will be described with reference to the drawings. 2 to 9 show an embodiment of the present invention, in which the present invention is applied to an SPi (Single Point Injection) system engine. First, the configuration will be described. In Figure 2, 1 is the engine, the intake air through a throttle chamber 3 from the air cleaner 2, to ON / OFF by the heater control signal S _H PT
After being heated by C heater 4, intake manifold 5
And the fuel is supplied to each cylinder from the
Injection is performed by a single injector 7 provided on the upstream side of the throttle valve 6 based on _Ti . An ignition plug 10 is mounted on each cylinder, and a high-voltage pulse PULSE from an ignition coil 12 is supplied to the ignition plug 10 via a distributor 11. These spark plugs 10, distributor 11 and ignition coil 12 constitute the ignition means 13 for igniting air-fuel mixture, ignition means 13 to generate a high voltage pulse PULSE discharge based on the ignition signal S _IGN. The air-fuel mixture in the cylinder ignites and explodes due to the discharge of the high-voltage pulse PULSE, becomes exhaust gas, and emits harmful substances (CO, HC, NO
_X ) is purified by the three-way catalyst and discharged from the muffler 16. Here, the flow of the intake air is controlled by the throttle valve 6 in the throttle chamber 3 that is linked to the accelerator pedal, and the throttle valve 6 is almost closed when idling. The flow of air when idling is
The street, ISC valve based on the opening signal S _ISC (Idle Spee
d Control Valve (idle control valve) 21 ensures necessary air as needed. A swirl control valve 22 is provided near the intake port of each cylinder.
Is connected to a servo diaphragm 24 via a rod 23. A predetermined control negative pressure is guided from the solenoid valve 25 to the servo diaphragm 24, and the solenoid valve 25 _{converts the} negative pressure supplied from the intake manifold 5 to the atmosphere based on the swirl control signal S _SCV having the duty value D _SCV. The control negative pressure introduced into the servo diaphragm 24 is continuously changed by leaking (leaking). The servo diaphragm 24 responds to the control negative pressure, and the swirl control valve
Adjust the opening of 22. The swirl control valve 22, the rod 23, the servo diaphragm 24, and the solenoid valve 25 constitute a swirl operating means 26 as a whole. The opening α of the throttle valve 6 is detected by a throttle sensor 30, and the coolant temperature T _W is detected by a coolant temperature sensor 31. The crank angle Ca of the engine is detected by a crank angle sensor 32 built in the distributor 11, and the number of pulses representing the crank angle Ca can be counted to find the engine speed N. An oxygen sensor 33 is attached to the exhaust pipe 14, and the oxygen sensor 33 is connected to an air-fuel ratio detection circuit 34. Air-fuel ratio detecting circuit 34 supplies the pump current I _P to the oxygen sensor 33, the oxygen concentration in the exhaust gas from the value of the pump current I _P can be detected over a wide range from rich to lean. The oxygen sensor 33 and the air-fuel ratio detection circuit 34 constitute air-fuel ratio detection means 35 for detecting the current air-fuel ratio of the engine.
The air-fuel ratio detection information by the air-fuel ratio detection means 35 is input to the controller 50. The operating position of the transmission is detected by the position sensor 36, and the speed _SVSP of the vehicle is detected by the vehicle sensor 37. Also,
The operation of the air conditioner is detected by the air conditioner switch 38,
The operation of the power steering is detected by a power steering detection switch 39. Sensors other than the oxygen sensor 33, that is, the throttle sensor 30, the water temperature sensor 31, the crank angle sensor 32, the position sensor 36, the vehicle speed sensor 37, the air conditioner switch 38, and the power steering detection switch 39 (hereinafter simply referred to as each sensor) detect the operating state. These signals are input to the control unit 50 in the same manner as the detection information of the air-fuel ratio detection circuit 34. And control unit 50
Performs combustion control (ignition timing control, fuel injection control, etc.) of the engine based on the input from each sensor and the air-fuel ratio detection circuit. The control unit 50 includes a CPU 51, a ROM 52, a RAM 5
3 and the I / O port 54, which function as intake air amount detection means, target air-fuel ratio setting means, current fuel-air ratio determination means, and load detection means in the present invention by the operation described later. CPU51 follows the program written in ROM52
While taking in external data required from the I / O port 54, and exchanging data with the RAM 53, calculate the processing values required for engine combustion control, and process the processed data as necessary. Output to I / O port 54. While signals from the sensors 30, 31, 32, 36, 37, 38, and 39 are input to the I / O port 54, the I / O port 54 outputs an injection signal S _Ti to the injector 7 and an ignition signal. Ignition signal S to means 13
_IGN, opening signal S _ISC to ISC valve 21, the heater control signal S _H to the swirl control signals S _SCV and PTC heater 4 to the electromagnetic valve 25 is output, respectively. The ROM 52 stores a calculation program for the CPU 51, and the RAM 53 stores data used for calculation in the form of a map or the like. Note that a part of the RAM 53 is composed of a nonvolatile memory, and retains its stored contents even after the engine 1 is stopped. Next, the operation will be described. First, the air flow rate calculation system will be described. In the present embodiment, a conventional air flow meter or the like is not provided for detecting the air flow rate, and the air amount Q _Ainj (hereinafter, the air amount passing through the injector unit) passing through the injector unit 7 using the throttle opening α and the engine speed N as parameters. (Hereinafter simply referred to as α-N system). The injector-part passing air amount Q _Ainj is calculated by the α-N system for the following reason. That is, according to the conventional sensor described above, (a) the fluctuation of the sensor output due to the intake pulsation is large, which causes the fluctuation of the fuel injection amount and the torque fluctuation. (B) In terms of sensor responsiveness, detection errors increase during transients. (C) The cost of the above sensor is relatively high. For this reason, the present embodiment employs an α-N system which is low in cost and excellent in responsiveness and detection accuracy. In particular, in the case of the SPi type engine, by employing such an α-N system, the control accuracy of the air-fuel ratio is remarkably improved. The following shows the amount of air passing through the injector section by this system.
