JPH04254224A - Control device of continuously variable transmission for vehicle having lean burn internal combustion engine - Google Patents

Abstract

PURPOSE:To provide a control device of a belt type continuously variable trans mission for a vehicle having a lean burn engine, which can attain favorable running fuel consumption of a vehicle in a continuously variable transmission for a vehicle having a lean burn internal combustion engine which is switched to a lean burn region for performing lean burn at an air-fuel mixture more leaner than the theoretical air fuel ratio and to a stoichiometric burn area. CONSTITUTION:In the lean burn condition of an engine 10, when the margin torque Ne<y> decided by a margin torque deciding means 500 is lower than a designated value delta, the target value Nin<o> in the change gear ratio control for a continuously variable transmission gear is changed in the direction of changing the gear change ratio gamma to the speed reduction side (increase side) by a gear change ratio changing means 502. Thus, during the gear change ratio control of CTV 16, if the gear change ratio is changed to the speed reduction side, the engine rotating speed is increased for a change on the constant horse power curve, so that the margin torque is sequentially increased. Thus, the frequency of use of lean burn of the engine 10 is increased so as to improve the running fuel consumption of a vehicle favorably.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a continuously variable transmission for a vehicle equipped with a lean-burn internal combustion engine.

0002

2. Description of the Related Art Lean burn engines are equipped with an EGR valve and a swirl control valve to create turbulent flow, as described in Japanese Patent Laid-Open No. 61-268845, for example, in order to purify exhaust gas from automobiles. The combustion control means controls the air-fuel mixture to be leaner than the stoichiometric air-fuel ratio, and one of a plurality of combustion states is selected depending on the load. Furthermore, as described in, for example, Japanese Patent Application Laid-open No. 58-191358, a continuously variable transmission has a gear ratio that is continuously variable so that the internal combustion engine operates along an optimum fuel efficiency curve. It is known as a technology that can improve the fuel efficiency of vehicles because it can be adjusted to Since the lean-burn internal combustion engine can provide suitable fuel efficiency due to its small pumping loss, it is desirable to install the lean-burn internal combustion engine and the continuously variable transmission in a vehicle in order to further improve the fuel efficiency of the vehicle. is possible.

0003

[Problems to be Solved by the Invention] Generally speaking, in the lean-burn internal combustion engine, when the engine load is lower than a predetermined limit, that is, when running under light load, the air-fuel ratio of the air-fuel mixture is set to the ideal value. When the internal combustion engine is put into a lean combustion state by setting the air-fuel ratio to the lean side, and the engine load value is higher than the predetermined engine load value, that is, when running at a medium load or at a high load, NOx generation is preferable to maintaining suitable fuel efficiency. In order to suppress this, control is performed to switch to a combustion state where the air-fuel ratio is richer, for example, a combustion state where recirculated gas is mixed with the air-fuel mixture where the air-fuel ratio A/F is the theoretical value (stoichiometric + EGR combustion state). It is being said. However, according to such combustion state switching control, when the surplus torque decreases while the vehicle is running with the internal combustion engine in a lean combustion state, the accelerator pedal is depressed in an attempt to obtain more surplus torque. The combustion state is switched to +EGR combustion state. For this reason, for example, when driving in the US emission test mode LA#4HWY, etc., the lean burn state is not achieved, so the ratio of lean burn being selected while the vehicle is running is small, resulting in the inconvenience that sufficient fuel efficiency cannot be obtained. .

The present invention has been made against the background of the above circumstances, and its object is to provide a continuously variable transmission for a vehicle equipped with a lean-burn internal combustion engine that can be switched to one of a plurality of combustion states. An object of the present invention is to provide a control device that can improve the fuel efficiency of a vehicle.

[0005]

[Means for Solving the Problems] To achieve the above object, the gist of the present invention is to provide a continuously variable transmission for a vehicle equipped with a lean burn internal combustion engine that can be switched to one of a plurality of combustion states. 1. A control device for adjusting the gear ratio of a continuously variable transmission so that the lean-burn internal combustion engine operates along a predetermined optimal curve in a motor vehicle, the control device comprising: (a)
(b) surplus torque determining means for determining surplus torque when the lean-burn internal combustion engine is in a lean-burn region; and (b) surplus torque of the lean-burn internal combustion engine determined by the surplus torque determining means is below a predetermined value. In the rotated state, the gear ratio changing means changes the gear ratio to a speed reduction side.

[0006]

[Operation] By doing this, when the surplus torque of the internal combustion engine in the lean burn state determined by the surplus torque determining means is less than a predetermined value, the gear ratio changing means changes the gear ratio of the continuously variable transmission. The speed is changed to the deceleration side.

[0007]

[Effects of the Invention] When the gear ratio of the continuously variable transmission is changed to the reduction side as described above, the rotational speed of the internal combustion engine is increased by the amount of the change on the equal horsepower curve, and as a result, the margin torque is increased. Ru. Therefore, by controlling the gear ratio in this manner, the selection ratio of lean combustion in the internal combustion engine is increased, so that the running fuel efficiency of the vehicle is suitably improved.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a vehicle power transmission device including a belt type continuously variable transmission to which an embodiment of the present invention is applied. In the figure, the power of an engine 10 is transmitted through a torque converter 12 with a lock-up clutch, a forward/reverse switching device 14, and a belt-type continuously variable transmission (hereinafter referred to as CVT) 1.
6, a reduction gear device 18, and a differential gear device 20 to be transmitted to drive wheels 24 connected to an axle 22.

