Information
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Patent Grant
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6694933
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Patent Number
6,694,933
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Date Filed
Thursday, September 19, 200221 years ago
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Date Issued
Tuesday, February 24, 200420 years ago
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Inventors
-
Original Assignees
-
Examiners
- Denion; Thomas
- Riddle; Kyle
Agents
- Collier Shannon Scott, PLLC
- Rygiel; Mark W.
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CPC
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US Classifications
Field of Search
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International Classifications
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Abstract
The present invention relates generally to a system and method for actuating one or more valves in an internal combustion engine. In particular, the present invention relates to a system and method that may provide lost motion valve actuation of intake, exhaust, and auxiliary valves in an internal combustion engine.
Description
FIELD OF THE INVENTION
The present invention relates generally to a system and method for actuating one or more valves in an internal combustion engine. In particular, the present invention relates to a system and method that may provide lost motion valve actuation of intake, exhaust, and auxiliary valves in an internal combustion engine.
BACKGROUND OF THE INVENTION
Valve actuation in an internal combustion engine is required in order for the engine to produce positive power, as well as to produce engine braking. During positive power, one or more intake valves may be opened to admit fuel and air into a cylinder for combustion. One or more exhaust valves may be opened to allow combustion gas to escape from the cylinder. Intake, exhaust, and/or auxiliary valves may also be opened during positive power at various times to recirculate gases for improved emissions.
Engine valve actuation also may be used to produce engine braking and exhaust gas recirculation when the engine is not being used to produce positive power. During engine braking, one or more exhaust valves may be selectively opened to convert, at least temporarily, the engine into an air compressor. In doing so, the engine develops retarding horsepower to help slow the vehicle down. This can provide the operator with increased control over the vehicle and substantially reduce wear on the service brakes of the vehicle.
Engine valve(s) may be actuated to produce compression-release braking and/or bleeder braking. The operation of a compression-release type engine brake, or retarder, is well known. As a piston travels upward during its compression stroke, the gases that are trapped in the cylinder are compressed. The compressed gases oppose the upward motion of the piston. During engine braking operation, as the piston approaches the top dead center (TDC), at least one exhaust valve is opened to release the compressed gases in the cylinder to the exhaust manifold, preventing the energy stored in the compressed gases from being returned to the engine on the subsequent expansion down-stroke. In doing so, the engine develops retarding power to help slow the vehicle down. An example of a prior art compression release engine brake is provided by the disclosure of the Cummins, U.S. Pat. No. 3,220,392 (November 1965), which is incorporated herein by reference.
The operation of a bleeder type engine brake has also long been known. During engine braking, in addition to the normal exhaust valve lift, the exhaust valve(s) may be held slightly open continuously throughout the remaining engine cycle (full-cycle bleeder brake) or during a portion of the cycle (partial-cycle bleeder brake). The primary difference between a partial-cycle bleeder brake and a full-cycle bleeder brake is that the former does not have exhaust valve lift during most of the intake stroke.
In many internal combustion engines, the engine cylinder intake and exhaust valves may be opened and closed by fixed profile cams, and more specifically by one or more fixed lobes which may be an integral part of each of the cams. Benefits such as increased performance, improved fuel economy, lower emissions, and better vehicle drivability may be obtained if the intake and exhaust valve timing and lift can be varied. The use of fixed profile cams, however, can make it difficult to adjust the timings and/or amounts of engine valve lift to optimize them for various engine operating conditions, such as different engine speeds.
One method of adjusting valve timing and lift, given a fixed cam profile, has been to provide valve actuation that incorporates a “lost motion” system in the valve train linkage between the valve and the cam. Lost motion is the term applied to a class of technical solutions for modifying the valve motion proscribed by a cam profile with a variable length mechanical, hydraulic, and/or other linkage assembly. In a lost motion system, a cam lobe may provide the “maximum” (longest dwell and greatest lift) motion needed over a full range of engine operating conditions. A variable length system may then be included in the valve train linkage, intermediate of the valve to be opened and the cam providing the maximum motion, to subtract or lose part or all of the motion imparted by the cam to the valve.
This variable length system (or lost motion system) may, when expanded fully, transmit all of the cam motion to the valve(s), and when contracted fully, transmit none or a minimum amount of the cam motion to the valve. An example of such a system and method is provided in Hu, U.S. Pat. Nos. 5,537,976 and 5,680,841, which are assigned to the same assignee as the present application and which are incorporated herein by reference.
