JP4506815B2 - External combustion engine - Google Patents

Description

  The present invention relates to an external combustion engine.

  In recent years, Stirling engines with excellent theoretical thermal efficiency have attracted attention in order to recover exhaust heat and factory exhaust heat of internal combustion engines mounted on vehicles such as passenger cars, buses, and trucks.

  As a piston device applicable to an external combustion engine including a Stirling engine, a technique disclosed in Japanese Patent Laid-Open No. 2000-46431 (Patent Document 1) is known. The piston of the external combustion engine disclosed in Patent Document 1 is a Stirling engine that uses a displacer that is driven by the action of a working medium that repeatedly compresses and expands in the working space as the piston reciprocates in the cylinder. A pressurizing chamber that is formed inside the piston and temporarily stores the working medium compressed in the working space, and the working medium in the pressurizing chamber is ejected to a clearance portion between the piston and the cylinder. An orifice and a check valve provided at an end of the orifice on the pressurizing chamber side, and the check valve is a working medium in the pressurizing chamber when the working medium pressure in the working space is reduced by the movement of the piston. Is provided to prevent backflow into the working space.

JP 2000-46431 A

  The working medium compressed in the working space of an external combustion engine such as a Stirling engine is introduced into the piston, and the clearance between the piston and the cylinder through a plurality of holes provided in the side periphery (outer periphery) of the piston When a gas bearing is constructed by injecting into a part, a check valve (check valve) that has a mechanically movable part and opens and closes every time the piston moves up and down has been used. It was difficult to secure. The moving part of the check valve does not move stably due to the acceleration caused by the vertical movement of the piston, and the correct position of the check valve may not be obtained. It was a restriction.

  An object of the present invention is to introduce a working medium compressed in a working space of an external combustion engine into a piston and inject it into a clearance portion between the piston and a cylinder from a plurality of holes provided in a side peripheral portion of the piston. Thus, when configuring a gas bearing, it is possible to reliably obtain the function of suppressing the backflow of the working medium inside the piston into the working space, and it is possible to easily ensure the reliability and life. To provide a good external combustion engine.

  An external combustion engine of the present invention is an external combustion engine including a piston device and a cylinder, and the piston device includes a piston main body, a pressure accumulation chamber formed inside the piston main body, and a piston main body. An introduction portion for introducing a working medium compressed in the working space of the external combustion engine into the pressure accumulating chamber; A hole provided in a second portion corresponding to a position below the predetermined height position in the circumferential portion and penetrating from the pressure accumulation chamber to a clearance portion between the piston body and the cylinder; In comparison between when the device is at the top dead center and when the device is at the bottom dead center, the size of the clearance portion between the first portion in the side periphery of the piston body and the cylinder is Device is better when it is in the top dead center, said piston device as compared to when in the bottom dead center, is characterized in that it is configured to be larger.

  In the external combustion engine of the present invention, in comparison between when the piston device is at the top dead center and when the piston device is at the bottom dead center, the second portion in the side periphery of the piston body, and the cylinder When the piston device is at the bottom dead center in the comparison between the first part and the second part in the side peripheral part of the piston body The size of the clearance between the cylinder and the cylinder is substantially the same.

  In the external combustion engine of the present invention, when the piston device is at bottom dead center, the piston device is larger than the diameter of the inner peripheral wall portion of the cylinder facing the first portion in the side peripheral portion of the piston body. It is characterized in that the diameter of the inner peripheral wall portion of the cylinder facing the first portion in the side peripheral portion of the piston main body is larger when at the dead center.

  In the external combustion engine of the present invention, the external combustion engine is an α-type Stirling engine, and the size of the clearance portion between the first portion in the side periphery of the piston body and the cylinder is the piston. The apparatus is characterized in that it is configured to be larger when the device is in a range within 45 ° before and after top dead center than when the piston device is outside the range.

  In the external combustion engine of the present invention, the upper surface of the introduction part is formed in a flat shape so as to have substantially the same height.

  According to the present invention, the working medium compressed in the working space of the external combustion engine is introduced into the piston and injected into the clearance portion between the piston and the cylinder from the plurality of holes provided in the side peripheral portion of the piston. Thus, when a gas bearing is configured, the function of suppressing the backflow of the working medium inside the piston into the working space can be reliably obtained, and the reliability and life can be easily ensured.

  Hereinafter, an embodiment of an exhaust heat recovery apparatus to which a piston device of the present invention is applied will be described in detail with reference to the drawings.

(First embodiment)
The purpose of this embodiment is to introduce a working fluid compressed in the working space of an α-type Stirling engine into the piston, and from a plurality of holes provided in the outer peripheral portion of the piston to a clearance portion between the piston and the cylinder. By injecting, when a gas bearing is configured, the function of suppressing the backflow of the working medium inside the piston into the working space can be reliably obtained, and reliability and life can be easily secured. An exhaust heat recovery device comprising a Stirling engine to which a possible piston device is applied is provided.

  In the present embodiment, in particular, when the Stirling engine operates using, for example, exhaust heat such as exhaust gas of an internal combustion engine of a vehicle as a heat source, the amount of heat obtained is limited, and the Stirling engine is limited within the range of the obtained heat amount. Since it is necessary to operate effectively, the weight reduction of a piston is calculated | required. In the present embodiment, the Stirling engine is required to be reduced in size (overall configuration). In particular, when the Stirling engine operates using exhaust heat such as exhaust gas of an internal combustion engine of a vehicle as a heat source, the space adjacent to the exhaust pipe of the internal combustion engine disposed under the floor of the vehicle is limited. This is because it may be necessary to install a Stirling engine in the space. In the Stirling engine described below, the weight of the piston is reduced and the size of the apparatus is reduced.

  FIG. 3 is a front view showing the Stirling engine of the present embodiment. As shown in FIG. 3, the Stirling engine 10 of this embodiment is an α-type (two-piston type) Stirling engine, and includes two power pistons 20 and 30. The two power pistons 20 and 30 are arranged in parallel in series. As shown in FIG. 4, the piston 31 of the low temperature side power piston 30 has a phase difference so as to move with a delay of about 90 ° in crank angle with respect to the piston 21 of the high temperature side power piston 20.

  The working fluid heated by the heater 47 flows into the space (expansion space) above the cylinder (hereinafter referred to as the high temperature side cylinder) 22 of the high temperature side power piston 20. The working fluid cooled by the cooler 45 flows into the space (compression space) above the cylinder (hereinafter referred to as the low temperature side cylinder) 32 of the low temperature side power piston 30.

  The regenerator (regenerative heat exchanger) 46 stores heat when the working fluid reciprocates between the expansion space and the compression space. That is, when the working fluid flows from the expansion space to the compression space, the regenerator 46 receives heat from the working fluid, and when the working fluid flows from the compression space to the expansion space, passes the stored heat to the working fluid.

  As the two pistons 21 and 31 reciprocate, the reciprocating flow of the working gas occurs, and the ratio of the working fluid in the expansion space of the high temperature side cylinder 22 and the compression space of the low temperature side cylinder 32 changes. As it changes, pressure fluctuations occur. Comparing the pressures when the two pistons 21 and 31 are in the same position, the expansion piston 21 is considerably higher when it is lowered than when it is raised, and the compression piston 31 is lower. For this reason, the expansion piston 21 needs to perform a large positive work (expansion work) with respect to the outside, and the compression piston 31 needs to receive work (compression work) from the outside. Part of the expansion work is used for compression work, and the rest is taken out as an output via the drive shaft 40.

