JP2016011601A - Internal combustion engine fuel injection control unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control unit capable of accurately controlling a fuel pressure even if an operating state of an engine transitions from a fuel injection state to a fuel stop state of even if the operating state transitions from the fuel stop state to the fuel injection state.SOLUTION: At a time of calculating a feedback amount containing an integration term based on a time integration value of a deviation between a target value and an actual value of a fuel pressure, if an operating state of an internal combustion engine transitions from a first state in which an injection valve injects fuel to a second state in which the injection valve does not inject fuel, a value of an integration term before transition is stored and a value of the integration term after the transition is determined to be zero. If the operating state then transitions from the second state to the first state, the value of the integration term after the transition is determined to the stored value. As a result, it is possible to prevent the fuel pressure from deviating from the target value if a fuel injection state of injecting the fuel from the injection valve suddenly changes, and to improve fuel pressure controllability.

Description

  The present invention relates to a fuel injection control device applied to an internal combustion engine including an injection valve that injects fuel into a cylinder.

  Conventionally, there has been proposed a fuel injection control device that controls the pressure of fuel supplied to an injection valve (hereinafter referred to as “fuel pressure”) in consideration of the operating state of the internal combustion engine. For example, in one of the conventional control devices (hereinafter referred to as “conventional device”), the fuel pressure in a fuel stop state (for example, during fuel cut operation) in which fuel is not injected from the injection valve is caused by heat reception of the fuel supply pipe. When the fuel pressure rises to a predetermined threshold, the fuel pressure is intentionally increased. As a result, the conventional device reduces the frequency with which the relief valve for adjusting the fuel pressure provided in the pipe opens and closes, thereby reducing the degradation of the relief valve and operating noise (see, for example, Patent Document 1). . Hereinafter, the internal combustion engine is simply referred to as “engine”.

JP 2013-231362 A

  By the way, the conventional apparatus sets the target value of the fuel pressure based on the operating state of the engine, and performs control (that is, fuel pressure control) to match the actual value of the fuel pressure with the target value. One method of such fuel pressure control is feedback control.

  When performing feedback control of the fuel pressure, in general, in order to eliminate the residual deviation between the target value and the actual value, the feedback amount including the “integral term based on the time integral value of the deviation between the target value of the fuel pressure and the actual value” It may be used (for example, so-called PI control or PID control). However, in order to calculate the integral term, it is necessary to integrate the deviation over time, and in general, a predetermined time difference (from the actual value of the fuel pressure changes until the integral term follows the change) Response delay time) occurs.

  Therefore, for example, when the engine operating state shifts from a “fuel injection state” in which fuel is injected from an injection valve to a “fuel stop state” in which fuel is not injected from the injection valve (for example, when fuel cut operation is started). A predetermined response delay until the integral term changes from a value before the transition (usually a positive value or a negative value inherent to the device) to a value suitable for the fuel stop state after the transition (for example, zero). It takes time. As a result, due to this response delay, the actual value of the fuel pressure may be significantly different from (separated from) the target value after the operation state is shifted. Conversely, when the operating state changes from the fuel stop state to the fuel injection state (for example, when the fuel cut operation is ended and the normal operation is started), the same deviation may occur. From the viewpoint of accurately controlling the fuel pressure, it is desirable to prevent such a deviation between the actual value and the target value as much as possible.

  In view of the above problems, the object of the present invention is when the engine operating state shifts from the fuel injection state to the fuel stop state, and when the operation state shifts from the fuel stop state to the fuel injection state. An object of the present invention is to provide a fuel injection control device capable of accurately controlling the fuel pressure.

A fuel injection control device according to the present invention for solving the above-mentioned problems is as follows.
The control unit is applied to an internal combustion engine having an injection valve that injects fuel into a cylinder, and includes a control unit that performs feedback control of a fuel pressure that is a pressure of fuel supplied to the injection valve.

