Thrust bearing arrangement for a drive shaft of a scroll compressor

To reduce a load applied to the thrust bearing, to prevent the thrust bearing from seizing and to improve the service life of the thrust bearing, the thrust bearing is provided between a drive shaft and a block to seal a high-pressure side space from a low-pressure side space. By providing an oil supply through hole, one end of which opens into high-pressure side space and the other end of which opens into a space formed by inserting the shaft into the insertion hole, high-pressure lubricating oil can be supplied to the space. The constric within the shaft with the effect of the constriction clearance is formed between the aforementioned oscillating shaft and the insertion hole, and a pressure differential between the two ends of the drive shaft is eliminated. Furthermore, by forming a circular oil groove at a sliding surface where the aforementioned thrust bearing and the drive shaft are in contact with each other and communicating channels that communicate between the circular oil groove and an external circumferential area of the aforementioned thrust bearing, the high-pressure lubricating oil is induced to the circular oil groove and the communicating channels to apply an upward force to the drive shaft.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a scroll type compressor that changes the 
volumetric capacity of a compression space formed with a fixed scroll 
member and an orbiting scroll member to compress the on-board coolant. 
2. Description of the Related Art 
In scroll type compressors of the prior art, in which a compression space 
is formed by fitting together a fixed scroll member that is provided with 
a fixed scroll in the form of a coil and an orbiting scroll member that is 
provided with an orbiting scroll in the form of a coil wherein the 
aforementioned orbiting scroll member makes an orbiting movement relative 
to the fixed scroll member, the volumetric capacity of the aforementioned 
compression space expands and contracts repeatedly to perform intake, 
compression and discharge. Thus, the lubrication and sealing of the 
sliding contact surface between the fixed scroll member and the sliding 
scroll member are crucial factors. 
Accordingly, the scroll type compressor disclosed in Japanese Patent 
Unexamined Publication No. H3-149391 includes a rotary displacement type 
oil pump in its structure, so that a sufficient quantity of lubricating 
oil can be reliably supplied to the bearings regardless of the flow rate 
of the lubricating oil supplied to the compression work space. With this, 
a large quantity of lubricating oil can be assured even when high loads 
are applied to the revolving drive bearing, the eccentric bearing and the 
first main bearing. 
Also, the scroll type compressor disclosed in Japanese Patent Unexamined 
Publication No. H3-61689 is provided with a cylinder section towards the 
direction of reciprocal movement of the Oldham's coupling on the wall 
surface facing opposite the external circumferential surface of the 
Oldham's coupling which prevents auto rotation of the orbiting scroll 
member. A liner is provided that moves back and forth within the 
aforementioned cylinder section in conformance with the operation of the 
Oldham's coupling to push out the lubricating oil. This structure allows 
the quantity of supplied oil to be increased as the number of rotations in 
the drive unit increases. 
Likewise, the Japanese Patent Unexamined Publication No. H3-105093 
discloses a structure in which a pressurized passage, which is subject to 
a centrifugal force from the drive shaft, is formed in the drive shaft 
towards the outside in the direction of the radius of the drive shaft, 
constituting a so-called centrifugal pump to supply lubricating oil. 
However, with the scroll type compressors in the examples quoted above, it 
is required that a non ferrite material such as aluminum be used for the 
fixed scroll member and the orbiting scroll member to reduce weight and 
cost, and a problem arises therefrom. Because of the high back pressure on 
the orbiting scroll member, it is pressed towards the fixed scroll member, 
and as a result, the sliding area where the orbiting scroll member and the 
fixed scroll member are in contact with each other tends to seize, even 
though the quantity of oil supplied to the sliding contact surface is 
increased. Thus, it is necessary to reduce the back pressure applied to 
the orbiting scroll member. 
