JP2001065374A - Engine valve timing control device - Google Patents

Abstract

(57) [Problem] To provide a valve timing control device capable of preventing deterioration of combustion of an engine and securing necessary minimum traveling performance even when a water temperature sensor system fails. SOLUTION: In an engine with a variable valve timing mechanism, a valve timing control device for setting a target valve timing VTTTGT based on at least a detection value of a cooling water temperature sensor, wherein an output value from the water temperature sensor is out of a specified value. When an abnormality in the water temperature sensor system is detected (FNGTW = 1), the target valve timing VTTTGT
Is set to the most retarded angle (step S22). This allows
Even in the case where the engine warm-up state cannot be detected, fail-safe control is performed to secure the necessary minimum traveling performance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve timing control device for an engine having a variable valve timing mechanism for changing at least one of an intake valve and an exhaust valve of an engine in accordance with an operating state of the engine. The present invention relates to an engine valve timing control device that controls valve timing based at least on engine temperature and performs fail-safe control of the engine when an engine temperature detection system is abnormal.

[0002]

2. Description of the Related Art In recent years, as disclosed in Japanese Patent Application Laid-Open No. Hei 8-109840, transmission means for transmitting rotation of a crankshaft of an engine to a camshaft of a cam for opening and closing an intake valve or an exhaust valve includes: By interposing a variable valve timing mechanism that adjusts the rotation phase between the crankshaft and the cam, and controlling the variable valve timing mechanism based on the operating state of the engine, at least the intake valve and the exhaust valve according to the engine operating state An engine with a variable valve timing mechanism for continuously changing one valve opening / closing timing has been put to practical use.

In such valve timing control of an engine, a target value (target valve timing) VTTTGT of a rotation phase is first set based on the operating state of the engine. Next, this target valve timing VTTTGT,
Actual valve timing VT indicating actual valve timing
Is calculated. Further, according to the difference between the two, the oil flow control valve OCV of the variable valve timing mechanism VVT is controlled.
Set the control amount for. Then, feedback control is performed so that the actual valve timing VT converges to the target valve timing VTTGT suitable for the engine operating state.

However, the target valve timing VTTG
T gives a valve timing suitable for the engine state at the time of completion of engine warm-up, so that a valve timing suitable for a cold engine state cannot be obtained, and the combustion state of the engine deteriorates. That is, when the engine temperature is low, especially at a light load where the effective compression ratio of the engine is small, the combustion may be deteriorated, and a problem such as an unstable engine rotation may occur.

In order to prevent the deterioration of the combustion state when the engine is cold, Japanese Patent Application Laid-Open No. 5-156972 discloses an internal combustion engine in which the control range of the valve opening / closing timing becomes narrower as the engine temperature becomes lower. A valve timing control device has been proposed. Here, an upper limit value and a lower limit value are set for the target valve timing based on the engine coolant temperature Tw, and the target valve timing is regulated in accordance with the engine coolant temperature by these target values. As a result, the pumping loss when the engine is cold is reduced as much as possible, and the effective compression ratio is suppressed from being reduced more than necessary to prevent deterioration of combustion in a light load region.

[0006]

However, even in such a valve timing control device considering the engine temperature, once the engine temperature detection system fails, control based on the engine temperature cannot be executed.
That is, when the water temperature sensor system becomes abnormal due to disconnection or short-circuit of the water temperature sensor itself or the harness between the water temperature sensor and the electronic control unit, the engine cooling water temperature T
w cannot be detected. Therefore, the upper limit value and the lower limit value for the target valve timing VTTGT set based on the water temperature Tw are erroneously set, so that the target valve timing cannot be properly controlled according to the engine temperature, and the engine combustion deteriorates. was there.

In view of the above circumstances, the present invention performs fail-safe control to prevent engine combustion from deteriorating, stabilize engine behavior, and reduce engine output even when the engine warm-up state cannot be detected. It is an object of the present invention to provide a valve timing control device for an engine with a variable valve timing mechanism capable of suppressing the driving performance and ensuring a necessary minimum traveling performance.

[0008]

According to a first aspect of the present invention, there is provided a transmission means for transmitting rotation of a crankshaft of an engine to a camshaft of a cam for opening and closing an intake valve or an exhaust valve. An engine having a variable valve timing mechanism interposed in the transmission means for adjusting a rotation phase between the crankshaft and the camshaft; and an engine temperature detection system for detecting a temperature of the engine. An engine valve timing control device that sets the target value of the rotation phase based on an engine temperature and controls the variable valve timing mechanism so that the rotation phase of a cam position with respect to a reference crank angle converges to the target value. When an abnormality of the engine temperature detection system is detected, a valve tie for setting the variable valve timing mechanism to the most retarded angle. Characterized by comprising a ring setting means.

That is, according to the present invention, there is provided an engine valve timing control apparatus for controlling a variable valve timing mechanism such that a rotation phase of a cam position with respect to a reference crank angle converges at least to a target value set based on engine temperature. Diagnose abnormalities in the engine temperature detection system. And, when the engine temperature detection system is abnormal,
Set the variable valve timing mechanism to the most retarded angle. As a result, even when the engine warm-up state cannot be detected, deterioration of the engine combustion can be prevented, the engine behavior can be stabilized, the engine output can be suppressed, and the required minimum traveling performance can be secured. This makes it possible to perform fail-safe control for a failure of the engine temperature detection system.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. First, an overall configuration of an engine with a variable valve timing mechanism to which the present invention is applied will be described with reference to FIG. In FIG.
This is an engine with a variable valve timing mechanism (hereinafter simply abbreviated as “engine”).
1 shows an HC horizontally opposed 4-cylinder gasoline engine. In both left and right banks of the cylinder block 1a of the engine 1,
Each cylinder head 2 is provided, and each cylinder head 2 is formed with an intake port 2a and an exhaust port 2b for each cylinder.

