15-10-2012, 03:40 PM
Centrifugal Clutch
Centrifugal Clutch.docx (Size: 82.55 KB / Downloads: 96)
Introduction
A centrifugal clutch is a clutch that uses centrifugal force to connect two concentric shafts, with the driving shaft nested inside the driven shaft.
The input of the clutch is connected to the engine crankshaft while the output may drive a shaft, chain, or belt. As engine revolutions per minute increase, weighted arms in the clutch swing outward and force the clutch to engage. The most common types have friction pads or shoes radially mounted that engage the inside of the rim of a housing. On the center shaft there are an assorted number of extension springs, which connect to a clutch shoe. When the center shaft spins fast enough, the springs extend causing the clutch shoes to engage the friction face. It can be compared to a drum brake in reverse. This type can be found on most home built karts, lawn and garden equipment, fuel-powered model cars and low power chainsaws. Another type used in racing karts has friction and clutch disks stacked together like a motorcycle clutch. The weighted arms force these disks together and engage the clutch.
When the engine reaches a certain speed, the clutch activates, working somewhat like a continuously variable transmission. As the load increases, the speed drops, disengaging the clutch, letting the speed rise again and reengaging the clutch. If tuned properly, the clutch will tend to keep the speed at or near the torque peak of the engine. This results in a fair bit of waste heat, but over a broad range of speeds it is much more useful than a direct drive in many applications.
Claims:
1. An engine controller for a vehicle using an automatic centrifugal clutch device for power transmission, wherein an idle speed control means is provided for an engine intake system that adjusts the amount of intake air by implementing control of the opening degree of a throttle valve, the engine controller comprising: a full-close state detecting means for detecting the full-close state of the throttle valve; an engine speed detecting means for detecting the engine speed; and an engine halt controlling means for implementing engine halt control based on the halt control starting conditions that the detected engine speed is equal to or greater than a first set rotational frequency, which is set to be equal to or lower than the clutch engagement rotational frequency of the automatic centrifugal clutch device, and that the full-closed state of the throttle valve is detected.
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an engine controller for a vehicle equipped with an automatic centrifugal clutch, such as a snowmobile, ATV (all-terrain vehicle), motorcycle, etc., including an idle speed control (abbreviated hereinbelow as ISC) device disposed in the engine intake system for adjusting the amount of intake air by a throttle valve.
Description of the Prior Art
Concerning engine intake systems for regulating the amount of intake air based on control of the opening degree at the throttle valve of an engine mounted on vehicles, such as snowmobiles, having an automatic centrifugal clutch, there are those that adopt ISC devices for controlling the idle speed by adjusting the amount of bypass air.
In a vehicle including such an ISC device, an ECM (electronic control module) is provided for the ISC device, so as to control the amount of intake air at the time of the throttle valve being fully closed, for each of the following modes (as to the prior art relating to the ISC device, refer to Japanese Utility Model Application Laid-open Sho 64 No. 34441 (FIG. 1 and the full text of the specification)).
In ISC, in startup mode, control at a start of the engine is performed by adjusting the amount of bypass air to the controlled amount for start in accordance with the cooling water temperature plus corrections for altitude and other factors.
In the complete explosion mode other than the startup mode, the basic control amount is corrected in accordance with the cooling water temperature and at the same time the idle speed is controlled by regulating the amount of bypass air.
SUMMARY OF THE INVENTION
The present invention has been devised in view of the above conventional problems, it is therefore an object of the present invention to provide an engine controller of an engine unit with an idle speed control (ISC) device for use in a vehicle including an automatic centrifugal clutch, the controller capable of preventing unintentional increase in engine speed even if the ISC device breaks down and capable of preventing excessive effect of engine brake resulting from fuel cutoff or ignition cutoff hence preventing degradation of driver's sensation during traveling.
In order to achieve the above object, the present invention is configured as follows:
In accordance with the present invention, an engine controller for a vehicle using an automatic centrifugal clutch device for power transmission, is characterized in that an idle speed control means is provided for an engine intake system that adjusts the amount of intake air by implementing control of the opening degree of a throttle valve, and the engine controller comprises: a full-close state detecting means for detecting the full-close state of the throttle valve;
an engine speed detecting means for detecting the engine speed; and an engine halt controlling means for implementing engine halt control based on the halt control starting conditions that the detected engine speed is equal to or greater than a first set rotational frequency, which is set to be equal to or lower than the clutch engagement rotational frequency of the automatic centrifugal clutch device, and that the full-closed state of the throttle valve is detected.