JP2807730B2 - Failure detection method of load sensor of internal combustion engine - Google Patents

Description

The present invention relates to a method for detecting a failure of a load sensor of an internal combustion engine. (Prior art and its problems) In general, in an electronically controlled automatic transmission connected to an internal combustion engine, it is necessary to detect an engine load as a control parameter for performing shift control and lockup control of a fluid torque converter. It is essential. As such a sensor for detecting the engine load, there are a throttle valve opening sensor for detecting the opening of the throttle valve, an intake pipe absolute pressure sensor for detecting the absolute pressure in the intake pipe, and the like. When a failure occurs in any of these engine load sensors, normal control of the automatic transmission cannot be performed. Therefore, the failure of such a sensor is detected, and fail-safe processing such as shift control and failure display corresponding to the failure is detected. It is necessary to do. As a conventional method of detecting a failure of a load sensor of an internal combustion engine, when an output signal value of the engine load sensor becomes a value outside a range of a signal value that can be output in a normal state, it is determined that a failure due to disconnection or short circuit has occurred. A known method is known (for example, Japanese Patent Publication No. Sho 60-10222). However, when the engine load sensor fails, the output signal value does not always become an abnormal value outside the normal value range, and a failure such as staying at a constant value within the normal value range can be assumed. Therefore, the conventional method has a problem that even if such a failure occurs, it cannot be detected. (Object of the Invention) The present invention has been made in view of the above circumstances, and detects a failure other than when an output signal value of an engine load sensor becomes an abnormal value, thereby improving the reliability of failure detection of an internal combustion engine. An object of the present invention is to provide a load sensor failure detection method. (Constitution of the Invention) In order to achieve the above object, according to the present invention, the load of an internal combustion engine in a vehicle that transmits the output of the internal combustion engine to driving wheels via an automatic transmission including a fluid torque converter is provided. The output signal value from the load sensor indicates an engine load equal to or less than a predetermined value, and the output shaft rotation speed of the fluid torque converter is the input shaft of the fluid torque converter. When the rotation speed is lower than the rotation speed and the speed difference is larger than a predetermined value, it is determined that the load sensor has failed, and a load sensor failure detection method for an internal combustion engine is provided. Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an automatic transmission with a fluid torque converter connected to an internal combustion engine. An automatic transmission M is connected to a crankshaft 1 of an engine E via a fluid torque converter T.
Is connected. The fluid torque converter T includes a pump wheel 31 connected to a crankshaft (that is, an input shaft of the torque converter T) 1.
A turbine wheel 32 connected to an output shaft 2 of the fluid torque converter T (that is, an input shaft of the automatic transmission M) 2, and a stator wheel 33 disposed between the two wheels 31, 32. You. The torque transmitted from the input shaft 1 to the pump impeller 31 is hydrodynamically transmitted to the turbine impeller 32, and the direction of the fluid flow returning from the turbine impeller 32 to the pump impeller 31 is changed in a known manner. The rotation direction of the pump impeller 31 is changed by the wheel 33 in the same direction as that of the pump wheel 31, and the torque is amplified. In the illustrated example, the automatic transmission M includes an input shaft 2 connected to an output shaft of a torque converter T, an output shaft 3 connected to driving wheels (not shown) of the vehicle, and an input / output shaft 2, The low-speed clutch CL is provided between the low-speed clutch CL and the high-speed clutch CH. When the low-speed clutch CL is engaged, power is transmitted to the output shaft 3 via the low-speed gears 4 and 6, while the high-speed clutch CH
At the time of engagement, power is transmitted to the output shaft 3 via the high-speed gears 5 and 7. FIG. 2 is an overall configuration diagram of a control device of the automatic transmission M. In FIG. 2, a hydraulic pump 8 sucks hydraulic oil from an oil tank 9 and feeds it to hydraulic oil passages 11 and 20. This pressure oil is adjusted to a predetermined pressure by a pressure adjusting valve 29, and then is manually operated.
Sent to 18. The manual valve 18 is interposed between the oil passages 14 and 14 ′ branched from the hydraulic oil passage 11, has a shift range of a neutral range and a drive range, and connects the oil passages 14 and 14 ′ when in the drive range. Communicate. Oilway 1
The hydraulic pressure 4 ′ is supplied to the hydraulic passages 12 or the hydraulic passages of the low-speed clutch CL and the high-speed clutch CH in accordance with the switching operation of the shift valve 16.
13 is supplied selectively. In the shift valve 16, the spring force of the spring 19 is applied to one end surface of the spool, and the oil pressure of the oil passage 20 is applied to the other end surface via a throttle 21. The oil pressure applied to the other end surface is provided by an electromagnetic valve 23. The oil is returned to the oil tank 9 via the oil passage 22 thus set. The solenoid valve 23 is a normally closed type, and its solenoid
25 is connected to ECU24. The throttle valve opening sensor 26 for detecting the opening of the throttle valve in the intake pipe of the engine E is connected to the ECU 24. This can be constituted by a known potentiometer, for example. The ECU 24 is connected to a vehicle speed sensor 27 for detecting the speed V of the vehicle and an engine speed sensor 28 for detecting the speed Ne of the engine E. The ECU 24 operates based on input signals from a throttle valve opening sensor (hereinafter referred to as “θ _TH sensor”) 26 and a vehicle speed sensor 27 in accordance with a θ _TH -V relationship shown in FIG. Control the energization of 25. The solenoid valve 23 is a normally closed type, and closes the oil passage 22 when no power is supplied.
