Controller of four-wheel drive vehicle

Abstract

To provide a controller of a four-wheel drive vehicle which suppresses periodic vibration and noise due to an engagement forced force of a differential gear for front wheels from occurring in a two-wheel traveling state at low oil temperatures.SOLUTION: An engagement clutch 38 is connected by the engagement clutch 38 in a two-wheel traveling state when temperature Toil of lubricating-oil is equal to or less than a determination temperature T1 set in advance in a transfer 24 and / or a differential gear 30 for front wheels, or when viscosity V of the lubricating-oil is equal to or more than a determination viscosity V1 set in advance. The differential gear 30 for the front wheels and one of right and left front wheels 14R and 14L are connected by the engagement clutch 38 so as to suppress periodic vibration and noise due to an engagement forced force of the differential gear 30 for front wheels from occurring.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for a four-wheel drive vehicle that, when it is determined that abnormal noise or vibration is occurring during two-wheel drive driving at low temperatures in a four-wheel drive vehicle, engages a mesh clutch between a front wheel differential gear device and the front wheels to suppress the abnormal noise and vibration. [Background technology]

[0002] There are well-known four-wheel drive vehicles in which a part of the torque transmitted from the engine to the transfer is transmitted to the left and right rear wheels via a rear propeller shaft and a rear wheel differential gear device, and another part of the torque transmitted from the engine to the transfer is transmitted to the left and right front wheels via a front propeller shaft and a front wheel differential gear device. For example, the four-wheel drive vehicle described in Patent Document 1 is such a type of vehicle. In addition, a mesh clutch that connects and disconnects the front wheel differential gear device and one of the left and right front wheels of such a four-wheel drive vehicle is provided to improve fuel efficiency. For example, the ADD mechanism shown in Patent Document 2 is an example of such a mesh clutch. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-025197 A [Patent Document 2] Japanese Patent Application Publication No. 08-085355 Summary of the Invention [Problem to be solved by the invention]

[0004] However, for example, in winter, when the temperature of the lubricating oil in the transfer case or the front differential gear unit drops and the viscosity increases, the chain in the transfer case, the front propeller shaft, and the front differential gear unit rotate at low speeds due to drag resistance while driving with four wheels, causing periodic vibrations and abnormal noises due to the meshing forcing force of the front differential gear unit. For example, there are cases where forced vibrations occur once or twice per rotation of the differential case of the front differential gear unit, causing periodic abnormal noises.

[0005] The present invention has been made against the background described above, and its object is to provide a control device for a four-wheel drive vehicle that can suppress the generation of periodic vibrations and abnormal noise caused by the engagement force of the front wheel differential gear device when the vehicle is in two-wheel driving mode with low oil temperature. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the gist of the present invention is to provide a control device for a four-wheel drive vehicle of a type in which a portion of the torque transmitted from the engine to the transfer is transmitted to the left and right rear wheels via a rear propeller shaft and a rear wheel differential gear device, and another portion of the torque transmitted from the engine to the transfer is transmitted to the left and right front wheels via a front propeller shaft and a front wheel differential gear device, and when the vehicle is running on two wheels, a mesh clutch is provided which disengages between the front wheel differential gear device and one of the left and right front wheels, and (b) when the vehicle is running on two wheels, when the temperature of the lubricating oil in the transfer and the front wheel differential gear device falls below a predetermined judgment temperature or the viscosity of the lubricating oil rises to a predetermined judgment viscosity or higher, the mesh clutch is connected. Effect of the Invention

[0007] According to the control device for a four-wheel drive vehicle of the present invention, when the temperature of the lubricating oil in the transfer and the front wheel differential gear unit is equal to or lower than a predetermined judgment temperature or the viscosity of the lubricating oil is equal to or higher than a predetermined judgment viscosity during two-wheel driving, the mesh clutch is engaged. In this way, the front wheel differential gear unit and one of the left and right front wheels are connected by the mesh clutch, thereby suppressing the generation of periodic vibrations and abnormal noise caused by the meshing forcing force of the front wheel differential gear unit. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating the configuration of a four-wheel drive vehicle to which the present invention is applied, and is also a diagram illustrating a main portion of a control system provided in the vehicle. [Diagram 2] 2 is a flowchart illustrating a main part of the control operation of an electronic control device provided in the four-wheel drive vehicle of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately. EXAMPLES

[0010] FIG. 1 is a diagram illustrating the configuration of a four-wheel drive vehicle 10 to which the present invention is applied, and is also a diagram illustrating the main parts of a control system provided in the four-wheel drive vehicle 10.

