JP2006046071A - Atmospheric pressure estimating device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve estimation precision of atmospheric pressure during downhill travel. <P>SOLUTION: The device determines whether or not a vehicle is under a downhill travel in which a vehicle travels downhill in an idling operation state on the basis of a continuous time in an idling operation state, a vehicle speed and a vehicle acceleration. At a normal time (when not under an idling downhill travel), an estimated atmospheric pressure is calculated on the basis of throttle opening, an intake pipe pressure, or the like. When a vehicle is under an idling downhill travel, an estimated road gradient is calculated in accordance with the change amount of the vehicle speed and the demand torque. The estimated atmospheric pressure is acquired by correcting the previous estimated atmospheric pressure by employing an estimated road gradient, a travel distance per prescribed period (vehicle speed × prescribed period) and a conversion factor. By so doing, the estimated atmospheric pressure is acquired by correcting the previous atmospheric pressure by a portion of the atmospheric pressure change resulting from a change in altitude. As a result, even if a vehicle travels downhill in an idling operation state where the throttle opening is reduced, the estimated atmospheric pressure is precisely calculated at a prescribed operation cycle to be updated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicle atmospheric pressure estimation device for the purpose of improving atmospheric pressure estimation accuracy.

  In general, while the vehicle is running, the atmospheric pressure changes due to a change in altitude and the like, and the density (mass flow rate) of the intake air changes. Therefore, in order to improve the air-fuel ratio control accuracy of the internal combustion engine, according to the atmospheric pressure It is necessary to correct the air-fuel ratio control parameter. However, if an atmospheric pressure sensor for detecting atmospheric pressure is provided, the cost increases accordingly.

  Therefore, in order to reduce the cost, as described in Patent Document 1 (Japanese Patent Publication No. 5-38894), when the throttle opening is close to full open without using the atmospheric pressure sensor, the throttle valve downstream side. Focusing on the fact that the intake pipe pressure detected by the intake pipe pressure sensor is almost equal to the atmospheric pressure, the detected value of the intake pipe pressure sensor is estimated to be the atmospheric pressure every time the throttle opening is nearly fully open. In some cases, the value obtained by performing the annealing process is finally updated and stored as a detected value of the atmospheric pressure.

Further, as described in Patent Document 2 (Japanese Patent Laid-Open No. 2000-345910), the throttle opening detected by the throttle opening sensor and the intake pipe detected by the intake pipe pressure sensor without using the atmospheric pressure sensor. Some have estimated the atmospheric pressure based on the pressure.
Japanese Patent Publication No. 5-38894 (first page, etc.) JP 2000-345910 A (second page, etc.)

  By the way, in general, when the vehicle travels on a downhill, the throttle opening is hardly opened to the vicinity of the fully open position, so that the intake air when the throttle opening is about the fully open position as in Patent Document 1 above. In the method of updating the detection value of the atmospheric pressure using the detection value of the pipe pressure sensor, the atmospheric pressure is changed even though the altitude of the road is actually decreasing and the atmospheric pressure is changing during downhill driving. A situation occurs in which the detection value is not updated. For this reason, there is a drawback that an error in the atmospheric pressure detection value increases during traveling downhill.

  On the other hand, in the method of estimating the atmospheric pressure based on the throttle opening and the intake pipe pressure as in Patent Document 2, the estimated atmospheric pressure can be calculated and updated at a predetermined calculation cycle even while traveling downhill. it can. However, during downhill driving, the throttle opening is often closed to close to close the engine brake, so even if the atmospheric pressure actually changes due to altitude change due to downhill driving, the atmospheric pressure change Is less likely to appear in the output of the intake pipe pressure sensor downstream of the throttle valve. Further, in the vicinity of the throttle fully closed, it is easily affected by a throttle opening detection error and a variation in the machine difference of the throttle. For this reason, during downhill traveling, there is a drawback that the estimation accuracy of the atmospheric pressure based on the throttle opening and the intake pipe pressure is reduced.

