rotary engine

Abstract

To improve fuel combustion performance of a rotary engine.SOLUTION: A recess 7 of an outer peripheral surface 2a of a rotor 2 is equipped with a first recessed portion 71 disposed at an outer peripheral surface center C, and a second recessed portion 72 that continues to the first recessed portion 71 and extends to an L side. The first recessed portion has a first bottom surface 71a that includes the outer peripheral surface center C and has a predetermined length L1 from the center toward the L side, and a first inclined surface 71b that inclines and extends from the first bottom surface to a T side recessed end portion 7t. A recess cross section when traversing the recess by a plane orthogonal to a longitudinal direction of a rotor outer peripheral surface and passing through a rotation axis X of the rotor, becomes the largest on the first bottom surface, and a border between the first bottom surface and the first inclined surface is located on a T side as compared with the center.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The technology disclosed herein relates to rotary engines. [Background technology]

[0002] In a rotary engine, a combustion chamber is formed between the rotor and a rotor housing having a trochoidal inner peripheral surface. A recess (depression) that forms the combustion chamber is formed on the outer peripheral surface of the rotor. For example, Patent Document 1 describes such a rotor recess.

[0003] Specifically, Patent Document 1 discloses that the volume of the leading-side recess, which extends from the center of the longitudinal direction of the outer peripheral surface to the front side in the rotor rotation direction, is made larger than the volume of the trailing-side recess, which extends to the front side in the rotor rotation direction. The recess disclosed in Patent Document 1 aims to improve thermal efficiency by advancing the center of gravity of combustion by increasing the volume of the leading-side recess, thereby promoting flame growth and enabling advance ignition and shortening the ignition delay period. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-12410 Summary of the Invention [Problem to be solved by the invention]

[0005] However, promoting flame growth can lead to rapid heat generation due to the accelerated combustion of the air-fuel mixture, which can lead to concerns about combustion noise and gas leakage, and furthermore, the increased cooling loss can be detrimental to improving fuel efficiency.

[0006] The present disclosure has been made in consideration of the above points, and its purpose is to improve the fuel efficiency of rotary engines. [Means for solving the problem]

[0007] A first aspect of the present disclosure relates to a rotary engine comprising: a rotor housing having a substantially elliptical trochoidal inner peripheral surface; side housings arranged on either side of the rotor housing and forming a rotor accommodating chamber together with the rotor housing; a substantially triangular rotor accommodated within the rotor accommodating chamber, dividing the rotor accommodating chamber into three working chambers, and rotating to move each working chamber circumferentially, causing each working chamber to perform intake, compression, expansion, and exhaust strokes in sequence; an ignition plug provided in the rotor housing; and a control unit that controls the operation of the spark plug, wherein recesses are formed in each outer peripheral surface of the rotor that divides the working chambers.

[0008] In the rotary engine, the recess on the outer peripheral surface of the rotor is of Longitudinal direction is the midpoint of the The rotor includes a first recessed portion disposed at a center and extending along a rotation direction of the rotor, and a second recessed portion connected to the first recessed portion and extending toward a front side in the rotation direction, the first recessed portion including the center. a predetermined first depth along a straight line perpendicular to the outer peripheral surface and extending toward the rotation axis of the rotor; A predetermined length from the center toward the front side and, a first bottom surface having a The first bottom surface is continuous with the front end in the rotation direction, As you move towards the front along the above line Depth Above the first depth a first inclined surface that extends from the first bottom surface to the front end of the recess while inclining so as to become shallower; a second inclined surface that is continuous with the front end of the first bottom surface and extends from the first bottom surface to the front end of the second recessed portion while inclining so that the depth along the straight line becomes shallower than the first depth toward the front side; , the second recess includes a second bottom surface that is continuous with the front end of the second inclined surface, has a predetermined second depth that is shallower than the first depth along the straight line, and has a predetermined length from the front end of the second inclined surface toward the front side, and the length from the center to the front end of the recess is between 2 / 10 and 5 / 10 of the length from the center to the front end of the recess.

[0009] According to a first aspect of the present disclosure, when the recess is traversed on a plane perpendicular to the longitudinal direction and passing through the center of rotation of the rotor, the cross-sectional area of ​​the recess is largest at the first bottom surface, and the boundary between the first bottom surface and the first inclined surface is located on the front side in the direction of rotation compared to the center, and the control unit is configured to 2nd bottom and the ignition timing is before the top dead center of the compression stroke. On top Controlling the operation of the spark plug This ignites the air-fuel mixture present between the second bottom surface and the spark plug, generating a flame that sprays out from the spark plug to the front side, and as the rotor rotates, the air-fuel mixture is supplied to the flame sequentially from the first bottom surface and the first inclined surface.

[0010] Hereinafter, the longitudinal center of the outer peripheral surface may be simply referred to as the "center of the outer peripheral surface," the front side in the rotational direction may be referred to as the "L side (Leading side)," the near side in the rotational direction may be referred to as the "T side (Trailing side)," and the top dead center of the compression stroke may be referred to as "TDC."

[0011] According to the first aspect, the spark plug ignites the air-fuel mixture around the second recess at a timing earlier than TDC. The flame generated by this ignition generally blows out from the spark plug toward the L side.

[0012] As the rotor rotates, the air-fuel mixture is supplied to the flame from the first bottom surface of the first recess located on the T side of the second recess, and the flame grows as the mixture is burned. After that, the air-fuel mixture is supplied through the first inclined surface located further on the T side than the first bottom surface, and the mixture is burned up, completing one cycle of combustion in one working chamber.

