| 摘要 |
PURPOSE:To make it possible to control an engine in accordance with altitudes with the use of a device of a simple structure, by providing, for detecting the density of oxygen in the ambient air, an oxygen density detecting device, the output of which is used for carrying out altitude compensation due to, for example, the percentage of excessive air in a combustion chamber. CONSTITUTION:Upon engine operation, a control circuit 6 to which an engine revolution number N gained from an engine speed sensor 4, and an open degree L of a pump lever obtained from a variable resistor 3, are delivered, calculates the rate of EGR of the engine. Further, the above-mentioned EGR rate is compensated in accordance with an oxygen density which is obtained by detecting a change in current running through a concentration sensing element 2 in an oxygen density detecting device 2, by means of the control circuit 6. The valve opening degree of a control valve 7 is controlled in dependence upon the compensated EGR rate so that the value of negative pressure introduced into a pressure chamber 15 in an EGR valve 1 from a negative pressure pump 8, is optimumly controlled. The above-mentioned oxygen density detecting device 2 includes the oxygen density sensing element 21 made of ZrO2 as a main component and a heater 24 which are so arranged that they surrounds a casing 29, an insulating material 26 intervening therebetween. |
