JP2876539B2 - Fail-safe processing method in valve timing switching control of internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to valve timing switching control of an internal combustion engine in which the valve timing of an intake valve and / or an exhaust valve can be switched, and in particular, detects the operating state of the engine in such control. The present invention relates to a fail-safe processing method performed when an abnormality occurs in a valve timing control system such as a sensor that performs a failure.

(Prior art) The valve timing of at least one of the intake valve and the exhaust valve is set to a low speed valve timing (hereinafter referred to as "low speed V / T") suitable for a low rotation region and a high speed valve timing (hereinafter referred to as "high speed") suitable for a high rotation region. For example, a method of switching the valve timing according to the engine speed and the absolute pressure in the intake pipe in an engine that can be switched between V / T and V / T (for example, Japanese Patent Publication No. 49-33289).

On the other hand, a method of determining the amount of fuel to be supplied to the engine based on a basic fuel amount map set in accordance with the engine speed and the intake pipe absolute pressure is also known, and as shown in FIG. When switching between the high-speed V / T region and the low-speed V / T region according to the absolute pressure _{PBA in the} intake pipe, the values on the basic fuel amount map are adjusted so that an optimal air-fuel ratio is obtained for each valve timing. It is also known to set (for example, Japanese Utility Model Application Laid-Open No. 61-157143).

In addition, when an abnormality is detected in a sensor or the like for detecting an operation state of an engine, an abnormality processing method in which the valve timing is fixed at a low speed V / T has already been proposed by the present applicant (Showa 1). (A patent application filed on August 1, 1963).

Further, the switching of the valve timing in the engine to which the above-mentioned conventional control method is applied and the control device thereof is specifically performed as follows. First, the solenoid valve is opened and closed by a command signal from the electronic control unit, and the hydraulic switching valve is opened and closed according to the opening and closing of the solenoid valve. As a result, the hydraulic pressure supplied to the switching mechanism for switching the valve timing changes, and the valve timing is switched between high-speed V / T and low-speed V / T according to the level of the hydraulic pressure.

(Problems to be Solved by the Invention) According to the above-described conventional abnormality processing method, a command signal for switching the valve timing to the low-speed V / T is output from the electronic control unit when an abnormality is detected in the sensor or the like, and is sent to the solenoid valve. Although supplied, a malfunction may occur in the hydraulic switching valve or the switching mechanism, and the actual valve timing may not be switched to the low-speed V / T, but may be a high-speed V / T. In such a case, the engine
Actual valve timing is high-speed V even when in V / T range
The state of / T may occur, causing the following problems. That is, in a relatively high rotational speed region exceeding even example 3,000rpm when the engine rotational speed is lower than a predetermined rotational speed Ne ₁ of FIG. 6, to the actual valve timing as described above is high V / T Regardless, if the fuel amount to be supplied to the engine is determined based on the basic fuel amount suitable for the low-speed V / T, the air-fuel ratio of the mixture becomes lean, and the combustion temperature or the catalyst temperature of the exhaust gas purification device rises (for example, 1,000 Temperature rise of more than ° C). In this case, problems such as melting of the spark plug, knocking at a high speed, and deterioration of the durability of the catalyst due to preignition occur.

Such a problem becomes more conspicuous in an operating state where the engine speed is high and the load is high.

The present invention has been made to solve the above problems, even when detecting an abnormality in the valve timing control system including a sensor for detecting the operating state of the engine,
By properly controlling the air-fuel ratio of the mixture supplied to the engine,
An internal combustion engine that can prevent the combustion temperature or the catalyst temperature of the exhaust gas purification device from excessively rising, and solve problems such as melting of the spark plug due to preignition, knocking at high speed, and deterioration of catalyst durability. It is an object of the present invention to provide a fail-safe processing method in the valve timing switching control.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a valve timing of at least one of an intake valve and an exhaust valve which is a low speed valve timing suitable for a low rotation region and a high speed valve timing suitable for a high rotation region. In the fail-safe processing method in the valve timing switching control of switching the valve timing by outputting a command signal from the electronic control unit of the electronically controlled internal combustion engine that can be switched between the normal and the normal, the basic for normal use used when the valve timing control system is normal A fail-safe basic fuel amount map set relatively rich in the predetermined operation region with respect to the set value of the fuel amount map is provided, and when an abnormality of the valve timing control system is detected, the engine is operated in a low rotation region. And low-speed valve timing regardless of whether When the engine speed is higher than the predetermined speed while the command signal is being output, fuel is supplied to the engine based on the value read from the fail-safe basic fuel amount map. It is intended to be supplied.

Further, instead of the engine speed, when the engine load is higher than a predetermined value, fuel may be supplied to the engine based on the value read from the fail-safe basic fuel map.

Incidentally, the switching of the valve timing referred to in this specification means
This refers to switching both or one of the valve opening period and the valve lift amount.

