Watercraft engine control

A personal watercraft catalytic exhaust system wherein an over-temperature sensor is provided that is effective to shut down the engine in the event the catalyst reaches a dangerous temperature. The engine, once shutdown, cannot be restarted until the temperature falls below a predetermined temperature which may be lower than the overheat temperature. In the process of stopping the engine, it is slowed down first so as to give the rider additional warning that the shutdown procedure will be initiated.

BACKGROUND OF THE INVENTION 
This invention relates to a small personal type watercraft and more 
particularly to an improved engine control for such a type of watercraft. 
The field of so-called "personal watercraft" is one that is growing 
rapidly. However, due to the large number of such watercraft, there is a 
concern for improving environmental protection by implementing engine 
controls for such watercraft. In many instances, catalytic treatment is 
desirable for the watercraft engine, particularly when the engine is of 
the two-cycle, crankcase compression type. 
Because of its very nature, however, the small confined space available for 
the propulsion unit in such watercraft gives rise to certain problems. As 
is well known, the catalyst must be at or above a specific temperature in 
order to operate efficiently. However, under some operating conditions, 
the temperature of the catalyst may become quite elevated, particularly 
when large amounts of exhaust gases having high amounts of unburned 
hydrocarbons must be treated. This provides certain problems in connection 
with heat control. 
Although the heat or temperature of the catalyst can be controlled and is 
controlled by water-jacketing the catalyst, too high a cooling of the 
catalyst can result in its operation at temperatures less than those 
required in order to be effective. Thus, the amount of cooling provided 
should be limited so as to avoid over-cooling of the catalyst. This 
further aggravates the problem of preventing excess temperatures. 
It is, therefore, a principal object of this invention to provide an 
improved control arrangement for the engine of a personal watercraft 
having a catalytic converter. 
It is a further object of this invention to provide an improved catalytic 
converter control arrangement for a personal watercraft wherein 
overheating conditions can be avoided. 
It may be desirable in order to provide effective control to incorporate an 
arrangement wherein the engine of the watercraft is slowed or stopped if 
the temperature of the converter becomes too high. However, merely 
stopping the engine does not totally avoid these potential problems. 
For example, the watercraft may be shut down and then the operator can 
again restart the watercraft engine. Since starting techniques frequently 
provide richer than normal mixtures, further aggravation of the overheated 
condition of the catalyst can occur if the engine is started again too 
soon after shutdown. 
It is, therefore, a further object of this invention to provide an improved 
temperature control system for the catalytic exhaust of a personal 
watercraft wherein restarting of the engine after shutdown is not 
permitted until the catalyst reaches a safe temperature. 
In conjunction with the shutting down of the engine to prevent damage due 
to catalyst overheating, if the engine is abruptly stopped, certain other 
ancillary problems may arise. Also, this may fail to give the operator 
warning of shutdown among other problems. 
It is, therefore, a further object of this invention to provide an improved 
shutdown procedure for a catalytic exhaust system of a personal 
watercraft. 
SUMMARY OF THE INVENTION 
This invention is adapted to be embodied in a personal watercraft having a 
hull in which an engine is mounted. The engine drives a propulsion devices 
for propelling the personal watercraft through a body of water. The engine 
is provided with an exhaust system for discharging exhaust gases from the 
combustion chamber of the engine to the atmosphere. This exhaust system 
includes a catalyst bed through which the exhaust gases are passed for 
treating the exhaust products and removing harmful constituents. An 
arrangement is provided that incorporates a starting system for starting 
the engine and also a sensing arrangement senses the temperature of the 
catalyst. 
In accordance with a first feature of the invention, an engine shutdown 
procedure is initiated if the catalyst is at a temperature that is greater 
than a predetermined temperature. Once the shutdown procedure is 
initiated, the engine cannot be restarted until the catalyst temperature 
falls below a predetermined lower safe value. 