[0013] Here, the first bottom surface, which has a relatively large cross-sectional area, is not only located on the L side of the first inclined surface, but also extends from the center of the outer circumferential surface toward the L side. Therefore, this first bottom surface can supply the air-fuel mixture to the flame at a timing before TDC, that is, at a timing during the first half of combustion immediately after ignition.

[0014] Generally, the gap between the center of the outer peripheral surface and the rotor housing narrows as the TDC approaches. However, by making the cross-sectional area of ​​the first bottom surface relatively large, a larger amount of the mixture can be supplied to the flame while ensuring the fluidity of the unburned mixture compared to when the cross-sectional area is made small. This allows a larger amount of the mixture to be burned immediately after ignition.

[0015] In addition, by relatively increasing the cross-sectional area of ​​the first bottom surface, the squish flow of the air-fuel mixture can be weakened and its flow rate can be reduced. In other words, it is possible to burn a large amount of air-fuel mixture in the first half of combustion while allowing the combustion to proceed slowly. As a result, it is possible to suppress sudden heat generation and reduce combustion noise, gas leakage, and deterioration of fuel efficiency due to increased cooling loss.

[0016] Furthermore, because the first bottom surface includes the center of the outer circumferential surface, the supply speed of the air-fuel mixture from the T-side to the flame growing on the L-side of the rotor housing's minor axis position around TDC is prevented from increasing, i.e., the flow of the air-fuel mixture from the T-side to the L-side is prevented from becoming strong. This prevents the combustion speed of the main combustion after ignition from increasing, so to speak, and prevents slow combustion and sudden heat generation. This prevents large cooling losses, which is advantageous for improving fuel efficiency, reducing combustion noise, and preventing gas leaks.

[0017] Furthermore, making the cross-sectional area of ​​the first bottom surface the largest is equivalent to making the cross-sectional area of ​​the second recess relatively small. As a result, the air-fuel mixture near the second recess is under higher pressure than the air-fuel mixture near the first recess. This improves ignition of the unburned air-fuel mixture. Furthermore, by making the cross-sectional area of ​​the second recess relatively small in proportion to the increase in the cross-sectional area of ​​the first bottom surface, it is possible to maintain the geometric compression ratio of the engine and ensure thermal efficiency while slowing combustion.

[0018] Furthermore, by providing the first inclined surface on the T side of the center of the outer peripheral surface, the flow of the air-fuel mixture from the T side of the rotor housing's minor axis position to the L side where the flame exists can be smoothly promoted through this first inclined surface during the latter half of combustion after TDC. This suppresses the occurrence or scale of so-called two-stage combustion, which is advantageous for suppressing cooling loss. In this case, the first inclined surface gradually deepens from the T-side end of the recess to the first bottom surface on the L side. By gradually deepening it toward the L side, the flow velocity of the squish flow in the first recess is weakened, which is advantageous for improving fuel efficiency by slowing down combustion.

[0019] According to the first aspect, slow combustion can be achieved in both the first and second half of combustion while supplying a large amount of mixture from the first recess. This reduces combustion noise, gas leakage, and the like, while also reducing cooling loss, thereby improving fuel economy. Furthermore, setting the cross-sectional area of ​​the second recess as described above is even more advantageous in improving fuel economy.

[0020] Furthermore, as in the first aspect, by making the length from the longitudinal center of the outer peripheral surface to the front end of the recess to be between 2 / 10 and 5 / 10 of the length from the longitudinal center of the outer peripheral surface to the front end of the recess, it becomes possible to significantly advance the ignition timing while suppressing two-stage combustion and combustion noise.

[0021] According to the second aspect of the present disclosure, the length of the first bottom surface may be longer than the length of the first inclined surface when viewed along the longitudinal direction.

[0022] According to the second aspect, the proportion of the volume defined by the first bottom surface in the total volume of the first recess can be increased. Because the volume defined by the first bottom surface is larger than the volume defined by the first inclined surface, the total volume of the first recess can be expanded, slowing down combustion and improving fuel economy. Furthermore, since the length of the first inclined surface is relatively short, the first inclined surface becomes steeper and deeper toward the L side. This weakens the flow velocity of the squish flow through the first inclined surface, which is advantageous for improving fuel economy by slowing down combustion.

[0023] Furthermore, according to a third aspect of the present disclosure, Above center The length from the boundary between the first recess and the second recess is Above center The length may be 2 / 10 or more and 4 / 10 or less of the length from the tip to the front end of the outer circumferential surface.

[0024] According to the third aspect, the second recess extends longer on the L side relative to the center of the outer circumferential surface than the first bottom surface of the first recess. This allows the spark plug to face the second recess at the time of ignition, without having to be positioned away from the second recess, even if the ignition timing changes depending on the engine operating conditions, such as the introduction of EGR. This allows the spark plug to be aligned with the second recess at the time of ignition, allowing for changes in ignition timing and ensuring a path for the air-fuel mixture to reach the plug position.

[0025] In addition, the first aspect of the present disclosure 4 According to the embodiment, Above center The length from the front edge of the recess is Above center The distance between the rotor end and the second recess may be greater than or equal to 7 / 10 and less than or equal to 9 / 10 of the length from the first recess to the front end of the outer circumferential surface in the rotational direction. This widens the range of rotor rotation angles at which ignition can be achieved with the spark plug facing the second recess, which is advantageous for advancing the ignition timing.

