Control method of automatic transmission for automobiles with exhaust brake

Claim 1

A control method of an automatic transmission for an automobile with an exhaust brake including automatic speed change means for automatically switching a speed change stage of at least three speeds, an exhaust brake unit with a control means, sensor means for detecting a degree of throttle opening; sensor means for detecting car speed, and means for determining if a downshift point is passed over, including the steps of: transmitting a signal from said exhaust brake control means which indicates a particular condition of an exhaust brake control switch; detecting said degree of throttle opening so as to determine whether a particular downshift pattern should be selected; detecting said car speed by said sensor means for detecting car speed selecting a downshift pattern that is to be compared with said car speed; comparing the detected car speed and the selected downshift pattern and determining from that comparison whether a downshift point is to be passed over; and downshifting the automatic transmission by said automatic speed change means in response to said signal transmitted from said exhaust brake control means and thereby effecting an engine braking force.