The torque converter 12 is connected to the engine 1.
The converter output shaft 32 is fixed to a pump impeller 28 connected to the crankshaft 26 of No. 0, and a converter output shaft 32 provided concentrically between the crankshaft 26 and the central shaft 54 of the rear-stage forward/reverse switching device 14. A turbine impeller 34 receives oil from the pump impeller 28 and is rotated; a stator impeller 38 is fixed to a non-rotating member via a one-way clutch 36; and a converter output shaft 32 via a damper 40.
A lock-up clutch 42 is fixed to the lock-up clutch 42, and when the lock-up clutch 42 is not engaged, torque is transmitted at an amplification factor corresponding to the input/output rotational speed ratio. The lock-up clutch 42 is configured such that, for example, the vehicle speed
When the engine rotational speed or the rotational speed of the turbine impeller 34 exceeds a predetermined value, the crankshaft 26 is activated.
This directly connects the converter output shaft 32 and the converter output shaft 32.

The forward/reverse switching device 14 is a double pinion type planetary gear device that is selectively switched to a forward gear or a reverse gear depending on the operating position of a shift lever (not shown), and is a double pinion type planetary gear device that is selectively switched to a forward gear or a reverse gear depending on the operating position of a shift lever (not shown). It is provided concentrically with the input shaft 44. This planetary gear device includes a sun gear 46 fixed to a converter output shaft 32 that functions as an input shaft of the forward/reverse switching device 14.
And, the ring gear 4 provided concentrically with this sun gear 46
8, a pair of planetary gears 50 and 52 that mesh with one and the other of ring gear 48 and sun gear 46, and mesh with each other; sun gear 46 and ring gear 4;
8, a flange portion 56 extending from the central shaft 54 toward the outer periphery, and a pair of planetary gears 50 extending from the flange portion 56 in a direction parallel to the axis of the central shaft 54. and a carrier 60 having a carrier pin 58 rotatably supporting the carrier pin 52 and the carrier pin 58 . Further, this planetary gear device includes a forward clutch 62 for coupling between the converter output shaft 32 and the carrier 60.
and a reverse brake 64 for connecting the ring gear 48 and the fixed housing 63. Therefore, when the forward clutch 62 is engaged,
Since the converter output shaft 32 and the carrier 60 are connected and the converter output shaft 32 and the central shaft 54 rotate together, the CVT 16 and below are rotated in the forward direction. On the other hand, when the reverse brake 64 is engaged instead of the forward clutch 62, the housing 63 and the ring gear 48 are connected and the ring gear 48 is brought into a non-rotating state. On the other hand, the central shaft 54 is rotated in the opposite direction, and the CVT 16 and below are rotated in the reverse direction.

The CVT 16 has variable pulleys 66 and 68 provided on its input shaft 44 and output shaft 45, respectively.
and a transmission belt 70 wound around the variable pulleys 66 and 68. This transmission belt 70 is disclosed in, for example, Japanese Patent Application Laid-open No. 61-116146,
As described in Japanese Patent No. 62445, a belt block is constructed by connecting a large number of belt blocks that are pressed by walls between the V grooves of variable pulleys 66 and 68 along an endless annular hoop or chain. . Variable pulley 6
6 and 68 are fixed rotating bodies 72 and 74 fixed to the input shaft 44 and the output shaft 45, respectively, and the input shaft 44
and movable rotating bodies 76 and 7 provided on the output shaft 45 so as to be movable in the axial direction but not relatively rotatable around the axis.
When the movable rotating bodies 76 and 78 are moved by hydraulic cylinders 80 and 82 functioning as hydraulic actuators, the V groove width, that is, the hanging diameter (effective diameter) of the transmission belt 70 is changed, and the CVT 16
gear ratio γ (=rotational speed Nin of input shaft 44/output shaft 4
5 rotational speed (Nout)) is changed. The hydraulic cylinder 80 is operated exclusively to change the gear ratio γ, and the hydraulic cylinder 82 is operated exclusively to obtain the minimum clamping force within a range where the transmission belt 70 does not slip. Note that the hydraulic pump 84 is a CV pump (not shown).
It constitutes the hydraulic power source of the T hydraulic control system, and is constantly driven to rotate by a pump impeller 28 that rotates together with the engine 10.

[0012] The output shaft 45 of the CVT 16 is provided with a first gear 86 that functions as an output gear. Further, a second gear 90 that meshes with the first gear 86 and a third gear 92 having a smaller diameter are fixed to a rotating shaft 88 that is rotatably provided around an axis parallel to the axis of the first gear 86. The third gear 92 is meshed with the large diameter gear 94 of the differential gear 20 . The first gear 86 and the second gear 90
, and the third gear 92 constitute the reduction gear device 18. The differential gear device 20 includes a pair of differential small gears 96 that are rotatably supported around an axis perpendicular to the rotational axis of the axle 22 and rotate integrally with the large diameter gear 94, and the differential small gears 96. and a pair of differential large gears 98 that mesh with the axle shaft 22 and are connected to the axle shaft 22. Therefore, after the power transmitted from the reduction gear device 18 is equally distributed to the left and right axles 22 in the differential gear device 20,
The signal is transmitted to the left and right drive wheels 24.

Transmission electronic control unit 110
is a so-called microcomputer consisting of a CPU 112, a ROM 114, a RAM 116, an interface (not shown), and the like. An input shaft rotation sensor 120 and an output shaft rotation sensor 122 that detect each, a throttle valve opening sensor 124 that detects the throttle valve opening provided in the intake pipe of the engine 10, and the operation position of the shift operation lever 126, that is, L, S , D, N, R, and P ranges.
, a signal representing the vehicle speed SPD, a signal representing the input shaft rotational speed Nin, a signal representing the output shaft rotational speed Nout, a signal representing the throttle valve opening θth, and a shift operation lever 12.
Signals representing the operation positions Ps of 6 are supplied respectively. CPU 11 of the electronic control device 110
2 uses the temporary storage function of the RAM 116 to store R in advance.
The input signal is processed according to a program stored in the OM 114, and the first solenoid valve 102, the second solenoid valve 104, and the linear solenoid valve 106 in the hydraulic control circuit 100 are controlled, respectively.

