Vehicle control devices

Abstract

The present invention provides a vehicle control device that can appropriately control the responsiveness of switching to all-wheel drive mode according to the vehicle's driving conditions. [Solution] The electronic control unit 80 sets the allowable value Nlmt to be larger as the road surface unevenness value RE during driving and the accelerator operation amount Δθacc during a predetermined period ΔT increase. As a result, the responsiveness of the engagement of the dog clutch 60, i.e., the responsiveness of switching to the all-wheel drive state, becomes faster as the road surface unevenness value RE during driving and the accelerator operation amount Δθacc during a predetermined period ΔT increase. Therefore, in situations where the occurrence of noise and shock when the dog clutch 60 engages is acceptable, the responsiveness of switching to the 4WD state is appropriately controlled according to the driving state of the vehicle 10.

Description

Technical Field

[0001] The present invention relates to a vehicle control device in which a meshing clutch provided in a power transmission path between one of the front and rear wheels and an electric motor is disengaged when only one of the front and rear wheels is in a driving state.

Background Art

[0002] A control device for a vehicle including a power source that drives only one of the front and rear wheels, an electric motor that drives only the other of the front and rear wheels, and a meshing clutch provided in a power transmission path between the other wheel and the electric motor is well known. For example, the drive vehicle for a vehicle described in Patent Document 1 is such a vehicle. Patent Document 1 discloses that after controlling the electric motor so that the rotational speed of the electric motor estimated from the current and duty value of the electric motor matches the rotational speed corresponding to the rotational speed of the other wheel detected by the sensor, the meshing clutch is engaged.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the aforementioned vehicle, when switching from a drive state where only one wheel is driven to an all-wheel drive state as acceleration and deceleration increase, the clutch engages only after the rotational speeds of the opposing meshing teeth of the clutch have become sufficiently close, that is, when the difference in rotational speed is below an acceptable value. This is to suppress noise and shock, which would occur if the clutch were engaged when the difference in rotational speed is large. For this reason, clutch engagement required a reasonable response time until the difference in rotational speed was below an acceptable value. On the other hand, when the road surface was very uneven during driving, or when the driver requested sudden acceleration (or sudden deceleration), that is, when the amount of accelerator operation within a given period was large, it was required to engage the clutch earlier, tolerating a reasonable amount of noise and shock, and to quickly switch to the all-wheel drive state. This is because if the responsiveness of switching to the all-wheel drive state is poor in driving conditions with uneven road surfaces or large acceleration and deceleration, drivability will be impaired.

[0005] The present invention was made against the above circumstances, and its objective is to provide a vehicle control device that can appropriately control the responsiveness of switching to an all-wheel drive state according to the vehicle's driving conditions. [Means for solving the problem]

[0006] The gist of the present invention is a vehicle control device that, in a vehicle comprising (a) a power source that drives only one of the front wheels and rear wheels, an electric motor that drives only the other of the front wheels and rear wheels, and a meshing clutch provided in the power transmission path between the other wheel and the electric motor, switches from a drive state in which the clutch is disengaged and only one wheel is driven to a full-wheel drive state in which the clutch is engaged and both the front and rear wheels are driven, by controlling the clutch to engage when the difference in rotational speed of the opposing meshing teeth of the clutch falls below an allowable value, and (b) sets the allowable value to be larger as the road surface irregularities during driving and the amount of accelerator operation by the driver over a predetermined period of time increase. [Effects of the Invention]

[0007] According to the present invention, the larger the road surface irregularities during driving and the amount of accelerator operation by the driver over a predetermined period, the larger the allowable value is set. As a result, the larger the road surface irregularities during driving and the amount of accelerator operation by the driver over a predetermined period, the faster the responsiveness of the clutch engagement, i.e., the responsiveness of switching to the all-wheel drive state. Therefore, in situations where the occurrence of noise and shock during clutch engagement is acceptable, the responsiveness of switching to the all-wheel drive state is appropriately controlled according to the driving conditions of the vehicle. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram illustrates the schematic configuration of a vehicle to which the present invention is applied, as well as the control functions and key components of the control system for various control functions in the vehicle. [Figure 2] This is a time chart illustrating an example of control operation when the dog clutch is engaged. [Figure 3] This is a flowchart illustrating the key aspects of the control operation of an electronic control unit. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Examples]