  The Stirling engine 10 of this embodiment is used with a gasoline engine (internal combustion engine) in a vehicle to constitute a hybrid system. That is, the Stirling engine 10 uses the exhaust gas of the gasoline engine as a heat source. The heater 47 of the Stirling engine 10 is disposed inside the exhaust pipe 100 of the gasoline engine of the vehicle, and the working fluid is heated by the thermal energy recovered from the exhaust gas, so that the Stirling engine 10 is operated.

  The Stirling engine 10 of the present embodiment is installed in a limited space in the vehicle such that the heater 47 is accommodated in the exhaust pipe 100, so that the installation of the Stirling engine 10 is more compact if the entire device is compact. The degree increases. For this purpose, the Stirling engine 10 employs a configuration in which the two cylinders 22 and 32 are arranged in series and not in a V shape.

  When the heater 47 is disposed inside the exhaust pipe 100, the heater 47 is connected to the upstream side (the side close to the gasoline engine) 100a of the exhaust gas through which a relatively high-temperature exhaust gas flows. The high temperature side cylinder 22 side is located, and the low temperature side cylinder 32 side of the heater 47 is located on the downstream side (the side far from the gasoline engine) 100b through which relatively low temperature exhaust gas flows. This is because the high temperature side cylinder 22 side of the heater 47 is heated more.

  Each of the high temperature side cylinder 22 and the low temperature side cylinder 32 is formed in a cylindrical shape and supported by a substrate 42 which is a reference body. In the present embodiment, the substrate 42 serves as a position reference for each component of the Stirling engine 10. With this configuration, the relative positional accuracy of each component of the Stirling engine 10 is ensured. In addition, the substrate 42 can be used as a reference when the Stirling engine 10 is attached to the exhaust pipe (exhaust passage) 100 or the like that is the target of heat recovery.

  A substrate 42 is fixed to the flange 100f of the exhaust pipe 100 via a heat insulating material (spacer, not shown). Since the exhaust pipe 100 and the substrate 42 are fixed in a state where relative positional accuracy is ensured, the substrate 42 can be regarded as a device mounting surface provided in the exhaust pipe 100 as a fixed structure. A flange 22 f provided on the side surface (outer peripheral surface) of the high temperature side cylinder 22 is fixed to the substrate 42. Further, a flange 46f provided on a side surface (outer peripheral surface) 46c of the regenerator 46 is fixed to the substrate 42 via a heat insulating material (spacer, not shown). A partition wall 70 to be described later is fixed to the substrate 42.

  All structural members of the Stirling engine 10 are supported on the substrate 42. From this, when the substrate 42 is deformed by the heat of the exhaust gas in the exhaust pipe 100, the deformation affects all the structural members of the Stirling engine 10. Therefore, the heat insulating material is provided between the flange 100f of the exhaust pipe 100 and the heat of the exhaust gas in the exhaust pipe 100 is suppressed to the substrate 42 by the shroud 90 to the minimum.

  The exhaust pipe 100 and the Stirling engine 10 are attached via a substrate 42. At this time, the substrate 42 and the end surface on the side where the heater 47 is connected in the high temperature side cylinder 22 (upper surface of the top portion 22b), and the end surface on the side where the cooler 45 is connected in the low temperature side cylinder 32 (top surface 32a). And the Stirling engine 10 are attached to the substrate 42 so that they are substantially parallel to each other. Alternatively, the Stirling engine 10 is configured such that the substrate 42 and the rotation axis of the crankshaft 43 (or the drive shaft 40) are parallel, or the central axis of the exhaust pipe 100 and the rotation axis of the crankshaft 43 are parallel. Is attached to the substrate 42. Thereby, the Stirling engine 10 can be easily attached to the exhaust pipe 100 without making a significant design change to the existing exhaust pipe 100. As a result, the Stirling engine 10 can be mounted on the exhaust pipe 100 without impairing the performance, mountability, noise, and other functions of the internal combustion engine body of the vehicle that is the subject of exhaust heat recovery. Further, even when the Stirling engine 10 having the same specification is attached to different exhaust pipes, it can be dealt with only by changing the specification of the heater 47, so that versatility can be improved.

  The Stirling engine 10 is placed horizontally in a space adjacent to the exhaust pipe 100 arranged under the floor of the vehicle, that is, each of the high temperature side cylinder 22 and the low temperature side cylinder 32 with respect to the vehicle floor (not shown). The two pistons 21 and 31 are reciprocated in the horizontal direction. In the present embodiment, for convenience of explanation, it is assumed that the top dead center side of the two pistons 21 and 31 is upward and the bottom dead center side is downward.

  The higher the average pressure of the working fluid, the higher the pressure difference with respect to the same temperature difference caused by the cooler 45 and the heater 47, so that a higher output can be obtained. Therefore, as described above, the working fluid in the high temperature side cylinder 22 and the low temperature side cylinder 32 is maintained at a high pressure.

  The pistons (piston devices) 21 and 31 are formed in a columnar shape. A small clearance of several tens of μm is provided between the outer peripheral surfaces of the pistons 21 and 31 and the inner peripheral surfaces of the cylinders 22 and 32. The working fluid (air) of the Stirling engine 10 is included in the clearances. Intervene. The pistons 21 and 31 are supported in a non-contact state by air bearings 48 with respect to the cylinders 22 and 32, respectively. Therefore, the piston ring is not provided around the pistons 21 and 31, and the lubricating oil generally used with the piston ring is not used. As described above, the air bearing 48 keeps the airtightness of the expansion space and the compression space with the working fluid (gas), and performs clearance sealing without ring and without oil.

  As will be described later with reference to FIG. 1, the air bearing 48 introduces working fluid compressed in the working space of the Stirling engine 10 into the pistons 21 and 31, and is provided on the outer periphery of the pistons 21 and 31. It is a static pressure gas bearing constituted by injecting into a clearance part between pistons 21 and 31 and cylinders 22 and 32 from a plurality of holes.

  In this embodiment, since the heat source of the Stirling engine 10 is the exhaust gas of the internal combustion engine of the vehicle, the amount of heat obtained is limited, and it is necessary to operate the Stirling engine 10 effectively within the range of the obtained heat amount. . Therefore, the top (upper part) 22b of the high temperature side cylinder 22 and the upper part of the side surface 22c of the high temperature side cylinder 22 are arranged inside the exhaust pipe 100 so that the working fluid as hot as possible flows in the expansion space. Thereby, the upper part of the expansion piston 21 in the vicinity of the top dead center is located inside the exhaust pipe 100, and the upper part of the expansion piston 21 is effectively heated.

  Next, with reference to FIG.1 and FIG.2, the structure of piston 21 and 31 is demonstrated in detail.

  FIG. 1 is a front view showing the configuration of the piston 21. FIG. 2 is a front sectional view of a main part of the piston 21. As shown in FIG. 3, the sizes of the pistons 21 and 31 are different, but the structure is common. In FIGS. 1 and 2, a structure common to the pistons 21 and 31 is shown. Below, FIG.1 and FIG.2 is demonstrated as a structure of the piston 21 (The description about the piston 31 of the same structure is abbreviate | omitted).

  As shown in FIG. 1, the piston 21 includes a piston main body 211 and a hollow portion (pressure accumulation chamber) 212 formed inside the piston main body 211. The piston body 211 is formed in a cylindrical shape whose upper and lower portions are closed.

  The piston main body 211 includes a side peripheral portion (sliding portion) 211a that slides with the high temperature side cylinder 22 (FIG. 3), and a top surface portion 211b that is provided integrally with the side peripheral portion 211a (continuously) in a lid shape. have. A communication channel 214 that communicates the working space in the high temperature side cylinder 22 and the hollow portion 212 is formed in the top surface portion 211b.

