Information
-
Patent Grant
-
6289882
-
Patent Number
6,289,882
-
Date Filed
Thursday, February 10, 200024 years ago
-
Date Issued
Tuesday, September 18, 200122 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 123 5591
- 123 5593
- 060 611
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International Classifications
-
Abstract
A supercharger clutch system has a clutch housing (52) in which a clutch pack (84) is disposed to transmit torque from an input, such as a pulley (66), to one of the timing gears (58). The clutch pack (84) is disposed within a cage (92), having a spring seat member (98) adjacent thereto. A set of springs (104) biases the seat member and the clutch cage (92) to engage the clutch pack (84). On the opposite side, axially, of the clutch pack there is a piston (76) including a portion (80) surrounding the clutch cage (92) and engaging the seat member (98). The piston (76) and the clutch housing (52) define a pressure chamber (106) which, when pressurized, causes movement of the piston in a direction compressing the springs (104) and disengaging the clutch pack. The invention provides a method of controlling the clutch system by means of an electrohydraulic valve (110) which can communicate the pressure chamber (106) to either high pressure (112) or low pressure (132). The valve (110) is controlled by sensing throttle position (141) and modifying a command signal (130) to a coil (126) of the valve (110) in response to the throttle position (141), so that the rate of clutch engagement may be modulated in response to throttle position.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE DISCLOSURE
The present invention relates to a rotary blower, such as a supercharger for supercharging an internal combustion engine. More particularly, the invention relates to a supercharger having a fluid pressure operated clutch assembly adapted to transmit torque from an input to one of the supercharger rotors.
Although the present invention may be used advantageously with superchargers having various rotor types and configurations, such as the male and female rotors found in screw compressors, it has been developed for use with a Roots blower type of supercharger, and will be described in connection therewith.
As is well known to those skilled in the art, the use of a supercharger to increase or “boost” the air pressure in the intake manifold of an internal combustion engine results in an engine having greater horsepower output capability than would occur if the engine were normally aspirated, (i.e., if the piston would draw air into the cylinder during the intake stroke of the piston). However, the conventional supercharger is mechanically driven by the engine, and therefore, represents a drain on engine horsepower whenever engine boost is not required. For the above and other reasons, it has been known for several years to provide some sort of engageable/disengageable clutch assembly disposed in series between the input (e.g., a belt driven pulley) and the blower rotors.
The assignee of the present invention has sold superchargers commercially including such clutch assemblies which operate electromagnetically. Unfortunately, the ON-OFF characteristics of electromagnetic clutches produce a transient load torque on the engine. For example, as the electromagnetic clutch is engaged, the result will be a “droop” in engine speed which will likely be perceived by the driver and may be manifested as an undesirable slowing down of the vehicle.
It is also known to provide a fluid pressure operated clutch assembly in which the clutch pack is spring biased toward a disengaged condition, and is moved toward an engaged condition in response to axial movement of a fluid pressure actuated piston member. In other words, the known supercharger clutch is of the “pressure-applied, spring-released” type. Although a supercharger with such a clutch arrangement can operate in a generally satisfactory manner, once the clutch is in either the engaged or the disengaged condition, the known arrangement does involve certain disadvantages during “transient” conditions, i.e., as the clutch assembly changes from the disengaged condition to the engaged condition, or vice versa. By way of example, a known supercharger clutch assembly of the pressure applied, spring released type requires a fairly long piston travel in order to achieve engagement of the clutch pack (or very high apply pressure), thus requiring substantial flow of fluid to accomplish the required piston movement.
Although such a high flow requirement is not a problem, once the engine has reached normal operating temperature, it frequently occurs that engagement of the clutch assembly is required soon after “cold engine start up”, while the engine oil is still cold. As a result, the known pressure applied, spring released system will have substantially longer time of engagement when the engine is cold than when the engine is warm. By way of example only, a typical engagement or release response time, as specified by the vehicle manufacturer, would be in the range of about 0.10 seconds. A substantially longer response time would result in the well known “turbo lag” feeling wherein the operator depresses the accelerator, but then there is a time lag before engine boost becomes noticeable, as is inherent in a turbo charger type of engine boost system. On the other hand, response time should not be so fast (when engaging) and so sudden as to result in a large torque spike being imposed upon the engine.
