JPH07156693A - Power unit for vehicle - Google Patents

Abstract

PURPOSE:To markedly improve fuel consumption by using a gasoline engine with exhaust turbosupercharger and an automatic transmission, achieving reducing the fuel consumption in a low speed high load side of the engine, and also more using this operating region. CONSTITUTION:An exhaust turbosupercharger 15 is provided in an engine, to increase a mean effective pressure while decreasing a loss by resistance of the supercharger so that fuel consumption in a low speed high load region is reduced, to also use a continuously variable transmission in a speed changer 25 connected to the engine, and by setting a speed change ratio control characteristic of the continuously variable transmission so that steady running, when on a flat road, can be performed in at least a low speed region in a supercharge region, this region is more used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle power unit including a gasoline engine with a supercharger and an automatic transmission.

[0002]

2. Description of the Related Art Generally, a vehicle power unit includes an engine and a transmission. Various types are known in which the engine in the power unit of this vehicle is provided with a supercharger to improve the output by supercharging the intake air (see, for example, JP-A-1-104920).

[0003]

Conventionally, the engine provided with the supercharger is mainly intended to increase the output, and the fuel economy has not been sufficiently devised. Some supercharged engines are expected to have a certain fuel consumption reduction effect by setting the air-fuel ratio to a lean side when the load is high (see, for example, JP-A-3-23327). However, there was room for improvement because the low fuel consumption area was not always effectively utilized.

In view of the above-mentioned circumstances, the present invention aims to reduce the fuel consumption of an engine by utilizing an exhaust turbocharger having a particularly low resistance among the turbochargers, and to effectively utilize the low fuel consumption region. It is an object of the present invention to provide a vehicle power unit that can significantly improve fuel efficiency.

[0005]

In order to achieve the above object, the present invention provides a gasoline engine with an exhaust turbocharger, and a transmission connected to the engine is a continuously variable transmission for operation. The gear ratio control characteristic that changes the gear ratio of the continuously variable transmission according to the state is set so that steady running is performed on a flat road in the low speed region of the supercharging region.

In the present invention, at least the supercharging region of the engine (the region where the pressure immediately before the intake valve is equal to or higher than atmospheric pressure).
The same applies to the following), the intake valve closing timing is set late so that the effective compression ratio of the engine becomes smaller than the expansion ratio in the operating range from the low speed region to the high speed region. It is preferable to set the closing timing in crank angle to 50 ° or more after bottom dead center.

Further, it is preferable to set the geometrical compression ratio of the engine to 9 or more.

[0008]

According to the present invention, as will be described later in detail, the fuel consumption becomes low in the operation range on the low speed and high load side, and the average effective pressure is increased by supercharging, and the exhaust gas turbocharger of low resistance is used. As a result, fuel consumption is sufficiently reduced, and since the continuously variable transmission controls the gear ratio according to the gear ratio control characteristic, the low fuel consumption region is frequently used. Further, the exhaust turbocharger is inferior to the mechanical turbocharger in low speed torque and response, but by supplementing this with the gear ratio control of the continuously variable transmission, good acceleration performance and the like can be obtained.

Further, if the intake valve closing timing is set late so that the effective compression ratio of the engine becomes smaller than the expansion ratio in at least the operating range from the low speed region to the high speed region of the supercharging region of the engine, the temperature rises during compression. Is suppressed and knock resistance in the supercharging region is enhanced, which is advantageous for suppressing knocking in the supercharging region that is frequently used by the control of the continuously variable transmission.

Further, if the geometrical compression ratio is 9 or more, the expansion ratio is increased to improve the thermal efficiency, which also reduces the fuel consumption.

[0011]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 schematically shows a power unit of a vehicle according to an embodiment of the present invention. The engine (gasoline engine) in this power unit has an engine body 1, an intake passage 10, an exhaust passage 12, and the like. The engine body 1 includes a plurality of cylinders 2, and an intake port 4 and an exhaust port 5 are opened in a combustion chamber 3 of each cylinder 2, and in the illustrated example, two intake ports 4 and two exhaust ports 5 are opened. ing. The intake ports 4 and the exhaust ports 5 are opened and closed by intake valves 6 and exhaust valves 7, respectively. The intake port 4 is connected to the intake passage 11 for each cylinder on the downstream side of the intake passage 10, and the exhaust port 5 is connected to the exhaust passage 13 for each cylinder on the upstream side of the exhaust passage 12.