Embodiment An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of a control device to which the control method of the present invention is applied. In FIG. 1, reference numeral 1 denotes a DOHC in-line four-cylinder engine in which each cylinder is provided with a pair of an intake valve and an exhaust valve. is there.

In the middle of the intake pipe 2 of the engine 1, a throttle body 3
And a throttle valve 3 ′ is disposed therein. Throttle valve opening (θth)
A sensor 4 is connected, and outputs an electric signal corresponding to the opening degree of the throttle valve 3 and supplies it to an electronic control unit (hereinafter referred to as “ECU”) 5.

The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3 and slightly upstream of the intake valve (not shown) of the intake pipe 2, and each injection valve is connected to a fuel pump (not shown). Is electrically connected to ECU5 together with the EC
The valve opening time of fuel injection is controlled by a signal from U5.

An ignition plug 22 provided for each cylinder of the engine 1 is connected to the ECU 5 via a drive circuit 21, and the ECU 5 controls the ignition timing θig of the ignition plug 22.

An electromagnetic valve 23 for performing valve timing switching control described later is connected to the output side of the ECU 5, and the opening and closing operation of the electromagnetic valve 23 is controlled by the ECU 5.

On the other hand, an absolute pressure (P _BA ) sensor 8 in the intake pipe is provided immediately downstream of the throttle valve 3 via a pipe 7, and the absolute pressure signal converted into an electric signal by the absolute pressure sensor 8 is sent to the ECU 5. Supplied. Further, the downstream mounted an intake air temperature (T _A) sensor 9 is supplied to the ECU5 outputs an electric signal indicative of the sensed intake air temperature T _A.

The engine water temperature (Tw) sensor 10 mounted on the main body of the engine 1 is composed of a thermistor or the like, detects the engine water temperature (cooling water temperature) Tw, outputs a corresponding temperature signal, and supplies it to the ECU 5. The engine speed (Ne) sensor 11 and the cylinder discrimination (CYL) sensor 12 are mounted around the camshaft or the crankshaft of the engine 1. Engine speed sensor 11
Outputs a pulse (hereinafter referred to as a “TDC signal pulse”) at a predetermined crank angle position every time the crankshaft of the engine 1 rotates 180 degrees, and the cylinder discriminating sensor 12 outputs a signal pulse at a predetermined crank angle position of a specific cylinder. Output
Each of these signal pulses is supplied to the ECU 5.

The three-way catalyst 14 is disposed in the exhaust pipe 13 of the engine 1 and purifies components such as HC, CO, and NOx in the exhaust gas. O ₂ sensor 15 as an exhaust gas concentration detector outputs a three-way catalyst 14 is mounted on the upstream side of the signal corresponding to the detected value by detecting the oxygen concentration in the exhaust gas in the exhaust pipe 13 ECU 5 To supply.

The ECU 5 further includes a vehicle speed sensor 16, a gear position sensor 17 for detecting a shift position of the transmission, and a hydraulic pressure sensor 1 for detecting a hydraulic pressure in an oil supply passage (88i, 88e in FIG. 2) of the engine 1, which will be described later.
8. A catalyst temperature sensor 19 for detecting the temperature (T _CAT ) of the three-way catalyst 14 and a spark plug temperature sensor 20 for detecting the temperature (T _PLG ) of the spark plug 22 are connected, and detection signals of these sensors are provided. Is supplied to the ECU5.

The ECU 5 shapes input signal waveforms from various sensors, corrects a voltage level to a predetermined level, and converts an analog signal value to a digital signal value. The input circuit 5a has a function of a central processing unit (hereinafter referred to as a “CPU”). 5b, a storage means 5c for storing various calculation programs executed by the CPU 5b, calculation results, and the like, an output circuit 5d for supplying drive signals to the fuel injection valve 6, the drive circuit 21, and the solenoid valve 23, and the like. .

Based on the various engine parameter signals described above, the CPU 5b determines various engine operation states such as a feedback control operation area and an open loop control operation area corresponding to the oxygen concentration in the exhaust gas, and determines the next according to the engine operation state. Based on the equation (1), a fuel injection time _TOUT of the fuel injection valve 6 synchronized with the TDC signal pulse is calculated.

T _OUT = Ti × K ₁ + K ₂ (1) where Ti is the basic fuel amount, specifically the engine speed
This is a basic fuel injection time determined according to Ne and the intake pipe absolute pressure _PBA.As a Ti map for determining this Ti value, a normal Ti _NL map used when the engine control system is normal is used. The failsafe _TiFS map used when an abnormality is detected is stored in the storage unit 5c.
The _TiNL map for normal uses a value suitable for low-speed valve timing in the operation region where the valve timing is low, and a value suitable for high-speed valve timing in the operation region where the valve timing is high. The fail-safe Ti _FS map is set in a predetermined operation region (for example, an operation region in which the valve timing is a low-speed valve timing, and the engine speed Ne is 3,000 rpm) with respect to the set value of the normal Ti _NL map. Higher region), it is set to a relatively rich value.