[0010] Figure 1 is a diagram illustrating the schematic configuration of a vehicle 10 to which the present invention is applied. In Figure 1, the vehicle 10 is equipped with left and right front wheels 12, a front-wheel drive unit 20 that drives the front wheels 12, left and right rear wheels 14, and a rear-wheel drive unit 30 that drives the rear wheels 14, all spaced apart from each other. The vehicle 10 is also equipped with a battery 40, which is a rechargeable DC power source. Note that "left and right" above refers to left and right with respect to the forward direction of the vehicle 10.

[0011] Vehicle 10 is an all-wheel drive vehicle in which the drive torque distribution between the front wheels 12 and the rear wheels 14 can be adjusted. All-wheel drive (AWD) and four-wheel drive (4WD) are synonymous. In addition to driving in 4WD control (4WD state is also synonymous), vehicle 10 can also drive in two-wheel drive (2WD) control (2WD state is also synonymous) in which the drive torque is distributed to only one of the front wheels 12 or the rear wheels 14.

[0012] The front-wheel drive system 20 includes an MGF 22, a front-wheel power transmission system 24, and an inverter 26.

[0013] MGF22 is a known rotating electric machine, a so-called motor generator, and is connected to the battery 40 via an inverter 26. MGF22 is an electric motor that drives only the front wheel 12, which is the other wheel of the rear wheels 14.

[0014] The inverter 26 is a power control device that controls the power exchanged between the battery 40 and the MGF22. The inverter 26 controls the power of the MGF22 by being controlled by the electronic control device 80, which will be described later.

[0015] The front wheel power transmission system 24 includes a counter gear mechanism 50, a counter shaft 52, a final gear 54, a front wheel differential gear (hereinafter referred to as the front wheel differential) 56, etc. The front wheel power transmission system 24 also includes left and right front wheel drive shafts 58 connected to the front wheel differential 56, etc. The counter gear mechanism 50 is a gear pair having a drive gear 50a and a driven gear 50b that meshes with the drive gear 50a. The drive gear 50a is connected to the MGF 22, and the driven gear 50b is connected to the final gear 54 via the counter shaft 52. The final gear 54 meshes with the differential ring gear 56r of the front wheel differential 56. The front wheel drive shafts 58 connect the front wheel differential 56 and the front wheels 12. The front wheel power transmission system 24 transmits power from the MGF 22 to the front wheels 12.

[0016] The front-wheel power transmission device 24 includes a dog clutch 60 and an actuator 62. The dog clutch 60 is a known meshing clutch provided in the power transmission path between the front wheels 12 and the MGF 22. The actuator 62 is controlled by an electronic control device 80 described later to control the switching between the engaged state and the disengaged state of the dog clutch 60.

[0017] The dog clutch 60 is provided, for example, in the power transmission path between the front-wheel differential 56 and the left front wheel 12. The dog clutch 60 has first dog teeth 60a and second dog teeth 60b as opposing meshing teeth. The first dog teeth 60a are connected to the front-wheel differential 56 and are the meshing teeth on the MGF 22 side among the opposing meshing teeth. The second dog teeth 60b are connected to the left front-wheel drive shaft 58 and are the meshing teeth on the front-wheel 12 side among the opposing meshing teeth. The dog clutch 60 is brought into an engaged state when the first dog teeth 60a and the second dog teeth 60b are meshed, and is brought into a disengaged state when their meshing is released.

[0018] The rear-wheel drive device 30 includes an MGR 32, a rear-wheel power transmission device 34, and an inverter 36.

[0019] The MGR 32 is a known rotary electric machine, a so-called motor generator, and is connected to the battery 40 via the inverter 36. The MGR 32 is a power source that drives only the rear wheels 14, which are one of the front wheels 12 and the rear wheels 14.

[0020] The inverter 36 has the same function as the inverter 26 and controls the power of the MGR 32 by being controlled by an electronic control device 80 described later.