In the lost motion system of U.S. Pat. No. 5,680,841, an engine cam shaft may actuate a master piston which displaces fluid from its hydraulic chamber into a hydraulic chamber of a slave piston. The slave piston in turn acts on the engine valve to open it. The lost motion system may include a solenoid valve and/or a check valve in communication with the hydraulic circuit including the chambers of the master and slave pistons. The solenoid valve may be maintained in a closed position in order to retain hydraulic fluid in the circuit when the master piston is acted on by certain of the cam lobes. As long as the solenoid valve remains closed, the slave piston and the engine valve respond directly to the hydraulic fluid displaced by the motion of the master piston, which in turn displaces hydraulic fluid in direct response to the cam lobe acting on it. When the solenoid is opened, the circuit may drain, and part or all of the hydraulic pressure generated by the master piston may be absorbed by the circuit rather than be applied to displace the slave piston, and correspondingly, the engine valve.
Some previous lost motion systems have utilized high speed mechanisms to rapidly vary the length of the lost motion system. By using a high speed mechanism to vary the length of the lost motion system, precise control may be attained over valve actuation, and accordingly optimal valve actuation may be attained for a wide range of engine operating conditions. Systems utilizing high speed control mechanisms, however, can be costly to manufacture and operate.
When a unitary cam lobe is used to impart the valve motion for both an auxiliary valve event (e.g., engine braking) and the main valve event (e.g., main exhaust), there may be increased overlap between the main intake and exhaust events. The use of a unitary lobe for both events means that the relatively large main event lobe motion will be imparted to the valve actuation system. Because there may be little or no lash between the valve actuation system and the engine valve during engine braking, input of the main event motion may produce a greater than desired main exhaust event. The time during the cycle when both intake and exhaust valves are open at the same time may be increased. The longer that both the intake and exhaust valves are open together, the more exhaust manifold pressure is likely to bleed through the open intake valve. This may greatly reduce braking performance. As such, there is often a need for a valve actuation system including a “reset” mechanism, such that, when a unitary cam lobe is used to impart the valve motion, the valve experiences normal lift and closing during engine braking.
The design, size, and configuration of many engines require valve actuation systems to be located relatively remote from the engine valves that they are required to actuate (e.g., on the input side of an engine rocker arm), rather than being located on the valve side of the engine. Production tolerances for components on the input side of an engine rocker arm (e.g., the push tube) are typically much greater than those on the valve side because the manufacturer may anticipate making manual lash adjustments. Incorporating valve actuation systems capable of providing precise lost motion and/or reset functionality in this location may be difficult due to the inherent production tolerances that may exist between the valve actuation system and the valves.
The lost motion systems and methods of the present invention may be particularly useful in engines requiring lost motion valve actuation for positive power, engine braking valve events (such as, for example, compression release and bleeder braking), and/or exhaust gas recirculation valve events. The systems of various embodiments of the present invention may provide a lower cost, production viable lost motion circuit with fixed event timing that requires no high speed electronic controls to operate. In addition, the systems and methods of the present invention may reduce valve overlap during braking and reduce the impact on the valve train.
Additional advantages of embodiments of the invention are set forth, in part, in the description which follows and, in part, will be apparent to one of ordinary skill in the art from the description and/or from the practice of the invention.
SUMMARY OF THE INVENTION
Responsive to the foregoing challenges, Applicant has developed innovative systems and methods for actuating one or more engine valves. In one embodiment, the present invention is an engine valve actuation system comprising: a lost motion subsystem operatively connected to the engine valve; a hydraulic fluid supply in communication with the lost motion subsystem; and means for imparting motion to the lost motion subsystem. The lost motion subsystem may comprise: a housing having an internal bore; a piston assembly slidably disposed in the bore, the piston assembly comprising a master piston and a slave piston; a hydraulic control valve; a solenoid actuated hydraulic fluid valve; a first hydraulic passage connecting the control valve to the piston assembly; a second hydraulic passage connecting the fluid supply to the control valve; and a third hydraulic passage connecting the solenoid valve to the control valve.
