Exhaust temperature monitoring system

• US 4,078,531 A
• Filed: 11/01/1976
• Issued: 03/14/1978
• Est. Priority Date: 05/23/1975
• Status: Expired due to Term

• Current Assignee: John T. Hewitt
• Original Assignee: John T. Hewitt
• Inventors: Hewitt, John T.
• Primary Examiner(s): Myhre, Charles J.
• Assistant Examiner(s): Lazarus, Ira S.
• Application Number:
  US05/737,435
• Time in Patent Office: 498 Days
• Field of Search: 123/198 D, 123/198 DB, 123/198 DC, 123/41.15, 123/102, 73/137, 73/343.5, 73/346, 323/75 H, 340/57
• US Class Current: 123/198.00D
• CPC Class Codes: F02B 3/06 with compression ignition compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02
• CPC Class Codes: G01K 1/024 for remote indication
• CPC Class Codes: G01K 7/021 Particular circuit arrangements G01K7/026, G01K7/12, G01K7/14 take precedence
• CPC Class Codes: G01M 15/048 by monitoring temperature
• CPC Class Codes: G01M 15/104 using oxygen or lambda-sensors testing catalytic converters F01N3/18, F01N11/007

Abstract

An exhaust temperature monitoring unit is provided with a thermocouple connected in opposition to a reference signal across the differential inputs of an operational amplifier. Both the thermocouple and the reference signal are connected to a common ground which is isolated from the vehicle chassis. This provides a floating reference point which is insensitive to variations in ground potential and eddy current in the vehicle chassis. The operational amplifier drives an optical coupling unit which in turn controls various alarms and vehicle controls.

Claims

1. An exhaust temperature monitoring system for use in a vehicle having an exhaust manifold comprising:

a voltage transformer having inputs from the electrical system of said vehicle including a coupling to vehicle ground and having an output lead isolated from vehicle ground and serving as a common floating ground and having other output leads carrying a power output and a voltage reference signal;

variable voltage dividing means connected to said output lead of said voltage transformer serving as said floating ground and to another output lead from said voltage transformer to receive said voltage reference signal and having a voltage tap therefrom;

differential summing amplifier means connected to receive said power output from said voltage transformer and having one signal input from said voltage tap of said variable voltage dividing means;

thermocouple means adapted for thermal contact with said manifold and having one electrical lead connected to said floating ground and having another electrical lead connected as a signal input to said differential summing amplifier means;

optical coupling means connected to receive the output of said differential summing amplifier means and to generate an output signal at a potential with respect to said floating ground; and

alarm means operatively connected to said optical coupling means for producing an alarm responsive to the output of said optical coupling means.

2. The exhaust temperature monitoring system of claim 1 further characterized in that a plurality of variable voltage dividers, differential amplifiers, optical coupling means and alarm means are provided, and said thermocouple means is connected to said floating ground and to each of said differential amplifiers.

3. The exhaust temperature monitoring system of claim 1 further characterized in that a plurality of alarm means are provided each connected to the aforesaid optical coupling means and each responsive to the output of said optical coupling means at a unique threshold.

4. The exhaust temperature monitoring system of claim 1 wherein said differential summing amplifier means is an operational amplifier.

5. The exhaust temperature monitoring system of claim 1 wherein said alarm means is an audible alarm mechanism.

6. The exhaust temperature monitoring system of claim 1 wherein a delay means is interposed between the output of said optical coupling means and said alarm means.

7. An exhaust temperature monitoring system for use in a vehicle employing an internal combustion engine and having an exhaust manifold comprising;

a voltage transformer having inputs from the electrical system of said vehicle including a coupling to vehicle ground and having an output lead isolated from vehicle ground and serving as a common floating ground and having other output leads carrying a power output and a voltage reference signal,

variable voltage dividing means connected to said floating ground and connected to receive said voltage reference signal and having a voltage tap therefrom,

differential summing amplifier means connected to receive said power output from said voltage transformer and having one signal input from said voltage tap of said variable voltage dividing means;

thermocouple means adapted for thermal contact with said manifold and having one electrical lead connected to said common voltage ground and having another electrical lead connected as a signal input to said differential summing amplifier means;

optical coupling means connected to receive the output of said differential summing amplifier means and to generate an output signal at a potential with respect to said floating ground; and

control means operatively connected to said optical coupling means for adjusting operating parameters of said vehicle.

8. The exhaust temperature monitoring system of claim 7 wherein said control means regulates fuel flow to the internal combustion engine of the vehicle.