RECIPROCATING ENGINE TECHNICAL FIELD

The present invention relates to improvement in a reciprocating 1 -cycle engine having a piston mechanism which is moved by compressed gas and wherein one reciprocating movement of the piston is set as one cycle. BACKGROUND ART

In the related art, there is known an engine which has a piston mechanism having a cylinder and a piston housed in the cylinder to separate the cylinder into two spaces. In such an engine, the piston mechanism is moved by compressed gas alternately introduced to the two spaces of the piston, and pressure energy of the compressed gas is converted into kinetic energy, which can be output.

Patent Literature 1 discloses a pressure engine in which a piston is moved in a reciprocating manner with compressed air introduced to the cylinder, to rotate a crankshaft.

In this pressure engine, the cylinder is separated into two cylinder chambers by the piston.

To each of these two cylinder chambers, there are connected an air inlet port through which compressed air is supplied and an air exhaust port through which the supplied compressed air is discharged as remnant air, and open/close devices are provided on these four ports.

The open/close devices are opened and closed according to the stroke of the piston.

[Citation List] Patent Literature 1 : JP 2001-132403 A SUMMARY

[Technical Problem]

In the engine described in the Patent Literature 1, the air inlet port and the air exhaust port are connected to each of the two cylinder chambers, and open/close devices are provided on all of the four ports. In such a structure, the number of components is increased, and the structure becomes complicated. Therefore, there have been problems of an increased number of occurrences of failure, increased size and weight of the device, and increased manufacturing cost.

An advantage of the present invention lies in provision of a reciprocating 1 -cycle engine which allows, in an engine having two cylinder chambers, simplification of a structure related to selective introduction of compressed gas to the two cylinder chambers and selective discharge of remnant gas from the two cylinder chambers.

[Solution to problem]

According to one aspect of the present invention, there is provided a reciprocating

1 -cycle engine comprising a cylinder, and a piston which is housed in the cylinder, to separate the cylinder into a first cylinder chamber and a second cylinder chamber, and which moves in a reciprocating manner, wherein one reciprocating movement of the piston including a first stroke in which compressed gas is introduced into the first cylinder chamber and remnant gas in the second cylinder chamber is discharged and a second stroke in which remnant gas in the first cylinder chamber is discharged and the compressed gas is introduced into the second cylinder chamber is set as one cycle of the engine, the reciprocating 1 -cycle engine further comprising an introduction path through which the compressed gas is introduced into each of the first cylinder chamber and the second cylinder chamber, an exhaust path through which the remnant gas in each of the first cylinder chamber and the second cylinder chamber is discharged, and a switching valve which is provided between the first and second cylinder chambers and the introduction and exhaust paths and which switches a connection relationship between the first and second cylinder chambers and the introduction and exhaust paths based on the first stroke and the second stroke.

According to another aspect of the present invention, preferably, in the reciprocating 1 -cycle engine, in the first stroke the switching valve connects the first cylinder chamber and the introduction path and connects the second cylinder chamber and the exhaust path for a predetermined period, and in the second stroke the switching valve connects the first cylinder chamber and the exhaust path and connects the second cylinder chamber and the introduction path for a predetermined period.

According to another aspect of the present invention, preferably, in the reciprocating 1 -cycle engine, the switching valve comprises a valve box having a first cylinder chamber port in communication with the first cylinder chamber, a second cylinder chamber port in communication with the second cylinder chamber, an introduction port in communication with the introduction path, and an exhaust port in communication with the exhaust path, a valve element which is housed in the valve box and which opens and closes between the first and second cylinder chamber ports and the introduction and exhaust ports, and a valve element moving member which moves the valve element to two positions based on the first stroke and the second stroke, the first cylinder chamber port and the introduction port are opened to each other and the second cylinder chamber port and the exhaust port are opened to each other when the valve element is at a first position, and the first cylinder chamber port and the exhaust port are opened to each other and the second cylinder chamber port and the introduction port are opened to each other when the valve element is at a second position.

