JPH03189322A - Otto cycle engine - Google Patents

Abstract

PURPOSE:To improve heat efficiency by means of high expansion and compression ratios by arranging a rotary valve provided with a valve opening/closing timing adjustor at an intake passage of an engine. CONSTITUTION:A rotary valve 13 is arranged at an intake branched pipe 11, and is driven by a timing gear 23 from a crank shaft via a crank gear 39. An actuator 35 moves an adjusting piece 28 to an axial direction via a rod 36 an adjusting lever 29 to change the rotation timing of a driving shaft 16 so as to adjust the opening/closing timing of a rotary valve 13. An expansion ratio of an engine E is set higher than the compression ratio at the time of full load operation by closing the rotary valve 13 just before a bottom dead center of intake stroke. The expansion ratio is sensed and predicted by a knocking sensor 31 at the beginning of knocking generation, and the closing timing of the rotary valve 13 is quicken via an actuator 35 by the signal so as to adjust a substantial compression ratio. The expansion and compression ratios are raised, and heat efficiency is improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention improves thermal efficiency in an Otto cycle engine, especially in an engine that uses a Miller cycle, by increasing the expansion ratio to the limit of knocking depending on the load. This relates to an Otto cycle engine.

<Prior Art> A generally well-known Otto cycle engine and a diesel engine both have a structure in which the compression ratio and the expansion ratio are set to be the same. The above compression ratio is limited by the knocking that occurs during full-load operation, and the limit for non-supercharged engines is usually around 10. Therefore, the expansion ratio is also 10, and the high temperature and high pressure combustion gas generated in the cylinder is sufficiently expanded. The heat is discharged as high-temperature exhaust gas without being converted into useful work, resulting in low thermal efficiency.

As is well known, such high-temperature exhaust gas not only reduces thermal efficiency, but also increases thermal stress in the cylinder head, causing cracks, and also makes the exhaust valve hot, reducing its strength.
Sometimes it breaks. Also.

In the case of exhaust turbocharging, an excessive heat load is applied to the exhaust turbine, casing, etc., which also has a negative impact on reliability.

In an Otto cycle engine that inhales a mixture of fuel and air close to the equivalence ratio, a throttle valve is used to throttle the engine's mixture intake in order to reduce the load. Throttling not only increases power losses at part load, but also causes a reduction in the density of the compressed air-fuel mixture and therefore incomplete combustion or a reduction in the combustion rate, reducing the indicated thermal efficiency.

<Problems to be Solved by the Invention> Conventionally known Otto cycle engines (hereinafter referred to as engines) in which the compression ratio and expansion ratio are the same are constrained by the knocking phenomenon as described above, and the compression ratio is limited and the In the case of exhaust turbocharging, the heat load on the exhaust turbine increases and the use of expensive heat-resistant alloys for the exhaust turbine and casing becomes necessary. I am forced to do so.

Furthermore, when the engine is under partial load, the density of the compressed air-fuel mixture decreases, poor combustion occurs, and thermal efficiency decreases. However, at this time, it is currently impossible to further increase the compression ratio, increase the compression temperature, produce good combustion, and improve thermal efficiency.

In view of the above, the present invention sets the compression ratio at full load of the engine to the maximum value limited by the occurrence of knocking, and sets an expansion ratio larger than the compression ratio to increase thermal efficiency and lower exhaust temperature. This was devised for the purpose of further increasing the compression ratio to the knocking limit at that time and improving the indicated thermal efficiency through good combustion.

Means for Solving the Problems> The configuration of the engine of the present invention to achieve the above object is such that the expansion ratio of the engine is set higher than the compression ratio at full load, and the intake passage of the engine is provided with valve opening/closing timing adjustment. A rotary valve equipped with a device is installed, and a knock sensor is provided, and the knock sensor detects knocking at an early stage when knocking occurs, and the signal is used to advance the closing timing of the rotary valve via the valve opening/closing timing adjusting device. 6 <Operation> With the above configuration, when the engine is at full load, the rotary valve is operated at the same valve closing timing as the engine intake valve. However, at this time, the compression ratio becomes the same as the expansion ratio, which is too high and causes knocking.