[0026] In addition, the first aspect of the present disclosure 5 According to this aspect, the spark plug may be arranged at the front position of the rotor housing across the minor axis of the rotor housing, and the control unit may control the operation of the spark plug so that the ignition timing falls within a range of 25° to 55° before top dead center of the compression stroke. [Effects of the Invention]

[0027] As described above, according to the present disclosure, the fuel economy performance of a rotary engine can be improved. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a perspective view showing an overview of a rotary engine according to an embodiment of the present disclosure; [Figure 2] FIG. 2 is a front view showing the rotor and rotor housing of the engine. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] Cross-sectional view showing the size of the gap between the rotor and rotor housing at TDC. [Figure 6] 10 is a graph showing a change in the cross-sectional area of ​​a recess. [Figure 7] FIG. 2 is a cross-sectional view showing the relationship between the rotor and the rotor housing at an ignition timing before TDC. [Figure 8] FIG. 2 is a cross-sectional view showing the relationship between the rotor and the rotor housing in the first half of combustion before TDC. [Figure 9] FIG. 2 is a cross-sectional view showing the relationship between the rotor and the rotor housing in the latter half of combustion after TDC. DETAILED DESCRIPTION OF THE INVENTION

[0029] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following description of preferred embodiments is merely exemplary in nature and is not intended to limit the scope of the present invention, its applications, or uses.

[0030] <Overall structure of the rotary engine> Fig. 1 is a perspective view showing an overview of a rotary engine 1 (hereinafter simply referred to as engine 1) according to an embodiment of the present disclosure, and Fig. 2 is a front view showing a rotor 2 and a rotor housing 3 of the engine 1.

[0031] The engine 1 shown in Fig. 1 is mounted on a vehicle and has one or more rotors 2 (two in the illustrated example). An intermediate housing 4 is provided between two rotor housings 3, each housing housing 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 considered a side housing that forms a rotor accommodating chamber 31 together with the rotor housing 3 and the side housing 5.

[0032] In Figure 1, the front side (right side of Figure 1) of the engine 1 is partially cut away to show the inside of the engine, and the rear side (left side of Figure 1) of the side housing 5 is also shown separated to show the inside of the engine. The symbol X in the figure indicates the rotation axis of the eccentric shaft serving as the output shaft.

[0033] As shown in Fig. 2, the rotor housing 3 has a trochoidal inner peripheral surface 3a that is substantially elliptical (bale-shaped) when viewed from the direction of the rotation axis X, which is described by a parallel trochoid curve. As shown in Fig. 1, the inner peripheral surface of the rotor housing 3, the inner surfaces 4a on both sides of the intermediate housing 4, and the inner surface 5a of the side housing 5 form a rotor accommodating chamber 31, and the rotor 2 is accommodated in this rotor accommodating chamber 31. The rotor accommodating chambers 31 on both sides of the intermediate housing 4 have the same configuration except that the rotation phase of the rotor 2 is different.

[0034] The rotor 2 has a generally triangular shape when viewed from the direction of the rotation axis X, with the center of each side bulging outward, and a recess 7 is formed on the generally rectangular outer peripheral surface 2a between the apexes of the triangle. Apex seals 14 provided at each apex of the triangle of the rotor 2 come into sliding contact with the trochoid inner peripheral surface 3a of the rotor housing 3 as the rotor 2 rotates. The rotor 2 divides the interior of the rotor accommodating chamber 31 into three working chambers 8, as shown in FIG. 2 .

[0035] The rotor 2 is supported by an eccentric ring 6a of the eccentric shaft 6, and while rotating, it revolves around the rotation axis X in the same direction as the rotation (this rotation and revolution are, in a broad sense, simply referred to as the rotation of the rotor 2). During one rotation of the rotor 2, the three working chambers 8 move circumferentially, and each chamber undergoes an intake, compression, expansion (combustion), and exhaust stroke. The rotational force generated by this movement is output from the eccentric shaft 6 via the rotor 2.

[0036] In FIG. 2, the rotor 2 rotates clockwise as indicated by the arrow, and the rotor accommodating chamber 31 is divided by the major axis Y of the rotor accommodating chamber 31, which passes through the rotation axis X. The left side of the rotor accommodating chamber 31 is generally the area for the intake stroke and exhaust stroke, and the right side is generally the area for the compression stroke and expansion stroke.

[0037] 1, intake ports 11-13 and an exhaust port 10 open at locations corresponding to the intake stroke and exhaust stroke regions on the inner surface 4a of the intermediate housing 4 and the inner surface 5a of the side housing 5. Although not shown, a fuel injection valve that injects fuel into the working chamber 8 during the intake stroke or compression stroke is provided at the top of the rotor housing 3.

[0038] 2, the spark plug 9 is attached to the side of the rotor housing 3 at a position on the L side in the direction of rotation of the rotor 2 (hereinafter referred to as the "rotor rotation direction") across the minor axis Z of the rotor accommodating chamber 31 that passes through the rotation axis X, with its electrode exposed toward the rotor accommodating chamber 31. The major axis Y and the minor axis Z are perpendicular to each other.

[0039] Although not shown, the engine 1 is provided with an EGR device that recirculates part of the exhaust gas to the intake passage, and the recirculation of the exhaust gas is performed depending on the operating state of the engine 1.

[0040] The engine 1 also includes a control unit as a control section that controls the operation of the engine 1, including the operation of the intake throttle valve, the fuel injection valve, the spark plug 9, and the EGR device.

