JP2006188956A - Piston engine - Google Patents

Abstract

When a piston movement direction intersects with an action direction of gravity, the piston is quickly lifted from a cylinder after the piston starts moving.
The piston engine includes a piston 21 that reciprocates in a cylinder 22 and whose movement direction is orthogonal to the vertical direction and in which a pressure accumulating chamber 212 is formed inside a piston main body 211. The pressure accumulating chamber 212 and the inside of the cylinder 22 are communicated with each other by a fluid introduction unit 214, and the working fluid in the cylinder 22 is introduced into the pressure accumulating chamber 212. The side circumferential portions 211a ₁ and 211a ₂ of the piston 21 are provided with a plurality of air supply holes 216 and 217 that eject the gas taken into the pressure accumulating chamber 212 between the side surface of the piston 21 and the cylinder 22. ing. The air supply holes 216 and 217 are arranged more in the lower vertical direction LS than in the upper vertical direction US.
[Selection] Figure 4

Description

  The present invention relates to a piston device, and more particularly to a piston engine in which a piston reciprocates in a cylinder without using a piston ring or lubricating oil.

  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 Patent Document 1 is known.

  The piston of the external combustion engine disclosed in Patent Document 1 is a Stirling engine of a type 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 prevents the working medium in the pressurizing chamber from flowing back into the working space. A check valve and an orifice for ejecting the working medium in the pressurizing chamber to the clearance between the piston and the cylinder are provided.

JP 2000-46431 A

  By the way, when forming the air bearing by ejecting the working fluid from the orifice, if the piston is arranged so that the direction of movement of the piston intersects with the direction of action of gravity, the piston starts to move and the air bearing A certain amount of time is required until the piston is lifted from the cylinder. For this reason, the piston and the cylinder come into contact with each other under the influence of gravity during the period from when the piston starts to move to when the piston rises from the cylinder. In the technique disclosed in Patent Document 1, since this point is not taken into consideration, if the contact time between the piston and the cylinder is long, the wear of the piston or the cylinder may increase, and the durability of these may be shortened. is there. This wear becomes more prominent as the direction of motion of the piston becomes perpendicular to the direction of gravity action.

  Accordingly, the present invention has been made in view of the above, and a piston that takes in the working fluid from the working space into the hollow portion provided in the piston via the pressurized state holding means and ejects it from the piston side peripheral portion. In the engine, when the movement direction of the piston intersects the direction of gravity action, after the piston starts moving, the piston is quickly lifted from the cylinder to provide a piston engine that can suppress the deterioration of the durability of the piston and the cylinder. The purpose is to do.

  In order to achieve the above-described object, a piston engine according to the present invention includes a piston that reciprocates in a cylinder and whose movement direction intersects the vertical direction, and a hollow portion formed in the piston. And a fluid introduction part for communicating the hollow part and the inside of the cylinder, introducing the working fluid in the cylinder into the hollow part by the movement of the piston, and a side peripheral part of the piston on the upper side in the vertical direction, A plurality of air supply holes provided on the side periphery of the piston on the lower side in the vertical direction to eject the working fluid introduced into the hollow portion between a side surface of the piston and the cylinder; It is characterized by.

  In this piston engine, when the working fluid taken into the hollow portion provided in the piston is ejected from the piston side peripheral portion, the air supply hole provided in the piston side peripheral portion is vertically A larger number is arranged on the lower side in the vertical direction than the upper side in the direction. As a result, the working fluid (for example, air) introduced into the hollow portion by the movement of the piston immediately starts to be ejected from the air supply hole of the piston, and then the force of floating the piston generated by the air supply hole arranged on the lower side in the vertical direction. It is possible to create a state in which the difference between the sum and the sum of the forces that lift the piston generated by the air supply holes arranged on the upper side in the vertical direction becomes larger. As a result, after the piston starts to move, the piston can be quickly lifted from the cylinder, and the contact between the piston and the inner wall of the cylinder can be minimized to suppress a decrease in the durability of the piston and the cylinder.

  In the piston engine according to the next aspect of the present invention, in the piston engine, the air supply hole provided in the side peripheral portion of the piston on the lower side in the vertical direction is configured so that the movement direction of the piston and the action direction of gravity are orthogonal to each other. In the case where the piston is arranged, the piston is arranged symmetrically with respect to the center of gravity with respect to the sum of the side pressures of the piston due to gravity.

  In the piston engine according to the next aspect of the present invention, in the piston engine, an air supply hole provided in a side peripheral portion of the piston on the upper side in the vertical direction is at a point opposite to the center of gravity point with respect to the central axis of the piston. It is characterized by being symmetrically arranged.

  In the piston engine according to the next aspect of the present invention, in the piston engine, an air supply hole provided in a side peripheral portion of the piston on the lower side in the vertical direction intersects the movement direction of the piston and the action direction of gravity. And when the piston is stationary, the piston and the cylinder are shifted from the contact portion.

  The piston engine according to the present invention is characterized in that, in the piston engine, the air supply holes are arranged at substantially equal intervals with respect to a circumferential direction of the piston.

  In the piston engine according to the next aspect of the present invention, in the piston engine, when the working fluid flows out from the hollow portion, the fluid introduction portion flows out of the flow path resistance when the working fluid flows into the hollow portion. It is a fluid element having a larger flow path resistance and having no movable part.