Further, the engine has an exhaust turbocharger 15
Is provided. The exhaust turbocharger 15 includes a turbine 15a arranged in the exhaust passage 12 and an intake passage 10
And a compressor 15b connected to the turbine 15a via a shaft 15c. The turbine 15a is rotated by exhaust energy, and the compressor 15b is rotated in conjunction therewith to supercharge intake air. It has become.

The compressor 1 in the intake passage 10
An intercooler 16 for cooling the supercharged air is provided downstream of 5b.
Is provided. Further, in the intake passage 10, an air cleaner 17, an air flow meter 18 for detecting the intake flow rate,
A throttle valve 19 for adjusting the intake flow rate according to accelerator operation and the like, an injector 20 for injecting and supplying fuel, and the like are provided.

A transmission 25 is connected to the output shaft of the engine.
The final reducer 26 is connected to the output side of the
A wheel 28 is connected to the wheel via an axle 27.

FIG. 2 shows the structure of the transmission 25, which is composed of a continuously variable transmission. In this embodiment, a toroidal type continuously variable transmission 40 is used.
It is configured using. That is, the transmission 25 is connected to the output shaft of the engine to perform a torque increasing action, the planetary gear mechanism 31 as a speed reducer to which the output of the torque converter 30 is transmitted, and the rotation of the engine. Toroidal-type continuously variable transmission 4 that receives the input of
It has 0 and.

The planetary gear mechanism 31 comprises a forward planetary gear mechanism 32 and a reverse planetary gear mechanism 33. The sun gear 34 shared by these is connected to the turbine shaft 35 of the torque converter, while the forward planetary gear mechanism 31 is connected. Gear mechanism 3
The second ring gear is connected to the output shaft 50 via the forward clutch 36 and the one-way clutch 37, and the ring gear of the reverse planetary gear mechanism 33 is connected to the output shaft 50 via the reverse clutch 38.
It is possible to switch between forward and reverse by the operation of 6, 38.

Further, the continuously variable transmission 40 has a first transmission unit 41 and a second transmission unit 42, and these transmission units 41, 42 have the same structure, and each of the output shafts has the same structure. An input disc 43 rotatably provided on the shaft 50 and the input disc 43;
And an output disk 44 which is arranged to face the output shaft 50 and rotates integrally with the output shaft 50, and a pair of rollers 45 which are arranged between the input / output disks 43 and 44. The roller 45
Is rotated in contact with both disks 43 and 44 so as to transmit the rotation of the input disk 43 to the output disk 44, and is tiltable. Then, the roller 45 is tilted by a hydraulic drive mechanism (not shown) and its installation angle is changed, so that the contact position of the roller 45 with respect to both the disks 43 and 44 is displaced, and the gear ratio is changed. It has become so.

The input disks 43 of the transmission units 41 and 42 are arranged adjacent to each other, and an intermediate disk 46 is arranged between the input disks 43. The intermediate disk 46 and the input disks 43 are arranged between the input disks 43. In addition, a loading cam 47 that applies a pressing force corresponding to the input torque to the input disk 43 is interposed.

In order to input the engine output to the input disk 43 of the continuously variable transmission 40, an input shaft 51 is arranged in parallel with the output shaft 50, and a first gear 52 is provided on one end side of the input shaft 51. A gear 55 is provided, which is connected to a hollow shaft 53 directly connected to the input side of the torque converter 30 via a switching clutch 54, and an idle gear 56 meshes with the gear 55.
The first gear 52 is in mesh with 6. The input shaft 51
A second gear 57 is provided on the other end side of the second gear 57.
A gear 58 provided on the intermediate disk 46 meshes with the gear 7.