[0041] <About the control unit> The control unit is based on a microcomputer and includes a central processing unit (CPU) that executes programs, a memory configured with, for example, RAM or ROM that stores programs and data, and a signal input / output (I / O) bus. Various information signals are input to the control unit from the vehicle's accelerator position sensor, vehicle speed sensor, engine rotation angle sensor, air-fuel ratio sensor, engine water temperature sensor, air flow sensor, etc.

[0042] Based on input signals from various sensors, the control unit determines the operating state of the engine 1. Depending on the determined operating state, the control unit controls the throttle valve opening, the EGR rate by the EGR device, the ignition timing by the spark plug 9 in each working chamber 8, and the fuel injection amount and fuel injection timing by the fuel injection valve.

[0043] The ignition timing of the spark plug 9 is set to 55° or less before top dead center (BTDC) of the compression stroke, preferably within the range of 30° to 50°, and the timing of energization of the ignition coil of the spark plug 9 is controlled based on this setting.

[0044] The ignition timing is controlled according to the EGR rate so that the center of gravity of combustion is located at an appropriate position with high thermal efficiency, between 10° and 30° after top dead center (ATDC) of the compression stroke. As shown by the dotted line in Figure 2, when one of the apexes of the rotor 2 is positioned on the minor axis Z on the opposite side of the spark plug 9, the working chamber 8 located on the opposite side of that apex is at TDC.

[0045] As the EGR rate increases, the ignition delay period becomes longer and the center of combustion gravity is retarded. Therefore, the ignition delay period is set according to the EGR rate, and the target heat generation start timing (target time for the apparent start of heat generation) is also set according to the EGR rate. Then, the ignition timing of the spark plug 9 is set to a time advanced by the ignition delay period from the target heat generation start timing.

[0046] <About the rotor recess> Fig. 3 is a plan view showing the outer peripheral surface 2a of the rotor 2. Fig. 4 is a longitudinal cross-sectional view of the rotor 2, and Fig. 5 is a cross-sectional view showing the size of the gap between the rotor 2 and the rotor housing 3 at TDC. Fig. 6 is a graph showing the change in the cross-sectional area of ​​the recess.

[0047] Here, Fig. 4 corresponds to the IV-IV cross section in Fig. 3. The aa cross section of the second recess 72 in Fig. 4 corresponds to the upper diagram (a) of Fig. 5, the bb cross section of the first bottom surface 71a of the first recess 71 corresponds to the central diagram (b) of Fig. 5, and the cc cross section of the first inclined surface 71b of the first recess 71 corresponds to the lower diagram (c) of Fig. 5.

[0048] FIG. 6 also shows how the recess cross-sectional area changes in the longitudinal direction of the rotor outer peripheral surface 2a. The horizontal axis of FIG. 6 represents position coordinates (unit: mm) with the origin (0) at the center of the longitudinal direction of the rotor outer peripheral surface 2a, with the L side represented as a plus and the T side represented as a minus. More precisely, the length position measured on a straight line connecting the apex seals 14 located at both ends of the rotor outer peripheral surface 2a corresponds to the position coordinates referred to here. In FIG. 6, reference numeral 9a denotes the plug hole of the spark plug 9.

[0049] (Overall structure of the recess) 3, the recess 7 formed in the outer peripheral surface 2a of the rotor 2 (hereinafter referred to as the "rotor outer peripheral surface") extends long in the rotor rotation direction. The center of the recess 7 in the rotor rotation direction is offset toward the L side from the center C in the longitudinal direction of the rotor outer peripheral surface 2a (hereinafter referred to as the "outer peripheral surface center").

[0050] As a result, the length Ll from the outer peripheral surface center C to the L-side end of the recess 7 (hereinafter referred to as the "L-side recess end") 7l is longer than the length Lt from the outer peripheral surface center C to the T-side end of the recess 7 (hereinafter referred to as the "T-side recess end") 7t (Ll > Lt). Note that "length" here refers to the length measured along the rotor outer peripheral surface 2a. Unless otherwise specified, the same applies to various "lengths" that appear below. Furthermore, the "outer peripheral surface center C7" refers to a portion having a central angle of about 4 to 8 degrees of the rotor 2.

[0051] Specifically, it is preferable that the length Lt from the center C of the outer peripheral surface to the T-side recess end 7t is 2 / 10 or more and 5 / 10 or less of the length Ll from the center C of the outer peripheral surface to the L-side recess end 7l (the latter length Ll is 2 times or more and 5 times or less of the former length Lt), and more preferably it is approximately 1 / 4.

[0052] Furthermore, the length Ll from the outer peripheral surface center C to the L-side recess end 7l (the starting position on the L side of the entire recess 7) is preferably in the range of 7 / 10 to 9 / 10, and more preferably 3 / 4, of the length La from the outer peripheral surface center C to the L-side end of the rotor outer peripheral surface 2a. On the other hand, the length Lt from the outer peripheral surface center C to the T-side recess end 7t (the starting position on the T side of the entire recess 7) is preferably in the range of 18 / 100 to 36 / 100, of the length La from the outer peripheral surface center C to the L-side end of the rotor outer peripheral surface 2a.

[0053] The recess 7 according to this embodiment includes a first recess 71 disposed at the center C of the outer circumferential surface and extending along the rotor rotation direction, and a second recess 72 continuous with the first recess 71 and extending toward the L side. The volume of the recess 7 is set so that the geometric compression ratio of the working chamber 8 is 9.7 or more.