FIG. 2 shows the main parts of the hydraulic control circuit 100, and the hydraulic pump 84 is connected to the hydraulic control circuit 10.
0 oil pressure source. The hydraulic pump 84 sucks the hydraulic oil that has returned to an oil tank (not shown) through the strainer 140, and also sucks the hydraulic oil that has been returned through the return oil passage 142 and pumps it to the first line oil passage 144. In this embodiment, the hydraulic oil in the first line oil passage 144 is leaked to the return oil passage 142 and the lock-up clutch pressure oil passage 148 by the overflow (relief) type first pressure regulating valve 146, so that the hydraulic oil in the first line oil passage 144 is The first line oil pressure Pl1 in the oil passage 144 is regulated. Further, the second line oil pressure Pl2 in the second line oil passage 152 is regulated by reducing the first line oil pressure Pl1 by the second pressure regulating valve 150 of the pressure reducing valve type. Note that a relief valve 154 is provided in the first line oil passage 144 to prevent an abnormal pressure increase above a predetermined pressure.
is provided.

The second pressure regulating valve 150 includes a spool valve 160 that opens and closes between the first line oil passage 144 and the second line oil passage 152, a spring seat 162, a return spring 164, and a plunger 166. Also,
At the shaft end of the spool valve element 160, there are a first land 168, a second land 170, and a third land 172 whose diameters increase in order.
are formed sequentially. Between the second land 170 and the third land 172 is an oil chamber 176 into which the second line oil pressure Pl2 is introduced as feedback pressure through a throttle 174.
is provided so that the spool valve element 160 is urged in the valve closing direction by the second line oil pressure Pl2. Further, an oil chamber 180 is provided on the end surface side of the first land 168 of the spool valve element 160, through which a gear ratio pressure Pr (described later) is guided through a throttle 178, and the spool valve element 160 is closed by the gear ratio pressure Pr. The valve is biased toward the valve. Further, within the second pressure regulating valve 150, a biasing force of a return spring 164 in the valve opening direction is applied to the spool valve element 160 via a spring seat 162. Also, the first land 168 and the second land of the spool valve 160 are
An oil chamber 182 is provided between the land 170 and the signal pressure PsolL output from the linear solenoid valve 106, and the signal pressure PsolL causes the spool valve element 160 to be moved in the valve closing direction by the second line oil pressure Pl2. It is designed to be biased toward Furthermore, the plunger 16
An oil chamber 184 for applying a throttle pressure Pth (described later) is provided on the end face side of the spool valve 16.
0 is biased in the valve opening direction by this throttle pressure Pth. Therefore, the pressure receiving area (cross-sectional area) of the first land 168 is A1, the cross-sectional area of the second land 170 is A2, the cross-sectional area of the third land 172 is A3, the pressure receiving area of the small diameter land 188 of the plunger 166 is A4,
When the urging force of the return spring 164 is W, the spool valve element 160 is balanced at a position where Equation 1 is satisfied. That is, by moving the spool valve 160 according to formula 1, the first line oil path 1
44 is caused to flow into the second line oil path 152 and the state in which the hydraulic oil in the second line oil path 152 is flowed out to the drain port is repeated, and the second line oil pressure Pl2 is regulated. They are made to do so. Since the second line oil passage 152 is a relatively closed system, the second pressure regulating valve 150 reduces the first line oil pressure Pl1, which is a relatively high oil pressure, as described above, thereby reducing the second line oil pressure Pl1.
12 is generated as shown in FIG. Note that FIG. 3 shows the characteristics when the throttle pressure Pr is constant, the polygonal line shows the pressure regulation value (basic output pressure Pmec) when the signal pressure PsolL is zero, and the curve shows the signal pressure PsoL.
It shows the pressure regulation value when the pressure is regulated to the ideal pressure Popt by 1L. That is, the signal pressure PsolL is supplied to control the value to be reduced from the basic output pressure Pmec in order to obtain the ideal pressure Popt.

[0016]

[Math 1]

The first pressure regulating valve 146 has a spool valve 200
, spring seat 202, return spring 204
, the first plunger 206, and the first plunger 2
The second plunger 208 has the same diameter as the second land 215 of 06
It is equipped with The spool valve 200 opens and closes between the first line oil passage 144, the return oil passage 142, and the lock-up clutch pressure oil passage 148, and has a first line as feedback pressure on the end surface of the first land 212. An oil chamber 213 is provided for applying the oil pressure Pl1 through a throttle 211, and this first line oil pressure Pl1
The spool valve element 200 is biased in the valve opening direction. Throttle pressure Pt is applied between the first land 214 of the first plunger 206, which is provided coaxially with the spool valve element 200, and the second land 215, which has a smaller diameter.
An oil chamber 216 is provided between the second land 215 and the second plunger 208 for guiding the hydraulic pressure Pin in the primary side hydraulic cylinder 80 via a branch oil passage 220. An oil chamber 217 is provided, and a second line hydraulic pressure Pl2 is provided at the end face of the second plunger 208.
An oil chamber 218 is provided for guiding the oil. The biasing force of the return spring 204 is applied to the spring seat 2
02 in the valve closing direction, the pressure-receiving area of the first land 212 of the spool valve 200 is A5, the cross-sectional area of the first land 214 of the first plunger 206 is A6, and the pressure-receiving area of the first land 212 of the spool valve 200 is A5. 2nd land 215 and 2nd
When the cross-sectional area of the plunger 208 is A7 and the biasing force of the return spring 204 is W, the spool valve 200 is balanced at a position where Equation 2 is satisfied, and the first line oil pressure Pl1 is regulated.

