Valve control apparatus and method

A valve control apparatus particularly suited for a diesel engine brake. There is an hydraulic actuator having a piston which contacts the valve stem of an exhaust valve. The actuator is independent of the exhaust valve opening mechanism. There is a device, such as an electromagnetically activated valve, which can releasably shut off a flow of fluid from the hydraulic actuator after the exhaust valve is opened by the exhaust valve opening mechanism. The exhaust valve is prevented from closing until a flow of fluid from the hydraulic cylinder is permitted just before top dead center of the compression stroke.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to valve control apparatuses for engines and to 
diesel engine brakes. 
2. Description of Related Art 
Internal combustion engines conventionally have at least one exhaust valve 
and at least one intake valve per cylinder. The opening and closing of the 
valves is governed by a camshaft which rotates at one half engine speed. 
In most engines the timing of valve opening and closing cannot be 
regulated and occurs at fixed points on the engine cycle. 
Devices have however been developed to alter valve timing, for example as 
disclosed in U.S. Pat. No. 4,870,930 to Yagi. Here an electromagnetic 
solenoid operates on a valve stem to hold the valve open longer than 
normal. 
In U.S. Pat. No. 4,662,332 to Bergmann, an engine brake operates by holding 
valves open during braking with hydraulic actuators. The device requires 
pistons large enough to hold the valves open with available oil pressure 
used as an hydraulic fluid. The device also uses an exhaust restrictor to 
increase the braking effect. 
In U.S. Pat. No. 4,466,390 to Babitzka, a fluid column is interposed 
between the cam and the valve. Valve timing can be regulated by trapping 
fluid in the column or allowing it to drain. The complicated arrangement 
is not well adapted for retrofitting existing engines. 
In some engine applications the force available from an electromagnetic 
device, as disclosed in the Yagi patent, may not be sufficient to hold the 
valve open. Also Yagi discloses holding the valve open only a relatively 
brief period on the exhaust stroke and does not conceive of a device where 
the holding open of the exhaust valve can be utilized for engine braking 
purposes. 
It may be desirable to retrofit engines with valve control apparatuses, for 
example when adapted for use as a diesel engine brake. Devices such as in 
the patent to Babitzka are not suitable, as discussed. 
SUMMARY OF THE INVENTION 
This invention addresses the problem of providing a valve control apparatus 
suitable for retrofitting engines, and especially for use as an engine 
brake, by providing an apparatus for a cylinder of the engine having an 
exhaust valve with a valve stem and a valve opening mechanism. The 
apparatus includes means for selectively holding the exhaust valve open 
after the exhaust valve is opened by the exhaust valve opening mechanism. 
The means includes an hydraulic actuator having an hydraulic cylinder and 
a piston reciprocally positioned in the hydraulic cylinder. There is means 
for operatively contacting the valve stem with the piston without 
interfering with normal operation of the valve opening mechanism. There is 
means for releasably shutting off a flow of fluid from the hydraulic 
cylinder, whereby, when the exhaust valve is open, and the piston contacts 
the valve stem, the exhaust valve is prevented from closing until the flow 
of fluid from the hydraulic cylinder is allowed. 
The invention also provides a combination of an engine braking apparatus 
and a diesel engine. The apparatus includes means for selectively 
preventing complete closing of each exhaust valve by the valve spring, 
after each exhaust valve is opened on the exhaust stroke of its engine 
cylinder, until near top dead center of the compression stroke. The 
exhaust valve is released when its engine cylinder is near top dead center 
of its compression stroke so each exhaust valve is then closed by its 
valve spring. 
The invention also provides a method for braking an engine having a 
plurality of engine cylinders, each said cylinder having an exhaust valve, 
each said exhaust valve having an exhaust valve opening mechanism, an 
exhaust valve spring and an hydraulic actuator having a hydraulic cylinder 
with a piston operatively biased against said each exhaust valve. The 
method comprises the steps of opening each said exhaust valve with the 
exhaust valve opening mechanism; shutting off a flow of hydraulic fluid 
from each said hydraulic cylinder so the piston holds said each exhaust 
valve cracked open; and permitting a flow of hydraulic fluid from the 
hydraulic cylinder near top dead center of each compression stroke of said 
each cylinder so said each exhaust valve is closed by said exhaust valve 
spring. 
In one embodiment, the exhaust valve of each engine cylinder and an exhaust 
valve of a second engine cylinder communicate with a common exhaust 
outlet. There is a selectively operable exhaust restrictor in the exhaust 
outlet. The second engine cylinder is on the intake stroke when said each 
cylinder is near top dead center of the compression stroke. The exhaust 
restrictor in one example of the invention restricts the exhaust gases 
sufficiently to force exhaust gases into the second cylinder past its 
exhaust valve when said each cylinder is near top dead center of the 
compression stroke. 
