JPS6022030A - Variable compression ratio engine - Google Patents

Abstract

PURPOSE:To obtain a variable compression ratio engine which is simple in structure and excellent in durability and reliability, by connecting a cylinder block and a crankcase or the like by the intermediary of a shape memory alloy that is expansible in the axial direction of a cylinder. CONSTITUTION:A shape memory alloy 1 is fixed between the lower portion of flange 3 formed to extend outward from the lower outer wall of a cylinder block 2 of an engine and the top 4a of a crankcase 4 respectively by means of bolts 5, 6. The shape memory alloy 1 is so designed that it is expanded when the temperature is higher than the critical temperature and contracted when the temperature is lower than the critical temperature. With such an arrangement, it is enabled to increase the compression ratio at the time of starting the engine by making the shape memory alloy 1 take its low-temperature shape. On the other hand, when warmingup of the engine is completed, the compression ratio is lowered to such an extent as not to cause knocking by making the shape memory alloy 1 take its high-temperature shape.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable compression ratio engine capable of changing the compression ratio of an engine or diesel engine.

It is generally said that the higher the engine compression ratio, the better in terms of startability and fuel efficiency, but this increases the likelihood of knocking. Therefore, it is preferable to set the compression ratio high at startup, and after the engine has moved to the first stage, set the compression ratio high enough to prevent knocking.

Conventional variable compression ratio engines are, for example, 5AEPaper
770430, which hydraulically moves the piston ring carrier above the piston pin carrier up and down, and S'A E Paper 77
0114, in which the stroke is changed by a link mechanism, is known.

However, these conventional devices have a complicated structure, and the actuating part for switching the compression ratio is provided on a moving part such as a piston or crank, so there is a problem with itl stability, and the inertial mass is large. This prevents the engine from rotating at high speeds.

The object of the invention is therefore that the structure f\ij il'
Another object of the present invention is to provide a novel variable compression ratio engine in which the actuating part for switching the compression ratio is not located in a moving part such as a piston.

The above-mentioned object of the present invention is to join a cylinder block and a crankcase or a cylinder head with a shape memory alloy which is made to have shape memory so that it contracts at a low temperature side of a specific temperature and expands at a high temperature (III) in the axial direction of the cylinder. This is achieved by

Hereinafter, the present invention will be explained with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, in which FIG. 1 (4) shows a state at a high compression ratio, and FIG. 1 (B) shows a state at a low compression ratio. The shape memory alloy 1 is applied to an eave 3 that is formed to protrude from the outer wall of the lower part of the cylinder block 2 of the engine.
and the top 4α of the crankcase 4 by ports 5 and 6, respectively. shape memory alloy 1
may be provided around the entire circumference of the joint between the cylinder block 2 and the crankcase 4, but may also be provided only on both sides thereof.

In the latter case, it is necessary to provide a sliding member or the like to make the joint part not provided with the shape memory alloy expandable and retractable. Similarly, if the shape memory alloy is not provided between the cylinder block 2 and the crankcase 4 but is provided on the outer wall of the joint between the cylinder block 2 and the cylinder head 7, it will slide against the cylinder block 2 in the cylinder axial direction. For example, the cylinder may be fixed to the cylinder head 7 so that it can be moved, and a shape memory alloy may be provided on the outside of the cylinder. This is to ensure the shape and sealing of the combustion chamber 9 between the upper surface of the piston 8 and the cylinder head 7.

As for the shape of the shape memory alloy 1, in addition to the bellows shown in the figure, other shapes such as a coil can be used.

The bellows-shaped shape memory alloy lid is heated to a temperature higher than the specific temperature (martensite transformation start temperature) of the alloy.
It is stored in a reduced shape as shown in Figure (4). The temperature at the outer wall of the joint between the cylinder block 2 and the crankcase 4 at the end of warm-up is approximately 100°C, so at around room temperature when the engine is started, it assumes the shape on the low temperature side shown in (A), and the engine warm-up ends. In some cases, a shape memory alloy having martensitic transformation temperature characteristics such as the shape shown in (B) on the high temperature side is used. The compression ratio - becomes high in the low-temperature side shape shown in FIG. 1(4), and becomes low in the high-temperature side shape shown in FIG. 1(B). Therefore, when starting the engine, the length L (A
), the compression ratio becomes high, and at the end of warm-up, the high temperature side shape of (B) with length L+4L is obtained, and the compression ratio is suppressed to a low level to prevent the occurrence of wood cracking.