When energized, the oil passage 22 is opened. When the solenoid valve 23 is energized, it is pumped from the oil tank 9 by the pump 8,
The pressure is regulated by 29 and the shift valve is
The pressure oil supplied to 16 is drained to oil tank 9 via oil passage 22 and solenoid valve 23. Accordingly, the shift valve 16 is held at the illustrated position by the spring 19. At this time, if the manual valve 18 has been shifted to the drive range, the hydraulic oil pumped by the pump 8 is supplied to the oil passage 14, the manual valve 18, the oil passage 14 ',
The low-speed clutch CL is supplied via the shift valve 16 and the oil passage 12, and the low-speed clutch CL is engaged. At this time, the residual oil in the high-speed clutch CH is drained to the oil tank 9 via the oil passage 13, the shift valve 16, and the oil passage 15, so that the high-speed clutch CH
Is dissociated. On the other hand, when the solenoid valve 23 is not energized, the oil passage 22 is closed, so that the pressure oil pumped by the pump 8 and supplied through the oil passage 20 and the throttle 21 shifts against the urging force of the spring 19. Valve 16
Is moved to the left from the illustrated position. Therefore, at this time, if the manual valve 18 is shifted to the drive range,
The hydraulic oil pumped by the pump 8 is the oil passage 14, the manual valve
The oil is supplied to the high-speed clutch CH via the oil passage 14, the shift valve 16 and the oil passage 13, and the high-speed clutch CH is engaged. At this time, the residual oil in the low-speed clutch CL
Since it is drained to the oil tank 9 via 16 and the oil passage 15,
The low speed clutch CL is disengaged. When the manual valve 18 is held in the neutral range shown in the figure, the hydraulic oil pumped by the pump 8 is stopped by the manual valve 18 and the shift valve 16 is stopped.
Is in any position, the residual oil in the low-speed clutch CL and the high-speed clutch CH is drained to the oil tank 9 through the oil passages 12 and 13, the shift valve 16, and the oil passages 14 ', 15, and 17. Therefore, both the low speed clutch CL and the high speed clutch CH are disengaged. To ensure the control of the automatic transmission M described above, the ECU 2
4 is used to detect whether the θ _TH sensor 26 is operating normally. This detection is performed by the following method. When the detected throttle valve opening θ _{TH of the} θ _TH sensor 26 is within the normal value range but is smaller than a predetermined value close to the idle opening and the vehicle is running at a predetermined speed or more, for example, when the vehicle speed is high, It is considered that the engine is in a decelerating state, and the rotation speed N _OUT of the output shaft 2 of the fluid torque converter T should be higher than the rotation speed N _IN of the input shaft 1. That is, the rotation speed ratio e = N _OUT / N _IN (1) of the output shaft rotation speed N _{OUT to} the input shaft rotation speed N _IN should be 1.0 or more. Therefore, when the rotation speed ratio e is smaller than a predetermined value (for example, 0.9) smaller than 1.0 while θ _TH is smaller than the predetermined value, the actual throttle valve opening θ _TH ′ should not be smaller than the predetermined value. Therefore, in such a case, it is estimated that a failure has occurred in the θ _TH sensor 26. In the calculation of the rotation speed ratio e in the equation (1), the input shaft rotation speed N _IN and the output shaft rotation speed N _OUT are detected as follows. Since the input shaft rotation speed N _IN is equal to the engine rotation speed Ne, it is detected by the engine rotation speed sensor (hereinafter referred to as “Ne sensor”) 28. Ne
The sensor calculates an engine rotation speed Ne by detecting, for example, an interval of generation of an ignition pulse of the engine E. The output shaft rotation speed N _OUT is calculated based on the output signal value of the vehicle speed sensor 27. The vehicle speed sensor 27 includes, for example, a magnet rotor that rotates in conjunction with the transmission output shaft 3 and a reed switch that is opened and closed by the magnet rotor, and outputs a signal value representing the rotation speed N _OUT 'of the transmission output shaft 3. I do.
Therefore, the output shaft rotation speed N _OUT of the fluid torque converter T is calculated by multiplying the N _OUT ′ value by the gear ratio A of the automatic transmission M. As a result, the rotation speed ratio e in the above equation (1) is calculated by the following equation (2). e = N _OUT '· A / Ne (2) Here, the gear ratio A is the gear ratio of the low speed stage or the high speed stage, and the ECU 24 itself determines the low speed stage or the high speed stage as described above. . FIG. 4 is a flowchart of a failure detection program of the θ _TH sensor executed in the ECU 24. First, in step 1, by executing this program, θ
_When a failure of the _TH sensor is detected, a step 8 described later is performed.