[0018]

[Math 2]

In the first pressure regulating valve 146, the hydraulic pressure Pin in the primary side hydraulic cylinder 80 is equal to the second line hydraulic pressure Pl2.
(In a steady state, Pl2 = secondary hydraulic cylinder 82 internal hydraulic pressure Pout), the first plunger 206 and the second plunger 208 are separated, and the thrust due to the primary hydraulic cylinder 80 internal hydraulic pressure Pin acts on the spool valve element 200 in the valve closing direction, but if the hydraulic pressure Pin in the primary side hydraulic cylinder 80 is lower than the second line hydraulic pressure Pl2, the first plunger 206 and the second plunger 208 come into contact with each other. , the second plunger 20
A thrust force due to the second line oil pressure Pl2 acting on the end face of the valve 8 acts on the spool valve element 200 in the valve closing direction. That is, the second plunger 208 that receives the primary hydraulic cylinder 80 internal hydraulic pressure Pin and the second line hydraulic pressure Pl2 applies an acting force based on the higher of these hydraulic pressures in the valve closing direction of the spool valve element 200. It is. As a result, the optimum first line oil pressure Pl2 is generated even during positive torque running and negative torque running.

The throttle pressure Pth is the required output, that is, the actual throttle valve opening θ in the engine 10.
It corresponds to th, and the throttle valve opening detection valve 2
28. Further, the gear ratio pressure Pr represents the actual gear ratio of the CVT 16, and is generated by the gear ratio detection valve 232. The throttle valve opening detection valve 228 and the gear ratio detection valve 232 are configured similarly to that described in, for example, Japanese Patent Application Laid-Open No. 64-49749.
is a plunger 230 that engages with a cam surface of a cam (not shown) that is rotated together with the throttle valve of the engine 10.
, and generates a throttle pressure Pth as shown in FIG. 4 in response to a thrust corresponding to the displacement of the plunger 230. The gear ratio detection valve 232 also includes a detection rod 234 that slides on the input side movable rotating body 76 of the CVT 16 and is moved in the axial direction by an amount of displacement equal to the amount of displacement in the axial direction. By changing the relief amount on the downstream side of the throttle 236 in accordance with this, a gear ratio pressure Pr as shown in FIG. 5 is generated.

Here, the gear ratio detection valve 232 generates the gear ratio pressure Pr by changing the release amount of the hydraulic oil of the second line hydraulic pressure Pl2 supplied from the second line oil passage 152 through the throttle 236. Therefore, the gear ratio pressure Pr is limited to a value equal to or higher than the second line oil pressure Pl2. However, in the second pressure regulating valve 150 that operates according to Equation 1, the gear ratio pressure Pr increases as the gear ratio pressure Pr increases. Decrease the 2nd line oil pressure Pl2. For this reason,
The gear ratio pressure Pr increases to a predetermined value and the second line oil pressure P
After that, both become saturated and become constant, and as shown in FIG. 3, the basic output pressure Pme
The change characteristics of c initially decrease linearly in response to an increase in the gear ratio pressure Pr in the process where the gear ratio γ changes from the maximum value to the minimum value, but after reaching the same value as the gear ratio pressure Pr, It becomes a polygonal characteristic with a constant value.

The third pressure regulating valve 240 is connected to the forward/reverse switching device 14.
The hydraulic pressure and first electromagnetic valve 1 actuate the reverse brake 64 and the forward clutch 62 that are frictionally engaged in the
02, third line hydraulic pressure Pl3 that functions as the main pressure lot hydraulic pressure for the second solenoid valve 104 and the linear solenoid valve 106
For example, Japanese Patent Application Laid-Open No. 64-497
The structure is similar to that described in Publication No. 49. The third line oil pressure Pl3 is regulated to an optimal value so that a torque capacity capable of reliably transmitting torque without slipping in the forward clutch 62 or the reverse brake 64 is obtained.

The speed change control valve unit 250 includes a CVT 16
In order to adjust the gear ratio γ of the first line oil pressure Pl1
One and the other of the primary hydraulic cylinder 80 and the secondary hydraulic cylinder 82 are controlled using the second line hydraulic pressure Pl2 as the source pressure. This speed change control valve unit 250 is composed of a speed change direction switching valve 252 and a flow rate control valve 254. Note that the third line oil pressure Pl3 is used as a pilot pressure for driving the speed change direction switching valve 252 and the flow rate control valve 254.

The speed change direction switching valve 252 is the first solenoid valve 102.
The flow control valve 254 includes a spool valve 256 whose position is controlled by the second electromagnetic valve 104 . For example, when the first solenoid valve 102 is in the on state and the second solenoid valve 104 is in the on state, the spool valves 256 and 25
8 are both located on the upper side, so the first line oil passage 1
The hydraulic oil in 44 is supplied to the speed change direction switching valve 252, the first connection oil passage 260, the flow rate control valve 254, and the secondary oil passage 262.
The hydraulic oil in the primary hydraulic cylinder 80 flows through the primary oil passage 264, the flow control valve 254, the second connection oil passage 266, and the speed change direction switching valve. 252 and is discharged to the drain, and the gear ratio γ of the CVT 16 is quickly changed in the deceleration direction.

In this state, when the second solenoid valve 104 is turned off, the spool valve element 258 is positioned at the lower side, so that the first solenoid valve 258 passes through the bypass oil passage 272, which is provided with the one-way valve 268 and the throttle 270 in parallel. The hydraulic oil in the 2-line oil passage 152 is made to flow into the secondary hydraulic cylinder 82, while the hydraulic oil in the primary hydraulic cylinder 80 is discharged to the drain through the gap between the sliding parts, and the gear ratio γ of the CVT 16 is changed.
is gradually changed in the direction of deceleration.