[0054] These two recesses 71-72 have bottom surfaces 71a-72a, respectively, having predetermined lengths L1-L2 in the longitudinal direction of the rotor outer peripheral surface 2a. Specifically, the first recess 71 has a first bottom surface 71a having a first length L1 in the longitudinal direction. The second recess 72 has a second bottom surface 72a having a second length in the longitudinal direction.

[0055] 4, the first recess 71 is recessed deeper than the second recess 72. For example, in this embodiment, the depth D1 of the first bottom surface 71a is deeper than the depth D2 of the second bottom surface 72a (see FIG. 5).

[0056] The "depth" here refers to the depth measured along a straight line that is perpendicular to the rotor outer peripheral surface 2a and extends toward the rotation axis X. In particular, in this embodiment, the maximum depth in the rotor width direction among the depths measured along such a straight line is considered to be the "depth."

[0057] Specifically, the depth D2 of the second bottom surface 72a can be set to be not less than 1 / 2 and not more than 3 / 4 of the depth D1 of the first bottom surface 71a, and preferably to be approximately 2 / 3.

[0058] 3, the first recess 71 is slightly wider in the short direction (rotor width direction) of the rotor outer peripheral surface 2a than the second recess 72. That is, in this embodiment, the width W1 of the first bottom surface 71a of the first recess 71 is longer than the width W2 of the second bottom surface 72a of the second recess 72. Note that the "width" here refers to the depth measured along the short direction of the rotor outer peripheral surface 2a.

[0059] (Details of the first recess) More specifically, the first recess 71 according to this embodiment has a first bottom surface 71a including the center C of the outer circumferential surface, a first inclined surface 71b disposed on the T side relative to the center C, and a second inclined surface 71c connecting the first recess 71 to the second recess 72. The first inclined surface 71b, the first bottom surface 71a, and the second inclined surface 71c are continuous in this order from the T side to the L side.

[0060] The first bottom surface 71a extends from the center C of the outer circumferential surface toward the L side and has a predetermined length L1 in the longitudinal direction (hereinafter referred to as the "first length"). The length from the center C of the outer circumferential surface to the T-side end of the first bottom surface 71a (the boundary between the first bottom surface 71a and the first inclined surface 71b) is shorter than the length to the L-side end of the first bottom surface 71a (the boundary between the first bottom surface 71a and the second inclined surface 71c). The first bottom surface 71a extends perpendicular to a straight line that extends from the rotational axis X of the rotor 2 and passes through the center C of the outer circumferential surface.

[0061] The first inclined surface 71b is continuous with the T-side end of the first bottom surface 71a and extends at an angle from the first bottom surface 71a to the T-side recess end 7t so that the depth of the first recess 71 becomes shallower toward the T side. The first inclined surface 71b is configured as an inclined surface that gradually becomes shallower and narrower toward the T side, and extends smoothly until its depth becomes zero. The boundary between the first bottom surface 71a and the first inclined surface 71b is located on the T side relative to the center C of the outer circumferential surface.

[0062] On the other hand, the second inclined surface 71c is continuous with the L-side end of the first bottom surface 71a, and extends at an angle from the first bottom surface 71a to the second recess 72 so that the depth of the first recess 71 becomes shallower toward the L side. The second inclined surface 71c is configured as an inclined surface that gradually becomes shallower and narrower toward the L side, and extends smoothly up to the T-side end of the second bottom surface 72a.

[0063] The first bottom surface 71a is flatter than the first inclined surface 71b and the second inclined surface 71c. This means that the cross-sectional area of ​​the first bottom surface 71a changes more gradually than the cross-sectional areas of the first inclined surface 71b and the second inclined surface 71c.

[0064] For example, as shown in Figure 6, the cross-sectional area of ​​the recess 7 is approximately constant in the first range R1 corresponding to the first bottom surface 71a, and decreases relatively steeply in the ranges corresponding to the first inclined surface 71b and the second inclined surface 71c (ranges adjacent to the first range R1 on the left and right sides of the paper).

[0065] As described above, the first bottom surface 71a extends over a predetermined length range (first length L1) along the longitudinal direction of the rotor outer peripheral surface 2a. When viewed along the longitudinal direction, this first length L1 is approximately the same as the length range (second length L2) of the second bottom surface 72a, as shown in FIG. 3, and is longer than the lengths of the first inclined surface 71b and the second inclined surface 71c.

[0066] Specifically, the first length L1 is preferably 8 / 10 to 12 / 10 of the second length L2, and more preferably approximately 9 / 10. Furthermore, the length from the outer peripheral surface center C to the boundary between the first recess 71 and the second recess 72 (in other words, the length from the outer peripheral surface center C to the second inclined surface 71c) is 2 / 10 to 4 / 10 of the length La from the outer peripheral surface center C to the L-side end of the rotor outer peripheral surface 2a.

[0067] Furthermore, when viewed along the longitudinal direction, the length of the first inclined surface 71b (third length L3) is longer than the length of the second inclined surface 71c. Specifically, the third length L3 is preferably 4 / 10 to 8 / 10 of the first length L1, and more preferably approximately 6 / 10. Furthermore, the length Lc from the outer peripheral surface center C to the boundary between the first bottom surface 71a and the first inclined surface 71b is preferably 1 / 20 to 3 / 20 of the length La from the outer peripheral surface center C to the L-side end of the rotor outer peripheral surface 2a.