As an intake system of the engine 1, an intake manifold 3 communicates with each intake port 2a, and a throttle valve interlocked with an accelerator pedal through an air chamber 4 in which intake passages of respective cylinders are connected to the intake manifold 3. The throttle chamber 5 in which 5a is interposed communicates. An air cleaner 7 is mounted upstream of the throttle chamber 5 via an intake pipe 6, and the chamber 8 communicates with an air intake passage connected to the air cleaner 7.

The intake pipe 6 has a throttle valve 5
a bypass passage 9 is connected to the bypass passage 9 to control the idle rotation speed by adjusting the amount of bypass air flowing through the bypass passage 9 according to the valve opening during idling. A valve (ISC valve) 10 is interposed.

Further, an injector 11 is disposed immediately upstream of the intake port 2a of each cylinder of the intake manifold 3. In addition, an ignition plug 12 that exposes a discharge electrode at the tip to the combustion chamber is provided in the cylinder head 2 for each cylinder. Each ignition plug 12 is connected to an ignition coil 13 with a built-in igniter.

On the other hand, as an exhaust system of the engine 1, an exhaust pipe 15 is communicated with a collection portion of an exhaust manifold 14 which communicates with each exhaust port 2 b of the cylinder head 2, and a catalytic converter 16 is interposed in the exhaust pipe 15. To the muffler 17.

Next, the engine 1 will be described with reference to FIGS.
The variable valve timing mechanism will be described. The rotation of the crankshaft 18 of the engine 1 is transmitted to the intake camshafts 19 and the exhaust camshafts 20 disposed in the cylinder heads 2 of the left and right banks, respectively, by transmission means.
In this embodiment, the transmission means includes a crank pulley 21 fixed to the crankshaft 18, a timing belt 22, an intake cam pulley 23, an exhaust cam pulley 24 fixed to the exhaust camshaft 20, and the like. The crankshaft 18 and the camshafts 19, 2 are connected via these belts and pulleys.
The transmission coefficient is set such that 0 is a two-to-one rotation angle. The cams 19a provided on the intake camshaft 19 and the exhaust cams (not shown) provided on the exhaust camshaft 20 are each maintained at a rotation angle of 2: 1 with respect to the crankshaft 18. , 20 are driven to open and close the intake valve 25 and the exhaust valve 26.

As shown in FIG. 2, the intake cam pulley 23 and the intake cam shaft 19 are relatively rotated between the intake cam shafts 19 and the intake cam pulleys 23 in the left and right banks, so that the intake cam with respect to the crank shaft 18 is rotated. A hydraulically driven variable valve timing mechanism (hereinafter abbreviated as “VVT”) 27 that continuously changes the rotation phase (displacement angle) of the shaft 19 is provided.

As is well known, the VVT 27 has an oil flow control valve (hereinafter abbreviated as "OCV") 36R which is operated by a drive signal from an electronic control unit 60 described later.
The hydraulic pressure is switched and driven by (36L). In the following, the suffixes L, L
H indicates a right bank, and R and RH indicate a left bank.

The intake camshaft 19 is rotatably supported between the cylinder head 2 and a bearing cap (not shown). Rotor 2 having blade 28a
8 is attached by a bolt 29 so as to be integrally rotatable.

A housing 30 and a housing cover 31 are attached to the intake cam pulley 23 by bolts 32 so as to be integrally rotatable. A large number of external teeth 23 a for mounting the timing belt 22 are formed on the outer periphery of the intake cam pulley 23.

The intake cam shaft 19 is rotatably penetrated through the housing cover 31, and each vane 28a of the vane rotor 28 fixed to the intake cam shaft 19 is formed in a housing 30 integral with the intake cam pulley 23. The three fan-shaped space portions 33 are rotatably housed. Each fan-shaped space 3
Numeral 3 is divided into an advance chamber 33a and a retard chamber 33b by vanes 28a.

The advance chamber 33a is connected to the OC through the advance oil passages 28b, 19b and 34 formed in the vane rotor 28, the intake camshaft 19 and the cylinder head 2, respectively.
The OCV 36R is communicated with the A port 36a of the V36R (36L), and the OCV 36R is connected to the retard chamber 33b via the vane rotor 28, the intake camshaft 19, and the retard oil passages 28c, 19c, 35 formed in the cylinder head 2, respectively. (3
6L) B port 36b.

Further, the OCV 36R (36L) further comprises:
An oil supply port 36c connected to an oil supply passage 40 to which oil, that is, a predetermined oil pressure is supplied from an oil pan 37 via an oil pump 38 and an oil filter 39
And a drain port 36d and 36f communicating with the two drain passages 41 and 42, respectively, and a spool 36g having four lands and three passages formed between the lands is reciprocated in the axial direction. , A port 36a, B port 36b and oil supply port 36
c, and selectively communicates with the drain port 36d or 36f.

That is, the OCV 36R (36L)
Is a four-way control valve which comprises a linear solenoid valve or a duty solenoid valve, and switches the oil flow direction by reciprocating the spool 36g in the axial direction. The opening degree of the OCV 36R (36L) is adjusted by current control or duty control by an electronic control unit 60 described later, and the OCV 36R (36L) adjusts the opening degree of each advance chamber 33a.
The magnitude of the hydraulic pressure supplied to the retard chamber 33b is adjusted.

Reference numeral 28d denotes a stopper pin pushed through the vane 28a of the vane rotor 28,
Is in the most retarded state (see FIG. 4), it engages with a hole 30a formed in the housing 30 to perform positioning.

FIG. 3 shows the most advanced state of the VVT 27, and FIG. 4 shows the most retarded state of the VVT 27.