On the other hand, when the first solenoid valve 102 is off and the second solenoid valve 104 is on, the hydraulic oil in the first line oil passage 144 flows through the relatively large throttle 278.
, the shift direction switching valve 252, the second connection oil passage 266, the flow rate control valve 254, and the primary oil passage 264 to flow into the primary hydraulic cylinder 80, while the hydraulic oil in the secondary hydraulic cylinder 82 flows into the secondary hydraulic cylinder 80. Next side oil passage 262, flow rate control valve 254, first connection oil passage 260, and speed change direction switching valve 2
52 and is discharged to the second line oil passage 152, and C
The gear ratio γ of the VT16 is quickly changed in the direction of speed increase.

Furthermore, when the second solenoid valve 104 is turned off in this state, the hydraulic oil in the first line oil passage 144 is
The hydraulic oil in the secondary hydraulic cylinder 82 is caused to flow into the primary hydraulic cylinder 80 through the third connecting oil passage 276 equipped with the speed change direction switching valve 252 and the throttle 274.
The oil is discharged to the second line oil passage 152 through the bypass oil passage 272, and the gear ratio γ of the CVT 16 is gradually changed in the speed increasing direction. Shift control is performed by selectively switching between these four shift modes. Note that ON and OFF given to the first solenoid valve 102 and the second solenoid valve 104 in FIG.
4 corresponds to ON and OFF. Also,
In the first solenoid valve 102 and the second solenoid valve 104, the ball-shaped valve closes the drain port and communicates the input port with the output port in the excited state, and the third line hydraulic pressure Pl
This is a three-way switching valve that outputs 3 and in a non-excited state, the ball-shaped valve closes the input port and communicates the output port with the drain port.

The linear solenoid valve 106 reduces the signal pressure Psol by reducing the third line oil pressure Pl3.
A spool valve element 302 that generates L and is biased in the valve closing direction by a spring 300, an oil chamber 304 that receives a signal pressure PsolL in order to apply feedback oil pressure to the spool valve element 302, and a continuous The solenoid 308 includes a core 306 that applies a thrust in the valve opening direction that changes to the spool valve element 302, and is related to an increase in the current value or voltage value of the drive signal supplied from the transmission electronic control unit 110. signal pressure Ps
It has the characteristic shown in FIG. 6 that continuously increases olL. That is, the biasing force of the spring 300 is WL1
, the pressure receiving area of the spool valve 302 is AL1, and the thrust of the solenoid 306 is FL1, then the above output signal pressure Pso
IL is controlled according to Equation 3.

[0029]

[Math 3]

The engine 10 is a multi-cylinder lean burn internal combustion engine, and the main structure thereof is shown in FIG. In the figure, a pair of exhaust valves 4 are provided for one combustion chamber 400.
02, three first intake valves 404, a second intake valve 406, a third intake valve 408, and one spark plug 410 are provided in the cylinder head, respectively. Exhaust ports opened and closed by the exhaust valve 402 are connected to a common exhaust pipe 412, and the exhaust pipe 412 is provided with a lean mixture sensor 414 and a three-way catalyst 416. This lean mixture sensor 414 has a characteristic that it can detect not only the region near the stoichiometric air-fuel ratio like the conventional oxygen sensor, but also the region leaner than that. Here, the air-fuel ratio is the weight ratio of fuel and air contained in the mixture (weight of air/weight of fuel = A/F) or the weight ratio of gas and fuel in the combustion chamber [(weight of air + circulation Weight of gas)/Weight of fuel = G/F]).

The intake pipe 418 is provided with a helical intake port 420 and a straight intake port 422 substantially parallel to each other.
2 are opened and closed by second intake valves 406, respectively. The fuel intake port 424, which has a smaller flow cross-sectional area than the helical intake port 420 and the straight intake port 422, transfers fuel injected from the fuel injection valve 426 to the ignition plug 410 provided in the center of the combustion chamber 400. The opening thereof is opened and closed by the third intake valve 408. A well-known throttle valve 428 is provided in the intake pipe 418 to control the amount of intake air.

[0032] The straight type intake port 422 has the following:
Additionally, a swirl control valve 430 is provided. This swirl control valve 430 has a link 432
It is designed to be driven by a negative pressure actuator 434 via. Between the first negative pressure tank 436 equipped with a check valve so that the negative pressure in the intake pipe 418 is stored and the negative pressure actuator 434 is a three-way electromagnetic valve whose drive is controlled by the engine electronic control unit 440. A switching valve 438 is provided, and a swirl control valve 430 is opened and closed by an engine electronic control device 440. When the swirl control valve 430 is open, intake air flows into the combustion chamber 40 through the helical intake port 420 and the straight intake port 422.
However, when the swirl control valve 430 is closed, intake air is introduced into the combustion chamber 400 exclusively through the helical intake port 420, so that a strong swirl is generated.

The three first intake valves 404, second intake valves 406, and third intake valves 408 are driven to open and close at predetermined relative timing by a camshaft rotating together with the crankshaft. The valve 408 is the first intake valve 40
The mutual opening and closing timings are set so that the valves are opened near the end of the valve opening period of No. 4. Therefore, a layer of fuel is formed near the upper part of the combustion chamber 400, and ignition becomes stable even if the air-fuel ratio of the air-fuel mixture is lean. Lean burn is considered possible. When the swirl control valve 430 is opened, a large amount of air can be taken in from the intake pipe 418, so that a large output of the engine 10 can be obtained.

Between the intake pipe 418 and the exhaust pipe 412,
An EGR passage 444 with an EGR valve 442 is provided. EGR valve 442 is a well-known negative pressure operated valve, and is controlled by a negative pressure signal output from negative pressure signal generating valve 446. This negative pressure signal generation valve 446 uses the negative pressure in a second negative pressure tank 448 equipped with a check valve for storing the negative pressure in the intake pipe 418 as a source pressure, and also uses the negative pressure from the engine electronic control device 440. Generates a negative pressure signal in response to a control signal.