  The present invention has been made in consideration of these circumstances. Accordingly, an object of the present invention is to provide an atmospheric pressure estimation device for a vehicle that can improve the estimation accuracy of atmospheric pressure during downhill traveling. It is in.

  In order to achieve the above object, an atmospheric pressure estimation device for a vehicle according to claim 1 of the present invention is a system for estimating atmospheric pressure based on the operating state of an internal combustion engine mounted on a vehicle by atmospheric pressure estimation means. Then, it is determined whether the throttle opening degree of the internal combustion engine is a predetermined value or less or the required torque is a predetermined value or less by the low load operation determination means, and the vehicle speed is detected by the vehicle speed detection means. Further, the road gradient detecting unit estimates or detects the road gradient on which the vehicle is traveling, and the low load downhill traveling determination unit calculates the low load based on the duration of the low load driving state, the vehicle speed, and the vehicle speed change rate. It is determined whether or not the vehicle is running on a low-load downhill running downhill in the driving state. Based on the road gradient and the vehicle speed estimated or detected by the road gradient detection means during the period when the low load downhill travel determination means determines that the vehicle is running at a low load downhill, the previous estimation by the atmospheric pressure estimation means is performed. The estimated atmospheric pressure of this time is obtained by correcting the atmospheric pressure.

  While the vehicle is running on a downhill, the vehicle speed and the speed of change of the vehicle speed (that is, the acceleration) are maintained even if the throttle opening is less than the predetermined value or the low load operation state (for example, the idle operation state) where the required torque is less than the predetermined value continues. It is maintained in a somewhat large state. Therefore, by using the duration of the low load operation state, the vehicle speed, and the change speed of the vehicle speed, it is possible to determine whether or not the vehicle is running on a low load downhill traveling downhill in the low load operation state.

  Moreover, since the altitude changes and the atmospheric pressure changes according to the gradient of the traveling road and the distance traveled (vehicle speed × time), the road gradient detecting means is used during the period when it is determined that the vehicle is traveling on a low load downhill. If the previous estimated atmospheric pressure is corrected using the estimated or detected road gradient and the vehicle speed, the previous estimated atmospheric pressure can be corrected by an amount corresponding to the change in atmospheric pressure due to the change in altitude. This makes it possible to accurately calculate and update the estimated atmospheric pressure at an appropriate cycle even when traveling downhill in a low-load operation state where the throttle opening is small, and the estimated accuracy of atmospheric pressure during downhill traveling Can be improved.

  In this case, as in claim 2, during a period in which it is determined that the vehicle is not traveling on a low load downhill (that is, in an operating state other than the low load downhill traveling), the throttle opening of the internal combustion engine, the intake pipe pressure, etc. It is preferable to estimate the atmospheric pressure based on. In this way, when operating in a state other than low-load downhill traveling, if atmospheric pressure is estimated based on the throttle opening and intake pipe pressure, etc., The atmospheric pressure can be estimated with high accuracy.

  In the above claim 1, it is determined whether or not the vehicle is traveling on a low load downhill on the basis of the duration of the low load operation state, the vehicle speed, and the speed of change of the vehicle speed (that is, acceleration). As in item 3, it may be determined whether or not the vehicle is traveling on a low load downhill on the basis of the duration of the low load operation state and the road gradient estimated or detected by the road gradient detection means. Even in this case, it is possible to accurately determine whether or not the vehicle is traveling on a low load downhill.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. On the downstream side of the air flow meter 14, a throttle valve 15 whose opening is adjusted by a DC motor or the like and a throttle opening sensor 16 for detecting the throttle opening are provided.

  Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 19 of each cylinder. Yes. A spark plug 21 is attached to each cylinder of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each spark plug 21.

  On the other hand, the exhaust pipe 22 of the engine 11 is provided with a catalyst 23 such as a three-way catalyst that purifies CO, HC, NOx, etc. in the exhaust gas. / An exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting lean or the like is provided.