Also, since the drive shaft is provided over the high-pressure side, where 
a drive means is provided, through the low-pressure or intermediate drive 
side where the orbiting scroll member is provided, a force is constantly 
applied towards the orbiting scroll member side by the pressure 
differential between the high-pressure and low-pressure regions or the 
pressure differential between the high-pressure and intermediate pressure 
regions. Because of this, it is required that a bearing (thrust bearing) 
be provided at the end of the drive shaft to receive the load applied by 
this force. 
However, when the load is large, the thrust bearing itself can seize, and 
as the load is applied constantly, the service life of the thrust bearing 
is shortened. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a scroll type compressor 
in which the load on the thrust bearing is reduced, seizure of the thrust 
bearing is prevented and the service life of the thrust bearing is 
extended. 
In order to achieve this object, the present invention is a scroll type 
compressor that comprises; an electric motor that is provided in a high 
pressure space within a sealed case, and a stator that is fixed within the 
sealed case, a rotor that is secured to the drive shaft. An orbiting shaft 
is formed as a decentered extension of the aforementioned drive shaft. An 
orbiting scroll member is provided with an insertion hole into which the 
orbiting shaft is fitted, and a fixed scroll member fits by interlocking 
with the orbiting scroll member to form a compression space. A block holds 
the orbiting scroll member between the fixed scroll member and the block 
in such a manner that it can orbit freely against the fixed scroll member, 
and is provided with a through hole that accommodates a main bearing, 
which holds the aforementioned drive shaft. An toroidal thrust bearing is 
provided under the aforementioned through hole and between the drive shaft 
and the block, and supports the aforementioned drive shaft in such a 
manner that it can rotate freely and, at the same time, seals off the high 
pressure side that communicates with the oil reservoir that is formed in 
the lower section of the high-pressure space from the low pressure side, 
where the aforementioned orbiting scroll member orbits. An oil supply 
through hole has one end which opens into the high-pressure side space 
that is sealed off by the aforementioned thrust bearing and another end 
which opens into the space within the shaft formed by inserting the 
orbiting shaft into the aforementioned insertion hole. 
Therefore, in the present invention, since the high-pressure side space and 
the low-pressure side space are sealed off from each other by the thrust 
bearing provided between the drive shaft and the block, and since the oil 
supply through hole is provided with one end opening into the 
high-pressure side space that is sealed off by the thrust bearing and the 
other end opening into the space within the shaft, high-pressure 
lubricating oil can be supplied to the end of the orbiting shaft via the 
oil supply through hole, eliminating the pressure differential between the 
upper end and the lower end of the drive shaft. Consequently, the load on 
the thrust bearing is reduced, the thrust bearing is prevented from 
seizing and the durability of the thrust bearing is improved. 
Also, in order to achieve the object, the present invention is a scroll 
type compressor that comprises; an electric motor that is provided in a 
high pressure space within a sealed case, a stator that is fixed within 
the sealed case, a rotor that is secured to the drive shaft, an orbiting 
shaft, which is formed as a decentered extension of the drive shaft, an 
orbiting scroll member is provided with an insertion hole into which the 
orbiting shaft is fitted, and a fixed scroll member fits by interlocking 
with the orbiting scroll member to form a compression space. A block holds 
the orbiting scroll member between the fixed scroll member and the block 
in such a manner that it can orbit freely against the fixed scroll member, 
and is provided with a through hole that accommodates the main bearing, 
which holds the aforementioned drive shaft. A toroidal thrust bearing is 
provided under the aforementioned through hole and between the drive shaft 
and the block which supports the aforementioned drive shaft in such a 
manner that it can rotate freely and which, at the same time, seals off 
the high pressure side that communicates with the oil reservoir formed in 
the lower section of the high-pressure space from the low pressure side, 
where the aforementioned orbiting scroll member oscillates. The thrust 
bearing is further provided with a circular oil groove formed on the 
sliding contact surface of the thrust bearing where it is in contact with 
the drive shaft and communicating channels that communicate between the 
circular oil groove and the external circumferential side surface of the 
aforementioned thrust bearing. 
