Vehicle control device

Abstract

To provide a vehicle control device capable of suppressing unnecessary change of output transmitted from an internal combustion engine to a torque converter (hydraulic power transmission) during execution of backlash reduction control in a vehicle that executes the backlash reduction control for temporarily reducing a fuel injection amount in order to avoid rattling noise caused by backlash of a gear mechanism when a vehicle is switched from a driven state to a driving state.SOLUTION: During execution of backlash reduction control, a control section (5) of a vehicle control device executes injection amount correction processing for determining a fuel injection amount (Qfin) of a fuel injection valve (25) on the basis of a correction injection amount that becomes larger as differential rotation between rotating speed (NE) on an internal combustion engine (21) and rotating speed (NT) of a driving wheel (12a-12b) side in a hydraulic power transmission (22) becomes smaller.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device, and more particularly to a vehicle control device that is applied to a vehicle having a fluid transmission device disposed in a torque transmission path between an internal combustion engine and drive wheels. [Background technology]

[0002] There are known vehicles in which a gear mechanism is disposed (interposed) in a torque transmission path from an internal combustion engine, which is a driving force source, to the drive wheels. The gear mechanism includes, for example, a torque converter, which is a fluid transmission, a transmission, and a differential gear. In the torque converter, a difference (differential rotation) can occur between the rotation speed of the internal combustion engine side (i.e., engine rotation speed) and the rotation speed of the drive wheels side (i.e., turbine rotation speed).

[0003] When the internal combustion engine is generating torque to accelerate the vehicle (i.e., when the vehicle is in a driving state), the differential rotation speed is generally a positive value, i.e., the engine rotation speed is greater than the turbine rotation speed. On the other hand, when the vehicle is running and the internal combustion engine is not generating sufficient torque (i.e., when the vehicle is in a driven state), the differential rotation speed is generally a negative value.

[0004] When a vehicle switches from a driven state to a driving state, backlash in the gear mechanism can cause a discontinuous change in the vehicle's acceleration (so-called rattle or tip-in shock). Therefore, rattle elimination control has been proposed to suppress the occurrence of rattle. For example, according to a vehicle control device (conventional device) described in Patent Document 1, the output (engine output) of the internal combustion engine is reduced when the vehicle switches from a driven state to a driving state, and then the engine output is gradually increased to perform rattle elimination control. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-68046 Summary of the Invention [Problem to be solved by the invention]

[0006] In many cases, the torque transmission path described above is provided with accessories (for example, an alternator that generates electric power and a hydraulic pump of a power steering device) to which the torque of the internal combustion engine is transmitted. That is, the output of the internal combustion engine is transmitted to the drive wheels and also to the accessories. The engine output transmitted to the accessories (i.e., the energy of the engine output transmitted to the accessories) is hereinafter also referred to as the "accessory load."

[0007] A change in the accessory load may cause a change in the power output transmitted to the drive wheels (more specifically, the power output transmitted from the internal combustion engine to the torque converter, hereinafter also referred to as the "drive load"). In particular, if the accessory load changes while backlash elimination control, which temporarily reduces the engine power, is being executed, the change in the drive load may become larger than when backlash elimination control is not being executed, which may cause discomfort to the vehicle occupants.

[0008] The present invention has been devised in view of the above points, and one of its objects is to provide a vehicle control device that can suppress unnecessary changes in the drive load while backlash elimination control is being executed. [Means for solving the problem]

[0009] In order to solve the above problem, the vehicle control device of the first invention of the present invention is a vehicle control device applied to a vehicle having an internal combustion engine including a fuel injection valve and a fluid transmission device arranged in a torque transmission path between the internal combustion engine and a drive wheel, and has a control unit that performs backlash elimination control to temporarily reduce the fuel injection amount of the fuel injection valve below the required injection amount corresponding to the acceleration requested by the vehicle occupant when the vehicle switches from a driven state to a drive state, and the control unit performs an injection amount correction process to obtain the fuel injection amount based on a corrected injection amount that becomes larger as the differential rotation between the internal combustion engine side and the drive wheel side in the fluid transmission device becomes smaller while the backlash elimination control is being performed.

[0010] A second aspect of the present invention is a vehicle control device according to the first aspect of the present invention, wherein the control unit increases the fuel injection amount by the sum of a first increase amount and the corrected injection amount every time a predetermined time elapses while the injection amount correction process is being executed.

[0011] A third aspect of the present invention is a vehicle control device according to the first aspect of the present invention, wherein the control unit executes at least one of a process of acquiring the corrected injection amount so that the accumulated value of the corrected injection amount does not exceed an accumulated upper limit amount, and a process of acquiring the corrected injection amount so that the accumulated value does not exceed an accumulated lower limit amount.

[0012] A fourth aspect of the present invention is a vehicle control device according to the second aspect of the present invention, wherein the control unit increases the fuel injection amount by a second increase amount greater than the first increase amount every time the predetermined time elapses while the backlash elimination control is being executed and after the injection amount correction process has been executed.

[0013] A fifth aspect of the present invention is the vehicle control device according to the first aspect, wherein the vehicle has an auxiliary device that is operated by the output of the internal combustion engine. [Effects of the Invention]

[0014] In the first aspect of the present invention, when the differential rotation speed changes due to a change in the driving load, the correction injection amount acquired in accordance with the change in the differential rotation speed is reflected in the fuel injection amount. That is, according to the first aspect of the present invention, the change in the driving load during execution of backlash elimination control is suppressed by adjusting the fuel injection amount based on the correction injection amount.

[0015] In the second aspect of the present invention, the fuel injection amount is acquired based on the first increment (i.e., the feedforward value) and the corrected injection amount (i.e., the feedback value). That is, the first increment is reflected in the fuel injection amount, so that the drive load can be gradually increased. Furthermore, if an unexpected change in the drive load occurs, the fuel injection amount is compensated for by the corrected injection amount. Therefore, according to the second aspect of the present invention, the drive load (and therefore the differential rotation) can be accurately controlled.

[0016] In the third aspect of the present invention, an upper limit and / or a lower limit is set for the integrated value of the correction injection amount. Therefore, when a change in the driving load cannot be compensated for by the correction injection amount for some reason, the correction injection amount is prevented from becoming too large or too small. In other words, according to the third aspect of the present invention, a sudden increase or decrease in the engine speed can be suppressed when the reason preventing the correction injection amount from compensating for the driving load is resolved.

[0017] According to the fourth aspect of the present invention, after the injection amount correction process is performed, the fuel injection amount increases according to the second increment, which is greater than the first increment. That is, the rate at which the fuel injection amount increases increases. This makes it possible to quickly bring the fuel injection amount closer to the required injection amount while suppressing the occurrence of abnormal noise, vibration, and the like, which may be caused by the backlash of the gear mechanism not being sufficiently eliminated during the injection amount correction process.

