JP2519110B2 - Otto-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention increases the expansion ratio to 11 to 16 which is the same as the compression ratio of a diesel engine in an Otto cycle engine, particularly an engine using a Miller cycle together, The present invention relates to an Otto cycle engine in which a compression ratio is raised to a knocking occurrence limit according to an operating state of the engine to increase output and improve combustion.

<Prior Art> A generally well-known Otto cycle engine has a structure in which the compression stroke and the expansion stroke are the same, that is, the compression ratio and the expansion ratio are the same. The compression ratio is limited by knocking that occurs during full-load operation, and is usually about 10 for a non-supercharged engine and about 8.5 for a supercharged engine.
10, the high temperature, high pressure combustion gas generated in the cylinder does not expand sufficiently and is discharged as a high temperature exhaust gas without being converted into an effective work amount, so that the thermal efficiency is low.

As is well known, such high-temperature exhaust gas not only lowers the thermal efficiency, but also increases the thermal stress of the cylinder head, causes cracks, and raises the exhaust valve to a high temperature to lower its strength and sometimes break it. Further, in a supercharged engine, the exhaust temperature becomes higher due to a reduction in the expansion ratio.For example, in the case of exhaust turbo supercharging, excessive thermal stress may be applied to the exhaust turbine casing, etc. and exceed its allowable limit. At present, a rich air-fuel mixture is sucked in to suppress an excessive rise in exhaust temperature, which is a cause of increasing the fuel consumption rate.

To reduce the load in an Otto cycle engine that inhales a mixture of fuel and air with an equivalence ratio,
Throttle valves are used to throttle the amount of air-fuel mixture intake, but the negative pressure of intake air due to these throttle valves not only increases power loss during partial load, but also reduces the density of the compressed air-fuel mixture. As a result, incomplete combustion or a decrease in the combustion speed is caused, and the indicated thermal efficiency is decreased. In particular, when exhaust gas recirculation (hereinafter referred to as EGR) and lean mixture combustion are performed for the purpose of improving thermal efficiency by reducing throttling loss and reducing NOX, combustion failure will occur and HC emissions will increase, but the amount is Of course it was regulated. Further, when starting an engine in a cold region, the compression ratio is not sufficiently high, which makes starting difficult.

<Problems to be Solved by the Invention> In a conventionally known Otto cycle engine (hereinafter referred to as an engine) in which the compression ratio and the expansion ratio are the same, the knocking phenomenon is restricted as described above, and the compression ratio is restricted, and accordingly the expansion ratio is also increased. Due to the restriction, the thermal efficiency at full load decreases, the reliability of the engine decreases due to too high exhaust temperature, and in the case of exhaust turbo supercharging, especially in a supercharging engine with a low compression ratio, the exhaust temperature is even higher. A rich mixture is used to reduce the exhaust temperature, which not only increases fuel consumption but also increases the heat load on the exhaust turbine, forcing the use of expensive heat-resistant alloys for the exhaust turbine and casing. .

Further, when the engine is partially loaded, the density of the compressed air-fuel mixture is reduced, combustion is poor, and thermal efficiency is reduced. Furthermore, the use of EGR and a lean mixture for the purpose of reducing throttling loss and NOx results in poor combustion and the required EG
At present, it is not possible to use an R amount and a sufficiently lean mixture. However, at this time, it is impossible to further improve the thermal efficiency by further increasing the compression ratio, raising the compression temperature, and producing good combustion.

By the way, in Japanese Utility Model Laid-Open No. 64-21223, a rotary valve, which is driven by an engine output shaft to open and close the intake passage, is provided in the intake passage upstream of the intake valve, and the rotary valve is provided coaxially with the valve and rotates integrally. A driven shaft and a drive shaft that is rotationally driven by the engine output shaft and is provided coaxially with the driven shaft, the driving shaft engaging with the driven shaft via an ultrasonic motor, An engine with a rotary valve is disclosed in which the relative angle between the driven shaft and the driven shaft is changed by the ultrasonic motor, and thereby the overlap period in which both the intake valve and the rotary valve are opened is changed.

According to the above invention, the relative angle setting that is inversely proportional to the depression of the accelerator pedal is made by the computer program that is set so that the set relative angle of the ultrasonic motor decreases as the accelerator opening increases, and the intake valve and the rotary valve are set. While changing the overlap period of the valve opening period of
Increase the set relative angle based on an input signal from knocking sensing means such as a knocking sensor or prediction means such as an intake pressure sensor, an intake air temperature sensor and a rotation speed sensor, and stop the cutoff of the rotary valve to reduce the compression ratio. Although knocking is suppressed, it is not practical because it is unknown what value the expansion ratio of the engine should be set to.