Another disadvantage associated with the pressure-applied type of supercharger clutch is that the oil pressure typically used is the engine lubrication oil circuit. As a result, the fluid pressure available to engage the clutch may be only in the range of about 20 psi., and even that very low pressure may not be available on a sufficiently consistent and predictable basis to be relied upon for engagement of the supercharger clutch, especially within the specified response time.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an improved supercharger and clutch assembly which overcome the above-described disadvantages of the prior art.
It is a more specific object of the present invention to provide an improved supercharger and clutch assembly which accomplishes the above-stated object, and which has both a variable and a controllable engagement and disengagement response time, thus avoiding transient overloading of the engine as well as a time lag upon engagement.
It is a further object of the present invention to provide such an improved supercharger and clutch assembly which operates in a consistent manner, substantially independent of variables such as engine oil temperature.
The above and other objects of the invention are accomplished by the provision of an improved method of controlling a rotary blower of the back flow or compression type having an input, a housing defining a blower chamber, and a pair of blower rotors disposed in the blower chamber and adapted to be driven by the input. A wet clutch is disposed in series driving relationship between the input and the blower rotors. The wet clutch includes spring means biasing the wet clutch toward one of an engaged in a disengaged condition, and a fluid pressure actuated piston having a pressure chamber biasing the wet clutch toward the other of the engaged and disengaged conditions.
The improved method of controlling the rotary blower is characterized by providing an electrohydraulic valve means operable to communicate the pressure chamber selectively to a source of high pressure and a source of low pressure. The method includes generating a command signal operable to bias the electrohydraulic valve means toward a position operable to communicate the pressure chamber to the source of whichever of the high pressure and the low pressure corresponds to the engaged condition. The method includes sensing a throttle position representative of change in commanded throttle position for the vehicle engine, and modifying the command signal in response to the throttle position whereby a change between the engaged and the disengaged conditions will occur more rapidly for a more rapid change in commanded throttle position.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic illustration of an intake manifold assembly having disposed therein a supercharger of the type which may utilize the present invention.
FIG. 2
is a front plan view of the supercharger shown schematically in FIG.
1
.
FIG. 3
is an enlarged, fragmentary, axial cross-section taken on line
3
—
3
of
FIG. 2
, and showing primarily the clutch assembly to be controlled by the method of the present invention, the clutch assembly being shown in its engaged condition.
FIG. 4
is an enlarged, fragmentary, axial cross-section taken on line
4
—
4
of
FIG. 2
, and showing primarily the control valve assembly which comprises one aspect of the control method of the present invention.
FIG. 5
is a logic flow diagram illustrating the control logic which comprises one aspect of the method of the present invention.
FIG. 6
is a graph of current versus time for the electromagnetic coil of the control valve assembly shown in
FIG. 4
, illustrating one aspect of the control method of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, which are not intended to limit the invention,
FIG. 1
is a schematic illustration of an intake manifold assembly, including a Roots blower supercharger and bypass valve arrangement of the type which is now well known to those skilled in the art. An engine, generally designated
10
, includes a plurality of cylinders
12
, and a reciprocating piston
14
disposed within each cylinder, thereby defining an expandable combustion chamber
16
. The engine includes intake and exhaust manifold assemblies
18
and
20
, respectively, for directing combustion air to and from the combustion chamber
16
, by way of intake and exhaust valves
22
and
24
, respectively.
The intake manifold assembly
18
includes a positive displacement rotary blower
26
of the backflow or Roots type, as is illustrated and described in U.S. Pat. Nos. 5,078,583 and 5,893,355, assigned to the assignee of the present invention and incorporated herein by reference. The blower
26
includes a pair of rotors
28
and
29
, each of which includes a plurality of meshed lobes. The rotors
28
and
29
are disposed in a pair of parallel, transversely overlapping cylindrical chambers
28
c
and
29
c
, respectively. The rotors may be driven mechanically by engine crankshaft torque transmitted thereto in a known manner, such as by means of a drive belt (not illustrated herein). The mechanical drive rotates the blower rotors at a fixed ratio, relative to crankshaft speed, such that the blower displacement is greater than the engine displacement, thereby boosting or supercharging the air flowing to the combustion chambers
16
.