In another embodiment, the present invention is a method of actuating an engine valve during first and second operating modes to produce a main event valve actuation and to selectively produce an auxiliary event valve actuation using motion imparted to a lost motion subsystem. The method may comprise the steps of: supplying hydraulic pressure to the lost motion subsystem; during the first operating mode, selectively absorbing at least a portion of the hydraulic pressure applied to the lost motion subsystem so as to selectively lose a portion of the motion imparted thereto; and during the second operating mode, creating a hydraulic lock in the lost motion subsystem to transfer the motion to the engine valve and selectively modifying the manner in which the motion is transferred to the valve from hydraulic means to mechanical means.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated herein by reference, and which constitute a part of this specification, illustrate certain embodiments of the invention and, together with the detailed description, serve to explain the principles of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to assist the understanding of this invention, reference will now be made to the appended drawings, in which like reference numerals refer to like elements. The drawings are exemplary only, and should not be construed as limiting the invention.
FIG. 1
is a block diagram of a valve actuation system according to a first embodiment of the present invention.
FIG. 2
a
is a schematic diagram of a valve actuation system according to a second embodiment of the present invention.
FIG. 2
b
is a schematic diagram of a valve actuation system according to a third embodiment of the present invention.
FIG. 3
is a schematic diagram of a cam having multiple lobes for use in connection with various embodiments of the present invention.
FIG. 4
is a schematic diagram of a master/slave piston assembly according to an embodiment of the present invention.
FIG. 5
is a schematic diagram of a control valve according to an embodiment of the present invention.
FIG. 6
is a schematic diagram of an accumulator according to an embodiment of the present invention.
FIG. 7
is a valve lift profile according to an embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
Reference will now be made in detail to a first embodiment of the system and method of the present invention, an example of which is illustrated in the accompanying drawings. As embodied herein, the present invention includes systems and methods of controlling the actuation of engine valves.
An embodiment of the present invention is shown in
FIG. 1
as valve actuation system
10
. The valve actuation system
10
includes a lost motion subsystem or variable length system
300
which connects a means
100
for imparting motion with one or more engine valves
200
. The motion imparting means
100
provides an input motion to the lost motion system
300
. The lost motion system
300
may be selectively switched between modes of: (1) losing a portion of the motion input by the motion imparting means
100
, and (2) transferring the input motion to the engine valves
200
. In this manner, the motion transferred to the engine valves
200
may be used to produce various engine valve events, such as, but not limited to, main intake, main exhaust, compression release braking, bleeder braking, and/or exhaust gas recirculation. The valve actuation system
10
, including the lost motion system
300
, may be switched between a mode of losing motion and not losing motion in response to a signal or input from a control means
400
. Without limiting the scope of the present invention, the remainder of this detailed description will refer to the mode of not losing motion as engine braking. The engine valves
200
may be exhaust valves, intake valves, and/or auxiliary valves.
The motion imparting means
100
may comprise any combination of cam(s), cam follower(s), push tube(s), and/or rocker arm(s), or their equivalents. The lost motion system
300
may comprise any structure that connects the motion imparting means
100
to the valves
200
and is capable of transmitting motion from the motion imparting means
100
to the valve
200
. In one sense, the lost motion system
300
may be any structure(s) capable of selectively attaining more than one length. The lost motion system
300
may comprise, for example, a mechanical linkage, a hydraulic circuit, a hydro-mechanical linkage, an electromechanical linkage, and/or any other linkage adapted to connect to the motion imparting means
100
and attain more than one operative length. The lost motion system
300
may include means for adjusting the pressure, or amount of fluid in the hydraulic circuit, such as, for example, trigger valve(s), check valve(s), accumulator(s), and/or other devices used to release hydraulic fluid from or add hydraulic fluid to a circuit in the lost motion system
300
. The lost motion system
300
may be located at any point in the valve train connecting the motion imparting means
100
and the valves
200
. In a preferred embodiment, the lost motion system
300
is located on the push tube side of the engine, as described below.
The control means
400
may comprise any electronic and/or mechanical device for communicating with the lost motion system
300
and selectively causing the lost motion system
300
to either lose a portion of the motion input to it, or not lose motion. The control means
400
may include a microprocessor, linked to an appropriate vehicle component(s), to determine and select the appropriate mode of the lost motion system
300
. The vehicle component may include, without limitation, an engine speed sensing means, a clutch position sensing means, a fuel position sensing means, and/or a vehicle speed sensing means. Under prescribed conditions, the control means
400
will produce a signal and transmit the signal to the lost motion system
300
, which will, in turn, switch to the appropriate mode of operation. For example, when the control means
400
determines that engine braking mode is desired, based on a condition, such as, idle fuel, engaged clutch, and/or an engine RPM greater than a certain speed, the control means
400
may produce and transmit a signal to the lost motion system
300
to switch to engine braking mode. It is contemplated that the valve actuation system
10
is designed such that valve actuation may be optimized at one or more engine speeds and engine operating conditions.