K _FS is a fail-safe enrichment correction coefficient calculated by a method shown in FIG. 7 described later.

K ₁ and K ₂ is a correction coefficient and correction variable computed according to various engine parameter signals, predetermined as fuel consumption characteristic according to engine operating conditions, the optimization of various properties such as the engine acceleration characteristics can be achieved Determined by the value.

CPU5b further absolute intake pipe and engine rotational speed Ne pressure P _BA
The ignition timing θig is determined accordingly.

The CPU 5b controls the opening and closing of the solenoid valve 23 by outputting a valve timing switching instruction signal by a method shown in FIG.

The CPU 5b outputs a signal for driving the fuel injection valve 6, the drive circuit 21, and the solenoid valve 23 via the output circuit 5d based on the result calculated and determined as described above.

FIG. 2 is a longitudinal sectional view of a main part of the engine 1, in which four cylinders 32 are provided in a cylinder block 31 in series, and a cylinder head 33 connected to an upper end of the cylinder block 31; A combustion chamber 35 is defined between the piston 34 and the piston 34 that is slidably fitted in the combustion chamber 35. In the cylinder head 33, a pair of intake ports 36 and a pair of exhaust ports 37 are provided at portions forming the ceiling surface of each combustion chamber 35, and each of the intake ports 36 is opened on one side of the cylinder head 33. Each exhaust port 37 is connected to an exhaust port 39 opened on the other side surface of the cylinder head 33.

In order to guide a pair of intake valves 40i that can open and close each intake port 36 and a pair of exhaust valves 40e that can open and close each exhaust port 37, a portion corresponding to each cylinder 32 of the cylinder head 33,
The guide tubes 41i, 41e are fitted and fixed respectively, and the intake valves 40i projecting upward from the guide tubes 41i, 41e.
And a flange portion 42 attached to the upper end of each exhaust valve 40e.
Valve springs 43i and 43e are respectively contracted between i and 42e and the cylinder head 33, and the intake valves 40i and the exhaust valves 40e are attached upward, that is, in the valve closing direction by the valve springs 43i and 43e. It is being rushed.

A working chamber 45 is defined between the cylinder head 33 and a head cover 44 coupled to the upper end of the cylinder head 33. In the working chamber 45, an intake valve for each cylinder 32 is provided.
An intake valve side valve drive 47i for opening and closing the 40i and an exhaust valve side valve drive 47e for opening and closing the exhaust valve 40e in each cylinder 32 are housed and arranged. Double valve unit 47
i, 47e have basically the same configuration,
In the following description, the intake valve-side valve operating device 47i will be described with reference numerals added with a suffix i, and the exhaust valve-side valve operating device 17e will only be illustrated with a reference numeral added with a suffix e.

Referring also to FIG. 3, the intake valve-side valve operating device 47i includes:
A camshaft 48i that is driven to rotate at a half speed ratio from a crankshaft (not shown) of the engine, and a high-speed cam 51i provided on the camshaft 48i corresponding to each cylinder 32
And low-speed cams 49i and 50i (low-speed cams 50i are low-speed cams
49i, which is substantially the same shape as the high-speed cam 51i and is positioned on the opposite side of the low-speed cam 49i).
And a rocker shaft 52i fixedly disposed in parallel with the first and second drive rocker arms 53i, 54i and a free rocker arm 55i pivotally supported by the rocker shaft 52i corresponding to the cylinders 32, respectively. A connection switching mechanism 56i is provided between the corresponding rocker arms 53i, 54i, 55i.

In FIG. 3, a connection switching mechanism 56i includes a first switching pin 81 capable of connecting the first drive rocker arm 53i and the free rocker arm 55i, and a second switching pin capable of connecting the free rocker arm 55i and the second drive rocker arm 54i. 82 and the first
And a regulating pin 83 for regulating the movement of the second switching pins 81 and 82.
And a return spring 84 for urging each of the pins 81 to 83 toward the connection release side.

The first drive rocker arm 53i has a free rocker arm 55i.
The first guide hole 85 with the bottom opened to the side is the rocker shaft 52.
The first guide hole 85 is
The switching pin 81 is slidably fitted, and a hydraulic chamber 86 is defined between one end of the first switching pin 81 and the closed end of the first guide hole 85. Further, a passage 87 communicating with the hydraulic chamber 86 is formed in the first drive rocker arm 53i, and an oil supply passage 88i is provided in the rocker shaft 52i. The oil supply passage 88i is connected to the first drive rocker arm 53i.
Irrespective of the swing state of 53i, it is always in communication with the hydraulic chamber 86 via the passage 87.