  A piston engine according to the present invention is a piston engine in which a working fluid is taken in from a working space into a hollow portion provided in the piston through a pressurized state holding means and ejected from a piston side peripheral portion. In the case of crossing the direction of operation, after the piston starts to move, the piston can be quickly lifted from the cylinder, and the durability of the piston and the cylinder can be suppressed from decreasing.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the best mode for carrying out the invention. In addition, constituent elements in the best mode for carrying out the invention include those that can be easily assumed by those skilled in the art or those that are substantially the same. In the following, a Stirling engine is taken as an example of a piston engine. An example in which exhaust heat of an internal combustion engine mounted on a vehicle or the like is recovered using a Stirling engine will be described, but the exhaust heat recovery target is not limited to the internal combustion engine. For example, the present invention can also be applied to recovering waste heat from a factory, plant, or power generation facility.

  The piston engine according to this embodiment is a piston engine that introduces a working fluid from a working space in a cylinder into a hollow portion in the piston and ejects the fluid between a side peripheral portion of the piston and the cylinder. And the air supply hole provided in the side peripheral part of a piston has the characteristics in the point which is different by the vertical direction upper side and vertical direction lower side of a piston. More specifically, the air supply hole provided in the side peripheral portion of the piston is characterized in that there are more on the lower side in the vertical direction than on the upper side in the vertical direction of the piston.

  FIG. 1 is a cross-sectional view showing a piston engine according to this embodiment. FIG. 2 is an explanatory diagram showing an example of a state in which exhaust heat of the internal combustion engine is recovered by the piston engine according to this embodiment. FIG. 3 is a front view showing an example in which the piston engine according to this embodiment is arranged under the floor of the vehicle. As shown in FIG. 1, a Stirling engine 10 according to this embodiment is an α-type (two-piston type) Stirling engine, and includes high-temperature side and low-temperature side piston / cylinder portions 20 and 30. As shown in FIG. 1, the high temperature side and low temperature side piston / cylinder parts 20, 30 are arranged in series. The piston 31 of the low temperature side piston / cylinder part 30 has a phase difference of about 90 ° in crank angle with respect to the piston 21 of the high temperature side piston / cylinder part 20.

  The piston 21 of the high temperature side piston / cylinder portion 20 is housed in a cylinder (high temperature side cylinder) 22 and reciprocates therein. Further, the piston 31 of the low temperature side piston / cylinder portion 30 is housed in a low temperature side cylinder 32, and reciprocates within this. The working fluid heated by the heater 47 flows into the space on the heater 47 side of the high temperature side cylinder 22 (hereinafter referred to as the expansion space ES). The working fluid cooled by the cooler 45 flows into the space (hereinafter referred to as compression space PS) on the side of the regenerative heat exchanger (hereinafter referred to as regenerator) 46 of the cylinder (low temperature side cylinder) 32. Note that the expansion space ES and the compression space PS are also called working spaces.

  The regenerator 46 stores heat when the working fluid reciprocates between the expansion space ES and the compression space PS. That is, when the working fluid flows from the expansion space ES to the compression space PS, the regenerator 46 receives heat from the working fluid, and operates the stored heat when the working fluid flows from the compression space PS to the expansion space ES. Pass to fluid.

  As the two pistons 21, 31 reciprocate, the reciprocating flow of the working gas occurs, and the ratio of the working fluid in the expansion space ES of the high temperature side cylinder 22 and the compression space PS of the low temperature side cylinder 32 changes. As the total volume also changes, pressure fluctuations occur. Comparing the pressures when the two pistons 21 and 31 are in the same position, the piston 21 is considerably higher when it is lowered than when it is raised, while the piston 31 is lower. For this reason, the piston 21 needs to perform a large positive work (expansion work) to the outside, and the 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.

  As shown in FIG. 1, the drive shaft 40 is connected to a crankshaft 43 stored in a crankcase 41. The crankshaft 43 is connected to the two pistons 21 and 31 via the piston side connecting rod 61, the connecting pin 60, and the connecting rod 109. The crankshaft 43 converts the reciprocating motion of the two pistons 21, 31 into a rotational motion and transmits it to the drive shaft 40.

  The higher the average pressure of the working fluid (air in this embodiment), the larger the pressure difference with respect to the same temperature difference due to the cooler 45 and the heater 47, so that a higher output is obtained from the Stirling engine 10. . Since the average pressure of the working fluid becomes the pressure in the crankcase 41, it is preferable to pressurize the crankcase 41 with a pressurizing unit so as to extract more output from the Stirling engine 10.

  As shown in FIG. 2, the Stirling engine 10 according to this embodiment is used in a vehicle together with an internal combustion engine 220 such as a gasoline engine. That is, the Stirling engine 10 is driven using the exhaust gas Ex of the internal combustion engine 220 such as a gasoline engine as a heat source. The heater 47 of the Stirling engine 10 is disposed inside the exhaust pipe 100 of the internal combustion engine 220 mounted on the vehicle, and the working fluid is heated by the thermal energy recovered from the exhaust gas Ex, so that the Stirling engine 10 operates. In this embodiment, the Stirling engine 10 drives the generator 225 using the exhaust gas Ex of the internal combustion engine 220 as a heat source.