The knock sensor immediately senses this and instructs the actuator to tighten the valve closing timing of the rotary valve, closing it in the middle of the intake stroke and shortening the length of the intake stroke, so that the actual compression ratio is reduced. knocking is avoided. At this time, the compression ratio is reduced to that of a normal engine, but the expansion ratio is higher than that of a normal engine, and thermal efficiency is improved.

When the engine is under partial load, the actual compression ratio decreases by throttling the throttle valve and knocking does not occur, and the compression ratio can be increased by delaying the valve closing timing of the rotary valve. By selecting , a good combustion state immediately before knocking is maintained, the indicated efficiency is increased, and thermal efficiency is improved.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings.

The Otto cycle engine of the present invention is basically a four-stroke engine in which a piston 2 slides within a cylinder 1 and a crankshaft (not shown) is rotated by a connecting rod 3, as shown in FIG. cylinder head 4
An ignition plug 5 is located facing the cylinder, an intake valve 7 and a fuel injection valve 8 are located at the intake port 6, and an exhaust valve 1 is located at the exhaust port 9.
The spark plug 5 performs ignition operation in synchronization with the crankshaft of the engine, and the intake valve 7 and exhaust valve 1o also operate in synchronization with the crankshaft using a well-known valve opening/closing mechanism. The opening and closing timing is set in the same way as a normal engine.

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

A rotary valve 13 as a control valve is disposed in the intake branch pipe 11, and is driven from the crankshaft via a gear transmission mechanism, and a throttle valve 14 is disposed upstream thereof.

3 and 4 show the drive 4i of the rotary valve 13.
! The rotary valve 13 is a valve body 1a formed in the middle of the intake branch pipe 11.
Drive shaft 1 fixed with rotary valve 13 and bottle 15 inside
6 is supported.

This drive shaft 16 is connected to a pair of sleeves 17 disposed to sandwich the rotary valve 13 within the valve body 1a.
．． 18 and a single sleeve 19 on a plurality of bearings 20, 21 and 22, and a left-handed helical spline L6a is formed at one end thereof.

Reference numeral 23 denotes a timing gear that is conductively connected to a crankshaft (not shown) via a gear mechanism, and a rotating shaft 24 integrated with the gear 23 is supported by a bracket 27 attached to the engine via bearings 25 and 26. At the same time, a right-handed helical spline 24a is formed at the end, and is connected to the left-handed helical spline 16a by an adjustment piece 28 that has protrusions 28a, 28b formed inside to engage with the plane spline.

An adjustment lever 29 is supported by a shaft 30, and one end thereof is fitted into the recess 28c of the adjustment piece 28. As a result, in the case of FIGS. 3 and 4, for example, if the adjustment piece 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 rotating shaft 24, and the adjustment piece 28 is moved to the right. By moving it, it is possible to cause an angular displacement in the opposite direction.

In this way, by moving the adjustment piece 28 in the axial direction, the drive shaft 1
By changing the rotation timing of the rotary valve 13, the opening and closing timing of the rotary valve 13 is adjusted.

As shown in FIG. 2, the rotary valve 13 has opening and closing timing set at approximately 90° intervals, and is driven by the timing gear 23 at a rotation speed of 1/2 of the crankshaft rotation. ing.

On the other hand, the intake stroke period of the engine is approximately 180 degrees in terms of crankshaft rotation angle, and therefore, like the intake valve 7, the rotary valve 13 has an open period of approximately 180'' in terms of crankshaft rotation angle.

FIG. 1 shows a four-stroke automatic cycle engine according to the present invention, which is equipped with a rotary valve having the above-mentioned opening/closing timing adjustment device.A knock sensor 31 is attached to the outer wall of the engine E. FIG. The knock sensor 31 emits a signal in response to engine vibration caused by knocking, and this signal is transmitted via wiring 32, 33 to an actuator 35 that receives electrical energy from a power source 34.

Upon receiving the knocking signal, the actuator 35 pushes out the rod 36 to which the pin 37 is fixed to the left, rotates the lever 29 clockwise around the shaft 30, and moves the adjustment piece 2
8 to the right, the closing timing of the rotary valve 13 is shifted to V as described above, and the effective compression ratio of the engine is lowered. 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 I [trachea.

Next, the operation of the above embodiment will be explained.