A guide hole 89 corresponding to the first guide hole 85 is formed in the free rocker arm 55i in parallel with the rocker shaft 52i between both side surfaces, and one end of the first switch pin 81 is in contact with the other end. The second switching pin 82 is slidably fitted in the guide hole 89.

A second guide hole 90 having a bottom corresponding to the guide hole 89 is formed in the second drive rocker arm 54i so as to open to the free rocker arm 55i side and to be bored in parallel with the rocker shaft 52i. Disc-shaped regulating pin abutting on the other end
83 is slidably fitted in the second guide hole 90. In addition, the guide cylinder 91 is fitted to the closed end of the second guide hole 90,
A shaft portion 92 slidably fitted in the guide tube 91 is a regulating pin.
It protrudes coaxially and integrally with 82. The return spring 84 is inserted between the guide cylinder 91 and the regulating pin 83, and the pins 81, 82, 83 are urged toward the hydraulic chamber 86 by the return spring 84.

In the connection switching mechanism 56i, when the hydraulic pressure in the hydraulic chamber 86 is increased, the first switching pin 81 is fitted into the guide hole 89 and the second switching pin 82 is fitted into the second guide hole 90. The rocker arms 53i, 55i, 54i are connected. When the oil pressure in the hydraulic chamber 86 becomes low, the first switching pin 81 returns to a position where the contact surface with the second switching pin 82 corresponds to the position between the first drive rocker arm 53i and the free rocker arm 55i by the spring force of the return spring 84, Since the second switching pin 82 returns to the position corresponding to the contact surface with the restriction pin 83 between the free rocker arm 55i and the second drive rocker arm 54i, each rocker arm 53i, 55i,
The connected state of 54i is released.

Next, an oil supply system to the two-way valve devices 47i and 47e will be described with reference to FIG. 4. An oil gallery 98, 98 'is provided to an oil pump (not shown) for raising oil from an oil pan (not shown). And oil pressure is supplied from the oil gallery 98, 98 'to each of the connection switching mechanisms 56i, 56e.
Lubricating oil is supplied to each lubricating part of the valve gear 47i, 47e.

The oil gallery 98 is connected to a switching valve 99 for switching the oil pressure between high and low and supplying the oil. The oil supply passages 88i and 88e in each rocker shaft 52i and 52e are connected to the oil gallery 98 via the switching valve 99. Connected to 98.

Passage forming members 102i, 102e extending parallel to the two camshafts 48i, 48e are fastened to the upper surface of each cam holder 59 by a plurality of bolts. Each passage forming member 10
2i and 102e have low-speed lubricating oil passages 104i and 104e
And the high-speed lubricating oil passages 105i and 105e are provided in parallel with each other, the low-speed lubricating oil passages 104i and 104e are provided in the oil gallery 98 ', and the high-speed lubricating oil passages 105i and 105e are provided in the lubricating passage. Connected to 88i and 88e, respectively. In addition, lubricating oil passage 104 for low speed
i, 104e are connected to the cam holder 59.

The switching valve 99 has an inlet port 119 communicating with the oil gallery 98 and an outlet port 120 communicating with the oil supply passages 88i and 88e, and is mounted on one end surface of the cylinder head 3.
A spool valve 122 is slidably fitted into the inside of the 121.

A cylinder hole 124 whose upper end is closed by a cap 123 is formed in the housing 121.
An operating hydraulic chamber 125 is formed between the cylinder and the cap 123 so as to be slidably fitted in the cylinder hole 124. Moreover, the housing 121
Spring chamber 126 formed between the lower part of
Accommodates a spring 127 that biases the spool valve body 122 upward, that is, in the closing direction. The spool valve element 122 has an annular recess that allows communication between the inlet port 119 and the outlet port 120.
When the spool valve element 122 is moving upward as shown in FIG. 4, the spool valve element 122 is in a state of shutting off between the inlet port 119 and the outlet port 120.

With the housing 121 attached to the end face of the cylinder head 33, an oil filter 129 is sandwiched between the inlet port 119 and the high-speed hydraulic supply passage 116. Further, an orifice hole 131 communicating between the inlet port 119 and the outlet port 120 is formed in the housing 121. Therefore, with the spool valve body 122 in the closed position, the inlet port 119 and the outlet port 120
The orifices 131 communicate with each other through an orifice hole 131.
88i, 88e.

The housing 121 is provided with a bypass port 132 that communicates with the outlet port 120 via the annular recess 128 only when the spool valve element 122 is in the closed position, and the bypass port 132 communicates with the upper portion in the cylinder head 33. .

The housing 121 is connected to a conduit 135 that is always in communication with the inlet port 119, and the conduit 135 is connected to the conduit 137 via the electromagnetic valve 23. Moreover, the pipe 137 is a cap 12
It is connected to the connection hole 138 drilled in 3. Therefore, when the solenoid valve 23 opens, hydraulic pressure is supplied to the operating hydraulic chamber 125, and the spool valve body 122 is driven in the valve opening direction by the hydraulic pressure of the hydraulic pressure introduced into the operating hydraulic chamber 125.