Here, the operation of the VVT 27 will be described in detail. As will be described in detail later, the crank rotor 4 is mounted on the crankshaft 18 and rotates in synchronization with the crankshaft 18.
3, projections 43a, 43 formed at predetermined crank angles.
b, 43c (see FIG. 8), a crank angle sensor 44 as a first rotational position detecting sensor for outputting a crank pulse representing the crank angle by detecting a crank angle index, and fixed to the rear end of the intake camshaft 19. A second rotation position for detecting a cam position index by a plurality of protrusions 45a (see FIG. 10) formed at equal angles on a cam rotor 45 rotating in synchronization with the intake cam shaft 19 and outputting a cam position pulse representing the cam position. A cam position sensor 46R (46L) as a detection sensor is provided. The crank pulse output from the crank angle sensor 44 and the cam position sensor 46R
(46L) is input to the electronic control unit 60, and based on the crank pulse and the cam position pulse, the rotation phase of the intake cam position with respect to the reference crank angle, that is, the crank position pulse, The VVT 27 is feedback-controlled so that the rotation phase of the intake camshaft 19 with respect to the shaft 18 converges to the target value (target valve timing) of the rotation phase set based on the engine operating state.

In this embodiment, the VVT 27 is provided only on the intake camshaft 19 side, and the opening and closing timing of the intake valve 25 is changed with respect to the opening and closing timing of the exhaust valve 26 as shown in FIG.

For example, as shown in FIG. 6, as the engine operation state, the basic fuel injection pulse width Tp (= K × Q / NE; Q is the intake air amount, K is the injector characteristic) Correction constant) and
At the time of idling at low load and low rotation, the intake valve 25
The opening / closing timing is retarded to reduce the overlap between the exhaust valve 26 and the intake valve 25, thereby stabilizing the idle rotation. Also, during high load operation, the intake valve 25
The opening and closing timing of the valve is advanced to increase the overlap between the exhaust valve 26 and the intake valve 25, thereby improving the scavenging efficiency and improving the engine output. In addition, at the time of low and medium load operation except low rotation such as idling. Optimum valve timing for improving fuel efficiency is obtained.

In this embodiment, when the OCV 36R (36L) using the linear solenoid valve is employed,
The larger the current value output from the electronic control device 60 with respect to V36R (36L), the more the spool 36g moves leftward (advanced) as shown in FIG.
It moves rightward (retards) as shown in FIG. Said O
In the CV36R (36L), the drive current (control current value) is controlled between 100 mA and 1000 mA and the spool 3
The 6g stroke is changed. Thus, the amount of connection between the advance-side oil passage 34 or the retard-side oil passage 35 and the oil supply passage 40, and the relationship between the advance-side oil passage 34 or the retard-side oil passage 35 and the drain ports 36d, 3
6f is changed between 0% and 100%, and the moving speed of the vane rotor 28 fixed to the intake camshaft 19 to the most advanced side or the most retarded side is changed.

That is, a crank pulse output from the crank angle sensor 44 and a cam output from the cam position sensor 46R (46L) with respect to a target valve timing (rotation phase target value) set based on the engine operating state. The rotation phase of the intake cam position with respect to the reference crank angle based on the position pulse, that is, the crankshaft 18
When the rotational phase (displacement angle) of the intake camshaft 19 with respect to is advanced, the electronic control unit 60 sets the OCV 36R
(36L), and the rotation phase (displacement angle) of the intake camshaft 19 with respect to the crankshaft 18 is retarded by the operation of the VVT 27.

Here, when the amount of current decreases, the OCV 36
The R (36L) spool 36g moves rightward in the figure,
The communication between the A port 36a and the drain port 36d causes the advance chamber 33a of the VVT 27 to
8b, 19b, 34, and the OCV 36R (36L) communicate with the drain passage 41. At the same time, the communication between the B port 36b and the oil supply port 36c allows the retard chamber 33b of the VVT 27 to move to the retard oil passage 28b.
c, 19c, 35, and the OCV 36R (36L) to communicate with the oil supply passage 40.

As a result, the oil pressure acting on the advance chamber 33a due to the drain of the oil in the advance chamber 33a of the VVT is reduced, and the oil supplied to the retard chamber 33b and acting on the retard chamber 33b is reduced. 4, the vane rotor 28 rotates in the counterclockwise direction in the figure, and the rotational phase of the intake cam shaft 19 with respect to the intake cam pulley 23, that is, the intake cam shaft 1 with respect to the crank shaft 18,
9 is retarded, and the intake valve 2 driven by the intake cam 19a of the intake camshaft 19 is retarded.
5, the opening / closing timing is retarded.

On the other hand, on the other hand, the rotational phase of the intake cam position with respect to the reference crank angle with respect to the target valve timing,
That is, when the rotational phase (displacement angle) of the intake camshaft 19 with respect to the crankshaft 18 is retarded, the electronic control unit 60 increases the amount of current output to the OCV 36R (36L) and operates the VVT27 to operate the crankshaft. The rotation phase (displacement angle) of the intake camshaft 19 with respect to 18 is advanced.

That is, when the current value increases, OCV3
The 6R (36L) spool 36g moves to the left in the drawing, and the A port 36a and the oil supply port 36c communicate with each other, so that the advance chamber 33a of the VVT 27 is connected to the advance oil passages 28b, 19b, 34, and the OCV 36R. (36L) and communicate with the oil supply passage 40. At the same time, the communication between the B port 36b and the drain port 36f allows the retard chamber 33b of the VVT 27 to communicate with the drain passage 42 via the retard oil passages 28c, 19c, 35 and the OCV 36R (36L). .

As a result, oil is supplied to the advance chamber 33a of the VVT to increase the hydraulic pressure acting on the advance chamber 33a, and the hydraulic pressure acting on the retard chamber 33b by the drain of the oil in the retard chamber 33b. As shown in FIG. 3, the vane rotor 28 rotates clockwise in FIG. 3, and the rotational phase of the intake cam shaft 19 with respect to the intake cam pulley 23,
That is, the rotational phase (displacement angle) of the intake camshaft 19 with respect to the crankshaft 18 is advanced, and the opening / closing timing of the intake valve 25 driven by the intake cam 19a of the intake camshaft 19 is advanced.