The calculation of Q _Ainj will be described. FIG. 3 is a flowchart showing a program for calculating the cylinder air amount Q _Acyl . First, stored in a memory as old value Q _Acyl 'the last Q _Acyl at P _0. Where Q
_Acyl is the amount of intake air passing through the cylinder portion and is equivalent to the amount of intake air Q _a (engine load T _P ) in a conventional device (eg, an EGi type engine), and is shown in FIG. Air quantity Q in injector section by program
_This is the basic data for calculating _Ainj . Then, the necessary data in P _1, i.e. the throttle opening alpha, ISC valve 2
The duty (hereinafter referred to as ISC duty) D _ISC of the opening signal S _ISC to 1 and the engine speed N are read. Flow area in the portion where the throttle valve 6 is mounted on the basis of the P in the _second throttle opening alpha (hereinafter, referred to as the throttle valve passage area) is calculated A.alpha. This is determined by, for example, looking up the corresponding value of Aα from the table map shown in FIG. In P ₃ in the same manner ISC duty D
Calculating a fifth view of the bypass passage area from a table map A _B Based on _ISC, it determines the total flow area A according to the following equation by P _4. A = Aα + A _B ...... then calculated steady air amount Q _H in P _5. This calculation is
First, A / N is obtained by dividing the total flow area A by the engine speed N, and the corresponding steady air amount Q is obtained from a table map as shown in FIG. Look up the value of _H. Then, taking into account the volume of the intake manifold 5 from the table map shown in FIG. 7 and A and N as a parameter to look up the delay coefficient K2 by at P _6, calculates the cylinder air quantity Q _Acyl according to the following equation by P ₇ And terminate the routine. _{Q Acyl = Q Acyl '× (} 1-K2) + Q H × K2 ...... However, Q _Acyl': cylinder air quantity Q _Acyl found by the value thus stored in P ₁ is SPi method as in this embodiment Instead, the present invention can be applied to an EGi type engine that injects fuel near the intake port, for example. However, since the present embodiment is of the SPi type, it is necessary to find the injector unit air amount Q _Ainj , and this calculation is performed by the program shown in FIG. In the program first determines the intake pipe air amount variation ΔCM according to the following equation at P _11. This ΔCM means the amount of air for changing the pressure of the air in the throttle chamber 3 during transition with respect to the cylinder air amount Q _Acyl . In _{ΔCM = K M + (Q Acyl} -Q Acyl ') / N ...... equation, K _M is a constant determined depending on the volume of the intake manifold 5, the optimum value is selected depending on the type of the engine 1 Is done. Then calculated injector unit air quantity Q _Ainj according to the following equation at P _12. Q _Ainj = Q _Acyl + ΔCM ...... The Q _Ainj obtained in this way has extremely high responsiveness because the throttle valve opening α is one of the information parameters, and is calculated using a table map based on experimental data. Therefore, it is accurately correlated with the actual value and has high detection accuracy (high resolution). Furthermore, the cost can be reduced because only the software needs to be handled by the microcomputer using the existing sensor information. In particular, it is very convenient to apply to a type in which fuel is injected upstream of the throttle chamber 3 as in the SPi system. Next, the operation of the present paper will be described. FIG. 9 is a flowchart showing a program for engine load detection. First, a parameter indicative of the engine load P ₂₁ (Q _Acyl ×
TFBYA) is within a predetermined range. Here, Q _Acyl is calculated by the program in FIG. 3 and indicates the amount of air taken in per stroke. TFBYA is a fuel-air ratio corresponding to the reciprocal of the excess air ratio λ. The fuel-air ratio TFBYA is expressed by the following equation from the stoichiometric air-fuel ratio and the current air-fuel ratio. Fuel-to-air ratio TFBYA = 1 / Excess air ratio λ = Theoretical air-fuel ratio (14.7 for gasoline) / Current air-fuel ratio …… This fuel-air ratio TFBYA calculated using the current air-fuel ratio
(Current fuel-air ratio) is a constant value 1 when the current air-fuel ratio matches the stoichiometric air-fuel ratio, and otherwise, it is a value dependent only on the current air-fuel ratio. Therefore, the parameter (Q _Acyl × TFBYA) obtained by multiplying the cylinder air amount Q _Acyl by the current fuel-air ratio TFBYA represents an accurate engine load that is not affected by the change in the air-fuel ratio. When obtaining the fuel-air ratio TFBYA in accordance with the formula, the current air-fuel ratio may be the previous value detected by the air-fuel ratio detecting means 35 or a value newly detected this time. In this embodiment, based on the parameter (Q _Acyl × TFBYA), for example, the parameter falls within a predetermined range (L ≦ Q _Acyl × TFB
