Method for controlling a pressure

Abstract

A method and an assembly for controlling the pressure in a high-pressure region of an injection system in an internal combustion engine. A set high pressure is compared to an actual high pressure in order to determine a control deviation, the control deviation representing an input variable of a controller. A high pressure pump is controlled by a solenoid valve and the angle at which the delivery of fuel by the at least one high-pressure pump is to start is used as a manipulated variable of the high-pressure closed-loop control system.

Claims

1. A method for controlling gasoline pressure in a high-pressure region of an injection system in a dual fuel internal combustion engine comprising at least one high-pressure gasoline pump for conveying gasoline and at least one additional high-pressure pump for conveying a different fuel, the method comprising the steps of: comparing a target gasoline high pressure with an actual gasoline high pressure to determine a control deviation, wherein the control deviation represents an input variable to a PI(DT.sub.1) high-pressure controller; controlling the at least one high-pressure gasoline pump by a solenoid valve; and using a camshaft angle at which delivery of gasoline by the at least one high-pressure gasoline pump begins as a control input to a gasoline high-pressure control circuit, wherein an integrating component is limited in a downward direction to a negative target fuel consumption.

2. The method according to claim 1, wherein the angle is determined based on a target volumetric flow.

3. The method according to claim 2, wherein the angle is determined from a characteristic diagram having input variables that are engine speed and the target volumetric flow.

4. The method according to claim 1, wherein a proportional coefficient is calculated as a function of the actual high pressure.

5. The method according to claim 1, wherein an integrating component is initialized with a value 0 as long as the engine is still in a starting phase and the actual high pressure is less than a presettable limit value.

6. The method according to claim 1, wherein an integrating component is limited in an upward direction as a function of engine speed when a presettable limit speed is exceeded.

7. The method according to claim 2, wherein a number of high-pressure pumps are provided, wherein the number is taken into account in calculating the target volumetric flow.

8. The method according to claim 1, including implementing the method in a high-pressure region of an injection system in which several different fuels are burned.

9. An arrangement for controlling the gasoline pressure in a high-pressure region of an injection system in a dual fuel internal combustion engine according to claim 1, the arrangement comprising: at least one high-pressure gasoline pump for conveying gasoline; at least one additional high-pressure pump for conveying a different fuel; a PI(DT.sub.1) high-pressure controller, the controller and the at least one high-pressure gasoline pump being arranged in a gasoline high-pressure control circuit, wherein a target gasoline high pressure is compared with an actual gasoline high pressure to determine a control deviation, wherein the control deviation represents an input variable to the controller; and a solenoid valve that controls the at least one high-pressure gasoline pump, wherein a camshaft angle at which delivery of gasoline by the at least one high-pressure gasoline pump should begin is a control input to the gasoline high-pressure control circuit, wherein an integrating component is limited in a downward direction to a negative target fuel consumption.

10. The arrangement according to claim 9, wherein the arrangement is configured for an injection system in which several types of fuel are burned.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 shows how the nominal high pressure is calculated;

(2) FIG. 2 shows how the nominal consumption of gasoline is calculated;

(3) FIG. 3 shows a closed gasoline high-pressure control circuit;

(4) FIG. 4 shows the algorithm of the gasoline high-pressure controller;

(5) FIG. 5 shows how the dynamic proportional coefficient is calculated;

(6) FIG. 6 shows how the nominal volumetric flow of gasoline is limited; and

(7) FIG. 7 shows a flow chart of the gasoline high-pressure control.

DETAILED DESCRIPTION OF THE INVENTION

(8) FIG. 1 shows how the nominal high pressure of the gasoline high-pressure controller is calculated. The nominal high-pressure 10 is first acquired from the 3-dimensional characteristic diagram 12 with the input variables engine speed 14 and nominal torque 16. Then a filtering process is carried out by means of a PT1 filter 18. A filter constant 20 can also be specified. In the characteristic diagram 12, curves of the nominal torque are plotted on an ordinate 22 versus the engine speed on the abscissa 24.

(9) FIG. 2 shows how the nominal consumption 50 of gasoline is calculated, which represents the disturbance variable of the gasoline high-pressure controller. For this calculation, the reference number 43 is used; see FIG. 3.