According to another aspect of the present invention, preferably, in the reciprocating 1 -cycle engine, the valve box has a valve base which is a surface in which the first cylinder chamber port, the exhaust port, and the second cylinder chamber port are formed and arranged in this order, the valve element moving member moves the valve element in a reciprocating manner while the valve element contacts the valve base such that the position of the valve element is set in the order of the second position and the first portion along the direction of arrangement of the first cylinder chamber port, the exhaust port, and the second cylinder chamber port in this order, and the introduction port is positioned at a location which enables pressurizing the valve element moving in the reciprocating manner against the valve base by a pressure of the compressed gas supplied from the introduction path. According to another aspect of the present invention, preferably, in the reciprocating 1 -cycle engine, the valve element has a recess formed at a center of a surface opposing the valve base, the first cylinder chamber port is opened and connected to the introduction port and the second cylinder chamber port and the exhaust port are connected to each other through the recess when the valve element is at the first position, and the first cylinder chamber port and the exhaust port are connected to each other through the recess and the second cylinder chamber port is opened and connected to the introduction port when the valve element is at the second position.

According to another aspect of the present invention, preferably, the reciprocating 1 -cycle engine further comprises a crankshaft which is connected to the piston, wherein the valve element moving member converts a rotational movement of the crankshaft into a reciprocating movement and moves the valve element.

According to another aspect of the present invention, preferably, in the reciprocating 1 -cycle engine, a crankshaft chamber which houses a crankshaft is provided adjacent to the second cylinder chamber, and a sealing member for maintaining gas-tightness of the second cylinder chamber is provided on a hole formed in a wall separating the second cylinder chamber and the crankshaft chamber and through which a connecting rod which connects the cylinder and the crankshaft passes.

[Advantageous Effects of Invention]

According to the reciprocating 1 -cycle engine of various aspects of the present invention, in an engine having two cylinder chambers, a structure related to selective introduction of compressed gas to the two cylinder chambers and selective discharge of the remnant gas from the two cylinder chambers can be simplified.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a structure of a reciprocating 1 -cycle engine according to a preferred embodiment of the present invention.

FIG. 2 is a diagram showing a state of an engine in a first stroke. FIG. 3 is a diagram showing a state of the engine in a second stroke.

FIG. 4 is a diagram showing a relationship between a rotational angle of the crankshaft and an operation timing of a switching valve. DESCRIPTION OF EMBODIMENT

A reciprocating 1 -cycle engine according to a preferred embodiment of the present invention will now be described with reference to the drawings. The engine can be applied to a prime motor equipped in a moving body such as a vehicle or to a prime motor which is used for other purposes. In the reciprocating 1 -cycle engine of the present embodiment, compressed air is used as the compressed gas. However, the present invention is not limited to such a configuration, and, for example, water vapor or other gas may be used as the compressed gas, so long as the gas has a pressure higher than the atmospheric pressure.

FIG. 1 is a diagram showing a structure of a reciprocating 1 -cycle engine 10 of the present embodiment. The reciprocating 1 -cycle engine 10 comprises a cylinder 12 and a piston 18 which is housed in the cylinder 12 to separate the cylinder 12 into two cylinder chambers; that is, a first cylinder chamber 14 and a second cylinder chamber 16.

The reciprocating 1 -cycle engine 10 is an engine having one reciprocating movement of the piston 18 as one cycle, and is a device which includes a piston mechanism which converts compressed air into kinetic energy and outputs the kinetic energy. One reciprocating movement of the piston 18 refers to a movement of two strokes including a first stroke in which the compressed air is introduced into the first cylinder chamber 14 and remnant air in the second cylinder chamber 16 is discharged, and a second stroke in which the remnant air in the first cylinder chamber 14 is discharged and the compressed air is introduced into the second cylinder chamber 16. The remnant air refers to the compressed air which is introduced into each of the cylinder chambers 14 and 16 and then has its pressure reduced due to expansion of each of the cylinder chambers 14 and 16. The reciprocating 1 -cycle engine (hereinafter simply referred to as "engine") 10 comprises the cylinder 12, the piston 18 which is housed in the cylinder and moves in a reciprocating manner, and a crankshaft 24 which is connected to the piston 18 via a connecting rod 20 and a con-rod 22, and which converts the reciprocating movement of the piston 18 into a rotational movement. The crankshaft 24 is provided with a rotational angle sensor (not shown) which detects a rotational angle of the crankshaft 24.

The piston 18 is positioned to separate the cylinder 12 into the first and second cylinder chambers 14 and 16. In the present embodiment, the first cylinder chamber 14 is formed on an upper dead center point side (upper side on the page) and the second cylinder chamber 16 is formed on the lower dead center point side (lower side of the page); that is, on the side of the crankshaft 24.

