Patent Application
20130167713
The present invention relates to a shoe for swash plate type compressor in which occurrence of seizure between a swash plate and a piston can be prevented.
As shown in
By reciprocating the piston 7 of the swash plate type compressor in the rotational shaft direction (direction indicated by the arrow M in
Since the swash plate 5 is slid while applying a large pressure to the shoe 90, a large frictional force is generated between the swash plate 5 and the shoe 90, so that seizure may possibly occur between the swash plate 5 and the shoe 90.
Even when a lubrication oil is supplied to the space between the shoe 90 and the piston 7, there is a possibility that the seizure might occur between the shoe 90 and the semispherical slide surface 13 of the piston 7, because of a frictional force generated between the shoe 90 and the semispherical slide surface 13 of the piston 7.
In order to cope with this problem, there have been known a shoe whose spherical surface is provided with a helical groove and a shoe whose spherical surface has a somewhat flattened top, in order to prevent occurrence of seizure between the shoe and a semispherical slide surface (see, for example, Patent Documents 1 and 2). In addition, there has been known a shoe whose flat surface has a circular recess or an annular groove formed in a center part thereof, in order to prevent occurrence of seizure between a swash plate and the shoe (see, for example, Patent Documents 3 and 4).
However, in the shoe used in the aforementioned conventional swash plate type compressor, since an oil lubrication effect is local, an amount of the lubrication oil between the swash plate and the shoe and/or between the shoe and the piston is insufficient, whereby there is a possibility that the oil lubrication effect is lost. Thus, the seizure may occur between the swash plate and the shoe and/or the seizure may occur between the shoe and the piston.
In addition, since such a shoe itself has a large weight, a large load is imposed on the piston and the swash plate, which is likely to cause abrasion. Thus, in order to reduce the weight of the shoe, there has been known a hollow shoe provided with a flat surface having a substantially constant thickness, and a spherical surface having a thickness that is gradually decreased toward a top (see Patent Document 5).
However, as shown in Patent Document 5, when the hollow shape is changed in order to make constant the thickness, the strength of the shoe lessens. Such a small-sized shoe is insufficient in durability and it is difficult to practically use the shoe. In addition, since the degree of the reduced weight is about 10% at the most, the effect of weight reduction is not yet sufficient.
The present invention has been made in view of the above circumstances. The object of the present invention is to provide a shoe for swash plate type compressor, the shoe being capable of preventing the seizure (burn) between the a flat surface of the shoe and a swash plate and the seizure between a spherical surface of the shoe and a piston. The shoe can be downsized, while maintaining an excellent durability.
A shoe for a swash plate type compressor according to the present invention is a shoe for swash plate type compressor, disposed between a swash plate provided on a rotational shaft in an inclined manner, the swash plate being configured to be rotated together with the rotational shaft, and a piston configured to be reciprocated in a direction in which the rotational shaft extends, by means of the rotation of the swash plate, the shoe for swash plate type compressor comprising:
a flat surface in contact with the swash plate; and
a spherical surface in contact with a semispherical slide surface formed on the piston;
wherein:
a through-hole communicating the flat surface and the spherical surface with each other is formed between the flat surface and the spherical surface; and
the through-hole is composed of a first through-hole of a cylindrical shape having a first radius and a second through-hole of a cylindrical shape having a second radius that is larger than the first radius.
In the shoe for a swash plate type compressor according to the present invention, the first through-hole may be formed on a side of the spherical surface so as to extend up to the spherical surface, and the second through-hole may be formed on a side of the flat surface so as to extend up to the flat surface.
The shoe for a swash plate type compressor according to the present invention may further comprises a transitional hole of a truncated conical shape formed between the first through-hole and the second through-hole, the transitional hole communicating the first through-hole and the second through-hole with each other.
In the shoe for a swash plate type compressor according to the present invention, an inner circumferential part of the flat surface adjacent to the through-hole may be inclined toward the spherical surface, and an inner circumferential part of the spherical surface adjacent to the through-hole may be inclined toward the flat surface.
In the shoe for a swash plate type compressor according to the present invention, the spherical surface may have a contact surface in contact with the slide surface of the piston under a static state, and a non-contact surface not in contact with the slide surface under the static state.
In the shoe for a swash plate type compressor according to the present invention, the flat surface may have a contact surface in contact with the swash plate under the static state, and an area of the contact surface of the spherical surface and an area of the contact surface of the flat surface may be substantially equal to each other.