[0021] The rear-wheel power transmission device 34 includes a counter gear mechanism 70, a counter shaft 72, a final gear 74, a rear-wheel differential gear 76, left and right rear-wheel drive shafts 78, etc. The rear-wheel power transmission device 34 has the same function as the front-wheel power transmission device 24 and transmits the power from the MGR 32 to the rear wheels 14.

[0022] In the vehicle 10, the rear wheels 14 are driven when in the 2WD state and the 4WD state, and the front wheels 12 are driven only when in the 4WD state. The 4WD state is a driving state in which the front wheels 12 and the rear wheels 14 are driven in the engaged state of the dog clutch 60, and the power transmission path between the front wheels 12 and the MGF22 is in a connected state, that is, a connected state. The 2WD state is a driving state in which only the rear wheels 14 are driven in the released state of the dog clutch 60, and the power transmission path between the front wheels 12 and the MGF22 is in a disconnected state, that is, a disconnected state. By being in the disconnected state during 2WD control, the rotation members of the front wheel power transmission device 24 on the MGF22 side and the rotation of the MGF22 are stopped from the dog clutch 60. Thereby, the occurrence of power loss due to the rotation of the counter gear mechanism 50, the final gear 54, the front wheel differential 56, etc. is prevented or suppressed. The dog clutch 60 is a disconnect mechanism capable of disconnecting the power transmission path between the front wheels 12 and the MGF22.

[0023] The vehicle 10 further includes, as a vehicle control device, an electronic control device 80 configured to include a so-called microcomputer.

[0024] Various signals based on the detection values of various sensors provided in the vehicle 10 are respectively supplied to the electronic control device 80. The various sensors are, for example, the MGF rotation sensor 90, the wheel speed sensor 92, the accelerator opening sensor 94, the brake sensor 96, the in-vehicle camera 98, etc. The various signals are, for example, the MGF rotation speed Nmgf which is the rotation speed of the MGF22, the left front wheel rotation speed Nwfl, the right front wheel rotation speed Nwfr, the left rear wheel rotation speed Nwrl, the right rear wheel rotation speed Nwrr, the accelerator opening θacc, the brake operation amount Bra, the in-vehicle camera imaging information Iard, etc. The MGF rotation speed Nmgf corresponds to the first rotation speed Ndg1 which is the rotation speed of the first dog tooth 60a.

[0025] From the electronic control unit 80, various command signals are output to each device provided in the vehicle 10. Each device is, for example, the inverter 26, the inverter 36, the actuator 62, etc. The various command signals are, for example, the MGF control signal Smgf for controlling the MGF 22, the MGR control signal Smgr for controlling the MGR 32, and the actuator control signal Sc for controlling the switching between the engaged state and the released state of the dog clutch 60.

[0026] The electronic control unit 80 functionally includes a drive control unit 82, a dog control unit 84, a tolerance value setting unit 86, etc.

[0027] The drive control unit 82 calculates a required acceleration or a required deceleration for the vehicle 10 based on the accelerator opening θacc and / or the brake operation amount Bra, etc., and determines the switching of the drive state based on the required acceleration or the required deceleration, the wheel slip, the driving mode selection by the driver, etc. For example, during 2WD control, when the required acceleration or the required deceleration is increased, the drive control unit 82 determines the switching to the 4WD state and outputs a command to switch the dog clutch 60 to the engaged state to the dog control unit 84.

[0028] The dog control unit 84 increases the MGF rotational speed Nmgf so that the first rotational speed Ndg1 of the first dog tooth 60a becomes the left front wheel rotational speed Nwfl corresponding to the rotational speed of the second dog tooth 60b in accordance with the command to switch the dog clutch 60 to the engaged state. Then, when the dog rotational speed difference ΔNdg, which is the absolute value of the difference between the left front wheel rotational speed Nwfl and the first rotational speed Ndg1, is less than the tolerance value Nlmt (ΔNdg = |Nwfl - Ndg1| < Nlmt), the dog control unit 84 operates the actuator 72 so that the dog clutch 60 is in the engaged state. The dog rotational speed difference ΔNdg corresponds to the "rotational speed difference between the opposing meshing teeth" of the present invention. The tolerance value Nlmt is a threshold value for determining the start of engagement of the dog clutch 60 and is preset by the tolerance value setting unit 86.