In the four-stroke Otto cycle engine of the present invention, the expansion ratio is set to, for example, "11 to 16", which is much larger than "10" of a normal Otto cycle engine, and the rotary valve 13 is The actuator 35 tries to close the closing timing at the same time as the opening/closing timing of the intake valve, but the compression ratio becomes the same as the expansion ratio, and if left as it is, the compression ratio will be too high, and knocking will naturally occur when the engine starts operating. However, the occurrence of knocking is immediately sensed by the knock sensor 31, and the signal is transmitted to the 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, so that the rotary valve 13 closes in the middle of the intake stroke.

To explain the above process using the p-v diagram in Figure 5, intake begins 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. do. If this compression is continued, the transition will be as shown by the dotted line, and at compression top dead center, the air-fuel mixture will be adiabatically compressed, and the compression pressure will be at point 8, and excessively high pressure and accompanying high temperature will cause knocking. The occurrence of this knocking is immediately sensed by the knock sensor 31, and the actuator 35 operates to advance the closing timing of the rotary valve 13 in response to the signal.

The intake passage is closed at point 2 in the middle of the intake stroke after 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 from point 1 to 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 reaches point 3. The pressure drops below atmospheric pressure. (At this time, the temperature also decreases.) The compression stroke starts from point 3, the pressure becomes atmospheric pressure at point 2, and the temperature rises accordingly, but the actual compression stroke starts from point 2, and the pressure reaches atmospheric pressure at point 2. 4, the compression ends at the second dead center, so the actual compression ratio is lowered, the compression pressure is lower than at points 4 and 8, and at the same time the compression temperature is lowered to avoid knocking.

In a conventionally known engine in which a compression ratio of "10" is set as the non-king limit, the expansion ratio is also 10 as described above.
The indicated amount of work generated in the cylinder is point 2-4-5 in the 5th figure.
-9-2, but in the case of the engine of the present invention, the expansion ratio is large, so the indicated work is the area surrounded by point 2 in Figure 5.
The area is surrounded by -4-5-6-7-2. Here, the area surrounded by points 2-7-3-2, that is, the amount of work lost due to early closure of the intake passage, is so small that it can be ignored, so the area surrounded by points 2-9-6-7-2 ends up being The area, that is, the indicated work is larger than that of a normal engine by the amount indicated by the shaded line, and the thermal efficiency is increased even though the amount of air-fuel mixture supplied between points 1 and 2 and the amount of fuel used are the same.

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

Furthermore, under atmospheric conditions or engine operating conditions that can increase the compression ratio, for example, when the combustion chamber wall temperature is low such as during light load operation of the engine, the closing timing of the rotary valve 13 may be delayed to increase the compression ratio. Accordingly, the engine of the present invention has a function of increasing the intake air amount of the engine E and increasing the output.

This means, for example, when accelerating a car from a stop,
This shows that it is possible to temporarily generate higher output than during continuous high-load driving and increase acceleration ability.

Next, during partial load, this can be explained using the p-v diagram in Figure 6 (for ease of understanding, negative pressure is drawn on a scale of five times the positive pressure).In conventionally known engines, the throttle valve The intake air is throttled, and the intake pressure drops to point 10 during the intake stroke, and the intake stroke ends at point 12. At this time, the intake air temperature decreases due to adiabatic expansion from point 1 to point 10, but due to the amount of work surrounded by 1 point 1-1o-12-13-1, in other words, due to the pressure difference between point 1 and point 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, and the compression stroke starts from point 12, and at point 13 it becomes atmospheric pressure, and the temperature at point 1 -13 is the amount of air-fuel mixture inhaled in terms of atmospheric pressure. At the second dead center of compression at point 14, the compression ratio and compression temperature are the same as at full load, but the density is lower and the combustion speed is slower than at full load, and the p-V diagram is 1 in Figure 6. The dotted chain line points 14-23, and the diagonally shaded point 14-
Work is lost by the area surrounded by 15-23-14 (shaded line), and the indicated work at this time is point 13-14-2.
Currently, the area is surrounded by 3-18-19-13, and the thermal efficiency is decreasing.

In the intake stroke of the engine of the present invention, the intake pressure is lowered to point 20 by the throttle valve 14, and the rotary valve 13 is closed at point 21 in the middle of the intake stroke.
The piston 2 further descends, the air-fuel mixture expands adiabatically and lowers its pressure and temperature, reaches the bottom dead center of the intake stroke at point 22, changes to the compression stroke, and returns to the intake state pressure and temperature at point 21.

