REDUCING AGENT RECOVERY CONTROL METHOD, REDUCING AGENT SUPPLY DEVICE, AND ELECTRONIC CONTROL DEVICE

摘要

Provided are a reducing agent recovery control method that does not draw urea water solution back into a pump by blocking an injection hole of a reducing agent injection valve when recovery control of the urea water solution is completed, and a reducing agent supply device and electronic control device capable of executing such recovery control. Pressure in a reducing agent supply channel is reduced by a pump when an internal combustion engine is stopped and a liquid reducing agent is recovered by opening a reducing agent injection valve. When the pressure inside the reducing agent supply channel is less than a prescribed threshold value, the pressure inside the reducing agent supply channel is increased by the pump and the blockage of the injection hole of the reducing agent injection valve is removed by using the pressure in the interior of the reducing agent supply channel so that the liquid reducing agent is not injected while the reducing agent injection valve is in an opened state, and then recovery control of the liquid reducing agent is started again.