[0029] FIG. 2 is a time chart for explaining an example of control operation during engagement of the dog clutch 60 performed by the dog control unit 84. The upper part shows an example where a predetermined value N1 is set in advance so that the generation of noise and shock due to clutch engagement is suppressed to the allowable value Nlmt (when the allowable value Nlmt = N1), and the lower part shows an example where a predetermined value N2 greater than the predetermined value N1 is set for the allowable value Nlmt (when the allowable value Nlmt = N2). In each example, the horizontal axis represents time, and the vertical axis represents the dog rotation speed difference ΔNdg, the state of the dog clutch 60, and the total driving torque by which the front wheels 12 and the rear wheels 14 drive the vehicle 10.

[0030] In the upper part of FIG. 2 (when the allowable value Nlmt = N1), the rotation of the MGF 22 starts at time t1, and accordingly, the dog rotation speed difference ΔNdg decreases. Then, at time t4 when the dog rotation speed difference ΔNdg becomes less than the allowable value Nlmt, that is, less than the predetermined value N1 (△Ndg < Nlmt = N1), the actuator 72 is operated so that the dog clutch 60 is in an engaged state, and at time t5, the total driving torque increases to the required driving torque (see the one-dot chain line in the figure), and the switching to the 4WD state is completed. On the other hand, in the lower part of FIG. 2 (when the allowable value Nlmt = N2), the allowable value Nlmt is a predetermined value N2 greater than the predetermined value N1, and the engagement of the dog clutch 60 starts at time t2, which is earlier than the aforementioned time t4 when the dog rotation speed difference ΔNdg becomes less than the allowable value Nlmt (△Ndg < Nlmt = N2). Since the dog rotation speed difference ΔNdg is greater than the predetermined value N1, noise and shock occur during engagement, but the total driving torque increases to the required driving torque at time t3, which is earlier than the aforementioned time t5, and the switching to the 4WD state is completed. Thus, as the allowable value Nlmt increases, the noise and shock during the engagement of the dog clutch 60 increase, but the responsiveness of the engagement, that is, the responsiveness of the switching to the 4WD state, is increased.

[0031] Incidentally, when the road surface is uneven during driving, or when the driver requests sudden acceleration (or sudden deceleration), that is, when the accelerator is operated significantly within a predetermined period, it was required that the dog clutch 60 be engaged quickly, even if it meant tolerating a certain amount of noise and shock, and that the vehicle would quickly switch to 4WD mode. In other words, the operation shown in the lower part of Figure 2 was required. This is because if the response to switching to 4WD mode is poor in driving conditions with uneven road surfaces or significant acceleration and deceleration, drivability will be impaired.

[0032] Therefore, the electronic control unit 80 controls the responsiveness of switching to the 4WD state according to the vehicle's driving state, using the control operation described in the flowchart of Figure 3. Figure 3 is a flowchart illustrating the main part of the control operation of the electronic control unit 80, and is a flowchart illustrating the operation of setting the allowable value Nlmt by the allowable value setting unit 86, which is executed repeatedly, for example.

[0033] First, in step S10 (the step will be omitted hereafter), it is determined whether or not the road surface irregularities during driving are large. This determination is made, for example, by calculating a road surface irregularity value RE, which indicates the magnitude of the road surface irregularities, according to a predetermined calculation method, based on the fluctuation trends of the rotational speeds (Nwfl, Nwfr, Nwrl, Nwrr) of the front wheels 12 and rear wheels 14 respectively from the wheel speed sensor 92, and information from the road surface image acquired from the onboard camera imaging information Iard from the onboard camera 98. The determination is then made as to whether or not the road surface irregularity value RE is greater than a predetermined value Rn. The predetermined value Rn is a set value that has been determined in advance, either through design or experiment, in order to determine the magnitude of the road surface irregularities.

