Vehicle control system

Abstract

The present invention provides a vehicle control device that can suppress the generation of noise and shock when engaging a mesh-type clutch. [Solution] When a switch is determined from a drive state where only one wheel is driven to a full-wheel drive state, the rotational speed of the electric motor is increased so that the rotational speeds of the opposing meshing teeth of the clutch are synchronized. When it is determined that the rotational speeds of the opposing meshing teeth are synchronized, the switch to the clutch engagement state is initiated. In addition, the rotational speed of the meshing teeth on the other wheel side after a predetermined time from the synchronization determination point to the start of meshing is calculated based on the acceleration / deceleration request. Furthermore, the rotational speed of the electric motor is changed so that the rotational speed of the meshing teeth on the electric motor side becomes the rotational speed of the meshing teeth on the wheel side after a predetermined time. As a result, the rotational speed of the electric motor is corrected so that the opposing meshing teeth engage in a state where the rotational speeds are synchronized during the transient period from the synchronization determination point to the start of meshing.

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 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 are well-known in a control device of a vehicle. For example, a front and rear wheel drive vehicle described in Patent Document 1 is such a vehicle. In this Patent Document 1, 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, it discloses engaging a meshing clutch.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, a considerable amount of time is required from the moment the system determines that the rotational speeds of the opposing meshing teeth of the clutch are synchronized until the system starts switching to the engaged state and the opposing meshing teeth actually begin to engage. Therefore, as acceleration and deceleration increase, when switching from a drive state where only one wheel is driven to an all-wheel drive state where the clutch is engaged, the rotational speed of the meshing teeth on the other wheel side of the opposing meshing teeth of the clutch is changed by the acceleration and deceleration during the transition. As a result, the difference in rotational speed at the start of the meshing of the opposing meshing teeth of the clutch may not match the synchronization determination point, and the opposing meshing teeth may engage without the rotational speeds being synchronized, potentially increasing noise and shock.

[0005] The present invention was made against the above circumstances, and its objective is to provide a vehicle control device that can suppress the generation of noise and shock when engaging a mesh-type clutch. [Means for solving the problem]

[0006] The gist of the first invention is a control device for 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, wherein (b) when it is determined to switch from a drive state in which only one wheel is driven with the clutch disengaged to an all-wheel drive state in which both the front and rear wheels are driven with the clutch engaged, the rotation of the electric motor is adjusted so that the rotational speeds of the opposing meshing teeth of the clutch are synchronized. (c) When it is determined that the rotational speed of the opposing meshing teeth has synchronized, the clutch is switched to the engaged state, and the rotational speed of the other wheel-side meshing tooth of the opposing meshing teeth is calculated based on the acceleration / deceleration request to the vehicle after a predetermined time has elapsed from the time it is determined that the teeth have synchronized until the time the opposing meshing teeth begin to mesh, and the rotational speed of the motor is changed so that the rotational speed of the motor-side meshing tooth of the opposing meshing teeth becomes the rotational speed of the wheel-side meshing tooth after the predetermined time. [Effects of the Invention]

[0007] According to the first invention, when a switch is determined to change from a drive state in which only one wheel is driven to a full-wheel drive state, the rotational speed of the electric motor is increased so that the rotational speeds of the opposing meshing teeth of the clutch become synchronized. When it is determined that the rotational speeds of the opposing meshing teeth are synchronized, the switch to the clutch engagement state is initiated. In addition, the rotational speed of the meshing teeth on the other wheel side after a predetermined time from the synchronization determination point to the start of meshing is calculated based on the acceleration / deceleration requirement. Furthermore, the rotational speed of the electric motor is changed so that the rotational speed of the meshing teeth on the electric motor side becomes the rotational speed of the meshing teeth on the wheel side after a predetermined time. As a result, the rotational speed of the electric motor is corrected so that the opposing meshing teeth mesh in a synchronized state during the transient period from the synchronization determination point to the start of meshing of the opposing meshing teeth. Therefore, it is possible to suppress the generation of noise and shock when engaging a meshing type clutch. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram illustrates the schematic configuration of a vehicle to which the present invention is applied. [Figure 2] This diagram illustrates the control functions and key components of the control system in a vehicle. [Figure 3] This flowchart explains the key aspects of the control operation of an electronic control unit, specifically the control operation to suppress noise and shock when engaging the dog clutch. [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 drive unit 20 that drives the front wheels 12, left and right rear wheels 14, and a rear 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 drive unit 20 comprises an MGF 22, a front power transmission unit 24, a front PCU (Power Control Unit) 26, and a front case 28. The front case 28 is a case that is mounted on the vehicle body.