In accordance with another feature of the invention, the shutdown procedure 
is comprised of initially slowing the engine and then stopping the engine 
after it is slowed sufficiently so as to give the operator notification or 
warning of the shutdown.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now in detail to the drawings and initially primarily to FIGS. 
1-3, a personal watercraft constructed in accordance with an embodiment of 
the invention is indicated generally by the reference numeral 11. The term 
"personal watercraft" is intended to describe a relatively small type of 
watercraft having a generally sporting nature and designed primarily for 
operation by a single rider and accommodating one or more passengers. By 
its very nature, the personal watercraft such as the watercraft 11 is 
quite compact in nature and this gives rise to the potential difficulties 
as aforenoted. A specific type of personal watercraft is illustrated and 
will be described, but it should be readily apparent to those skilled in 
the art how the invention can be practiced with personal watercraft of 
other configurations and types. 
The watercraft 11 is comprised of a hull assembly, indicated generally by 
the reference numeral 12, which is comprised primarily of a hull underpart 
13 and a deck 14. The hull parts 13 and 14 are preferably formed from a 
molded fiberglass reinforced resin or the like, and are secured to each 
other around their outer periphery at a gunnel area 15. 
The deck portion 14 is formed at its rearward end with a rider's area. This 
rider's area is comprised of a raised seat portion 16 on which the rider 
and passengers may be seated in a straddle fashion and in tandem 
relationship if more than one person occupies the watercraft 11. On 
opposite sides of the raised seat portion 16, there are provided depressed 
foot areas 17 wherein the seated riders may place their feet. As is 
typical with this type of watercraft, the foot area 17 may open through 
the transom of the watercraft to facilitate entry and exit while the 
watercraft 11 is floating in a body of water. 
A control mast 18 is provided forwardly of the seat 16 and carries a 
handlebar assembly 19 for control of the watercraft in a manner which is 
well known in the art and which will be described to some extent later. 
In the area below the rider's area, as is typical with the personal type 
watercraft of this nature, the hull and deck portions 13 and 14 define an 
engine compartment 21 which is delimited at its rear end by a bulkhead 22. 
An internal combustion engine, indicated generally by the reference 
numeral 23, is supported on a lower part 24 of the hull portion 13 within 
the engine compartment 21. As may be best seen in FIG. 2, the seat portion 
16 has a removable part which, when removed, opens an access opening 25 
through which the engine 23 may be serviced. 
In the illustrated embodiment, the engine 23 is of the two-cycle, crankcase 
compression type and is depicted as being of the inline type. Although the 
invention is described in conjunction with such an engine, as should be 
apparent from the following description, the various features of the 
invention can be utilized in combination with engines of other types and 
other than two-cycle engines. 
The engine 23 is mounted in the hull engine compartment and has an output 
shaft 26 that is coupled to the impeller shaft of a jet propulsion unit, 
indicated generally by the reference numeral 27, and positioned on the 
underside of the hull portion 13 rearwardly of the bulkhead 22. 
This jet propulsion unit 27 has a downwardly facing water inlet opening 
through which water is drawn under the action of an impeller driven by the 
engine output shaft 26. This water is then discharged rearwardly through a 
discharge nozzle portion 28 to provide a propulsive force for the 
associated watercraft hull 12. A pivotally supported steering nozzle 29 is 
mounted on the end of the discharge nozzle portion 28 and is controlled by 
the handlebar 19 for steering of the watercraft in a manner well known in 
this art. 
Still referring primarily to FIGS. 1-3, the engine 23 is provided with an 
induction system, indicated generally by the reference numeral 31, and 
which supplies an air fuel charge to the crankcase chambers of the engine 
23. These crankcase chambers are formed below a cylinder block 32 which is 
inclined to the vertical as best seen in FIG. 3 to permit a more compact 
construction and still afford easy access to the various engine 
components. 