[0018] According to the fifth aspect of the present invention, even if the engine output transmitted to the accessories (i.e., the accessory load) changes, a corrected injection amount is acquired and reflected in the fuel injection amount in accordance with a change in the differential rotation caused by the change in the accessory load (more specifically, a change in the engine rotation speed). Therefore, according to the fifth aspect of the present invention, even if a change in the accessory load occurs, it is possible to suppress a change in the engine rotation speed. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram (cross-sectional view) of a vehicle according to an embodiment of a vehicle control device. [Figure 2] 1 is a time chart showing an example of changes in (A) accelerator operation amount, (B) engine rotation speed and turbine rotation speed, (C) required injection amount and fuel injection amount, and (D) acceleration of a vehicle. [Figure 3] 10 is an example of a map showing the relationship between differential rotation and corrected injection amount. [Figure 4] 6 is a graph showing an example of changes in the correction injection amount, the integrated correction amount, and the upper limit correction amount. [Figure 5] 4 is a flowchart showing an "injection amount acquisition processing routine" executed by a control unit of the vehicle control device. [Figure 6] 10 is a flowchart showing a "first smoothing processing routine" executed by the control unit. [Figure 7] 10 is a flowchart showing a "second smoothing processing routine" executed by the control unit. DETAILED DESCRIPTION OF THE INVENTION

[0020] An embodiment of the present invention will be described with reference to the drawings. The same symbols (reference numbers) in the description refer to the same elements having the same functions, although duplicated descriptions will not be given. The vehicle control device according to this embodiment is applied to a vehicle 1 shown in FIG.

[0021] The vehicle 1 includes steered wheels 11a-11b, which are front wheels, and drive wheels 12a-12b, which are rear wheels. In addition, the vehicle 1 includes a powertrain system 2, a steering system 4, and an ECU 5. The powertrain system 2 includes an internal combustion engine 21, a torque converter 22, a transmission 23, and a differential gear 24. The powertrain system 2 forms a torque transmission path (power transmission path) between the internal combustion engine 21 and the drive wheels 12a-12b.

[0022] The internal combustion engine 21 and the torque converter 22 are connected to each other by a crankshaft 31 so as to be able to transmit torque between them. The torque converter 22 and the transmission 23 are connected to each other by a turbine shaft 32 so as to be able to transmit torque between them. The transmission 23 and the differential gear 24 are connected to each other by a propeller shaft 33 so as to be able to transmit torque between them. The differential gear 24 and the driving wheels 12a to 12b are connected to each other by drive shafts 34a to 34b so as to be able to transmit torque between them.

[0023] The internal combustion engine 21 is a compression-ignition multi-cylinder diesel engine. A fuel injection valve 25 is disposed in each of the cylinders (combustion chambers) formed in the internal combustion engine 21. High-pressure fuel is supplied to the fuel injection valve 25 from an accumulator chamber (not shown) of a common rail device. The fuel injection valve 25 injects fuel into the combustion chamber in response to instructions from the ECU 5. The internal combustion engine 21 generates torque to rotate a crankshaft 31 by burning the fuel injected by the fuel injection valve 25. The rotational speed of the crankshaft 31 (i.e., the rotational speed of the internal combustion engine 21 side of the torque converter 22) is also referred to as engine rotational speed NE.

[0024] The torque converter 22 is one of the fluid power transmission devices and includes a pump impeller 22a and a turbine runner 22b. The pump impeller 22a is connected to the crankshaft 31. The turbine runner 22b is connected to the turbine shaft 32. The operating state of the torque converter 22 is switched between a "torque connected state" and a "torque disconnected state" in response to an instruction from the ECU 5.

[0025] The torque connection state is a state in which torque is transmitted between the pump impeller 22a and the turbine runner 22b by hydraulic oil (i.e., torque converter oil) filled in the torque converter 22. The torque interruption state is a state in which torque is not transmitted between the pump impeller 22a and the turbine runner 22b. The rotational speed of the turbine shaft 32 (i.e., the rotational speed of the torque converter 22 on the side of the drive wheels 12a-12b) is also referred to as the turbine rotational speed NT.

[0026] The transmission 23 changes the gear ratio (specifically, the ratio of the turbine rotation speed NT to the rotation speed of the propeller shaft 33) in response to an instruction from the ECU 5. The differential gear 24 absorbs the difference in rotation speed (i.e., differential) between the drive shafts 34a to 34b.

[0027] The steering system 4 is a hydraulic power steering mechanism and includes a steering wheel 41, a steering gear box 42, a hydraulic pump 43, a reservoir tank 44, and a control valve 45.

[0028] The steering wheel 41 is connected to a steering gear box 42 via a steering shaft 46. The steering gear box 42 displaces tie rods 47a to 47b in response to the rotation of the steering wheel 41, thereby changing the steering angle of the steered wheels 11a to 11b.

[0029] The hydraulic pump 43 is operated by torque transmitted from the crankshaft 31 via a drive belt 48. That is, the hydraulic pump 43 is operated by the output (auxiliary load) transmitted from the internal combustion engine 21. The hydraulic pump 43 pumps hydraulic oil (i.e., power steering oil) stored in a reservoir tank 44 to a control valve 45.

[0030] The hydraulic oil supplied to the control valve 45 is supplied to the steering gear box 42. The control valve 45 switches the flow direction of the hydraulic oil in the steering gear box 42 according to the rotation direction of the steering wheel 41. The steering gear box 42 uses the pressure of the hydraulic oil supplied from the control valve 45 to assist the steering torque input to the steering wheel 41 by the driver.

[0031] The ECU 5 is an electronic control unit (control device, control section) that includes a CPU, ROM, RAM, and EEPROM. The CPU sequentially executes a predetermined program to read data, perform numerical calculations, and output the calculation results. The ROM stores the programs executed by the CPU and maps (look-up tables), etc. The RAM temporarily stores data referenced by the CPU. The EEPROM stores data referenced by the CPU and furthermore, retains the stored data even when the ECU 5 stops operating.

[0032] Furthermore, the ECU 5 is connected to a crank angle sensor 61, a cam position sensor 62, a turbine rotation speed sensor 63, and an accelerator operation amount sensor 64. The crank angle sensor 61 outputs a pulse signal to the ECU 5 every time the crankshaft 31 rotates by a predetermined angle. The cam position sensor 62 outputs a signal corresponding to the rotation position of a camshaft (not shown) of the internal combustion engine 21 to the ECU 5.

[0033] The ECU 5 acquires the engine rotation speed NE based on the signal input from the crank angle sensor 61. In addition, the ECU 5 acquires the crank angle CA of each cylinder in the internal combustion engine 21 based on the signals input from the crank angle sensor 61 and the cam position sensor 62.

[0034] The turbine rotation speed sensor 63 detects the turbine rotation speed NT (i.e., the rotation speed of the turbine shaft 32) and outputs a signal representing the turbine rotation speed NT to the ECU 5. The accelerator operation amount sensor 64 detects the accelerator operation amount Accp, which is the operation amount (depression amount) of the accelerator pedal 65, and outputs a signal representing the accelerator operation amount Accp to the ECU 5. When the accelerator pedal 65 is not operated (i.e., the accelerator is not operated), the accelerator operation amount Accp is "0".

[0035] In addition, the vehicle 1 includes auxiliary equipment (e.g., an alternator and a compressor for the in-vehicle air conditioning) that operates using output transmitted from the internal combustion engine 21, similar to the hydraulic pump 43, but illustrations and descriptions of these auxiliary equipment are omitted.

[0036] The ECU 5 acquires the required injection amount Qgov by applying the accelerator operation amount Accp, the engine rotation speed NE, etc. to a pre-adapted map (required injection amount map) every time a predetermined processing period Δt (predetermined time) elapses while the vehicle 1 is traveling. In other words, the required injection amount Qgov is acquired according to the acceleration of the vehicle 1 requested by the driver.

[0037] If backlash-eliminating control, which will be described later, is not being executed, the ECU 5 sets the fuel injection amount Qfin to a value equal to the required injection amount Qgov. When the crank angle CA of a certain cylinder reaches a predetermined fuel injection angle, the ECU 5 causes the fuel injection valve 25 of that cylinder to inject fuel equivalent to the fuel injection amount Qfin in multiple injections. That is, the ECU 5 executes a well-known multi-injection including a pilot injection and a main injection. The larger the fuel injection amount Qfin, the greater the output (engine power) of the internal combustion engine 21.