(10) If the engine is not yet synchronized, no injection will occur. In this case, the logical signal 46 has the value true, and the switch 44 assumes the upper position. This means that the nominal gasoline consumption 50 in this case is identical to zero. Once synchronization has occurred, the switch 44 assumes the lower position, which means in this case that the nominal gasoline consumption 50 is identical to the output signal 40 of the calculation unit 42. This calculation unit is a multiplier with the input signals engine speed 14, number of active cylinders 32, nominal injection quantity 34, and a constant 36.

(11) FIG. 3 shows the closed high-pressure gasoline control circuit, which is designated overall by the reference number 100. The difference between the nominal high pressure 70 and the measured actual high pressure 72 is the control deviation 74. This represents the input variable of a PI(DT.sub.1) controller 76. The output variable 78 of the PI(DT.sub.1) controller 76 is added to the disturbance variable 50; the result of this addition is the unlimited nominal gasoline volumetric flow 82. This is then limited as a function of the engine speed 14 (block 86).

(12) Because the fuel is conveyed by several feed pumps, the limited nominal volumetric flow 88 is then divided by the number of pumps 90. Thus the resulting nominal volumetric flow 116 pertains to an individual pump. By means of a 3-dimensional characteristic diagram, i.e., the gasoline pump characteristic diagram 12, with the input variables engine speed 14 and nominal volumetric flow 116, the angle 92 is determined at which the delivery of the fuel is to begin.

(13) When the engine is off, no fuel can be conveyed. In this case, the logical signal 94 has the value true, and the switch 93 assumes the upper position, as a result of which the delivery angle is set to the value of 0.

(14) Each individual high-pressure gasoline pump 96 is actuated on the basis of the resulting delivery angle 95. This angle represents the control input to the high-pressure gasoline circuit 100, which also comprises a pressure filter 98. The diagram also shows a rail 102, into which the fuel is conveyed by the high-pressure pumps 96.

(15) FIG. 4 shows the PI(DT.sub.1) algorithm of the high-pressure gasoline controller. The reference number 76 is used in FIG. 3 for this algorithm.

(16) The proportional coefficient 403 consists of the sum of a presettable, constant value 402 and a dynamic value 401 dependent on the gasoline high pressure. The proportional coefficient 403 is multiplied by the high-pressure control deviation 74, as a result of which the proportional component 404 of the PI(DT.sub.1) algorithm is obtained. The high-pressure control deviation 74 is calculated as the difference between the nominal gasoline high pressure 70 and the actual gasoline high-pressure 72.

(17) To calculate the integrating component (I component) of the PI(DT.sub.1) algorithm, the current high-pressure control deviation 74 is first added to the high-pressure control deviation 406, which has been delayed by one sampling step. This sum 407 is multiplied by the factor 408, as a result of which the product 409 is obtained. This product 409 is added to the delayed I component 411, which is delayed by one sampling step. The sum 412 is the input signal to the function block 412. Other input signals to the function block 413 include, for example, the actual engine speed 14. The function block 413 limits the integrating component of the PI(DT.sub.1) algorithm in the downward and upward directions when the switch 415 is in the lower position. The lower limit is in this case identical to the negative disturbance variable 50 of the high-pressure gasoline controller (compare FIGS. 2 and 3). The upper limit is identical to the upper limit of the unlimited nominal gasoline volumetric flow 82: The upper limit is constant when the actual engine speed 14 is less than or equal to a presettable limit speed. If the engine speed is greater than this limit speed, the upper limit is proportional to the engine speed (compare FIG. 6).

(18) When the switch 415 is in the upper position, the integrating component is identical to 0. This is the case when the logical signal 416 assumes the value true. The signal 416 assumes the value true when the actual high pressure 72 is less than a presettable limit value 428 and the engine simultaneously is still in the starting phase, that is, the idling speed has not yet been reached after the engine has been started. In this case, the signal 429 assumes the value 1. The I component 417 of the PI(DT.sub.1) algorithm is also multiplied by the factor 418. The result 419, finally, is added to the proportional component 404.