As a result, with the toroidal thrust bearing provided between the drive 
shaft and the block to receive the load applied to the aforementioned 
drive shaft, which is in turn provided with a circular oil groove formed 
on the sliding surface that comes in contact with the drive shaft and 
communicating channels that communicate between this circular oil groove 
and the external circumferential side surface, high-pressure lubricating 
oil can be supplied from the aforementioned high-pressure side space to 
the aforementioned circular oil groove via the communicating channels, and 
the upward force applied to the drive shaft can be increased, reducing the 
load to a degree equivalent to this applied force. Consequently, seizure 
of the thrust bearing is prevented and the durability of the thrust 
bearing is improved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following is an explanation of the preferred embodiments, with 
reference to the drawings. 
In a scroll type compressor 1 shown in FIG. 1 and FIG. 2, a sealed case 6 
is structured with a cylindrical member 3 that is provided with a coolant 
intake port 2, a cap member 4 that seals the upper end of the cylindrical 
member 3, and a base member 5 that seals the lower end of the cylindrical 
member 3. Note that the cap member 4 is provided with a coolant outlet 
port 7 and a power supply terminal 9 for a electric motor 8. 
The electric motor 8 may be, for example, a DC brushless motor provided 
with a drive shaft 10, a rotor 11 which is secured onto the drive shaft 10 
and which is surrounded by a permanent magnet and a stator 13, which is 
secured onto the internal circumferential surface of the cylindrical 
member 3 and wrapped by a coil winding 12. The drive shaft 10 is held by a 
drive shaft holding member 14 via a bearing 15 in such a manner that it 
can turn freely. It is provided with an upper balance weight 16 near its 
upper end. The rotor 11 is secured below the upper balance weight 16. 
Below the rotor 11, a lower balance weight 17 is secured, and the lower 
portion of the balance weight 17 is inserted in a through hole 19 that is 
formed in a block 18, the details of which will be explained below. The 
lower portion of the balance weight 17 is held by a main bearing 20 so 
that it can rotate freely. Projecting from the lower end of the drive 
shaft 10, is an eccentric shaft 21 that is provided off center of the 
drive shaft. 
The block 18 is secured to the internal circumferential surface of the 
aforementioned cylindrical member 3 and is provided with the through hole 
19, which is formed by piercing the center. A fixed scroll member 22, 
details of which will come later, is secured with a bolt 27 to the lower 
end surface of the block 18, and with this, an orbiting scroll member 23, 
also to be explained later, is clamped in such a manner that it can orbit 
freely. Also, in order to hold the drive shaft 10, in addition to the main 
bearing 20, a thrust bearing 37, to be explained later, is provided 
between the drive shaft 10 and block 18. Note that the diameter of the 
lower section of the aforementioned through hole 19 is increased so that a 
projected portion 23b of the orbiting scroll member 23, where an insertion 
hole 23a is formed, can make its orbiting motion. 
An oldham's-ring housing groove 25 is formed on the surface of the block 18 
where the orbiting scroll member 23 slides to contain an oldham's ring 24, 
which prevents the orbiting scroll member 23 from rotating. A scroll 
bearing 26, which is provided with a lubricating oil groove with an 
appropriate constriction formed in it, is also provided on this sliding 
surface. 
The orbiting scroll member 23 is provided with the projected portion 23b 
formed at the center of its upper end surface. The insertion hole 23a is 
formed in the projected portion 23b, into which the orbiting shaft 21 is 
fitted. An orbiting scroll 23c is formed in a coil shape on the lower end 
surface of the orbiting scroll member 23. 
