Abstract:
A compressor including a motor, a piston reciprocating by the motor, a crankcase having a middle wall portion formed with a communication hole, the crankcase housing the piston, a cylinder body secured to an inner surface of the middle wall portion, the cylinder body and the wall portion defining a cylinder chamber, and reciprocation of the piston increasing or decreasing a capacity of the cylinder chamber, and a cylinder head secured to an outer surface of the middle wall portion, the cylinder head and the middle wall portion defining an exhaust chamber communicated with the cylinder chamber through the communication hole.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2012-138931, filed on Jun. 20, 2012, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     (i) Technical Field 
     The present invention relates to a compressor and a vacuum machine. 
     (ii) Related Art 
     There is known a compressor and a vacuum machine where a piston reciprocates within a cylinder by a motor. Japanese Patent Application Publication No. 2004-183498 discloses such a compressor. As for general compressor and vacuum machine, a cylinder body and a cylinder head are provided outside a crankcase. 
     In order to provide the cylinder body and the cylinder head outside the crankcase, the cylinder body is secured to a wall portion of the crankcase, and the cylinder head is secured to the cylinder body. In this case, a seating portion on which the piston is seated has to be provided separately from the wall portion of the crankcase. Therefore, the whole size of the device may increase in such a direction that the piston moves. Also, an exclusive part functioning as the seating portion is needed, so that the number of the parts increases. 
     On the other hand, in order to downsize the compressor and the vacuum machine, the cylinder or the crankcase is reduced in size. However, if the cylinder is reduced in size, absorption or discharging ability of the compressor and the vacuum machine might deteriorate. Also, if the crankcase is reduced in size, the cylinders interfere with each other. Thus, there is a limit in reducing the crankcase in size. 
     SUMMARY 
     According to an aspect of the present invention, there is provided a compressor including: a motor; a piston reciprocating by the motor; a crankcase comprising a wall portion formed with a communication hole, and the crankcase housing the piston; a cylinder body secured to an inner surface of the wall portion, the cylinder body and the wall portion defining a chamber, and reciprocation of the piston increasing or decreasing a capacity of the chamber; and a cylinder head secured to an outer surface of the wall portion, and the cylinder head and the wall portion defining space communicated with the chamber through the communication hole. 
     According to another aspect of the present invention, there is provided a vacuum machine including: a motor; a piston reciprocating by the motor; a crankcase comprising a wall portion formed with a communication hole, and the crankcase housing the piston; a cylinder body secured to an inner surface of the wall portion, the cylinder body and the wall portion defining a chamber, and reciprocation of the piston increasing or decreasing a capacity of the chamber; and a cylinder head secured to an outer surface of the wall portion, and the cylinder head and the wall portion defining space communicated with the chamber through the communication hole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an external view of a compressor according to a first embodiment; 
         FIG. 2  is an external view of the compressor according to the first embodiment; 
         FIG. 3  is a sectional view taken along A-A line of  FIG. 1 ; and 
         FIG. 4  is a sectional view of a part of a compressor different from the present embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     [First Embodiment] 
       FIGS. 1 and 2  are external views of a compressor A according to a first embodiment. The compressor A includes: a crankcase  20 ; four cylinders  10   a  to  10   d  provided with the crankcase  20 ; and a fan F arranged at the upper side of the crankcase  20 . The Fan F is secured to a motor. The motor will be described later in detail. The cylinder  10   a  includes a cylinder head  15   a  secured to the outside of the crankcase  20 , and a cylinder body provided within the crankcase  20 . Likewise, the other cylinders  10   b  to  10   d  have the same structure. Thus, the other cylinder heads  15   b  to  15   d  are provided on wall portions of the crankcase  20 , respectively. 
     Specifically, the cylinder heads  15   a  to  15   d  are secured to the flat, outer surfaces of the middle wall portions of the crankcase  20 , respectively. As illustrated in  FIG. 1 , the cylinder heads  15   a  to  15   d  are radially arranged about the rotational shaft  42  at even intervals. Middle wall portions  21   a  and  21   b  are adjacent and perpendicular to each other, and the middle wall portions  21   c  and  21   d  are adjacent and perpendicular to each other. The middle wall portions  21   a  and  21   c  face each other in the parallel manner, and the middle wall portions  21   b  and  21   d  face each other in the parallel manner. Also, the crankcase  20  is provided with an upper wall portion  21   e  near the motor. The cylinder heads, the cylinder bodies, the crankcase  20  are made of metal such as aluminum having good heat radiation characteristics. 