  Since the Stirling engine 10 according to this embodiment is installed in a limited space in the vehicle such that the heater 47 is accommodated in the exhaust pipe 100, the installation is more compact. The degree of freedom increases, which is preferable. Therefore, the Stirling engine 10 employs a configuration in which the two high-temperature side and low-temperature side 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 high temperature of the heater 47 is set on the upstream side (a side close to the gasoline engine) 100 a of the exhaust gas in which a relatively high temperature exhaust gas flows inside the exhaust pipe 100. The 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 this 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. Further, 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, which is the exhaust heat recovery target.

  A substrate 42 is fixed to the flange 100f of the exhaust pipe 100 via a heat insulating material. 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 considered 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.

  The exhaust pipe 100 and the Stirling engine 10 are attached via a substrate 42. At this time, the substrate 42, the end surface of the high temperature side cylinder 22 to which the heater 47 is connected (the side to which the heater 47 of the top portion 22 b is connected), and the low temperature side cylinder 32 to which the cooler 45 is connected. The Stirling engine 10 is attached to the substrate 42 so that its end face (top face 32a) is substantially parallel.

  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.

As shown in FIG. 3, when the Stirling engine 10 according to this embodiment is mounted on a vehicle 200, for example, it is mounted under the floor of the vehicle 200. Then, it is placed horizontally in a space adjacent to the exhaust pipe 100 arranged under the floor of the vehicle 200. That is, the axial directions of the high temperature side cylinder 22 and the low temperature side cylinder 32 are arranged substantially parallel to the vehicle floor 200up, and the two pistons 21 and 31 reciprocate in the horizontal direction ( Arrow C direction in FIG. 3). At this time, the two pistons 21 and 31 reciprocate in the vertical direction, that is, in a direction perpendicular to the direction of action of gravity (the direction of arrow G in FIG. 3). As shown in FIG. 4 to be described later, the configuration disclosed in this embodiment can be applied when a component in the direction of gravity acts on the side peripheral portions 211a ₁ and 211a ₂ of the piston 21. Therefore, the configuration disclosed in this embodiment can be applied to the case where the pistons 21 and 22 move in the vertical direction, that is, the direction intersecting with the direction of action of gravity.

  Minute clearances are provided between the outer peripheral surfaces of the pistons 21 and 31 and the inner walls of the cylinders 22 and 32, respectively. A working fluid (a gas, which is air in this embodiment) of the Stirling engine 10 is interposed in the clearance to constitute an air bearing 48. Here, the air bearing 48 uses the pressure (distribution) of the working fluid generated by the minute clearance between the pistons 21 and 31 and the cylinders 22 and 32 to bring the pistons 21 and 31 into the cylinders 22 and 32. Let it float.

  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. A solid lubricant may be attached to the inner walls of the cylinders 22 and 32. Although the sliding resistance of the working fluid of the air bearing 48 is originally very low, the sliding resistance between the piston and the cylinder can be reduced when the function of the air bearing is insufficient, such as when stopping and starting. is there.

  The air bearing 48 (see FIG. 1) introduces working fluid compressed in the working space of the Stirling engine 10 into the pistons 21 and 31, and from a plurality of holes provided in the side peripheral portions of the pistons 21 and 31. This is a static pressure air bearing configured by jetting into a clearance portion between the pistons 21 and 31 and the cylinders 22 and 32. The static pressure gas bearing jets pressurized fluid and floats an object (in this embodiment, pistons 21 and 31) by the generated static pressure.

  In this embodiment, since the heat source of the Stirling engine 10 is the exhaust gas Ex of the internal combustion engine 220 of the vehicle 200, the amount of heat obtained is limited, and the Stirling engine 10 is effectively operated within the range of the obtained heat amount. There is a need. Therefore, as shown in FIG. 1, the side to which the heater 47 of the top portion 22b of the high temperature side cylinder 22 is connected and the side surface 22c of the high temperature side cylinder 22 are heated so that the working fluid as hot as possible flows into the expansion space ES. The side to which the vessel 47 is connected is disposed inside the exhaust pipe 100. Thereby, in the vicinity of the top dead center, the piston top 211t of the expansion-side piston 21 is positioned inside the exhaust pipe 100, and the piston top 211t of the expansion-side piston 21 is effectively heated.

  Here, in the Stirling engine 10 according to this embodiment, the substrate 42 is disposed on the working fluid introduction side of the high temperature side and low temperature side cylinders 22 and 32, and both cylinders are assembled to the substrate 42. With such a configuration, the high temperature side and low temperature side cylinders 22 and 32 are restrained, and an increase in the distance between the high temperature side cylinder 22 and the low temperature side cylinder 32 is suppressed. As a result, even when the heater 47 becomes hot during operation of the Stirling engine 10, the clearance between the cylinder and the piston can be maintained and the function of the air bearing 48 can be exhibited.

  Next, the configuration of the pistons 21 and 31 will be described in detail. Here, as shown in FIG. 1, the sizes of the pistons 21 and 31 are different, but the structure is common. Since the piston 21 and the piston 31 according to this embodiment both have a common configuration, the piston 21 will be described below, and the description of the piston 31 will be omitted.

  FIG. 4 is a sectional view showing a piston provided in the piston engine according to this embodiment. FIG. 5 is a plan view of the piston according to this embodiment as viewed from the top surface side. FIG. 6 is an explanatory view showing a state in which the piston according to this embodiment is viewed from the direction of arrow B in FIG. FIG. 7 is an explanatory view showing a state in which the piston according to this embodiment is viewed from the direction of arrow A in FIG.