  The communication flow path 214 has a remarkably large flow path resistance at the time of reverse flow compared to that at the time of forward flow, and is constituted by a fluid element 215 having no movable part such as a valve body. That is, the fluid element 215 has a flow path resistance when the direction of the flow of the working fluid passing through the communication flow path 214 is a downward direction (a direction from the working space side to the hollow portion 212) (forward flow). Constructed in a shape that is relatively small and, on the contrary, in the upward direction (the direction toward the working space from the hollow portion 212) (during reverse flow), the flow resistance is significantly greater than in forward flow. Has been.

  The fluid element 215 causes the working fluid in the hollow portion 212 to flow back into the working space in the high temperature side cylinder 22 when the pressure of the working fluid in the working space in the high temperature side cylinder 22 decreases due to the movement of the piston 21. Is suppressed. Since the fluid element 215 does not have a movable part like the valve body of the check valve (check valve), it is easy to ensure reliability and life, and it becomes a structural limitation in design. Is suppressed.

  FIG. 2 is an enlarged view showing the fluid element 215. In the fluid element 215, the curvature R1 of the forward flow side inlet portion 215a is formed relatively large, and the curvature R2 of the reverse flow side inlet portion 215b is not formed (zero) or extremely small. The forward flow side inlet 215 a is formed so that the diameter of the opening gradually decreases, and the flow line when drawing the working fluid into the communication channel 214 becomes smooth. The counterflow side inlet portion 215b has an edge, and the working fluid in the hollow portion 212 causes separation of the fluid that tries to flow back into the working space, and the flow rate flows back from the hollow portion 212 to the working space due to a contraction effect or the like. Is suppressed.

  In the fluid element 215, no protrusion protruding from the top surface portion 211b to the working space side is formed on the forward flow side inlet portion 215a side (reference numeral D1), whereas the hollow portion 212 is formed on the reverse flow side inlet portion 215b side. A protrusion D2 protruding toward the end is provided, and a backflow side inlet 215b is provided at the tip of the protrusion D2.

  In the fluid element 215, the angle θ formed by the end surface S on the backflow side inlet 215b side and the flow path of the communication flow path 214 is an acute angle (smaller than 90 °). However, it is not necessary to define this angle when the protrusion D2 of the backflow side inlet 215b is thin and the end surface itself is extremely small (see FIG. 6 described later). The fluid element 215 constituting the communication channel 214 shown in FIGS. 1 and 2 may be formed integrally (continuously) with the piston 21 (integral structure) as shown in FIG. However, as shown in FIGS. 6 and 7, the piston 21 may be configured separately.

  In the case of the integral structure shown in FIG. 8, for example, a portion corresponding to the top surface portion 211 b of the piston 21 can be formed by punching with a press and plastically deforming. When configured as a separate body, as shown in FIG. 6, the forward flow side inlet portion 215 a is formed integrally with the piston 21, and the protruding portion (reverse flow side inlet portion 215 b) is a tube 218 separate from the piston 21. Can be configured. Further, as shown in FIG. 7, the entire portion corresponding to the fluid element 215 can be constituted by a chip 219.

  As shown in FIG. 1, the side peripheral portion 211 a is provided with a plurality of air supply holes 216 at equal intervals in the circumferential direction. When the working fluid in the working space of the high temperature side cylinder 22 is compressed as the piston 21 rises and the pressure of the working fluid becomes higher than the pressure of the hollow portion 212, the forward flow side inlet portion 215 a passes through the communication flow path 214. A part of the working fluid in the working space is introduced into the hollow portion 212. When the working fluid is introduced into the hollow portion 212 via the communication channel 214, a part of the working fluid in the hollow portion 212 is ejected to the clearance between the piston 21 and the cylinder 22 via the air supply hole 216. .

  The communication channel 214 is formed at the center on the surface of the top surface portion 211b. Thereby, the distance between the communication channel 214 and the plurality of air supply holes 216 becomes equal. When the working fluid in the working space is introduced into the hollow portion 212 via the communication channel 214, the ejection states (injection amount / injection pressure) of the working fluid ejected from the plurality of air supply holes 216 are easily equalized, When the working fluid is injected into the clearance, there is little possibility of causing a bias in the circumferential direction with respect to the injection. Thereby, the air bearing 48 functions more stably.

  It is desirable that the pressure of the working fluid enclosed in the hollow portion 212 is slightly lower than the maximum compression pressure of the working fluid. FIG. 4 shows changes in the top surface position of the high temperature side piston 21 and the top surface position of the low temperature side piston 31. As described above, the low temperature side piston 31 has a phase difference so as to move 90 ° behind the high temperature side piston 21 with a crank angle.

  In FIG. 4, a combined wave W of the waveform of the high temperature side piston 21 and the waveform of the low temperature side piston 31 indicates the in-cylinder pressure. In FIG. 4, the symbol Pmax indicates the maximum value (maximum compression pressure) of the in-cylinder pressure during the compression process. When the piston 21 is operated, the maximum compression pressure Pmax acts on the piston body 211 at the maximum. Therefore, by filling the hollow portion 212 with a working fluid having a pressure slightly lower than the maximum compression pressure Pmax of the working fluid, an in-cylinder pressure (hollow) that is lower than the maximum compression pressure Pmax by a predetermined value or more in the piston body 211. When the pressure lower than the pressure of the portion 212 is acting (except when the piston 21 is near the top dead center during the compression process), the piston main body 211 has a sufficient pressure resistance performance against the in-cylinder pressure ( Rigidity). Thereby, the thickness of the piston main body 211 (particularly, the portion other than the portion where the air supply hole 216 is formed in the side peripheral portion 211a) can be formed thin without considering the pressure resistance performance against the in-cylinder pressure, Weight reduction is realized.

  The operation when the working fluid having a pressure slightly lower than the maximum compression pressure Pmax of the working fluid is sealed in the hollow portion 212 is as follows. That is, during the compression process, when the piston 21 is in a position near the top dead center, the pressure in the working space of the high temperature side cylinder 22 exceeds the pressure in the hollow portion 212, and the working space is operated from the communication channel 214. While a part of the fluid is introduced, a part of the working fluid in the hollow portion 212 is ejected from the air supply hole 216 to the outside of the piston 21. The pressure of the hollow portion 212 is higher than the pressure of the working space of the high temperature side cylinder 22 except when the piston 21 is in the above position. However, as described above, the fluid element 215 is in the reverse flow, the forward flow, and the like. Since the flow path resistance is remarkably increased as compared with the above, the working fluid in the hollow portion 212 flows backward from the backflow side inlet portion 215b to the working space in the high temperature side cylinder 22 through the communication flow path 214. It is suppressed.

  At least one air supply hole 216 is provided above and below the intermediate position of the length of the piston 21 in the vertical direction (two in each case, four in total are shown in FIG. 1). This is effective for balancing the position of the piston 21 in the high temperature side cylinder 22.

  The heater 47 has a plurality of heat transfer tubes (tube groups) 47t, and the plurality of heat transfer tubes 47t are formed in a substantially U-shape. A first end portion 47a of each heat transfer tube 47t is connected to an upper portion (end surface on the top surface 22a side) 22b of the high temperature side cylinder 22. The first end portions 47a of the plurality of heat transfer tubes 47t are provided so as to be disposed substantially on the same surface (flat surface). The first ends 47a of the plurality of heat transfer tubes 47t arranged on the substantially flat surface are respectively connected to the upper portion 22b of the high temperature side cylinder 22 formed on the substantially flat surface. From these things, the process and connection operation | work by the side of the 1st end part 47a of the some heat exchanger tube 47t become easy. On the other hand, the second end 47b of each heat transfer tube 47t is connected to the upper part (end surface on the heater 47 side) 46a of the regenerator 46.