[0013] The MGF22 is housed within the front case 28. The MGF22 is a known rotating electric machine, a so-called motor generator, and is connected to the battery 40 via the front PCU 26. The MGF22 is a front motor that serves as a power source to drive only the front wheel 12, which is one of the two wheels (front wheel 12 and rear wheel 14).

[0014] The front PCU26 is a power control device that includes, for example, an inverter, and controls the power exchanged between the battery 40 and the MGF22. The front PCU26 is controlled by the electronic control device 80, which will be described later, to control the MGF torque Tmgf, which is the torque of the MGF22.

[0015] The front power transmission system 24 includes a counter gear mechanism 50, a counter shaft 52, a final gear 54, a front differential gear 56, etc., within the front case 28. The front power transmission system 24 also includes left and right front drive shafts 58 connected to the front differential gear 56. 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 differential gear 56. The front drive shafts 58 connect the front differential gear 56 to the front wheels 12. The front power transmission system 24 transmits power from the MGF 22 to the front wheels 12.

[0016] The rear drive unit 30 comprises an MGR 32, a rear power transmission unit 34, a rear PCU 36, and a rear case 38. The rear case 38 is a case that is mounted on the vehicle body.

[0017] The MGR32 is provided inside the rear case 38. The MGR32 is a known rotary electric machine, a so-called motor generator, and is connected to the battery 40 via the rear PCU 36. The MGR32 is a rear motor as an electric motor that drives only the rear wheel 14, which is the other wheel of the front wheel 12 and the rear wheel 14.

[0018] The rear PCU 36 has the same function as the front PCU 26, and controls the MGR torque Tmgr, which is the torque of the MGR32, by being controlled by an electronic control unit 80 described later.

[0019] The rear power transmission device 34 includes a counter gear mechanism 60, a counter shaft 62, a final gear 64, a rear differential gear 66, left and right rear drive shafts 68, etc. The rear power transmission device 34 has the same function as the front power transmission device 24, and transmits the power from the MGR32 to the rear wheel 14.

[0020] The rear power transmission device 34 includes a dog clutch 70 and an actuator 72. The dog clutch 70 is a known meshing clutch provided in the power transmission path between the rear wheel 14 and the MGR32. The actuator 72 controls the switching between the engaged state and the released state of the dog clutch 70 by being controlled by an electronic control unit 80 described later.

[0021] The dog clutch 70 is provided, for example, in the power transmission path between the rear differential gear 66 and the left rear wheel 14. The dog clutch 70 has a first dog tooth 70a and a second dog tooth 70b as opposing meshing teeth. The first dog tooth 70a is connected to the rear differential gear 66 and is the meshing tooth on the MGR32 side of the opposing meshing teeth. The second dog tooth 70b is connected to the left rear drive shaft 68 and is the meshing tooth on the rear wheel 14 side of the opposing meshing teeth. The dog clutch 70 is brought into the engaged state when the first dog tooth 70a and the second dog tooth 70b are meshed, and is brought into the released state when their meshing is released.

[0022] In the vehicle 10, the front wheels 12 are driven when in the 2WD state and the 4WD state, and the rear wheels 14 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 70, and the power transmission path between the rear wheels 14 and the MGR 32 is in the connected state, that is, the connect state. The 2WD state is a driving state in which only the front wheels 12 are driven in the released state of the dog clutch 70, and the power transmission path between the rear wheels 14 and the MGR 32 is in the disconnected state, that is, the disconnect state. By being in the disconnected state during 2WD control, the rotation of the rotating members of the rear power transmission device 34 on the MGR 32 side and the rotation of the MGR 32 are stopped compared to the dog clutch 70. As a result, the generation of agitation loss due to the oil enclosed in the rear case 38 being agitated by the counter gear mechanism 60, the final gear 64, the rear differential gear 66, etc. is prevented or suppressed. The dog clutch 70 is a disconnect mechanism capable of disconnecting the power transmission path between the rear wheels 14 and the MGR 32.