     The fan F, which is secured to the motor, includes: a body portion FM having a substantially cylindrical shape; a ring portion FR formed at the outside of the body portion FM; and plural blade portions FB formed between the body portion FM and the ring portion FR. Rotation of the motor causes pistons to reciprocate within the crankcase  20  and causes the fan F to rotate, as will be described later in detail. This can cool the whole compressor A. 
       FIG. 3  is a sectional view taken along line A-A of  FIG. 1 . Firstly, the motor M will be described. The motor M includes: coils  30 , a rotor  40 , a stator  50 , and a printed circuit board PB. The stator  50  is made of metal. The stator  50  is secured to the crankcase  20 . The plural coils  30  are wound around the stator  50 . The coils  30  are electrically connected with the printed circuit board PB. As for the printed circuit board PB, conductive patterns are formed on an insulating board having rigidity. A non-illustrated power supply connector for supplying power to the coils  30 , a signal connector, and other electronic parts are mounted on the printed circuit board PB. For example, the electronic part is an output transistor (a switching element) such as an FET for controlling an energized state of the coils  30 , or a capacitor. The coils  30  are energized, so the stator  50  is energized. 
     The rotor  40  includes: a rotational shaft  42 ; a yoke  44 ; and one or plural permanent magnets  46 . The rotational shaft  42  is rotationally supported by plural bearings BR 1  and BR 2  arranged within the crankcase  20 . The yoke  44  is secured to the rotational shaft  42  through a hub  43 , so the yoke  44  rotates together with the rotational shaft  42 . The yoke  44  has a substantially cylindrical shape and is made of metal. One or plural permanent magnets  46  are secured to the inner circumferential side of the yoke  44 . The permanent magnets  46  face the outer circumferential surface of the stator  50 . The coils  30  are energized, so the stator  50  is energized. Thus, the magnetic attractive force and the magnetic repulsive force are generated between the permanent magnets  46  and the stator  50 . This magnetic force allows the rotor  40  to rotate with respect to the stator  50 . As mentioned above, the motor M is an outer rotor type motor in which the rotor  40  rotates. 
     A body portion FM of the fan F is secured to the yoke  44 . Specifically, the body portion FM of the fan F is secured to the yoke  44  by press-fitting or engaging, but the secured manner is not limited to this. The body portion FM is provided with plural holes FH to reduce the weight thereof. Also, the yoke  44  is provided with holes H. The fan F is secured to the yoke  44  such that the holes H of the yoke  44  overlap the several holes FH of the fan F. This permits air to flow into the motor M through the holes H and FH. This can promote the heat radiation of the inside of the motor M, for example, the heat radiation of the coils  30 . Also, the air which has flowed into the motor M through the holes H and FH partially flows toward the cylinder heads  15   a  to  15   d  and the crankcase  20  through clearances between the stator  50  and the permanent magnet  46 . It is therefore possible to cool the compressor A which is heated by the sliding of the pistons and adiabatic compression of air. Additionally, the stator  50  is partially exposed from the holes H, as illustrated in  FIGS. 1 and 2 . 
     Next, the internal structure of the crankcase  20  will be described. The rotational shaft  42  extends within the crankcase  20 . The plural pistons  25   a  to  25   d  are connected to a part of the rotational shaft  42  within the crankcase  20 . The proximal end of the piston  25   a  is connected to the position through a bearing at a position eccentric to the center position of the rotational shaft  42 . The rotation of the rotational shaft  42  in the single direction permits the piston  25   a  to reciprocate. Likewise, the other cylinders  10   b  to  10   d  and the other pistons  25   b  to  25   d  respectively moving therewithin have the same structure. The positional phase difference between the four pistons  25   a  to  25   d  is 90 degrees. The crankcase  20  is provided with a lower wall portion  21   f  at a side opposite to the motor M. 
     Cylinder bodies  12   a  and  12   c  are enclosed within the crankcase and secured to the internal surfaces of the middle wall portions  21   a  and  21   c  of the crankcase  20 , respectively. When the rotational shaft  42  rotates, the distal end of the piston  25   a  slides on the cylinder body  12   a . Herein, a cylinder chamber  13   a  is defined by the distal end of the piston  25   a , the cylinder body  12   a , and the middle wall portion  21   a of the crankcase  20 . The capacity of the cylinder chamber  13   a  increases and decreases by the reciprocation of the piston  25   a . Likewise, the other pistons and the other cylinder bodies are configured in the same manner. 