As described above, the rotational phase (displacement angle) of the intake camshaft 19 with respect to the crankshaft 18 converges on the target valve timing which is the rotational phase target value (target displacement angle) set based on the engine operating state. , V
The VT 27 is feedback-controlled.

In this embodiment, FIG.
As shown in (a), the front intake valve 25 and the exhaust valve 26 of the intake valve 25 and the exhaust valve 26 of each cylinder are used.
, The valve overlap amount of the intake valve 25 at the most retarded angle with respect to the exhaust valve 26 is set at 6 ° CA, and the valve overlap amount at the most advanced angle is set at 56 ° CA. Also, as shown in FIG. 7B, the rearmost intake valve 25 and exhaust valve 26 of the intake valve 25 and exhaust valve 26 of each cylinder are the valves at the most retarded angle of the intake valve 25 with respect to the exhaust valve 26. The overlap amount is set to 10 ° CA, and the valve overlap amount at the most advanced angle is set to 60 ° CA.

Therefore, in this embodiment, the rotation phase of each intake camshaft 19 with respect to the crankshaft 18 (the intake cam pulley 23) changes by a maximum of 50 ° CA due to the VVT 27.

Next, sensors for detecting the operating state of the engine will be described.

Immediately downstream of the air cleaner 7 of the intake pipe 6,
A thermal intake air amount sensor 47 using a hot wire or a hot film is interposed, and a throttle chamber 5 is provided.
The throttle opening sensor 48 is connected to the throttle valve 5a provided in the first embodiment.

The cylinder block 1a of the engine 1
Knock sensor 49 is attached to the cylinder block 1
A cooling water temperature sensor 51 as temperature detecting means for detecting the temperature of the engine 1 faces the cooling water passage 50 communicating the left and right banks a. This cooling water temperature sensor 51
Constitutes a water temperature sensor system (engine temperature detection system) together with a harness and a connector, etc., and the engine cooling water temperature Tw
Is output from the cooling water temperature sensor 51 to the electronic control unit 60. Then, the electronic control unit 60 controls the engine cooling water temperature T along with the engine speed NE and the basic fuel injection pulse width Tp representing the above-described engine operation state.
The target valve timing is set based on w.

Further, upstream of the catalytic converter 16, O
_Two sensors 52 are provided.

A crank angle sensor 44 is mounted on the outer periphery of a crank rotor 43 which is mounted on the crankshaft 18 of the engine 1.
Further, a cylinder discriminating sensor 53 is provided opposite to the back surface of the intake cam pulley 23 which makes a half rotation with respect to the crankshaft 18 (see FIG. 2), and a cam rotor fixed to the rear end of the intake camshaft 19 is provided. A cam position sensor 46R (46
L) are provided opposite to each other.

As shown in FIG. 8, the crank rotor 43 has projections 43a, 43b, 43c formed on its outer periphery, and these projections 43a, 43b, 43c are connected to the respective cylinders (# 1, # 2 and (# 3, # 4 cylinders) before compression top dead center (BTDC) θ1, θ2, θ3. In the present embodiment, θ1 = 97 ° CA, θ2 = 65
° CA, θ3 = 10 ° CA.

As shown in FIG. 9, on the outer peripheral side of the back surface of the intake cam pulley 23, protrusions 23b, 23
c, 23d are formed, the projection 23b is formed at the position of θ4 after the compression top dead center (ATDC) of the # 3, # 4 cylinders, and the projection 23c is composed of three projections, and the first projection is the # 1 cylinder. ATDC θ5. Further, protrusion 2
3d is formed by two projections, and the first projection is formed at the position of ATDC θ6 of the # 2 cylinder. In the present embodiment, θ4 = 20 ° CA, θ5 = 5 ° CA, θ6 =
20 ° CA. In addition, these cylinder discrimination projections 23
b, 23c, 23d and the cylinder discrimination sensor 53 are provided only in one bank.

Further, when the engine 1 employed in this embodiment is 4
The cam rotor 45 corresponds to the cylinder engine.
As shown in FIG. 10, a total of four protrusions 45a for detecting the cam position are formed on the outer periphery at equal angles of 180 ° CA. Each of these projections 45a is VV
By the operation of T27, the value changes between θ7 = BTDC 40 ° CA to ATDC 10 ° CA based on the compression top dead center of each cylinder. In FIG. 10, a cam rotor 45 fixed to the intake camshaft 19 on the RH side is shown.
Similarly, on the intake camshaft 19 on the LH side, a projection 45a for detecting a cam position is provided on the outer periphery thereof at every equal angle of 180 ° CA.
Each of these protrusions 45a is
, The compression top dead center of each cylinder
8 = Vary between BTDC 40 ° CA and ATDC 10 ° CA.

As shown in the time chart of FIG. 11, the crank rotor 43 and the cam rotor 45 are rotated by the rotation of the crankshaft 18, the intake cam pulley 23, and the intake camshaft 19 during the operation of the engine. 43 are detected by a crank angle sensor 44, and the projections 43a, 43b, 43c
From θ1, θ2, θ3 (BTDC 97 °, 65 °, 10
° CA) of each crank pulse
80 ° CA). Further, between the θ3 crank pulse and the θ1 crank pulse, each protrusion 23b, 23c, 23d of the intake cam pulley 23 is detected by the cylinder discrimination sensor 53, and a predetermined number of cylinder discrimination pulses are output from the cylinder discrimination sensor 53.

On the other hand, the VVT 27 causes the crankshaft 18
The protrusions 45a of the cam rotor 45 fixed to the rear end of each of the intake camshafts 19 of the right bank and the left bank, whose rotational phase changes, are detected by the cam position sensors 46R and 46L. Θ7,
The cam position pulse of θ8 is output.