  A cooling water temperature sensor 25 that detects the cooling water temperature and a crank angle sensor 26 that outputs a pulse signal each time the crankshaft of the engine 11 rotates a predetermined crank angle are attached to the cylinder block of the engine 11. Based on the output signal of the crank angle sensor 26, the crank angle and the engine speed are detected. Further, the accelerator opening (the driver's accelerator operation amount) is detected by the accelerator sensor 28, and the vehicle speed is detected by the vehicle speed sensor 29 (vehicle speed detecting means).

  Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 27. The ECU 27 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 20 according to the engine operating state. The ignition timing of the spark plug 21 is controlled.

  At that time, the ECU 27 calculates a required torque based on the accelerator opening detected by the accelerator sensor 28 and controls the generated torque of the engine 11 based on the required torque.

  Further, the ECU 27 calculates an estimated atmospheric pressure Pa as follows by executing an atmospheric pressure estimation program shown in FIG. 3 described later. First, based on the duration of the idle operation state, the vehicle speed detected by the vehicle speed sensor 29, and the vehicle acceleration (change speed of the vehicle speed), it is determined whether or not the vehicle is in the idle downhill traveling that travels downhill in the idle operation state. Determine. Here, the idle operation state is an operation state in which the idle switch is turned on. For example, the accelerator opening becomes 0 and the throttle opening becomes less than a predetermined value (near full close) or the required torque becomes less than a predetermined value. It is a driving state.

  While the vehicle is traveling downhill, the vehicle speed and the vehicle acceleration are maintained at a certain level even if the idling operation state continues. Therefore, using the duration of the idling operation state, the vehicle speed, and the vehicle acceleration, it can be determined whether or not the idling downhill traveling in the idling driving state is in progress.

  Then, as shown in FIG. 2, in normal times (when it is determined that the vehicle is not running on an idling downhill), the throttle opening φ detected by the throttle opening sensor 16 and the intake pipe pressure sensor 18 are detected. Based on the intake pipe pressure Pm and the intake air amount Ga detected by the air flow meter 14, the estimated atmospheric pressure Pa is calculated using the following theoretical formula, for example.

  Here, C is a flow coefficient, A (φ) is a throttle cross-sectional area (intake flow passage cross-sectional area that changes according to the throttle opening φ), R is a gas constant, and T is an intake air temperature.

  The method for calculating the estimated atmospheric pressure Pa may be changed as appropriate. For example, the estimated atmospheric pressure Pa may be calculated based on the throttle opening φ and the intake pipe pressure Pm. When the throttle opening φ is larger than a predetermined value, the intake pipe pressure sensor 18 detects the intake pipe pressure Pm (pressure in the surge tank 17) almost equal to the atmospheric pressure. The intake pipe pressure Pm may be adopted as the estimated atmospheric pressure Pa.

  On the other hand, as shown in FIG. 2, when it is determined that the vehicle is traveling on an idle downhill, the amount of change in the vehicle speed detected by the vehicle speed sensor 29 per predetermined period is calculated, and the accelerator detected by the accelerator sensor 28 is calculated. The required torque is calculated based on the opening degree and the like, and the estimated road gradient according to the amount of change in the vehicle speed and the required torque is calculated using a map or a mathematical expression. The estimated road gradient map is set in advance based on design data, experimental data, and the like, and is stored in the ROM of the ECU 29. Although the generated torque of the engine 11 changes according to the required torque and the vehicle speed changes, the relationship between the required torque and the amount of change in the vehicle speed changes depending on the gradient of the traveling road at that time. Therefore, the estimated road gradient can be calculated by using the required torque and the amount of change in the vehicle speed.

  After calculating the estimated road gradient, the previous estimated atmospheric pressure Pa (i-1) is corrected by the following equation using the estimated road gradient, travel distance per predetermined period (vehicle speed x predetermined period), and conversion coefficient. Estimated atmospheric pressure Pa (i) is obtained.