The engine electronic control device 440 includes:
A signal representing the oxygen concentration from the lean mixture sensor 414, a signal representing the engine rotation speed Ne from the engine rotation sensor 450, a signal representing the throttle valve opening θth from the throttle sensor 452, and an air flow sensor 4.
A signal representing the intake air amount Va from 54, water temperature sensor 4
A signal representative of the engine coolant temperature Tw is supplied from each of the input terminals 56 and 56 . The engine electronic control device 440 is
Similar to the transmission electronic control unit 110 described above, it is a microcomputer including a CPU, ROM, RAM, interface, etc., and controls HC, CO, and N contained in exhaust gas according to a pre-stored program.
In order to reduce Ox and obtain low fuel consumption, a fuel injection valve 426, a three-way electromagnetic switching valve 438, and a negative pressure signal generating valve 4 are installed.
46 respectively.

For example, engine electronic control unit 440
As shown in FIG. 8, the air-fuel ratio is changed from a region leaner than the stoichiometric air-fuel ratio to a region richer than the stoichiometric air-fuel ratio through a stoichiometric region substantially the same as the stoichiometric air-fuel ratio according to the load. EGR depending on the load as shown in Figure 9.
Vary the rate. Note that FIGS. 8 and 9 above show the characteristics when the engine rotational speed Ne is a constant value that is not very high, and as is well known, the above load is determined by the intake air amount Q/Ne, the intake air This corresponds to the pipe negative pressure Pv, the throttle valve opening θth, and the combination thereof with the engine rotational speed Ne or the vehicle speed SPD. According to the control of the engine electronic control unit 440, as shown in FIGS. 8 and 9 above, as the load increases, the air-fuel ratio becomes leaner than the stoichiometric air-fuel ratio.
The stoichiometric combustion, in which the air-fuel ratio is approximately the same as the stoichiometric air-fuel ratio, and the rich combustion, in which the air-fuel ratio is richer than the stoichiometric air-fuel ratio, are performed sequentially.
Further, the EGR valve 442 is controlled so that the EGR rate is maximized on the side where the load is high within the lean burn region.

[0037] Then, the engine electronic control device 44
0, a flag FAF representing the actual air-fuel ratio, a flag FEGR representing the actual EGR rate, and a flag FSCV representing the open/closed state of the swirl control valve 430 are created, and signals representing the contents of these flags are sent to the transmission. Each of the signals is transmitted to the electronic control device 110. That is, in the engine electronic control unit 440, the flag FAF is set to "1" if the actual air-fuel ratio indicated by the AF signal is a value on the leaner side than the stoichiometric air-fuel ratio; If so, its contents are reset to "0". Also, the flag FEGR
is set to "1" if the actual EGR rate indicated by the EGR signal is equal to or higher than a predetermined criterion value, and reset to "0" if it is lower than the criterion value. Ru. This judgment reference value is used to judge whether or not exhaust gas recirculation is being performed, and is, for example, 0.
A small value close to % is set. And the flag FSC
V is the swirl control valve 43 indicated by the SCR signal.
If the opening degree of 0 is greater than or equal to a predetermined criterion value, the content is set to "1", and if it is lower than the criterion value, the content is reset to "0". This determination reference value determines whether the swirl control valve 430 is in an open state or a closed state, and is set to, for example, a value close to 100% and 0%, respectively.

Further, in the control by the engine electronic control unit 440, for example, a predetermined constant judgment reference value (amount of intake air per unit rotational speed of the engine: Q/ The air-fuel ratio is controlled so that the lean combustion state (lean + EGR + SCV closed) and stoichiometric combustion (stoichiometric + EGR + SCV closed) are switched with α as the boundary. On the other hand, the fuel consumption rate SFC (weight/unit work) and the nitrogen oxide emission rate SNOX (weight/unit work) of the engine 10 change according to the change characteristics shown in FIGS. It changes as shown by the solid line in the combustion state, and as shown by the broken line in the stoichiometric combustion state. Therefore, by switching the combustion state at the above-mentioned criterion value α, the lean burn state with an excellent fuel efficiency SFC is selected during light load driving, and the nitrogen oxide emission is selected during medium and high load driving. By selecting a stoichiometric state with an excellent rate SNOX, it is possible to obtain a preferable fuel efficiency rate SFC and nitrogen oxide emission rate SNOX as a whole.

[0039] Transmission electronic control device 1
10 is a speed change control that controls the speed ratio of the CVT 16 to an optimum value corresponding to the running condition of the vehicle, and a transmission belt 70.
The second line oil pressure Pl2, which is the belt tension control pressure, is adjusted such that the tension of
Perform belt tension optimization control as appropriate.

In the above belt tension optimum control, the actual gear ratio γ, engine 1
0 output torque Te (=CVT16 input torque),
The ideal pressure (optimal pressure) Popt is calculated based on the output shaft rotational speed Nout, and the second pressure regulating valve 1
The basic output pressure Pmec of 50 is calculated based on the actual gear ratio γ and the throttle valve opening θth from the pre-stored relationship shown in FIG. 3, for example. Then, the difference between the basic output pressure Pmec and the ideal pressure Popt of the second pressure regulating valve 150, that is, the oil pressure reduction value Pdown to be lowered from the basic output pressure Pmec is calculated from Equation 4. This oil pressure reduction value Pdown is a value for making the second line oil pressure Pl2 coincide with the ideal pressure Popt, and the signal pressure PsolL corresponding to the oil pressure reduction value Pdown is determined from the relationship shown in FIG. 6, and the linear solenoid valve 106
By causing the output from the second line oil pressure Pl2
is made to match the ideal pressure Popt. Note that the second term on the right side of Equation 4 is a correction term for centrifugal oil pressure, and the third term on the right side is a margin value. Also, k1 and k in Formula 4
2 is a constant.