Another embodiment of the present invention is shown in
FIG. 2
a
. With reference thereto, the motion imparting means
100
may comprise a cam
110
, and a push tube assembly
125
. The motion imparting means
100
is adapted to act on the lost motion system
300
, as shown in
FIG. 2
a.
The cam
110
may include one or more cam lobes for producing an engine valve event. With reference to
FIG. 3
, the cam lobes may include lobes, such as, for example, a main (exhaust or intake) event lobe
112
, an engine braking lobe
114
, and an EGR lobe
116
. The depictions of the lobes on the cam
110
are intended to be illustrative only, and not limiting. It is appreciated that the number, combination, size, location, and shape of the lobes may vary markedly without departing from the intended scope of the invention. For example, the engine braking lobe
114
may be shaped to produce a bleeder braking event or a compression release braking event.
The lost motion system
300
may include a housing
302
, a master piston assembly
130
, a slave piston assembly
140
, a rocker
120
, a hydraulic circuit
310
formed within the housing
302
, a control valve
320
, an accumulator
330
, and a solenoid actuated valve
340
.
The master/slave piston assembly
130
/
140
connects the cam
110
with the rocker
120
. One embodiment of the master/slave piston assembly
130
/
140
of the present invention is shown in FIG.
4
. The slave piston assembly
140
may be slidably disposed in a bore formed in the housing
302
such that it may slide back and forth in the bore while maintaining a hydraulic seal with the housing
302
. The master piston assembly
130
is adapted to slide relative to the bore, while at the same time forming a seal with the slave piston assembly
140
. In the embodiment shown in
FIGS. 2
a
and
4
, one end of the master piston assembly
130
may be in contact with the push tube
125
to receive the motion from the cam
110
. The push tube
125
may include a cam follower, such as, for example, a roller
126
, for contacting the surface of the cam
110
. Alternatively, as shown in
FIG. 2
b
, the valve actuation system
10
may operate without the push tube
125
, whereby the cam
110
acts directly on the master piston assembly
130
. One end of the slave piston assembly
140
may be in contact with a second end
124
of the rocker
120
.
The master/slave piston assembly
130
/
140
receives hydraulic fluid through a fill passage
311
. A fill hole
141
for communicating with the fill passage
311
may be formed in the slave piston assembly
140
. When the roller
126
is on the base circle of the cam
110
, the master piston assembly
130
is at its lowest position. When no hydraulic fluid is provided between the master piston assembly
130
and the slave piston assembly
140
, the master/slave piston assembly is fully collapsed, creating a mechanical link between the master piston assembly
130
and the slave piston assembly
140
. The fill passage
311
may be positioned such that, when the roller
126
is on the base circle of the cam
110
, as shown in
FIG. 4
, hydraulic fluid may be selectively supplied to the master/slave piston assembly to create a variable volume gap
313
between the master piston assembly
130
and the slave piston assembly
140
. When hydraulic fluid is provided between the master piston assembly
130
and the slave piston assembly
140
, the gap
313
has a variable height, s. During positive power operation, fluid may be permitted to pump in and out of the gap
313
. This may cushion the motion of the master/slave piston assembly and reduce the overall impact on the valve train. When no hydraulic fluid is in the master/slave piston assembly, the assembly is fully collapsed, and the gap
313
is eliminated (solid condition). This solid condition may be used for cold engine starting when there is not fluid in the master/slave piston assembly
130
/
140
and for control of valve actuation during positive power.
The height, s, of the gap
313
when the roller is on the base circle of the cam
110
may vary depending on the specification and requirements of the engine and the system
10
. In a preferred embodiment, the maximum height of the gap
313
is greater than the magnitude of the engine braking lobe
114
on the cam
110
plus an allowance for system lash and tolerances, but sized such that the full motion of the main event lobe
112
is transferred to the engine valves
200
when the master/slave piston assembly is fully collapsed. The maximum height of the gap
313
may be adjusted by an adjustment means
123
, which may adjust the position of the second end
124
of the rocker
120
relative to the slave piston assembly
140
.