  The piston 21 includes a piston main body 211, a hollow portion (hereinafter referred to as a pressure accumulating chamber) 212 formed inside the piston main body 211 (that is, the inside of the piston 21), and a partition member 213. In this embodiment, the partition member 213 is attached to the inner wall 211 iw of the piston 21 at the bottom portion 211 s of the piston main body 211. And as shown in FIG. 4, the partition member 213 is comprised so that the piston pin 62 for attaching the piston 21 to the piston side connection rod 61 may be avoided. With such a configuration, the piston main body 211 is closed by the partition member 213 on the piston top 211t side and the piston skirt 211s side, and the pressure accumulation chamber 212 is formed inside.

The piston main body 211 has a high temperature side cylinder 22 (FIG. 1) and side peripheral portions (sliding portions) 211a ₁ and 211a ₂ that slide, and a top surface portion 211b that is integrally (continuously) provided in a lid shape. is doing. A fluid introduction part 214 for communicating the working space in the high temperature side cylinder 22 and the pressure accumulating chamber 212 and introducing the working fluid in the working space into the pressure accumulating chamber 212 is provided at the center of the top surface portion 211b. In this embodiment, the fluid introduction part 214 is composed of a fluid element, which will be described in detail later.

As shown in FIGS. 4 and 5, the side peripheral portions 211 a ₁ and 211 a ₂ of the piston main body 211 are provided with a plurality of air supply holes 216 and 217. In the following description, for convenience of explanation, the air supply hole arranged on the vertical upper side US of the piston 21 is referred to as a first air supply hole 216, and the air supply hole arranged on the lower vertical side LS of the piston 21 is the second air supply hole. The air supply hole 217 is used. Further, the side circumferential portion of the piston 21 on the upper side US in the vertical direction is referred to as a _first side circumferential portion 211a _1, and the side circumferential portion on the lower side LS in the vertical direction of the piston 21 is referred to as a _second side circumferential portion 211a ₂ . Then, when focusing on a position where each of the feed holes 216 and 217 are arranged, a first gas supply hole 216, a second gas supply hole 217, a first side peripheral portion 211a _1, second side periphery The two are distinguished as 211a ₂ .

  Here, the vertical upper side US means that the piston 21 is arranged so that the direction of motion of the piston 21 (the direction of arrow C in FIG. 4) is orthogonal to the direction of gravity action (the direction of arrow G in FIG. 4). Above the plane (plane indicated by Y in FIG. 5, hereinafter referred to as the boundary plane) passing through the central axis (piston central axis) Z of the piston 21 and orthogonal to the gravity action direction (opposite to the gravity action direction). ). Further, the lower LS in the vertical direction means that the piston 21 is arranged so that the direction of motion of the piston 21 (the direction of arrow C in FIG. 4) is perpendicular to the direction of gravity action (the direction of arrow G in FIG. 4). The side below the boundary plane (the direction in which the gravity acts).

  FIG. 8 is a cross-sectional view showing the air supply holes according to this embodiment. FIG. 9 is a plan view showing the air supply holes according to this embodiment. The air supply hole 217 (216) includes an orifice 217o (216o) and an enlarged portion 217s (216s). The working fluid spreads through the orifice 217o (216o) at the enlarged portion 217s (216s) and is ejected to the clearance between the piston 21 and the high temperature side cylinder 22. The enlarged portion 217s (216s) has a function of accumulating and accumulating the working fluid ejected from the orifice 217o (216o). Therefore, when the piston 21 is started, the pressure receiving area is increased, and the piston 21 is stably stabilized with a larger force. Can surface.

When the clearance between the piston 21 and the high temperature side cylinder 22 changes after the piston 21 starts reciprocating, the flow rate is adjusted by the orifice 217o (216o). As a result, the clearance between the piston 21 and the high temperature side cylinder 22 is kept substantially constant. The diameter D ₁ of the orifice 217o (216o), and the diameter D ₂ of the enlarged portion 217s (216s), appropriately modified specification of the Stirling engine 10 and the piston 21 or by the operating conditions and the like.

  When the piston 21 moves to the top dead center side, the working fluid in the working space of the high temperature side cylinder 22 flows from the fluid introduction part 214 into the pressure accumulating chamber 212. Here, the fluid introduction part according to this embodiment will be described. As already described, the fluid introduction part 214 is composed of a fluid element. FIG. 10 is a cross-sectional view showing a fluid introducing portion according to this embodiment. In the fluid introduction part 214, the flow path resistance is remarkably increased in the reverse flow (the flow when the working fluid flows out from the pressure accumulation chamber 212) compared to the forward flow (the flow when the working fluid is introduced into the pressure accumulation chamber 212). Characteristics are required. For this reason, the fluid element which comprises the fluid introduction part 214 which concerns on this Example is comprised as follows.

In the fluid element, the curvature R2 of the top surface side opening 214ow is relatively larger than the curvature R1 of the pressure accumulation chamber side opening 214C. The curvature R1 of the pressure accumulating chamber side opening 214C is set to be extremely small and is preferably close to 0 as much as possible. Top side opening 214ow forms the projection without smooth surface, the accumulation chamber side opening 214C protrudes, the protrusion height h ₂ is formed. Further, an angle θ formed by the end surface 214S of the pressure accumulating chamber side opening 214o ₁ and the passage axis of the introduction passage 214H is formed as an acute angle. With such a configuration, the working fluid smoothly flows from the top surface opening 214o ₂ into the pressure accumulating chamber 212, but the working fluid hardly flows out through the pressure accumulating chamber side opening 214o ₁ . As a result, when the piston 21 reciprocates, the pressure of the working fluid stored in the pressure accumulating chamber 212 (pressure in the pressure accumulating chamber) Pp increases and gradually approaches a constant value. Note that a check valve may be configured using a reed valve instead of the fluid element, and this may be used as the fluid introduction unit 214.

