JP7305930B2 - rotary piston engine - Google Patents

Description

The present invention relates to rotary piston engines.

A rotary piston engine has a combustion chamber formed between a rotor and a rotor housing having a trochoidal inner peripheral surface. A recess that forms a combustion chamber is formed on the outer peripheral surface of the rotor. Regarding this rotor recess, Patent Document 1 describes a recess consisting of a first recess located on the trailing side in the rotor rotation direction and a second recess located on the leading side following the first recess. . Combustion stability of the engine is enhanced by making the cross-sectional area of the first recess perpendicular to the rotor circumferential direction smaller than that of the second recess. That is, when the air-fuel mixture flows from the trailing side to the leading side, turbulence is easily generated at the connection portion from the first recess to the second recess where the cross-sectional area of the recess changes, and the air-fuel mixture is mixed and It is intended to promote diffusion.

JP 2015-78664 A

By the way, in a rotary piston engine, it is known that when EGR is introduced, the combustion center of gravity is retarded and the thermal efficiency is lowered. Possible solutions to this problem include advancing the ignition timing and shortening the ignition delay period (the period from ignition to the start of apparent heat generation). However, in the case of a rotary piston engine, unlike a reciprocating engine, due to its structure, the heat transfer from the flame to the combustion chamber wall surface tends to increase in the initial stage of combustion after ignition. Therefore, it is difficult to secure ignition robustness in advanced ignition, and it is difficult to shorten the ignition delay period.

In general, it is known to decrease the surface area/volume ratio of the combustion chamber to reduce the cooling loss in order to improve the combustibility or thermal efficiency of the engine. However, in the case of a rotary piston engine, it is difficult to achieve advance ignition and shorten the ignition delay period simply by reducing the surface area/volume ratio of the combustion chamber.

Therefore, in a rotary piston engine, the present invention makes it possible to shorten the advance ignition and the ignition delay period, thereby improving the thermal efficiency by advancing the combustion center of gravity.

In order to solve the above problems, the present invention defines a predetermined virtual flame in a rotary piston engine, and forms a rotor recess based on this virtual flame so as to suppress wall heat transfer in the early stage of combustion. .

The rotary piston engine disclosed herein includes a rotor housing having a substantially elliptical trochoidal inner peripheral surface, side housings disposed on both sides of the rotor housing and forming rotor housing chambers together with the rotor housing, and rotor housing chambers. It is housed in a rotor housing chamber and partitions three working chambers in the rotor housing chamber, and while each working chamber is moved in the circumferential direction by rotation, each stroke of intake, compression, expansion and exhaust is sequentially performed in each working chamber. and spark plugs provided in the rotor housing, wherein recesses are formed in respective outer peripheral surfaces of the rotor that define the working chambers,
A conical portion that spreads conically from the ignition point in the direction of rotation of the rotor and a hemispherical bulge from the tip of the conical portion, which is caused by the ignition of the air-fuel mixture before the top dead center of the compression stroke by the spark plug. When defining a virtual flame consisting of a part, the height L of the cone part is 17.5 mm, and the radius r of the bottom surface of the cone part and the radius r of the hemispherical bulge part are 12.5 mm,
At 49° before top dead center of the compression stroke, the virtual flame geometrically interferes with the rotor and the rotor housing. ³ ), and the S/V ratio is 0.13 or more and 0.2037 or less, where S (mm ² ) is the total area of the surface where the virtual flame contacts the rotor and the rotor housing, A recess is formed in the rotor.

Here, when the air-fuel mixture is ignited before the top dead center of the compression stroke, the flame propagates radially, and the squish flow of the air-fuel mixture from the trailing side to the leading side in the rotor rotation direction causes the center of the flame to rotate the rotor. move in the direction Therefore, the shape of the flame in the early stage of combustion after ignition expands conically from the ignition point of the spark plug in the moving direction due to the squish flow, and the tip surface swells into a hemispherical shape due to flame propagation. Based on this, the shape of the virtual flame is determined as described above. The height L of the virtual flame cone corresponds to the moving distance of the center of the flame in the direction of rotation of the rotor, and the radius r of the bottom surface and hemispherical portion of the virtual flame cone corresponds to the propagation distance of the flame.