In view of the above, the present invention increases the thermal efficiency by adjusting the compression ratio at full load of the engine to be the maximum value restricted by the occurrence of knocking, and setting the expansion ratio to 11 to 16 which is larger than the compression ratio. It was devised for the purpose of improving the thermal efficiency by good combustion even if the exhaust temperature is lowered and the knocking limit at that time is further increased at the time of partial load, even with EGR or a lean mixture, while lowering the exhaust temperature. Is.

<Means for Solving the Problems> An engine configuration according to the present invention for achieving the above object is such that a rotary valve having a valve opening / closing timing adjusting device is provided in an intake passage of the engine, and the valve is installed in the intake air of the engine. By closing before the bottom dead center of the stroke, the expansion ratio of the engine is set to 11 to 16 higher than the compression ratio at full load, while knocking sensing or predicting means is provided to detect this at the early stage of knocking occurrence. Alternatively, by predicting the signal, the closing timing of the rotary valve is advanced through the valve opening / closing timing adjusting device to adjust the substantial compression ratio as high as possible.

<Operation> With the above configuration, when the engine is fully loaded, the rotary valve tends to be operated at the same closing timing as the intake valve of the engine, but at this time, the compression ratio becomes the same as the expansion ratio and is too high. Knocking occurs.

The knocking sensing or predicting means, for example, a knock sensor, senses this immediately, commands the actuator to accelerate the valve closing timing of the rotary valve, and closes this in the middle of the intake stroke to shorten the intake stroke length. While the expansion ratio remains unchanged, the substantial compression ratio falls below the knocking occurrence limit, and knocking is avoided. At this time, the compression ratio drops to the level of a normal engine.

In the case of supercharging, the density and temperature of the compressed air become higher and knocking occurs. Therefore, the closing timing of the rotary valve intake valve is further advanced in cooperation with the knock sensor and the opening / closing timing adjusting device. Although it further lowers the dynamic compression ratio, the expansion ratio is higher than a normal engine and the thermal efficiency is improved.

When the engine is partially loaded, the throttle valve is throttled to reduce the substantial compression ratio and knocking does not occur, and the valve closing timing of the rotary valve can be delayed to increase the substantial compression ratio. By selecting the optimum compression ratio, the good combustion state immediately before knocking is maintained, the indicated efficiency is increased, and the thermal efficiency is improved.

In addition, the EGR reduces the throttling loss, and the use of a lean air-fuel mixture also sucks excess air to reduce the throttling loss, and approaches the air cycle to further improve the thermal efficiency and reduce NOx. In this case, combustion will be poor in a normal engine, but the knock sensor and the opening / closing timing adjusting device cooperate to delay the valve closing timing of the rotary valve to increase the substantial compression ratio and increase the compression density and temperature. Improve combustion.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The Otto cycle engine of the present invention is basically the second
As shown in the figure, the piston 2 slides in the cylinder 1,
In a four-cycle engine in which a crankshaft (not shown) is rotated by a connecting rod 3, a spark plug 5 is faced to the cylinder head 4 thereof, an intake valve 7 and a fuel injection valve 8 are further provided at an intake port 6, Exhaust valve at exhaust port 9
10 are installed respectively, the spark plug 5 performs ignition operation in synchronization with the crankshaft of the engine, and the intake valve 7 and the exhaust valve 10 are also known valve opening / closing mechanisms in synchronization with the crankshaft. The opening and closing timing is set in the same manner as a normal engine.

An intake manifold 12 is provided at one end of an intake branch pipe 11 that communicates with the intake port 6, and an intake passage is formed.

The intake branch pipe 11 has a rotary valve as a control valve.
13 is arranged and driven from the crankshaft through a gear transmission mechanism, and a throttle valve 14 is arranged upstream thereof.

3 and 4 show an opening / closing timing adjusting device including a drive mechanism for the rotary valve 13, and FIG.
Is supported by a rotary valve 13 and a drive shaft 16 fixed by a pin 15 in a valve body 11a formed in the middle of the intake branch pipe 11.

The drive shaft 16 is a rotary valve 1 in the valve body 11a.
It is supported by a plurality of bearings 20, 21 and 22 via a pair of sleeves 17 and 18 and a single sleeve 19 arranged so as to sandwich 3 and a left-handed helical spline 16a is formed at one end thereof. ing.