  The regenerator 46 includes a heat storage material (matrix, not shown) and a regenerator housing 46h in which the heat storage material is accommodated. The regenerator housing 46 h accommodates a substantially cylindrical heat storage material having substantially the same cross-sectional shape as the upper part of the low temperature side cylinder 32. Therefore, the regenerator housing 46h is formed in a cylindrical shape (hollow column shape) having a bottom surface and an upper surface that are substantially the same as the cross-sectional shape of the upper portion of the low temperature side cylinder 32.

  A flange 46f is provided on a side surface (outer peripheral surface) 46c of the regenerator 46, and the flange 46f is fixed to the substrate 42 via a heat insulating material. In the regenerator 46, a laminated wire mesh (laminated material) is used as a heat storage material. The metal mesh is laminated along the direction in which the working fluid flows, and the plurality of metal meshes are provided in a state in which heat transfer is unlikely to occur.

  When the heat storage material receives heat from the working fluid when the working fluid flows from the expansion space to the compression space, first, the uppermost wire mesh closest to the heater 47 among the plurality of stacked wire meshes receives heat. The temperature of the fluid is lowered, and then the temperature of the working fluid is further lowered by receiving the heat of the wire mesh near the heater 47, and the temperature of the working fluid is further lowered by receiving the heat of the wire mesh near the heater 47 next. Thus, each time the regenerator 46 passes through the wire mesh layer from the top to the bottom, the temperature of the working fluid decreases.

  The following conditions are required for the regenerator 46 from the above-described functions. That is, the heat transfer performance and the heat storage capacity are high, the flow resistance (flow loss, pressure loss) is small, the thermal conductivity in the flow direction of the working fluid is small, and a large temperature gradient is required. For this reason, the heat conduction between the plurality of wire meshes is required to be as small as possible. The wire mesh material can be stainless steel.

  In the regenerator 46 disposed inside the exhaust pipe 100, there is a very high need to suppress the adverse effect of heat conduction in the flow direction of the working fluid in the regenerator housing 46h. Therefore, in this embodiment, the shroud 90 is provided in the regenerator housing 46h. The shroud 90 is intended to prevent heat (for example, about 600 to 800 ° C.) inside the exhaust pipe 100 from being transferred to the regenerator housing 46h. In this case, the shroud 90 is particularly intended to prevent transmission to the surfaces (side surface 46c and flange 46f) except the upper surface 46a of the regenerator housing 46h.

  In the above, the vertical length of the expansion piston 21 is formed larger than that of the compression piston 31, and the vertical length of the high temperature side cylinder 22 is formed larger than that of the low temperature side cylinder 32. The reason is as follows.

  In order to suppress a decrease in the efficiency of the Stirling engine 10, a space other than the expansion space in the high temperature side power piston 20 and a space other than the compression space in the low temperature side power piston 30, that is, the high temperature side power piston 20 and the low temperature side power piston. The space around the crankshaft 43 in each of the 30 needs to be kept at room temperature. Therefore, the high temperature working fluid in the expansion space flows into the space around the high temperature side power piston 20 of the crankshaft 43, or the low temperature working fluid in the compression space is around the low temperature side power piston 30 side of the crankshaft 43. It is necessary to securely seal the high temperature side cylinder 22 and the expansion piston 21 and the low temperature side cylinder 32 and the compression piston 31 so as not to flow into the space. Air bearing 48 is used).

  On the other hand, as described above, since the top portion 22b and the upper portion of the side surface 22c of the high temperature side cylinder 22 are accommodated inside the exhaust pipe 100 in order to increase the temperature of the expansion space, the upper portion of the high temperature side cylinder 22 and the expansion piston. The upper part of 21 expands thermally. There is a possibility that sealing cannot be reliably performed in the portions of the high temperature side cylinder 22 and the expansion piston 21 which are thermally expanded. Therefore, in the present embodiment, the lengths of the expansion piston 21 and the high temperature side cylinder 22 in the vertical direction are set long, thereby providing a temperature gradient in the vertical direction of the expansion piston 21 to influence the influence of thermal expansion. Sealing can be surely performed at a portion not received (lower portion of the expansion piston 21). In addition, since the space between the high temperature side cylinder 22 and the expansion piston 21 is sealed at the lower portion of the expansion piston 21 (the portion that is not affected by thermal expansion), the movement distance of the seal portion is sufficiently secured for expansion. In order to sufficiently compress the space, the length in the vertical direction of the high temperature side cylinder 22 is set long.

  Next, the configuration of the cooler 45 will be described.

  In FIG. 3, only a part of the heat transfer tubes 45t of the plurality of heat transfer tubes 45t of the cooler 45 are illustrated, and the other heat transfer tubes 45t are not illustrated.

  The partition (member) 70 is provided between the regenerator 46 and the low temperature side cylinder 32. The partition wall 70 is made of a material having low thermal conductivity. In the partition wall 70, the length dimension in the axial direction (vertical direction) of the low temperature side cylinder 32 is designed to be as small as possible while ensuring a sufficient size to fulfill the function of routing the heat transfer tube 45t described later. This is to contribute to downsizing of the Stirling engine 10.

  As described above, the partition wall 70 is fixed to the substrate 42. The upper surface 70a of the partition wall 70 is provided so as to be in direct contact with the lower surface of the regenerator 46 (the end surface on the heater 47 side opposite to the end surface 46a) 46b. The lower surface 70 b of the partition wall 70 also serves as the top surface 32 a of the low temperature side cylinder 32. A cooler container 45 c of the cooler 45 is fixed to a side surface (outer peripheral surface) 70 c of the partition wall 70.

  The cooler 45 is constituted by a water-cooled multi-tube heat exchanger (shell-and-tube exchanger, tubular exchanger). The cooler 45 includes a plurality of heat transfer tubes (tube groups) 45t and a cooler container 45c. Most of the plurality of heat transfer tubes 45t of the cooler 45 are accommodated in a cooler container 45c. The portion of the heat transfer tube 45t accommodated in the cooler container 45c comes into contact with the cooling water (refrigerant) Wt supplied to the cooler container 45c, whereby the working fluid flowing through the heat transfer tube 45t is cooled.

  As described above, the cooler container 45 c is fixed to the outer peripheral surface 70 c of the partition wall 70. The cooler container 45c is provided in a ring shape over the circumferential direction of the outer peripheral surface 70c. The cooler container 45c is formed in a ring shape that surrounds an upper portion (a portion corresponding to the compression space) of the outer peripheral portion 32k of the low temperature side cylinder 32 in the circumferential direction. The cooler container 45 c is provided over the entire circumference of the outer peripheral portion 32 k of the low temperature side cylinder 32. Alternatively, the cooler container 45c can be provided so as to surround a part of the outer peripheral portion 32k of the low temperature side cylinder 32 in the circumferential direction.

  Next, the piston / cylinder seal structure and the piston / crank mechanism will be described.

  As described above, since the heat source of the Stirling engine 10 is the exhaust gas of the internal combustion engine of the vehicle, the amount of heat obtained is limited, and it is necessary to operate the Stirling engine 10 within the range of the obtained heat amount. Therefore, in this embodiment, the internal friction of the Stirling engine 10 is reduced as much as possible. In this embodiment, in order to eliminate the friction loss due to the piston ring having the largest friction loss among the internal friction of the Stirling engine, the piston ring is not used, and instead, between the cylinders 22 and 32 and the pistons 21 and 31. Each is provided with an air bearing 48.

  Since the air bearing 48 has extremely small sliding resistance, the internal friction of the Stirling engine 10 can be greatly reduced. Even if the air bearing 48 is used, since the airtightness between the cylinders 22 and 32 and the pistons 21 and 31 is ensured, there is no problem that a high-pressure working fluid leaks during expansion and contraction.