When the virtual flame geometrically interferes with the rotor and rotor housing, heat is transferred to the rotor and rotor housing from the interfering portions. This is cooling loss. Then, at 49° before the top dead center of the compression stroke, when the volume of the portion of the virtual flame that does not interfere with the rotor and rotor housing is V, and the total area of contact with the rotor and rotor housing is S, S/V A ratio of 0.2037 or less means that the cooling loss from the flame at the initial stage of combustion is small. This reduction in wall heat transfer makes it easier for the flame to grow, ensuring robust ignition even if the ignition timing is greatly advanced, and is advantageous in shortening the ignition delay period. Therefore, when EGR is required, it becomes easier to optimize the center of gravity of combustion by adjusting the ignition timing, which is advantageous for improving thermal efficiency.

The lower limit of the S/V ratio can be set to 0.13. This lower limit is the case where the virtual flame does not interfere with the rotor, but only with the rotor housing.

In one embodiment, the recess in the outer peripheral surface of the rotor includes a leading-side concave portion extending forward in the rotational direction from the center in the longitudinal direction of the outer peripheral surface, and a concave portion extending forward in the rotational direction from the center in the longitudinal direction of the outer peripheral surface. an extending trailing side recess,
The leading side recess has a larger volume than the trailing side recess.

As a result, the volume V of the portion of the virtual flame that does not interfere with the rotor and the rotor housing becomes larger than when the volumes of the leading-side recess and the trailing-side recess are equal, so that the S/V ratio can be reduced. will be advantageous.

In one embodiment, the leading-side recess includes a recessed deep portion that is the deepest at a center corresponding to the ignition point of the spark plug, and the deep portion is deeper than the trailing-side recess and the virtual It is wider than the diameter of the hemispherical bulging portion of the flame and formed into a concave curved surface having a radius of curvature larger than the radius of the bulging portion. As a result, the area of contact with the rotor can be reduced while the volume V of the virtual flame is increased, which is advantageous in reducing the S/V ratio.

In one embodiment, the working chamber has a geometric compression ratio of 9.7 or greater. While setting the geometric compression ratio of the working chamber to 9.7 or more, as described above, the S/V ratio is set to 0.2037 or less, so the engine combustion pressure is converted to the rotation of the output shaft. It is possible to suppress the cooling loss while securing the effective efficiency, and thus the thermal efficiency can be increased.

According to the present invention, the S/V ratio, which is the ratio of the area S in contact with the rotor and rotor housing to the volume V of the portion of the virtual flame that does not interfere with the rotor and rotor housing, is 0.2037 or less. Since the cooling loss from the flame is reduced, the ignition robustness is improved and the ignition delay period is shortened, making it easier to optimize the combustion center of gravity by advancing the ignition timing, which is advantageous for improving thermal efficiency. become.

BRIEF DESCRIPTION OF THE DRAWINGS The perspective view which shows the outline|summary of the rotary piston engine which concerns on embodiment of this invention. The front view which shows the rotor and rotor housing of the engine. The top view which shows the outer peripheral surface of the same rotor. FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 3; FIG. 4 is a cross-sectional view taken along the line VV of FIG. 3; FIG. 3 is a sectional view taken along the line VI-VI of FIG. FIG. 4 is a graph showing cross-sectional areas of recesses on each part of the outer peripheral surface of the rotor. A perspective view of a virtual flame. Sectional drawing which shows the interference state of a virtual flame, a rotor, and a rotor housing in BTDC49 degree. Sectional drawing which shows a rotor, a rotor housing, and a virtual flame in BTDC24 degrees. FIG. 10 is a diagram showing the recess shapes of Comparative Examples 1 and 2 and Examples 1 and 2, and the state of interference between a virtual flame, a rotor, and a rotor housing; FIG. 10 is a diagram showing recess shapes of Examples 3 to 6, and interference states between a virtual flame, a rotor, and a rotor housing; FIG. 4 is a graph showing the relationship between the S/V ratio and the V/Vt ratio; FIG. 10 is a graph showing the heat release rates of Comparative Example 1 and Example 7; FIG. 4 is a graph showing the relationship between the S/V ratio and the fuel efficiency improvement rate; 4 is a graph showing the relationship between the V/Vt ratio and the fuel efficiency improvement rate;