Furthermore, the control unit
When calculating the feedback amount including an integral term based on the time integral value of the deviation between the target value and the actual value of the fuel pressure,
When the engine operating state shifts from the first state in which the injection valve injects fuel to the second state in which the injection valve does not inject fuel, the value of the integral term before the transition is stored and the transition is made Determine the value of the later integral term to be zero,
Thereafter, when the operating state transitions from the second state to the first state, the value of the integral term after the transition is determined as the stored value.
It is configured as follows.

  With the above configuration, when the engine operating state shifts from the fuel injection state (first state) to the fuel stopped state (second state), the value before the transition is not waited for after the elapse of the response delay time of the integral term. Does not require time to gradually change to the appropriate value after the transition), and the value of the integral term is set to “zero”. In general, if the value of the integral term after the transition to the fuel stop state is set to “zero”, the additional fuel supply to the injection valve is stopped immediately after the transition, so the fuel pressure is reduced before and after the transition. An appropriately controlled state is maintained (the actual value does not deviate from the target value). As a result, when the engine operating state shifts from the fuel injection state (first state) to the fuel stop state (second state), the actual value of the fuel pressure is prevented from greatly deviating from the target value.

  Conversely, when the engine operating state shifts from the fuel stop state (second state) to the fuel injection state (first state), the engine does not wait for the response delay time of the integral term to elapse (that is, zero before the transition). Does not require time to gradually change to an appropriate value after the transition), and the value of the integral term is set to the “stored value” in advance. Since the “stored value” is the value of the integral term used in the previous fuel injection state, if the value of the integral term after the transition to the fuel injection state is set to “stored value”, The state in which the fuel pressure is appropriately controlled before and after the transition is maintained (the actual value does not deviate from the target value). As a result, even when the engine operating state shifts from the fuel stop state (second state) to the fuel injection state (first state), the actual value of the fuel pressure is prevented from greatly deviating from the target value.

  Therefore, in the fuel injection control device of the present invention, even when the operation state of the engine shifts from the fuel injection state to the fuel stop state, and when the operation state shifts from the fuel stop state to the fuel injection state, The fuel pressure can be accurately controlled.

  By the way, as a specific method for “feedback control of fuel pressure” in the present invention, for example, the amount of fuel (fuel discharge) discharged by a member (such as a fuel pump) that boosts the fuel in the fuel tank and supplies it to the injection valve (Amount) is a feedback control method. Since the fuel discharged from the member is sealed in the injection valve and the supply path, the fuel pressure can be controlled by controlling the fuel discharge amount. When this method is used, for example, the fuel discharge amount can be calculated as the sum of the fuel amount consumed by the injection valve (fuel consumption amount) and the feedback amount for fuel pressure control.

  Furthermore, the “feedback amount” in the present invention is not only “integral term” but also one of “proportional term” based on deviation between target value and actual value of fuel pressure and “differential term” based on time differential value of the deviation or Both may be included.

1 is a schematic view of a fuel injection control device according to an embodiment of the present invention and an internal combustion engine to which the device is applied. It is the flowchart which showed the routine which CPU of the fuel-injection control apparatus which concerns on embodiment of this invention performs. 3 is a time chart showing an example of a relationship among an operating state of an internal combustion engine, a feedback amount for fuel pressure control, an integral term included in the feedback amount, and an actual value of fuel pressure.

<Embodiment>
Outline of Device FIG. 1 shows a schematic configuration of an internal combustion engine 10 to which a fuel injection control device (hereinafter also referred to as “implementation device”) according to an embodiment of the present invention is applied. The engine 10 is an in-cylinder injection / spark ignition type / four-cycle internal combustion engine.

  The engine 10 includes a fuel injection system (11-15), a cylinder block part (21-25), a cylinder head part (31-38), an intake system (41-44), an exhaust system (51-53), an accelerator pedal ( 61), an ignition key switch (62), various sensors (71 to 73), and an electronic control device 81.