According to the transmission 25, when the switching clutch 54 is released, the hollow shaft 5 is released.
The transmission of rotation between the engine 3 and the input shaft 51 of the continuously variable transmission 40 is cut off, and the engine output is transmitted to the output shaft 50 via the torque converter 30 and the planetary gear mechanism 31. on the other hand,
When the switching clutch 54 is engaged, the engine output is transmitted from the hollow shaft 53 to the input shaft 51 and then to the output shaft 50 via the continuously variable transmission 40. When the vehicle is traveling normally except when moving backward or starting, the switching clutch 5 is
By controlling a hydraulic drive mechanism (not shown) that tilts the roller 45 in the state where 4 is fastened, the gear ratio can be changed according to the traveling state.

Control of the gear ratio and the like in the transmission 25 and control of the engine are performed by a control unit (ECU) 60 shown in FIG.
The control unit 60 includes the air flow meter 18, a throttle opening sensor 61 for detecting the opening of the throttle valve, an engine speed sensor 62 for detecting the engine speed, and a sensor 6 for detecting the output shaft speed of the transmission.
The signal from 3rd grade is input. And the above ECU
The engine control unit 60 controls the fuel injection amount from the injector 20 and controls the gear ratio of the continuously variable transmission 40 according to a running condition according to a preset gear ratio control characteristic. Has become.

In this power unit, the geometric compression ratio of the engine is larger than the geometric compression ratio of a general supercharged engine (8.5 or less), and is set to a high compression ratio of 9 or more.

Further, the intake valve closing timing is set so that the effective compression ratio becomes smaller than the expansion ratio at least in the low speed region in the supercharging region. In this embodiment, as shown in FIG. 3, the exhaust valve is set to open near the bottom dead center and closed near the top dead center so that the expansion ratio becomes a substantially geometric compression ratio, while the intake valve It is set to open near top dead center and close at a certain time later than bottom dead center. Specifically, the intake valve closing timing IC defined with a 1 mm lift is 50 degrees or more after bottom dead center in crank angle. It is set late. By delaying the intake valve closing timing to this extent, the blowback of the intake occurs at the end of intake, and the effective compression ratio becomes sufficiently smaller than the expansion ratio, and the knocking suppression effect described later is effectively obtained. It is what is done.

In this embodiment, the opening / closing timing of the intake / exhaust valve is fixed, but a valve timing variable mechanism for changing the opening / closing timing of both the intake valve and the intake / exhaust valve is provided, and at least The opening / closing timing may be controlled according to the operating state while making the effective compression ratio smaller than the expansion ratio in the low speed region of the supercharging region. Further, as the setting such that the effective compression ratio becomes smaller than the expansion ratio, the intake valve closing timing may be set earlier than the bottom dead center.

On the other hand, the characteristics of the continuously variable transmission are set so that steady running is performed on a flat road in the low speed region of the supercharging region.

That is, in controlling the continuously variable transmission,
For example, as shown in FIG. 4, a map of the gear ratio control characteristic in which the output rotation speed and the throttle opening are associated with the input rotation speed (engine rotation speed) is set, and the actual output rotation speed and the throttle are set based on this map. The gear ratio is controlled according to the opening. In this case, the continuously variable transmission has a relatively high degree of freedom in setting the gear ratio control characteristic, and thus the engine operating state during steady running can be adjusted relatively freely.

Therefore, the gear ratio control characteristic is set so that steady running is performed on a flat road in the low speed and high load region. That is, in the map of the operating state shown in FIG. 6 which will be described in detail later, the line A (line indicated by a thick solid line) passing through the low speed and high load region is set as the steady running line, and the operating state is set to the above line by controlling the gear ratio. The gear ratio control characteristic of the continuously variable transmission is set so as to follow A.

The low speed region is a region where the engine speed is at least 3000 rpm (1/2 of the rated speed) or less.

According to the power unit of this embodiment as described above, the fuel consumption is greatly improved, and its operation will be described below.

The indicated fuel consumption rate (fuel consumption rate of the work for the piston) is bi, the average effective pressure is Pe, and the friction loss average effective pressure (the average effective amount of loss due to friction of sliding parts such as pistons and driving of various auxiliary machines). If the pressure) is Pf, the net fuel consumption rate be of the engine be is as follows.

