Pumps – Condition responsive control of drive transmission or pump... – Adjustable cam or linkage
Reexamination Certificate
1999-09-30
2002-07-09
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of drive transmission or pump...
Adjustable cam or linkage
C417S365000
Reexamination Certificate
active
06416297
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a compressor used in an on-vehicle air conditioner. Particularly, the present invention pertains to a variable displacement compressor that varies its displacement based on environmental conditions.
FIG. 10
illustrates a typical variable displacement compressor. The compressor of
FIG. 10
includes a front housing
201
, a cylinder block
202
and a crank chamber
203
, which is defined between the front housing
201
and the cylinder block
202
. A drive shaft
204
extends and is rotatably supported in the crank chamber
203
.
A cam plate, or swash plate
205
, is supported by the drive shaft
204
in the crank chamber
203
by a lug plate
205
a.
The swash plate
205
rotates integrally with and is inclined relative to the drive shaft
204
. The lug plate
205
a
is secured to the drive shaft
204
to transmit rotation of the drive shaft to the swash plate
205
. The lug plate
205
a
is supported by a thrust bearing
205
b
located between the lug plate
205
a
and the front housing
201
. A lip seal
203
a
is located between the circumferential surface of the front portion of the drive shaft
204
and the inner surface of an opening
201
a
of the front housing
201
to seal the crank chamber
203
.
Cylinder bores
202
a
are formed in the cylinder block
202
. A piston
206
is reciprocally housed in each bore
202
a
. The pistons
206
are coupled to the swash plate
205
. A rear housing
208
is secured to the cylinder block
202
by way of a valve plate
207
. A suction chamber
209
and a discharge chamber
210
are defined in the rear housing
208
. Refrigerant gas is drawn into the suction chamber
209
before being compressed by reciprocation of the pistons
206
in the cylinder bores
202
a
. The compressed gas is then conducted to the discharge chamber
210
.
A shaft bore
202
b
is formed in the center of the cylinder block
202
. The rear portion of the drive shaft
204
is fitted in the shaft bore
202
b
. A snap ring
211
is fixed to the rear portion of the shaft bore
202
b
. A thrust bearing
212
is located at the rear end of the drive shaft
204
. A coil spring, or support spring
213
, is located between the thrust bearing
212
and the snap ring
211
. The support spring
213
urges the drive shaft
204
forward and compensates for dimensional errors of the parts. The support spring
213
also prevents the drive shaft
204
from chattering in the axial direction. The front side of the drive shaft
204
refers to the end connected to a drive source, or engine Eg, and the rear end of the drive shaft
204
refers to the opposite end.
The discharge chamber
210
and the crank chamber
203
are connected by a supply passage
214
. A control valve
215
is located in the supply passage
214
to adjust the flow rate of refrigerant gas. The control valve
215
, which is an electromagnetic valve, controls the size of an opening between a valve body
216
and a valve hole
217
based on external information such as the temperature of an evaporator connected to the compressor, the temperature of the passenger compartment, a target value of the compartment temperature and the speed of the engine Eg. Accordingly, the difference between the pressure Pc in the crank chamber
203
and the pressure in the cylinder bores
202
a
is changed. The inclination of the swash plate
205
is changed in accordance with the changed pressure difference. The abutment of the swash plate
205
against a limit member or, stop ring
218
, prevents the inclination of the swash plate
205
from being less than a predetermined minimum inclination.
An electromagnetic clutch
219
is attached to the front end of the drive shaft
204
to selectively transmit the force of the engine Eg. The clutch
219
includes an armature
220
and a pulley
221
. The armature
220
is secured to the drive shaft
204
and includes a surface perpendicular to the axis of the drive shaft
204
. The pulley
221
is coupled to the engine Eg. The armature
220
is located in front of the pulley
221
. A core
222
is located next to the pulley
221
. The armature
220
is coupled to and separated from the pulley
221
by exciting and de-exciting the core
222
.
When the target compartment temperature is significantly changed in a short time, or when the engine speed is suddenly increased, the compressor displacement is minimized. At this time, the control valve
215
abruptly widens the opening between the valve body
216
and the valve hole
217
based on the external information. Accordingly, highly pressurized refrigerant gas in the discharge chamber
210
is suddenly conducted to the crank chamber
203
, which quickly increases the pressure Pc of the crank chamber
203
. In this case, the pressure difference between the crank chamber
203
and the cylinder bores
202
a
with the pistons
206
in between is suddenly increased. A sudden change of pressure dramatically decreases the inclination of the swash plate
205
, which presses the swash plate
205
against the ring
218
.
The thrust load acting on the drive shaft
204
will now be described. The force F acting on the drive shaft
204
is expressed by the following equation (1).
F
=
Fgh
-
Fsp
-
∑
i
=
1
N
S
(
Pb
(
i
)
-
Pc
)
(
1
)
Fgh represents the force that the clutch
219
applies to the drive shaft. Fsp represents a load at the rear end of the drive shaft
204
. N represents the number of the cylinder bores
202
a
. S represents the cross-sectional area of each cylinder bore
202
a
. Pb(i) represents the pressure in each cylinder bore
202
a
. Pc represents the pressure of the crank chamber
203
. The equation (1) can be approximated by an equation (2) below, which has been obtained through experiments.
F
=
Fgh
-
Fsp
-
SN
7
(
3
Pd
+
4
Ps
-
7
Pc
)
(
2
)
Ps represents the pressure of the suction chamber
209
(suction pressure). Pd represents the pressure of the discharge chamber
210
.
When the swash plate
205
is pressed against the stop ring
218
, the equation (2), or the value F, is greater than zero (F>0). In other words, the drive shaft
204
receives a rearward force. The rearward force acts as a compression load and is transmitted to the support spring
213
via the thrust bearing
212
thereby compressing the spring
213
.
However, since the spring
213
is a coil spring, a change of the axial dimension of the spring
213
, as shown in
FIG. 4
, does not significantly increases the force of the spring
213
. Therefore, the support spring
213
allows the drive shaft
204
to move rearward. When the drive shaft
204
is moved rearward, the stroke range of the pistons
206
, which are coupled to the drive shaft
204
through the swash plate
205
, is moved rearward. Accordingly, the top dead center position of each piston
206
is moved rearward.
When each piston
206
is at the top dead center, a predetermined space exists between the piston
206
and the valve plate
207
. The space prevents the pistons
206
from interfering with the valve plate
207
.
However, when the drive shaft
204
is moved rearward such that the top dead center of each piston
206
is moved by a distance greater than the axial dimension of the space between the top dead center and the valve plate
207
, the pistons
206
collide with the valve plate
207
. The collision generates noise and vibration and damages the piston
206
and the valve plate
207
. In other words, the life of the compressor is shortened.
When the drive shaft
204
is displaced rearward, the armature
220
, which is secured to the drive shaft
204
, is also moved rearward, or brought closer to the pulley
221
, which is coupled to the engine Eg. If the core
222
is de-excited in this state, the armature
220
may not be moved to a normal disconnection position but may contact the pulley
221
. This creates noise and heat in the clutch
219
and reduces the life of the clutch
219
.
Further, when the drive shaft
204
is moved rearward, the lip seal
203
a
is displaced from a contact area
Inaji Satoshi
Kato Keiichi
Kawaguchi Masahiro
Kurakake Hirotaka
Kurita Hajime
Freay Charles G.
Gray Michael K.
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan , LLP
LandOfFree
Stopping means for preventing movement of the drive shaft of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Stopping means for preventing movement of the drive shaft of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stopping means for preventing movement of the drive shaft of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2895264