[0068] (Details of the second recess) On the other hand, the second recess 72 has, in addition to the second bottom surface 72a, a third inclined surface 72b that connects the second bottom surface 72a to the L-side recess end 71. The second bottom surface 72a and the third inclined surface 72b are continuous in this order from the T side to the L side.

[0069] The third inclined surface 72b is configured as an inclined surface that gradually becomes shallower and narrower from the second bottom surface 72a toward the L-side recess end 7l, smoothly extending to a depth of zero. On the other hand, the second bottom surface 72a forms a flat surface that is flatter than the second bottom surface 72a. This means that the cross-sectional area of ​​the second bottom surface 72a changes more gradually than the cross-sectional area of ​​the third inclined surface 72b.

[0070] For example, as shown in Figure 6, the cross-sectional area of ​​the recess 7 is approximately constant in the second range R2 corresponding to the second bottom surface 72a, and decreases relatively steeply in the range corresponding to the third inclined surface 72b (the range adjacent to the right side of the first range R1 on the paper).

[0071] As described above, the second bottom surface 72a extends over a predetermined length range (second length L2) along the longitudinal direction of the rotor outer peripheral surface 2a. When viewed along the longitudinal direction, the second length L2 is longer than the lengths of the first inclined surface 71b and the second inclined surface 71c, similar to the first length L1, and is also longer than the length of the third inclined surface 72b.

[0072] (more details on cross section) Thus, when comparing the bottom surfaces 71a, 72a of the first recess 71 and the second recess 72, the first bottom surface 71a of the first recess 71 is wider and deeper than the second bottom surface 72a of the second recess 72.

[0073] 5, the first bottom surface 71a and the second bottom surface 72a extend flat in the rotor width direction, with both side portions rising in an arc shape. Therefore, the cross-sectional area of ​​the recess 7 when crossing the recess 7 on a plane perpendicular to the longitudinal direction of the rotor outer peripheral surface 2a and passing through the center of the rotor 2 (hereinafter also referred to as the "recess cross-sectional area") is a size that approximately corresponds to the depth of the recess 7.

[0074] Therefore, in consideration of the relationship between the width and depth described above, the cross-sectional area of ​​the recess according to this embodiment is greatest at the first bottom surface 71a. In other words, considering that the depth D1 of the first bottom surface 71a is substantially constant, the cross-sectional area of ​​the recess is greatest at the center C of the outer circumferential surface.

[0075] Specifically, when the cross-sectional area of ​​the first bottom surface 71a is defined as a first cross-sectional area and the cross-sectional area of ​​the second bottom surface 72a is defined as a second cross-sectional area, the recess cross-sectional area is given by: 1st cross-sectional area > 2nd cross-sectional area…(A) This will satisfy the relationship.

[0076] As described above, the first bottom surface 71a and the second bottom surface 72a according to this embodiment are configured to be flatter than the second inclined surface 71c that connects the bottom surfaces, and therefore each has a relatively constant cross-sectional area.

[0077] Therefore, the above-mentioned relationship (A) is satisfied over substantially the entire area of ​​the first bottom surface 71a and the second bottom surface 72a in the longitudinal direction.

[0078] For example, as shown in FIG. 6 , the second cross-sectional area (see range R2 in FIG. 6 ) can be between ½ and ¾ of the first cross-sectional area (see range R1 in FIG. 6 ). More specifically, the recess cross-sectional area is largest in a first range R1 (a range from the origin 0 extending −10 mm toward the T side and +30 mm toward the L side) corresponding to the first bottom surface 71a. From this range toward the L side, the recess cross-sectional area gradually decreases to between ½ and ¾ of the recess cross-sectional area (first cross-sectional area) in the first range R1 up to a distance of approximately ⅙ of the total length of the first recess 71. From there, the recess cross-sectional area remains substantially constant, between ½ and ¾ of the recess cross-sectional area in the first range R1, until it passes through a second range R2 toward the L side. Thereafter, it reaches the L-side recess end 71 at a distance of approximately ⅙ of the total length of the second range R2, where the recess cross-sectional area becomes zero.

[0079] Furthermore, on the T side, since the first inclined surface 71b is located on the T side of the first bottom surface 71a, the recess cross-sectional area gradually and continuously decreases from the first range R1 to the T-side recess end 7t.

[0080] Furthermore, the boundary between the first bottom surface 71a and the first inclined surface 71b is located on the T side relative to the center C of the outer circumferential surface. In other words, the first bottom surface 71a extends from the T side to the L side so as to pass through the center C of the outer circumferential surface, and has a larger volume than the first inclined surface 71b and the second bottom surface 72a. On the other hand, the first inclined surface 71b has a smaller volume than the first bottom surface 71a and the second bottom surface 72a because its length in the longitudinal direction (third length L3) is relatively short.

[0081] <Action and effect> Fig. 7 is a cross-sectional view showing the relationship between the rotor 2 and the rotor housing 3 at the ignition timing before TDC, Fig. 8 is a cross-sectional view showing the relationship between the rotor 2 and the rotor housing 3 in the first half of combustion before TDC, and Fig. 9 is a cross-sectional view showing the relationship between the rotor 2 and the rotor housing 3 in the second half of combustion after TDC.

[0082] When the engine 1 is operating, the spark plug 9 ignites the air-fuel mixture around the second recess 72 at a timing earlier than TDC (see FIG. 7). The flame generated by this ignition blows out from the spark plug 9 toward the L side.