[0034] If the judgment in S10 is denied, in S20, it is determined whether the driver's accelerator operation amount Δθacc is large or not, i.e., whether the accelerator operation amount Δθacc is greater than a predetermined value Ae. The accelerator operation amount Δθacc is the amount of change in the accelerator opening θacc over a predetermined period ΔT, i.e., the rate of change. The predetermined value Ae and predetermined period ΔT are set values ​​that have been determined in advance through design or experimentation to determine the driver's accelerator operation amount Δθacc.

[0035] When the determination in S20 is negative, in S40, a small predetermined value Nmin is set to the allowable value Nlmt (Nlmt = Nmin). When the determination in S20 is affirmative or the determination in S30 is negative, in S50, a medium predetermined value Nmid is set to the allowable value Nlmt (Nlmt = Nmid). When the determination in S30 is affirmative, in S60, a large predetermined value Nmax is set to the allowable value Nlmt (Nlmt = Nmax). Then, after the processes of S40, S50, and S60, this routine is terminated. The small predetermined value Nmin, the medium predetermined value Nmid, and the large predetermined value Nmax satisfy Nmin < Nmid < Nmax, and are set values obtained in advance by design or experiment so that the responsiveness of the switching to the 4WD state is appropriate while tolerating the generation of sound and shock due to the engagement of the dog clutch 60 according to the driving state determined in S10 to S30.

[0036] The flowchart of FIG. 3 is an example of setting the allowable value Nlmt in three levels of a small predetermined value Nmin, a medium predetermined value Nmid, and a large predetermined value Nmax according to the magnitudes of the road surface unevenness value RE and the accelerator operation amount Δθacc. However, for example, by applying it to a setting map or the like that increases the allowable value Nlmt as the road surface unevenness value RE and the accelerator operation amount Δθacc each increase, the allowable value Nlmt may be preferably set in more levels than three levels.

[0037] As described above, according to this embodiment, as the road surface unevenness value RE during traveling and the accelerator operation amount Δθacc in the predetermined period ΔT each increase, the allowable value Nlmt is set larger. Thereby, as the road surface unevenness value RE during traveling and the accelerator operation amount Δθacc in the predetermined period ΔT each increase, the responsiveness of the engagement of the dog clutch 60, that is, the responsiveness of the switching to the all-wheel drive state is accelerated. Therefore, in a scene where the generation of sound and shock at the time of engagement of the dog clutch 60 can be tolerated, the responsiveness of the switching to the 4WD state is appropriately controlled according to the driving state of the vehicle 10.

[0038] As described above, the embodiments of the present invention have been described in detail based on the drawings, but the present invention is also applicable in other aspects.

[0039] For example, in the above embodiment, the power source for the rear-wheel drive system 30 may be an engine in addition to, for example, the MGR 32. Alternatively, one of the front wheels 12 and the other rear wheel 14 may be the front wheel 12 and the other wheel may be the rear wheel 14. In this case, the system is equipped with a power source that drives only the front wheel 12, an electric motor that drives only the rear wheel 14, and a meshing clutch provided in the power transmission path between the rear wheel 14 and the electric motor.

[0040] It should be noted that the above-described embodiment is merely one example, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of Symbols]

[0041] 10: Vehicle 12: Front wheel (the other wheel) 14: Rear wheel (one wheel) 22: MGF (motor) 32: MGR (power source) 60: Dog clutch (meshing clutch) 80: Electronic control unit (vehicle control unit) Nlmt: Tolerance RE: Road surface irregularity value (road surface irregularity) ΔNdg: Dog rotation speed difference (difference in rotation speed of opposing meshing teeth) ΔT: Predetermined period Δθacc: Accelerator operation amount

Claims

[Claim 1] In a vehicle comprising a power source that drives only one of the front and rear wheels, an electric motor that drives only the other of the front and rear wheels, and a meshing clutch provided in the power transmission path between the other wheel and the electric motor, the vehicle control device controls the switching from a drive state in which the clutch is disengaged and only one wheel is driven to a full-wheel drive state in which the clutch is engaged and both the front and rear wheels are driven, by switching the clutch to the engaged state when the difference in rotational speed of the opposing meshing teeth of the clutch falls below an allowable value, The greater the road surface irregularities during driving and the amount of accelerator operation by the driver over a predetermined period, the larger the allowable value will be set. A vehicle control device characterized by the following features.

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