  The fuel injection system includes an injection valve (injector) 11 that injects fuel into a cylinder, a delivery pipe 12 that injects high-pressure fuel into the injection valve 11, a fuel pump 13 that boosts the fuel and sends the fuel to the delivery pipe 12, and a fuel pump 13 And a fuel pressure sensor 15 for measuring the pressure of the fuel in the delivery pipe 12 (hereinafter referred to as “fuel pressure”).

  The fuel pump 13 is an electric pump that operates according to an instruction signal (specifically, duty ratio of the operating voltage) of the electronic control device 81, and boosts the fuel supplied from the fuel tank 14 (the fuel pressure is used as an instruction signal). To match the corresponding fuel pressure). Specifically, the fuel pressure is feedback controlled so that the output value of the fuel pressure sensor 15 (actual value of the fuel pressure) matches a predetermined target value (see also the fuel pressure control routine of FIG. 2). The delivery pipe 12 injects the fuel supplied from the fuel pump 13 into the injection valve 11 while temporarily storing the fuel while maintaining the fuel pressure. The injection valve 11 injects fuel into the cylinder 21 in accordance with an instruction from the electronic control unit 81.

  The cylinder block portion includes a cylinder 21, a piston 22, a connecting rod 23, and a crankshaft 24. The inner wall surface of the cylinder 21, the upper surface of the piston 22, and the lower surface of the cylinder head portion define a combustion chamber 25. The cylinder head includes an intake port 31 communicating with the combustion chamber 25, an intake valve 32 for opening and closing the intake port 31, an intake camshaft 33 for driving the intake valve 32, an exhaust port 34 communicating with the combustion chamber 25, and an exhaust port 34. It has an exhaust valve 35 that opens and closes, an exhaust camshaft 36 that drives the exhaust valve 35, an ignition plug 37, and an igniter 38 that generates a high voltage applied to the ignition plug 37.

  The intake system includes an intake manifold 41 connected to each cylinder via an intake port 31, an intake pipe 42 connected to the intake manifold 41, an air cleaner 43 provided at an end of the intake pipe 42, and an opening area of the intake pipe 42. And a throttle valve actuator 44a that rotationally drives the throttle valve 44 in response to an instruction signal. The exhaust system has an exhaust manifold 51 connected to each cylinder via an exhaust port 34, an exhaust pipe 52 connected to the exhaust manifold 51, and an exhaust gas purification catalyst 53 provided in the exhaust pipe 52. Yes.

  The accelerator pedal 61 is operated by an operator of the engine 10 in response to an output request to the engine 10 or the like. The ignition key switch 62 is operated by an operator of the engine 10 when starting the engine 10. As various sensors, the engine 10 includes a cam position sensor 71, a crank position sensor 72, and a water temperature sensor 73.

  The electronic control device 81 is an electronic circuit mainly composed of a known microcomputer including a CPU, a ROM, a RAM, and the like. A CPU (hereinafter simply referred to as “CPU”) of the electric control device is configured to transmit an instruction signal to the injection valve 11 and the fuel pump 13 and the like and to receive a signal output from each of the sensors. .

Device Operation In the execution device, the CPU executes the “fuel pressure control routine” shown in FIG. 2 and controls the fuel pressure by adjusting the amount of fuel discharged from the fuel pump.

  Specifically, the CPU executes the routine of FIG. 2 every time a predetermined time elapses. When the processing of this routine is started, the CPU proceeds from step 200 to step 205, specifies the operating state of the engine 10 with reference to the output values of the various sensors 71 to 73 described above, and the current time based on the operating state. A fuel pressure target value FPtgt (t) at (time t) is set.

  Next, the CPU proceeds to step 210, acquires the actual value FPact (t) of the current fuel pressure based on the output value of the fuel pressure sensor 15, and the deviation between the target value FPtgt (t) and the actual value FPact (t). ΔFP (t) is calculated. Further, the CPU proceeds to step 215 and multiplies the deviation ΔFP (t) by a predetermined gain Kp to calculate the “proportional term FBp (t)” of the current feedback amount for fuel pressure control. The gain Kp is an appropriate value determined by a prior experiment or the like, and is stored in the ROM.