With continued reference to
FIG. 2
a
, the rocker
120
is adapted to actuate the valves
200
. The rocker
120
may include a central opening
121
for receipt of a rocker shaft, a first end
122
adapted to contact a valve bridge
250
, and a second end
124
adapted to contact the slave piston assembly
140
. The rocker
120
is adapted to pivot back and forth about the central opening
121
. The first end
122
and the second end
124
may be adapted to allow some pivot motion as the rocker arm
120
contacts the valve bridge
250
and the slave piston assembly
140
. A system lash (not shown) may exist between the first end
122
and the valve bridge
250
.
As the cam
110
rotates, the roller
126
follows the surface of the cam
110
, causing the push tube
125
to displace the master piston assembly
130
. Depending on the mode of operation, the hydraulic pressure generated by the master piston assembly
130
may, in turn, displace the slave piston assembly
140
, causing the rocker
120
to rotate. As the rocker
120
rotates, the rocker
120
is adapted to actuate the one or more engine valves
200
.
The hydraulic circuit
310
may comprise any combination of hydraulic passages adapted to achieve the objects of the system
10
. In one embodiment, as shown in
FIG. 2
a
, the hydraulic circuit comprises a constant supply passage
312
connecting the master/slave piston assembly
130
/
140
to the hydraulic fluid supply source
500
, a fill passage
311
connecting the master/slave piston assembly
130
/
140
to the control valve
320
for providing hydraulic fluid to the master/slave piston assembly
130
/
140
, and a low-pressure passage
314
connecting the control valve
320
to the solenoid valve
340
for switching the system to a braking mode of operation. In a preferred embodiment, as shown in
FIG. 2
a
, the low-pressure passage
314
is isolated from the constant supply passage
312
. This configuration permits the supply of hydraulic fluid to the master/slave piston assembly
130
/
140
during positive power operation for lubrication and damping while permitting the engine braking mode to be disengaged.
The lost motion system
300
may further comprise means
315
for resetting the length of the lost motion system
300
such that during braking, the engine valves
200
may experience normal valve lift and closing. The reset means
315
is adapted to selectively release fluid from the master/slave piston assembly
130
/
140
to reset the length of the lost motion system
300
. In one embodiment, as shown in
FIG. 2
a
, the reset means comprises a hydraulic passage
315
formed in the housing
302
. During engine braking, as the roller
126
approaches the main event lobe
112
on the cam
110
, the high-pressure hydraulic fluid in the gap
313
between the master piston assembly
130
and the slave piston assembly
140
is released through the reset means
315
, causing the master/slave piston assembly
130
/
140
to collapse (solid condition). The full motion of the main event lobe
112
may then be transferred to the engine valves
200
through the mechanical link between the slave piston assembly
140
and the master piston assembly
130
. As such, the reset means
315
may modify the manner in which motion is transferred to the valves
200
from a hydraulic linkage to a mechanical linkage.
In one embodiment, the hydraulic fluid is released to the constant supply passage
312
, allowing for quicker refill of the master/slave piston assembly
130
/
140
during the next engine cycle. It is appreciated, however, that the hydraulic fluid may be released to other parts of the engine, such as, for example, the engine overhead, and/or an oil supply source
500
.
During engine braking operation, the system
10
may produce a valve lift profile
210
having an additional lift because the lash in the system may be reduced or fully taken up. As shown in
FIG. 7
, the release of the hydraulic fluid through the reset means
315
allows the master/slave piston assembly to collapse and the engine valves
200
to follow the remainder of the standard engine valve event, such as, for example, the main exhaust event.
FIG. 7
illustrates the cam profile
111
, the valve lift profile
210
, including the main exhaust event
220
and main intake event
230
profiles, according to one embodiment of the present invention.
The reset means
315
may be sized and positioned such that the reset occurs at any point during the modified valve profile
210
. For example, the reset may occur earlier on the main exhaust event
220
. The reset means
315
may be positioned based on factors, such as, for example, the desired valve velocity during the reset event, the desired valve acceleration during the reset event, design and production tolerances, and/or other design considerations. Preferably, the reset means
315
is positioned such that the reset occurs when the engine valves
200
have a reduced velocity and acceleration.
The control valve
320
may be disposed in a bore formed in the housing
302
. The control valve
320
is adapted to control the flow of hydraulic fluid to the master/slave piston assembly. In one embodiment of the present invention, as shown in
FIG. 5
, the control valve
320
includes a check valve assembly
3200
and a control pin assembly
3210
. The check valve assembly
3200
may comprise a ball
3201
in contact with a spring
3202
. The spring
3202
is in contact with a screw assembly
3203
, which secures the check valve
3200
to the housing
302
. The control pin assembly
3210
may comprise a base
3215
secured to the housing
302
, a control piston
3213
, and a spring
3214
having a first end in contact with the base
3215
and a second end in contact with the control piston
3213
. The control pin assembly
3210
may further comprise a pin
3211
having a first end in contact with the control piston
3213
and a second end in contact with the ball
3201
. The pin
3211
is free to slide within a pin guide
3212
.