In the following electronic control unit for engine control (hereinafter abbreviated as “ECU”) 60, the engine speed NE is calculated based on the input interval time of the crank pulse output from the crank angle sensor 44. Further, the pattern of the combustion stroke of each cylinder (for example, # 1 cylinder → # 3 cylinder → # 2 cylinder → # 4 cylinder) and the value obtained by counting the cylinder discrimination pulse from the cylinder discrimination sensor 53 by the counter are used. Based on the determination, the cylinders of the combustion stroke cylinder, the fuel injection target cylinder, and the ignition target cylinder are determined.

Further, the ECU 60 determines the reference crank angle based on the crank pulse (eg, θ1 pulse) output from the crank angle sensor 44 and the θ7, θ8 cam position pulses output from the cam position sensors 46R, 46L. Is calculated with respect to the rotation phase (displacement angle) of the intake cam position. Here, the rotation time per unit angle can be obtained from the engine speed NE, and the time from when the θ7 and θ8 cam position pulses are input to when the θ1 crank pulse is input is calculated as the time per unit angle rotation. By the multiplication, the rotational phase (displacement angle) of the intake cam position with respect to the reference crank angle, that is, the rotational phase (displacement angle) of each intake camshaft 19 with respect to the crankshaft 18 can be calculated.

The ECU 60 is provided with the above-described injector 1
1. Calculation of control amounts for actuators such as OCVs 36R and 36L for adjusting hydraulic pressure supplied to the spark plug 12, the ISC valve 10, and the VVT 27, and output of control signals, that is, fuel injection control, ignition timing control, idle rotation It performs number control, valve timing control (VVT control) for the intake valve 25, and the like. As shown in FIG. 12, the CPU 61, ROM 62, RAM 63, backup RAM 64, counter / timer group 65, and I / O
An O interface 66 is constituted mainly by a microcomputer connected via a bus line, and includes a constant voltage circuit 67 for supplying a stabilized power to each section, a driving circuit 68 connected to the I / O interface 66, and an A / D. A peripheral circuit such as the converter 69 is built in.

The counter / timer group 65 generates various counters such as a free-run counter, a counter for counting the input of a cylinder discrimination sensor signal (cylinder discrimination pulse), a fuel injection timer, an ignition timer, and a periodic interrupt. Timers, such as a timer for periodic interruption, a timer for measuring the input interval of a crank angle sensor signal (crank pulse), and a watchdog timer for monitoring a system abnormality, are collectively referred to for convenience. A timer is used.

The constant voltage circuit 67 is connected to the battery 71 via a first relay contact of a power supply relay 70 having two circuit relay contacts. The power supply relay 70 has one end of a relay coil grounded. The other end of the coil is connected to the drive circuit 68. A power supply line for supplying power from the battery 71 to each actuator is connected to the second relay contact of the power supply relay 70. One end of an ignition switch 72 is connected to the battery 71, and the other end of the ignition switch 72 is connected to I
/ O interface 66 is connected to the input port.

The constant voltage circuit 67 is directly connected to the battery 71. When the ignition switch 72 is detected to be ON and the contact of the power supply relay 70 is closed, the constant voltage circuit 67 supplies power to each unit in the ECU 60. On the other hand, regardless of whether the ignition switch 72 is ON or OFF, a backup power supply is always supplied to the backup RAM 64.

The input ports of the I / O interface 66 include a knock sensor 49, a crank angle sensor 44,
Cylinder discrimination sensor 53, cam position sensors 46R, 46L,
A vehicle speed sensor 54 for detecting a vehicle speed is connected, and further, via an A / D converter 69, an intake air amount sensor 47, a throttle opening degree sensor 48, a cooling water temperature sensor 5
1 and the O ₂ sensor 52 are connected, and the battery voltage VB is input and monitored.

On the other hand, the ISC valve 10, the injector 11, the O
The CVs 36R and 36L, a CHECK ENGINE lamp 55 as an alarm lamp disposed on an instrument panel (not shown) for centrally displaying various alarms, and a relay coil of a power supply relay 70 are connected via the drive circuit 68 and an igniter. The igniter of the built-in ignition coil 13 is connected.

An external connection connector 75 is connected to the I / O interface 66. A serial monitor (portable failure diagnosis device) 80 is connected to the external connection connector 75, so that a serial monitor is provided. 80, the input / output data in the ECU 60 and the ECU
The backup RAM 64 by the self-diagnosis function
The fault data including the water temperature sensor system NG flag FNGTW, which will be described later, which indicates the abnormality of the cooling water temperature sensor system stored in the system, is read out, and the trouble data indicating the content of the fault is read out for diagnosis. Further, the trouble monitor can be initially set (cleared) by the serial monitor 80.

For the diagnosis of trouble data by the serial monitor 80 and the initial set,
It is described in detail in Japanese Patent Publication No. 7-76730 by the present applicant.

In accordance with the control program stored in the ROM 62, the ECU 60 processes the detection signal from the sensors and switches, the battery voltage, and the like, which are input via the I / O interface 66, in the CPU 61. Based on the stored various data, the various learning value data stored in the backup RAM 64, and the fixed data stored in the ROM 62, the fuel injection amount, the ignition timing, the duty ratio of the control signal for the ISC valve 10, the OCV 36R, A control current value for 36L is calculated, and engine control such as fuel injection control, ignition timing control, idle speed control, valve timing control (VVT control), and the like are performed.

As described above, in the valve timing control, the reference crank angle is determined based on the crank pulse output from the crank angle sensor 44 and the cam position pulse output from the cam position sensor 46R (46L). The control current value for the OCVs 36R and 36L is calculated so that the rotational phase of the intake cam position with respect to the crankshaft 18, that is, the rotational phase of the intake camshaft 19 with respect to the crankshaft 18 converges to the target valve timing set based on the engine operating state. The control current is output to the OCVs 36R and 36L, and the VVT 27 is feedback-controlled.

At this time, the target valve timing is an engine cooling water temperature T which is one of the indicators of the engine operating state.
It is also regulated by w. That is, the ECU 60 sets an upper limit value and a lower limit value for the target valve timing according to the engine coolant temperature Tw, and regulates the target valve timing according to the engine coolant temperature Tw.