The supercharger or blower
26
includes an inlet port
30
which receives air or air-fuel mixture from an inlet duct or passage
32
, and further includes a discharge or outlet port
34
, directing the charged air to the intake valves
22
by means of a duct
36
. The inlet duct
32
and the discharge duct
36
are interconnected by means of a bypass passage, shown schematically at
38
. If the engine
10
is of the Otto cycle type, a throttle valve
40
preferably controls air or air-fuel mixture flowing into the intake duct
32
from a source, such as ambient or atmospheric air, in a well known manner. Alternatively, the throttle valve
40
may be disposed downstream of the supercharger
26
.
Disposed within the bypass passage
38
is a bypass valve
42
which is moved between an open position and a closed position by means of an actuator assembly, generally designated
44
. The actuator assembly
44
is responsive to fluid pressure in the inlet duct
32
by means of a vacuum line
46
. Therefore, the actuator assembly
44
is operative to control the supercharging pressure in the discharge duct
36
as a function of engine power demand. When the bypass valve
42
is in the fully open position, air pressure in the duct
36
is relatively low, but when the bypass valve
42
is fully closed, the air pressure in the duct
36
is relatively high. Typically, the actuator assembly
44
controls the position of the bypass valve
42
by means of suitable linkage. Those skilled in the art will understand that the illustration herein of the bypass valve
42
is by way of generic explanation and example only, and that, within the scope of the invention, various other bypass configurations and arrangements could be used, such as a modular (integral) bypass or an electronically operated bypass, or in some case, no bypass at all.
Referring now primarily to
FIGS. 2 and 3
, the blower
26
includes a housing assembly generally designated
48
, which includes a main housing
50
(shown only fragmentarily in FIG.
3
), which defines the chambers
28
c
and
29
c
. The housing assembly
48
also includes an input housing
52
, also referred to hereinafter as a clutch housing. Disposed axially between the main housing
50
and the clutch housing
52
is a bearing plate
54
through which extends a forward end of a rotor shaft
56
, on which is mounted the rotor
28
.
As is well known to those skilled in the art of superchargers, a timing gear
58
is pressed onto the forward end of the rotor shaft
56
, and in the subject embodiment, the timing gear
58
includes an input hub
60
. Journalled within the forward end (left end in
FIG. 3
) of the input hub
60
is a reduced diameter portion
62
of an input shaft
64
. Disposed about a forward end of the input shaft
64
is an input pulley
66
, by means of which torque is transmitted from the engine crankshaft (not shown) to the input shaft
64
. It should be noted that the input pulley
66
is shown only fragmentarily in FIG.
3
. The input pulley
66
surrounds a reduced diameter portion
68
of the clutch housing
52
, and disposed radially between the input shaft
64
and the portion
68
is a bearing set
70
.
The clutch housing
52
defines a relatively smaller internal diameter
72
, also referred to hereinafter as a cylindrical surface
72
, and a relatively larger internal diameter
74
, also referred to hereinafter as a cylindrical surface
74
. The cylindrical surfaces
72
and
74
comprise a clutch chamber which will hereafter also bear the reference “
74
”. Disposed within the clutch chamber
74
is a clutch assembly, generally designated
75
, including a clutch piston
76
, including a reduced diameter portion
78
which is in sealing engagement with the smaller cylindrical surface
72
, and a larger cylindrical portion
80
which is in sealing engagement with the cylindrical surface
74
.