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated based on drawing. The following description of preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its applications or uses.

<Overall Configuration of Rotary Piston Engine>
A rotary piston engine 1 (hereinafter simply referred to as engine 1 ) shown in FIG. 1 is mounted on a vehicle and includes two rotors 2 . An intermediate housing 4 is provided between two rotor housings 3 each containing a rotor 2 . Side housings 5 are provided on both outer sides of the two rotor housings 3 . Focusing on one rotor housing 3, the intermediate housing 4 is located on one side of the rotor housing 3 and can be positioned as a side housing that forms a rotor housing chamber 31 together with the rotor housing 3 and the side housing 5. .

In FIG. 1, a portion of the front side (right side in FIG. 1) of the engine 1 is cut away to show the inside of the engine. showing. Symbol X in the drawing is the rotational axis of the eccentric shaft as the output shaft.

As shown in FIG. 2, the rotor housing 3 has a trochoidal inner peripheral surface 3a that is substantially elliptical (barrel-shaped) when viewed from the direction of the rotation axis X drawn by parallel trochoidal curves. As shown in FIG. 1, the inner peripheral surface of the rotor housing 3, the inner side surfaces 4a on both sides of the intermediate housing 4, and the inner side surfaces 5a of the side housing 5 form a rotor housing chamber 31. The rotor housing chamber 31 accommodates the rotor 2. is accommodated. The rotor housing chambers 31 on both sides of the intermediate housing 4 have the same configuration except that the rotors 2 have different rotational phases.

The rotor 2 has a substantially triangular shape in which the central portion of each side bulges outward when viewed from the direction of the rotation axis X, and a recess 7 is formed in the substantially rectangular outer peripheral surface 2a between the tops of the triangle. there is Apex seals 9 provided at the triangular tops of the rotor 2 come into sliding contact with the trochoidal inner peripheral surface 3a of the rotor housing 3 as the rotor 2 rotates. The rotor 2 partitions the interior of the rotor housing chamber 31 into three working chambers 8, as shown in FIG.

The rotor 2 is supported by the eccentric ring 6a of the eccentric shaft 6, and while rotating, revolves around the rotation axis X in the same direction as the rotation (including this rotation and revolution, in a broad sense, simply the rotor 2 rotation). During one rotation of the rotor 2, the three working chambers 8 move in the circumferential direction, and respective strokes of intake, compression, expansion (combustion), and exhaust are performed. The rotational force generated thereby is output from the eccentric shaft 6 via the rotor 2 .

In FIG. 2, the rotor 2 rotates clockwise as indicated by an arrow, and the left side of the rotor housing chamber 31 divided by the long axis Y passing through the rotation axis X is generally the intake stroke and the exhaust stroke. The area on the right side is generally the area for the compression stroke and the expansion stroke.

As shown in FIG. 1, intake ports 11 to 13 and an exhaust port 10 are opened at portions of the inner surface 4a of the intermediate housing 4 and the inner surface 5a of the side housing 5 corresponding to the areas of the intake stroke and the exhaust stroke. ing. Although not shown, a fuel injection valve for injecting fuel into the working chamber 8 during the intake stroke or compression stroke is provided at the top of the rotor housing 3 .