If not YA <H) is determined not to be setting condition of a lean air-fuel ratio, to select a stoichiometric (current fuel-air ratio TFBYA = 1) at P _22. Here, L and H are predetermined constants, and the setting thereof may be variable depending on the operating state or the like. Further, when the parameter is within a predetermined range, it performs other lean determination at P _23. The other lean determination is to determine whether it is appropriate to select an air-fuel ratio in a lean region based on an operating state such as an engine cooling water temperature, a vehicle speed, an engine speed, and the like. when not under determines that the selection of the lean region is not appropriate, the process proceeds to P _22. On the other hand, when satisfies a predetermined condition for selecting the lean target air-fuel ratio at P _24. As described above, in the present embodiment, the current fuel-air ratio is obtained from the ratio between the stoichiometric air-fuel ratio and the current air-fuel ratio, and this is multiplied by the cylinder air amount to detect the engine load. Even so, an accurate load can always be detected, and a precise lean determination can be made. Further, in this embodiment, no special sensor or member is required, and a conventional component can be used as it is, so that it is not necessary to modify the heart surface of the apparatus. That is, since the device can be provided only by the software, it is possible to prevent the device from becoming complicated and increasing the cost. As a result, it matches systems such as air-fuel ratio control or ignition timing control,
It is possible to provide a load detection device that meets recent high-level requirements. In the present embodiment, the aspect in which the present invention is applied to the air-fuel ratio control device is shown. However, the application field of the present invention is not limited to such air-fuel ratio control, but may be based on operating conditions such as engine load. It is, of course, possible to apply the present invention to so-called ignition timing control in which the ignition timing is controlled by the ignition timing control. That is, the present invention can be applied to all devices that detect the load of the engine, and the load detection accuracy of the present invention is extremely high. Therefore, it is possible to increase the control accuracy of these devices. it can. (Effect) According to the present invention, the engine load is detected by appropriately correcting the detected value of the intake air amount based on the current fuel-air ratio obtained from the ratio between the stoichiometric air-fuel ratio and the current air-fuel ratio. Therefore, it is possible to detect an accurate engine load regardless of a change in the air-fuel ratio.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a basic conceptual diagram of the present invention. 2 to 9 are views showing an embodiment of the present invention. FIG.
FIG. 4 is a flowchart showing a program for calculating the cylinder air amount Q _Acyl . FIG. 4 is a flowchart showing the throttle valve flow area A.
table maps the alpha, Fig. 5 table maps the bypass passage area A _B, Fig. 6 is constant for a parameter and A / N and the engine speed N obtained by dividing the Soryuro area A by the engine speed N table maps the air amount Q _H, Fig. 7 is a table map of the delay coefficient K2, FIG. 8 is a flowchart showing a calculation program of the injector portion air amount Q _Ainj,
FIG. 9 is a flowchart showing the load detection program. 1 ... engine, 30 ... throttle sensor, 31 ... water temperature sensor, 32 ... crank angle sensor, 33 ... oxygen sensor, 34 ... air-fuel ratio detection circuit, 35 ... air-fuel ratio detection means, 36 ... position Sensor, 37… Vehicle speed sensor, 38 …… Air conditioner switch, 39 …… Power steering detection switch, 50 …… Control unit.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Hiroshi Sanichi               2 Takaracho, Kanagawa-ku, Yokohama-shi Nissan Motor               Inside the corporation                (56) References JP-A-59-120748 (JP, A)                 Japanese Patent Publication No. 58-33386 (JP, B2)

Claims (1)

(57) [Claims] a) intake air amount detecting means for detecting an intake air amount of the engine; b) operating state detecting means for detecting an operating state of the engine; c) air-fuel ratio detecting means for detecting a current air-fuel ratio of the engine; d. E) current fuel / air ratio determining means for obtaining a current fuel / air ratio from the ratio between the current air / fuel ratio and the stoichiometric air / fuel ratio; and e) current fuel / air ratio determined by the current fuel / air ratio determining means and A load detecting device for an internal combustion engine, comprising: load detecting means for obtaining an engine load correlated with the generated torque from the intake air amount detected by the intake air amount detecting means.