[0038] (backlash control) The ECU 5 executes "backlash reduction control" when the traveling state of the vehicle 1 switches from the "driven state" to the "driving state." The driving state is a state in which torque generated by the internal combustion engine 21 is transmitted to the driving wheels 12a to 12b. In this case, the differential rotation speed dN, which is the difference between the engine rotation speed NE and the turbine rotation speed NT, is generally a positive value (i.e., dN=NE-NT>0).

[0039] In the driven state, the output of the internal combustion engine 21 is small or "0", and therefore torque is transmitted from the drive wheels 12a to 12b to the internal combustion engine 21. More specifically, in the driven state, the inertial force acting on the traveling vehicle 1 becomes torque that rotates the drive wheels 12a to 12b, and this torque is transmitted to the internal combustion engine 21. In this case, the differential rotation dN generally takes a negative value (i.e., dN<0).

[0040] When the running state of the vehicle 1 switches from a driven state to a driving state, rattles (i.e., discontinuous changes in the acceleration of the vehicle 1, as well as abnormal noise and vibrations) may occur due to backlash in the gear mechanisms included in the transmission 23 and the differential gear 24. Therefore, the ECU 5 executes rattle elimination control to suppress the occurrence of rattles.

[0041] The backlash elimination control is a process of reducing the fuel injection amount Qfin below the required injection amount Qgov and then gradually increasing it to the required injection amount Qgov. More specifically, when the backlash elimination control is performed, the fuel injection amount Qfin is adjusted so that the differential rotation speed dN is maintained near a predetermined reference differential rotation speed dNrf. The reference differential rotation speed dNrf is a positive and relatively small value. When the differential rotation speed dN matches the reference differential rotation speed dNrf, a relatively small torque is transmitted from the internal combustion engine 21 to the drive wheels 12a to 12b. This gradually eliminates backlash (backlash).

[0042] The ECU 5 starts backlash elimination control when the following conditions (a) and (b) are both met. Condition (a): The differential rotation dN is a negative value (i.e., dN < 0). Condition (b): The required injection quantity Qgov has become greater than a predetermined first reference injection quantity Qr1.

[0043] When executing the backlash elimination control, the ECU 5 executes "first limit processing", "second limit processing", "first smoothing processing", and "second smoothing processing" in this order. The first limit processing is a process of maintaining the fuel injection quantity Qfin at the first reference injection quantity Qr1. The second limit processing is a process of maintaining the fuel injection quantity Qfin at a predetermined second reference injection quantity Qr2. The second reference injection quantity Qr2 is smaller than the first reference injection quantity Qr1 (i.e., Qr2 < Qr1). Each of the first smoothing processing and the second smoothing processing is a process of gradually increasing the fuel injection quantity Qfin. When the fuel injection quantity Qfin reaches the required injection quantity Qgov during the execution of the second smoothing processing, the ECU 5 ends the backlash elimination control. The first smoothing processing is also referred to as "injection quantity correction processing" for convenience.

[0044] (Backlash Elimination Control - Time Chart) A specific explanation will be given while referring to the example of FIG. 2. During the period shown in FIG. 2, the torque converter 22 is in a torque connection state, and the gear ratio of the transmission 23 is not changed. At time t0, as shown by the solid line L1, the accelerator operation amount Accp is "0". In addition, as understood from the solid line L2a representing the engine rotational speed NE and the broken line L2b representing the turbine rotational speed NT, the turbine rotational speed NT is greater than the engine rotational speed NE. That is, the vehicle 1 is in a driven state, and the differential rotation dN is a negative value.

[0045] At time t1, the accelerator operation amount Accp starts to increase (refer to the solid line L1). Along with this, as shown by the broken line L3a, the required injection quantity Qgov increases. At this time, since the backlash elimination control is not being executed, the fuel injection quantity Qfin is set to the same value as the required injection quantity Qgov. Therefore, as shown by the solid line L3b, the fuel injection quantity Qfin increases together with the required injection quantity Qgov.

[0046] After that, at time t2, the required injection amount Qgov reaches the first reference injection amount Qr1. That is, the condition (b) is satisfied. Since the condition (a) is already satisfied, the ECU 5 starts the backlash-reducing control (more specifically, the first limitation process) at time t2. Therefore, after time t2 (until time t3), the fuel injection amount Qfin is maintained at the first reference injection amount Qr1 (which is smaller than the required injection amount Qgov) (see the solid line L3b).

[0047] When the differential speed dN becomes larger than a predetermined differential speed threshold dNth while the first limiting process is being executed, the ECU 5 ends the first limiting process and starts the second limiting process. The differential speed threshold dNth is a negative value (i.e., dNth<0). In FIG. 2, the differential speed dN reaches the differential speed threshold dNth at time t3. In other words, the engine rotation speed NE increases, and the magnitude of the difference with the turbine rotation speed NT (i.e., |dN|) becomes smaller. Therefore, the ECU 5 ends the first limiting process at time t3 (and starts the second limiting process). The condition that is met when the differential speed dN becomes larger than the differential speed threshold dNth while the first limiting process is being executed is also referred to as the "start condition of the second limiting process."

[0048] By executing the second limiting process, the fuel injection amount Qfin is maintained at the second reference injection amount Qr2 after time t3 (until time t4). As a result, the engine speed NE, which had been increasing until time t3, stops increasing and gradually decreases. Therefore, the differential speed dN is maintained near the reference differential speed dNrf.

[0049] After starting the second restriction process, when a predetermined first time threshold Tth1 has elapsed, the ECU 5 ends the second restriction process and starts the first smoothing process. In FIG. 2, the time when the first time threshold Tth1 has elapsed since time t3 is time t4. Therefore, the ECU 5 ends the second restriction process and starts the first smoothing process at time t4. The condition that is met when the first time threshold Tth1 has elapsed after starting the second restriction process is also referred to as the "start condition of the first smoothing process."

[0050] During the execution of the first smoothing process, the ECU 5 acquires the fuel injection amount Qfin every time a processing period Δt elapses, based on the previous fuel injection amount Qfinp, a predetermined first increment Qsm1, and the corrected injection amount Qfb. Specifically, the ECU 5 acquires the fuel injection amount Qfin by adding the first increment Qsm1 and the corrected injection amount Qfb to the previous fuel injection amount Qfinp (i.e., Qfin←Qfinp+Qsm1+Qfb). The previous fuel injection amount Qfinp is the fuel injection amount Qfin acquired by the ECU 5 at a timing that is the processing period Δt earlier than the current time. In other words, the fuel injection amount Qfin increases by the sum of the first increment Qsm1 and the corrected injection amount Qfb compared to the timing that is the processing period Δt earlier.

[0051] The ECU 5 obtains the corrected injection amount Qfb by applying the differential rotation speed dN to the relationship (corrected injection amount map) between the differential rotation speed dN and the corrected injection amount Qfb shown in Fig. 3. The relationship shown in Fig. 3 is adapted in advance and stored in the EEPROM of the ECU 5. As can be seen from Fig. 3, the smaller the differential rotation speed dN, the larger the corrected injection amount Qfb.

