US 3,947,733 A · Control circuit

Abstract

A temperature-actuated circuit for controlling the application of an electronic circuit. In a typical application, the control circuit shunts a circuit which effects enrichment of the fuel mixture for the cold-starting of internal combustion engines. In a preferred embodiment, the control circuit comprises a temperature-dependent resistance, such as a thermistor, which supplies changing voltage with increasing engine temperature to the gate of an SCR. After an interval necessary to attain a predetermined engine temperature, the altered gate voltage triggers the SCR, thereby actuating a relay associated with the enrichment circuit for shunting the enrichment circuit from the fuel injection circuit. Typically, the enrichment circuit alters the width of square wave signals which control fuel delivery, so that bypassing the circuit eliminates the altered wave characteristics and provides leaner, more economical operation. The control circuit components may be selected to provide time delay operation, rather than operation controlled by an external temperature. Also, the control circuit can include features such as manual override and visual and/or audible operation displays.

Claims14

Dependent claims

A temperature-actuated control circuit for controlling the application of a portion of an electrical circuit, comprising:

resistance means comprising at least a first resistance and a second, temperature-dependent resistance in series therewith;
an SCR connected to said resistance means for generating a signal in response to a predetermined threshold signal applied via said resistance means to a gate of said SCR in the presence of a reference potential applied to said SCR;
means for selectively applying the reference potential across said resistance means and said contact means, such that, upon attainment of a predetermined temperature by said second resistance, the threshold signal is applied to the gate of said SCR;
contact means including a pair of normally closed contacts in series with said resistance means and actuated in response to the generated signal for opening and closing said contacts;
and
circuit path means connected across the electrical circuit portion and actuated by the generated signal for controlling the application of a circuit path bypassing the electrical circuit portion.

3 more elements

A temperature-actuated circuit for controlling the connection of a portion of an electrical circuit to the electrical circuit, comprising:

resistance means comprising first, second, and third resistors connected in series via a normally closed circuit path, the resistance of said second resistance being temperature dependent and the resistance of said third resistor being adjustable;
an SCR having a first, gate electrode connected between two of said series-connected resistors and having second and third electrodes such that, in the presence of a potential difference across said second and third electrodes, application of a signal of requisite threshold value to said gate via at least said first resistor actuates said SCR, thereby establishing a current across said second and third electrodes;
means for applying a potential difference across said second and third electrodes and across said resistance means such that upon said second resistor attaining a predetermined, temperature-dependent resistance value controlled by the adjustment of said third resistor, the threshold signal is applied to said gate;
and
relay means connected between the electrical circuit portion and the electrical circuit and connected to said resistance means and actuated by the SCR current for disconnecting the electrical circuit portion from the electrical circuit and for opening the circuit path of said resistance means.

2 more elements

Dependencies are inferred from the claim text.

Control circuit

Life of this patent

Control circuit

Life of this patent

Abstract

Claims14