Therefore, if an abnormality occurs in the cooling water temperature sensor system, it becomes impossible to regulate the target valve timing. That is, if a break or short circuit occurs in the cooling water temperature sensor 51 or the harness or the connector between the cooling water temperature sensor 51 and the ECU 60, the detection of the engine cooling water temperature Tw and the transmission of the detection data cannot be performed. Things happen. When such a situation occurs, the engine temperature cannot be accurately detected, or the engine temperature itself cannot be detected. For this reason, the upper limit value and the lower limit value for the target valve timing set based on the engine cooling water temperature Tw are erroneously set, and the valve timing cannot be properly controlled according to the engine temperature. Timing control cannot be performed.

Therefore, when performing the valve timing control, it is necessary to diagnose the water temperature sensor system such as the cooling water temperature sensor 51.

In this case, when the output value of the cooling water temperature sensor 51 continues to be a value that cannot be normally obtained for a set time, it can be diagnosed that the water temperature sensor system is abnormal. For example, the cooling water temperature sensor 51 in the present embodiment usually has a value of 0.1 V or less or 4.85 V
The above value is not output, and if it continues for a predetermined time (for example, 0.2 sec) or more, it can be determined that the water temperature sensor system is abnormal. Therefore, in the present embodiment,
The ECU 60 monitors the output value of the cooling water temperature sensor 51, and diagnoses that the water temperature sensor system is abnormal when the output value is out of the specified value for a predetermined time. As described later, when the water temperature sensor system is diagnosed as abnormal,
Performs fail-safe control to make the target valve timing the most retarded. In other words, the ECU 60 prevents engine combustion from deteriorating by the most retarded operation, stabilizes the engine behavior, and suppresses the engine output to ensure the necessary minimum traveling performance.

That is, the ECU 60 realizes a function as a valve timing setting means according to the present invention.

The diagnosis processing for the water temperature sensor system according to the present invention and the valve timing control based on the engine temperature, which are executed by the ECU 60, will now be described with reference to FIGS.
This will be described according to the flowchart shown in FIG.

First, the ignition switch 72 is turned on.
Then, when the power is supplied to the ECU 60, the system is initialized and each flag and each counter are initialized except for trouble data and data such as various learning values stored in the backup RAM 64. And
When the starter switch (not shown) is turned on and the engine 1
Is started, a water temperature sensor system diagnostic routine shown in FIG. 13 is executed every predetermined time (for example, 10 msec).

In this water temperature sensor system diagnosis routine, when the water temperature sensor output voltage VTW continues to be a value that cannot be normally obtained for a set time, a failure of the cooling water temperature sensor 51, a wiring abnormality or the like occurs, and the water temperature sensor system becomes abnormal. Diagnose that

First, in step S1, the output voltage VTW of the cooling water temperature sensor 51 is compared with a preset lower limit determination threshold VL (for example, 0.1 V). At this time, if the water temperature sensor output voltage VTW exceeds the lower limit determination threshold VL, the process proceeds to step S2, and the flow proceeds to the upper limit determination threshold VH.
(For example, 4.85 V). When the water temperature sensor output voltage VTW is lower than the upper limit determination threshold VH,
When L <VTW <VH, the water temperature sensor system is immediately diagnosed as normal, and the process proceeds to step S3 to clear the water temperature sensor system NG flag FNGTW (FNGTW ← 0). Then, proceeding to step S4, a measure for turning off the CHECK ENGINE lamp (engine failure warning light) 55 is performed, and the abnormal duration count value CNG is cleared in step S5 (CNG ← 0), and the routine exits.

On the other hand, if the water temperature sensor output voltage VTW is equal to or lower than the lower limit determination threshold VL in step S1, or if the water temperature sensor output voltage VTW is equal to or higher than the upper limit determination threshold VH in step S2, the process proceeds to step S6. It is determined whether or not the sensor system NG flag FNGTW has already been set. At step S6, the water temperature sensor system NG flag F
If NGTW has been cleared (FNGTW = 0), the process proceeds to step S7, and the abnormal continuation time count value CNG
Is greater than a set value CS (for example, a value equivalent to 0.2 sec). The water temperature sensor system NG flag F
If NGTW is set (FNGTW =
1) Exit the routine as it is.

If it is determined in step S7 that the abnormal continuation time count value CNG is less than the set value CS, the process proceeds to step S8, where the abnormal continuation time count value CNG is counted up, and the routine exits (CNG ← CNG + 1) routine. On the other hand, when the abnormal continuation time count value CNG exceeds the set value CS, the process proceeds to step S9, and the water temperature sensor system NG flag FNGTW is set (FNGTW ← 1). Then, the process proceeds to step S10, and CHECK ENGINE.
A measure for turning on the lamp 55 is performed, and the abnormal continuation time count value CNG is cleared through the above step S5 (CN
G ← 0) Exit the routine.

The diagnosis result of the water temperature sensor system executed at predetermined time intervals is stored in the backup RAM 64. In this case, FNGTW = 1 indicates abnormality of the water temperature sensor system, and FNGTW = 0 indicates normality of the water temperature sensor system. Then, this water temperature sensor system NG flag FNGT
VVT is controlled with reference to W.

FIG. 14 is a flowchart showing a valve timing control routine in consideration of the engine cooling water temperature Tw, and this routine is also executed at a predetermined cycle. In the valve timing control according to the present embodiment, F
When NGTW = 0, the upper and lower limits of the target valve timing VTTTGT are set based on the engine coolant temperature Tw, and the target valve timing is regulated according to the engine temperature. On the other hand, if FNGTW = 1, it is determined that the water temperature sensor system is abnormal, and the target valve timing VTTGT is made the most retarded (VTTGT = 0 °) to ensure the required minimum traveling performance.