  Next, the CPU proceeds to step 220 to determine “whether the control status at the present time (time t) is the fuel injection state or not”. The control status is an index representing the operating state of the engine 10, and the same applies to the state in which fuel is injected from the injection valve 11 (fuel injection state) and the state in which fuel is not injected from the injection valve 11 (fuel stop state). Included in the indicator. For example, when the engine 10 is operating normally, the control status is set to “fuel injection state”. On the other hand, when the engine 10 is in fuel cut operation, the control status is set to “fuel stop state”.

  For example, when the normal operation is continuously performed at the present time, the control status is the fuel injection state, so the CPU determines “Yes” in step 220 and proceeds to step 225. In step 225, the CPU determines whether or not the current time is immediately after the control status shifts from the fuel stop state to the fuel injection state. Specifically, the CPU compares the control status at the present time (time t) with the control status at the time when this routine was last executed (time t-1), thereby changing the control status (control status). To see how it changed.

  When the normal operation is continued as described above, since the control status is maintained in the fuel injection state, the CPU makes a “No” determination at step 225 to proceed to step 230. In step 230, the CPU multiplies a value obtained by time-integrating the deviation ΔFP (t) (integral value from the integration start time τ = 0 to the current time τ = t) by a predetermined gain Ki according to the following equation (1). Thus, the “integral term” FBi (t) of the feedback amount for fuel pressure control is calculated. The gain Kp is an appropriate value determined by a prior experiment or the like, and is stored in the ROM.

    FBi (t) = Ki · ∫ΔFP (τ) dτ [τ = 0, t] (1)

  Next, the CPU proceeds to step 235, and multiplies the sum of the proportional term FBp (t) and the integral term FBi (t) by a predetermined coefficient Kfb according to the following equation (2) to thereby provide a feedback amount for fuel pressure control. Ffb (t) is calculated. That is, the execution apparatus performs proportional / integral control (PI control) on the fuel pressure. The coefficient Kfb is a coefficient for converting the proportional term FBp (t) and the integral term FBi (t) calculated as the value of “fuel pressure” into “fuel discharge amount” from the fuel pump 13. The coefficient Kfb is determined by a prior experiment or the like and stored in the ROM.

    Ffb (t) = Kfb · (FBp (t) + FBi (t)) (2)

  Next, the CPU proceeds to step 240, and adds the feedback amount Ffb (t) to the fuel amount (fuel consumption amount) Finj (t) injected from the injection valve 11 and consumed, thereby obtaining the fuel from the fuel pump 13. A discharge amount Fout (t) is calculated. The fuel consumption amount Finj (t) is determined by applying the current operating state of the engine 10 to another routine (not shown) for determining the fuel consumption amount. The fuel discharge amount Fout (t) is a value greater than or equal to zero.

  Next, the CPU proceeds to step 245 and transmits an instruction signal to the fuel pump 13 so as to discharge the fuel with the fuel discharge amount Fout (t). Specifically, the CPU specifies a “duty ratio of the operating voltage of the fuel pump 13 corresponding to the fuel discharge amount Fout (t)” with reference to a map or the like stored in the ROM, and operates the duty ratio. An instruction to apply a working voltage to the fuel pump 13 is transmitted to a controller (so-called FPC, Fuel Pump Controller, not shown) that operates the fuel pump 13.

  Thereafter, the CPU proceeds to step 295 to end the present routine tentatively.

  On the other hand, when the process of step 220 is performed immediately after the fuel cut operation is started, the CPU makes a “No” determination at step 220 to proceed to step 250. In step 250, the CPU determines “whether or not the current time point is immediately after the control status shifts from the fuel injection state to the fuel stop state”. Specifically, the CPU compares the control status at the present time (time t) with the control status at the time when this routine was last executed (time t-1), thereby changing the control status (control status). To see how it changed.