A splined drive member
82
is in driven engagement with the input shaft
64
by any suitable means, such as a press-fit relationship. Surrounding the drive member
82
is a clutch pack, generally designated
84
, including a set of internally splined clutch disks
86
, which are in splined engagement with the drive member
82
. Interleaved with the disks
86
is a set of externally splined clutch disks
88
, which are in splined engagement with internal splines defined by a cylindrical portion
90
of a clutch housing or cage
92
. The clutch cage
92
also includes a relatively smaller cylindrical portion
94
which is in a splined relationship with the input hub
60
, such that there can be relative axial movement therebetween, for reasons which will become apparent subsequently. Therefore, whenever the clutch pack
84
is engaged, input torque is transmitted from the input pulley
66
through the input shaft
64
to the splined drive member
82
, and from there through the clutch pack
84
to the clutch cage
92
, and then through the timing gear
58
to the rotor shaft
56
.
Disposed about the cylindrical portion
94
, and in pressed fit relationship thereto, is a bearing set
96
, and surrounding the bearing set
96
is a spring seat member
98
(also referred to hereinafter as a release plate), the outer periphery of the member
98
being in engagement with a rearward shoulder surface
100
of the cylindrical portion
80
of the clutch piston
76
. The purpose of the above relationship of the spring seat member
98
and the clutch piston
76
will be described subsequently.
Seated against a forward surface of the bearing plate
54
is a plurality (of which two are shown in
FIG. 3
) of spring support members
102
, each member
102
being surrounded by a coil compression spring
104
, the forward end of each spring
104
being seated against the spring seat member
98
. Disposed axially between the radially extending portion of the clutch housing
52
and the forward surface of the clutch piston
76
is an annular pressure chamber
106
. Whenever relatively high pressure is communicated to the pressure chamber
106
, the clutch piston
76
is moved rearwardly (to the right in
FIG. 3
) to a position in which the springs
104
are sufficiently compressed that the member
98
is disposed in contact with the forward end (left end in
FIG. 3
) of each of the support members
102
. Thus, the members
102
also serve as travel “stops” for the springs
104
and the seat member
98
.
As is used herein, the term “relatively high” pressure will be understood to mean high relative to the low pressure, or sump (reservoir) pressure which would be present in the pressure chamber
106
whenever the chamber
106
is drained, i.e., is communicated to a case drain region, such as that surrounding the timing gear
58
(and the other timing gear, not shown herein). However, it is also one important aspect of the invention that the “relatively high” pressure used to disengage the clutch pack
84
is preferably a pressure of only about 10 to 20 psi. (gauge). As was mentioned in the BACKGROUND OF THE DISCLOSURE, it is desirable to be able to operate the supercharger clutch using only the engine lubrication oil, for which the pressure would typically be about 20 psi. at the “end” of its flow path, which is where the supercharger clutch would be disposed.
When the piston
76
is moved to the right from the position shown in
FIG. 3
, the spring seat member
98
is also moved rearwardly, compressing the springs
104
as mentioned previously. With the springs
104
somewhat compressed, the clutch cage
92
is moved somewhat to the right in
FIG. 3
, and the loading of the clutch pack
84
is relieved sufficiently such that no substantial torque will be transmitted from the input shaft
64
to the clutch cage
92
. In other words, no substantial input torque will be transmitted to the timing gear
58
or to the rotor shaft
56
. Preferably, the unloading of the clutch pack
84
is sufficient to eliminate any “clutch drag”, the presence of which would somewhat diminish the benefit of being able to de-clutch the supercharger.
In order to engage the clutch pack
84
, and therefore, to drive the rotors of the supercharger, it is necessary to reduce the fluid pressure in the pressure chamber
106
from the relatively high pressure to a relatively low pressure (which could be sump or reservoir pressure). In the subject embodiment, the spring rate of the springs
104
has been selected such that, when the pressure in the chamber
106
is reduced to the relatively low pressure, the springs
104
will bias the seat member
98
forwardly (to about the position shown in
FIG. 3
) which, in turn, biases the bearing set
96
and the clutch cage
92
forwardly. Such forward movement of the radially extending wall of the clutch cage
92
will compress the clutch pack
84
against a radially extending lip
108
of the drive member
82
.