[0083] Thereafter, as the rotor 2 rotates, the mixture is supplied to the flame from the first recess 71, which is located on the T side of the second recess 72, particularly from its first bottom surface 71a, and the flame grows as the mixture is burned (see Figure 8).

[0084] Thereafter, the air-fuel mixture is supplied through the first inclined surface 71b, which is located further toward the T side than the first bottom surface 71a, and is burned up, thereby completing one cycle of combustion in one working chamber 8 (see FIG. 9).

[0085] 5 and other figures, first bottom surface 71a, which has a relatively large cross-sectional area, is not only located on the L side of first inclined surface 71b, but also extends from the outer circumferential surface center C toward the L side. Therefore, first bottom surface 71a can supply the air-fuel mixture to the flame at a timing before TDC, that is, at a timing during the first half of combustion immediately after ignition.

[0086] 5(a) and 5(b) and 5(b) and 5(c), the gap between the rotor outer peripheral surface 2a and the rotor housing 3 generally narrows as the TDC approaches. However, by forming the cross-sectional area of ​​the first recess 71 relatively large as in the above embodiment, a larger amount of the mixture can be supplied to the flame while ensuring the fluidity of the unburned mixture compared to when the cross-sectional area is formed small. This allows a larger amount of the mixture to be combusted immediately after ignition.

[0087] In addition, by relatively increasing the cross-sectional area of ​​the first bottom surface 71a, the squish flow of the air-fuel mixture can be weakened and its flow rate can be reduced. That is, while a large amount of air-fuel mixture is combusted in the first half of combustion, the combustion can be made to proceed slowly. As a result, sudden heat generation can be suppressed, and combustion noise, gas leakage, and deterioration of fuel economy due to increased cooling loss can be suppressed.

[0088] Furthermore, because the first bottom surface 71a crosses the center C of the outer circumferential surface, the supply speed of the air-fuel mixture from the T-side to the flame growing on the L-side of the minor axis position of the rotor housing 3 around TDC is prevented from increasing, that is, the flow of the air-fuel mixture from the T-side to the L-side is prevented from becoming strong. Therefore, the combustion speed of the main combustion after ignition does not increase, so to speak, slowing down combustion and preventing sudden heat generation. This prevents large cooling losses, which is advantageous for improving fuel efficiency, reducing combustion noise, and preventing gas leakage.

[0089] Furthermore, making the cross-sectional area of ​​the first bottom surface 71a the largest is equivalent to making the cross-sectional area of ​​the second recessed portion 72 relatively small. As a result, the air-fuel mixture near the second recessed portion 72 becomes higher pressure than the air-fuel mixture near the first recessed portion 71. This improves ignition performance when igniting the unburned air-fuel mixture. Furthermore, by making the cross-sectional area of ​​the second recessed portion 72 relatively small in proportion to the increase in the cross-sectional area of ​​the first bottom surface 71a, it is possible to maintain the geometric compression ratio of the engine 1 and ensure thermal efficiency while slowing combustion.

[0090] Furthermore, by providing the first inclined surface 71b on the T side of the outer peripheral surface center C, the flow of the air-fuel mixture from the T side of the minor axis position of the rotor housing 3 to the L side where the flame exists can be smoothly promoted through this first inclined surface 71b during the latter half of combustion after TDC. This suppresses the occurrence or scale of so-called two-stage combustion, which is advantageous for suppressing cooling loss. In this regard, the first inclined surface 71b gradually deepens from the T-side recess end Lt to the first bottom surface 71a on the L side. By gradually deepening the first inclined surface 71b toward the L side, the flow velocity of the squish flow in the first recess 71 is weakened, which is advantageous for improving fuel efficiency by slowing down combustion.

[0091] As described above, according to the embodiment, slow combustion can be achieved in both the first and second half of combustion while supplying a large amount of mixture from the first recess 71. This reduces combustion noise, gas leakage, and the like, while also suppressing cooling loss and improving fuel economy. Furthermore, setting the cross-sectional area of ​​the second recess 72 as described above is even more advantageous in improving fuel economy.

[0092] Furthermore, as shown in FIG. 3 and other figures, by making the length of the first bottom surface 71a (first length L1) longer than the length of the first inclined surface 71b (third length L3), it is possible to increase the proportion of the volume defined by the first bottom surface 71a in the total volume of the first recess 71. Because the volume defined by the first bottom surface 71a is larger than the volume defined by the first inclined surface 71b, the total volume of the first recess 71 can be expanded, which can slow combustion and thereby improve fuel economy. Furthermore, by making the length of the first inclined surface 71b relatively shorter, the first inclined surface 71b becomes steeper and deeper toward the L side. This is advantageous for weakening the flow velocity of the squish flow through the first inclined surface 71b and thereby improving fuel economy by slowing combustion.

[0093] The length from the outer circumferential surface center C to the boundary between the first recess 71 and the second recess 72 is 2 / 10 to 4 / 10 of the length La from the outer circumferential surface center C to the L-side end of the rotor outer circumferential surface 2a.

[0094] 6, on the L side of the outer circumferential surface center C, which corresponds to the origin in the figure, the second recess 72 extends longer than the first bottom surface 71a of the first recess 71. As a result, even if the ignition timing changes depending on the operating state of the engine 1, such as the introduction of EGR, the spark plug 9 can be positioned opposite the second recess 72 at the time of ignition, without facing the second recess 72. This allows for changes in the ignition timing and ensures a path for the air-fuel mixture to reach the plug position.