[0011] In FIG. 1, a four-wheel drive vehicle 10 is, for example, a vehicle based on a front-mounted engine and rear-wheel drive (FR), and is equipped with a vehicle power transmission device 18 that transmits power from an engine 12 as a driving power source for traveling to a pair of left and right front wheels 14L, 14R (front wheels 14 when no particular distinction is made) as auxiliary drive wheels and a pair of left and right rear wheels 16L, 16R (rear wheels 16 when no particular distinction is made) as main drive wheels.

[0012] The vehicle power transmission device 18 includes an automatic transmission 22 having a torque converter 20 connected to the engine 12, a transfer (power distribution device) 24 connected to the output side of the automatic transmission 22 and distributing the power transmitted from the automatic transmission 22 to the front wheels 14 and the rear wheels 16, a front propeller shaft 26 and a rear propeller shaft 28 that transmit the power distributed by the transfer 24 to the front wheels 14 and the rear wheels 16, respectively, a front wheel differential gear device 30 and a rear wheel differential gear device 32 that are connected to the front propeller shaft 26 and the rear propeller shaft 28, respectively, and a pair of left and right front wheel axles 34L, 34R (referred to as front wheel axles 34 when no particular distinction is made) and a pair of left and right rear wheel axles 36L, 36R (referred to as rear wheel axles 36 when no particular distinction is made) that transmit the power transmitted via the front wheel differential gear device 30 and the rear wheel differential gear device 32 to the front wheels 14 and the rear wheels 16, respectively.

[0013] In the vehicle power transmission device 18 configured in this manner, the power generated by the engine 12 is transmitted to the pair of left and right front wheels 14 and rear wheels 16, respectively, via power transmission paths that include the torque converter 20, the automatic transmission 22, the transfer 24, the front propeller shaft 26 and the rear propeller shaft 28, the front wheel differential gear device 30 and the rear wheel differential gear device 32, a pair of left and right front wheel axles 34, and a pair of left and right rear wheel axles 36.

[0014] The front wheel differential gear device 30 has a mesh clutch (front differential ADD) 38 as a so-called ADD (Automatic Disconnecting Differential) mechanism for switching the on / off state of the front wheel axle 34R, which also functions as the output shaft of the front wheel differential gear device 30. The mesh clutch 38 is provided between the front wheel axle 34R1 connected to the front wheel differential gear device 30 and the front wheel axle 34R2 connected to the front wheels 14. The front wheel differential gear device 30 and the mesh clutch 38 constitute a vehicle differential device 41.

[0015] The engine 12 is an internal combustion engine such as a gasoline engine or a diesel engine that generates driving force by burning fuel injected into the cylinder. The torque converter 20 is a fluid power transmission device that includes, for example, a pump wheel connected to a crankshaft of the engine 12, a turbine wheel connected to an input shaft of an automatic transmission 22, and a stator wheel fixed to a transmission case (not shown) via a one-way clutch, and transmits power between the pump wheel and the turbine wheel via a fluid. The automatic transmission 22 is an automatic transmission that includes, for example, a plurality of friction engagement elements, selectively establishes a plurality of gear ratios according to a combination of engagement and release of the friction engagement elements, and changes the speed of the driving force input from the input shaft and outputs it.

[0016] The transfer 24 responds to, for example, an operation position Pdial of a drive state changeover dial switch 170 detected by an operation position sensor 168 described later, and transmits the power from the automatic transmission 22 only to the rear wheels 16 in a two-wheel driving state (mode), or distributes the power to each of the front wheels 14 and the rear wheels 16 in a four-wheel driving state (mode). The transfer 24 also has a function as an auxiliary transmission that establishes, for example, a high-speed gear stage (high-speed shift stage) H or a low-speed gear stage (low-speed shift stage) L to change the speed of the power from the automatic transmission 22 and transmit it to the rear stage.

[0017] The power (torque) from the engine 12 distributed by the transfer 24 is input to the front wheel differential gear device 30 via the front propeller shaft 26. A drive pinion 104, which is a bevel gear, is provided at an end of the front propeller shaft 26, and the gear of the drive pinion 104 is configured to mesh with a ring gear 106, which is a bevel gear of the front wheel differential gear device 30. This ring gear 106 is fixed to a differential case (diff case) 108, and rotates (revolves) integrally around the axis of the front wheel axle 34. This front wheel axle 34 is configured to include a pair of left and right front wheel axles 34L, 34R, and the front wheel axle 34R is further divided into an axle 34R1 connected to the front wheel differential gear device 30 and an axle 34R2 connected to the front wheels 14r.