Further, the housing 121 has an outlet port 120, that is, an oil supply passage.
A hydraulic pressure sensor 18 for detecting the hydraulic pressure of 88i, 88e is attached, and this hydraulic pressure sensor 18 has a function of detecting whether the switching valve 99 is operating normally.

The valve train 47i, 47 of the engine 1 configured as described above.
The operation of e will be described below. Here, each valve train 47i
And 47e operate in the same manner, so the intake valve side valve train 47i
Only the operation of will be described.

When the ECU 5 outputs a valve opening command signal to the electromagnetic valve 23, the electromagnetic valve 23 opens, the switching valve 99 opens, and the oil pressure in the oil supply passage 88i increases. As a result, the connection switching mechanism 5
6i is operated to connect the respective rocker arms 53i, 54i, 55i, and the high-speed cam 51i causes the respective rocker arms 53i, 54i, 54i.
i and 55i operate integrally, and the pair of intake valves 40i open and close at a high-speed valve timing in which the valve opening period and the lift amount are relatively large.

On the other hand, when a valve closing command signal is output from the ECU 5 to the solenoid valve 23, the solenoid valve 23 and the switching valve 99 are closed, and the oil supply passage 88 is closed.
The oil pressure of i decreases. As a result, the connection switching mechanism 56i operates in the opposite direction to the above, the connection state of each rocker arm 53i, 54i, 55i is released, and the corresponding rocker arms 53i, 54i are operated by the low-speed cams 49i, 50i, respectively, and a pair of Intake valve 40i,
It operates at a low valve timing in which the valve opening period and the lift amount are relatively small.

Next, the valve timing switching control according to the present invention will be described in detail below.

FIG. 5 shows a flowchart of a program for controlling switching of valve timing by the ECU 5, that is, an output control program of a signal output to the solenoid valve 23. This program is executed in synchronization with each TDC signal pulse generation.

In step 501, it is determined whether signals are normally input from the various sensors to the ECU 5, or whether an abnormality has already occurred in another control system, that is, whether to fail-safe.

Specifically, an intake pipe absolute pressure (P _BA ) sensor 8, a cylinder discrimination (CYL) sensor 12, an engine speed (TDC) sensor 11,
Abnormal output from the engine water temperature sensor 10 and vehicle speed sensor 16, abnormal ignition timing control signal output and abnormal fuel injection control output, abnormal current flowing through the valve timing control solenoid valve 23, valve timing control solenoid valve 23 An abnormality such as that a normal oil pressure change of the outlet port 120 according to the opening / closing of the outlet port 120 cannot be confirmed even after a predetermined time has elapsed by the oil pressure switch in the oil pressure sensor 18 is detected, and it is determined that the engine is in the fail-safe operating state. When one of the cylinder discrimination (CYL) sensor and the TDC sensor has an abnormality, the other output is used in place of the one output.

When the answer to step 501 is affirmative (YES), that is, when fail-safe is to be performed, the process proceeds to step 532 described below, and negative (NO)
In the case of, a normal _TiNL map is selected (step 534), and the routine proceeds to step 502.

502 is a step of determining whether or not the engine is starting based on Ne or the like, 5
03 is a step for judging whether or not the remaining time t _ST of the delay timer has become 0, and sets t _ST to a predetermined time (for example, 5 seconds) during the start (step 504), and starts the timing operation after the start. I did it. 505 is a step for determining whether or not the engine coolant temperature Tw is lower than a set temperature Tw ₁ (for example, 60 ° C.), that is, whether or not warm-up has been completed; 506 is a set vehicle speed V _{1 at which the} vehicle speed V is extremely low (with hysteresis) For example 8km / 5k
m) a step of determining whether the engine is lower than a vehicle, 507 a step of determining whether or not the engine-equipped vehicle is a manual vehicle (MT), and 508 a shift lever in a parking (P) range when the vehicle is an automatic vehicle (AT). 509 is a step for determining whether or not Ne is in a neutral (N) range, and 509 is a step for determining whether or not Ne is equal to or greater than a predetermined lower limit Ne ₁ (for example, 4,800 rpm). Is affirmative (YES)), during start-up (the answer in step 502 is affirmative (YES)), after the start, before the elapse of the delay timer set time t _ST (the answer in step 503 is affirmative (YES)), and during warm-up (step 505). Is affirmative (YES), while the vehicle is stopped or running slowly (step
When the answer of 506 is affirmative (YES), the range is P and N (the answer of step 508 is affirmative (YES)), and when Ne <Ne ₁ (the answer of step 509 is negative (NO)), which will be described later. The solenoid valve 23 is closed to maintain the valve timing at the low-speed valve timing.