According to the present invention, there is provided the cylindrical through-hole communicating the flat surface and the spherical surface with each other. The through-hole is composed of the cylindrical first through-hole having the first diameter, and the cylindrical through-hole having the second diameter larger than the first diameter. Thus, oil can be supplied to the flat surface and the spherical surface of the shoe, whereby the seizure (burn) between the flat surface of the shoe and the swash plate and the seizure between the spherical surface of the shoe and the piston can be prevented. In addition, the shoe can be downsized, while maintaining an excellent durability.
a)(b) are sectional views showing an operation of a swash plate type compressor according to an embodiment of the present invention.
An embodiment of a swash plate type compressor and a shoe for swash plate type compressor according to the present invention will be described herebelow, with reference to the drawings.
As shown in
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In this embodiment, the transitional hole 38 is formed between the first through-hole 36 and the second through-hole 37, which is by way of example, and the present invention is not limited thereto. As shown in
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In this embodiment, the contact surface 31a of the spherical surface 31 is located on a virtual spherical surface. A radius R1 of the virtual spherical surface is about 9.00 mm. The non-contact surface 31b has a surface which is substantially in parallel with the virtual spherical surface on which the contact surface 31a is located, and is recessed from the virtual spherical surface.
As shown in
Herein, it is preferable that an area of the contact surface 31a of the spherical surface 31 and an area of the contact surface 32a of the flat surface 32 are substantially equal to each other. When the area of the contact surface 31a of the spherical surface 31 and the area of the contact surface 32a of the flat surface 32 are substantially equal to each other, a pressing force per unit area applied between the semispherical slide surface 13 and the spherical surface 31, and a pressing force per unit area applied between the flat surface 32 and the swash plate 5, can be made substantially equal to each other. Thus, the shoe 30 can be slid in a well-balanced manner.
In order to make the area of the contact surface 31a of the spherical surface 31 and the area of the contact surface 32a of the flat surface 32 be substantially equal to each other, the diameter D2 between the ending points of the contact surface 31a is adjusted and/or the diameters d1 and d2 of the through-hole 35 are adjusted.
A diameter d3 of the contact surface 32a of the flat surface 32 of the shoe 30 is about 13.00 mm, a height H of the shoe 30 is about 5.85 mm, and a diameter d4 of the shoe 30 is about 15.00 mm (see
It is preferable that the diameter d1 of the first through-hole 36 of the through-hole 35 is about 30% to about 45% of the radius R1 of the virtual spherical surface. It is preferable that the diameter d2 of the second through-hole 37 of the through-hole 35 is about 45% to about 95% of the radius R1 of the virtual spherical surface. It is preferable that a height h of the second through-hole 37 is about 20% to about 30% of the radius R1 of the virtual spherical surface. To be more specific, the diameter d1 of the first through-hole 36 is, e.g., 4.0 mm, the diameter d2 of the second through-hole 37 is e.g., 7.0 mm, and the height h of the second through-hole 37 is, e.g., 2.5 mm. Due to these dimensions, the weight of the shoe 30 can be reduced by 30%, as compared with the conventional shoe 30 not having the through-hole 35.
Although the dimensions of the shoe 30 are described, the above numerical values are mere examples and the present invention is not limited thereto.
Next, an operation of this embodiment as structured above will be described.
At first, the drive unit (not shown), such as a motor, connected to the rotational shaft 2 drives the rotational shaft 2 in rotation (in the direction indicated by the arrow C in
Due to the rotation of the swash plate 5, the piston 7 is linearly moved in one direction of the rotational shaft direction (in the direction indicated by the arrow M1 in
During the linear movement of the piston 7 in the one rotational shaft direction, when a pressure of a frozen refrigerant compressed between the piston 7 and the second valve plate 8b becomes greater than a pressure of a frozen refrigerant in the discharge pipe (not shown) connected to the second valve plate 8b, the frozen refrigerant in the compression chamber 6 is discharged to the discharge pipe through the second discharge valve 21b (see
Then, the drive unit connected to the rotational shaft 2 further drives the rotational shaft 2 in rotation (in a direction indicated by the arrow C in
Since the swash plate 5 is further rotated, the piston 7 is linearly moved in the other rotational shaft direction, i.e., in a direction opposed to the above direction (in a direction indicated by the arrow M2 of
During the linear movement of the piston 7 in the other rotational shaft direction, when a pressure of a frozen refrigerant compressed between the piston 7 and the first valve plate 8a becomes greater than a pressure of a frozen refrigerant in the discharge pipe connected to the first valve plate 8a, the frozen refrigerant in the compression chamber 6 is discharged to the discharge pipe through the first discharge valve 21a (see
Thereafter, the above steps are repeatedly carried out. As described above, since the rotational shaft 2 is rotated by the drive unit so that the swash plate 5 is rotated, the piston 7 can be reciprocated. Thus, the swash plate type compressor can compress a frozen refrigerant in the compression chamber 6 and discharge the compressed frozen refrigerant, as well as suck a frozen refrigerant from the suction pipe into the compression chamber 6.