Clutch Controls
It will be apparent to those skilled in the art that the time of engagement of the clutch assembly of the present invention is determined indirectly by the net force compressing the clutch pack
84
. The compression force is determined by the fluid pressure in the pressure chamber
106
, as it decreases from the relatively high pressure to a relatively lower pressure. In connection with the development of the present invention, it has been determined that it is an important aspect of the present invention to be able to modulate the rate of engagement of the clutch pack
84
, in accordance with various vehicle and engine operating parameters, i.e., to reduce the pressure in the chamber
106
, to a desired level, and therefore engage the clutch pack more rapidly or more slowly, depending upon various predetermined conditions. For example, when the engine is operating under a “part throttle” condition, it is desirable to achieve a longer time of engagement, whereas when the engine is operating under a “full throttle” condition, it is acceptable to engage the clutch pack more rapidly.
Referring now primarily to
FIG. 4
, there is illustrated a control valve assembly, generally designated
110
, of the type which may be used to control the pressure in the chamber
106
. It will be understood by those skilled in the art, that the invention of this application is not limited to any particular type or configuration of control valve, or to any specific control logic. What is essential to the present invention is that the clutch assembly include some sort of control valving which is capable of modulating the pressure in the chamber
106
between the relatively high and relatively low pressures to achieve engagement and disengagement of the clutch pack
84
within the specified response times, and that the clutch assembly include some sort of control logic which is capable of achieving engagement of the clutch pack
84
at a controllable (modulatable) rate representative of some other predetermined vehicle parameter, such as throttle position.
Disposed in threaded engagement with the clutch housing
52
is a fitting
112
(see also FIG.
2
), which is connected to a source of fluid pressure, such as the engine lubrication fluid, as was described previously. The clutch housing
52
also defines a chamber
114
in which is disposed the control valve assembly
110
. The housing
52
also defines an axial passage
116
communicating with a transverse passage
118
, which is in open communication with the pressure chamber
106
.
The control valve assembly
110
, which will be described only briefly hereinafter, may be of the general type illustrated and described in U.S. Pat. No. 4,947,893, assigned to the assignee of the present invention, and incorporated herein by reference. The control valve assembly
110
includes a valve body
120
and disposed for axial movement therein, a valve spool
122
, the valve spool
122
being shown in
FIG. 4
in a centered (or “neutral” position). The valve spool
122
is biased to the left in
FIG. 4
by a compression spring
124
, and can be moved to the right in
FIG. 4
by means of an electromagnetic coil
126
which, when energized, biases an armature assembly
128
to the right, moving the valve spool
122
to the right also. Disposed at the left end of the valve spool
122
is a pressure feedback chamber
129
which, as is taught in the above-incorporated patent, is in communication with the fluid pressure present in the axial passage
116
. Thus, the valve spool
122
is always being biased toward the right in
FIG. 4
by whatever pressure is present in the pressure chamber
106
.
In operation, with the coil
126
de-energized, the spring
124
biases the valve spool
122
to the left in
FIG. 4
, permitting communication of relatively high pressure from the chamber
114
through the valve assembly
110
to the axial passage
116
, thus pressurizing the chamber
106
, such that the piston
76
moves to the right in
FIG. 3
, disengaging the clutch pack
84
, in the manner described previously. The above-described arrangement whereby the coil
126
is de-energized to disengage the clutch pack
84
is preferred because, in a typical vehicle application, the supercharger is disengaged for a greater part of the total duty cycle than it is engaged. More importantly, it is considered desirable that an electrical failure result in the supercharger clutch being disengaged. After the chamber
106
is pressurized to a relatively high pressure, that same pressure present in the feedback chamber
129
returns the valve spool
122
to the neutral position shown in FIG.
4
.
When it is desired to operate the supercharger, by engaging the clutch pack
84
, an appropriate electrical signal
130
is transmitted to the coil
126
, moving the valve spool
122
to the right of the neutral position shown in
FIG. 4
, thus communicating the passage
116
(and therefore, the chamber
106
) through the valve assembly
110
to a case drain region, illustrated generally as
132
in
FIGS. 3 and 4
. The decreasing pressure in the chamber
106
permits the springs
104
to bias the release plate
98
to the left, to the position shown in
FIG. 3
, as described previously, engaging the clutch pack
84
. The rate of engagement (response time) of the clutch pack is determined by the pressure in the chamber
106
, which in turn is controlled in response to changes in the electrical signal
130
, such that a “soft engagement” may be achieved when that is desirable, or a more rapid engagement may be achieved when that is needed and is acceptable. Those skilled in the art will understand that in most supercharger installations, it is the engagement response time which is more critical, whereas the disengagement response time is typically less critical.