In the routine of FIG. 14, first, in step S1
At 1, the NG flag FNGTW of the water temperature sensor system is referred to. When FNGTW = 0, the water temperature sensor system is determined to be normal, and the process proceeds to the control routine of step S12 and subsequent steps.

In step S12, a table (TBL; see FIG. 6) stored in the ROM 62 is searched based on the basic fuel injection pulse width Tp representing the engine load and the engine speed NE, and the target valve timing (rotation) is calculated by interpolation. Phase target value) VTTGT is set. When the target valve timing VTTTGT is set, step S13 is performed.
Then, based on the engine cooling water temperature Tw obtained by the cooling water temperature sensor 51, a table stored in the ROM 62 is searched and an upper limit regulation value VTlimit U is set by interpolation calculation. Subsequently, in step S14, a table stored in the ROM 62 is searched based on the engine coolant temperature Tw, and the lower limit regulation value VTlimit is calculated by interpolation calculation.
Set L.

Here, the upper limit regulation value VTlimi for the target valve timing set based on the cooling water temperature Tw.
t U and the lower limit value VTlimit L reduce the pumping loss as much as possible when the engine is cold, suppress the unnecessary reduction of the effective compression ratio, and prevent the deterioration of the combustion state of the engine 1 in the light load range. FIG. 15 shows the characteristics of each of the above tables.

That is, in the present embodiment, appropriate upper and lower limit values VTlimit U and VTlimit L with respect to the target valve timing are obtained in advance by simulation or experiment using the cooling water temperature Tw as a parameter, and the obtained values are stored in the ROM 62 as a table. Stored in a series of addresses.

In the present embodiment, as shown in FIG.
When the engine cooling water temperature Tw is lower than 10 ° C., the valve timing of the intake valve is set to the most retarded angle in the entire operation range, and the valve overlap amount is reduced. And the cooling water temperature Tw
When the engine is cold from 10 ° C. to 70 ° C., the upper limit regulation value VTlimi is increased in accordance with the rise of the engine coolant temperature Tw.
The regulation range based on t U and the lower regulation value VTlimit L is gradually expanded, and the regulation based on the regulation value is substantially released when the engine is warm at 70 ° C. or more. Thereby, Tw ≧ 7
When the engine is cold at Tw <70 ° C., when the engine is cold at 0 ° C., the region where the valve overlap amount is relatively small is widened to prevent deterioration of the engine combustion state and increase the cooling water temperature Tw. Upper and lower limit value VT according to
By gradually expanding the regulation range by limit U and VTlimit L, the connection of VVT control is smoothed and controllability is improved.

After setting these regulation values, the routine proceeds to step S15, where the upper limit of the target valve timing VTTGT is regulated. That is, the target valve timing VT
The TGT is compared with the upper limit control value VTlimit U. If the target valve timing VTTTGT exceeds the upper limit control value VTlimit U, the process proceeds to step S16, where the upper limit control value VTlimit U is set to the target valve timing VTTGT, and the step is performed. Proceed to S17. On the other hand, if the target valve timing VTGTGT is equal to or less than the upper limit regulation value VTlimit U, the process directly proceeds to step S17.

Then, the target valve timing VTTTGT
After the upper limit is set, the lower limit is set. That is, in step S17, the target valve timing VTTG
T is compared with the lower limit value VTlimit L. If the target valve timing VTTGT is lower than the lower limit value VTlimit L, the process proceeds to step S18, and the lower limit value V
After Tlimit L is set to the target valve timing VTTTGT, the process proceeds to step S19. On the other hand, when the target valve timing VTTGT is equal to or larger than the lower limit regulation value VTlimit L,
Proceed directly to step S19.

As described above, the target valve timing VTTG
After T is set, in step S19, the actual valve timing VT indicating the actual displacement angle of the current rotational phase is calculated based on the outputs of the cam position sensor 46R (46L) and the crank angle sensor 44.

After calculating the actual valve timing VT, the routine proceeds to step S20, where the control current value IVT for the OCV 36R (36L) is set. That is, the control current value IVT required to converge the valve timing from the current value to the target valve timing VTTGT is calculated. In the present embodiment, the target valve timing VTTG
The control current value IVT is calculated by calculating the difference between T and the actual valve timing VT, multiplying the difference by a proportional gain K, and adding the result to the holding current value IVTH of the OCV 36R (36L).

Here, the OCV 36R (36L) is controlled with the control current value in the range of 100 mA to 1000 mA as described above. At this time, if the OCV 36R (36L) is controlled by a certain control current value, the OCV 36R (36L) is controlled.
L) spool 36g, A port 3 depending on the land
6a, it is displaced to a position to close the B port 36b. Therefore, the advance side oil passage 34 or the retard side oil passage 3
5 and the oil supply passage 40, the advance-side oil passage 34 or the retard-side oil passage 35 and the drain port 3
6d and 36f are connected to 0%, respectively, and VVT
The 27 vane rotor 28 is not displaced to the advance side or the retard side, the movement speed becomes zero, and is held at that position. The control current value corresponding to this holding state is the holding current value I
VTH, which is initially set by a value obtained in advance by a simulation or an experiment.
As is well known in Japanese Patent Application Laid-Open No. 09840, this holding current value IVTH is appropriately updated by learning.

When the control current value IVT is calculated in step S20, the process proceeds to step S21, where the value is set, and based on this value, the VVT 27 is controlled to adjust the rotation phase. Thus, the target valve timing VTTGT is set based on the engine operating state based on the basic fuel injection pulse width Tp and the engine speed NE, and the OCV 36R (36L) is set according to the difference between the target valve timing VTTGT and the actual valve timing VT. The control current value IVT is set. And the actual valve timing V
Feedback control is performed so that T converges to the target valve timing VTTGT suitable for the engine operating state.