[0031]

[Equation 1] be = {(Pe + Pf) / Pe} × bi Therefore, in order to reduce the net fuel consumption rate be, the indicated fuel consumption rate bi is decreased, the average effective pressure Pe is increased, and the friction loss effective pressure Pf is increased. You can make it smaller.

FIG. 5 shows the relationship between the axial torque of the engine and the resistance torque corresponding to the friction loss effective pressure Pf in the case of a naturally aspirated engine without a supercharger and with a mechanical supercharger. It shows the case of the engine and the case of the engine provided with the turbocharger. As shown in this figure, in the case of a naturally aspirated engine, the resistance torque decreases as the shaft torque increases. When the mechanical supercharger is provided, the resistance torque increases as the shaft torque increases. On the other hand, when the turbocharger is provided, the resistance torque of the turbocharger is small when the axial torque is large because the turbocharger has low resistance.

Comparing the various engines in terms of fuel consumption based on the above equation 1 and FIG. 5, first, in the case of a naturally aspirated engine, the larger the axial torque of the engine, the larger the average effective pressure Pe and the friction loss effective pressure. As Pf becomes smaller, {(Pe + Pf) /
Pe} becomes small. However, in a naturally aspirated engine, it is necessary to increase the amount of fuel and enrich the air-fuel ratio in order to earn axial torque at high load, which results in the indicated fuel consumption rate b.
Since i becomes large, the net fuel consumption rate be becomes large.

Further, in the case of an engine with a mechanical supercharger, since the filling amount is increased by supercharging, a torque equivalent to that of a naturally aspirated engine with a large displacement can be obtained even with a small displacement. However, when the shaft torque increases, the friction loss effective pressure Pf increases, which is disadvantageous for reducing fuel consumption.

On the other hand, in the case of the turbocharged engine, the average effective pressure Pe can be sufficiently increased while keeping the indicated fuel consumption rate bi small by supercharging.
The turbocharger has lower resistance than the mechanical supercharger,
Even if the shaft torque increases, the effective friction loss pressure Pf does not increase. Therefore, in the high torque range, the net fuel consumption rate be
Will be significantly reduced.

Further, since the effective compression ratio is made smaller than the expansion ratio by delaying the intake valve closing timing, and the geometric compression ratio is made high, it becomes even lower. Fuel consumption is improved.

That is, if the intake valve closing timing is delayed and the intake valve closing timing defined for a lift of 1 mm is set to 50 ° or more after the bottom dead center at the crank angle, the effective compression ratio is sufficiently higher than the expansion ratio. It becomes smaller, the temperature rise due to compression is suppressed, and the knock resistance is improved. The fuel consumption is further improved by increasing the expansion ratio while improving the knock resistance in this way.

Further, FIG. 6 shows a constant fuel consumption rate line of the net fuel consumption rate (a large number of curves shown by thin solid lines) and a steady running line (thick solid line) A by the gear ratio control characteristic of the continuously variable transmission as described above. And a steady running line (one-dot chain line) B by setting of a conventional general transmission using a manual transmission and the like, and an equal horsepower line (a large number of curves shown by broken lines).

As shown in this figure, the net fuel consumption rate becomes low in the low speed and high load range, and in particular, as described above, the turbocharger 1
By supercharging at 5, the high-load side region of the supercharging region in the low speed region is the optimum fuel consumption region (the net fuel consumption rate is the minimum value b
This is the region where min is reached), and the net fuel consumption rate in this region is significantly reduced.

In the power unit of the present embodiment, the characteristic of the gear ratio of the continuously variable transmission 40 is set so that the steady running line A passes through the low speed region in the supercharging region, so that the fuel efficiency is greatly improved. The effect is obtained.

That is, in order to improve the fuel consumption, it is required to drive a large amount in a driving region where the net fuel consumption rate is small. However, according to the conventional general setting, the steady running line B is larger than the optimum fuel consumption region. Since the driving range is far away, the frequency of use of the driving range having a small net fuel consumption rate is reduced. On the other hand, in the present embodiment, the continuously variable transmission is used, the gear ratio control characteristic thereof is adjusted, and the steady running line A is set to pass through the low speed region in the supercharging region.
The frequency of driving in the low fuel consumption region where the net fuel consumption rate is low increases.