  When the fuel cut operation is started as described above, since the control status is immediately after the fuel injection state is shifted to the fuel stop state, the CPU makes a “Yes” determination at step 250 to proceed to step 255. In step 255, the CPU stores the value of the integral term FBi (t-1) at the time (time t-1) when this routine was last executed as a stored value FBstr in the RAM. Thereafter, the CPU proceeds to step 260 to set the value of the integral term FBi (t) to zero. That is, the CPU resets the value of the integral term FBi (t). Note that the actual value FPact (t) of the fuel pressure before the fuel cut operation is started (before the transition of the control status) is normally maintained in the vicinity of the target value FPtgt (t). Therefore, the value of the proportional term FBp (t) at the present time is also a value near zero.

  Thereafter, the CPU performs the processing from step 235 to step 245 to calculate the fuel discharge amount Fout (t) and give a discharge instruction. The fuel consumption Finj (t) in the fuel stop state is zero, the value of the integral term FBi (t) at the present time is zero, and the value of the proportional term FBp (t) is also substantially zero. The discharge amount Fout (t) is substantially zero. As a result, even when the control status shifts from the fuel injection state to the fuel stop state (when the fuel cut operation is started as in this example), the actual value FPact (t) of the fuel pressure becomes the target value FPtgt ( Deviation from t) is prevented.

  If this routine is executed again during the period in which the fuel cut operation is continued, the CPU makes a “No” determination at step 250 to proceed to step 230 via the connection indicator A. Then, the integral term FBi (t) is determined in step 230 as in the normal operation, and an instruction signal is transmitted to the fuel pump 13 in steps 235 to 245. However, since the fuel does not substantially flow in the delivery pipe 12 during the fuel cut operation, the value of the integral term FBi (t) is substantially maintained at zero. From this point of view, the value of the integral term FBi (t) may be continuously updated to zero during execution of the fuel cut operation.

  Thereafter, when step 220 is executed immediately after the fuel cut operation is stopped and the normal operation is started, the CPU makes a “Yes” determination at step 220 and step 225 to proceed to step 265. In step 265, the CPU sets the value of the integral term FBi (t) to the stored value FBstr. That is, the CPU reads (reads) the value of the integral term FBi (t) from the RAM, and resets it to the value before execution of the fuel cut operation.

  Thereafter, the CPU executes the processing of step 235 to step 250 to calculate the fuel discharge amount Fout (t) and give a discharge instruction. Since the stored value FBstr is an appropriate value used as the proportional term FBp before the execution of the fuel cut operation, the fuel discharge amount Fout (t) is set to an appropriate value from the viewpoint of fuel pressure control. As a result, even when the control status shifts from the fuel stop state to the fuel injection state (for example, when the fuel cut operation ends), the actual value FPact (t) of the fuel pressure is quickly changed to the target value FPtgt (t). And the actual value FPact (t) of the fuel pressure is prevented from deviating from the target value FPtgt (t).

Actual Practical Example With reference to the time chart shown in FIG. 3, the transition of the fuel pressure when the implementation apparatus actually performs the fuel pressure control will be described.

  Specifically, the engine 10 is normally operated at time t0 in FIG. 3 (that is, the control status is the fuel injection state). Therefore, an amount of fuel based on the fuel consumption Finj (t0) and the feedback amount Ffb (t0) corresponding to the operating state of the engine 10 is discharged from the fuel pump 13, and the actual value FPact (t) of the fuel pressure is equal to the target value FPtgt. The value is in the vicinity. The magnitude of the integral term FBi (t0) at time t0 is a value in the vicinity of the predetermined value FBi0 that is determined based on individual differences of the fuel pump 13 and aging deterioration. In this example, the predetermined value FBi0 is a positive value.

  Thereafter, when the fuel cut operation is started at time t1 (that is, when the control status shifts from the fuel injection state to the fuel stop state), the execution device calculates the fuel consumption Finj (t1) at time t1. Set to zero. Furthermore, the implementation apparatus stores the value of the integral term FBi (t1-1) at the immediately previous time t1-1 in the RAM as the stored value FBstr, and sets the integral term FBi (t1) to zero. Note that the value of the stored value FBstr is a value in the vicinity of the predetermined value FBi0.

