Method and apparatus for metering fuel in a diesel engine

• US 5,067,461 A
• Filed: 03/05/1990
• Issued: 11/26/1991
• Est. Priority Date: 09/05/1987
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Joachim, Ernst-Ulrich, Kull, Hermann
• Primary Examiner(s): Miller, Carl Stuart
• Application Number:
  US07/490,668
• Time in Patent Office: 631 Days
• Field of Search: 123/357, 123/358, 123/359, 123/479
• US Class Current: 123/357
• 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: F02D 2250/18 Control of the engine output torque
• CPC Class Codes: F02D 2250/32 Air-fuel ratio control in a diesel engine
• CPC Class Codes: F02D 31/009 for maximum speed control
• CPC Class Codes: F02D 41/1482 Integrator, i.e. variable slope
• CPC Class Codes: F02D 41/38 of the high pressure type

Abstract

A method and an apparatus for metering fuel in a diesel engine is suggested wherein the fuel quantity is taken from a multi-dimensional characteristic field in the part-load range, in the full-load range, however, a limitation of the fuel quantity is undertaken with the aid of a lambda control. Minimal value selection stages are used for decoupling the various methods of fuel quantity control. Notwithstanding the dead times present in the system, there results a dynamically satisfying lambda control system since up to a catch curve, a rapid control and thereafter a slower lambda control are used. The use of a lambda control for full-load limiting leads to an exhaust gas almost completely free of particles.

Claims

1. A method of metering fuel to a diesel engine operable at part load and full load, the engine having a controller for supplying a quantity of fuel to the engine via a fuel pump, the method comprising the steps of:

utilizing a lambda probe arranged in the exhaust gas flow of the engine to measure the actual value of lambda which is indicative of the ratio of air and fuel supplied to the engine;

providing a desired value of lambda in dependence upon at least the engine speed;

open-loop controlling the fuel quantity metered to the engine during the part-load operation in dependence upon at least the engine speed and accelerator pedal position;

comparing the desired value of lambda with the actual value of lambda;

transferring from the open-loop control to closed-loop control when the engine passes from part-load operation to full-load operation by utilizing the controller to control the actual value of lambda to the desired value of lambda by controlling the quantity of fuel metered to the engine in dependence upon the comparison of said actual and desired lambda values;

detecting the full-load when the fuel quantity value taken from the characteristic field is greater than the precontrol value dependent upon torque; and

,

at full-load, adding a time variable additional signal to the fuel quantity signal dependent upon torque.

2. The method of claim 1, wherein the additional signal increases linearly with time.

3. The method of claim 2, wherein the slope of the ramp is dependent upon the rotational speed of the engine.

4. The method of claim 3, wherein the slope of the ramp is dependent upon the dead time of the lambda control.

5. An apparatus for metering fuel to a diesel engine, the engine having a controller and a fuel pump for supplying a quantity of fuel to the engine via a fuel pump, the engine further having an exhaust pipe, the apparatus comprising:

a plurality of sensors for detecting operating characteristic variables of the engine;

a control arrangement for generating a fuel quantity signal in dependence upon said operating characteristic variables and the operating condition of the engine;

a position controller for receiving said fuel quantity signal;

said position controller being operatively connected to said fuel pump for influencing said fuel pump in response to said fuel quantity signal;

means for providing a desired value of lambda in dependence upon at least the rotational speed of the engine;

a lambda probe mounted in the exhaust pipe for providing a lambda signal indicative of the actual value of lambda;

first control means for open-loop controlling said fuel-quantity signal to control the fuel quantity metered to the engine in dependence upon the operating characteristic variables of rotational speed and accelerator pedal position when the engine operates in a load range outside of full-load operation; and

,

second control means for substituting the open-loop control of said fuel quantity for a closed-loop control thereof during the full-load operation of the engine by comparing said lambda values to each other and controlling said actual value of lambda to said desired value of lambda.

6. A method of metering fuel to a diesel engine operable at part load and full load, the engine having a controller for supplying a quantity of fuel to the engine via a fuel pump, the method comprising the steps of:

utilizing a lambda probe arranged in the exhaust gas flow of the engine to measure the actual value of lambda which is indicative of the ratio of air and fuel supplied to the engine;

providing a desired value of lambda in dependence upon at least the engine speed;

open-loop controlling the fuel quantity metered to the engine during the part-load operation in dependence upon at least the engine speed and accelerator pedal position;

comparing the desired value of lambda with the actual value of lambda; and

,

transferring from the open-loop control to closed-loop control when the engine passes from part-load operation to full-load operation by utilizing the controller to control the actual value of lambda to the desired value of lambda by controlling the quantity of fuel metered to the engine in dependence upon the comparison of said actual and desired lambda values.

7. The method of claim 6, wherein the transfer from part-load to full-load operation takes place by means of a minimum value selection.

8. The method of claim 6, wherein the fuel quantity to be metered to the engine is taken from characteristic fields.

9. The method of claim 6, wherein the fuel quantity is precontrolled in dependence upon desired speed of the engine.

10. The method of claim 6, wherein the full-load is detected when the fuel quantity value taken from the characteristic field is greater than the precontrol value dependent upon torque.