On the other hand, in the present embodiment, step S11
In the case where the water temperature sensor system NG flag FNGTW = 1, it is determined that the water temperature sensor system is abnormal, and the process proceeds to step S22. Then, in step S22, the target valve timing VTTGT is retarded most (VTTGT ← 0 °), and VT
After setting TGT to 0 °, the process proceeds to step S19 and subsequent steps. As a result, in step S20, a control current value IVT is calculated according to the difference between the target valve timing VTTTGT and the actual valve timing VT so as to make the actual valve timing VT the most retarded. Timing is most retarded.

As a result, the opening / closing timing of the intake valve 25 is retarded, the overlap between the exhaust valve 26 and the intake valve 25 is minimized, the engine rotation is stabilized, and the engine output is suppressed. Therefore, even when the engine warm-up state cannot be detected due to an abnormality in the water temperature sensor system, it is possible to prevent engine combustion from deteriorating, stabilize the engine behavior, and secure the necessary minimum traveling performance. Fail-safe control for a failure of the temperature detection system can be realized.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments and can be variously modified without departing from the gist thereof. Needless to say,

For example, in the above-described embodiment, an example in which only the valve timing of the intake valve is changed by the variable valve timing mechanism has been described. However, the present invention is not limited to this. The present invention can be applied to any engine having a variable valve timing mechanism that changes at least one of the valve timings of the exhaust valve using a variable valve timing mechanism.

The engine to be used may be an engine with a variable valve timing mechanism, and at least one camshaft interlocking with the crankshaft may be used.
The engine need not be a C (double over head camshaft) type engine, and is not limited to a horizontally opposed engine.

Further, the transmission means between the crankshaft and the camshaft is not limited to the timing belt system according to the embodiment, but may employ a suitable system such as a chain system or a gear system.

The abnormality diagnosis for the water temperature sensor system shown in FIG. 13 is not limited to the above-described method, and other well-known methods can be appropriately applied. Further, in the above-described embodiment, when the water temperature sensor system is abnormal, the valve timing is set to the most retarded angle by setting the target valve timing VTTGT to the most retarded angle. However, the OCV 36R (3
6L) to the control lower limit (IT
V = 100 mA), the valve timing may be controlled to the most retarded angle.

Further, the setting of the target valve timing is not limited to the present embodiment, and if the target valve timing is set at least based on the engine temperature,
The present invention is applicable.

[0093]

As described above, according to the first aspect of the present invention, there is provided a valve timing control apparatus for an engine which controls a variable valve timing mechanism so as to converge at least to a target valve timing set based on an engine temperature. Diagnose abnormalities in the engine temperature detection system.
When the engine temperature detection system is abnormal, the variable valve timing mechanism is set to the most retarded angle, so that even when the engine warm-up state cannot be detected, deterioration of engine combustion is prevented and engine behavior is stabilized. As a result, the engine output can be suppressed, the required minimum traveling performance can be ensured, and fail-safe control for a failure of the engine temperature detection system can be performed.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an engine with a variable valve timing mechanism according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a variable valve timing mechanism according to the first embodiment;

3 is a sectional view of the variable valve timing mechanism, taken along the line AA in FIG.

FIG. 4 is a sectional view taken along the line AA of FIG. 2, showing the most retarded state of the variable valve timing mechanism;

FIG. 5 is an explanatory diagram showing a change in valve timing of an intake valve with respect to an exhaust valve;

FIG. 6 is an explanatory diagram showing valve timing characteristics according to the first embodiment;

FIG. 7 is an explanatory diagram showing a change in a valve overlap amount between an intake valve and an exhaust valve by the variable valve timing mechanism.

FIG. 8 is a front view of the crank rotor and the crank angle sensor according to the first embodiment;

FIG. 9 is a rear view of the intake cam pulley;

FIG. 10 is a front view of a cam rotor and a cylinder discrimination sensor according to the first embodiment;

FIG. 11 is a time chart showing a relationship among a crank pulse, a cylinder discrimination pulse, a cam position pulse, a combustion stroke cylinder, an ignition timing, and a fuel injection timing.

FIG. 12 is a circuit diagram of the electronic control system according to the first embodiment;

FIG. 13 is a flow chart of a water temperature sensor system diagnosis routine;

FIG. 14 is a flowchart of a valve timing control routine using engine coolant temperature according to the first embodiment;

FIG. 15 is an explanatory diagram showing characteristics of an upper limit value and a lower limit value according to the first embodiment;

[Explanation of symbols]

Reference Signs List 1 engine with variable valve timing mechanism 18 crankshaft 19 intake camshaft 23 intake cam pulley (transmission means) 24 exhaust cam pulley 25 intake valve 26 exhaust valve 27 variable valve timing mechanism 51 cooling water temperature sensor 60 electronic control unit (valve timing setting means) CNG Abnormal continuation time count value FNGTW Water temperature sensor system NG flag IVT control current value IVTH holding current value Tw Engine cooling water temperature VH Upper limit judgment threshold VL Lower limit judgment threshold VT Actual valve timing VTlimit L Lower limit regulation value VTlimit U Upper regulation value VTTGT Target valve timing (Rotation phase target value) VTW Water temperature sensor output voltage

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) FB05 FB06 HA01Z HA06Z HA13X HA13Z HC05Z HD05Z HE01Z HE03Z HE05Z HE08Z HF02Z HF21Z

Claims (1)

[Claims] 1. A transmission means for transmitting rotation of a crankshaft of an engine to a camshaft of a cam for opening and closing an intake valve or an exhaust valve, and rotation between the crankshaft and the camshaft interposed in the transmission means. In an engine equipped with a variable valve timing mechanism for adjusting a phase and an engine temperature detection system for detecting the temperature of the engine, a target value of the rotation phase is set based on at least the engine temperature, and a reference value for a reference crank angle is set. An engine valve timing control device that controls the variable valve timing mechanism so that a rotation phase of a cam position converges to the target value, wherein when an abnormality in the engine temperature detection system is detected, the variable valve timing mechanism is controlled. An engine valve timing comprising valve timing setting means for setting a most retarded angle. Grayed control device.