  The air bearing 48 is a bearing in which the pistons 21 and 31 are floated in the air using the pressure (distribution) of air generated by a minute clearance between the cylinders 22 and 32 and the pistons 21 and 31. In the air bearing 48 of the present embodiment, the diameter clearance between the cylinders 22 and 32 and the pistons 21 and 31 is several tens of μm. In realizing an air bearing that floats an object in the air, the static pressure gas bearing is applied. The static pressure gas bearing jets pressurized fluid and floats an object (the pistons 21 and 31 in this embodiment) by the generated static pressure.

  Further, since the use of the air bearing 48 eliminates the need for the lubricating oil used in the piston ring, there is no problem that the heat exchanger (the regenerator 46 and the heater 47) of the Stirling engine 10 deteriorates due to the lubricating oil. .

  When the pistons 21 and 31 are reciprocated in the cylinders 22 and 32 using the air bearing 48, the linear motion accuracy must be less than the diameter clearance of the air bearing 48. Further, since the load capacity of the air bearing 48 is small, the side forces of the pistons 21 and 31 must be substantially zero. That is, since the air bearing 48 has a low ability (pressure resistance ability) to withstand the force in the diameter direction (lateral direction, thrust direction) of the cylinders 22 and 32, the linear motion accuracy of the pistons 21 and 31 with respect to the axes of the cylinders 22 and 32 is low. Need to be expensive. In particular, the air bearing 48 of the type that is used in the present embodiment and is supported by levitating using a fine clearance air pressure has a low pressure resistance against the force in the thrust direction compared to the type that blows high-pressure air. Higher linear motion accuracy of the piston is required.

  For this reason, in this embodiment, the grasshopper mechanism (approximate linear link) 50 is employed in the piston / crank portion. The glass hopper mechanism 50 is smaller in size than the other linear approximation mechanism (for example, a watt mechanism), so that the size of the mechanism necessary for obtaining the same linear motion accuracy is small. It is done. In particular, the Stirling engine 10 according to the present embodiment is installed in a limited space such that the heater 47 is accommodated in the exhaust pipe of an automobile. The degree increases. Further, the grasshopper mechanism 50 is advantageous in terms of fuel consumption because the weight of the mechanism necessary for obtaining the same linear motion accuracy is lighter than other mechanisms. Further, the grasshopper mechanism 50 is easy to configure (manufacture / assemble) because the structure of the mechanism is relatively simple.

  FIG. 5 shows a schematic configuration of the piston / crank mechanism of the Stirling engine 10. In the present embodiment, since the piston / crank mechanism adopts a common configuration for the high temperature side power piston 20 side and the low temperature side power piston 30 side, only the low temperature side power piston 30 side will be described below. Description of the high temperature side power piston 20 side is omitted.

  As shown in FIGS. 5 and 3, the reciprocating motion of the compression piston 31 is transmitted to the drive shaft 40 by the connecting rod 109, where it is converted into rotational motion. The connecting rod 109 is supported by the approximate linear mechanism 50 shown in FIG. 5, and reciprocates the low temperature side cylinder 32 linearly. Thus, by supporting the connecting rod 109 by the approximate linear mechanism 50, the side force F of the compression piston 31 becomes almost zero, so that the compression piston 31 can be sufficiently supported by the air bearing 48 having a small load capacity. it can.

  In the above-described embodiment, the configuration in which the Stirling engine 10 is attached to the exhaust pipe 100 so as to use the exhaust gas of the internal combustion engine of the vehicle as a heat source has been described. However, the Stirling engine of the present invention is not limited to a type attached to the exhaust pipe of an internal combustion engine of a vehicle.

  In the above description, the configuration, operation, and effect of the piston device are described using an example in which the piston device is applied to a piston of a Stirling engine. However, the piston device is used for an external combustion engine other than the piston of the Stirling engine. Can be easily applied, and when applied, has the same utility as described above.

(First modification of the first embodiment)
Next, a first modification of the first embodiment will be described with reference to FIGS. 9 to 11.

  As shown in FIG. 9, the fluid element 215 may have a two-stage (multi-stage) configuration via a small chamber (buffer) 220. When the fluid element 215 has a two-stage configuration, a higher pressure than the one-stage configuration of the first embodiment can be taken into the hollow portion 212. In the case of a multi-stage configuration, the flow resistance at the time of backflow is further reduced compared to that at the time of forward flow, so that the working fluid in the hollow portion 212 flows from the backflow side inlet 215b through the communication flow path 214 to the high temperature side cylinder 22. This is because the backflow into the working space is further suppressed.

  As shown in FIG. 10, when the fluid element 215 has a two-stage configuration via the small chamber 220, the communication channel 214-1 of the fluid element 215-1 on the hollow portion 212 side is relatively small, It is preferable that the communication channel 214-2 of the fluid element 215-2 on the working space side is configured to be relatively large. Further, when enhancing the function of the two-stage configuration, as shown in FIG. 11, the flow lines of the communication flow paths 214-1 and 214-2 of the two fluid elements 215-1 and 215-2 are offset. It is effective to be provided in. If the flow lines of the communication channels 214-1 and 214-2 of the two fluid elements 215-1 and 215-2 are deviated, the effect of suppressing the backflow increases.

(Second modification of the first embodiment)
Next, a second modification of the first embodiment will be described with reference to FIG.

  In the present embodiment, the static pressure levitation mechanism may be provided on the high temperature side cylinder 22 side. In FIG. 12, reference numeral 201 denotes a pressure accumulating chamber provided in the high temperature side cylinder 22, reference numeral 202 denotes a communication flow path, and reference numeral 203 denotes a floating static pressure supply hole (air supply hole).

  The communication flow path 202 is provided above the top dead center position of the piston 21, and communicates the working space of the high temperature side cylinder 22 and the pressure accumulation chamber 201. The communication flow path 202 has a significantly larger flow path resistance at the time of reverse flow than at the time of forward flow, and is constituted by a fluid element 204 having no movable part. That is, the fluid element 204 has a relatively small channel resistance when the flow direction of the working fluid passing through the communication channel 202 is a forward flow (a flow from the working space side toward the pressure accumulating chamber 201). In the case of (in the direction from the pressure accumulating chamber 201 toward the working space), the flow path resistance is configured to be significantly larger than that in the forward flow.

  The high temperature side cylinder 22 is provided with a plurality of air supply holes 203 at equal intervals in the circumferential direction. When the working fluid in the working space of the high temperature side cylinder 22 is compressed as the piston 21 rises and the pressure of the working fluid becomes higher than the pressure in the pressure accumulating chamber 201, the communication channel 202 is connected from the forward flow side inlet of the fluid element 204. Then, a part of the working fluid in the working space is introduced into the pressure accumulating chamber 201. When the working fluid is introduced into the pressure accumulating chamber 201 via the communication channel 202, a part of the working fluid in the pressure accumulating chamber 201 is ejected to the clearance between the piston 21 and the cylinder 22 via the air supply hole 203. . Further, when the pressure of the working fluid in the working space in the high temperature side cylinder 22 is lowered by the movement of the piston 21 by the fluid element 204, the working fluid in the pressure accumulating chamber 201 flows back to the working space in the high temperature side cylinder 22. It is suppressed.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS.
In the second embodiment, overlapping description of parts common to the above embodiment is omitted.

  13 and 14, reference numeral 301 is a working space in the high temperature side cylinder 22, reference numeral 22 g is an enlarged diameter portion of the high temperature side cylinder 22, and reference numeral 314 is a communication hole (communication) provided in the piston 21. Channel).