(19) For the calculation of the DT.sub.1 component, the current high-pressure control deviation 406 delayed by one sampling step is subtracted from the current high-pressure control deviation 74. The difference 420 is then multiplied by the factor 421, as a result of which the product 422 is obtained. To this product is added the DT.sub.1 component 426, which has been delayed by one sampling step and multiplied by the factor 425, as a result of which the current DT.sub.1 component 427 is obtained. The sum of the proportional component 404, the result 419, and the DT.sub.1 component 427, finally, yields the PI(DT.sub.1) component 78.

(20) The function blocks 405, 410, and 423 are time-delay elements, which delay the input signal in question by one sampling step.

(21) FIG. 5 shows how the dynamic proportional coefficient 401 is calculated. This value is plotted on the ordinate 200 versus the gasoline high pressure on the abscissa 202.

(22) If the gasoline high pressure is lower than the limit value 204, the dynamic proportional coefficient is identical to the constant, presettable value 206.

(23) If the gasoline high pressure is above the limit value 208, the dynamic proportional coefficient is identical to the constant, also presettable value 210.

(24) If the gasoline high pressure is less than or equal to the upper limit value 208 and greater than or equal to the lower limit value 204, the dynamic proportional coefficient depends in linear fashion on the gasoline high pressure.

(25) FIG. 6 shows how the unlimited nominal gasoline volumetric flow 82 is limited. The reference number 86 is used for this in FIG. 3.

(26) If the engine is off, the signal 510 is identical to the value true, and the switch 509 assumes the upper position. Thus the limited nominal gasoline volumetric flow 88 is identical to 0.

(27) If, however, the engine is not off, the limited nominal gasoline volumetric flow 88 is identical to the output of the switch 504, i.e., the signal 508.

(28) The upper limit value of the nominal gasoline volumetric flow is identical to the signal 507, i.e., the output value of the function block 505. If the unlimited nominal gasoline volumetric flow 82 is greater than the upper limit value 507, the switch 504 assumes the lower position; i.e., in this case the signal 508 is identical to the signal 507. Thus the limited nominal gasoline volumetric flow 88 is always identical to the upper limit value 507 of the nominal gasoline volumetric flow when the engine is off and the upper limit value is exceeded. The upper limit value 507 is in this case calculated as the output of the function block 505 as a function of the engine speed 14: If the engine speed is less than or equal to the presettable limit speed 506, the signal 507 assumes a constant value. If the engine speed is greater than the limit speed 506, the upper limit value 507 increases in linear fashion with the engine speed.

(29) If the unlimited nominal gasoline volumetric flow 82 is less than or equal to the upper limit value 507, the switch 504 assumes the upper position. In this case, the signal 508 is identical to the output of the switch 502. If the unlimited nominal gasoline volumetric flow 82 assumes a negative value, the upper position of the switch 502 becomes active; i.e., in this case the output of the switch 502 is identical to the value 0. If, however, the unlimited nominal gasoline volumetric flow 82 is greater than or equal to 0, the switch 502 assumes the lower position, as a result of which its output is identical to the unlimited nominal gasoline volumetric flow 82.

(30) FIG. 7 shows a flow chart of the operation of the high-pressure gasoline control system. In step S1, the gasoline high pressure 72 is entered. In step S2, the gasoline high-pressure control deviation 74 is calculated as the difference between the nominal gasoline high pressure 70 and the actual gasoline high pressure 72.

(31) In step S3, the output variable of the PI(DT.sub.1) high-pressure controller is calculated. In step S4, the unlimited nominal volumetric flow is calculated as the sum of the PI(DT.sub.1) high-pressure controller output and the nominal gasoline consumption (addition of the disturbance variable). In step S5, the nominal gasoline volumetric flow is limited.

(32) In step S6, the limited nominal volumetric flow is divided by the number of gasoline high-pressure pumps. In step S7, the delivery angle 95 is calculated as the output variable of the gasoline pump characteristic diagram. In step S8, it is determined whether the engine is off or not. If the engine is not off, the delivery angle is identical to the output variable of the gasoline pump characteristic diagram (step S9). Then the program goes back and begins again with step S1.