Estimated atmospheric pressure Pa (i) = Estimated atmospheric pressure Pa (i-1) + Conversion coefficient x Estimated road slope x Travel distance Here, [Estimated road slope x Travel distance] corresponds to the elevation change of the travel road per predetermined period. The conversion coefficient is a coefficient for converting an altitude change into an atmospheric pressure change. Thereby, the previous estimated atmospheric pressure Pa (i-1) is corrected by an amount corresponding to the change in atmospheric pressure due to the altitude change, and the current estimated atmospheric pressure Pa (i) is obtained.

Hereinafter, the processing content of the atmospheric pressure estimation program of FIG. 3 executed by the ECU 27 will be described.
The atmospheric pressure estimation program shown in FIG. 3 is executed at predetermined intervals during engine operation, and serves as atmospheric pressure estimation means in the claims. When this program is started, first, in step 101, it is determined whether or not the engine is in an idle operation state. The process of step 101 serves as a low load operation determination means in the claims.

As a result, when it is determined that the engine is in the idle operation state, the process proceeds to step 202, and the duration of the idle operation state is calculated.
After this, in steps 103 to 104, whether or not the vehicle is in an idle downhill running in an idling state is determined by whether or not all of the following conditions (1) to (3) are satisfied, for example: judge.

(1) The duration of the idle operation state exceeds a predetermined value (step 103)
(2) The vehicle speed exceeds a predetermined value (step 104)
(3) The vehicle acceleration (change speed of the vehicle speed) exceeds a predetermined value (step 105).
If all of the above conditions (1) to (3) are satisfied, it is determined that the vehicle is traveling on an idling downhill, but if there is a condition that does not satisfy one of the above conditions (1) to (3), It is determined that the vehicle is not idling downhill. The processing of these steps 103 to 105 serves as a low-load downhill traveling determination means referred to in the claims.

  As a result, if it is determined that the vehicle is traveling on an idling downhill, the process proceeds to step 106, and an estimated road gradient corresponding to the required torque and the amount of change in vehicle speed is calculated using a map (see FIG. 2) or a mathematical expression. . The processing in step 106 serves as road gradient detection means in the claims.

Thereafter, the routine proceeds to step 107, where the previous estimated atmospheric pressure Pa (i-1) is corrected by the following equation using the estimated road gradient, the travel distance per predetermined period (vehicle speed × predetermined period), and the conversion coefficient. The estimated atmospheric pressure Pa (i) is obtained.
Estimated atmospheric pressure Pa (i) = Estimated atmospheric pressure Pa (i-1) + Conversion coefficient x Estimated road gradient x Travel distance

  On the other hand, if it is determined in step 101 that the vehicle is not idling, or if it is determined in steps 103 to 105 that the vehicle is not idling downhill, the routine proceeds to step 108 where the throttle opening sensor 16 Based on the throttle opening φ detected in step S1, the intake pipe pressure Pm detected by the intake pipe pressure sensor 18, and the intake air amount Ga detected by the air flow meter 14, for example, using the above equation (1), The atmospheric pressure Pa is calculated.

  In the present embodiment described above, during the idling downhill traveling in the idling state, the previous estimated atmospheric pressure Pa (i-1) is calculated based on the estimated road gradient and the traveling distance per predetermined period (vehicle speed × predetermined period). ) And the conversion coefficient to obtain the current estimated atmospheric pressure Pa (i), and the previous estimated atmospheric pressure Pa (i-1) is corrected by the atmospheric pressure change due to the altitude change. Since the estimated atmospheric pressure Pa (i) is obtained, the estimated atmospheric pressure Pa can be accurately calculated and updated at a predetermined calculation cycle even when the vehicle is traveling downhill in an idling state where the throttle opening is small. It is possible to improve the estimation accuracy of atmospheric pressure during downhill travel.

  In the present embodiment, the atmospheric pressure is estimated based on the throttle opening, the intake pipe pressure, etc. in the same manner as in the past during the period when it is not determined that the vehicle is running on an idling downhill. Thus, the atmospheric pressure can be estimated with high accuracy.