The fixed scroll member 22 is provided with a fixed scroll 22a, formed in a 
coil shape, which interlocks with the aforementioned orbiting scroll 23c 
to form a compression space 28. An intake chamber 22b is provided on one 
side between the aforementioned coolant intake port 2 and the forward end 
of the compression space 28. The coolant outlet 22c is also provided at 
the center of the lower end surface, and communicates with the last level 
of the compression space 28. A cover 30, which forms a the coolant outlet 
passage 29, is secured onto the lower end surface of the fixed scroll 
member 22. Note that in the area of the middle level of the aforementioned 
compression space 28, a bypass channel 31 is provided which communicates 
between the compression space 28 and the aforementioned coolant outlet 
passage 29. It is opened if the pressure inside the compression space 28 
exceeds a specific value. When the electric motor 8 is driven in the 
scroll type compressor 1, structured as described above, the orbiting 
scroll member 23 secured decentered to the drive shaft 10 of the electric 
motor 8, makes an orbiting motion relative to the fixed scroll member 22 
and the compression space 28, formed by the orbiting scroll 23c and the 
fixed scroll 22a, gradually reduces its volumetric capacity from the 
intake side to the outlet side. The coolant taken in through the coolant 
intake port 2 is compressed and then discharged from the coolant outlet 
22c into the coolant outlet passage 29. Then it passes through a coolant 
conduit 32, which is a continuous passage through the fixed scroll member 
22 and the block 18, passes through a extended pipe 33 mounted on the 
block 18, reaches a space (high pressure chamber) 34 where the 
aforementioned electric motor 8 is provided and is sent out via the 
coolant outlet port 7 to the next process in the cooling cycle. 
Also, in this high pressure chamber 34, the lubricating oil that has been 
separated by the rotation of the electric motor 8 is stored in an oil 
reservoir 35 that is formed over the block 18. The lubricating oil thus 
stored in the oil reservoir 35 flows from a lubricating oil intake port 36 
to a high-pressure side space 41 over the aforementioned thrust bearing 37 
due to the difference in pressure between the high pressure and the low 
pressure on the intake side of the compression space 28, because the 
lubricating oil is subject to the pressure of the aforementioned 
high-pressure chamber 34. 
The lubricating oil which has flowed into the high-pressure side space 41, 
while lubricating the main bearing 20, is divided to follow two different 
paths. One path is the passage up the oil supply groove 38, formed on an 
incline on the external circumferential surface of the drive shaft 10, so 
the oil will reach the upper end. The other passage passes the oil supply 
through the hole 39 from the high-pressure side space 41 over the thrust 
bearing 37 and travels to a space 40 within the shaft formed by the end of 
the aforementioned eccentric shaft 21 and the insertion hole 23a. In the 
first passage, the lubricating oil flows out to the outside from the upper 
end of the oil supply groove 38 and returns to the oil reservoir 35. 
In the second passage, because of the constricting effect of the clearance 
formed by the external circumferential surface of the aforementioned 
eccentric shaft 21 and the internal circumferential surface of the 
insertion hole 23a, the pressure in the space 40 within the shaft is 
maintained at a high level. Also, in this second passage, the lubricating 
oil passes through the clearance and reaches the low-pressure side space 
42, which is beneath the thrust bearing 37, while lubricating the sliding 
area of the external circumferential surface of the eccentric shaft 21 and 
the internal circumferential surface of the insertion hole 23a. 
The pressure in the aforementioned low-pressure side space 42 is controlled 
at an intermediate or low pressure through the constricting effect of the 
clearance between the insertion hole 23 and the eccentric shaft 21 on the 
upstream side and the constricting effect of the narrow portion formed in 
the aforementioned scroll bearing 26 on the downstream side, and the 
quantity of lubricating oil traveling to the oldham's ring housing groove 
via the scroll bearing 26 can be adjusted with the pressure differential 
between the pressure on the high-pressure side and the low pressure on the 
intake side. The lubricating oil which has traveled to the oldham's ring 
housing groove 25 then travels, after lubricating the oldham's-ring 24, to 
the intake chamber 22b formed in the fixed scroll member 22. From the 
intake chamber 22b the lubricating oil is carried along with the coolant 
into the compression space 28 where it lubricates and seals the 
compression space 28. 