  As a result, the fuel is excessively injected due to the response delay of the integral term FBi (specifically, fuel is continuously injected from the fuel pump 13 to the delivery pipe 12 even though the fuel is not injected from the injection valve 11). Therefore, the actual value FPact (t1) of the fuel pressure is maintained in the vicinity of the target value FPtgt even after the time t1. Note that the actual value FPact (t1) of the fuel pressure is maintained in the vicinity of the target value FPtgt, so that the value of the proportional term FBp (not shown) is also maintained in the vicinity of zero. Therefore, the feedback amount Ffb (t1) after time t1 is a value near zero.

  Thereafter, at time t2, when the fuel cut operation is finished and the normal operation is started (that is, when the control status shifts from the fuel stop state to the fuel injection state), the execution apparatus performs the fuel consumption amount Finj (t2). Is set to a value corresponding to the operating state, and the stored value FBstr (≈FBi0) is set to the integral term FBi (t2). As a result, under-injection due to a delay in response of the integral term FBi (specifically, a sufficient amount of fuel is not injected from the fuel pump 13 into the delivery pipe 12 even though the fuel is injected from the injection valve 11). Therefore, the actual value FPact (t2) of the fuel pressure is maintained in the vicinity of the target value FPtgt even after time t2.

  Note that since the fuel does not substantially flow in the delivery pipe 12 from the time t1 to the time t2, the value of the integral term FBi (t) is substantially maintained at zero.

  As described above, the execution apparatus is configured to change the control status of the engine 10 from the fuel injection state to the fuel stop state (when the fuel cut operation is started) and change the control status from the fuel stop state to the fuel injection state. Even in the case of transition (when normal operation is resumed), the fuel pressure FPact (t) can be made to coincide with the target value FPtgt (t) with high accuracy.

<Summary of Embodiment>
As described above, the fuel injection control device (implementation device) according to the embodiment of the present invention is
A control unit (electronic control unit) 81 that is applied to the internal combustion engine 10 having the injection valve 11 that injects fuel into the cylinder and feedback-controls the fuel pressure FPact that is the pressure of the fuel supplied to the injection valve 11 is provided.

  When the control unit 81 calculates the feedback amount Ffb including the integral term FBi based on the time integral value of the deviation ΔFP between the target value FPtgt of the fuel pressure and the actual value FPact (step 235), the injection valve 11 injects fuel. When the operating state of the engine 10 shifts from the first state (normal operation) to the second state (fuel cut operation) in which the injector 11 does not inject fuel, the integral term value FBstr before the transfer is stored ( In step 255), the value of the integral term FBi after the transition is determined to be zero (step 260), and when the operating state transitions from the second state to the first state thereafter, the value of the integral term FBi after the transition is determined. The stored value FBstr is determined (step 265).

<Other aspects>
The present invention is not limited to the above embodiment, and various modifications can be employed within the scope of the present invention. For example, the implementation apparatus may employ proportional / integral / derivative control (PID control) instead of proportional / integral control (PI control) as a method for feedback control of the fuel pressure.

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Injection valve, 12 ... Delivery pipe, 13 ... Fuel pump, 14 ... Fuel tank, 15 ... Fuel pressure sensor, 81 ... Electronic control apparatus

Claims (1)

A fuel injection control device that is applied to an internal combustion engine having an injection valve that injects fuel into a cylinder and includes a control unit that feedback-controls a fuel pressure that is a pressure of fuel supplied to the injection valve,
The controller is
When calculating the feedback amount including an integral term based on the time integral value of the deviation between the target value and the actual value of the fuel pressure,
When the engine operating state shifts from the first state in which the injection valve injects fuel to the second state in which the injection valve does not inject fuel, the value of the integral term before the transition is stored and the transition is made Determine the value of the later integral term to be zero,
Thereafter, when the operating state transitions from the second state to the first state, the value of the integral term after the transition is determined as the stored value.
A fuel injection control device for an internal combustion engine.

Images