While the piston 7 is being reciprocated, the lubrication oil passes through the cylindrical through-hole 35 communicating the flat surface 32 and the spherical surface 31 with each other, whereby the lubrication oil can be supplied to both of the flat surface 32 and the spherical surface 31 thoroughly (see
In particular, when the operation of a general swash plate type compressor is started, since a frozen refrigerant flows at first, the inside of the swash plate type compressor is degreased so that no oil lubrication effect can be provided. Thus, the seizure between the shoe 30 and the swash plate 5 is likely to occur. On the other hand, according to this embodiment, owing to the provision of the through-hole 35, an oil, which was used before, remains in the through-hole 35. Namely, since the oil can be held in the through-hole 35, the seizure between the shoe 30 and the swash plate 5 can be securely prevented.
In addition, according to this embodiment, since the transitional hole 38 of a truncated conical shape is provided between the first through-hole 36 and the second through-hole 37, an oil can be easily stored. Thus, the seizure between the shoe 30 and the swash plate 5 can be more securely prevented.
In addition, according to this embodiment, since the cylindrical through-hole 37 having the second diameter d2, which is relatively a larger diameter, is provided, a larger amount of remaining oil can be held. Thus, the seizure between the shoe 30 and the swash plate 5 can be more securely prevented.
In addition, as shown in
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In addition, as described above, when the area of the contact surface 31a of the spherical surface 31 and the area of the contact surface 32a of the flat surface 32 are substantially equal to each other, a pressing force per unit area applied between the semispherical slide surface 13 and the spherical surface 31, and a pressing force per unit area applied between the flat surface 32 and the swash plate 5, can be made substantially equal to each other. Thus, the shoe 30 can be slid in a well-balanced manner.
Next, a result of a friction and abrasion test (pin-on-disk friction and abrasion test) between the shoe 30 and the swash plate 5 is described.
A test apparatus shown in
Disposed between the swash plate fixing part 64 and the pressurizing shaft 62 is a steel ball 63 serving as a pivot shaft. In addition, a protective barrel 65 for safety is disposed outward peripheries of the shoe pressers 68 and the swash plate fixing part 64.
An electric motor (not shown) for rotating the rotational shaft 61 is connected to the rotational shaft 61. The electric motor stops, when a rotational torque value exceeds a set value. Connected to the pressurizing shaft 62 is a pressurizing apparatus (not shown), such as an oil pressure generator, for loading and pressurizing the pressurizing shaft 62. A force in a torsional direction applied to the pressurizing shaft 62 is detected as a rotational torque value.
A frictional force was generated between the shoe 30 and the swash plate 5, by rotating the shoe 30 at a predetermined rotational speed, while pressing the slide surface 13 of the swash plate 5 onto the flat surface 32 of the shoe 30 by pressurizing the swash plate 5 in the upward direction in
Amounts of forces corresponding to the above frictional forces were detected as rotational torque values. The below-described Table 1 shows these values. The rotational torque value corresponds to the performance of the shoe 30 with respect to the swash plate 5. When the rotational torque value is small, the seizure rarely occurs, i.e., the performance of the shoe 30 is excellent.
As a comparative example, there was used the conventional shoe 30 not having the through-hole 35.
As understood from the above Table 1, there is not so remarkable difference between the comparative example shoe and the example shoe, in the regions of 50 kgf and 100 kgf as low loads. On the other hand, in the regions of 150 kgf and 200 kgf as high loads, the rotational torque values of the example shoe 30 are less than the rotational torque values of the comparative example shoe. Thus, it can be understood that the example shoe is excellent against friction and abrasion. In particular, after 300 seconds had passed with a load of 200 kgf being applied, the rotational torque value of the comparative example shoe was 2.5, while the rotational torque value of the example shoe was 0.65. Namely, the rotational torque value of the comparative example shoe is 3.8 times (=2.5/0.65) the rotational torque value of the example shoe. Thus, it can be understood that the example shoe 30 can be expected to provide a seizure prevention effect which is about four times a seizure prevention effect provided by the comparative example shoe.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-204662 | Sep 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/070176 | 9/5/2011 | WO | 00 | 3/19/2012 |