[0023] Figure 2 is a diagram for explaining the main parts of the control function and control system in the vehicle 10. In Figure 2, the vehicle 10 further includes an electronic control device 80 (refer to "ECU" in Figure 1) as a controller including the control device of the vehicle 10. The electronic control device 80 is configured to include a so-called microcomputer having, for example, a CPU, a RAM, a ROM, an input / output interface, etc. The electronic control device 80 includes, for example, an MG ECU 82, a BEV ECU 84, a VSC ECU 86, a DCS ECU 88, etc.

[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, an MGR rotation sensor 90, a wheel speed sensor92, an accelerator opening sensor 94, a brake sensor 96, etc. The various signals are, for example, an MGR rotation speed Nmgr which is the rotation speed of the MGR 32, a left rear wheel rotation speed Nwrl, an accelerator opening θacc, a brake operation amount Bra, etc.

[0025] The electronic control unit 80 outputs various command signals to each device installed in the vehicle 10. These devices include, for example, the rear PCU 36 and the actuator 72. The various command signals include, for example, an MGR torque instruction value for controlling the MGR 32 and an actuator control instruction value for controlling the switching between the engaged and disengaged states of the dog clutch 70.

[0026] BEVECU84 calculates the required acceleration for the vehicle 10 based on the accelerator opening θacc, etc. BEVECU84 also calculates the required deceleration for the vehicle 10 based on the accelerator opening θacc and / or the brake operation amount Bra, etc.

[0027] The BEVECU84 determines whether to switch the drive state based on the requested acceleration, requested deceleration, wheel slip, and the driver's selection of the driving mode. For example, if the requested acceleration or requested deceleration is increased during 2WD control, the BEVECU84 determines whether to switch to the 4WD state and outputs a command to the MGECU82 to synchronize the rotational speeds of the opposing meshing teeth of the dog clutch 70. The MGECU82 increases the MGR rotational speed Nmgr in accordance with the command to synchronize the rotational speeds of the opposing meshing teeth of the dog clutch 70, so that the rotational speed of the first dog tooth 70a becomes the left rear wheel rotational speed Nwrl, which corresponds to the rotational speed of the second dog tooth 70b. In this way, when the electronic control unit 80 determines whether to switch from the 2WD state to the 4WD state, it increases the MGR rotational speed Nmgr so that the rotational speeds of the opposing meshing teeth of the dog clutch 70 are synchronized.

[0028] When BEVECU84 determines that the rotational speeds of the opposing meshing teeth of the dog clutch 70 are synchronized, it outputs a command to DCSECU88 to switch the dog clutch 70 to the engaged state. Since the first dog tooth 70a is connected to MGR32 via the counter gear mechanism 60 and the final gear 64, the rotational speed of the first dog tooth 70a and the MGR rotational speed Nmgr are mutually interchangeable. BEVECU84 determines whether the rotational speeds of the opposing meshing teeth of the dog clutch 70 are synchronized based on whether the absolute value of the difference between the left rear wheel rotational speed Nwrl and the MGR rotational speed Nmgr is less than a predetermined rotational difference. The predetermined rotational difference is, for example, a predetermined threshold that allows it to determine that the rotational speeds of the opposing meshing teeth of the dog clutch 70 are synchronized. DCSECU88 operates the actuator 72 to engage the dog clutch 70 in accordance with the command to switch the dog clutch 70 to the engaged state. Thus, when the electronic control unit 80 determines that the rotational speeds of the opposing meshing teeth of the dog clutch 70 are synchronized, it starts switching the dog clutch 70 to the engaged state.

[0029] Incidentally, a considerable amount of time is required from the time the synchronization of the rotational speeds of the opposing meshing teeth of the dog clutch 70 is determined until the dog clutch 70 is switched to the engaged state and the first dog tooth 70a and the second dog tooth 70b actually mesh. Therefore, when the first dog tooth 70a and the second dog tooth 70b actually mesh, a deviation from the synchronized state may occur, potentially increasing noise and shock. This phenomenon is particularly noticeable when transitioning from 2WD to 4WD when a large acceleration or deceleration is required, as this causes a change in the rotation of the rear wheels 14. It should be noted that it is possible to suppress the generation of noise and shock by employing a mechanical synchronization mechanism in the dog clutch 70, but this would result in the disadvantage of a larger system and increased costs.