     As illustrated in  FIG. 2 , an air hole  24   c  is provided with the middle wall portion  21   c  of the crankcase  20 . The reciprocation of the piston  25   a  permits air to be introduced into the crankcase  20  through the air hole  24   c . The distal end of the piston  25   a  is provided with a communication hole  26   a . The end surface of the distal end of the piston  25   a  is provided with a non-illustrated valve member for opening and closing the communication hole  26   a . An exhaust chamber  18   a  is defined between the cylinder head  15   a  and the middle wall portion  21   a . The cylinder chamber  13   a  and the exhaust chamber  18   a  are separated by the middle wall portion  21   a  formed with a communication hole  22   a  communicating the cylinder chamber  13   a  with the exhaust chamber  18   a . The communication hole  22   a  is opened or closed by a valve member Va secured to the outer surface of the middle wall portion  21   a . As can be seen in  FIG. 3 , the interior diameter of exhaust chamber  18   a  matches in size with the interior diameter of cylinder chamber  13   a . Likewise, the other cylinder heads  15   b  to  15   d  and the wall portions  21   b  to  21   d  are configured in the same manner. As shown in  FIGS. 2-3 , the cylinder heads are smaller than the respective outer surfaces of the middle wall portion to which they are affixed. 
     The reciprocation of the piston  25   a  changes the capacity of the chamber  13   a . In response to this, air is introduced to the chamber  13   a  through the communication hole  26   a  and is compressed within the chamber  13   a . The compressed air is discharged into the exhaust chamber  18   e  through the communication hole  22   a . An air hole  19   a  is provided with the exhaust chamber  18   a . A tube is connected to such an air hole  19   a.    
     Likewise, the other cylinders  10   b  to  10   d  have the same structure. Thus, air introduced into the crankcase  20  through the air holes formed therein is compressed by the reciprocation of the pistons  25   a  to  25   d , and is discharged outside the crankcase  20 . Additionally, as illustrated in  FIG. 3 , balancers B 1  and B 2  are connected to the rotational shaft  42  within the crankcase  20 . 
     As illustrated in  FIG. 3 , the cylinder body  12   a  is arranged within the crankcase  20 , and the wall portion  21   a  of the crankcase  20  functions as a seating portion where that piston  25   a  is seated. Likewise, the other wall portions  21   b  to  21   d  function as seating portions on which the pistons  25   b  to  25   d  are seated, respectively. Additionally, in order to avoid collision noise in seating the piston, a slight gap may be made so as not to seat the piston completely. Thus, the compressor A is reduced in size in such a direction that the pistons  25   a  to  25   d  reciprocate, that is, in the direction perpendicular to the rotational shaft  42 . This will be described below. 
       FIG. 4  is a explanatory view of an example of a compressor A′ having the structure different from the compressor A according to the present embodiment. Additionally, in the compressor A′, similar components of the compressor A according to the first embodiment are designated with similar reference numerals and a description of those components will be omitted. Also,  FIG. 4  is a partially sectional view of the compressor A′. As illustrated in  FIG. 4 , as for the compressor A′, a cylinder body  12   a ′ is secured to an outer surface of a wall portions  21   a ′ of a crankcase  20 ′. Also, a cylinder head  15   a ′ is secured to the cylinder body  12   a ′. A partition member  21 A′ is provided between a chamber  13   a ′ defined in the cylinder body  12   a ′ side and an exhaust chamber  18   a ′ defined in the cylinder head  15   a ′ side. The partition member  21 A′ functions as a seating portion where the distal end of a piston  25   a ′ is seated. Thus, the wall portions  21   a ′ of the crankcase  20 ′ and the partition member  21 A′ are arranged in the direction perpendicular to a rotational shaft  42 ′. 
     Also, a wall portions  21   c ′ and a partition member  21 C′ are arranged in the same manner. The other wall portion and the other partition member are arranged in the same manner. For this reason, the compressor A′ is increased in size in the direction perpendicular to the rotational shaft  42 ′. 
     However, in the present embodiment, the wall portions  21   a  to  21   d  of the crankcase  20  functions as the seating portions for the pistons  25   a  to  25   d,  respectively. Thus, the compressor A according to the present embodiment does not need the partition member  21 A′. Thus, in the compressor A according to the present embodiment, the size is reduced in such directions that the pistons  25   a  to  25   d  reciprocate, and the number of the parts is reduced. 