The invention provides several advantages over the prior art. Firstly, it 
is well adapted for retrofitting standard engines because the hydraulic 
actuator acts independently of the camshaft and is not interposed between 
the camshaft and the valve stem as in some prior art. Secondly, the 
electromagnetic actuator can be relatively small because it only needs to 
create enough force to shut off the flow of hydraulic fluid from the 
hydraulic actuator, not the much greater force required to actually hold 
the exhaust valve open directly as in the patent to Yagi. Also the 
hydraulic actuator itself can have a much smaller capacity than in 
Bergmann, for example, because it need not create a force equal to the 
force of the valve spring and compressed gases in the cylinder to hold the 
valve open. 
The invention provides a compression-release type brake for a diesel engine 
which does not require a specially timed actuator, such as a push tube for 
a fuel injector. At the same time it provides better engine braking in 
some cases than brakes where the exhaust valve remains cracked open 
throughout all engine cycles.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1a, this shows a fragment of a diesel engine, shown 
generally at 10, including a portion of its cylinder head 12 and an 
exhaust valve 14 of one engine cylinder 13 having a piston 17. The exhaust 
valve is opened on a cyclic basis in the conventional manner by a camshaft 
which depresses valve stem 16 of the valve against the force of the valve 
spring 18. The camshaft acts on the valve through a conventional push tube 
and rocker arm arrangement. 
A valve control apparatus is shown generally at 20. In this example the 
apparatus is a compression release brake and has housing 22, shown in 
fragment, which is mounted on the cylinder head as is common for 
compression release brakes. 
The housing includes an hydraulic actuator 24, additional actuators being 
provided for exhaust valves of other engine cylinders. The actuator 
includes a piston 26 which is reciprocally positioned in hydraulic 
cylinder 28. The piston has a bottom end 30 which contacts valve stem 16. 
For simplicity the conventional valve opening mechanism of the engine is 
omitted in FIG. 1a, 1b, 2 and 3. FIG. 4 however, where like parts have 
like numbers with ".4" and ".5" added, shows how piston 26.4 operates 
independently of the conventional valve opening mechanism 27 of the engine 
which includes rocker arm 29. In this example the piston has a bifurcated 
lower portion 31 which contacts crosshead 33 which in turn contacts two 
exhaust valves 14.4 and 14.5. Other known arrangements may be used for 
other configurations of valves. The bifurcated lower portion of the piston 
straddles the rocker arm and so does not interfere with its normal 
operation. 
There is a return coil spring 32 located in a cylindrical recess 34 within 
the piston as seen in FIG. 1a. A vertically elongated slot 36 extends 
diametrically through the piston. A pin 38 extends through the slot and is 
fixedly secured to the housing 22. This pin serves to limit travel of the 
piston towards the exhaust valve while the spring resiliently biases the 
piston away from the valve. 
A conduit 40 extends through the housing to hydraulic cylinder 28 and is 
connected to oil pump 41 of the lubricating oil lines 43 of the engine so 
the pressurized oil acts as hydraulic fluid for cylinder 28. 
A needle valve 42 is slidably received in a bore 44 through the housing and 
has a pointed end 46 capable of sealingly engaging valve seat 48 between 
conduit 40 and cylinder 28 and therefore can serve as means for releasably 
shutting off a flow of fluid from the cylinder 28. 
A disc 50, of steel or other magnetic material, is connected to the top of 
the needle valve. An electromagnetic actuator or solenoid 52 is located 
between the disc and the housing. A coil spring 54, located between the 
disc and the housing, biases the needle valve away from its seat 48 as 
shown. 
A control unit 56 supplies electrical current to solenoid 52 when it is 
desired to keep valve 14 open beyond its normal timed closing. 
In operation, when employed as a compression release brake, control unit 56 
supplies current to solenoid 52 during the exhaust stroke of cylinder 13. 
The valve 14 is open at this time. The solenoid attracts disc 50 
downwards, thus pressing the needle valve against its seat 48 and shutting 
off the flow of oil from cylinder 28 to conduit 40. The maximum downward 
movement of piston 26, which occurs when pin 38 contacts the top of slot 
36, is such that the valve is kept cracked open a relatively small 
distance compared to its normal maximum opening. 
Current is supplied to the solenoid 52 throughout the intake stroke of 
cylinder 13 and throughout its compression stroke so piston 26 holds valve 
14 open past the exhaust stroke until the piston 17 is near top dead 
center of the compression stroke. At that point control unit 56 cuts off 
electrical current to solenoid 52. Spring 54 then acts to raise needle 
valve 42 off its seat 48 and thus allow oil to exit from cylinder 28 
through conduit 40. This permits valve spring 18 to move piston 26 
upwards, away from the valve 14 and closes the valve. 
FIG. 1b illustrates an alternative embodiment of the invention and is a 
continuation of FIG. 1a. In this example valve 14 and a second exhaust 
valve 58 have exhaust ports 60 and 62 respectively which are connected to 
a common exhaust conduit 64. One common arrangement in an eight cylinder 
engine is to provide two banks of four cylinders each. Each bank of 
cylinders has a common exhaust outlet. Piston 61 of cylinder 59 is on the 
intake stroke when cylinder 13 approaches top dead center of its 
compression stroke. 