The compression ratio is the ratio between the volume of the combustion chamber 9 when the piston 8 is at the bottom dead center and the volume of the combustion chamber 9 when the piston 8 is at the top dead center. This is about 10 for gasoline engines and about 20 for diesel engines. The volume is
If the area is constant, it is determined by the height, so for example, if the piston stroke is 63 nirn and the height to the remaining cylinder head is 7 mrn, the compression ratio is (63 nirn).
+7 )/7 = 10, and the elongation amount aL == l due to the shape change of the shape memory alloy 1 shown in FIG. 1(B)
In mm, it becomes (63+8)/8#9. Similarly, in the case of a diesel engine, for example, (95+5
)15 = 20 becomes (9
5+6)/6=17. In this way, if the position of the 7 cylinder block 2 becomes l nun higher due to the shape change of the shape memory alloy 1, the compression ratio can be changed by about 3 for a gasoline engine or an 11 diesel engine.

Shape memory alloys include so-called unidirectional ones, which return to the high-temperature shape when heated, but do not return to the low-temperature shape when cooled, and those that are reversible to the low-temperature and high-temperature shapes by repeated cooling and heating. There are two types: bidirectional, which returns to the target, and omnidirectional, which sequentially changes its shape in response to temperature changes.

In this invention, when using a unidirectional shape memory alloy, a spring bias is required to return it to the shape on the low temperature side. If a bidirectional shape memory alloy is used, the compression ratio will be switched in two stages. On the other hand, if an omnidirectional shape memory alloy is used, the compression ratio can be adjusted steplessly.

In order to make large or small changes in the compression ratio of two or more steps using a bidirectional shape memory alloy, the martensitic transformation temperature characteristics must be adjusted sequentially as shown in Figure 2 (A). A plurality of shape memory alloys La, 1b,
1c may be formed continuously into a bellows shape, for example. In this way, when starting the engine, the
When the engine is operated at a high compression ratio as shown in 4) and gradually warms up, the first shape memory alloy 1α expands as shown in FIG. ) as in the second. The third profile 1.8 alloys 1b and 1c are sequentially elongated to obtain an elongation amount of JLI +aL2+4L3 as a whole. This allows large or small changes in the compression ratio.

The above embodiment is an example in which the shape memory alloy 1 naturally changes its shape in accordance with the temperature change of the outer wall of the cylinder block 2, but this temperature change is artificially controlled to change the shape of the shape memory alloy. An example in which this is forcibly performed is shown in Figures 3 and below. In the example shown in FIG.
is fixed between the eaves 3 and the top of the crankcase 4,
Hot air or exhaust gas is blown onto this circular folded part to forcibly heat it. In the example shown in FIG. 4, a rhombic pipe-shaped shape memory alloy 1'' is used, and cooling water 10 is introduced into the inside for forced cooling.If such forced heating or forced cooling means is provided, compression This has the advantage of not only being able to artificially control changes in the ratio, but also widening the degree of freedom in selecting the shape memory alloy to be used. The heater 11, which is placed close to the shape memory alloy l or in contact with it through an insulating material, is energized by the output signal of the engine control unit EcU, which receives signals such as water temperature, engine speed, throttle opening, and intake air amount. As the heater 11, a nichrome wire, a ceramic heater, etc. may be used, or if a Peltier effect element is used,
It is more effective because heating and cooling can be selectively performed by changing the direction of the current flowing. When performing such temperature control, the base compression ratio for the low-temperature side shape should be set higher than for normal conditions, and this can be used when knocking, noise, or exhaust gas characteristics deteriorate. It is preferable to detect this and heat the shape memory alloy to lower the compression ratio.

As described above, the variable compression ratio engine of the present invention has a simple structure and the compression ratio changing mechanism is provided in a non-moving part, so startability, fuel efficiency, one-stop reliability, etc. are significantly improved. . Furthermore, since the compression ratio can be changed in multiple stages or in a stepless manner according to temperature changes, the ability to follow the engine is improved. Furthermore, control by a combeater is also possible, making it possible to optimally control the compression ratio.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a variable compression ratio engine according to the invention, and FIGS. 2 to 5 are diagrams showing only essential parts of different embodiments of the invention. l Shape memory alloy, 2... cylinder block, 3-...
Eaves, 4 Crankcase, 5, 6 Wheels 1-. 7 No'J head, 8 Piston, 9 Combustion chamber, 1″0
Cooling water, 11 heater.゛Form 1 (c) l'F). (A) rf3> (Bacteria (B) 2ba (C,> (D)

Claims (1)

[Claims] A variable compression ratio engine characterized in that the cylinder block and the crankcase or cylinder head are joined in the axial direction of the cylinder by a shape memory alloy that contracts at a specific temperature on the low temperature side and expands on the high temperature side. .