[0030] The time required to switch the dog clutch 70 to the engaged state is, as shown in Figure 2, for example, the time from the input of the left rear wheel rotation speed Nwrl signal from the wheel speed sensor 92 (see [1]-1) to the speed calculation by VSCECU86 (see [2]). It is also the time from the input of the MGR rotation speed Nmgr signal from the MGR rotation sensor 90 (see [1]-2) to the speed calculation by MGECU82 (see [3]). It is also the time it takes for the speed calculation result to be transmitted to BEVECU84 (see [4]-1, 2). It is also the synchronization judgment time by BEVECU84 (see [5]). It is also the time it takes for the switching command for the dog clutch 70 associated with the synchronization judgment to be transmitted to DCSECU88 (see [6]). It is also the time it takes for DCSECU88 to output the operation command for actuator 72 (see [7]). It is also the response delay time of actuator 72 (see [8]). Furthermore, this is the operating time of the dog clutch 70 (the time it takes for the dog teeth to move) (see [9]). The times [6]-[9] in Figure 2 above correspond to a reasonable amount of time from when synchronization is determined until the teeth actually engage. This reasonable amount of time is not variable depending on the driving conditions, but is determined to a certain extent uniformly. This reasonable amount of time is a predetermined time TMf from the time when synchronization is determined until the start of engagement of the opposing meshing teeth. However, if we consider that the actual rotational speed of the left rear wheel Nwrl, that is, the rotational speed of the second dog tooth 70b, changes due to acceleration and deceleration at the start of engagement, the times [1]-[5] in Figure 2 above may be included in the predetermined time TMf.

[0031] BEVECU84 calculates the rotational speed of the left rear wheel Nwrl, i.e., the rotational speed of the second dog tooth 70b, which changes during a predetermined time TMf, based on the required acceleration or deceleration. Alternatively, BEVECU84 calculates an estimated (predicted) value of the rotational speed of the second dog tooth 70b after a predetermined time TMf, based on the required acceleration or deceleration. Based on the rotational speed of the second dog tooth 70b which changes during a predetermined time TMf, or the estimated value of the rotational speed of the second dog tooth 70b after a predetermined time TMf, BEVECU84 outputs a command to MGECU82 to synchronize the rotational speed of the first dog tooth 70a with the rotational speed of the second dog tooth 70b after a predetermined time TMf. The MGECU 82 corrects the MGR rotation speed Nmgr so that the rotation speed of the first dog tooth 70a becomes the rotation speed of the second dog tooth 70b after a predetermined time TMf, in accordance with a command to synchronize at the rotation speed of the second dog tooth 70b after a predetermined time TMf. In this way, the electronic control device 80 calculates the rotation speed of the second dog tooth 70b after a predetermined time TMf based on the acceleration / deceleration request to the vehicle 10, and changes the MGR rotation speed Nmgr so that the rotation speed of the first dog tooth 70a becomes the rotation speed of the second dog tooth 70b after a predetermined time TMf.

[0032] Figure 3 is a flowchart illustrating the main part of the control operation of the electronic control device 80, and is a flowchart illustrating the control operation to suppress the generation of noise and shock when engaging the dog clutch 70, and is, for example, executed repeatedly.