[0041]

[Math 4]

[0042]

[Math 5]

Further, the above-mentioned speed change control can be carried out, for example, as shown in FIG.
As shown in the main part configuration diagram, the surplus torque Te y of the engine 10 in the lean burn state is determined by
00, and when the surplus torque Te y falls below a predetermined value δ, the gear ratio changing means 502 changes the target value Nino of the gear ratio control of the CVT 16 to the deceleration side.

The operation of the shift control described above will be explained in more detail below based on the flowchart shown in FIG. In step S1 of FIG. 14, based on the actual throttle valve opening θth and vehicle speed SPD from a well-known shift diagram determined in advance and stored in the ROM 114, the fuel efficiency and drivability of the engine 10 are obtained. A target input shaft rotational speed Nin° is determined. The speed change diagram is, for example, one selected in advance from a plurality of types of speed change diagrams corresponding to the driving range selected by the shift lever 126, similar to the one described in Japanese Patent Application Laid-Open No. 60-205067. A plurality of data points are stored in the form of a stored data map and intermediate values of the data points are calculated by well-known interpolation calculations.

In step S3 of FIG. 14, step S2
Signal FA from engine electronic control unit 440 received at
The combustion state of the engine 10 is determined from F. That is, it is determined whether the content of the flag FAF indicated by the signal FAF is "1". If it is determined that the content of the flag FAF is not "1", that is, if the engine 10 is not in a lean burn state, the content of the gear ratio change value ΔNin is set to "0" in step S4, and then step S5 In step S6, the contents of the timer counter C are reset to "0", and the flag F1 is reset in step S6.
The contents of are also reset to "0".

Next, in step S7, step S1
By adding the gear ratio change value ΔNin° to the target input shaft rotational speed Nin° determined in , the content of the target input shaft rotational speed Nin° is changed. However, in this case, the contents of the gear ratio change value ΔNin° have been reset to "0" in step S6, so
Even if step 7 is executed, the target input shaft rotational speed Nin° is not changed. In the following step S8, the target input shaft rotation speed N
The difference between in° and the actual input shaft rotational speed Nin, that is, the control deviation ΔNin of the gear ratio feedback control, is calculated, and in step S9, the gear ratio control valve unit 250 is driven so that the control deviation ΔNin is canceled. Ru. That is, one of the speed change modes shown in FIG. 15 is selected according to the control deviation ΔNin, and the first solenoid valve 102 and the second solenoid valve 104 are driven to select that speed change mode.

[0047] When the vehicle is running under a light load, the engine 1
0 is lean-burned, the content of the flag FAF in the engine electronic control unit 440 is "1".
Since the flag F1 is set to "1", the determination in step S3 is affirmative, and in the subsequent step S10, it is determined whether the content of the flag F1 is "1". This flag F
1 indicates that the margin torque Te y in the lean burn state has become smaller than the predetermined value δ when the content is "1". Initially, since the content of the flag F1 is "0", the determination in step S10 is negative, so in the subsequent step S11, the flag F1 -1 in the previous control cycle stored in advance is
It is determined whether the content of is "0" or not. This step S11 is for executing step S12 only once when the engine 10 is switched to lean combustion. Initially, when the engine 10 is switched to lean burn mode, the content of F1-1 is "0", so the determination in step S11 is affirmative, so in step S12 corresponding to the surplus torque determining means 500, the surplus torque Te y (=Te o −Te) is calculated from the output torque Teo at the time of switching between lean combustion and stoichiometric combustion and the actual output torque Te calculated in a step not shown, and the margin torque Te y is calculated based on a predetermined judgment criterion. It is determined whether the value is less than or equal to the value δ. This criterion value δ is a constant value, Q/Ne, θth, P
It is determined according to a function of v or a value thereof and a function of vehicle speed SPD or Ne, and is determined to increase the proportion of lean burn state within a range where the fuel consumption rate SFC and nitrogen oxide emission rate SNOX do not increase beyond predetermined allowable values. is the value given. In addition, the above-mentioned Te o is the above-mentioned judgment reference value α
This is a value uniquely determined corresponding to , and is stored in advance.

If the determination in step S12 is negative, the excess torque Te y is sufficiently large, so steps S4 and subsequent steps are executed. However, step S12
If the determination is affirmative, the surplus torque Te y is insufficient, so in step S13 the content of the gear ratio change value ΔNin° is set to a predetermined increase value β, and in step S14 Flag F1
After the content of is set to "1", the step S7
The following will be executed: Therefore, since the target input shaft rotational speed Nin° is added by the increase value β in step S7, the control deviation ΔNin is expanded by that amount.
In step S9, the gear ratio γ is changed to the deceleration side. As a result, the engine rotational speed Ne is increased on the equal horsepower curve of the engine 10, and the surplus torque Te y
is made larger.

As described above, the contents of flag F1 are changed to "
1", the determination in step S10 of the next control cycle is affirmative, so in step S15 a predetermined constant increase value β is added to the gear ratio change value ΔNin° up to that point. As a result, the contents of the gear ratio change value ΔNin° are changed, and the step S
In step S16, the contents of the timer counter C are updated by adding an additional value "1" to the contents of the timer counter C up to that point, and then in step S17, the contents of the timer counter C are updated to a predetermined judgment reference value CO. It is determined whether or not it has been reached. This criterion value CO is
The deceleration shift time is experimentally set in advance to effectively generate the margin torque Te y , and may be a function similar to the judgment reference value δ.