  As in the first embodiment, in the piston main body 211 of the piston 21, the side peripheral portion (sliding portion) 211a that slides with the high temperature side cylinder 22 is provided with a plurality of air supply holes 216 at equal intervals in the circumferential direction. It has been. In the side circumferential portion 211a, a communication channel 314 that connects the working space 301 in the high temperature side cylinder 22 and the hollow portion 212 is formed above the position where the air supply hole 216 is provided.

  The communication channel 314 is provided at a position where the hollow portion 212 and the working space 301 communicate with each other only when the piston 21 is in the vicinity of the top dead center (FIG. 14), and is closed by the wall portion of the high temperature side cylinder 22 otherwise. (FIG. 13). The communication channel 314 is a hole provided in the vicinity of the top surface portion 211 b on the side peripheral portion 211 a that faces and opposes the inner peripheral wall portion of the high temperature side cylinder 22.

  A diameter-enlarged portion 22g that is larger in diameter than the other portions is provided on the upper portion of the inner peripheral wall portion of the high temperature side cylinder 22 (the portion that forms the working space 301). The communication channel 314 is positioned at the height of the enlarged diameter portion 22g only when the piston 21 is near the top dead center, and communicates the hollow portion 212 and the working space 301 (FIG. 14). The high temperature side cylinder 22 is closed by a wall portion other than the enlarged diameter portion 22g (FIG. 13).

  That is, in the state shown in FIG. 13, the pressure of the working fluid in the working space 301 in the high temperature side cylinder 22 decreases due to the movement of the piston 21, but the clearance between the communication channel 314 and the inner peripheral wall portion of the high temperature side cylinder 22. Is as small as the clearance between the air supply hole 216 and the inner peripheral wall portion of the high temperature side cylinder 22, and the pressure in the hollow portion 212 hardly flows out to the outside.

  As shown in FIG. 14, as the piston 21 rises, the working fluid in the working space 301 of the high temperature side cylinder 22 is compressed, and the communication flow path 314 provided in the piston 21 reaches the height of the enlarged diameter portion 22g. When the clearance between the inner peripheral wall portion of the high temperature side cylinder 22 reaches the working space 301 and reaches the working space 301, a part of the working fluid in the working space 301 is introduced into the hollow portion 212 via the communication channel 314. The When the working fluid is introduced into the hollow portion 212 via the communication channel 314, a part of the working fluid in the hollow portion 212 is ejected to the clearance between the piston 21 and the cylinder 22 via the air supply hole 216. .

  As described above, the communication channel 314 is provided in the first portion corresponding to the predetermined height position in the side peripheral portion 211 a of the piston main body 211, and introduces the working fluid compressed in the working space 301 into the pressure accumulating chamber 212. Used to do. The air supply hole 216 is provided in a second portion corresponding to a position below the predetermined height position in the side peripheral portion 211 a of the piston main body 211, and from the pressure accumulation chamber 212 to between the piston main body 211 and the high temperature side cylinder 22. It penetrates the clearance part.

  In comparison between when the piston 21 is at the top dead center and when it is at the bottom dead center, the size of the clearance portion between the first portion in the side peripheral portion 211a of the piston main body 211 and the high temperature side cylinder 22 is as follows. The piston 21 is configured to be larger when the piston 21 is at the top dead center than when the piston 21 is at the bottom dead center.

  In comparison between when the piston 21 is at the top dead center and when it is at the bottom dead center, the size of the clearance portion between the second portion in the side peripheral portion 211a of the piston main body 211 and the high temperature side cylinder 22 is as follows. Are configured to be substantially the same. In comparison between the first portion and the second portion in the side peripheral portion 211a of the piston body 211, the size of the clearance portion between the piston 21 and the high temperature side cylinder 22 when the piston 21 is at the bottom dead center is approximately It is configured to be the same.

  When the piston 21 is at the top dead center, the piston 21 is at the top dead center, rather than the diameter of the inner peripheral wall portion of the high temperature side cylinder 22 that the first portion of the side peripheral portion 211a of the piston body 211 faces when the piston 21 is at the bottom dead center. The diameter of the inner peripheral wall portion 22g of the high temperature side cylinder 22 facing the first portion in the side peripheral portion 211a of the main body 211 is configured to be larger.

  As shown in FIG. 4, there is a phase shift of about 45 ° (crank angle) between the top dead center of each piston 21 and 31 and the point of the maximum value (maximum compression pressure) Pmax of the in-cylinder pressure during the compression process. In order to secure a high pressure in the hollow portion 212 and to prevent deterioration in efficiency due to the entry and exit of the working fluid between the hollow portion 212 and the working space 301, 45 ° (top dead center) near the top dead center of each piston 21, 31. The connecting flow path 314 is set to be open (state shown in FIG. 14) within 45 ° before and after the point, that is, a width of 90 °.

  As described above, the size of the clearance portion between the first portion of the side peripheral portion 211a of the piston main body 211 and the high temperature side cylinder 22 is within a range of 45 ° before and after the top dead center of the piston 21. The time is configured to be larger than when the piston 21 is outside the range.

  Also in the second embodiment, the communication hole 314 does not have a movable part like the valve body of the check valve (check valve), so it is easy to ensure reliability and life. It is suppressed that it becomes a structural restriction.

(First Modification of Second Embodiment)
A first modification of the second embodiment will be described with reference to FIGS. 15 and 16.

  As shown in FIGS. 15 and 16, the communication flow path 315 is configured by a fluid element 316 having a remarkably large flow path resistance at the time of backflow and no moving part, as in the first embodiment. . That is, the fluid element 316 has a shape in which the flow resistance is relatively small when the direction of the flow of the working fluid passing through the communication flow path 315 is forward, and the flow resistance is remarkably large at the time of reverse flow compared to the forward flow. It is configured.

  According to this modification, the effect | action which prevents the deterioration of the efficiency by the entrance / exit of the working fluid between the hollow part 212 and the working space 310 improves.

(Second Modification of Second Embodiment)
A second modification of the second embodiment will be described with reference to FIGS. 17 and 18.

  As shown in FIGS. 17 and 18, in the fluid elements 317 and 318 of the second modified example, unlike the fluid element 316 of the first modified example, a part of the working fluid in the working space 301 passes through the communication channel 315. The upper surfaces 317a and 318a of the surface forming the inlet when flowing into the hollow portion 212 are formed flat. Thereby, as the piston 21 rises, the entire upper surfaces 317a and 318a of the inlets of the fluid elements 317 and 318 reach the height of the enlarged diameter portion 22g at the same time and communicate with the working space 310. The accuracy of the period (open period) communicating with the working space 301 is improved.

(Third embodiment)
Next, a third embodiment will be described with reference to FIGS.
In the third embodiment, descriptions of parts common to the above embodiment are omitted.

  When a fluid element without an operating mechanism (movable part) is used as in the first embodiment, it is easy to ensure reliability and life, but the rise of the accumulated pressure value of the hollow part is slow at start-up, and the gas bearing The time during which the piston 21 (FIG. 1) cannot obtain sufficient levitation force becomes longer. For this reason, a special hardening process is required on the piston / cylinder surface in order to ensure wear resistance. Hereinafter, the reason why the increase in the accumulated pressure value of the hollow portion is delayed at the time of activation will be described.

  As described above, when a fluid element whose flow path resistance varies greatly depending on the flow direction (forward flow, reverse flow), it is necessary to design the introduction flow rate per unit time to be small. This is to reduce the respiration (in / out amount) of the working space and the pressure accumulation space while increasing the flow velocity. For this reason, several tens of cycles are required to start up the pressure accumulation value at the time of startup.