A crankshaft chamber 26 which houses the crankshaft 24 is provided adjacent to the second cylinder chamber 16. In a wall 28 separating the second cylinder chamber 16 and the crankshaft chamber 26, there is formed a through-hole 30 through which the connecting rod 20 passes. On the through-hole 30, there is provided a seal member 32 which maintains the gas-tightness of the second cylinder chamber 16 such as, for example, an O-ring. With the gastight structure, it is possible to prevent intrusion of the compressed air from the second cylinder chamber 16 into the crankshaft chamber 26. In addition, even when the compressed gas used in the engine 10 is water vapor, intrusion of the water vapor can be prevented. Therefore, it is possible to prevent accumulation of the water vapor in the lubricant oil housed in the crankshaft chamber 26, and to prevent subsequent reduction of the lubrication performance.

The engine 10 also comprises an introduction path 34 through which the compressed air is introduced into the cylinder chambers 14 and 16 and an exhaust path 36 through which the remnant air in the cylinder chambers 14 and 16 is discharged. The compressed air is produced by a compressed gas generating source, such as a compressor (not shown), and is supplied from the compressor through the introduction path 34 into the cylinder chambers 14 and 16. The engine 10 of the present embodiment further comprises a switching valve 38 provided between the cylinder chambers 14 and 16 and the introduction and exhaust paths 34 and 36. The switching valve 38 switches the connection relationship between the cylinder chambers 14 and 16 and the introduction and exhaust paths 34 and 36 based on the first and second strokes. More specifically, the switching valve 38 selectively switches the introduction of the compressed gas to the cylinder chambers 14 and 16 and selectively switches the discharge of the remnant gas from the cylinder chambers 14 and 16. With this structure, the number of open/close devices corresponding to the cylinder chambers 14 and 16 can be reduced from four in the related art to one, and, therefore, the structure of the engine 10 can be simplified. As a result, it is possible to reduce the occurrences of failure, reduce size and weight of the device, and reduce the manufacturing cost. The structure of the switching valve 38 will now be described.

The switching valve 38 comprises a valve box 40, a valve element 42 housed in the valve box 40, and a valve element moving member 44 which is connected to the valve element 42 and moves the valve element 42.

The valve box 40 comprises a first cylinder chamber port 46 in communication with the first cylinder chamber 14, a second cylinder chamber port 48 in communication with the second cylinder chamber 16, an introduction port 50 in communication with the introduction path 34, and an exhaust port 52 in communication with the exhaust path 36. In this manner, by reducing the number of paths connected to the cylinder chambers 14 and 16 from four in the related art to two (first and second cylinder chamber ports 46 and 48), the structure of the engine 10 can be simplified.

The valve box 40 also comprises a valve base 54 corresponding to the valve element 42. The switching valve 38 of the present embodiment is a valve device which switches the connection relationship by sliding the valve element 42 in one direction. Therefore, on the valve base 54, the first cylinder chamber port 46, the exhaust port 52, and the second cylinder chamber port 48 are positioned arranged in one line. More specifically, the first cylinder chamber port 46, the exhaust port 52, and the second cylinder chamber port 48 are positioned in this order from an upper dead center point toward the lower dead center point side in the direction of the reciprocating movement of the piston 18. Meanwhile, the introduction port 50 is positioned at a location which enables pressurization of the valve element 42 against the valve base 54 by a pressure of the compressed air supplied from the introduction path 34. More specifically, as shown in FIG. 1, the introduction port 50 is positioned on a surface different from a surface including the valve base 54.

With this structure, even if no sealing member is provided on the contact surface between the valve element 42 and the valve base 54, it is possible to secure gas-tightness between the valve element 42 and the valve base 54 while taking advantage of the pressure of the compressed air. In the present embodiment, there is described a configuration in which the introduction port 50 is positioned on a surface different from the surface including the valve base 54, but the present invention is not limited to such a configuration. Alternatively, the introduction port 50 may be positioned on the surface including the valve base 54, so long as the introduction port 50 is not blocked by the valve element 42.

