Starter thermal overload protection system

• US 4,494,162 A
• Filed: 10/30/1981
• Issued: 01/15/1985
• Est. Priority Date: 10/30/1981
• Status: Expired due to Term

• Current Assignee: Harsco Corporation
• Original Assignee: Harsco Corporation
• Inventors: Eyler, Francis R.
• Primary Examiner(s): EISENZOPF, REINHARD
• Application Number:
  US06/316,640
• Time in Patent Office: 1,173 Days
• Field of Search: 361/23, 361/22, 361/24, 361/26, 361/25, 361/29, 361/32, 361/105, 361/96, 361/97, 123/179 R, 123/179 F, 123/179 A, 123/179 B, 123/179 C, 290/38 C, 290/37 R, 318/471, 318/447, 318/472, 318/473, 318/434
• US Class Current: 361/29
• CPC Class Codes: F02N 11/10 Safety devices F02N11/08 takes precedence
• CPC Class Codes: H02H 3/087 for dc applications
• CPC Class Codes: H02H 7/0859 avoiding restarting after fault condition has disappeared

Abstract

A system for protecting the starter of an internal combustion engine from overheating as a result of cranking for an excessive period of time when the engine is difficult to start. Override circuitry is electrically interposed between a manually operable starter switch and the engine starter to apply a prescribed ON and OFF cranking sequence to the starter and thereby limit the duty cycle even though the operator continuously operates the switch. Preferably, the overall maximum duration of the start attempt (the duration of the ON and OFF cranking sequence) is limited by termination circuitry. The ON and OFF cranking intervals and, optionally, the overall maximum duration of the start attempt are particularly selected so as to allow sufficient time for motor winding heat to dissipate into the starter housing. This limited cranking duty cycle protects the starter from overheating. Also, when employed in combination with a thermostatic switch mounted on the starter housing and arranged to prevent starter energization when a predetermined temperature is reached, the limited starter ON time and intermediate resting periods permit the housing and the thermostatic switch to more closely follow winding temperature. As a further aspect, in order to maintain optimum operation of the protection system as starter load conditions vary, starter current is sensed and the starter ON/OFF duty cycle is appropriately modified in response.

Claims

1. In an internal combustion engine starting system of the type including a power source, an electric starter including motor windings within a housing, and a manually operable starter switch for selectively energizing the starter from the power source, a device for protecting the electric starter from overheating during extended cranking periods, said device comprising:

override circuitry electrically interposed between the starter switch and the starter, said override circuitry arranged to limit energization of the starter and consequent engine cranking to a predetermined timing sequence of alternating ON intervals and OFF intervals even though the operator continuously operates the starter switch, the predetermined timing sequence being selected so as to allow sufficient time for motor winding heat to dissipate into the starter housing to prevent excessive winding temperatures, and current sensing circuitry for sensing current drawn by the electric starter and for modifying the ON to OFF time ratio of said override circuitry as an inverse function of sensed starter current.

2. In an internal combustion engine starting system of the type including a power source, and electric starter including motor windings within a housing, a thermostatic switch mounted on the starter housing and connected to prevent starter energization when a predetermined temperature is reached, and a manually operable starter switch for selectively energizing the starter from the power source, a device for permitting the thermostatic switch to more closely follow winding temperature during extended cranking periods, said device comprising:

override circuitry electrically interposed between the starter switch and the starter, said override circuitry arranged to limit energization of the starter and consequent engine cranking to a predetermined timing sequence of alternating ON intervals and OFF intervals even though the operator continuously operates the start switch, the predetermined timing sequence being selected so as to allow sufficient time for motor winding heat to dissipate into the starter housing such that starter housing temperature better follows winding temperature; and

current sensing circuitry for sensing current drawn by the electric starter and for modifying the ON to OFF time ratio of said override circuitry as an inverse function of sensed starter current.