Reference numeral 23 is a timing gear that is conductively connected to a crankshaft (not shown) through a gear mechanism, and is a rotary shaft integrated with the gear 23.
24 is supported by a bracket 27 attached to the engine via bearings 25 and 26, and a right-handed screw helical spline 24a is formed at the end, and between the left-handed screw helical spline 16a and the above-mentioned splines on the inside. They are connected by an adjusting piece 28 formed with protrusions 28a and 28b that mesh with.

Reference numeral 29 is an adjusting lever, which is supported by a shaft 30, and one end of which is fitted into the recess 28c of the adjusting piece 28. by this,
For example, in the case of FIGS. 3 and 4, if the adjustment lever 28 is moved to the left by the adjustment lever 29, the drive shaft 16 is angularly displaced in a predetermined direction with respect to the rotary shaft 24, and the adjustment piece 28 is moved to the right. With this, angular displacement can be performed in the opposite direction. Thus, the rotation timing of the drive shaft 16 is changed by the axial movement of the adjustment piece 28, and the opening / closing timing of the rotary valve 13 is adjusted.

As shown in FIG. 2, the rotary valve 13 has valve opening / closing timings set at about 90 °, and is driven by the timing gear 23 at a rotation speed half the crankshaft rotation. ing.

On the other hand, the intake stroke period of the engine is 180 ° in crankshaft rotation angle, and therefore the rotary valve 13 has a valve opening period of about 180 ° in crankshaft rotation angle, like the intake valve 7.

FIG. 1 shows a four-cycle Otto-cycle engine of the present invention provided with a rotary valve having the above-mentioned opening / closing timing adjusting device. On the outer wall of the engine E, knocking sensing or predicting means such as a knock sensor 31 is attached. The knock sensor 31 emits a signal in response to engine vibration due to knocking, and this signal is transmitted to the actuator 35 which receives the supply of electric energy from the power source 34 via the wirings 32 and 33.

Upon receiving the knocking signal, the actuator 35 pushes out the rod 36 fixing the pin 37 to the left, rotates the lever 29 clockwise around the shaft 30, pushes the adjusting piece 28 to the right, and as described above. That is, the closing timing of the rotary valve 13 is advanced to reduce the substantial compression ratio of the engine. In the figure, 39 is a crank gear fixed to the front end 38 of the crankshaft, which drives the timing gear 23, and 40 is an exhaust pipe. The supercharging device (turbocharger, supercharger) is not shown because it is a normal one.

As the knocking sensing or predicting means, in addition to the knock sensor 31, a knocking predicting means that operates according to the operating state of the engine, that is, an engine water temperature sensor,
Sensors such as an engine rotation sensor, an accelerator pedal sensor, an O ₂ sensor, etc. that detect the operating condition of the engine and predict knocking (none are shown) can also be used. In cooperation with the opening / closing timing adjustment device, the intake rotary The valve opening timing of the valve 13 can be changed.

In the 4-cycle Otto-cycle engine of the present invention,
In order to minimize the pump loss and maximize the thermal efficiency, the expansion ratio is set to "11 to 16", which is much larger than the normal Otto cycle engine "10", so at full load the rotary valve 13 The actuator tends to be closed at the same time as the intake valve opening / closing timing by the actuator 35, but the compression ratio becomes the same as the expansion ratio, and the compression ratio is too high as it is, and naturally knocking occurs when the engine starts operating. . However, the occurrence of this knocking is immediately sensed by knock sensor 31, and the signal is transmitted to actuator 35. As a result, the actuator 35 moves the rod 36 to advance the closing timing of the rotary valve 13 as described above, and to close the rotary valve 13 during the intake stroke.

The above process will be described with reference to the p-v diagram of FIG. 5. The intake stroke starts at point 1 at the top dead center of the intake stroke, ends at point 7 at the bottom dead center, and starts the compression stroke at point 7. To do. If this compression is continued, it moves as shown by the dotted line, and at the compression top dead center, the air-fuel mixture is adiabatically compressed, the compression pressure becomes point 8, and too high pressure and accompanying high temperature cause knocking. The occurrence of this knocking is immediately detected by the knock sensor 31, and the actuator 35 operates so as to advance the closing timing of the rotary valve 13 in response to the signal, so that the intake passage is closed at point 2 in the intake stroke after the knocking is detected. . Therefore, the pressure at the bottom dead center of the intake stroke gradually decreases from point 7, and in the intake stroke after point 2, the air-fuel mixture in the cylinder expands adiabatically and increases in volume, and at the bottom dead center of the intake stroke, it becomes point 3. The pressure drops below atmospheric pressure. (At this time, the temperature also decreases.) The compression stroke starts at point 3, the pressure becomes atmospheric pressure at point 2, and the temperature rises accordingly, but the substantial compression stroke starts at point 2, Since it ends at the compression top dead center of 4, the substantial compression ratio falls below the knocking limit at that time, the compression pressure falls below points 4 and 8, and at the same time the compression temperature also falls to avoid knocking. It is.