  Therefore, in the third embodiment, as shown in FIG. 19, a fluid element 215 and a check valve 401 are used in parallel as a pressure introducing device to the hollow portion (accumulation chamber) 212 of the piston 21. Formed on the top surface portion 211 b of the piston 21 are first and second communication channels 214 and 414 that communicate the working space in the high temperature side cylinder 22 with the hollow portion 212. The first communication channel 214 is configured by a fluid element 215 that has a relatively small channel resistance at the time of forward flow and has a significantly larger channel resistance at the time of reverse flow than at the time of forward flow. Further, a check valve 401 is provided at a position facing the second communication channel 414 in the hollow portion 212.

  The check valve 401 includes a valve body (movable part) 402, a valve seat 403, and a spring 404 that presses the valve body 402 against the valve seat 403. The check valve 401 operates only at the time of activation (the valve is opened). When the normal operation state (normal operation range) is entered, the valve body 402 stops (closes), and the function as the check valve does not work. The second communication channel 414 is always closed.

In FIG. 20, reference numeral 501 indicates the pressure in the working space of the high temperature side cylinder 22, and reference numeral 502 indicates the movement of the PF immediately after activation. As shown in FIGS. 20 and 21, when the pressure increase pressure amplitude with respect to the average value (average pressure) Pmean of the working space pressure 501 is P _{+ P} and the saturated pressure accumulation value PF by the fluid element 215 is opened, the check valve 401 is opened. The check valve 401 exhibits the above-described function when the pressure set value Pc is designed as follows.
Pc <P _{+ P} , and
_{Pc> (P + P + PF} ), or, (Pc + PF)> P + P

At startup, when PF is small, P _{+ P} overcomes the valve opening pressure setting value Pc of the check valve 401 to open the check valve 401, and the hollow portion 212 introduces pressure from the second communication channel 414. When the PF increases (the accumulated pressure value of the hollow portion 212 increases after activation), the check valve 401 does not open, and the valve body 402 of the check valve 401 is fixed to the valve seat 403 and does not move.

  The valve opening pressure setting value Pc of the check valve 401 is designed based on the force of the spring 404 and the seat area, as shown in FIG. As shown in FIG. 23, the reed valve 430 is also achieved by applying a residual stress corresponding to the valve opening pressure setting value Pc to the reed 431 (in the seat state). In FIG. 23, reference numeral 432 is a valve guide.

  According to the third embodiment, the accumulated pressure value of the hollow portion 212 can be raised relatively early via the check valves 401 and 430 at the time of activation (including immediately after activation). In addition, since the movable parts 402 and 431 of the check valves 401 and 430 remain stopped (closed) after the pressure accumulation value of the hollow part 212 is raised to a predetermined value at the time of activation, it is described in the first embodiment. As described above, the problem of reliability, reliability, and durability of operation is suppressed.

(First Modification of Third Embodiment)
A first modification of the third embodiment will be described with reference to FIGS.

  As shown in FIG. 22 or FIG. 23, the check valves 401 and 430 are arranged so that the moving direction of the movable parts 402 and 431 of the check valves 401 and 430 coincides with the vertical (acceleration) direction of the piston 21. , 431, the piston device with better characteristics can be obtained as compared with the third embodiment.

  In FIG. 24, reference numeral 503 indicates the amount of increase in the valve opening pressure due to the maximum upward acceleration (the top dead center of the piston 21) acting on the movable parts 402 and 431 of the check valves 401 and 430. . As shown in the figure, it is shown that the valve opening pressure increase 503 due to the maximum upward acceleration acting on the movable parts 402 and 431 increases in accordance with the rotational speed [rpm] of the Stirling engine 10.

  On the other hand, reference numeral 504 indicates an increase in valve closing pressure due to the maximum downward acceleration (bottom dead center of the piston 21) acting on the movable parts 402 and 431 of the check valves 401 and 430. Yes. As shown in the figure, it is shown that the valve closing pressure increase 504 due to the maximum downward acceleration acting on the movable parts 402 and 431 increases according to the rotational speed of the Stirling engine 10.

As shown in FIG. 24, when the valve opening pressure increase due to the maximum upward acceleration acting on the movable parts 402 and 431 of the check valves 401 and 430 at the rotation speed N1 set lower than the normal operation range is PA, The valve opening pressure Pc ′ of the movable parts 402 and 431 of the check valves 401 and 430 is as follows.
Pc ′ ≦ (P _{+ P−} PA), and
Pc ′ + PA <(P _{+ P−} PF) or Pc ′> (P _{+ P−} PF−PA)

  In order to satisfy the above, according to this modification, the valve opening pressure Pc ′ of the movable parts 402 and 431 of the check valves 401 and 430 is compared with the valve opening pressure setting value Pc of the third embodiment. It can be designed to be smaller by the amount of PA (for example, the check valve 401 can be designed to weaken the force of the spring 404), and the check valves 401 and 430 can be easily opened at the initial stage of startup, thereby reducing the number of cycles at the initial stage of startup. The pressure accumulation value of the hollow portion 212 can be raised.

  In this modification, as the rotational speed of the Stirling engine 10 increases, the valve opening pressure increase 503 due to the maximum upward acceleration acting on the movable parts 402 and 431 increases, and the check valves 401 and 430 are difficult to open. , The valve opening pressure Pc ′ of the movable parts 402 and 431 of the check valves 401 and 430 can be designed to be small. Thereby, when the rotation speed of the Stirling engine 10 is low (starting up), the check valves 401 and 430 can be easily opened, and the pressure accumulation value of the hollow portion 212 can be raised with a smaller number of cycles.

When the piston 21 is at the bottom dead center, the valve closing pressure increase due to the maximum downward acceleration acts on the movable parts 402 and 431. At this time, the working space of the high temperature side cylinder 22 is greater than the pressure accumulating chamber of the hollow part 212. Therefore, even if the valve opening pressure Pc ′ of the movable parts 402 and 431 of the check valves 401 and 430 is designed to be small, the check valves 401 and 430 are difficult to open. Even if the rotation speed of the Stirling engine 10 is increased and the valve closing pressure increase 504 due to the maximum downward acceleration acting on the movable parts 402 and 431 is increased, the valve closing pressure increase 504 is (Pc ′ + PF−P _{−). If P} ) is not exceeded, the check valves 401 and 430 are not opened. In the example of FIG. 24, until the speed is 3000 rpm, the valve closing pressure rise 504, to indicate by reference numeral 505 _{(Pc '+ PF-P -P} ), not above, the check valve 401,430 is not open It has been shown.

In this modification, in view of the above, the design is made such that the valve closing pressure increase 504 does not exceed (Pc ′ + PF−P _−P ) 505 at a predetermined rotation speed in the practical operation range. Alternatively, by reducing the mass of the movable portions 402 and 431 of the check valves 401 and 430 and reducing the inclination of the valve closing pressure increase 504 that increases according to the rotation speed, at a predetermined rotation speed in the practical operation range, It is designed so that the valve closing pressure increase 504 does not exceed (Pc ′ + PF−P _−P ) 505.

  Even if the rotational speed increases or the mass of the movable parts 402 and 431 of the check valves 401 and 430 is large, the valve closing pressure increase due to the downward maximum acceleration with respect to the movable parts 402 and 431 In order to suppress the opening of the check valves 401 and 430 at the bottom dead center of the piston 21 without affecting the effect of the reference numeral 504, as shown in FIG. What is necessary is just to comprise so that it may not correspond with the up-down (acceleration) direction of 21.

(Second Modification of Third Embodiment)
A second modification of the third embodiment will be described with reference to FIGS.