For the aforementioned reasons, the temperature of the air-fuel mixture at point 21 is approximately the same as point 12, ie, the atmospheric temperature, and the substantial compression stroke begins at point 21 and ends at point 14.

The compression stroke of the engine of the present invention is longer at point 21-14 compared to point 12-14, which is the compression stroke of a conventionally known engine.
Based on the premise that the combustion chamber volumes of both engines are the same, the compression ratio is high and it is possible to increase the air-fuel mixture temperature at point 14, that is, compression top dead center. If the knock sensor 31 does not detect knocking at this time, the actuator 3
5 automatically further delays the closing of the rotary valve 13 to further lengthen the effective compression stroke, that is, further increase the compression ratio, and lower the compression ratio only after the knock sensor detects knocking, thereby achieving the present invention. The engine burns at the maximum allowable combustion speed, and if expressed on a p-v diagram, points 14-15-23 appear, and the expansion stroke is also long.
It expands to point 16, enters the exhaust stroke from point 17, and the indicated work is the work of the aperture loss from the area surrounded by points 13-14-15-16-17-13, which is point 1-20-21-.
The area is obtained by subtracting the area of 13-1.As mentioned above, the area of the throttling loss is exaggerated by a factor of five, and the throttling loss essentially reduces the partial load thermal efficiency of the Otto cycle engine. In the engine of the present invention, high thermal efficiency can be obtained even under partial load.'' Similarly,
At the time of starting, the engine of the present invention can increase the compression ratio to the expansion ratio by delaying the closing timing of the rotary valve 13, increasing the compression temperature and facilitating low-temperature starting.

<Effects of the Invention> As described above, the present invention sets the expansion ratio of the engine higher than the compression ratio at full load, and interposes a rotary valve equipped with a valve timing adjustment device in the intake passage of the engine. A knock sensor is provided, and the knock sensor detects knocking at the initial stage of occurrence, and the signal is used to adjust the closing timing of the rotary valve via the valve opening/closing timing adjustment device. Therefore, the engine compression ratio is maintained close to the knocking limit, and the actual compression ratio is adjusted.
A high expansion ratio can improve thermal efficiency.

In addition, under partial load of the engine, knocking is less likely to occur, and the knock sensor and actuator delay the closing timing of the rotary valve, increasing the compression ratio to near the knocking limit, thereby increasing the combustion rate and increasing the expansion ratio. Together, the thermal efficiency can be increased.

Furthermore, if the expansion ratio of the engine of the present invention is the same as that of a diesel engine, the Otto cycle engine has higher indicated efficiency than the diesel cycle, and the Otto cycle engine with lower combustion pressure not only has less friction loss but is also lighter. Pistons, connecting rods, etc. can further reduce friction loss and lower fuel consumption than diesel engines.

Diesel engines emit more NOx, HC, Go, etc. than otto cycle engines that use three-way catalysts.
Nowadays, there is no prospect of a solution to the problem of particulate matter, but the engine according to the present invention not only has higher thermal efficiency than a diesel engine, but also has the great advantage of being able to solve the problem of emission control.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of the automatic cycle engine of the present invention, Fig. 2 is a sectional view of the main parts, Figs. 3 and 4 are sectional views of the valve timing adjustment device, and Figs. FIG. 3 is a performance curve diagram of the invention engine. 1; cylinder, 2; piston, 4; cylinder head, 6; intake port, 7; intake valve, 9; exhaust port, 10; exhaust valve, 11; intake branch pipe, 12; intake manifold, 13; rotary valve, 14 ;throttle valve, 16
; Drive shaft, 17.18.19; Sleeve, 20.21.22.25.26: Bearing, 23; Timing gear, 24; Rotating shaft, 28; Adjustment piece, 29; Adjustment lever 31; Knock sensor, 35; Actuator, 36; rod. Figure 3 27 4a Figure 4

Claims (1)

[Claims] The engine expansion ratio is set higher than the compression ratio at full load,
A rotary valve equipped with a valve timing adjustment device is installed in the intake passage of the engine, and a knock sensor is installed, and the knock sensor detects knocking at an early stage when knocking occurs, and uses the signal to adjust the valve timing adjustment device. The Otto cycle engine is characterized in that the closing timing of the rotary valve is advanced through the method to adjust the substantial compression ratio.