The spring
3214
is biased such that, absent fluid pressure from the low-pressure supply passage
314
, the pin
3211
is forced against the ball
3201
by the control piston
3214
, keeping the ball
3201
off its seat (pin guide)
3212
. When fluid pressure is supplied to the low-pressure supply passage
314
, for example to initiate engine braking, the fluid pressure acts on the control piston
3213
and against the bias of the spring
3214
. This, in turn, causes downward translation of the pin
3211
within the pin guide
3212
and seating of the ball
3201
on its seat (pin guide)
3212
. At this point, the ball
3201
prevents backward fluid flow to the constant supply passage
312
such that fluid is trapped in the fill passage
311
.
The accumulator
330
is located in a bore formed in the housing
302
, and is adapted to absorb motion transferred by the motion imparting means
100
. In one embodiment of the present invention, as shown in
FIG. 6
, the accumulator
330
may comprise an accumulator piston
332
, and a spring
334
having a first end in contact with a base
336
and a second end in contact with the accumulator piston
332
. The accumulator piston
332
is adapted to slide within its bore in the housing
302
. Until braking is initiated, the accumulator
330
is in full communication with the master/slave piston assembly through the constant supply passage
312
and the fill passage
311
. This allows hydraulic fluid in the fill passage
311
and the constant supply passage
312
to be pumped back and forth between the master/slave piston assembly
130
/
140
and the accumulator
330
, thereby causing selected valve events on the cam
110
, or portions thereof, to be lost.
In one embodiment of the present invention, as shown in
FIG. 6
, the accumulator
330
further includes a bleed hole
338
formed in the accumulator piston
332
. The bleed hole
338
permits hydraulic fluid to slowly leak from the constant supply passage
312
to an oil supply source
500
, such as, for example, a sump. The slow leakage of hydraulic fluid from the valve actuation system
10
may be steadily replenished by cooler hydraulic fluid from a localized low pressure source of hydraulic fluid in communication with the hydraulic circuit
310
. This cooling effect may prevent the valve actuation system
10
from exceeding temperature limits. The local source of hydraulic fluid may communicate with the hydraulic circuit
310
through a check valve
350
. This local source of hydraulic fluid could also be used to charge the hydraulic circuit
310
with fluid upon cold start. It is appreciated that this local reservoir of hydraulic fluid may be integrated into the housing
302
.
The lost motion system
300
may include a solenoid valve
340
. The solenoid valve
340
may include an internal plunger (not shown) that is spring biased into a closed or opened position. The bias of the spring determines whether the solenoid valve
340
is normally open, or normally closed. Embodiments of the present invention may use either a normally open or a normally closed solenoid valve
340
. If the solenoid valve
340
is normally closed, for example, it will prevent the release of hydraulic fluid to the low-pressure passage
314
until it is activated by the control means
400
and opened. In a preferred embodiment, the solenoid valve
340
is a low-speed valve.
With reference to
FIG. 2
a
, operation of an embodiment of the system
10
during lost motion mode (e.g., non-braking) will now be described. Hydraulic fluid from the supply source
500
enters the hydraulic circuit
310
through the check valve
350
and fills the constant supply passage
312
. The solenoid valve
340
remains closed, preventing hydraulic fluid supply to the low-pressure passage
314
. The ball
3201
remains unseated by the pin
3211
, allowing hydraulic fluid to flow from the constant supply passage
312
to the fill passage
311
. Until the engine braking mode is initiated, the fill passage
311
remains in communication with the constant supply passage
312
. This permits hydraulic fluid to be pumped back and forth between the master/slave piston assembly
130
/
140
and the accumulator
330
. As the cam
110
rotates, the hydraulic pressure generated by the upward translation of the master piston assembly
130
may be absorbed by the accumulator
330
without transferring the motion of the engine braking lobe
114
to the slave piston assembly
140
, the rocker
120
, and, ultimately the valves
200
. As the cam
110
approaches the main event lobe
112
, the remaining fluid in the master/slave piston assembly
130
/
140
is pumped out and the master piston assembly
130
comes into contact with the slave piston assembly
140
, forming a mechanical link. The full motion of the main event lobe
112
is then transferred to the engine valves
200
.