The induction system 31 communicates with a crankcase assembly 33 and 
includes an air inlet device 34. The air inlet device 34 collects air from 
within the interior of the engine compartment and delivers it to a charge 
former such as one or more carburetors 35. The carburetors 35 communicate 
with intake ports in the crankcase chamber 33 for delivering the fuel air 
charge thereto. 
Fuel is supplied to the carburetor 35 or such other charge formers as the 
engine may employ from a fuel tank 36 that is positioned in the hull 
forwardly of the engine 23. The fuel supply system may be of any known 
type. 
The fuel air charge which has been delivered to the crankcase chambers is 
transferred to the combustion chambers through a scavenge system of any 
known type and further compressed above the pistons as they move toward 
top dead center. This charge is fired at an appropriate time by an 
ignition system which is not shown, but which may be controlled in a 
manner as will hereinafter be described. The exhaust gases are then 
discharged to the atmosphere through an exhaust system, indicated 
generally by the reference numeral 37. 
This exhaust system 37 includes an exhaust manifold 38 which has individual 
branch or collector sections 39 that communicate with the exhaust ports 
formed in the cylinder block 32 for collecting the exhaust gases and 
delivering them through runner sections 41 to a collector section formed 
in an expansion chamber portion of the exhaust manifold 38. The exhaust 
manifold 38 communicates with a further expansion chamber device, 
indicated generally by the reference numeral 42, and which includes a 
catalyst bed assembly 43 that is mounted on a support plate 44 held 
between a forward section 45 and a rearward section 46 of the expansion 
chamber device 42. This catalyst bed 43 may be of any desirable or known 
type so as to treat the exhaust gases to remove the desired harmful 
constituents therefrom. 
The expansion chamber portion 46 has a downwardly extending part that 
extends downwardly at a point to the rear of the engine 23 where it is 
connected to an exhaust pipe 47. The exhaust pipe 47 terminates in a water 
trap device 48 that is provided in the hull portion 13 on one side of the 
tunnel that receives the jet propulsion unit 27 as best seen in FIGS. 1 
and 2. 
An exhaust discharge pipe 49 extends from the water trap device upwardly 
and transversely across the upper portion of the jet propulsion unit 48 to 
terminate at a discharge end 51 that communicates with a tunnel formed in 
the hull under-surface adjacent the jet propulsion unit discharge nozzle 
28. 
It should be noted that the portion of the watercraft 11 as thus far 
described including the engine 23 and the general nature of the exhaust 
system 37 is only to permit those skilled in the art to understand the 
environment in which the invention is utilized. The invention deals 
primarily with a construction for monitoring the condition of the catalyst 
bed assembly 43 as well as the temperature downstream of the bed assembly 
43 and controlling the engine 23 under certain abnormal conditions. 
Therefore, the portions of the construction as thus far described has been 
described and illustrated only generally. It will be readily apparent to 
those skilled in the art how the invention can be practiced with any 
desired type of structure. 
The mounting of the catalyst bed assembly 43 and the construction of the 
catalyst bed will now be described in more detail by more reference first 
to FIGS. 4-6. It may be seen that the catalyst bed assembly 43 includes, 
in addition to the mounting plate 44, a tubular member 52 that is 
generally co-extensive with the interior diameter of the joined outer 
housing portions 45 and 46. These outer housing members have a double wall 
construction so as to provide a water jacket W to which cooling water from 
the engine is delivered. This water may be delivered also through similar 
water jacketing in the exhaust manifold 38 or through external conduitry. 
A honeycomb-type structure 53 is provided within the shell 52 and is coated 
with the appropriate catalytic material so as to treat the exhaust gases 
as they flow through the exhaust system. The mounting plate 44 also has 
water opening holes W so that the water jackets of the members 45 and 46 
can communicate with each other. 