  Due to the reciprocating motion of the piston 21, a part of the working fluid in the working space is introduced into the pressure accumulating chamber 212 through the fluid introduction part 214. Then, a part of the working fluid in the pressure accumulating chamber 212 is ejected to the clearance between the piston 21 and the high temperature side cylinder 22 through the air supply holes 216 and 217 to constitute the air bearing 48 (see FIG. 1). The clearance size tc (FIG. 4) is about 15 μm to 30 μm. Next, the arrangement of the air supply holes 216 and 217 will be described.

FIG. 11 is a conceptual diagram showing a state immediately after the piston engine according to this embodiment starts to move and starts to eject the working fluid from the air supply holes. In the piston 21 according to this embodiment, immediately after the working fluid introduced into the pressure accumulating chamber 212 by the movement of the piston 21 starts to be ejected from the air supply holes 216 and 217, the piston 21 is formed by the air supply hole 217 on the lower side LS in the vertical direction. The air supply holes 216 and 217 are arranged on the side periphery of the piston 21 so that the difference between the sum of the forces that float the air and the total force that causes the piston 21 to float from the high temperature side cylinder 22 by the air supply holes 216 on the upper side US in the vertical direction becomes larger. 211a ₁ and 211a ₂ are provided. Here, the force that lifts the piston 21 refers to a force that causes the piston 21 to move away from the high temperature side cylinder 22.

In order to realize this, for example, as shown in FIGS. 4 to 7, more second air supply holes 217 in the lower vertical direction LS than the first air supply holes 216 in the upper vertical direction US are provided. That is, the air supply holes 216 and 217 are provided more in the second side peripheral portion 211a ₂ of the piston 21 in the vertical lower side LS than in the first side peripheral portion 211a ₁ of the piston 21 in the vertical upper side US. become.

  When the piston 21 starts to move, the fluid in the working space is introduced from the fluid introduction part 214 into the pressure accumulating chamber 212. At this time, the pressure accumulating chamber pressure Pp gradually increases, so that the piston 21 is moved against gravity. A certain amount of time is required to float from the high pressure side cylinder 22. Until the piston 21 floats, the piston main body 211 of the piston 21 and the inner wall 22iw of the high temperature side cylinder 22 come into contact with each other and slide, so that the wear of both contact surfaces easily proceeds.

Here, since the pressure accumulation chamber pressure Pp in the pressure accumulation chamber 212 of the piston 21 is constant, the force to lift the piston 21 from the high temperature side cylinder 22 increases as the number of air supply holes increases. In this embodiment, more second air supply holes 217 in the lower vertical direction LS are provided than in the first air supply holes 216 in the upper vertical direction US. Therefore, immediately after the air starts to be ejected from the air supply hole of the piston 21, the sum of the force F ₂ that floats the piston 21 generated by the second air supply hole 217 and the piston 21 generated by the first air supply hole 216 are It is possible to create a state in which the difference from the sum of the floating force F ₁ becomes larger (the sum of F ₂ > the sum of F ₁ ). Accordingly, the piston 21 can be lifted from the high temperature side cylinder 22 immediately after the piston 21 starts to move. As a result, the contact between the piston main body 211 and the inner wall 22iw of the high temperature side cylinder 22 can be minimized, and wear of both at the time of activation can be minimized.

In the Stirling engine 10 according to this embodiment, after the piston 21 is lifted from the high temperature side cylinder 22, the force to lift the piston 21 and the own weight of the piston 21 are balanced in consideration of the weight of the piston 21. The arrangement of the air supply holes 217 is not set for the purpose of doing so. As described above, the difference between the sum of the forces F ₂ that floats the piston 21 generated by the second air supply holes 217 and the sum of the forces F ₁ that floats the piston 21 generated by the first air supply holes 216 increases. Is determined as quickly as possible. Thus, the purpose of assisting the rising of the piston 21 and shortening the period until the piston 21 rises from the high temperature side cylinder 22 is as short as possible.

  The piston 21 of the Stirling engine 10 according to this embodiment takes in the air supply hole 216 while taking in the working fluid in the working space from the fluid introducing portion 214 provided on the piston top surface portion into the pressure accumulating chamber 212 while reciprocating. The air bearing 48 is formed by ejecting from the air bearing 217. In this way, the gas is not supplied from the outside, but is ejected after the working fluid is taken into the inside by its own movement, so that if a certain amount of time has not passed since the piston 21 started the movement, Insufficient working fluid is available to float 21.

  Therefore, from the viewpoint of floating the piston 21 from the high temperature side cylinder 22 as soon as possible, the above-described configuration described in this embodiment is extremely effective. In particular, when the above-described fluid element is used as the fluid introduction part 214, the pressure accumulation chamber pressure Pp is relatively difficult to increase. However, in the arrangement of the air supply holes according to this embodiment, the second air supply holes 217 in the vertical lower side LS are provided more than the first air supply holes 216 in the vertical upper side US, and after the movement of the piston 21 starts. Therefore, it is strengthened that the piston 21 floats from the high temperature side cylinder 22. As a result, after the piston 21 starts to move, it can be quickly floated.