Initially, when the content of the flag F1 is set to "1", the content of the timer counter C does not reach the predetermined judgment reference value CO, so that the process proceeds to step S17.
If the determination is negative, the steps from step S7 onwards are executed. However, when the time corresponding to the judgment reference value CO has elapsed, the judgment in step S17 is affirmed, so in step S18 the timer counter C and the flag F1 are
After the content of is cleared to "0", the step S7
The following will be executed: In other words, the target input shaft rotational speed Nin° is increased by the time corresponding to the judgment reference value CO and deceleration shifting is performed, so that the engine rotational speed Ne
is increased, and the output torque Te of the engine 10 is changed to the increasing side of the engine rotational speed Ne on the equal horsepower curve, so that the combustion region switching boundary line α (= Te o
) and the equal horsepower curve, the margin torque Te y is sequentially increased as shown in ■, ■, and ■ in FIG. In this sense, the steps S7, S13,
S15 corresponds to the gear ratio changing means 502 for increasing the engine rotational speed Ne to generate surplus torque.

As described above, according to the present embodiment, the margin torque determining means 50 in the lean burn state of the engine 10
When the surplus torque determined by 0 is below the predetermined value δ, the gear ratio changing means 502 changes the gear ratio γ to the deceleration side (
(increasing side). In this way, during the gear ratio control of the CVT 16, the gear ratio γ
When is changed to the deceleration side, the engine rotational speed is increased by that amount on the equal horsepower curve of the engine 10, and as a result, the margin torque Te y is gradually increased. Therefore, by controlling the gear ratio as described above, the frequency of use of the lean combustion of the engine 10 is increased, so that the running fuel efficiency of the vehicle is suitably improved.

Incidentally, in the past, the combustion region was switched at a boundary value corresponding to a constant load value, as shown by α in FIG. If 10-mode fuel efficiency is determined to be optimal, then in LA#4HWY, the proportion of lean burn state will be significantly lower, and another value α' higher than that value α must be set. A sufficient fuel efficiency rate SFC could not be obtained.

Although one embodiment of the present invention has been described above based on the drawings, the present invention can also be applied to other embodiments. For example, in the embodiment described above, the engine 10
When the surplus torque becomes less than the predetermined value δ in the lean burn region of
By changing O, the margin torque Te y
is increased, but the gear ratio γ of the CVT 16 may be forcibly changed from its previous value to the deceleration side by a predetermined amount. Although a certain effect can be obtained even if the amount of change in the gear ratio is a constant value, it may be a function similar to the judgment reference value δ.

Furthermore, in the above embodiment, the target input shaft rotational speed Ni is set as the target value in the gear ratio control of the CVT 16.
n° was used, but the target gear ratio γ° (=Nin/Nout
) may be used. In this case, the actual gear ratio γ
The gear ratio is controlled so that the target gear ratio γ° coincides with the target gear ratio γ°.

Furthermore, in the above-mentioned embodiment, the engine 10 was controlled to have four types of combustion states, but two or three types were controlled.
It may be a type.

Furthermore, in the above embodiment, the engine electronic control device 440 and the transmission electronic control device 1
Although two microcomputers, 10 and 10, were used, one microcomputer having these two functions may be used, or it may be further divided into three or more microcomputers.

Further, in the above embodiment, the forward/reverse switching device 14 was provided at the front stage of the CVT 16, but the CVT 1
It may be provided at a stage subsequent to 6.

Furthermore, in the above embodiment, the second line oil pressure Pl2 regulated by the second pressure regulating valve 150 is:
Although it was applied to the CVT 16 through the speed change control valve unit 250, the secondary hydraulic cylinder 82 of the CVT 16
It may also be a type of hydraulic circuit that acts directly on the hydraulic circuit.

The above-mentioned embodiment is merely one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the configuration of a vehicle power transmission device including an embodiment of the present invention.

FIG. 2 is a diagram showing a partial configuration of the hydraulic control circuit of the embodiment of FIG. 1;

FIG. 3 is a diagram showing the output characteristics of the second pressure regulating valve in FIG. 2;

FIG. 4 is a diagram showing the output characteristics of the throttle valve opening detection valve of FIG. 2;

FIG. 5 is a diagram showing the output characteristics of the gear ratio detection valve of FIG. 2;

6 is a diagram showing the output characteristics of the linear solenoid valve of FIG. 2. FIG.

7 is a diagram showing the configuration of a combustion control device for the engine shown in FIG. 1. FIG.

8 is a diagram showing air-fuel ratio control characteristics of the engine by the combustion control device of FIG. 7. FIG.

9 is a diagram showing EGR rate control characteristics of the engine by the combustion control device of FIG. 7. FIG.

10 is a diagram showing the margin torque Tey in the lean burn region under the control of the combustion control device of FIG. 7; FIG.

FIG. 11 is a diagram showing fuel consumption rate SFC characteristics of the engine in FIG. 1 for each combustion state.

[Figure 12] Nitrogen oxide emission rate SNOX of the engine in Figure 1
FIG. 3 is a diagram showing characteristics for each combustion state.

13 is a diagram illustrating a main part configuration of gear ratio control in the transmission electronic control device of FIG. 1. FIG.

14 is a flowchart showing the operation of gear ratio control in the transmission electronic control device of FIG. 1. FIG.

15 is a diagram showing the relationship between the speed change operation mode and control deviation of the speed change control valve unit in the hydraulic control circuit of FIG. 1. FIG.

[Explanation of symbols]

10 Engine (lean burn internal combustion engine) 16 Belt type continuously variable transmission 110 Transmission electronic control device 500
Surplus torque determining means 502 Gear ratio changing means

Claims (1)

[Claims] Claim 1: A continuously variable transmission for a vehicle equipped with a lean-burn internal combustion engine that can be switched to one of a plurality of combustion states, wherein the lean-burn internal combustion engine operates along a predetermined optimal curve. A control device for adjusting a gear ratio of the continuously variable transmission, the control device comprising: a surplus torque determining means for determining a surplus torque when the lean burn internal combustion engine is in a lean burn region; and a surplus torque determined by the surplus torque determining means. and gear ratio changing means for changing the gear ratio to a deceleration side when the surplus torque of the lean burn internal combustion engine is below a predetermined value. Control device for gear transmission.