[0052] The corrected injection amount Qfb is included in the range from "0" to the injection amount Qfbmx. When the differential rotation dN becomes smaller than the rotation speed Na, the corrected injection amount Qfb is set to the injection amount Qfbmx. When the differential rotation dN becomes larger than the rotation speed Nb, the corrected injection amount Qfb is set to "0". In other words, when the differential rotation dN is smaller than the rotation speed Nb, the corrected injection amount Qfb is set to a positive value and is reflected in the fuel injection amount Qfin.

[0053] In this embodiment, the rotation speed Na is "0", but the rotation speed Na may be a value other than "0". In addition, the rotation speed Nb is equal to the reference differential rotation dNrf, but the rotation speed Nb may be a value other than the reference differential rotation dNrf.

[0054] Furthermore, when the corrected injection amount Qfb exceeds the upper limit correction amount Qmxgd, the ECU 5 executes an "upper limit guard process" that sets the corrected injection amount Qfb to "0" thereafter (until the first smoothing process is completed). The upper limit correction amount Qmxgd is the difference between a predetermined integrated upper limit amount sQmax (upper limit value) and the integrated correction amount sQfb (i.e., Qmxgd←sQmax-sQfb). The integrated correction amount sQfb is the integrated value of the corrected injection amount Qfb acquired during the period from the start of the first smoothing process to the timing one processing cycle Δt before. In other words, the integrated correction amount sQfb is the total value of the corrected injection amounts Qfb that have already been reflected in the fuel injection amount Qfin.

[0055] The upper limit correction amount Qmxgd will be specifically described with reference to the example of Fig. 4. In Fig. 4, the corrected injection amount Qfb, the integrated correction amount sQfb, and the upper limit correction amount Qmxgd are respectively represented by broken lines La to Lc. For convenience of explanation, in Fig. 4, the value acquired as the corrected injection amount Qfb is larger than the corrected injection amount Qfb actually acquired by the ECU 5, and therefore the upper limit guard process is started early. In addition, the corrected injection amount Qfb, the integrated correction amount sQfb, and the upper limit correction amount Qmxgd are values ​​that are acquired or changed discretely every time a processing period Δt elapses (i.e., values ​​that should be represented by multiple points in the graph of Fig. 4), but are represented by broken lines La to Lc in Fig. 4 for convenience.

[0056] In the example of FIG. 4, the first smoothing process is started at time ta, and therefore the corrected injection amount Qfb (specifically, the injection amount q1) is acquired for the first time. At time ta, the integrated correction amount sQfb is "0," so the upper limit correction amount Qmxgd is equal to the integrated upper limit amount sQmax. The injection amount q1, which is the corrected injection amount Qfb, is smaller than the upper limit correction amount Qmxgd (i.e., the integrated upper limit amount sQmax) at this time, so the upper limit guard process is not executed. In other words, the injection amount q1 acquired as the corrected injection amount Qfb is reflected in the fuel injection amount Qfin.

[0057] The corrected injection amount Qfb acquired at time tb after the processing cycle Δt has elapsed since time ta is the injection amount q2. At time tb, the integrated correction amount sQfb is equal to the injection amount q1 (acquired as the corrected injection amount Qfb at time ta), so the upper limit correction amount Qmxgd is equal to the difference between the integrated upper limit amount sQmax and the injection amount q1. Even at time tb, the corrected injection amount Qfb (= q2) is smaller than the upper limit correction amount Qmxgd (= sQmax - q1), so the upper limit guard process is not executed.

[0058] Thereafter, the corrected injection amount Qfb is acquired every time a processing cycle Δt elapses, and the cumulative correction amount sQfb increases accordingly. For example, at time tc, the cumulative correction amount sQfb becomes the cumulative amount qs as a result of adding the "corrected injection amount Qfb acquired at a timing that is the processing cycle Δt before time tc" to the cumulative correction amount sQfb. Next, when the processing cycle Δt elapses from time tc and the time reaches time td, the correction injection amount Qfb becomes the injection amount q3. The upper limit correction amount Qmxgd at time td is the difference between the cumulative upper limit amount sQmax and the cumulative amount qs (i.e., the cumulative correction amount sQfb at this time point).

[0059] As can be seen from the broken lines La and Lc, at time td, the corrected injection amount Qfb (= q3) is greater than the upper limit correction amount Qmxgd (= sQmax - qs). Therefore, the ECU 5 executes the upper limit guard process after time td. That is, until the first smoothing process is completed, the ECU 5 sets the corrected injection amount Qfb to "0." In other words, the injection amount q3 acquired as the corrected injection amount Qfb at time td is not reflected in the fuel injection amount Qfin.

[0060] If the corrected injection amount Qfb acquired at time td is reflected in the fuel injection amount Qfin, the integrated correction amount sQfb will increase by the injection amount q3 and exceed the integrated upper limit amount sQmax (see dashed line Ld in FIG. 4). In other words, the ECU 5 executes the upper limit guard process to acquire the corrected injection amount Qfb so that the integrated correction amount sQfb does not exceed the integrated upper limit amount sQmax. Note that the ECU 5 may set the corrected injection amount Qfb to the upper limit correction amount Qmxgd at time td and set the corrected injection amount Qfb to "0" thereafter. Even in this case, the integrated correction amount sQfb is acquired so that it does not exceed the integrated upper limit amount sQmax.

[0061] 2 again, the ECU 5 starts the upper limit guard process at time t5. Therefore, after time t5 (until time t6), the corrected injection amount Qfb is set to "0," and the fuel injection amount Qfin increases by the first increment Qsm1 every time the processing cycle Δt elapses. As a result, in FIG. 2, the slope of the solid line L3b (i.e., the rate of increase in the fuel injection amount Qfin) is angle θa during the period from time t5 to time t6.

[0062] The second smoothing process will now be described. After starting the first smoothing process, when a predetermined second time threshold Tth2 has elapsed, the ECU 5 ends the first smoothing process and starts the second smoothing process. In FIG. 2, the time when the second time threshold Tth2 has elapsed since time t4 is time t6. Therefore, the ECU 5 starts the second smoothing process at time t6 (by ending the first smoothing process). The condition that is met when the second time threshold Tth2 has elapsed after starting the first smoothing process is also referred to as the "start condition for the second smoothing process."

[0063] During the second smoothing process, the ECU 5 acquires the fuel injection amount Qfin by adding a predetermined second increment Qsm2 to the previous fuel injection amount Qfinp (i.e., Qfin←Qfinp+Qsm2). Therefore, after time t6 (until time t8), the fuel injection amount Qfin increases by the second increment Qsm2 every time a processing period Δt elapses. As a result, in FIG. 2, the slope of the solid line L3b is angle θb during the period from time t6 to time t8. The second increment Qsm2 is larger than the first increment Qsm1 (i.e., Qsm2>Qsm1). Therefore, the angle θb is larger than the angle θa (θb>θa).

[0064] After time t4, as a result of the first smoothing process and the second smoothing process being executed, the acceleration As of the vehicle 1 increases as shown by the solid line L4a. Note that the acceleration As shown by the solid line L4a (and the dashed line L4b described later) is based on the detection value of an acceleration sensor (not shown) mounted on the vehicle 1 (in other words, the acceleration felt by the occupants of the vehicle 1).

[0065] (Significance of backlash reduction control - corrected injection amount Qfb) The reason why the corrected injection amount Qfb is acquired and reflected in the fuel injection amount Qfin in the first smoothing process will be described below. The reason why the upper limit guard process is executed (that is, the effect obtained by the upper limit guard process) will be described later.