In the conventionally known engine in which the compression ratio is set to "10" for the knocking limit, the expansion ratio is 10 as described above, and the indicated work amount generated in the cylinder is at point 2-4-5-9-2 in Fig. 5. In the case of the engine of the present invention, the expansion stroke is longer than the point 5-6 and the point 5-9 of the normal engine, so the work amount is enclosed by the point 5-4-5-6 in FIG. -7-2 is the area surrounded by the area, so after all, the area surrounded by the point 2-9-6-7-2 (the shaded area) is larger than the normal engine, that is, the work shown in the figure is larger. Although the amount of air-fuel mixture and the amount of fuel supplied are the same between 1 and 2, the output is improved and therefore the thermal efficiency is increased.

When supercharging occurs, knocking is likely to occur due to high intake pressure, but at this time also, the closing timing of the rotary valve 13 is further reduced by the cooperation of the knock sensor 31 and the opening / closing timing adjusting device so as to further reduce the effective compression ratio. Is accelerated, the fifth
Point 2 in the figure is further to the left. At this time, the substantial compression ratio further decreases, but the large expansion ratio does not change, and the thermal efficiency does not decrease and the exhaust gas temperature does not increase.

In other words, the fact that the work amount is large with the same fuel amount as described above means that if the point 9 is further expanded to the point 6, the exhaust gas temperature is lowered and the heat load on each part of the engine can be reduced. I will say.

Further, if the combustion chamber wall temperature is low, such as in an atmospheric condition or an engine operating condition where the compression ratio can be increased, for example, when the temperature of the combustion chamber wall is low, the closing timing of the rotary valve 13 should be delayed to increase the compression ratio. Thus, the engine of the present invention has a function of increasing the intake amount of the engine E and increasing the output.

This indicates that, for example, when accelerating a vehicle after it is stopped, a high output is generated temporarily than during continuous high-load running, and the acceleration capability can be increased.

Next, at the time of partial load, this will be explained with reference to the p-v diagram of FIG. 6 (negative pressure is written on a scale of 5 times positive pressure for easy understanding). The intake air is throttled by, and the intake pressure decreases to point 10 in the intake stroke, and the intake stroke ends at point 12.
The intake air temperature at this time decreases due to adiabatic expansion from point 1 to point 10, but due to the work surrounded by points 1-10-12-13-1, in other words, due to the pressure difference between points 1 and 10. When the accelerated air flow is decelerated, it is converted into heat and returns to the atmospheric temperature again, and the temperature at point 12 becomes approximately atmospheric temperature.
The compression stroke becomes more, the atmospheric pressure is obtained at point 13, and the amount of the air-fuel mixture taken in is converted at atmospheric pressure at points 1-13. At the compression top dead center of point 14, the same compression ratio and the same compression temperature as at full load are obtained, but the density is lower and the combustion speed becomes slower than at full load,
The p-v diagram becomes the point 14-23 of the one-dot chain line in Fig. 6, and the work is lost by the area surrounded by the shaded points 14-15-23-14 (shaded area). The indicated work amount is 13-14-23
The area surrounded by -18-19-13 is the current situation, and the thermal efficiency is decreasing.

In particular, the use of a lean air-fuel mixture with a large EGR or air / fuel ratio for the purpose of pollution control and improvement of thermal efficiency is liable to cause combustion failure, and as shown above, the thermal efficiency shown in the figure decreases and the thermal efficiency at the partial load of the Otto cycle engine The current situation is a factor that hinders improvement.

In the intake stroke of the engine of the present invention, the intake pressure is reduced to a point 20 by the throttle valve 14, and the rotary valve 13 is closed at a point 21 in the middle of the intake stroke, but the piston 2 is further lowered and the air-fuel mixture is adiabatically expanded. The pressure and temperature are reduced, and at point 22, the intake stroke bottom dead center is reached, and the compression stroke is reached. At point 21, the pressure and temperature in the intake state are restored.

For the reason described above, the temperature of the air-fuel mixture at the point 21 is substantially the same as the temperature at the point 12, that is, the atmospheric temperature, and the substantial compression stroke starts at the point 21 and ends at the point 14.