It is determined whether or not the failure state display flag F set at (1) is set to 1. If the answer is yes,
The fail-safe processing in step 9, for example, the operation of the failure alarm device, is performed, and the process returns to step 1. If the answer to step 1 is negative (No), it is determined in step 2 whether the detected throttle valve opening θ _TH is smaller than a predetermined value θ ₁ shown in FIG. Small values in the normal output value range of the predetermined value theta ₁ is theta _TH sensor, set to a value close to, for example, an idle opening degree. If this answer is negative (No),
Since the failure of the θ _TH sensor 26 cannot be detected by the above-described method, the timer value T of the down-count timer used in steps 5 and 6 described later is set to 0 (step 1).
1) Return to step 1. If the answer to step 2 is affirmative (Yes), step 3
It is determined whether or not the rotational speed ratio e of the torque converter T calculated according to the equation (2) is smaller than a predetermined value 0.9. Here, a predetermined value used for determining the rotation speed ratio e is
The reason why 0.9 is set instead of 1.0 is that even if θ <θ ₁ is satisfied, the throttle valve may be somewhat open between the fully closed state and θ _{1. In} such a case, when cruising is performed, This is because the rotation speed ratio e may be lower than 1.0 (however,> 0.9). If the answer to step 3 is negative (No), step 11 is executed and the process returns to step 1. If the answer to step 3 is affirmative (Yes), step 4
In the detected vehicle speed V is determined whether or not higher than the predetermined value V ₁ shown in Figure 3. The reason for this determination is that even when the throttle valve is almost fully closed, the rotational speed ratio e may be lower than 0.9 when the vehicle speed is considerably low, such as when starting from a stopped state. If the answer to step 4 is negative (No), step 11 is executed and the process returns to step 1. If the answer to step 4 is affirmative (Yes), step 5
To determine whether the timer value T of the timer is 0 or not. If this answer is affirmative (Yes), it means that the abnormality of the θ _TH sensor in steps 2 and 3 has been detected for the first time in the current loop, and the timer value T of the timer is set to T ₀ + T ₁ in step 10. Set and return to step 1. The timer then starts counting down. When the answer to step 5 is negative (No), the timer value T in step 6 whether or not a predetermined value T ₀ is less than, i.e., determines whether a predetermined time T ₁ is passed. This answer is negative (No)
In the case of (1), in order to prevent erroneous detection due to superposition of noise or the like, final failure determination is not performed, and the process returns to step 1. If the answer to step 6 is affirmative (Yes), the θ _TH sensor 2
Assuming that a failure has occurred in 6, the timer value is set to 0 (step 7), the failure state display flag F is set to 1 (step 8), and the fail-safe processing (step 9) is executed. Then, the process returns to step 1. In the above-described embodiment, the case where the engine load sensor is a throttle valve opening sensor has been described. However, the present invention is not limited to this, and an intake pipe absolute pressure sensor (not shown) for detecting the absolute pressure in the intake pipe of the engine E is provided. The present invention can also be applied to detect a failure of the intake pipe absolute pressure sensor when the is used as an engine load sensor. Further, in the above embodiment, the rotation speed ratio of the output shaft rotation speed to the input shaft rotation speed of the fluid torque converter was obtained and used as a parameter representing the rotation speed difference between the two shafts. And may be used as a parameter for control. In this case, when the value of the parameter is larger than the predetermined value, it is determined that a failure has occurred. (Effects of the Invention) As described above, according to the present invention, the magnitude of the load of an internal combustion engine in a vehicle that transmits the output of the internal combustion engine to driving wheels via an automatic transmission including a fluid torque converter is reduced. A method of detecting a failure of a load sensor, wherein an output signal value from the load sensor indicates an engine load equal to or less than a predetermined value, and an output shaft rotation speed of the fluid torque converter is an input shaft rotation speed of the fluid torque converter. If the speed difference is lower than the predetermined value, the load sensor is determined to be faulty, so that the output signal value of the engine load sensor is within a normal value range that does not take an abnormal value. Can be detected, the range of failure detection can be expanded, and the reliability of failure detection can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram of an automatic transmission with a fluid torque converter, FIG. 2 is an overall configuration diagram of a control device of the automatic transmission, FIG.
FIG. 4 is a map showing shift characteristics of the automatic transmission, and FIG. 4 is a flowchart of a failure detection program for a throttle valve opening sensor to which the method of the present invention is applied. E: internal combustion engine, T: fluid torque converter, M
…… Automatic transmission, 24 …… Electronic control unit (ECU), 26 ……
Throttle valve opening sensor (engine load sensor), 27…
... Vehicle speed sensor, 28 ... Engine speed sensor.

Claims (1)

(57) [Claims] A failure detection method of a load sensor for detecting a magnitude of a load of an internal combustion engine in a vehicle that transmits an output of the internal combustion engine to driving wheels via an automatic transmission including a fluid torque converter, the method comprising: When the signal value indicates an engine load equal to or less than a predetermined value, and the output shaft rotation speed of the fluid torque converter is lower than the input shaft rotation speed of the fluid torque converter, and the speed difference is larger than a predetermined value, the load sensor is activated. A failure detection method for a load sensor of an internal combustion engine, which determines that a failure has occurred.