[0095] 3, the length from the outer circumferential surface center C to the T-side recess end 7t is set to be 2 / 10 or more and 5 / 10 or less of the length from the center C to the L-side recess end 7l, which makes it possible to significantly advance the ignition timing while suppressing two-stage combustion and combustion noise.

[0096] Furthermore, the length Ll from the center C of the outer peripheral surface to the L-side recess end 7l is set to be 7 / 10 or more and 9 / 10 or less of the length La from the center C of the outer peripheral surface to the L-side end of the outer peripheral surface. This widens the range of rotation angles of the rotor 2 at which ignition can be achieved with the spark plug 9 facing the second recess 72, which is advantageous for advancing the ignition timing.

[0097] Other Embodiments In the above embodiment, the first inclined surface 71b and the second inclined surface 71c are each defined as an element of the first recess 71, but this definition is merely for convenience. For example, the second inclined surface 71c may be defined as an element of the second recess 72. The relationship (A) described above holds regardless of such definitions.

[0098] The first bottom surface 71a and the second bottom surface 72a may be inclined or curved along the rotation direction. These bottom surfaces may have a cross-sectional area that changes more gradually than the second inclined surface 71c connecting the bottom surfaces together, or the third inclined surface 72b connecting the bottom surface to the end of the recess 7. [Explanation of symbols]

[0099] 1. Rotary engine 2 rotors 2a Rotor outer surface 3 Rotor housing 3a Trochoid inner surface 4,5 Side housing 7 Recess 71 First recess 71a 1st bottom 71b 1st slope 72 Second recess 72a 2nd bottom 7l L-side recess end (front end of recess) 7t T-side recess end (front end of recess) 8 Working chamber 9 Spark plugs 31 Rotor Containment Room L1 First length (first base length) L2 Second length (length of the bottom of the second recess) L3 Third length (length of first inclined surface) C Center of outer periphery (center of the outer periphery in the longitudinal direction) X Rotation axis Z short axis

Claims

1. a rotor housing having a substantially elliptical trochoidal inner peripheral surface; side housings disposed on either side of the rotor housing and forming a rotor accommodating chamber together with the rotor housing; a substantially triangular rotor accommodated in the rotor accommodating chamber, dividing three working chambers within the rotor accommodating chamber, and rotating to move each working chamber circumferentially, causing each working chamber to perform intake, compression, expansion and exhaust strokes in sequence; an ignition plug provided in the rotor housing; and a control unit for controlling the operation of the ignition plug, wherein recesses are formed in each outer peripheral surface of the rotor which divides the working chambers, the recess in the outer peripheral surface of the rotor includes a first recess disposed at a center that is a midpoint between two equal parts in the longitudinal direction of the outer peripheral surface and extending along a rotational direction of the rotor, and a second recess connected to the first recess and extending toward the front side in the rotational direction; The first recess is a first bottom surface including the center, having a predetermined first depth along a straight line that is perpendicular to the outer circumferential surface and extends toward a rotational axis of the rotor, and having a predetermined length from the center toward the front side; a first inclined surface that is continuous with an end of the first bottom surface on a front side in the rotation direction and that extends from the first bottom surface to the end of the recess on the front side while inclining so that the depth along the straight line becomes shallower than the first depth as it approaches the front side; a second inclined surface that is continuous with the front end of the first bottom surface and extends at an angle from the first bottom surface to the front end of the second recess so that the depth along the straight line becomes shallower than the first depth toward the front side, The second recess is a second bottom surface that is continuous with the front end of the second inclined surface, has a predetermined second depth that is shallower than the first depth along the straight line, and has a predetermined length from the front end of the second inclined surface toward the front side, a length from the center to the front end of the recess is 2 / 10 or more and 5 / 10 or less of a length from the center to the front end of the recess, a cross-sectional area of ​​the recess when crossed on a plane perpendicular to the longitudinal direction and passing through a rotation center of the rotor is largest at the first bottom surface, and a boundary between the first bottom surface and the first inclined surface is located on the near side in the rotation direction relative to the center, The control unit controls the operation of the spark plug so that the spark plug faces the second bottom surface and the ignition timing is a time before top dead center of the compression stroke, thereby igniting the air-fuel mixture present between the second bottom surface and the spark plug to generate a flame that is blown out to the front side from the spark plug, and supplies the air-fuel mixture to the flame from the first bottom surface and the first inclined surface in this order as the rotor rotates. A rotary engine characterized by:

2. 2. The rotary engine according to claim 1, When viewed along the longitudinal direction, the length of the first bottom surface is longer than the length of the first inclined surface. A rotary engine characterized by:

3. 3. The rotary engine according to claim 1, The length from the center to the boundary between the first recess and the second recess is 2 / 10 or more and 4 / 10 or less of the length from the center to the front end of the outer circumferential surface. A rotary engine characterized by:

4. 4. The rotary engine according to claim 1, The length from the center to the front end of the recess is equal to or greater than 7 / 10 and equal to or less than 9 / 10 of the length from the center to the front end of the outer circumferential surface in the rotational direction. A rotary engine characterized by:

5. 5. The rotary engine according to claim 1, the spark plug is disposed in the rotor housing at the front position across the minor axis of the rotor housing, The control unit controls the operation of the spark plug so that the ignition timing falls within a range of 55° or less before top dead center of the compression stroke. A rotary engine characterized by:

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