As shown in FIG. 2, leading-side spark plugs are installed at leading-side and trailing-side positions in the rotor rotation direction with the short axis Z of the rotor housing chamber 31 passing through the rotation axis X on both sides of the rotor housing 3 . 91 (hereinafter referred to as "L side spark plug 91") and a trailing side spark plug 92 (hereinafter referred to as "T side spark plug 92") are mounted. Note that the long axis Y and the short axis Z are orthogonal to each other.

Although not shown, the rotary piston engine 1 includes an EGR device for recirculating part of the exhaust gas to the intake passage, and the recirculation of the exhaust gas is performed according to the engine operating state.

The rotary piston engine 1 also includes a control unit as a control section for controlling the operations of the engine, including the operations of the intake throttle valve, the fuel injection valve, the spark plugs 91 and 92, and the EGR device.

<About control unit>
The control unit is based on a microcomputer, and includes a central processing unit (CPU) that executes programs, a memory that stores programs and data, for example, RAM and ROM, and a signal input/output (I /O) bus. The control unit receives signals of various information from a vehicle accelerator opening sensor, vehicle speed sensor, engine rotation angle sensor, air-fuel ratio sensor, engine coolant temperature sensor, air flow sensor, and the like.

The control unit determines the operating state of the engine 1 based on the input signal, and determines the opening of the throttle valve, the EGR rate by the EGR device, the L side and T side in each working chamber 8, and The ignition timing by the spark plugs 91 and 92, the fuel injection amount by the fuel injection valve, and the fuel injection timing are controlled.

As for the ignition timing, the ignition timing by the L-side spark plug 91 is set in the range of BTDC (before top dead center of the compression stroke) 15° or more and 55° or less, which is on the advance side of the ignition timing by the T-side spark plug 92, Based on the setting, the energization timing of the L side and T side ignition coils is controlled.

The ignition timing by the L-side spark plug 91 is controlled according to the EGR rate so that the center of gravity of combustion is positioned at an appropriate position of 10° to 30° ATDC (after top dead center in the compression stroke) with high thermal efficiency. 2, when one of the apexes of the rotor 2 is positioned on the opposite side of the spark plugs 91 and 92 on the minor axis Z, the working chamber located on the opposite side of the apex is Compression stroke top dead center.

The higher the EGR rate, the longer the ignition delay period and the more retarded the center of gravity of combustion. Therefore, the ignition delay period is set according to the EGR rate, and the target heat generation start timing (apparent heat generation start target timing) is set according to the EGR rate. Then, the ignition timing of the L-side spark plug 91 is set to the timing advanced by the ignition delay period from the target heat generation start timing.

Also, the ignition timing of the L-side spark plug 91 is corrected according to the engine load (the opening of the throttle valve) and the engine speed. That is, the ignition timing is retarded as the engine load increases, and advanced as the engine speed increases.

The ignition timing of the T-side spark plug 92 is controlled to be retarded by a predetermined angle from the ignition timing of the L-side spark plug 91 .

<Regarding the rotor recess>
As shown in FIG. 3, the recess 7 formed in the outer peripheral surface 2a of the rotor 2 extends long in the rotor rotation direction. The recess 7 includes a leading side concave portion 7a (hereinafter referred to as "L side concave portion 7a") extending forward in the rotor rotation direction from the longitudinal center of the outer peripheral surface 2a, and the outer peripheral surface 2a continuing from the L side concave portion 7a. T-side recesses 7b (hereinafter referred to as "seven T-side recesses") extending forward in the rotor rotation direction from the center of the rotor. The volume of this recess 7 is set so that the geometric compression ratio of the working chamber 8 is 9.7 or more.