[0066] If the corrected injection amount Qfb is not reflected in the fuel injection amount Qfin during the execution of the backlash-eliminating control illustrated in FIG. 2, the fuel injection amount Qfin changes after time t4 as shown by the dashed-dotted line L3c. That is, during the period from time t4 to time t6, the fuel injection amount Qfin increases by the first increment Qsm1 every time the processing cycle Δt elapses. Therefore, the slope of the dashed-dotted line L3c during this period is angle θa. In other words, the fuel injection amount Qfin in this case is smaller than the fuel injection amount Qfin shown by the solid line L3b by an amount equivalent to the corrected injection amount Qfb.

[0067] As a result, the engine speed NE changes as shown by the dashed line L2c after time t4. That is, after time t4, the engine speed NE in this case becomes smaller than the engine speed NE shown by the solid line L2a, and there is a period during which the engine speed NE is smaller than the turbine speed NT.

[0068] This decrease in engine speed NE is caused by an increase in the load on the hydraulic pump 43 (i.e., the accessory load). More specifically, the load on the hydraulic pump 43 increases due to the driver's operation of the steering wheel 41 around time t4. Therefore, as shown by the dashed-dotted line L2c, the engine speed NE decreases. In other words, the increase in the accessory load on the hydraulic pump 43 reduces the drive load transmitted from the internal combustion engine 21 to the torque converter 22.

[0069] As a result, the differential rotation speed dN is not maintained in the vicinity of the reference differential rotation speed dNrf. Therefore, the backlash of the gear mechanism in the torque transmission path is not gradually reduced, and the engine rotation speed NE becomes larger than the turbine rotation speed NT at a timing after time t6 (see dashed line L2b and dash-dot line L2c). In this case, as shown by dashed line L4b, the acceleration As fluctuates after time t7.

[0070] More specifically, as a result of the engine speed NE increasing relatively rapidly from a state where it was smaller than the turbine speed NT (exceeding the turbine speed NT), the backlash of the gear mechanism is suddenly eliminated, resulting in a tip-in shock. This causes vibrations (fluctuations) in the rotational speed of the torque transmission path, which then propagate and are reflected at the ends of the torque transmission path (specifically, the differential gear 24, the drive wheels 12a-12b, and the internal combustion engine 21). As a result, a fluctuation in the acceleration As appears at time t7 (i.e., slightly later than the timing at which the engine speed NE decreases). Such a fluctuation in the acceleration As is likely to appear when the acceleration As changes from a negative value to a positive value (see dashed line L4b).

[0071] On the other hand, as described above, when the engine speed NE decreases due to an increase in the auxiliary load (or other factors), the ECU 5 sets the corrected injection amount Qfb to a positive value and reflects it in the fuel injection amount Qfin, thereby suppressing the decrease in the engine speed NE and increasing the possibility that the differential speed dN will be maintained near the reference differential speed dNrf.

[0072] In other words, if there is no decrease in the drive load of the internal combustion engine 21 (for example, an increase in the auxiliary load related to the hydraulic pump 43) when the first smoothing process is performed, the corrected injection amount Qfb is set to "0" or a small value. In addition, even if the corrected injection amount Qfb is not reflected in the fuel injection amount Qfin, the first increment Qsm1 is adapted so that a state is achieved in which the differential rotation speed dN is close to the reference differential rotation speed dNrf if there is no increase in the auxiliary load. Furthermore, if an increase in the auxiliary load occurs during the execution of the first smoothing process, the fuel injection amount Qfin is adjusted (compensated) by the corrected injection amount Qfb.

[0073] (Backlash control - specific operation) Specific operations of the ECU 5 related to backlash elimination control will be described with reference to the flowcharts of Figures 5 to 7. The CPU of the ECU 5 (hereinafter simply referred to as "CPU") executes the "injection amount acquisition processing routine" shown in Figure 5 every time a processing period Δt elapses to acquire (determine) the fuel injection amount Qfin. Furthermore, the CPU executes a routine not shown to cause each of the fuel injection valves 25 to inject fuel according to the fuel injection amount Qfin.

[0074] In the processes shown in these flowcharts, the values ​​of the control state value Vc and the upper limit guard flag Xr are set and further referenced. When backlash-eliminating control is not being executed, the control state value Vc is set to "0." When any of the first limiting process, the second limiting process, the first smoothing process, and the second smoothing process is being executed, the control state value Vc is set to one of values ​​1 to 4. When the upper limit guard process is being executed, the upper limit guard flag Xr is set to "1." The control state value Vc, the upper limit guard flag Xr, and the integrated correction amount sQfb referenced in the process of FIG. 6 are each set to "0" by an initial routine (not shown) that is executed when the ECU 5 starts operating.

[0075] When the appropriate timing arrives, the CPU starts the process from step 500 in Fig. 5 and proceeds to step 505 to obtain the required injection amount Qgov. That is, the CPU obtains the required injection amount Qgov based on the required injection amount map described above. Next, the CPU proceeds to step 510 to determine whether the control state value Vc is "0".

[0076] (Case A) When backlash elimination control is not performed Assume that at present, the accelerator operation amount Accp is 0, so the vehicle 1 is in a driven state, and backlash-eliminating control is not being executed. For example, time t0 in FIG. 2 corresponds to this assumption.

[0077] In this case, since the control state value Vc is "0," the CPU determines "Yes" in step 510 and proceeds to step 515 to determine whether the conditions for starting backlash-eliminating control are met. That is, the CPU determines whether this routine is being executed for the first time after the above-mentioned conditions (a) and (b) are both met.

[0078] According to the above assumptions, condition (a) is met. On the other hand, because the accelerator operation amount Accp is "0," the required injection amount Qgov is a small value, and therefore condition (b) is not met. In other words, the conditions for starting backlash elimination control are not met. Therefore, the CPU determines "No" in step 515 and proceeds to step 530, where it sets the fuel injection amount Qfin to a value equal to the required injection amount Qgov. Next, the CPU proceeds to step 595, where it temporarily ends the processing of this routine.

[0079] (Case B) When the start condition for backlash elimination control is met It is assumed that the processing of this routine is started for the first time after the start condition of the backlash-eliminating control is satisfied. That is, it is assumed that the required injection amount Qgov was smaller than the first reference injection amount Qr1 when this routine was last executed, but that the required injection amount Qgov is now larger than the first reference injection amount Qr1. For example, time t2 in FIG. 2 corresponds to this assumption.

[0080] In this case, the CPU determines "Yes" in step 515 and proceeds to step 520, where it sets the control state value Vc to "1." Next, the CPU proceeds to step 525, where it sets the fuel injection amount Qfin to the first reference injection amount Qr1. That is, in this case, the first restriction process is executed. Then, the CPU proceeds to step 595.

[0081] Thereafter, when the processing period Δt has elapsed and the processing of this routine is executed again, the control state value Vc is different from "0," so the CPU determines "No" in step 510 and proceeds to step 535. In step 535, the CPU determines whether the control state value Vc is "1."

[0082] Because the control state value Vc is set to "1," the CPU determines "Yes" in step 535 and proceeds to step 540 to determine whether the start condition for the second restriction process described above is met. That is, the CPU determines whether this routine is being executed for the first time after the differential rotation speed dN became larger than the differential rotation speed threshold value dNth (during the execution of the first restriction process).

[0083] At this point, since no time has passed since the first restriction process was started (the processing period Δt has passed), the start condition for the second restriction process is not met. Therefore, the CPU determines "No" in step 540 and proceeds to step 525. That is, in this case, the first restriction process is executed (continued).