Further, the turbocharger 15 is inferior to the mechanical supercharger in terms of low-speed torque and response, but
This is supplemented by the gear ratio control of the continuously variable transmission 40. Specifically, when the throttle opening (accelerator pedal depression amount) is increased, the gear ratio is changed by the gear ratio control of the continuously variable transmission 40 in accordance with the increase, that is, the load. As the engine speed is increased in accordance with the increase of, the horsepower is increased as compared with the case where only the load is increased. Therefore, even if the supercharging response is poor, the horsepower is earned by the increase in the number of revolutions due to the change in the gear ratio, and the low speed traveling performance and the acceleration performance are secured.

The specific structure of the power unit of the present invention is not limited to the above-mentioned embodiment, but various modifications can be made. For example, in the above embodiment, the transmission is provided with the toroidal type continuously variable transmission 40, but a belt type continuously variable transmission may be used.

[0044]

According to the present invention, an exhaust gas turbocharger is provided in an engine, and a transmission connected to the engine is constituted by a continuously variable transmission, and its gear ratio control characteristics are controlled in a low speed range in the supercharging range. Since it is set to perform steady running on a flat road, supercharging boosts the effective compression ratio while maintaining low resistance loss by using an exhaust turbocharger. It is possible to sufficiently reduce the fuel consumption in the low fuel consumption region existing in the low speed region of the region, and moreover, the low speed region of the supercharging region where the fuel consumption is low is often used by the gear ratio control based on the above characteristics of the continuously variable transmission Therefore, the fuel consumption reduction effect can be sufficiently exerted. In addition, the turbocharger is inferior to the mechanical supercharger in low-speed torque and response, which is compensated by the control of the continuously variable transmission, and the acceleration performance and the like in the low-speed range can be improved.

Further, as described in claim 2, it is set so that the effective compression ratio becomes smaller than the expansion ratio at least in the high load region, and, for example, as described in claim 3, the intake air of the engine defined when the lift is 1 mm. If the valve closing timing is set to 50 ° or more after the bottom dead center in the crank angle, knocking in the high load range where supercharging is performed can be sufficiently suppressed, and the above effect can be effectively exhibited. .

Further, when the geometrical compression ratio of the engine is set to a high compression ratio of 9 or more as described in claim 4, thermal efficiency can be improved and fuel consumption can be further reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an overall structure of a power unit according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a transmission.

FIG. 3 is an explanatory diagram showing valve timing.

FIG. 4 is an explanatory diagram showing a control map of the continuously variable transmission.

FIG. 5 is a diagram showing a relationship between an engine axial torque and a resistance torque.

FIG. 6 is a diagram showing a steady running line, an equal fuel consumption line, and an equal horsepower line.

[Explanation of symbols]

 1 Engine Main Body 6 Intake Valve 10 Intake Passage 12 Exhaust Passage 15 Exhaust Turbocharger 25 Transmission 40 Toroidal Continuously Variable Transmission 60 Control Unit

Claims (4)

[Claims] 1. A gasoline engine equipped with an exhaust turbocharger, the transmission connected to the engine is a continuously variable transmission, and the gear ratio of the continuously variable transmission is changed according to operating conditions. A power unit for a vehicle, wherein a ratio control characteristic is set so that steady running is performed on a flat road in a low speed region in a supercharging region. 2. The intake valve closing timing is set to be late so that the effective compression ratio of the engine becomes smaller than the expansion ratio in at least the operating range of the supercharging range of the engine from the low speed range to the high speed range. Item 2. A vehicle power unit according to item 1. 3. The intake valve closing timing defined for a 1 mm lift is set to 50 ° or more after bottom dead center in crank angle as a setting for making the effective compression ratio of the engine smaller than the expansion ratio. The power unit for a vehicle according to claim 1 or 2. 4. The power unit for a vehicle according to claim 3, wherein the geometric compression ratio of the engine is set to 9 or more.