In a plan view of the outer peripheral surface 2a of the rotor 2, the width of the L-side recessed portion 7a gently widens forward in the rotor rotation direction, and the tip thereof has an arc shape. In other words, the L-side concave portion 7a has a bulb-like shape that expands forward in the rotor rotation direction. On the other hand, the T-side recessed portion 7b continues to the narrowed base portion of the L-side recessed portion 7a and extends forward in the rotor rotation direction with the same width. extends linearly in the width direction of the

The length L1 of the L-side recess 7a extending forward in the rotor rotation direction from the longitudinal center of the outer peripheral surface 2a is the length of the T-side recess 7b extending forward in the rotor rotation direction from the longitudinal center of the outer peripheral surface 2a. It is longer than L2. The distance Ld between the tip of the L-side concave portion 7a in the rotor rotation direction and the tip of the outer peripheral surface in the rotation direction is 5/100 or more and 15/100 or less of the length Lo of the outer peripheral surface 2a in the rotor rotation direction. In order to make the S/V ratio described later smaller than that of Comparative Example 1, the preferable Ld/Lo ratio is 5/100 or more and 12/100 or less. A preferable Ld/Lo ratio is 7/100 or more and 10/100 or less.

As shown in FIGS. 4 to 6, the L-side recessed portion 7a has a deep portion 15 which is recessed so that the center corresponding to the ignition point of the L-side spark plug 91 is the deepest. The deep portion 15 is deeper than the T-side concave portion 7b, and is formed into a concave curved surface that gradually becomes shallower toward both sides in the width direction of the outer peripheral surface 2a of the rotor 2 and forward in the rotor rotation direction. The width W1 of the deep portion 15 is larger than the width W2 of the T-side recess 7b, and is also larger than the diameter of the hemispherical swelling portion of the imaginary flame, which will be described later. Also, the radius of curvature of the deep portion 15 is larger than the radius of the hemispherical bulging portion.

FIG. 7 shows changes in the cross-sectional area of the recess 7 in the longitudinal direction of the outer peripheral surface 2a of the rotor 2 (cross-sectional area perpendicular to the rotating direction of the rotor).

The cross-sectional area of the L-side concave portion 7a is 20/100 of the total length of the leading side (the length from the longitudinal center to the front end of the outer peripheral surface 2a) forward in the rotor rotation direction from the longitudinal center of the outer peripheral surface 2a. It has a small cross-sectional area that is substantially constant up to the vicinity, and after that vicinity, the cross-sectional area gradually increases, reaches a maximum in the vicinity of 50/100 of the total length on the leading side, and then gradually decreases. The cross-sectional area of the T-side concave portion 7b extends from the center in the longitudinal direction of the outer peripheral surface 2a toward the front side in the direction of rotation of the rotor over the entire length of the trailing side (the length from the center in the longitudinal direction of the outer peripheral surface 2a to the rear end). From about 20/100 to about 30/100, the cross-sectional area is substantially the same as the small cross-sectional area of the L-side concave portion 7a, and beyond that area, the cross-sectional area gradually decreases.

Regarding the L-side recessed portion 7a, a starting point for increasing the cross-sectional area is provided in a range of, for example, 15/100 or more and 30/100 or less of the total length on the leading side, with the longitudinal center of the outer peripheral surface 2a as a base point. It is preferable to provide it in the range of 50/100 or more and 70/100 or less of the total side length. This is to make the S/V ratio small at BTDC 49°.

As is clear from the above, the volume V1 of the L-side recess 7a is larger than the volume V2 of the T-side recess 7b. A preferable volume ratio V1/V2 is 60/40 or more and 80/20 or less.

<Regarding virtual flame and S/V ratio>
When the L-side spark plug 91 ignites the air-fuel mixture before the top dead center of the compression stroke, the squish flow from the trailing side to the leading side due to the volume change of the working chamber 8 while the flame propagates radially from the ignition point. The center of the flame moves in the direction of rotor rotation. Assuming that there is no interference with the rotor 2 and the rotor housing 3, the shape of the flame generated in that case ideally expands conically from the ignition point in the moving direction, as shown in FIG. The tip surface becomes a hemispherical bulging shape. That is, the shape of the flame is defined by a conical portion 16a having a bottom diameter of 2×r and a height of L, and a hemisphere having a radius of r, where L is the movement distance of the flame center and r is the propagation distance from the flame center. The bulging portion 16b is combined with the bulging portion 16b.