     Also, in the compressor A′ illustrated in  FIG. 4 , the wall portions  21   a ′ and  21   c ′ of the crankcase  20 ′ are formed with cutout portions  21   a ′l and  21   c ′I having the size to escape axes of the pistons  25   a ′ and  25   c ′, respectively. Also, the other wall portions have cutout portions in the same manner. On the other hand, in the compressor A according to the present embodiment, although the wall portion  21   a  of the crankcase  20  is provided with the communication hole  22   a , the wall portion  21   a  is not provided with such a large cutout portion  21   a ′ 1  formed in the wall portion  21   a ′ of the compressor A′. Therefore, the hardness of the crankcase  20  is greater than that of the crankcase  20 ′. Thus, the durability of the crankcase  20  is improved. Also, the crankcase  20  has high hardness, so it is easy to process the crankcase  20 . 
     In the compressor A′, the above mentioned cutout portion  21   a ′ 1  is provided in the wall portion  21   a ′ of the crankcase  20 ′, and the cylinder body  12   a ′ is secured to the outer surface of the wall portion  21   a ′. Therefore, air might leak from a gap between the wall portion  21   a ′ and the cylinder body  12   a ′, so that drive noise might occur. In the present embodiment, such a large cutout portion is not provided in the crankcase  20 . It is thus possible to prevent air from leaking from the crankcase  20  and to prevent the drive noise from occurring. Also, it is conceivable that a sealing member such as a rubber member is arranged so as to cover the gap in order to prevent air from leaking therefrom. However, such a sealing member is arranged, so that the number of the parts is increased. In the crankcase  20  according to the present embodiment, there are few points where air might leak, as compared with the crankcase  20 ′. Thus, the number of such seal members for preventing air from leaking is reduced. 
     Also, the motor M is the outer rotor type motor. The outer rotor type motor tends to have a torque higher than that of an inner rotor type motor, providing that they have the same size. In other words, if the outer rotor type motor has the same output as an inner rotor type motor, the outer rotor type motor can be made smaller. Thus, the motor M of the compressor A according to the present embodiment is made small. 
     Also, the fan F is secured to the yoke  44  of the motor M. The compressor A is reduced in size in the axial direction of the rotational shaft  42 , for example, as compared with a case where the fan is arranged such that the fan and the motor M sandwich the crankcase  20 . 
     Additionally, in the compressor A according to the present embodiment, air discharged from each of the cylinder heads  15   a  to  15   d  are combined by a tube or a pipe. That is, the crankcase  20  is not provided with a flow path for combining air discharged from each of the cylinder heads  15   a  to  15   d . Thus, it is easy to manufacture the crankcase  20 , and the crankcase  20  is reduced in size and weight, as compared with a case where the crankcase is provided with the flow path. 
     The Fan F is made of synthetic resin. The Yoke  44  where the fan F is secured is made of metal. The attenuation rate of the vibration of the fan F is greater than that of the rotor  40 . It is therefore possible to reduce the drive noise of the compressor A. Further, the ring portion FR is provided at the ends of the plural blades FB to prevent an operator from touching the ends of the blades FB and getting injured. Also, it is preferable that the diameter of the fan F should be bigger than the surface of the compressor perpendicular to the rotational shaft  42 . 
     As mentioned above, the compressor A is reduced in size, since the cylinder body  12   a  is secured to the internal surface of the wall portion  21   a  of the crankcase  20 , the cylinder head  15   a  is secured to the outer surface of the wall portion  21   a , the crankcase  20  is not provided with the flow path for communicating the plural cylinder heads  15   a  and  15   b  with each other, the outer rotor type motor M is employed, and the fan F is secured to the yoke  44  of the motor M. 
     Also, in the compressor A, the drive noise is reduced, since the wall portions  21   a  to  21   d  of the crankcase  20  are not provided with a large cutout portion, and the attenuation rate of the fan F is greater than that of the rotor  40 . 
     Additionally, when the object device is connected at the intake side of the compressor A or when a check valve is arranged in a manner opposite to a manner of the compressor A, the compressor A acts as a vacuum machine. 
     Also, in another case where the compressor A is used as a vacuum machine, the object device is connected to the air hole  24   c . In this case, the valve member provided within the cylinder  10   a  may be the same as the compressor A. 
     While the exemplary embodiments of the present invention have been illustrated in detail, the present invention is not limited to the above-mentioned embodiments, and other embodiments, variations and modifications may be made without departing from the scope of the present invention. 
     The above embodiment is an example of the configuration where four pairs of the cylinder and the piston are provided. However, the present invention is not limited to this configuration. For example, one, two, or three pairs of the cylinder and the piston may be provided. More than four pairs of the cylinder and the piston may be provided.