A temperature sensor probe 54, which may comprise a thermocouple-type 
device, is mounted by means of a mounting base 55 on the housing member 46 
so that the probe 54 protrudes into the area immediately downstream of the 
catalyst bed 53. An output from this temperature sensor 54 is transmitted 
to a controller 56 (FIG. 7), which may comprise an ECU for motor control 
and which performs the control strategy for operating the engine 23 and 
its various systems including the over-temperature system which will be 
described shortly. The output from the sensor probe 54 is not employed, 
however, for this particular over-temperature protection in the 
illustrated embodiment, although this is possible. 
An over-temperature sensor, indicated generally by the reference numeral 
57, is mounted in the housing member 46 in line with a centerline CL of 
the flow path through the honeycomb bed 53 so that it will be directly 
impacted by the exhaust gases flowing through an internal passageway 58 
formed by the inner shell of the member 46. The output from this sensor 57 
is also outputted to the ECU 56. 
Although this location is a preferred location for the over temperature 
indicator 57, it may also be located at other places along the exhaust 
system downstream of the catalyst bed 43. For example and as shown in FIG. 
4, the high temperature or over-temperature sensor 57 may be located at 
the alternative location 57a at the point where the expansion chamber 
catalyst bed housing section 46 joins with the exhaust pipe 47. This 
alternative location is also shown in FIG. 7 by a like designation. 
A fitting 59 is placed in the housing section 46 in a downstream location. 
The fitting 59 is adapted to receive a sampling tube 61 so that exhaust 
gas sampling may be done to determine the efficiency of the catalytic 
system. 
As may be best seen in FIGS. 4 and 5, the lower end of the housing member 
46 that joins with the tail pipe 47 is closed by a member 62 that has a 
plurality of circumferentially spaced openings 63 which allow the water to 
flow from the water jacket W through an open end of the housing member 46 
into the interior of the exhaust pipe 47. This member 62 is held in place 
by threaded fasteners 64. 
It should be noted that the exhaust pipe 47 is comprised of an outer 
elastic member 65 and an inner heat-protecting aluminum sleeve 66. Thus, 
vibration can be absorbed while the exhaust gases will not attack the 
elastomeric member 65. Also, since the cooling water is mixed with exhaust 
gases at this point, the temperature will be lowered so as to avoid 
damage. In order to cool the exhaust gasses without excessively cooling 
the catalyst bed assembly, cooling water that has not passed through the 
engine cooling jackets through a fresh water inlet port 67 in the housing 
member 46 down stream from the catalyst bed assembly 43 (FIG. 5). 
Referring now primarily to FIGS. 7-9, it has been noted that the signals 
from the temperature sensor 54 and the over-temperature sensor 57 are 
transmitted to the ECU 56. The ECU 56 also receives various other 
information from engine and ambient sensors for engine control and outputs 
a signal through a conductor 68 to the ignition circuit of the engine 
among other things. 
Also, a control panel 69 is mounted forwardly of the control mast 18 and 
handlebar 19 as seen also in FIG. 1 to display certain information to the 
operator. This display 68 can include an over-temperature warning light 71 
and/or temperature gauge and an over temperature warning buzzer 72. 
Basically, the control strategy for the system, which will be described 
momentarily by reference to FIGS. 8 and 9, is such that if the temperature 
sensed by the overheat sensor 57 exceeds a predetermined relatively high 
temperature, for example a temperature in the range of about 250.degree. 
C., a protective routine is initiated. This protective routine includes 
the step of first slowing the engine 23 if it is operating at any elevated 
speed by misfiring the spark plugs. This will give the operator a physical 
warning that the overheat condition is existent and also will notify that 
the engine 23 will be shut down shortly. At the same time, the warning 
light 71 is illuminated and the warning buzzer 72 is sounded. Then, the 
engine will be stopped. 
In addition to stopping the engine, the starting circuit for the engine 
which includes a starter button 73 on the control panel 69 will be 
disabled so that the engine cannot be restarted until the temperature of 
the overhead sensor 57 falls to a predetermined lower temperature such as 
a temperature in the range of about 100.degree. C. 
