Internal-combustion engines – Engine speed regulator – Idle speed control
Reexamination Certificate
1999-10-13
2001-02-06
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Engine speed regulator
Idle speed control
C123S339140, C123S339190, C123S352000
Reexamination Certificate
active
06182634
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to a low RPM switching tachometer and more particularly to utilizing the tachometer for switching power draining devices on a work machine to a lower power output level when the engine is running at a specific RPM within a low idle range so that engine stalling is prevented.
1. Background Art
Present work machines utilize various devices, such as implement pumps, air conditioning compressors, fans, and the like that reduce the power or RPM of an engine during operation. Generally, such a reduction in the RPM of the engine does not affect the smooth operation of the work machine. However, when the engine is running at a low RPM or within a low idle range, any additional reduction of engine power brought about by any one of these devices may cause the engine to stall. Typically, in order to overcome the stalling problem, most work machines have incorporated a higher RPM capability within the low idle range. Unfortunately, such an increase in the RPM for the low idle range may limit performance of the work machine because certain operations may be conducted at too high an RPM level. Therefore, it is important to be able to automatically switch any one of these devices to a lower power output level when the engine is within the low idle range without incorporating a higher RPM capability to prevent stalling of the engine.
The present invention is directed to overcoming the problems as set forth above.
2. Disclosure of the Invention
In one aspect of the present invention, a work machine is disclosed that has an engine producing a rotational speed between a preselected low idle range and a preselected high idle range, an electrical power source, means for generating signals commensurate with rotational speed of the engine (RPM), and a tachometer for providing visual indication of the RPM. The work machine comprises at least one device operatively associated with the work machine. The device produces a power output measurable between a plurality of levels. A controller is locatable within the tachometer and is responsive to the RPM signal when the engine is at a first specified RPM within the preselected low idle range. The controller converts the RPM signal to an electrical signal. A relay is located in line between the controller and the at least one device. The relay is responsive to the electrical signal from the controller for automatically switching the at least one device from a first power output level to a second power output level that is lower than the first power output level.
In another aspect of the present invention, a method of preventing an engine from stalling during operation of a work machine is disclosed. The engine is operatively associated with the work machine and produces a rotational speed between a preselected low idle range and a preselected high idle range. The work machine includes an electrical power source, means for generating signals commensurate with rotational speed of the engine (RPM), and a tachometer for providing visual indication of the RPM. The method comprises the steps of operating at least one device with a specific function for the work machine at a power output measurable between a plurality of levels. Then, converting the RPM signal to an electrical signal when the engine is at a first specified RPM within the preselected low idle range. Finally, automatically switching the at least one device in response to the electrical signal from a first power output level to a second power output level that is lower than the first power output level to maintain the engine within the preselected low idle range.
In yet another aspect of the present invention, a work machine is disclosed that has an engine producing a rotational speed between a preselected low idle range and a preselected high idle range, an electrical power source, means for generating signals commensurate with rotational speed of the engine (RPM), and a tachometer for providing visual indication of the RPM. The work machine comprises at least one device operatively associated with the work machine. The device produces a power output measurable between a plurality of levels. A controller in communication with the tachometer and responsive to the RPM signal when the engine is at a first specified RPM within the preselected low idle range. The controller converts the RPM signal to an electrical signal. A relay is located in line between the controller and the at least one device. The relay is responsive to the electrical signal from the controller for automatically switching the at least one device from a first power output level to a second power output level that is lower than the first power output level.
The present invention prevents an engine, running within a low idle range, from stalling during operation of a work machine. The present invention includes a controller within a tachometer that is responsive to a first specified low idle RPM signal from the engine. The controller converts the RPM signal to an electrical signal that is directed to a relay. The relay is responsive to the electrical signal to automatically switch at least one device from a first power output level to a second power output level lower than the first power output level. The ability to automatically switch the at least one device to a lower power output level, when the engine is at a specified low idle RPM, maintains the engine within the preselected low idle range. This allows the preselected low idle range of the engine to have a lower RPM capability for smoother and more precise operational control of the work machine.
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Caldwell Sarah D.
Elliott Robert Q.
Francis John E.
Landon W. Frank
Smith David M.
Caterpillar Inc.
Charlton Diana L.
Vo Hieu T.
Yuen Henry C.
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