Here, the second air supply hole 217 arranged on the lower side LS in the vertical direction has a lateral pressure of the piston 21 due to gravity when the piston 21 is arranged so that the piston central axis Z and the direction of action of gravity are orthogonal to each other. It is preferable to arrange them symmetrically with respect to the center of gravity point g with respect to the sum of (Fig. 7). Here, the lateral pressure of the piston 21 is a pressure that the piston 21 receives from the virtual plane due to gravity when the piston 21 is placed on a virtual plane orthogonal to the direction of gravity. The component is perpendicular to the virtual plane. In this way, the resultant force F ₂ that floats the piston 21 generated by the second air supply hole 217 can be matched with the barycentric point g. As a result, the inclination of the piston 21 can be suppressed and the piston 21 can be stably floated.

  Next, the structure of the piston / cylinder and the mechanism of the piston / crank portion will be described with reference to FIG. 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. For this reason, in this embodiment, in order to reduce the friction loss due to the piston ring having the largest friction loss among the internal friction of the Stirling engine to the limit, the above-described air bearing (air bearing) 48 is used without using the piston ring. Is used.

  Since the air bearing 48 has extremely small sliding resistance, the internal friction of the Stirling engine 10 can be greatly reduced. Moreover, the use of the air bearing 48 eliminates the need for lubricating oil used in the piston ring. On the other hand, since the air bearing 48 has a low ability (load ability) to withstand the force in the diameter direction (lateral direction, thrust direction) of the cylinders 22 and 32, the side force of the pistons 21 and 31 can be made substantially zero. preferable. For this reason, it is necessary to increase the linear motion accuracy of the pistons 21 and 31 with respect to the axes (center axes) of the cylinders 22 and 32. In particular, the air bearing 48 of the type that is used in this embodiment and that supports the pistons 21 and 31 by using air pressure at a minute clearance is supported compared to the type in which high-pressure air is blown. Is low. For this reason, the higher linear motion accuracy of the piston is required.

  For this reason, in this embodiment, a linear approximation mechanism is used for the piston / crank portion. FIG. 12 is a schematic configuration diagram of a piston / crank mechanism provided in the Stirling engine according to this embodiment. In this embodiment, a grasshopper mechanism (approximate linear link) 50 is employed as the linear approximation mechanism. The glass hopper mechanism 50 has an effect that the entire apparatus becomes compact because the size of the mechanism required to obtain the same linear motion accuracy is smaller than that of other linear approximation mechanisms (for example, Watt mechanism). .

  In particular, the Stirling engine 10 according to this embodiment is installed in a limited space such that the heater 47 is accommodated in the exhaust pipe of an automobile, as shown in FIG. The more compact the whole, the more freedom of installation. Further, the grasshopper mechanism 50 is advantageous in terms of fuel consumption because the mass of the mechanism necessary for obtaining the same linear motion accuracy is lighter than other mechanisms. Furthermore, since the grasshopper mechanism 50 has a relatively simple structure, it is easy to manufacture and assemble, and has an advantage that the manufacturing cost can be reduced.

  In this embodiment, since the piston / crank mechanism employs a common configuration for the high temperature side piston 21 side and the low temperature side piston 31 side, in the following description, only the high temperature side piston 21 side will be described. And the description about the low temperature side piston 31 side is abbreviate | omitted. As shown in FIGS. 1 and 12, the reciprocating motion of the piston 21 is transmitted to the crankshaft 43 through the piston pin 62, the piston-side connecting rod 61, the connecting pin 60, and the connecting rod 109. Converted. The connecting rod 109 is supported by the grasshopper mechanism 50 shown in FIG. 12, and reciprocates the piston 21 linearly. Thus, by supporting the connecting rod 109 by the grasshopper mechanism 50, the side force F of the piston 21 can be made almost zero, so that the piston 21 can be sufficiently supported even by the air bearing 48 having a small load capacity. .

(First modification)
Next, a first modification of this embodiment will be described. The piston engine according to the first modified example has substantially the same configuration as the piston engine according to the above-described embodiment, but on the lower side in the vertical direction, from the portion where the piston and the cylinder come into contact when the piston is stationary. The difference is that the air supply holes are staggered.

  FIG. 13: is sectional drawing which shows the piston with which the piston engine which concerns on a 1st modification is provided. FIG. 14 is a plan view of the piston according to the first modification viewed from the top surface side. FIG. 15 is an explanatory diagram illustrating a state in which the piston according to the first modification is viewed from the direction of arrow B in FIG. 13. FIG. 16 is an explanatory diagram illustrating a state in which the piston according to the first modification is viewed from the direction of arrow A in FIG. 13.