[0033] In Figure 3, first, in step S10, which corresponds to the function of BEVECU84 (the step will be omitted hereafter), it is determined whether or not a change occurred during the transition from 2WD control to 4WD state. If the determination in S10 is affirmative, in S20, which corresponds to the functions of MGECU82 and BEVECU84, the MGR rotational speed Nmgr is increased so that the dog clutch 70 starts switching from the disconnected state to the connected state. Next, in S30, which corresponds to the function of BEVECU84, it is determined whether or not the absolute value of the difference between the left rear wheel rotational speed Nwrl and the MGR rotational speed Nmgr is less than a predetermined rotational difference. If the determination in S30 is negative, the process returns to S20. If the determination in S30 is affirmative, in S40, which corresponds to the functions of BEVECU84 and DCSECU88, it is determined that the rotational speeds of the opposing meshing teeth of the dog clutch 70 have synchronized, and the actuator 72 is started to operate to engage the dog clutch 70. Next, in S50, which corresponds to the function of BEVECU84, a predicted value of the left rear wheel rotation speed Nwrl (= rotation speed of the second dog tooth 70b) at a predetermined time TMf after the start of engagement between the first dog tooth 70a and the second dog tooth 70b is calculated based on the required acceleration or required deceleration. Next, in S60, which corresponds to the functions of MGECU82 and BEVECU84, the MGR rotation speed Nmgr is changed to change the rotation speed of the first dog tooth 70a in accordance with the predicted value of the left rear wheel rotation speed Nwrl. Next, in S70, which corresponds to the function of DCSECU88, it is determined whether or not the dog clutch 70 has completed engagement. If the judgment in S70 is negative, the process returns to S40. If the judgment in S70 is positive, the completion of engagement of the dog clutch 70 is recognized in S80, which corresponds to the function of DCSECU88. If the judgment in S10 is negative, the current control state is continued in S90.

[0034] As described above, according to this embodiment, when a switch from 2WD to 4WD is determined, the MGR rotation speed Nmgr is increased so that the rotation speeds of the opposing meshing teeth of the dog clutch 70 are synchronized. When it is determined that the rotation speeds of the opposing meshing teeth are synchronized, the switching to the engaged state of the dog clutch 70 is initiated. In addition, the rotation speed of the second dog tooth 70b after a predetermined time TMf is calculated based on the acceleration / deceleration request. Furthermore, the MGR rotation speed Nmgr is changed so that the rotation speed of the first dog tooth 70a becomes the rotation speed of the second dog tooth 70b after a predetermined time TMf. As a result, the MGR rotation speed Nmgr is corrected so that the opposing meshing teeth mesh in a state of synchronized rotation speed during the transient from the synchronization determination point to the start of meshing of the opposing meshing teeth. Therefore, the generation of noise and shock can be suppressed when engaging the dog clutch 70.

[0035] Although embodiments of the present invention have been described in detail above with reference to the drawings, the present invention is also applicable to other embodiments.

[0036] For example, in the above embodiment, the power source for the front drive unit 20 may be an engine, for example, in addition to or instead of the MGF22. Alternatively, one of the front wheels 12 and rear wheels 14 may be the rear wheel 14 and the other wheel may be the front wheel 12. In this case, a power source that drives only the rear wheel 14, an electric motor that drives only the front wheel 12, and a meshing clutch provided in the power transmission path between the front wheel 12 and the electric motor are provided.

[0037] It should be noted that the above-described embodiment is merely one possible design, 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]

[0038] 10: Vehicle 12: Front wheel (one wheel) 14: Rear wheel (the other wheel) 22: MGF (Power source) 32: MGR (Motor) 70: Dog clutch (meshing clutch) 70a: First dog tooth (meshing tooth on the motor side) 70b: Second dog tooth (meshing tooth on the other wheel side) 80: Electronic control unit (control unit)

Claims

[Claim 1] A control device for a vehicle comprising: a power source that drives only one of the front wheels and the rear wheels; an electric motor that drives only the other of the front wheels and the rear wheels; and a meshing clutch provided in the power transmission path between the other wheel and the electric motor, When it is determined that a switch is needed from a drive state in which only one wheel is driven with the clutch disengaged to a full-wheel drive state in which both the front and rear wheels are driven with the clutch engaged, the rotational speed of the electric motor is increased so that the rotational speeds of the opposing meshing teeth of the clutch become synchronized. A vehicle control device characterized in that, when it is determined that the rotational speeds of the opposing meshing teeth are synchronized, it starts switching the clutch to the engaged state, calculates the rotational speed of the meshing tooth on the other wheel side of the opposing meshing teeth after a predetermined time period from the time it is determined that the opposing meshing teeth are synchronized until the time the opposing meshing teeth start to mesh, based on the request for acceleration or deceleration to the vehicle, and changes the rotational speed of the electric motor so that the rotational speed of the meshing tooth on the electric motor side of the opposing meshing teeth becomes the rotational speed of the meshing tooth on the wheel side after the predetermined time period.

Images