It is one important aspect of the present invention to be able to control the rate of engagement of the clutch pack
84
, in accordance with some particular vehicle parameter, such as throttle position. Therefore, referring now primarily to
FIGS. 5 and 6
, in conjunction with
FIG. 4
, the method of controlling the engagement of the supercharger, including the control logic will be described.
When it is desired to operate the supercharger, by engaging the clutch pack
84
, and the electrical signal
130
is transmitted to the coil
126
, the control logic shown in
FIG. 5
is initiated by proceeding to “Start”. The logic then proceeds to an operation block
141
which reads the position of the throttle pedal which, as is generally well known to those skilled in the art, will be generally representative of the rate of acceleration of the vehicle. The logic then proceeds to a decision block
143
in which the throttle position
141
is compared to a predetermined engagement threshold. Typically, and by way of example only, the threshold utilized in the decision block
143
would be somewhere in the range of about twenty percent to about 30 percent of full throttle. If the throttle position
141
is less than the threshold (“No”), the logic merely loops back, upstream of the operation block
141
. If the throttle position
141
is greater than the threshold (“Yes”), the logic then proceeds to an operation block
145
.
In the operation block
145
, the command signal
130
(I1), the input to the electromagnetic coil
126
, is set equal to one amp (see
FIG. 6
) and the logic timer is started. Those skilled in the art will understand that setting I1 equal to one amp is by way of example only, and is done primarily to be sure that the valve spool
122
does not “hang up”, but is displaced enough that it can thereafter be moved to its desired position, as will be described subsequently. The logic then proceeds to a decision block
147
which interrogates the logic timer, and as long as the time t is not greater than 0.01 seconds (“No”), the logic merely loops back upstream of the decision block
147
. When the time t has exceeded 0.01 seconds (“Yes”), the logic then proceeds to an operation block
149
in which a new command signal
130
(I2) is calculated.
In accordance with one important aspect of the invention, and as is shown in the graph of
FIG. 6
, the current I2 is calculated to correspond, in its steady state condition (after about t equals 0.1 seconds), to correspond to the throttle pedal position, read in operation block
141
. However, as may be seen in
FIG. 6
, before the current I2 achieves its steady state condition, there is first an exponential decay from the initial condition (I1 equals one amp).
To illustrate one aspect of the invention, the graph of
FIG. 6
shows five different values of I2, each corresponding to a different throttle pedal position, the positions being labeled T
1
through T
5
, with the throttle position T
1
representing a position just above the threshold of decision block
143
, then T
2
being a somewhat greater throttle position, etc., all the way up through T
5
which may represent nearly a fall throttle position. As may also be seen in
FIG. 6
, the minimum throttle position T
1
results in the signal I2 being set at approximately 0.5 amps, whereas the highest throttle position T
5
results in the current I2 being set to about 0.9 amps.
Referring again to
FIG. 4
, the greater the magnitude of the current I2, the further to the right will the valve spool
122
be moved. As was described previously, the movement of the valve spool
122
to the right in
FIG. 4
will be a function of the force exerted by the coil
126
, plus the pressure in the feedback chamber
129
, together opposing the force of the biasing spring
124
. As the valve spool
122
is moved to the right, the pressure in the chamber
106
and in the axial passage
116
will be drained to the case drain region
132
. Thus, the pressure in the chamber
106
and in the axial passage
116
will decrease, and there will be a corresponding decrease in the pressure in the feedback chamber
129
, with the result that the valve spool
122
will tend to move back toward the neutral position shown in FIG.
4
. However, in the meantime, the pressure in the chamber
106
will level off at a pressure corresponding to the current I2 which in turn corresponds to one of the throttle positions T
1
through T
5
as shown in FIG.
6
.