The valve element 42 is a member which opens and closes between the cylinder chamber ports 46 and 48 and the introduction and exhaust ports 50 and 52. The valve element 42 has a recess 56 formed at a center of a surface opposing the valve base 54. As will be described below, the recess 56 has a function to connect the cylinder chamber ports 46 and 48 and the exhaust port 56 positioned on the valve base 54. A position of the valve element 42 shown in FIG. 1 is a position of closed-valve state (a third position to be described below). In this position, the surface of the valve element 42 opposing the valve base 54 blocks the first and second cylinder chamber ports 46 and 48, and the recess 56 covers the exhaust port 52. In other words, this is a closed-valve state in which none of the four ports is connected to any other port.

The valve element moving member 44 comprises a cam 60 and a spring 62 which is connected to the valve element 42 via a valve shaft 58 and moves the valve element 42. In the valve box 40, a hole through which the valve shaft 58 passes is formed in parallel to the direction of the reciprocating movement of the piston 18, and a valve shaft sealing member 63 for maintaining the gas-tightness of the valve box 40 such as, for example, an O-ring, is provided on the hole. With this gastight structure, it is possible to prevent leakage of the compressed air through a gap between the valve box 40 and the valve shaft 58. The cam 60 is provided in a manner to rotate in synchronization with a cam shaft 64. The cam shaft 64 is connected to the crankshaft 24 via a motive force transmitting mechanism (not shown) such as a timing belt or a gear. As the cycle of the engine 10 is two-strokes in one cycle, the motive force transmitting mechanism is configured such that the cam shaft 64 rotates one revolution as the crankshaft 24 rotates one revolution. Within the one cycle; that is, within the first and second strokes, the valve element moving member 44 can convert the rotational movement of the crankshaft 24 into the reciprocating movement and move the valve element 42. In other words, the valve element moving member 44 can move the valve element 42 to reciprocate between two positions. Of the two positions of the valve element 42, the position at the lower dead center point side in the direction of the reciprocating movement of the piston 18 will hereinafter be called a first position. On the other hand, of the two positions of the valve element 42, the position at the upper dead center point side in the direction of the reciprocating movement of the piston 18 will hereinafter be called a second position. Positions between the first and second positions, where the valve element is in the closed-valve state as shown in FIG. 1, will hereinafter be called a third position. When the valve element 42 is at the third position, the valve box 40 is filled with the compressed air introduced from the introduction port 50.

An operation of the engine 10 having such a structure and an operation of the switching valve 38 in the operation of the engine 10 will now be described with reference to FIGs. 2 - 4. FIG. 2 is a diagram showing a state of the engine 10 in the first stroke, FIG. 3 is a diagram showing a state of the engine 10 in the second stroke, and FIG. 4 is a diagram showing a relationship between the rotational angle of the crankshaft 24 and an operation timing of the switching valve 38. In these figures, there is described an example configuration in which the cycle is in the clockwise direction in the figures.

FIG. 4 shows that the piston 18 is at the upper dead center point when the rotational angle of the crankshaft 24 is 0 degrees and that the piston 18 is at the lower dead center point when the rotational angle is 180 degrees. Because the cycle is in the clockwise direction as described above, in FIG. 4, the cycle is in the first stroke when the rotational angle of the crankshaft 24 is between 0 and 180 degrees, and the cycle is in the second stroke when the rotational angle is between 180 and 360 degrees.

The state of the engine 10 in the first stroke will first be described. In the first stroke, the switching valve 38 connects the first cylinder chamber 14 and the introduction path 34 and connects the second cylinder chamber 16 and the exhaust path 36 for a predetermined period of time. In this period, the valve element 42 is moved in a direction of an arrow 70 and is at the first position as shown in FIG. 2. The first cylinder chamber port 46 and the introduction port 50 are opened to each other and the second cylinder chamber port 48 and the exhaust port 52 are opened to each other. More specifically, with the movement of the valve element 42 from the state shown in FIG. 1 in the direction of the arrow 70, the first cylinder chamber port 46 which has been blocked by the valve element 42 is opened and connected to the introduction port 50. In addition, with the movement of the valve element 42 in the direction of the arrow 70, the second cylinder chamber port 48 which has been blocked by the valve element 42 is connected to the exhaust port 52 through the recess 56.