As shown in FIGS. 13 to 16, the piston 21A according to the first modification includes a plurality of air supply holes 216 and 217 in the side peripheral portions 211a ₁ and 211a ₂ of the piston main body 211A. Then, the second air supply hole 217 provided in the second side peripheral part 211a ₂ on the lower side LS in the vertical direction than the first air supply hole 216 provided in the first side peripheral part 211a ₁ on the upper side in the vertical direction. The number is larger. As shown in FIGS. 14 and 16, the second air supply hole 217 provided on the lower side LS in the vertical direction includes the direction of movement of the piston 21 (the direction of arrow C in FIG. 13) and the direction of action of gravity ( The piston is arranged so as to intersect the direction of arrow G), and the piston 21A is displaced from a portion (hereinafter referred to as a stationary contact portion) Sp where the piston 21A contacts the high temperature side cylinder 22 when the piston 21A is stationary. The

Comparing the curvature of the outer diameter of the piston 21A and the curvature of the inner diameter of the high temperature side cylinder 22, the latter is slightly larger. Thus, when the piston 21A is at rest, a clearance between the inner wall 22iw side of the piston 21A circumferential portion 211a ₁ and the high-temperature side cylinder 22 is increased with the progress in the vertical direction upper side. Thus, the second supply hole 217 provided in the vertically lower side LS, when arranged offset from resting contact portion Sp, enlarged portion of the air supply holes 217 in the side periphery 211a _1, 211a ₂ of the piston 21A 217s ( A slight gap generated between the opening surface of FIGS. 8 and 9 and the inner wall 22iw of the high temperature side cylinder 22 is larger than when the second air supply hole 217 is disposed in the stationary contact portion Sp.

  Therefore, if the second air supply hole 217 is arranged so as to be shifted from the stationary contact portion Sp, the orifice 217o (2) of the second air supply hole 217 is larger than the case where the second air supply hole 217 is disposed in the stationary contact portion Sp. The pressure receiving surface of the working fluid ejected from FIGS. 8 and 9) can be increased. As a result, when the piston 21A starts to reciprocate and starts to eject the working fluid from the second air supply hole 217, the difference between the downward force in the vertical direction and the upward force in the vertical direction can be further increased ( (Vertical downward force> vertical upward force). Thereby, it is possible to further shorten the time from when the piston 21B starts to move to when it floats from the high temperature side cylinder 22.

  When the second air supply hole 217 is arranged so as to be shifted from the stationary contact portion Sp, the second air supply hole is symmetric with respect to the stationary contact line Sp1 of the stationary contact portion Sp in consideration of force balance. It is preferable to arrange (FIG. 16). At this time, in the case where the piston 21A is arranged so that the piston central axis Z and the direction of action of gravity are orthogonal to each other, the second air supply hole 217 is relative to the center of gravity point g with respect to the sum of the side pressures of the piston 21A due to gravity. It is preferable to arrange them symmetrically (FIG. 16). In this way, the resultant force of the force that lifts the piston 21 </ b> A generated by the second air supply hole 217 can be matched with the barycentric point g. As a result, the inclination of the piston 21A can be suppressed and the piston 21A can be floated stably.

  Further, the first air supply hole 216 arranged on the upper side in the vertical direction is symmetrical with respect to the opposite point g2 facing the center of gravity g with respect to the piston center axis Z on the upper side in the vertical direction of the piston 21A. It is preferable to arrange. Thereby, the inclination of the piston 21A can be suppressed and the piston 21A can be stably floated.

(Second modification)
Next, a second modification of this embodiment will be described. The piston engine according to the second modified example has substantially the same configuration as the piston engine according to the first modified example, except that air supply holes are arranged at substantially equal intervals in the circumferential direction of the piston. FIG. 17 is a cross-sectional view showing a piston provided in a piston engine according to a second modification. FIG. 18 is a plan view of the piston according to the second modification viewed from the top surface side.

As shown in FIG. 18, air supply holes 216 and 217 are arranged in the side peripheral portions 211a ₁ and 211a ₂ of the piston 21B at intervals of a central angle of 120 ° with respect to the piston central axis Z. That is, the air supply holes 216 and 217 are arranged at substantially equal intervals with respect to the circumferential direction of the piston main body 211B of the piston 21B. Then, when the piston 21B is arranged so that the piston central axis Z and the direction of action of gravity (arrow G direction in FIGS. 17 and 18) are orthogonal to each other, the second air supply hole 217 is formed on the lower side LS in the vertical direction. At the same time, the first air supply hole 216 is located in the upper vertical direction US. At this time, the first and second air supply holes 216 and 217 are arranged such that the number of the second air supply holes 217 in the lower vertical direction LS is larger than that of the first air supply hole 216 in the upper vertical direction US. Is done.

  Further, the second air supply hole 217 on the lower side LS in the vertical direction is arranged so as to be shifted from the stationary contact portion Sp. As a result, the pressure receiving surface of the working fluid ejected from the orifice 217o of the second air supply hole 217 can be made larger than when the second air supply hole 217 is disposed in the stationary contact portion Sp. As a result, when the working fluid starts to be ejected from the second air supply hole 217, the difference between the upward force in the vertical direction and the downward force in the vertical direction can be increased, so that the piston 21B starts reciprocating motion. It can shorten the time until it floats. Further, since the first and second air supply holes 216 and 217 are arranged at substantially equal intervals with respect to the circumferential direction of the piston main body 211B of the piston 21B, the first and second air supply holes 216 and 217 are generated. The force is directed toward the piston center axis Z. Thus, after the piston 21B is lifted from the high temperature side cylinder 22, the clearance between both is easily maintained.