[0084] (Case C) When the condition for starting the second restriction process is met It is assumed that this routine is started for the first time after the start condition of the second restriction process is met. That is, it is assumed that the differential speed dN was smaller than the differential speed threshold dNth when this routine was last executed, but that the differential speed dN is now greater than the differential speed threshold dNth. For example, time t3 in FIG. 2 corresponds to this assumption.

[0085] In this case, the CPU determines "Yes" in step 540 and proceeds to step 545, where it sets the control state value Vc to "2." Next, the CPU proceeds to step 550, where it sets the fuel injection amount Qfin to the second reference injection amount Qr2. That is, in this case, the second restriction process is executed. Then, the CPU proceeds to step 595.

[0086] Thereafter, when the processing period Δt has elapsed and the processing of this routine is executed again, the control state value Vc is different from "1," so the CPU determines "No" in step 535 and proceeds to step 555. In step 555, the CPU determines whether the control state value Vc is "2."

[0087] Since the control state value Vc is set to "2," the CPU determines "Yes" in step 555 and proceeds to step 560 to determine whether the start condition for the first smoothing process described above is met. That is, the CPU determines whether the first time threshold Tth1 has elapsed after the start of the second limiting process.

[0088] At this point, since no time has passed since the second limiting process was started (the processing period Δt has passed), the start condition for the first smoothing process is not met. Therefore, the CPU determines "No" in step 560 and proceeds to step 550. That is, in this case, the second limiting process is executed (continued).

[0089] (Case D) When the condition for starting the first smoothing process is met It is assumed that this routine is started for the first time after the start condition of the first smoothing process is satisfied. That is, the first time threshold Tth1 had not elapsed since the second limiting process was started the last time this routine was executed, but it is assumed that the first time threshold Tth1 has elapsed at the present time. For example, time t4 in FIG. 2 corresponds to this assumption.

[0090] In this case, the CPU determines "Yes" in step 560 and proceeds to step 565, where it sets the control state value Vc to "3." Next, the CPU proceeds to step 570, where it executes the "first smoothing processing routine" shown in FIG. 6.

[0091] Specifically, the CPU starts the process from step 600 and proceeds to step 605, where it determines whether the upper limit guard flag Xr is "0." At this point in time, the start condition for the first smoothing process has just been established, so the upper limit guard process has not yet been executed. That is, the upper limit guard flag Xr is "0." Therefore, the CPU determines "Yes" in step 605 and proceeds to step 610, where it acquires the corrected injection amount Qfb. That is, the CPU acquires the corrected injection amount Qfb by applying the differential rotation speed dN to the above-mentioned corrected injection amount map (see FIG. 3).

[0092] Next, the CPU proceeds to step 615 and obtains the difference between the integrated upper limit amount sQmax and the integrated correction amount sQfb as the upper limit correction amount Qmxgd. At this point, the start condition for the first smoothing process has just been met, so the integrated correction amount sQfb is "0." That is, in this case, the upper limit correction amount Qmxgd is set to a value equal to the integrated upper limit amount sQmax.

[0093] Furthermore, the CPU proceeds to step 620 and determines whether the corrected injection amount Qfb is smaller than the upper limit correction amount Qmxgd. That is, the CPU determines whether the upper limit guard process should be started. At this point in time, the start condition for the first smoothing process has just been met, so the corrected injection amount Qfb is smaller than the upper limit correction amount Qmxgd (see time ta in FIG. 4).

[0094] Therefore, the CPU determines "Yes" in step 620, sequentially executes the processes of steps 625 to 635 described below, and then proceeds to step 695. That is, the CPU ends the processing of the routine in Fig. 6 and proceeds to step 595 in Fig. 5.

[0095] Step 625: The CPU acquires the sum of the previous fuel injection amount Qfinp, the first increment Qsm1, and the correction injection amount Qfb as the fuel injection amount Qfin. That is, the CPU executes a first smoothing process. Step 630: The CPU increases the value of the integrated correction amount sQfb by the correction injection amount Qfb obtained in the process of step 610. The increased added integration is referred to in the process of step 615 when the routine of FIG. 6 is executed next time.

[0096] Step 635: The CPU sets the previous fuel injection amount Qfinp to a value equal to the fuel injection amount Qfin acquired in the processing of step 625. The set previous fuel injection amount Qfinp is referenced in the processing of step 625 the next time the routine of FIG. 6 is executed. Note that when the processing of FIG. 6 is executed for the first time in conjunction with the start of the first smoothing processing, the CPU references the second reference injection amount Qr2 as the previous fuel injection amount Qfinp in the processing of step 625. That is, in the backlash-eliminating control currently being executed, the processing of step 635 has not yet been executed, and therefore the previous fuel injection amount Qfinp has not been set, so the CPU reflects the second reference injection amount Qr2 in the fuel injection amount Qfin instead of the previous fuel injection amount Qfinp.

[0097] 5 is executed again after the processing period Δt has elapsed, the control state value Vc is different from "2," so the CPU determines "No" in step 555 and proceeds to step 575. In step 575, the CPU determines whether the control state value Vc is "3."

[0098] Since the control state value Vc is set to "3," the CPU determines "Yes" in step 575 and proceeds to step 580 to determine whether the start condition for the second smoothing process described above is met. That is, the CPU determines whether the second time threshold Tth2 has elapsed after the start of the first smoothing process.

[0099] At this point in time, no time has passed since the first smoothing process was started (only the processing period Δt has passed), so the start condition for the second smoothing process is not met. Therefore, the CPU determines "No" in step 580 and proceeds to step 570. That is, the processing of the routine in FIG. 6 is executed, and therefore the first smoothing process is executed (continued).

[0100] (Case E) When upper limit guard processing is executed It is assumed that the upper limit guard process is then started. That is, it is assumed that the corrected injection amount Qfb becomes equal to or greater than the upper limit correction amount Qmxgd during the first smoothing process. For example, time t5 in FIG. 2 corresponds to this assumption.

[0101] In this case, when the processing of the routine in FIG. 6 is started after step 570 in FIG. 5, the CPU determines "No" in step 620 and proceeds to step 640. In step 640, the CPU sets the upper limit guard flag Xr to "1." Next, the CPU proceeds to step 645 and sets the corrected injection amount Qfb to "0." That is, the CPU executes upper limit guard processing. Then, the CPU proceeds to step 625.

[0102] Thereafter, when the processing period Δt has elapsed and the processing of the routine in Fig. 5 is executed again, and the processing of the routine in Fig. 6 is started via step 570, the CPU determines "No" in step 605 and proceeds to step 645. That is, since the upper limit guard flag Xr is set to "1", the upper limit guard processing is executed (continued).

[0103] (Case F) When the condition for starting the second smoothing process is met It is assumed that the condition for starting the second smoothing process is met and the routine shown in Fig. 5 is then started for the first time. That is, the second time threshold Tth2 had not yet elapsed after the first smoothing process was started the previous time the routine shown in Fig. 5 was executed, but it is assumed that the second time threshold Tth2 has now elapsed. For example, time t6 in Fig. 2 corresponds to this assumption.

[0104] In this case, the CPU determines "Yes" in step 580 and proceeds to step 585, where it sets the control state value Vc to "4." Next, the CPU proceeds to step 590, where it executes the "second smoothing processing routine" shown in FIG.

[0105] Specifically, the CPU starts the process from step 700 and proceeds to step 705, where it determines whether the sum of the previous fuel injection amount Qfinp and the second increment Qsm2 is smaller than the required injection amount Qgov. In other words, the CPU determines whether the difference between the previous fuel injection amount Qfinp and the required injection amount Qgov is larger than the second increment Qsm2. More specifically, the CPU determines whether the backlash-eliminating control should be terminated as a result of the second smoothing process being executed and the fuel injection amount Qfin increasing.