Therefore, a virtual flame 16 generated by the ignition of the air-fuel mixture before the top dead center of the compression stroke by the L-side spark plug 91 is defined. That is, it is a virtual flame 16 in which the height L of the cone 16a is 17.5 mm and the radius r of the hemispherical bulge 16b is 12.5 mm. The volume of the virtual flame 16 is the sum of the volume of the conical portion (1/3×πr ² ×L) and the volume of the hemispherical swelling portion 16b (2/3×πr ³ ). This virtual flame is assumed to be a flame at the time when heat generation is started.

A preferred embodiment of the recess 7 on the outer peripheral surface 2a of the rotor 2 will be described below based on the geometrical interference between the virtual flame 16, the rotor 2 and the rotor housing 3 at the time of BTDC 49° shown in FIG.

The virtual flame 16 geometrically interferes with the rotor 2 and rotor housing 3 at 49° BTDC. The volume of the portion of the virtual flame 16 that does not interfere with the rotor 2 and the rotor housing 3 (the hatched portion in FIG. 9) (hereinafter referred to as “non-interfering volume”) is V (mm ³ ), and the virtual flame 16 S (mm ² ).

The portion of the non-interference volume V of the virtual flame 16 is deprived of heat by the rotor 2 and the rotor housing 3 from the surface in contact with the rotor 2 and the rotor housing 3 (portion of the contact area S). This is cooling loss. In this case, the larger the contact area S compared to the non-interference volume V, the larger the cooling loss.

Therefore, by defining the S/V ratio, which is the ratio of the non-interference volume V to the contact area S, it is possible to estimate the magnitude of the cooling loss in the early stage of combustion of the rotary piston engine based on the virtual flame 16 . A preferred S/V ratio is 0.2037 or less. An S/V ratio of 0.2037 or less means that the cooling loss from the flame at the initial stage of combustion is small.

As shown in FIG. 10 for the rotor 2 at 24° BTDC, the imaginary flame 16 extends forward in the rotor rotation direction through the L-side concave portion 7a. As is clear from the figure, in order to suppress the cooling loss, the above-described deep portion 15 is formed in the front portion of the L-side concave portion 7a so as to reduce the interference between the flame and the rotor 2. It can be seen that the area should be increased.

Here, if the L-side concave portion 7a is enlarged, the virtual flame 16 interferes less with the rotor 2, but the interference with the rotor housing 3 remains unchanged. That is, the imaginary flame 16 interferes with the rotor housing 3 approximately at one half of the longitudinal section passing through the axis of the conical expanded portion. Since the non-interfering volume V of the virtual flame 16 when the L-side concave portion 7a is enlarged and the virtual flame 16 no longer interferes with the rotor 2 is approximately half the total volume of the virtual flame 16, V=1/2 x(1/3 x πr ² x L + 2/3 x πr ³ ). A contact area S between the virtual flame 16 and the rotor housing 3 is S=r×L+(1/2) ^πr2 . Considering this, it can be said that the lower limit of the S/V ratio is preferably about 0.13.

[Example/Comparative example]
Rotors of Examples 1 to 6 and Comparative Examples 1 and 2 having different recess configurations shown in FIGS. 11 and 12 were produced. 11 and 12, the left side diagrams of Examples 1 to 6 and Comparative Examples 1 and 2 show the relationship between the rotor 2 at BTDC 49° and the spark plugs 91 and 92, and the right side diagrams show the relationship between the working chamber 8 and the virtual flame 16. is an enlarged view of the vicinity of the L-side spark plug 91 showing the . In the left figure, white circles and black dots in the recess 7 shown on the right side indicate the positions of the L side spark plug 91 and the T side spark plug 91 . Table 1 shows the recess volume, S/V ratio, etc. of Examples 1 to 7 and Comparative Examples 1 and 2.