When it is determined in step 509 that Ne ≧ Ne ₁ is satisfied, the process proceeds to step 513 and Ne is set to the predetermined upper limit value Ne ₂ (for example,
(5,900 rpm). The answer to step 513 is negative (NO), i.e. Ne <when Ne ₂ is satisfied, the process proceeds to step 514, the intake pipe absolute pressure P _BA is the engine speed
Based on Ne, it is determined whether or not it is equal to or greater than a determination value calculated by the following equation (2).

Discrimination value = A × Ne + B (2) Here, A and B are determined as follows by the predetermined lower limit value Ne ₁ , the predetermined upper limit value Ne ₂ and the predetermined pressures P _B1 and P _B2 shown in FIG. Is a constant.

A = (P _B1 −P _B2 ) / (Ne ₁ −Ne ₂ ) B = (Ne ₁ × P _B2 −Ne ₂ × P _B1 ) / (Ne ₁ −Ne ₂ ) That is, it is calculated by the equation (2). The discrimination value is Ne _{1 in} FIG.
A P _BA value on the straight line I in the range of ≦ Ne <Ne _2.

Note that the determinations in steps 509, 513, and 514 are provided with hysteresis as indicated by the solid line and the broken line in FIG.

The answer to step 514 is negative (NO), that is, P _BA <A × Ne + B
Is satisfied, it is determined whether or not the timer value t _VTOFF of the delay timer set in step 515 described later is zero (step 516). If the answer is affirmative (YES), the solenoid valve 23 is closed in step 517. A valve command, that is, a command to switch to low-speed valve timing is issued. Also, T _OUT ≧ T _VT , Ne ≧ Ne ₂ , P _BA
If any of ≧ A × Ne + B is satisfied, the timer value of the solenoid valve opening delay timer is set to t _VTOFF (for example, 3
(Seconds) and starts (step 515), and in step 518, a command to open the solenoid valve 23, that is, a command to switch to high-speed valve timing is issued.

When the valve closing command is issued in step 517, it is determined in step 519 whether or not the hydraulic switch in the hydraulic sensor 18 has been turned on, that is, whether or not the hydraulic pressure in the oil supply passages 88i and 88e has become low. When the answer is affirmative (YES), that is, when the hydraulic switch is turned on, it is determined in step 521 whether or not the remaining time t _LVT of the low speed valve timing switching delay timer has become zero. When the answer to step 521 is affirmative (YES), that is, when t _LVT = 0, at step 523, the remaining time t _HVT of the high-speed valve timing switching delay timer is set to a set time (for example, 0.1 second). Reburimitta value N _HFC in each it as Ti map and ignition timing map for use in injection control routine of the fuel is performed a process of selecting the Ti _L map and the low-speed valve timing for ignition timing map (? ig _L map), in subsequent step 527 _{Is set} to the value _NHFC1 for low-speed valve timing.

The above-mentioned rev limiter value N _HFC is for preventing fuel overrun when the engine speed Ne is equal to or higher than the rev limiter value N _HFC , and considering the load acting on the timing belt, The rev limiter value is set to a relatively low value N _HFC1 (for example, 7500 rpm) at low speed valve timing and a relatively high value N _HFC1 (for example, 8100 rpm) at high speed valve timing.

On the other hand, when the valve opening command is issued in step 518, it is determined in step 520 whether or not the hydraulic switch in the hydraulic sensor 18 has been turned off, that is, whether or not the hydraulic pressure in the oil supply passages 88i and 88e has become high. When the answer is affirmative (YES), that is, when the hydraulic switch is turned off, it is determined in step 522 whether or not the remaining time t _HVT of the high-speed valve timing switching delay timer has become zero. Step 522 is positive (YE
S), that is, when t _HVT = 0, at step 524 the remaining time t _LVT of the low-speed valve timing switching delay timer
To the set time (for example, 0.2 seconds), and follow step 5
28 performs processing for the N _HFC value N _HFC2 for high-speed valve timing.

By the way, both switching delay timers t _HVT and t _LVT described above
Is the response delay from when the solenoid valve 23 is opened and closed to when the switching valve 99 is switched, the oil pressure in the oil supply passages 88i and 88e changes, and the switching operation of the connection switching mechanisms 56i and 56e of all cylinders is completed. The program is set in accordance with the time, and when the solenoid valve 23 is switched from open to closed, the program proceeds in the order of 519 → 522 → 524 → 528 until the hydraulic switch in the hydraulic sensor 18 is turned on. Until the connection switching mechanisms 56i and 56e of all cylinders are switched to the low-speed valve timing side, 519 → 521 → 528
The switching valve 99 does not switch to the closing side even if a valve closing command is issued due to failure of the solenoid valve 23 or the switching valve 99, etc., even when the hydraulic switch in the hydraulic sensor 18 does not turn on forever. In the same manner as above, proceed in the order of 519 → 522 → 524 → 528, and as long as the connection switching mechanisms 56i, 56e of all cylinders are not switched to the low-speed valve timing side, the fuel injection control is adapted to the high-speed valve timing. Will be maintained. Solenoid valve 23
In the same manner as above, when switching from the closed state to the open state, unless the connection switching mechanisms 56i, 56e of all the cylinders are switched to the high-speed valve timing side, the fuel injection control is maintained at the low-speed valve timing. Is done.