With the connection of the first cylinder chamber port 46 and the introduction port 50, the compressed air is introduced from the introduction path 34 into the first cylinder chamber 14. Because of the pressure of the compressed air introduced into the first cylinder chamber 14, the piston 18 is pressed toward the direction of the arrow 70 and is lowered. Meanwhile, because of this movement of the piston 18 and the connection of the second cylinder chamber port 48 and the exhaust port 52, the remnant air is discharged from the second cylinder chamber 16 to the exhaust path 36. With such a linear movement of the piston 18, the crankshaft 24 is rotated in the clockwise direction. As shown in FIG. 4, this state in the first stroke where the valve element 42 is at the first position is preferably between the rotational angle of the crankshaft 24 of 5 and 175 degrees. By setting the valve element 42 to the first position at such a timing, a larger amount of compressed air to be introduced can be secured, and the output power can be increased. In addition, by setting the valve element 42 to the first position at such a timing, it is possible to reliably secure an amount of remnant air to be discharged, and to reduce the resistance to the movement of the piston 18, and, as a result, the operation efficiency can be improved.

Next, a state of the engine 10 in the second stroke will be described. In the second stroke, the switching valve 38 connects the first cylinder chamber 14 and the exhaust path 36 and connects the second cylinder chamber 16 and the introduction path 34 for a predetermined period of time. In this period, the valve element 42 is moved in a direction of an arrow 72 and is at the second position shown in FIG. 3, the first cylinder chamber port 46 and the exhaust port 52 are opened to each other, and the second cylinder chamber port 48 and the introduction port 50 are opened to each other. More specifically, with the movement of the valve element 42 from the state shown in FIG. 1 in the direction of the arrow 72, the first cylinder chamber port 46 which has been blocked by the valve element 42 is connected to the exhaust port 52 through the recess 56. Meanwhile, with the movement of the valve element 42 in the direction of the arrow 72, the second cylinder chamber port 48 which has been blocked by the valve element 42 is opened and connected to the introduction port 50.

With the connection of the second cylinder chamber port 48 and the introduction port 50, the compressed air is introduced from the introduction path 34 into the second cylinder chamber 16. Because of the pressure of the compressed air introduced into the second cylinder chamber 16, the piston 18 is pressed toward the direction of the arrow 72 and is raised. Meanwhile, because of this movement of the piston 18 and the connection between the first cylinder chamber port 46 and the exhaust port 52, the remnant air is discharged from the first cylinder chamber 14 to the exhaust path 36. With such a linear movement of the piston 18, the crankshaft 24 is rotated in the clockwise direction.

As shown in FIG. 4, the state in the second stroke where the valve element 42 is at the second position is preferably between the rotational angle of the crankshaft 24 of 185 to 355 degrees. By setting the valve element 42 to the second position at such a timing, it is possible to secure a larger amount of compressed air to be introduced and to increase the output power. In addition, by setting the valve element 42 to the second position at such a timing, it is possible to reliably secure an amount of remnant air to be discharged and to reduce the resistance to the movement of the piston 18, and, as a result, the operation efficiency can be improved.

According to the present embodiment, by setting the number of paths to the cylinder chambers 14 and 16 to one for each chamber and setting the number of mechanisms for switching the connection between the cylinder chambers 14 and 16 and the introduction and exhaust paths 34 and 36 to one, the structure of the engine 10 can be simplified. As a result, as described above, the number of failures can be reduced, the size and weight of the device can be reduced, and the manufacturing cost can be reduced.

In the present embodiment, there is described a configuration in which the valve element 42 is at the first position between the rotational angle of the crankshaft 24 of 5 and 175 degrees, and the valve element 42 is at the second position between the rotational angle of the crankshaft 24 of 185 and 355 degrees, but the present invention is not limited to such a configuration. In the first and second strokes, the piston 18 is driven by the pressure of the compressed air, and, thus, the periods of the first and second positions may be elongated, to introduce a larger amount of compressed air into the cylinder chambers 14 and 16. With this configuration, a larger amount of remnant air which forms the movement resistance to the piston 18 can be discharged from the cylinder chambers 14 and 16.

In addition, in the present embodiment, there is described a configuration in which the switching valve 38 is a valve device which switches the connection relationship by sliding the valve element 42 in one direction, but the present invention is not limited to such a configuration. Alternatively, the switching valve 38 may be a valve device which switches the connection of four ports by rotating the valve element 42 about the valve shaft 58; that is, the switching valve 38 may be a four- way valve.