This control routine will now be described by reference to FIGS. 8 and 9. 
Starting first with FIG. 8, the program starts at the step S1 to determine 
if the engine start switch or starter button 73 has been depressed to 
actuate a starter motor (not shown). If it has, the program moves ahead 
and if not, it repeats. 
Assuming the starter button has been depressed, the program moves to the 
step S2 to determine if the temperature of the overheat sensor 57 is over 
250.degree. C. If it is, the program moves to the step S3 to activate the 
warning and repeats back. Thus, the operator will be warned that the 
catalyst is over-temperature condition and he will not be able to start 
the engine. 
If, however, the temperature sensor has fallen below the dangerous 
temperature which is, for example, assumed to be 250.degree. C., the 
program moves to the step S4 to deactivate the warning. 
The program then moves to the step S5 to perform a self-checking function 
to determine if the system is operating properly. If it is not, the 
program moves to the step S6 to turn the warning on. The warning 
arrangement may be provided with a bypass switch that precludes its 
actuation and at the step S7, it is determined if this switch is turned 
off. If it is not, the program repeats. If it is, however, at the step S8 
the warning is deactivated. 
If at the step S5 it is determined that a control system is operating 
acceptably, the program moves onto the step S9 which, in essence, involve 
turning on the ignition switch. 
Once the ignition switch is turned on, the program moves to the step S10 to 
determine if the temperature of the over head sensor has fallen to 
110.degree. C. or below. If it has not, the program merely repeats. 
Once the temperature has dropped below 110.degree. C., then the program 
moves to the next phase of the control routine which appears in FIG. 9. 
At the step S11, the warning lamp and warning buzzer are turned on. This is 
just done as a self-checking function so that the operator can ascertain 
that the warning system is operative. 
The program then moves to the step S12 to determine if the engine stop or 
kill switch is turned on. If it is, the program moves to the step S13 to 
determine if a preset time period has passed. If it has not, the program 
repeats. If it has, however, then the warning light is turned off. In 
other words, once the warning has been established, it will remain on for 
a predetermined time period even after the system is shut down. 
Returning again to the step S12, if the engine stop switch is not on, then 
the program moves to the step S15. At this step, it is determined if the 
overheat sensor's temperature is above 250.degree. C. If it is not, the 
program repeats back to the step S12 and the system functions normally 
until the stop switch is turned on or until the temperature exceeds 
250.degree. C. at the step S15. 
When the temperature exceeds 250.degree. C., then the program moves to the 
step S16 to initiate a slowing of the engine speed. This is done, as 
aforenoted, by misfiring the spark plugs. 
In accordance with one control routine, the engine speed is permitted to 
operate at a slower speed for a time period which is preset. At the step 
S17, it is determined if this time period has elapsed. If it has not, the 
program repeats. If it has, however, then the program moves to the step 
S18 and stops the engine. 
It should be noted that in an alternative control routine, the program may 
move directly from the step S16 to the step S18 as shown by the phantom 
line in FIG. 9. 
Once the engine is stopped, then the program starts a timer running and at 
the step S19 determines if that time has elapsed. If it has not, the 
warning light is left on. If, however, the time has elapsed, then at the 
step S20, the warning is turned off. 
Thus, from the foregoing description, it should be readily apparent that 
the arrangement is such that at any time either during starting or when 
the engine is running and the temperature exceeds 250.degree. C. or 
whatever predetermined dangerously high temperature is chosen for the 
system, the engine will be stopped preceded by a slowing of the engine 
speed, although that step may be skipped if desired. However, once the 
condition has been exceeded and the engine stopped, it cannot be restarted 
until the temperature falls below that high temperature and in a preferred 
embodiment below a lower temperature such as 110.degree. C. 
Of course, it should be understood that the foregoing description is that 
of the preferred embodiment of the invention. Various changes and 
modifications may be made without departing from the spirit and scope of 
the invention, as defined by the appended claims.