On the other hand, the answer in step 502 is affirmative (YES), or the answer in step 503 is negative (NO), or
When the answer to 06 is affirmative (YES), that is, during the start and before the elapse of the set time after the start, during the warm-up, during the stop, or during the slow running, the process proceeds to step 529 and issues a command to close the solenoid valve 23,
From step 529, proceed in the order of 523 → 527. Step 508
Also, the step time N, in the case of P-range, the process proceeds to step 530 to determine whether or not the engine operating condition was in the high-speed valve timing region in the last loop, and the Ne <Ne ₁ is satisfied in step 509 in Proceed to 530. If the answer to step 530 is affirmative (YES), that is, if it was in the high-speed valve timing area in the previous loop, the timer value t _VTOFF of the solenoid valve opening delay timer is set to zero (step 531). If the answer to step 530 is negative (NO), that is, if the previous time was in the low speed valve timing region, in other words, if the connection switching mechanisms 56i, 56e of all cylinders have not been switched to the high speed valve timing side, In the same manner as described above, the process proceeds in the order of 529 → 523 → 527, and the fuel injection control suitable for the low-speed valve timing is performed irrespective of the hydraulic switch in the hydraulic pressure sensor 18. This is a countermeasure when the hydraulic switch in the hydraulic sensor 18 is kept off due to disconnection or the like.

By the way, the above-mentioned N _HFC1 is set higher than Ne ₂ , and usually, the valve timing is switched to the high-speed valve timing before Ne rises to N _HFC1, and the value of N _HFC becomes N
_{Since the mode} is switched to _HFC2 , the fuel cut at _NHFC1 is not performed. In contrast, steps 502 to 508
In the operation state proceeds to 529, for Ne by racing and the like are held in the low-speed valve timing even exceed the Ne _2, N _HFC1
The fuel cut is performed. Also, even if the low-speed valve timing is switched to the high-speed valve timing, the fuel cut by the _{NHFC 1} is performed until t _HVT becomes 0, that is, until the coupling mechanisms 56i and 56e are actually switched to the high-speed valve timing. .

On the other hand, when the answer to step 501 is affirmative (YES), that is, when the fail-safe operation is being performed, a command to close the solenoid valve 23 is issued (step 532), and fail-safe processing described later is executed (step 533). Proceed to 527.

FIG. 7 shows an embodiment of the fail-safe process in step 933. In the first embodiment ((a) in the figure), the engine speed Ne is equal to the map selection predetermined speed Ne _FS (for example, 3,00
When the engine speed is higher than 0 rpm), a fail-safe Ti _FS map is selected, and when the engine speed Ne is equal to or lower than the predetermined speed Ne _FS , a normal Ti _NL map is selected.

As described above, the value of the fail-safe Ti _FS map is set to be relatively rich with respect to the value of the normal Ti _NL map. Therefore, according to the method of FIG. In spite of outputting a valve closing command to the solenoid valve 23 during the fail-safe, the switching valve 99 or the coupling switching mechanism 56i, 56e, etc., fails and the actual valve timing becomes the high-speed valve timing. Even in such a case, the air-fuel ratio of the air-fuel mixture becomes lean and prevents the combustion temperature or the catalyst temperature in the exhaust gas purification device from rising excessively, and the ignition plug can be damaged due to pre-ignition. Problems such as knocking during rotation and deterioration of the durability of the catalyst can be prevented.

Further, since the problem is likely also occurs during high-load high intake pipe absolute pressure P _BA, FIG. 7 (b) intake manifold as shown in the absolute pressure P _BA office for the map selection pressure P _BFS (e.g. 650mmH
g) When it is higher, a fail-safe Ti _FS map is selected, and when the intake pipe absolute pressure P _BA is equal to or lower than the predetermined pressure P _BFS , a normal Ti _NL map is selected.

Further, in the modified example shown in FIG. 3C, the engine speed Ne is higher than the predetermined speed Ne _FS (Ne> Ne _FS ), and the intake pipe absolute pressure P _BA is higher than the predetermined pressure P _BFS (P _BA). > P _BFS ) In some cases, select a Ti _FS map for failsafe and set Ne ≦
When Ne _FS or P _BA ≦ P _BFS holds, T for normal
i Select the _NL map.