Comparative Example 1 is an example in which a rectangular dish-shaped recess 7 having a substantially constant depth is formed on the outer peripheral surface of the rotor 2, and the volume ratio V1/V2 between the L-side recess and the T-side recess is 50/50. In Comparative Example 1, since the tip of the L-side recessed portion is located near the position of the L-side spark plug 91, the interference between the virtual flame 16 and the rotor 2 increases, resulting in an increased S/V ratio.

In Comparative Example 2, compared to Comparative Example 1, the entire recess 7 was shifted forward in the rotor rotation direction, and the tip of the L-side concave portion was slightly bulged forward in the rotor rotation direction, and V1/V2 was 64. /36, and the total recess volume is slightly larger. In Comparative Example 2, the S/V ratio is large, as in Comparative Example 1, because the front end of the L-side concave portion bulges out in a small amount forward in the rotor rotation direction.

In Example 1, compared to Comparative Example 1, the recess 7 is elongated so that the tip of the L-side recess extends forward in the direction of rotation of the rotor, and a deep portion is formed in a portion near the tip of the L-side recess. . As a result, the interference between the virtual flame and the rotor is reduced and the S/V ratio is reduced. V1/V2 is 65/35, and the recess total volume is slightly larger than that of Comparative Example 1.

In Example 2, compared with Comparative Example 1, the recess 7 is elongated, the tip of the L-side recess extends forward in the rotor rotation direction, and the entire recess is deepened. As a result, the interference between the virtual flame and the rotor is reduced and the S/V ratio is reduced. V1/V2 is 64/36, and the recess total volume is slightly larger than that of Comparative Example 1.

In Example 3, compared to Comparative Example 1, the width of the T-side recess is narrowed, the tip of the L-side recess is extended forward in the direction of rotation of the rotor, and a deep portion is formed in the portion near the tip of the L-side recess. is. As a result, the interference between the virtual flame and the rotor is reduced and the S/V ratio is reduced. V1/V2 is 65/35, and the recess total volume is slightly larger than that of Comparative Example 1.

In the fourth embodiment, compared with the first comparative example, the recess 7 is elongated and the tip of the L-side recess extends forward in the rotor rotation direction. As a result, the interference between the virtual flame and the rotor is reduced, and the S/V ratio is reduced. . V1/V2 is 64/36, and the recess total volume is slightly larger than that of Comparative Example 1.

In Example 5, compared to Comparative Example 1, the recess 7 is shifted forward in the rotor rotation direction, and the tip of the L-side concave portion is extended forward in the rotor rotation direction. As a result, the interference between the virtual flame and the rotor is reduced, and the S/V ratio is reduced. . V1/V2 is 63/37, and the recess total volume is slightly larger than that of Comparative Example 1.

In the sixth embodiment, the width of the recess 7 is gradually increased forward in the rotor rotation direction, the tip of the L-side recess is extended forward in the rotor rotation direction, and a deep portion is formed in the portion near the tip of the L-side recess. is. The L-side concave portion is deeper than in Comparative Example 1. As a result, the interference between the virtual flame and the rotor is reduced and the S/V ratio is reduced. Although the total recess volume is the same as in Comparative Example 1, V1/V2 is 79/21, and the compression ratio is higher than in Comparative Example 1.

Embodiment 7 is shown in FIGS. 3 to 7, 9 and 10, in which the L-side concave portion 7a is expanded forward in the direction of rotation of the rotor into a light-bulb shape, and a deep portion is provided in the L-side concave portion. As a result, the interference between the virtual flame and the rotor is reduced, and the S/V ratio is reduced. V1/V2 is 78/22.

In Table 1, total volume Vt is the volume of the working chamber including the rotor recess at 49° BTDC. The V/Vt ratio is the ratio of the non-interfering volume V of the virtual flame 16 to the volume Vt of the working chamber and thus, as it were, represents the flame growth potential. The larger the V/Vt ratio, the easier the flame grows, which is advantageous for shortening the ignition delay period and combustion period. As the non-interference volume V increases, it becomes difficult to ensure a compression ratio of 9.7 or more, so the V/Vt ratio is preferably 0.014 or more and 0.026 or less. FIG. 13 is a graph showing the relationship between the S/V ratio and the V/Vt ratio.