Therefore, since the pressure in the space 40 within the shaft is 
maintained at a high level by the effect of the constriction of the 
clearance formed by the external circumferential surface of the 
aforementioned eccentric shaft 21 and the internal circumferential surface 
of the insertion hole 23a, high upward pressure is applied to the 
eccentric shaft 21. Consequently, the downward load applied to the drive 
shaft 10 can be reduced, reducing the load on the thrust bearing 37. 
As has been explained so far, the high-pressure side and the low-pressure 
side are sealed off from each other with the thrust bearing 37 provided 
between the drive shaft 10 and the block 18. The oil supply through hole 
39 has one end of which opens into the high-pressure side, which is sealed 
off by the aforementioned thrust bearing 37, and the other end which opens 
into the space 40 within the shaft formed with the end of the eccentric 
shaft 21, which extends decentered from the drive shaft. The insertion 
hole 23a, into which the eccentric shaft 21 is fitted, has a specific 
constriction created in the circular clearance formed between the 
aforementioned eccentric shaft 21 and the aforementioned insertion hole 
23a. Thus high-pressure lubricating oil can be supplied to the end of the 
eccentric shaft 21 via the oil supply through hole 39, eliminating the 
pressure differential between the upper end and the lower end of the drive 
shaft 10. As a result, the load applied to the thrust bearing 37 is 
reduced, seizure of the thrust bearing is prevented and the durability of 
the thrust bearing is improved. 
Also, in the structure described above, pressure on the aforementioned 
thrust bearing 37 is decreased gradually and linearly from a high-pressure 
Pd due to the lubricating oil supplied to the high-pressure side space 41, 
to an intermediate pressure Ps on the low-pressure side space 42, as shown 
in FIG. 5. This pressure applies an upward force to the drive shaft 10, as 
indicated by F1. Because of this, by increasing this applied force, the 
load applied to the thrust bearing 37 can be further reduced. 
For this reason, the toroidal thrust bearing 37 is provided with a circular 
oil groove 37a, formed at a specific position on the sliding surface that 
comes in contact with the drive shaft 10, and is also provided with a 
plurality of communicating channels 37b that are formed in a radial 
pattern and that communicate between the circular oil groove 37a and the 
external circumferential surface of the aforementioned thrust bearing 37 
as shown in FIG. 3. Since the high pressure Pd can be induced to the 
communicating channels 37b and the circular oil groove 37a and the high 
pressure Pd can be maintained on the surface where the thrust bearing 37 
and the drive shaft 10 come in contact through the circular oil groove 
37a, as shown in FIG. 6, an applied force F2 can be achieved. 
FIG. 4 shows an example of the thrust bearing 37 in which a plurality of 
communicating channels 37c are formed in a tangential direction to, and 
extending from the circular oil groove 37a, that is formed in the thrust 
bearing 37. With the communicating channels 37c, the lubricating oil can 
be supplied in the direction of the rotation of the drive shaft 10, 
achieving a lubricating effect on the sliding surface where the thrust 
bearing comes in contact with the drive shaft 10 as well as the advantages 
described earlier. 
With the toroidal thrust bearing 37 as has been described so far, which is 
provided between the drive shaft 10 and the block 18, and which receives 
the load applied to the aforementioned drive shaft 10, and which is 
provided with the circular oil groove 37a and the communicating channels 
37b, 37c, which extend from the circular oil groove 37a to the external 
circumferential surface to assure a supply of high-pressure lubricating 
oil from the aforementioned lubricating oil intake port 36 to the 
aforementioned circular oil groove 37a via these communicating channels 
37b, 37c, the upward force that is applied to the drive shaft at the 
contact surface where the thrust bearing 37 and the drive shaft 10 are in 
contact can be increased, resulting in a reduction in the load on the 
thrust bearing 37. Consequently, seizure of the thrust bearing 37 is 
prevented and the durability of the thrust bearing 37 is also improved.