Patent Application
20080109150
The present invention relates to internal combustion engines, and, more particularly, to starter systems for such engines.
A work machine such as used in the agricultural, forestry and construction industries typically includes an internal combustion (IC) engine providing motive force to a plurality of wheels or tracks. Examples of such work machines include agricultural tractors and combines, forestry timber harvesters, and construction track hoes and backhoes. The IC engines used in such work machines may be of the compression ignition type (e.g., diesel engines) or spark ignition type (e.g., gasoline engines).
Regardless of whether the IC engine is configured as a compression or spark ignition engine, a flywheel is typically provided at one end of a crankshaft. The flywheel provides inertial mass for smooth operation of the engine, and also typically has a toothed outer or inner periphery which is engaged by the starter during a starting sequence, such as occurs when an operator moves a starter switch (e.g., an ignition key) to a start position. The starter has an electronmechanically engaged small diameter gear which moves in an axial direction to engage the toothed flywheel when actuated using the starter switch.
A problem can occur from an operator over cranking the starter for too long a period of time. For example, diesel engines relying upon compression ignition start harder during cold weather when the fuel is colder and at a higher viscosity. Most diesel engines include a “glow plug” which in essence is an inline heater for heating the fuel prior to injection into the combustion cylinder. However, the metal surfaces of the injectors, cylinder liners, piston crowns, etc. may still be very cold and not conducive to the compression ignition process.
One solution is to use a block heater which is in communication with the liquid cooling jacket of the IC engine and warms up the fuel and various metal parts of the IC engine. It will be appreciated that given the thermal mass of the IC engine, this takes a considerable amount of time to heat the IC engine, and electrical plug-ins are not always available at a given work site. Another possible solution is to use starting fluid including ether as an active ingredient, but this can also be hard on an IC engine.
The starter includes an electric motor with a high amperage electrical input requirement. When the starter is cranked for too long a period of time (i.e., over cranked), the batteries of the work machine may be discharged. Moreover, the electric motor of the starter may fail, which is a primary problem that keeps the IC engine from being started, or keeps a work machine from being utilized. Operational instructions provide direction on starter motor operation indicating starter motor engagement times (cranking times). However, replacement of starter motors often results in warranty claims (returns and allowances expenses), and machine down time regardless of operational instructions.
A secondary problem may occur when a starter is engaged after the IC engine is already running. The outer toothed surface of the flywheel typically rotates faster than the rotational speed of the starter motor during operation. Engaging the starter when the IC engine is already running may result in physical damage to the teeth profiles on the flywheel or starter, or damage to the electric motor of the starter.
What is needed is a starter system for an IC engine which is configured to avoid damage to the starter and/or flywheel, such as may occur from over cranking the starter or engaging the starter when the IC engine is already running.
The invention in one form is directed to an internal combustion engine including a flywheel, a starter for rotatably driving the flywheel, at least one starter parameter indicator, and an engine control module. Each indicator provides an output signal representing a start or no-start condition for the starter. The engine control module is coupled with the starter and one or more indicators. The engine control module controllably actuates the starter, dependent upon the output signal from each indicator.
The invention in another form is directed to a method of operating an internal combustion engine, including the steps of: requesting an energization of a starter; verifying at least one starter parameter indicator representing a start condition or no-start condition for the starter; and controllably actuating the starter, dependent upon the requested energization of the starter and each indicator corresponding to a start condition.
Referring now to the drawings, and more particularly to
IC engine 12 is assumed to be a diesel engine in the embodiment shown, but could be a different type of IC engine such as a spark ignition engine (gasoline or propane). IC engine 12 may be used within a work machine such as described above, or may be a stationary engine such as used in generator sets, irrigation or other engine driven pumps. IC engine 12 includes a block 14 with a plurality of combustion cylinders 16. The number of combustion cylinders can vary depending upon the engine, such as 6, 8, 10 or 12 combustion cylinders. A plurality of pistons (not specifically shown) are reciprocally disposed within the respective combustion cylinders 16. The pistons are typically connected via respective piston rods with a crankshaft (not shown) which is coupled with a flywheel 18 at one end thereof.
A starter 20 includes an electric motor 22 and an electromechaniccally engaged gear 24 which engages flywheel 18 to start compression ignition within IC engine 12. Starter 20 is of course sized dependent upon the size of IC engine 12.
Starter switch 26 includes a keyslot 27 for receiving a key (not shown). Keyslot 27 is movable between a stop position A, a run position B, and a start position C. Switch 26 may also include an accessory power position, if desired. Alternatively, it is also known to provide an on-off power switch working in conjunction with a momentary push-type starter switch for energizing starter 20. As another alternative, the starter switch could be configured as a momentary push-type button with two functions. Pressing the button a first time would provide power to an ignition relay that powers up the cab. Once ignition power (run position) is on, pressing the momentary button again would provide a start command to the engine controller to energize the starter. A separate momentary push-type button would then be used to turn off the ignition.
One or more starter parameter indicators 28 provide an output signal representing a start condition or no-start condition for starter 20. In other words, when a start request is initiated by turning starter switch 26 to start position C, starter 20 cannot be started if indicator(s) 28 do not provide an appropriate output signal. In the embodiment shown, IC engine 12 includes two indicators 28 corresponding to a start condition or no-start condition for starter 20. More particularly, one indicator 28 is in the form of a run indicator 30 indicating a run condition of internal combustion engine 12, and the other indicator 28 is in the form of a time-out indicator 32 indicating the cranking time of starter 20. Run indicator 30 is in the form of an RPM sensor associated with flywheel 18 providing an output signal representing an RPM of flywheel 18. If the sensed RPM of flywheel 18 corresponds to a predetermined speed such as a speed which is higher than the input drive speed of starter 20, then IC engine 12 is already running and starter 20 is not actuated. Other types of sensors providing output signals corresponding to a run state of IC engine 12 are possible, such as sensors detecting combustion within cylinders 16, rotation of the crankshaft, etc.
Time-out indicator 32 is in the form of a timer or counter contained internally within an engine control module (ECM) 34. Timer 32 provides a time-out signal corresponding to an excess cranking time of starter 20. To that end, timer 32 is started when starter switch 26 is in start position C, and times out after a predetermined period of time.
ECM 34 is also coupled with starter 20, starter switch 26, and run indicator 30. ECM 34 controllably actuates starter 20, dependent upon the status of starter switch 26 and starter parameter indicators 28. More particularly, ECM 34 actuates starter 20, dependent upon a logical boolean operation of the output signals from each indicator 28 and the start position C of starter switch 26. If starter switch 26 is moved to start position C, run indicator 30 indicates that IC engine 12 is not running, and the time-out period for starter 20 has not been exceeded, then ECM 34 energizes motor 22 of starter 20. If IC engine 12 is already running, then ECM 34 will not energize motor 22 of starter 20 resulting in a no-start condition. When the time-out period is reached, ECM 34 deenergizes starter 20 resulting in a no-start condition for a preset period of time.
Referring now to
Referring now to
After the starter switch 26 is released and moves to run position B (line 62), then the accumulated value of the counter described above (with reference to block 66 and decision block 68) is decremented a predetermined amount (block 90). The counter value is then compared with a predetermined underflow value (e.g., 0; decision block 92). If the overflow flag is set (block 70), and the counter value has not yet reached the underflow value, or the mismatch starter source status is set, then the starter cannot be energized and the process ends (line 94). On the other hand, if the underflow value has been reached (line 96), the start source status is cleared (block 98), and if the mismatch starter source status is clear, then the starter can again be energized as described above when the starter switch is moved to start position C (block 86).
Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.