Regarding Comparative Example 1 and Example 6, heat generation characteristics were evaluated at an engine speed of 1500 rpm, a shaft output of 294 kPa, and an EGR rate of 30%. In Example 6 with a small S/V ratio, as shown in FIG. 14, the ignition timing of the L side spark plug 91 was advanced to ATDC -49° The ignition timing is ATDC -40°), the apparent heat generation start point is around ATDC -24°, the combustion period is shortened, the combustion center of gravity advances, and the thermal efficiency is improved. The ignition timing of the T-side spark plug 92 in Comparative Example 1 and Example 6 was ATDC-17°.

Therefore, for Comparative Examples 1 and 2 and Example 6, the fuel consumption was measured at an engine speed of 1500 rpm, a shaft output of 294 kPa, and an EGR rate of 30%. The results are summarized in the relationship between the S/V ratio and V/Vt ratio and the fuel efficiency improvement rate. The fuel efficiency improvement rate was calculated based on Comparative Example 1. FIG. 15 shows the relationship between the S/V ratio and the fuel efficiency improvement rate. FIG. 16 shows the relationship between the V/Vt ratio and the fuel efficiency improvement rate.

According to FIG. 15, it can be seen that the fuel consumption improves as the S/V ratio decreases. It can be seen from FIG. 16 that the fuel efficiency improves as the V/Vt ratio increases.

1 rotary piston engine 2 rotor 2a outer peripheral surface 3 rotor housing 3a trochoid inner peripheral surface 4, 5 side housing 7 recess 7a L side concave portion 7b T side concave portion 8 working chamber 15 deep portion 16 virtual flame 16a conical portion 16b hemispherical swelling portion 31 rotor housing chamber 91 L side spark plug 92 T side spark plug Y long axis Z short axis

Claims (4)

a rotor housing having a substantially elliptical trochoidal inner peripheral surface; side housings arranged on both sides of the rotor housing to form a rotor housing chamber together with the rotor housing; a substantially triangular rotor that partitions the chamber into three working chambers, moves the working chambers in the circumferential direction by rotation, and sequentially performs intake, compression, expansion and exhaust strokes in each working chamber; and a spark plug provided in a rotor housing, wherein recesses are formed in respective outer peripheral surfaces of the rotor defining the working chambers,
A conical portion that spreads conically from the ignition point in the direction of rotation of the rotor and a hemispherical bulge from the tip of the conical portion, which is caused by the ignition of the air-fuel mixture before the top dead center of the compression stroke by the spark plug. When defining a virtual flame consisting of a part, the height L of the cone part is 17.5 mm, and the radius r of the bottom surface of the cone part and the radius r of the hemispherical bulge part are 12.5 mm,
At 49° before top dead center of the compression stroke, the virtual flame geometrically interferes with the rotor and the rotor housing. ³ ), and the S/V ratio is 0.13 or more and 0.2037 or less, where S (mm ² ) is the total area of the surface where the virtual flame contacts the rotor and the rotor housing, A rotary piston engine, wherein a recess is formed in the rotor. In claim 1,
The recess in the outer peripheral surface of the rotor includes a leading side recess extending forward in the rotational direction from the center in the longitudinal direction of the outer peripheral surface, and a trailing side recess continuing from the recess and extending forward in the rotational direction from the center. and
The rotary piston engine, wherein the leading side recess has a larger volume than the trailing side recess. In claim 2,
The leading-side concave portion has a deep portion that is recessed so that the center corresponding to the ignition point of the spark plug is the deepest,
The deep portion is deeper than the trailing recess, is wider than the diameter of the hemispherical bulging portion of the virtual flame, and is formed into a concave curved surface having a radius of curvature larger than the radius of the bulging portion. A rotary piston engine characterized by: In any one of claims 1 to 3,
A rotary piston engine, wherein the geometric compression ratio of the working chamber is 9.7 or more.

Images