There is an adjustable exhaust gas restrictor 66, in the form of a 
butterfly valve in this example, in exhaust conduit 64. The restrictor is 
closed during engine brake operation to partially block conduit 64 and 
thus increase the braking effect as the exhaust gases are forced past the 
restrictor. In this example the restrictor creates a back pressure of 
exhaust gases great enough to force open valve 58 when the cylinder 13 is 
near top dead center of its compression stroke. At that time a pressure 
pulse is created in the exhaust system from cracked open valve 14. The 
pulse is transmitted to valve 58 and opens the valve beyond its normally 
cracked-open position and forces exhaust gases into its cylinder 59. This 
increases the charge in the cylinder and thereby the braking effect on its 
compression stroke. Another cylinder creates the same effect for cylinder 
13 and other cylinders of the engine. 
Referring to FIG. 2, this is another embodiment of the invention with 
provision for adjusting the amount the valve is cracked open. Parts 
corresponding to those in FIG. 1 have the same number with the addition of 
"0.1". The structure and operation are similar except as described below. 
In this example a valve member 42.1 replaces the needle valve of the first 
two embodiments. Its end 46.1 is blunt and is adapted to sealingly contact 
the top of the piston 26.1 to block a flow of oil from conduit 70 which 
extends axially from the top of piston 26.1. Valve member 42.1 fits 
slidingly through central bore 72 in an adjustment screw 74 which 
threadedly engages a complementary threaded opening 76 in housing 22.1. 
Solenoid 52.1 is mounted on top of adjustment screw 74. The piston 26.1 
also has diametrical conduit 78 communicating with conduit 70 which, in 
the illustrated position of the piston, is aligned with an oil drain 80 in 
the housing. In this embodiment pressurized oil is supplied from the 
engine oil pump through conduit 40.1. Conduit 40.1 has a check valve 82 
therein which blocks a flow of oil away from cylinder 28.1. 
When operated by means of control unit 56.1, current is supplied to 
solenoid 52.1 during the exhaust stroke of the engine cylinder associated 
with valve 14.1. The distal end 46.1 of member 42.1 projects into cylinder 
28.1 towards piston 26.1 and is adjustable by rotating the screw 74. The 
adjustment is made such that, when moved downwardly by a solenoid 52.1, 
the member 42.1 maintains piston 26.1 at a distance which is the sum of 
(1) the lash (freeplay) between piston 26.1 and the valve stem when the 
valve is closed and (2) the distance the valve is to be cracked open. Oil 
from conduit 40.1 fills cylinder 28.1 above piston 26.1 and moves the 
piston towards valve 14.1. If the top of the piston moves below end 46.1 
of member 42.1, then oil from the cylinder 28.1 drains through conduits 70 
and 78 to drain 80. 
When the exhaust stroke is finished, valve 14.1 attempts to close under the 
action of spring 18.1. However, once the top of piston 26.1 contacts end 
46.1 of the member 42.1, further upward movement is prevented by the oil 
trapped in cylinder 28.1 between the top of piston 26.1 and check valve 
82. The solenoid 52.1 is deactivated by control unit 56.1 near top dead 
center of the compression stroke of the relevant engine cylinder. Spring 
84 then moves member 42.1 away from piston 26.1, allowing oil in cylinder 
28.1 to flow out through bores 70 and 78 and drain 80. This allows piston 
26.1 to move up and the valve 14.1 to close. 
FIG. 3 shows a fourth embodiment of the invention where like parts have 
like numbers to FIG. 1 and FIG. 2 with the additional designation "0.2". 
This example functions generally similar to that of FIG. 2 except that the 
adjustment screw is separated from the solenoid 52.2. The solenoid is 
displaced to one side and retains a needle valve 42.2 with a seat 48.2 
similar to FIG. 1. 
Adjustment screw 74.2 has an interior hollow 92 with a coil spring 93 
therein. A moveable finger 90 projects from the interior of the screw and 
has an enlarged top 94 which is retained within the screw by annular 
flange 96 thereof. Spring 93 biases the finger downwardly. 
As with the embodiment of FIG. 2, the screw is adjusted so that the finger 
contacts the top of piston 26.2 until the piston has moved down a distance 
sufficient to take up lash in the system and keep the valve cracked open 
the desired amount. It works similarly as well except the oil is trapped 
in the cylinder 28.2 by the finger 90 contacting the top of conduit 70.2 
and by needle valve 42.2 contacting its seat 48.2. When the piston of the 
relevant cylinder is near top dead center of its compression stroke, 
control unit 56 deactivates the solenoid so the pressurized oil moves the 
needle valve 42.2 off its seat. Valve spring 18.2 then can move the piston 
26.2 upwardly displacing oil into conduit 40.2 so the valve 14.2 can 
close. 
By way of further example, the invention also includes embodiments where 
other means is employed as a trigger or release mechanism in place of the 
solenoids of the previous examples. For instance a mechanical trigger 
could be used and actuated by an engine valve or fuel injector mechanism. 
The description above and the drawings are by way of example only. The 
invention includes modifications within the scope of the following claims.