[0106] At this point in time, the start condition for the second smoothing process has just been satisfied, so the previous fuel injection amount Qfinp is smaller than the required injection amount Qgov. Therefore, the CPU determines "Yes" in step 705 and proceeds to step 710, where it obtains the sum of the previous fuel injection amount Qfinp and the second increment Qsm2 as the fuel injection amount Qfin. That is, the CPU executes the second smoothing process.

[0107] Next, the CPU proceeds to step 715, where it sets the previous fuel injection amount Qfinp to a value equal to the fuel injection amount Qfin acquired in the processing of step 710. That is, the CPU executes processing similar to that of step 635 in Fig. 6. The set previous fuel injection amount Qfinp is referred to in the processing of steps 705 and 710 when the routine in Fig. 7 is executed next time.

[0108] Furthermore, the CPU proceeds to step 795. That is, the CPU ends the processing of the routine in FIG. 7 and proceeds to step 595 in FIG.

[0109] Thereafter, when the processing period Δt has elapsed and the processing of the routine in Fig. 5 is executed again, the control state value Vc is set to "4", so the CPU determines "No" in step 575 and proceeds to step 590. That is, the processing of the routine in Fig. 7 is executed, and therefore the second smoothing processing is executed (continued).

[0110] (Case G) When ending backlash elimination control It is assumed that the fuel injection amount Qfin obtained by the second smoothing process then reaches the required injection amount Qgov. For example, time t8 in FIG. 2 corresponds to this assumption.

[0111] In this case, when the processing of the routine in Figure 7 starts after step 590 in Figure 5, the CPU determines "No" in step 705 and proceeds to step 720. In step 720, the CPU sets the fuel injection amount Qfin to a value equal to the required injection amount Qgov. That is, the CPU executes the same processing as in step 530 in Figure 5.

[0112] Next, the CPU proceeds to step 725, where it sets the control state value Vc, the upper limit guard flag Xr, and the integrated correction amount sQfb to "0." Parameters (variables) that have already been set to "0" are maintained in that state. Then, the CPU proceeds to step 795.

[0113] As described above, during execution of backlash-eliminating control (more specifically, the first smoothing process), the ECU 5 acquires the corrected injection amount Qfb based on the differential rotation speed dN and reflects the acquired corrected injection amount Qfb in the fuel injection amount Qfin. The smaller the differential rotation speed dN, the larger the corrected injection amount Qfb, and accordingly the larger the fuel injection amount Qfin. Therefore, a decrease in the engine speed NE due to an increase in the accessory load on the hydraulic pump 43 or other accessories (or other factors) is suppressed. In other words, unnecessary changes in the drive load transmitted from the internal combustion engine 21 to the torque converter 22 via the crankshaft 31 are suppressed.

[0114] As a result, there is a high possibility that the differential rotation speed dN will be maintained near the reference differential rotation speed dNrf when backlash elimination control is performed, and discontinuous changes in the acceleration As caused by backlash in the gear mechanism (see dashed line L4b in Figure 2), as well as the occurrence of abnormal noise and vibration, etc. Furthermore, by reflecting the corrected injection amount Qfb in the fuel injection amount Qfin, there is a high possibility that the differential rotation speed dN will quickly reach the vicinity of the reference differential rotation speed dNrf when backlash elimination control is performed.

[0115] Furthermore, even if the differential rotation speed dN decreases due to an increase in the turbine rotation speed NT during the execution of the first smoothing process, the corrected injection amount Qfb increases, further increasing the possibility that the differential rotation speed dN will be maintained in the vicinity of the reference differential rotation speed dNrf. An increase in the turbine rotation speed NT can occur, for example, due to a change in the gradient of the road surface on which the vehicle 1 is traveling.

[0116] In addition, after executing the first smoothing process, the ECU 5 executes the second smoothing process. In the second smoothing process, the second increment Qsm2 is larger than the first increment Qsm1, so the rate of increase of the fuel injection amount Qfin is faster than in the first smoothing process (unless the corrected injection amount Qfb is set to a large value). Therefore, after executing the first smoothing process, it is possible to quickly bring the fuel injection amount Qfin closer to the required injection amount Qgov while suppressing the occurrence of abnormal noise, vibration, and the like caused by insufficient elimination of backlash.

[0117] Furthermore, when the corrected injection amount Qfb becomes equal to or greater than the upper limit correction amount Qmxgd during execution of the first smoothing process, the ECU 5 starts the upper limit guard process. Therefore, if the engine speed NE does not increase despite the corrected injection amount Qfb (and therefore the fuel injection amount Qfin) increasing due to a decrease in the engine speed NE for some reason, the fuel injection amount Qfin is prevented from becoming larger than necessary. If the fuel injection amount Qfin becomes larger than necessary, when the cause that prevented the engine speed NE from increasing is resolved, the engine speed NE may suddenly increase, causing discomfort to the occupants of the vehicle 1.

[0118] Although the embodiments of the present invention have been described above with reference to the above structures, many alternatives, improvements, and modifications are possible without departing from the scope of the present invention. Therefore, the present invention includes all alternatives, improvements, and modifications that do not depart from the spirit and scope of the appended claims. The present invention is not limited to the specific structures described above, and modifications (i.e., variations of the embodiments) such as those described below are possible.

[0119] The ECU 5 previously acquired the corrected injection amount Qfb in the range from "0" to the injection amount Qfbmx (see FIG. 3). Alternatively, the ECU 5 may set the corrected injection amount Qfb to a negative value when the differential rotation dN increases. In this case, even if the auxiliary load decreases during execution of the first smoothing process, the increase in the engine speed NE is suppressed.

[0120] Furthermore, in this case, the ECU 5 may execute a "lower limit guard process" in addition to or instead of the upper limit guard process. That is, the ECU 5 may acquire the corrected injection amount Qfb so that the integrated correction amount sQfb does not exceed a predetermined integrated lower limit amount sQmin. For example, the ECU 5 may refer to the integrated lower limit amount sQmin, which is a negative value, and set the corrected injection amount Qfb to "0" if the integrated correction amount sQfb becomes smaller than the integrated lower limit amount sQmin as a result of consecutively setting the integrated correction amount Qfb to negative values. Alternatively, the ECU 5 may refer to the integrated lower limit amount sQmin, which is a positive value, and acquire the corrected injection amount Qfb so that the integrated correction amount sQfb does not become smaller than the integrated lower limit amount sQmin during a period after the integrated correction amount sQfb becomes larger than the integrated lower limit amount sQmin.

[0121] The first increment Qsm1 and the second increment Qsm2 in the first and second smoothing processes are fixed values. Alternatively, one or both of the first increment Qsm1 and the second increment Qsm2 may be variable. For example, the first increment Qsm1 or the second increment Qsm2 may increase over time. Alternatively, the first increment Qsm1 or the second increment Qsm2 may decrease over time.

[0122] Additionally, even during the second smoothing process, the ECU 5 may obtain the fuel injection amount Qfin based on the corrected injection amount Qfb, which increases as the differential rotation speed dN decreases. That is, the ECU 5 may obtain the fuel injection amount Qfin as the sum of the previous fuel injection amount Qfinp, the corrected injection amount Qfb, and the second increase amount Qsm2. In this case, the ECU 5 may obtain the corrected injection amount Qfb by applying the differential rotation speed dN to a map (i.e., the relationship between the differential rotation speed dN and the corrected injection amount Qfb) different from the corrected injection amount map (see FIG. 3) referred to during the first smoothing process.