In the modification shown in FIG. _3D , the catalyst temperature T _CAT of the exhaust gas purification device is detected, and the catalyst temperature T _CAT is set to a predetermined catalyst temperature T _{CAT.
If the} temperature is higher than _CATFS (for example, 1,000 ° C) (T _CAT > T _CATFS ), select a fail-safe Ti _FS map and set T _CAT ≤
When T _CATFS is established, a normal Ti _NL map is selected.

Further, in the modified example of FIG.
_PLG is detected and the plug temperature T _PLG is _equal to the specified plug temperature P _PLGFS
(T _PLG > P _PLGFS )
Select the Ti _FS map for fail-safe and set T _{PLG ≤P PLGFS}
Is satisfied, a normal Ti _NL map is selected.

(Effects of the Invention) As described in detail above, the present invention can switch at least one of the intake valve timing and the exhaust valve timing between a low-speed valve timing suitable for a low rotation region and a high-speed valve timing suitable for a high rotation region. In a fail-safe processing method in a valve timing switching control for switching a valve timing by outputting a command signal from an electronic control unit of a simple electronically controlled internal combustion engine, a normal basic fuel amount map used when a valve timing control system is normal is used. A fail-safe basic fuel amount map set relatively rich in the predetermined operation region with respect to the set value is provided, and when an abnormality of the valve timing control system is detected, the engine is operated in the low rotation region and the high rotation region. Command signal for setting the valve timing to the low-speed valve timing regardless of When the command signal is output and the engine speed is higher than a predetermined speed while the command signal is being output, fuel is supplied to the engine based on the value read from the fail-safe basic fuel amount map. Even when an abnormality of a valve timing control system including a sensor for detecting an operation state of the engine is detected, the air-fuel ratio of the air-fuel mixture supplied to the engine is appropriately controlled, and the combustion temperature or the catalyst temperature of the exhaust gas purifying device is detected. Is prevented from rising excessively, and problems such as melting of the spark plug due to preignition, knocking at high speed, deterioration of catalyst durability, and the like can be solved.

Further, as described in claim 2, when the engine load is higher than a predetermined load instead of the engine speed, fuel is supplied to the engine based on a value read from the fail-safe basic fuel map. However, the same effect as described above can be obtained.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an engine and a control device to which a fail-safe processing method of the present invention is applied, FIG. 2 is a longitudinal sectional view of a main part of the engine, FIG.
FIG. 4 is a diagram showing a refueling system and a hydraulic pressure switching device, FIG. 5 is a flowchart of a valve timing switching control routine, FIG. 6 is a diagram showing valve timing switching characteristics, and FIG. It is a flowchart. 1 ... internal combustion engine, 5 ... electronic control unit (ECU), 6 ... fuel injection valve, 11 ... engine speed sensor, 23 ... solenoid valve, 40i ... intake valve, 40e ... exhaust valve,
47i, 47e: Valve operating device, 88i, 88e: Oil supply path, 99: Switching valve.

Continuation of front page (56) References JP-A-60-150409 (JP, A) JP-A-52-153030 (JP, A) JP-A-52-25931 (JP, A) JP-A-59-12108 (JP) , A) JP-A-59-70842 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41 / 22,43 / 00 F02D 13/02 F01L 1/34

Claims (2)

(57) [Claims] An electronic control of an electronically controlled internal combustion engine in which at least one of an intake valve and an exhaust valve can be switched between a low-speed valve timing suitable for a low-speed region and a high-speed valve timing suitable for a high-speed region. In the fail-safe processing method in the valve timing switching control in which a command signal is output from the unit to switch the valve timing, a relative value in a predetermined operation region with respect to a set value of a normal basic fuel amount map used when the valve timing control system is normal. A basic fuel amount map for fail-safe is set on the rich side, and when an abnormality of the valve timing control system is detected, the valve timing is controlled regardless of whether the engine is in the low rotation region or the high rotation region. At the same time as the low-speed valve timing. Valve timing switching control for an internal combustion engine, wherein fuel is supplied to the engine based on a value read from the fail-safe basic fuel amount map when the engine speed is higher than a predetermined speed while the engine is being powered Fail-safe processing method. 2. An electronic control of an electronically controlled internal combustion engine in which at least one of an intake valve and an exhaust valve can be switched between a low-speed valve timing suitable for a low-speed region and a high-speed valve timing suitable for a high-speed region. In the fail-safe processing method in the valve timing switching control in which a command signal is output from the unit to switch the valve timing, a relative value in a predetermined operation region with respect to a set value of a normal basic fuel amount map used when the valve timing control system is normal. A basic fuel amount map for fail-safe is set on the rich side, and when an abnormality of the valve timing control system is detected, the valve timing is controlled regardless of whether the engine is in the low rotation region or the high rotation region. At the same time as the low-speed valve timing. When the engine load is higher than a predetermined load in a powered state, fuel is supplied to the engine based on a value read from the fail-safe basic fuel amount map. Safe processing method.