  In the above-described embodiment, it is determined whether or not the vehicle is running on an idling downhill based on the duration of the idle operation state, the vehicle speed, and the vehicle acceleration. However, the duration of the idle operation state and the estimated road gradient are determined. Based on the above, it may be determined whether or not the vehicle is traveling on an idling downhill. Even in this case, it is possible to accurately determine that the vehicle is in the idle downhill traveling in the idle operation state.

In the above embodiment, the road gradient is estimated based on the required torque and the vehicle speed. However, the road gradient may be detected by, for example, a sensor that detects the inclination of the vehicle.
Further, in the above embodiment, the present invention is applied to the atmospheric pressure estimation during idling downhill traveling downhill in the idling operation state, but is not limited to idling downhill traveling, and the throttle opening is equal to or less than a predetermined value or The present invention may be applied to atmospheric pressure estimation during low load downhill traveling that travels downhill in a low load operation state where the required torque is a predetermined value or less (for example, an operation state where the accelerator opening is slightly larger than 0). .

It is a schematic block diagram of the whole engine control system in one Example of this invention. It is a block diagram for demonstrating the atmospheric pressure estimation function of ECU. It is a flowchart which shows the flow of a process of an atmospheric pressure estimation program.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter, 15 ... Throttle valve, 16 ... Throttle opening sensor, 18 ... Intake pipe pressure sensor, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 27 ... ECU (atmospheric pressure estimation means, low load operation determination means, road gradient detection means, low load downhill travel determination means), 28 ... accelerator sensor, 29 ... vehicle speed sensor 29 (vehicle speed detection means)

Claims (3)

In an atmospheric pressure estimation device for a vehicle provided with an atmospheric pressure estimating means for estimating an atmospheric pressure based on an operating state of an internal combustion engine mounted on the vehicle,
Low load operation determination means for determining whether or not the throttle opening of the internal combustion engine is a low load operation state with a predetermined value or less or a required torque being a predetermined value or less;
Vehicle speed detection means for detecting the vehicle speed;
Road gradient detecting means for estimating or detecting the gradient of the road on which the vehicle is traveling;
A low-load downhill that determines whether or not the vehicle is running on a low-load downhill traveling downhill in the low-load operation state based on the duration of the low-load operation state, the vehicle speed, and the speed of change of the vehicle speed Traveling determination means,
The atmospheric pressure estimating means is based on the road gradient and the vehicle speed estimated or detected by the road gradient detecting means during the period when the low load downhill running judging means is judged to be running at a low load downhill. An atmospheric pressure estimation device for a vehicle, wherein the estimated atmospheric pressure of the vehicle is obtained by correcting the estimated atmospheric pressure of the previous time by the atmospheric pressure estimating means.   The atmospheric pressure estimation means estimates the atmospheric pressure based on the throttle opening of the internal combustion engine, the intake pipe pressure, and the like during a period when the low load downhill running judgment means determines that the low load downhill running is not running. The atmospheric pressure estimation device for a vehicle according to claim 1, wherein: In an atmospheric pressure estimation device comprising atmospheric pressure estimation means for estimating atmospheric pressure based on the operating state of an internal combustion engine mounted on a vehicle,
Low load operation determination means for determining whether or not the throttle opening of the internal combustion engine is a low load operation state with a predetermined value or less or a required torque being a predetermined value or less;
Vehicle speed detection means for detecting the vehicle speed;
Road gradient detecting means for estimating or detecting the gradient of the road on which the vehicle is traveling;
Based on the duration of the low load operation state and the road gradient estimated or detected by the road gradient detection means, it is determined whether or not the vehicle is running on a low load downhill traveling downhill in the low load operation state. A low load downhill traveling determination means,
The atmospheric pressure estimating means is based on the road gradient and the vehicle speed estimated or detected by the road gradient detecting means during the period when the low load downhill running judging means is judged to be running at a low load downhill. An atmospheric pressure estimation device for a vehicle, wherein the estimated atmospheric pressure of the vehicle is obtained by correcting the estimated atmospheric pressure of the previous time by the atmospheric pressure estimating means.

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