  Small chambers (buffers) 610 and 620 are provided between the check valves 440 and 450 shown in FIGS. 25 and 26 and the working space of the high temperature side cylinder 22, respectively. The small chambers 610 and 620 communicate with the working space via the orifices 611 and 621, respectively. In FIG. 25, reference numeral 441 is a spring of the check valve 440, reference numeral 442 is a communication hole to the pressure accumulating chamber, and reference numeral 443 is an introduction hole for the working fluid. In FIG. 26, reference numerals 451 and 452 denote a valve body and a spring of the check valve 450, respectively.

  FIG. 27 shows that the cycle of fluctuation of the pressure 501 in the working space is shortened with time (the rotational speed of the Stirling engine 10 is increased). In FIG. 28, reference numeral 509 indicates the pressure in the small chambers 610 and 620.

As shown in FIG. 27, when the number of revolutions increases after the start-up and the pressure fluctuation period in the working space becomes shorter, the pressure in the small chambers 610 and 620 corresponding to the pressure fluctuation in the working space as shown in FIG. The amplitude is reduced, and the peak pressure on the high pressure side is the valve opening pressure set value Pc of the check valves 440 and 450.
Lower than. Thereby, the check valves 440 and 450 are fixed in a closed state.

  In this modification, by providing the small chambers 610 and 620 communicated with the working space by the orifices 611 and 621 between the check valves 440 and 450 and the working space, the rotational speed of the Stirling engine 10 is increased (the working space is reduced). The valve opening pressure Pc of the check valves 440 and 450 can be designed to be small by utilizing the fact that the check valves 440 and 450 are difficult to open in accordance with the pressure fluctuation period becoming smaller. Thereby, when the rotation speed of the Stirling engine 10 is low (starting up), the check valves 440 and 450 can be easily opened, and the pressure accumulation value of the hollow portion 212 can be raised with a smaller number of cycles.

In the present modification, the valve opening pressure setting described in the third embodiment is provided by providing the small chambers 610 and 620 communicated with the working space through the orifices 611 and 621 between the check valves 440 and 450 and the working space. Even when the condition for the value Pc is not satisfied, it is possible to operate the check valve only at the time of startup and to close the check valve in the normal operation range.
In addition, this modification can be combined with the said 3rd Embodiment or the 1st modification of the said 3rd Embodiment.

It is a front sectional view showing a first embodiment of the piston device of the present invention. It is a front sectional view showing the important section of a first embodiment of the piston device of the present invention. 1 is a front view showing a first embodiment of a Stirling engine of the present invention. It is a graph explaining the cylinder pressure of 1st Embodiment of the Stirling engine of this invention. It is explanatory drawing for demonstrating the linear approximation mechanism applied in 1st Embodiment of the Stirling engine of this invention. It is a front sectional view showing the important section of another example of the first embodiment of the piston device of the present invention. It is a front sectional view showing an important part of still another example of the first embodiment of the piston device of the present invention. It is a front sectional view showing an important part of still another example of the first embodiment of the piston device of the present invention. It is a front sectional view showing the first modification of the first embodiment of the piston device of the present invention. It is a front sectional view showing another example of the first modification of the first embodiment of the piston device of the present invention. It is a front sectional view showing still another example of the first modification of the first embodiment of the piston device of the present invention. It is a front sectional view showing a main part of a second modification of the first embodiment of the Stirling engine of the present invention. It is a front sectional view showing one operation state of a second embodiment of the piston device of the present invention. It is a front sectional view showing another operation state of the second embodiment of the piston device of the present invention. It is a front sectional view showing the first modification of the second embodiment of the piston device of the present invention. It is a front sectional view showing the important section of the first modification of the second embodiment of the piston device of the present invention. It is explanatory drawing which shows the principal part of the 2nd modification of 2nd Embodiment of the piston apparatus of this invention. It is explanatory drawing which shows the principal part of the 2nd modification of 2nd Embodiment of the piston apparatus of this invention. It is a front sectional view showing a third embodiment of the piston device of the present invention. It is a graph which shows the pressure of working space, and the saturation pressure accumulation value by a fluid element in 3rd Embodiment of the piston apparatus of this invention. It is explanatory drawing explaining the valve opening pressure setting value of a check valve in 3rd Embodiment of the piston apparatus of this invention. It is a front sectional view showing the important section of the first modification of the third embodiment of the piston device of the present invention. It is a front sectional view showing the important section of another example of the first modification of the third embodiment of the piston device of the present invention. It is explanatory drawing explaining the valve opening pressure setting value of a check valve in the 1st modification of 3rd Embodiment of the piston apparatus of this invention. It is a front sectional view showing the important section of the second modification of the third embodiment of the piston device of the present invention. It is a front sectional view showing the important section of another example of the second modification of the third embodiment of the piston device of the present invention. It is a graph which shows the cycle of the fluctuation | variation of the pressure of a working space in the 2nd modification of 3rd Embodiment of the piston apparatus of this invention. It is a graph which shows the pressure fluctuation of a small chamber in the 2nd modification of 3rd Embodiment of the piston apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Stirling engine 20 High temperature side power piston 21 Expansion piston 211 Piston main body 211a Side peripheral part 211b Top surface part 212 Hollow part (pressure accumulation chamber)
214 Communication channel 215 Fluid element 216 Air supply hole 22 High temperature side cylinder 22b Top portion of high temperature side cylinder 30 Low temperature side power piston 31 Compression piston 32 Low temperature side cylinder 45 Cooler 46 Regenerator 46a Regenerator upper surface 46b Regenerator lower surface 47 Heating Device 47a First end portion 47b Second end portion 48 Air bearing 50 Approximate linear mechanism 60 Piston pin 100 Exhaust pipe Pmax Maximum value of in-cylinder pressure W In-cylinder pressure (composite waveform)

Claims (5)

A piston device;
An external combustion engine equipped with a cylinder,
The piston device is
A piston body;
A pressure accumulating chamber formed inside the piston body;
An introduction portion for introducing a working medium compressed in the working space of the external combustion engine into the pressure accumulating chamber, provided in a first portion corresponding to a predetermined height position in a side circumferential portion of the piston body;
A hole provided in a second portion corresponding to a position lower than the predetermined height position in a side peripheral portion of the piston body, and penetrating from the pressure accumulating chamber to a clearance portion between the piston body and the cylinder; With
In comparison between the time when the piston device is at the top dead center and the time when the piston device is at the bottom dead center, the size of the clearance portion between the first portion in the side periphery of the piston body and the cylinder is An external combustion engine configured to be larger when the piston device is at the top dead center than when the piston device is at the bottom dead center. In the external combustion engine according to claim 1,
In comparison between when the piston device is at the top dead center and when the piston device is at the bottom dead center, the size of the clearance portion between the second portion in the side peripheral portion of the piston body and the cylinder is approximately Configured to be the same,
In the comparison between the first part and the second part in the side periphery of the piston body, the size of the clearance part between the cylinder and the cylinder when the piston device is at bottom dead center is substantially the same. An external combustion engine characterized by being configured as follows. In the external combustion engine according to claim 1 or 2,
When the piston device is at the top dead center, the piston device is at the top dead center, rather than the diameter of the inner peripheral wall portion of the cylinder facing the first portion of the side periphery of the piston body when the piston device is at the bottom dead center. An external combustion engine characterized in that a diameter of an inner peripheral wall portion of the cylinder facing the first portion in a side peripheral portion of the main body is larger. In the external combustion engine according to any one of claims 1 to 3,
The external combustion engine is an α-type Stirling engine,
The size of the clearance portion between the first portion and the cylinder in the side periphery of the piston body is greater when the piston device is in a range within 45 ° before and after top dead center. An external combustion engine characterized in that it is configured to be larger than when the apparatus is out of the above range. In the external combustion engine according to any one of claims 1 to 4,
The upper surface of the introduction part is formed in a flat shape so as to have substantially the same height.

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