  As described above, in this embodiment and its modifications, more second air supply holes are provided on the lower side in the vertical direction than on the first air supply holes on the upper side in the vertical direction. That is, more air supply holes are provided on the lower side in the vertical direction than on the upper side in the vertical direction. For this reason, the difference between the sum of the forces that lifts the piston generated by the second air supply holes and the sum of the forces that lifts the piston generated by the first air supply holes immediately after the air starts to be ejected from the air supply holes of the piston. However, it can create a larger state. Accordingly, since the piston can be lifted from the cylinder immediately after the piston starts moving, the contact between the piston and the inner wall of the cylinder can be minimized. Thereby, both wear can be suppressed to the minimum, and both durability fall can be suppressed.

  In the above description, the Stirling engine is described as being mounted on the exhaust pipe so that the exhaust gas of the internal combustion engine of the vehicle is used as a heat source. However, the Stirling engine of the present invention is not limited to the type attached to the exhaust pipe of the internal combustion engine of the vehicle. In the above description, the configuration, operation, and effect of the piston engine are described using the case where the piston engine is a Stirling engine. However, the piston engine according to this embodiment can be easily applied to piston engines other than the Stirling engine. Applicable. And when applied, there exists an effect | action similar to the above, an effect, and it has the same usefulness as the above.

  As described above, the piston engine according to the present invention is useful for a piston engine that does not use a piston ring. In particular, the piston engine includes a hollow portion in the piston and ejects fluid from the hollow portion toward the cylinder inner surface. Suitable for

It is sectional drawing which shows the piston engine which concerns on this Example. It is explanatory drawing which shows an example of the state which collect | recovers the exhaust heat of an internal combustion engine with the piston engine which concerns on this Example. It is a front view which shows the example which has arrange | positioned the piston engine which concerns on this Example under the floor of a vehicle. It is sectional drawing which shows the piston with which the piston engine which concerns on this Example is provided. It is the top view which looked at the piston which concerns on this Example from the top surface part side. It is explanatory drawing which shows the state which looked at the piston which concerns on this Example from the arrow B direction of FIG. It is explanatory drawing which shows the state which looked at the piston which concerns on this Example from the arrow A direction of FIG. It is sectional drawing which shows the air supply hole which concerns on this Example. It is a top view which shows the air supply hole which concerns on this Example. It is sectional drawing which shows the fluid introduction part which concerns on this Example. It is a conceptual diagram which shows the state immediately after the piston engine which concerns on this Example started a motion and started ejecting a working fluid from an air supply hole. It is a schematic block diagram of the piston crank mechanism with which the Stirling engine which concerns on this Example is provided. It is sectional drawing which shows the piston with which the piston engine which concerns on a 1st modification is provided. It is the top view which looked at the piston which concerns on a 1st modification from the top surface part side. It is explanatory drawing which shows the state which looked at the piston which concerns on a 1st modification from the arrow B direction of FIG. It is explanatory drawing which shows the state which looked at the piston which concerns on a 1st modification from the arrow A direction of FIG. It is the top view which looked at the piston which concerns on a 2nd modification from the top surface part side. It is sectional drawing which shows the piston with which the piston engine which concerns on a 2nd modification is provided.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Stirling engine 20 High temperature side piston * cylinder part 21, 21A, 21B Piston 22 High temperature side cylinder 22iw Inner wall 22b Top part 30 Low temperature side piston * cylinder part 31 Piston 32 Low temperature side cylinder 43 Crankshaft 45 Cooler 46 Regenerator 47 Heater 48 air bearing 50 grasshopper mechanism 100 exhaust pipe 200up floor 200 vehicle 211,211A, 211B piston body 211t piston crown 211a _1, 211a ₂ side peripheral portion 211b top wall 211iw inner wall 211s skirt 212 accumulator (hollow portion)
214H Introduction passage 214 Fluid introduction part 216 Air supply hole (first air supply hole)
217 Air supply hole (second air supply hole)
220 Internal combustion engine

Claims (6)

A piston that reciprocates in the cylinder and whose direction of motion intersects the vertical direction;
A hollow portion formed inside the piston;
A fluid introduction part for communicating the hollow part with the inside of the cylinder, and introducing the working fluid in the cylinder into the hollow part by movement of the piston;
More than the side peripheral part of the piston on the upper side in the vertical direction, the working fluid introduced into the hollow part is provided on the side peripheral part of the piston on the lower side in the vertical direction. A plurality of air supply holes ejected in between,
A piston engine comprising: The air supply hole provided in the side periphery of the piston on the lower side in the vertical direction is
When the piston is arranged so that the direction of motion of the piston and the direction of action of gravity are orthogonal to each other, the piston is arranged symmetrically with respect to the center of gravity with respect to the sum of the side pressures of the piston due to gravity. The piston engine according to 1. The air supply hole provided in the side periphery of the piston on the upper side in the vertical direction is
3. The piston engine according to claim 1, wherein the piston engine is arranged symmetrically with respect to an opposing point facing the center of gravity with respect to a central axis of the piston. The air supply hole provided in the side periphery of the piston on the lower side in the vertical direction is
The piston is arranged such that the direction of motion of the piston and the direction of action of gravity intersect, and when the piston is stationary, the piston and the cylinder are arranged so as to be shifted from the contact portion. The piston engine according to any one of claims 1 to 3. The air supply holes are
The piston engine according to any one of claims 1 to 4, wherein the piston engine is arranged at substantially equal intervals with respect to a circumferential direction of the piston. The fluid introduction part is
The fluid element has a larger flow path resistance when the working fluid flows out from the hollow part than the flow path resistance when the working fluid flows into the hollow part, and has no movable part. The piston engine according to any one of claims 1 to 5, wherein:

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