[0123] Furthermore, the first increment Qsm1 in the first smoothing process may be "0." More specifically, the fuel injection amount Qfin during the execution of the above-described first smoothing process is the sum of the first increment Qsm1, which is a feedforward value, and the corrected injection amount Qfb, which is a feedback value. Alternatively, the fuel injection amount Qfin during the execution of the first smoothing process may be acquired based only on the feedback value. In this case, when the integrated value of the fuel injection amount Qfin acquired during the execution of the first smoothing process exceeds a predetermined value, the ECU 5 may execute, as an upper limit guard process, a process of increasing the fuel injection amount Qfin by "a value acquired independently of the differential rotation speed dN" every time a processing period Δt elapses.

[0124] Furthermore, the ECU 5 may acquire the corrected injection amount Qfb so that it increases with the passage of time after the start of the first smoothing process (as shown in FIG. 3, the smaller the differential rotation speed dN is, and the larger the corrected injection amount Qfb is). In this case, even if the first increment Qsm1 is set to "0", it is possible to gradually increase the fuel injection amount Qfin when the first smoothing process is executed.

[0125] The ECU 5 determines whether or not to terminate the backlash-reducing control (control termination determination) by processing step 705 in Fig. 7. Instead of this, or in addition to this, the ECU 5 may perform the control termination determination in the routines shown in Figs. 5 and 6. For example, the ECU 5 may terminate the backlash-reducing control when the accelerator operation amount Accp decreases while the backlash-reducing control is being executed, resulting in a decrease in the required injection amount Qgov.

[0126] The ECU 5 may predict changes in the auxiliary load of the hydraulic pump 43 and other auxiliary devices (for example, the alternator and air conditioner compressor described above) in advance and obtain (determine) the fuel injection amount Qfin in accordance with the predicted auxiliary load. More specifically, the ECU 5 may obtain the auxiliary injection amount Qpr based on the predicted auxiliary load and increase the fuel injection amount Qfin in accordance with the auxiliary injection amount Qpr. Even in this case, if the engine speed NE decreases during execution of the first smoothing process due to an unexpected change in the auxiliary load, a decrease in the prediction accuracy of the auxiliary load, or the like, the corrected injection amount Qfb is increased, thereby suppressing a decrease in the engine speed NE.

[0127] The start condition for the first smoothing process was met when a first time threshold Tth1 had elapsed after the start of the second limiting process. The start condition for the second smoothing process was met when a second time threshold Tth2 had elapsed after the start of the first smoothing process. One or both of the start conditions for the first smoothing process and the second smoothing process may be different conditions. For example, the start condition for the first smoothing process may be a condition that is met depending on the magnitude relationship between the differential rotation dN after the start of the second limiting process and a predetermined value. Alternatively, the start condition for the second smoothing process may be a condition that is met when the magnitude of the difference between the differential rotation dN and the reference differential rotation dNrf after the start of the first smoothing process continues to be smaller than a predetermined value for a predetermined period of time.

[0128] One of the first limiting process and the second limiting process may be omitted. Furthermore, the second smoothing process may be omitted. That is, from the start of the first smoothing process to the end of the backlash-eliminating control, the fuel injection amount Qfin may be acquired based on the first increment Qsm1 and the corrected injection amount Qfb, without depending on the second increment Qsm2.

[0129] The ECU 5 acquires the required injection amount Qgov based on the accelerator operation amount Accp. However, there may be cases where the ECU 5 does not take the accelerator operation amount Accp into consideration when acquiring the required injection amount Qgov. For example, when adaptive cruise control (ACC) control is being executed, which determines the traveling speed based on a target inter-vehicle distance from a vehicle traveling ahead of the vehicle 1 or a target speed set by the driver, the ECU 5 may acquire the required injection amount Qgov based on the target inter-vehicle distance or the target speed. Even in this case, it can be said that the required injection amount Qgov is acquired based on the acceleration As (indirectly) requested by the occupant of the vehicle 1.

[0130] The torque converter 22, which is one type of fluid transmission device, is disposed in the torque transmission path of the vehicle 1. Instead of this, a well-known fluid coupling, which is another type of fluid transmission device, may be disposed in the torque transmission path.

[0131] The driving wheels 12a-12b are the rear wheels of the vehicle 1. Alternatively, the steerable wheels 11a-11b may also serve as the driving wheels. In other words, the vehicle 1 may be a front-wheel drive vehicle.

[0132] The vehicle 1 has an internal combustion engine 21 as a driving force source. In addition, the vehicle 1 may have an electric motor as a driving force source. That is, the vehicle 1 may be a hybrid vehicle. In this case, the torque generated by the electric motor is transmitted to, for example, a crankshaft 31 or a turbine shaft 32.

[0133] The internal combustion engine 21 was a diesel engine having a fuel injection valve 25 that injects fuel into the combustion chamber. Alternatively, the internal combustion engine 21 may be a gasoline engine having a fuel injection valve that injects fuel into an intake port that introduces intake air into the combustion chamber. [Explanation of symbols]

[0134] 1... vehicle, 11a-11b... steering wheels, 12a-12b... driving wheels 2...Powertrain system, 21...Internal combustion engine, 22...torque converter, 22a...pump impeller, 22b...turbine runner 23...Transmission, 24...Differential gear, 25...Fuel injection valve 31... crankshaft, 32... turbine shaft, 33... propeller shaft 34a~34b...Drive shaft 4...Steering system, 41...Steering handle, 42...Steering gearbox 43...hydraulic pump, 44...reservoir tank, 45...control valve 46...steering shaft, 47a to 47b...tie rods, 48...drive belt 5...ECU 61... crank angle sensor, 62... cam position sensor, 63... Turbine rotation speed sensor, 64... Accelerator operation amount sensor, 65... Accelerator pedal

Claims

1. an internal combustion engine including a fuel injector; a fluid transmission device disposed in a torque transmission path between the internal combustion engine and drive wheels; A vehicle control device applied to a vehicle having a control unit that executes backlash-eliminating control to temporarily reduce the fuel injection amount of the fuel injection valve to a value less than the required injection amount according to the acceleration required by an occupant of the vehicle when the vehicle is switched from a driven state to a driving state; The control unit A vehicle control device that, while the backlash-eliminating control is being executed, executes an injection amount correction process that acquires the fuel injection amount based on a correction injection amount that increases as the differential rotation between the rotation speed of the internal combustion engine side and the rotation speed of the drive wheel side in the fluid transmission device decreases.

2. 2. The vehicle control device according to claim 1, The control unit The vehicle control device increases the fuel injection amount by a sum of a first increment and the corrected injection amount every time a predetermined time elapses during execution of the injection amount correction process.

3. 2. The vehicle control device according to claim 1, The control unit A vehicle control device that executes at least one of a process of acquiring the corrected injection amount so that an integrated value of the corrected injection amount does not exceed an integrated upper limit amount, and a process of acquiring the corrected injection amount so that the integrated value does not exceed an integrated lower limit amount.

4. 3. The vehicle control device according to claim 2, The control unit a vehicle control device that increases the fuel injection amount by a second increase amount greater than the first increase amount every time the predetermined time elapses while the backlash-eliminating control is being executed and after the injection amount correction process is executed;

5. 2. The vehicle control device according to claim 1, The vehicle control device includes an auxiliary device that is operated by the output of the internal combustion engine.

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