When motion transfer is required, the control means
400
transmits a signal to the trigger valve
340
, causing it to open and hydraulic fluid to fill the low-pressure passage
314
. The pressure in the passage
314
displaces the control piston
3213
, causing the downward translation of the pin
3211
and the seating of the ball
3201
. At this point, the ball
3201
seals the constant supply passage
312
such that fluid is trapped in the fill passage
311
. When the cam
110
is on the base circle, the slave piston assembly
140
blocks the reset passage
315
. This prevents hydraulic fluid from releasing from the master/slave piston assembly. The master/slave piston assembly
130
/
140
is now hydraulically locked and the motion from the engine braking lobe
114
is transferred to the valves
200
. As the cam
110
continues to rotate, approaching the main exhaust lobe
112
, the slave piston assembly
140
is positioned such that the reset passage
315
is exposed. This allows hydraulic fluid in the master/slave piston assembly
130
/
140
to be pumped back to the constant supply passage
312
, or elsewhere, as discussed above, and the master/slave piston assembly to collapse. The collapsing of the master/slave piston assembly
130
/
140
allows the valves
200
to follow the remainder of the standard main event, without any increase in overall valve lift or change to the exhaust valve closing. When the cam
110
returns to base circle, the master/slave piston assembly refills with hydraulic fluid. If refill or make-up hydraulic fluid is required by the master/slave piston assembly, the pressure in the fill passage
311
will be lower than the pressure in the constant supply passage
312
. The ball
3201
will be unseated due to the pressure differential and hydraulic fluid will be permitted into the fill passage
311
and the master/slave piston assembly. The ball
3201
will reseat once the fill passage
311
and the master/slave piston assembly are full, or once the pressure in the fill passage
311
is greater than the pressure in the constant supply passage
312
.
When engine braking is no longer required, the trigger valve
340
receives a signal from the control means
400
to turn off and close. The hydraulic fluid in the low-pressure. passage
314
is dumped, causing the control piston
3213
to return to its original position. This allows the system
10
to return to lost motion mode (e.g., positive power operation).
It will be apparent to those skilled in the art that variations and modifications of the present invention can be made without departing from the scope or spirit of the invention. For example, the system may be adapted to actuate a single engine valve without use of the valve bridge
250
. The location of the reset on the valve profile may vary by modifying the size and/or position of the reset means
315
. In addition, the solenoid valve
340
may be a high-pressure solenoid valve, which would allow several other components to be removed from the system. Thus, it is intended that the present invention cover all such modifications and variations of the invention, provided they come within the scope of the appended claims and their equivalents.
Claims
- 1. In an internal combustion engine, a system for actuating one or more engine valves, said system comprising:a lost motion subsystem operatively connected to the engine valve; a hydraulic fluid supply in communication with said lost motion subsystem; and means for imparting motion to said lost motion subsystem, wherein said lost motion subsystem comprises: a housing having an internal bore; a piston assembly slidably disposed in the bore, said piston assembly comprising a master piston and a slave piston; a hydraulic control valve; a solenoid actuated hydraulic fluid valve; a first hydraulic passage connecting said control valve to said piston assembly; a second hydraulic passage connecting said fluid supply to said control valve; and a third hydraulic passage connecting said solenoid valve to said control valve.
- 2. The system of claim 1, wherein said control valve comprises:a check valve assembly disposed between said first hydraulic passage and said second hydraulic passage; and a control pin assembly disposed between said check valve assembly and said second hydraulic passage.
- 3. The system of claim 2, wherein said check valve assembly further comprises:a screw assembly adapted to secure said check valve assembly to said housing; a check valve spring in contact with said screw assembly; and a ball in contact with said check valve spring.
- 4. The system of claim 3, wherein said control pin assembly further comprises:a base secured to said housing; a control piston; a piston spring having a first end in contact with said base and a second end in contact with said control piston; a pin slidably disposed in a pin guide, said pin having a first end in contact with said control piston and a second end in contact with said ball.
- 5. The system of claim 1, further comprising a fluid release passage formed within said housing in selective communication with said piston assembly.
- 6. The system of claim 5, said release passage connecting said piston assembly to said second hydraulic passage.