Referring again to the logic of
FIG. 5
, after the operation block
149
, the logic next proceeds to a decision block
151
in which the timer is interrogated to see if the time t is greater than 0.45 seconds. If not (“No”) the logic merely loops back upstream of the decision block
151
. As soon as the time t is equal to or greater than 0.45 seconds (“Yes”), the logic proceeds to an operation block
153
in which a new electrical command signal
130
(I3) is generated by merely setting I3 equal to one amp. By transmitting one amp to the coil
126
, the logic ensures that the pressure chamber
106
will be sufficiently drained such that the springs
104
will bias the clutch pack
84
into full engagement, with no substantial opposing force from the piston
76
. Thereafter, the supercharger clutch will operate in its fully engaged condition, such that no slipping occurs within the clutch pack
84
. It should be understood by those skilled in the art that the particular current values shown and described herein are by way of example only, and not by way of limitation. Furthermore, the fact that the currents I1 and I3 both are set to one amp is not significant to the invention, but instead, all that is truly essential to the invention is that I2 be relatively lower, to modulate the engagement, and then I3 be relatively higher, to insure full engagement of the clutch pack
84
.
By way of example only, it was found during the development of the present invention that for the throttle position T
1
(I2 equal 0.5 amps), the result was an engagement time in the range of about 400 to 450 milliseconds whereas, at the other extreme, for the throttle position T
5
(I2 equals 0.9 amps), the engagement time was in the range of about 100 to 150 milliseconds. As was described in the BACKGROUND OF THE DISCLOSURE, it was an important object of the invention to be able to modulate the rate of engagement (engagement time) of the supercharger clutch in response to varying vehicle parameters, such as throttle position.
The invention has been described in great detail in the foregoing specification, and it is believed that various alterations and modifications of the invention will become apparent to those skilled in the art from a reading and understanding of the specification. It is intended that all such alterations and modifications are included in the invention, insofar as they come within the scope of the appended claims.
Claims
- 1. A method of controlling a rotary blower of the backflow or compression type having an input, a housing defining a blower chamber, and a pair of blower rotors disposed in said blower chamber and adapted to be driven by said input, and a wet clutch disposed in series driving relationship between said input and said blower rotors, said wet clutch including spring means biasing said wet clutch toward one of an engaged and a disengaged condition, and a fluid pressure actuated piston having a pressure chamber biasing said wet clutch toward the other of said engaged and said disengaged conditions; said method of controlling characterized by:(a) providing an electrohydraulic valve means operable to communicate said pressure chamber selectively to a source of high pressure and a source of low pressure; (b) generating a command signal operable to bias said electrohydraulic valve means toward a position operable to communicate said pressure chamber to said source of whichever of said high pressure and said low pressure corresponds to said engaged condition; (c) sensing a throttle position representative of change in commanded throttle position for the vehicle engine; (d) modifying said command signal in response to said throttle position whereby a change between said engaged and said disengaged conditions will occur more rapidly for a more rapid change in commanded throttle position.
- 2. A method as claimed in claim 1 characterized by said spring means biasing said wet clutch toward said engaged condition, said fluid pressure actuated piston biasing said wet clutch toward said disengaged condition, and said step of providing said electrohydraulic valve means includes providing said command signal to said valve means to communicate said pressure chamber to said source of low pressure.
- 3. A method as claimed in claim 1 characterized by said step of sensing a throttle position comprises sensing a rate of change of commanded throttle position, and the step of modifying said command signal is performed generally proportionally to said rate of change of said throttle position.
- 4. A method as claimed in claim 2 characterized by said electrohydraulic valve means includes a spring biasing a valve member from its normal, neutral position toward a position communicating said pressure chamber to said source of high pressure, and an electromagnetic coil operable, when energized, to bias said valve member toward a position communicating said pressure chamber to said source of low pressure.
- 5. A method as claimed in claim 4, characterized by said electrohydraulic valve means defining a feedback pressure chamber in communication with a pressure representative of the pressure in said pressure chamber, said feedback pressure chamber being operable to bias said valve member in opposition to the force of said spring whereby, a decreasing pressure in said pressure chamber when said electromagnetic coil is energized will result in said valve member being biased toward said neutral position.
US Referenced Citations (4)