The compression stroke of the engine of the present invention is longer than the compression stroke of the conventional engine 12-14 and the compression stroke of the engine of the present invention is 21-14. It is possible to raise the temperature of the air-fuel mixture at the point 14, that is, the compression top dead center. At this time, if the knock sensor 31 does not detect knocking, the actuator 35 automatically delays the closing of the rotary valve 13 to further lengthen the compression stroke, that is, further increase the compression ratio, and the knock sensor prevents knocking. By sensing and lowering the compression ratio for the first time, the engine of the present invention burns at the maximum allowable burning velocity, which is represented by points 14-15-23 in the pv diagram, and has a long expansion stroke. It expands to point 16 and enters the exhaust stroke from point 17, and the indicated work is the work of throttle loss from the area surrounded by points 13-14-15-16-17-13. 13
It is the area minus the area of -1.

Furthermore, when burning a lean air-fuel mixture by inhaling EGR or excess air for the purpose of pollution control and improvement of thermal efficiency,
Although combustion failure occurs, in the engine of the present invention, by delaying the opening timing of the rotary valve 13 to the knocking limit, the substantial compression ratio is increased up to, for example, point 22 in FIG. It is possible to achieve high combustion efficiency and high thermal efficiency.

The engine of the present invention can achieve high thermal efficiency even at partial load. Similarly, at the time of starting, the engine of the present invention can increase the compression ratio up to the expansion ratio by delaying the closing timing of the rotary valve 13, increasing the compression temperature and facilitating cold start. .

<Effects of the Invention> As described above, according to the present invention, a rotary valve having a valve opening / closing timing adjusting device is provided in the intake passage of the engine, and the valve is closed before the bottom dead center of the intake stroke of the engine. The expansion ratio of 11 is higher than the compression ratio at full load.
On the other hand, a knocking detection or prediction means is provided to detect or predict the knocking at the initial stage of knocking occurrence, and the signal is used to accelerate the closing timing of the rotary valve via the valve opening / closing timing adjusting device. Since it is configured to adjust the substantial compression ratio as high as possible,
The compression ratio of the engine is kept high near the knocking limit according to the operating state at that time, and the thermal efficiency can be improved by the high expansion ratio.

Further, at partial load of the engine, knocking is less likely to occur, and the knock sensor and the actuator delay the closing timing of the rotary valve to increase the compression ratio close to the knocking limit, thereby increasing the EGR rate, or increasing the air / air ratio. Even with an air-fuel mixture having a large fuel ratio, it is possible to increase the combustion speed and, together with the large expansion ratio, improve the thermal efficiency.

Further, if the expansion ratio of the engine of the present invention is set to be about the same as that of a diesel engine, the Otto cycle has higher indicated efficiency than the diesel cycle, and the friction loss of the Otto cycle engine with low combustion pressure is small, and the light piston, Connecting rods and the like can further reduce friction loss and lower the fuel consumption rate compared to diesel engines.

The diesel engine has a larger displacement of NOx, HC, CO, etc. than the Otto-cycle engine using a three-way catalyst, and even if there is no way to resolve the particulates, the engine according to the present invention has higher thermal efficiency than the diesel engine. Not only that, but it also has the great merit of being able to solve the emission control problem.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an Otto cycle engine of the present invention, FIG. 2 is a sectional view of essential parts, FIGS. 3 and 4 are sectional views of a valve opening / closing timing adjusting device, and FIGS. 5 and 6 are present inventions. It is a performance curve figure of an engine. 1; cylinder, 2; piston, 4; cylinder head, 6; intake port, 7; intake valve, 9; exhaust port, 10; exhaust valve, 11; exhaust branch pipe, 1
2; intake manifold, 13; rotary valve, 14; throttle valve,
16; drive shaft, 17, 18, 19; sleeve, 20, 21, 22, 25, 2
6: bearing, 23; timing gear, 24; rotary shaft, 28; adjusting piece, 29; adjusting lever, 31; knock sensor, 35; actuator, 36; rod.

Claims (1)

(57) [Claims] 1. An expansion ratio of an engine at full load is provided by interposing a rotary valve having a valve opening / closing timing adjusting device in an intake passage of the engine and closing the valve before bottom dead center of an intake stroke of the engine. The compression ratio is set to 11 to 16 higher than the compression ratio, and knocking sensing or predicting means is provided, which senses or predicts at the early stage of knocking occurrence, and a signal from the means detects or predicts the rotary timing via the valve opening / closing timing adjusting device. An Otto cycle engine characterized by advancing the valve closing timing and adjusting the substantial compression ratio as high as possible.