- 7. The system of claim 1, wherein said motion imparting means further comprises:a cam having a plurality of lobes for producing at least one main event valve actuation and at least one auxiliary event valve actuation; and a push tube having a first end in contact with said cam and a second end in contact with the master piston.
- 8. The system of claim 1, wherein said lost motion subsystem further comprises:a valve bridge in contact with the engine valve; and a rocker having a first end in contact with said piston assembly and a second end adapted to contact said valve bridge.
- 9. The system of claim 1, wherein said lost motion subsystem further comprises an accumulator in communication with said second hydraulic passage.
- 10. The system of claim 9, wherein said accumulator comprises:a base secured to said housing; an accumulator piston slidably disposed in a bore formed in said housing; and a spring having a first end in contact with said base and a second end in contact with said accumulator piston.
- 11. The system of claim 10, further comprising a bleed hole formed in said accumulator piston adapted to permit fluid leakage from said second hydraulic passage to said fluid supply.
- 12. The system of claim 1, wherein said solenoid valve comprises a low speed solenoid valve.
- 13. The system of claim 1, further comprising a controller in communication with said lost motion subsystem adapted to selectively switch said lost motion subsystem between a first operating mode and a second operating mode.
- 14. In an internal combustion engine having an engine rocker arm, a hydraulic passage, and a control valve having a check valve assembly and a control pin assembly disposed between the check valve assembly and the hydraulic passage, a method of actuating an engine valve during first and second operating modes to produce a main event valve actuation and to selectively produce an auxiliary event valve actuation using motion imparted to a lost motion subsystem, said method comprising the steps of:supplying hydraulic pressure to the lost motion subsystem; during the first operating mode, selectively absorbing at least a portion of the hydraulic pressure applied to the lost motion subsystem so as to selectively lose a portion of the motion imparted thereto; and during the second operating mode, providing low-pressure hydraulic fluid to the control valve, imparting motion to the rocker arm through a hydraulic lock in the lost motion subsystem and selectively resetting the length of the lost motion subsystem.
- 15. In an internal combustion engine, an engine valve actuation system adapted to switch between first and second operating modes for providing main event valve actuations and selectively providing auxiliary event valve actuations, said system comprising:a housing having an internal bore; a piston assembly slidably disposed in the bore, said piston assembly comprising a master piston and a slave piston; means for imparting motion to said piston assembly; means for controlling the supply of hydraulic fluid to the piston assembly; a first passage connecting said control means to said piston assembly for providing hydraulic fluid to the piston assembly during the first and second operating modes; a second passage connecting the control means to a supply source for receiving a constant supply of hydraulic fluid; and a third passage connected to said control means for providing low-pressure hydraulic fluid to said control means to switch to the second operating mode.
- 16. The system of claim 15, wherein said motion imparting means comprises a cam in contact with said piston assembly, said cam having a plurality of lobes for producing the main event valve actuation and the auxiliary event valve actuation.
- 17. The system of claim 15, wherein said motion imparting means comprises:a cam having a plurality of lobes for producing the main event valve actuation and the auxiliary event valve actuation; and a push tube having a first end in contact with said cam and a second end in contact with the master piston.
- 18. The system of claim 15, further comprising means for releasing hydraulic fluid from said piston assembly during said second operating mode.
- 19. The system of claim 18, wherein said fluid release means comprises a fluid release passage formed within said housing.
- 20. The system of claim 19, wherein said fluid release means is adapted to release fluid from said piston assembly to said second passage.
- 21. A system for actuating one or more engine valves adapted to switch between a first operating mode for providing a main event valve actuation and a second operating mode for selectively providing an auxiliary event valve actuation, said system comprising:a housing having an internal bore; a piston assembly slidably disposed in the bore, said piston assembly comprising a master piston and a slave piston; means for imparting motion to said piston assembly; a control valve; and a hydraulic passage connected to said control valve for providing low-pressure hydraulic fluid to the control valve and enabling the second operating mode, wherein said control valve comprises: a check valve assembly; and a control pin assembly disposed between said check valve assembly and said hydraulic passage.
- 22. The system of claim 21, further comprising means for releasing hydraulic fluid from said piston assembly during the second operating mode.
- 23. The system of claim 21, further comprising a solenoid actuated hydraulic fluid valve in communication with said hydraulic passage.
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Number |
Name |
Date |
Kind |
5829397 |
Vorih et al. |
Nov 1998 |
A |
5996550 |
Israel et al. |
Dec 1999 |
A |
6257183 |
Vorih et al. |
Jul 2001 |
B1 |