[0018] The mesh clutch 38 switches between a power transmission state in which power is transmitted between the front axle 34R1 mechanically connected to the front differential gear device 30 and the front axle 34R2 mechanically connected to the front wheels 14R, and a power interruption state in which power transmission is interrupted. The mesh clutch 38 is, for example, a known dog clutch that selectively connects and disconnects the front axle 34R1 and the front axle 34R2, and functions as an on / off switching mechanism that selectively switches between disconnection and connection of power transmission between the front differential gear device 30 and the front wheels 14R. In an open state (disconnected state), the mesh clutch 38 interrupts the power transmission path between the front propeller shaft 26 and the front wheels 14L, 14R by idling the axle 34R1, while in a connected state, it connects the power transmission path between the front propeller shaft 26 and the front wheels 14L, 14R. The dog clutch 38 is disengaged in, for example, a two-wheel drive state, and blocks the power transmission path between the front wheel differential gear unit 30 and the front wheels 14R.

[0019] Specifically, the ADD device 110 includes the mesh clutch 38 and an electric motor 112 for switching the operating state of the mesh clutch 38, i.e., between a connected state and a disconnected state. In the ADD device 110, the electric motor 112 is driven to selectively switch the position of a clutch sleeve 116 having internal teeth between a release position shown in FIG. 1 in which the mesh clutch 38 is released, and a connected position in which the front wheel differential gear device 30 and the front wheels 14R are connected, thereby switching between a connected state in which the front wheel axle 34 and the front propeller shaft 26 are in a power transmission state, and a disconnected state in which power transmission between the front wheel axle 34 and the front propeller shaft 26 is disconnected.

[0020] When the front axle 34 and the rear axle 36 are connected by the ADD device 110, a portion of the torque (driving force) transmitted from the engine 12 to the transfer 24 is transmitted to the front wheel differential gear device 30 via the front propeller shaft 26, and then transmitted to the left and right front wheels 14 via the left and right front axles 34. Another portion of the torque (driving force) transmitted to the transfer 24 is transmitted to the left and right rear wheels 16 via the rear propeller shaft 28, the rear wheel differential gear device 32, and the left and right rear axles 36, respectively, so that the vehicle 10 is in a front-rear wheel drive state (four-wheel drive state).

[0021] On the other hand, when a second dog clutch device (not shown) in the transfer 24 is disengaged, the power from the engine 12 is transmitted only to the left and right rear wheels 16 by the transfer 24, so that the vehicle 10 is in a rear-wheel drive state (two-wheel drive state). At this time, if the front wheel axle 34 and the rear wheel axle 36 are connected by the ADD device 110, the front wheel axle 34, the front wheel differential gear device 30, the front propeller shaft 26, the second output shaft in the transfer 24, the driven gear, the chain, the drive gear, and the like are rotated by the rotational force from the left and right front wheels 14. This results in a torque in the deceleration direction (drag torque) being applied to the vehicle 10, which reduces fuel efficiency. For this reason, in the vehicle 10 of this embodiment, for example, in conjunction with being in a two-wheel drive state, the mesh clutch 38 is disengaged, and the ADD device 110 cuts off the connection between the front axle 34R1 connected to the front differential gear device 30 and the front axle 34R2 connected to the front wheels 14. At this time, power transmission is cut off in the front differential gear device 30, preventing co-rotation of the front propeller shaft 26, the second output shaft in the transfer 24, the chain, the drive gear, etc., and improving fuel efficiency.

[0022] 1, the four-wheel drive vehicle 10 is provided with an electronic control device 130 including a four-wheel drive vehicle control device for switching between a two-wheel drive state and a four-wheel drive state. The electronic control device 130 is configured to include, for example, a so-called microcomputer, and performs signal processing according to a pre-stored program to execute output control of the engine 12, shift control of the automatic transmission 22, switching control of the dog clutch 38, and the like. The electronic control device 130 is functionally provided with an abnormal noise / vibration generation condition satisfaction determination unit 132, a two-wheel drive state determination unit 134, and a dog clutch control unit 136.

[0023] The electronic control device 130 is supplied with, for example, a signal indicating the engine rotation speed Ne detected by an engine rotation speed sensor 162, a signal indicating the vehicle speed V corresponding to the output rotation speed Npr of the rear propeller shaft 28 detected by a rear propeller rotation speed sensor 164, signals indicating the wheel speeds Nfr, Nfl, Nrr, Nrl corresponding to the rotation speed Nw of each wheel (i.e., front wheels 14R, 14L, rear wheels 16R, 16L) detected by each wheel speed sensor 166, a signal indicating the operation position Pdial of the drive state changeover dial switch 170 detected by an operation position sensor 168, and a signal indicating the power transmission state in the transfer 24 detected by a drive state detection switch 172, such as a two-wheel drive state S2WD and a four-wheel drive state S4WD.

[0024] The electronic control device 130 also outputs, for example, an engine output control command signal Se for controlling the output of the engine 12, a gear change control command signal St for controlling the gear change of the automatic transmission 22, a high / low switching control command signal Shl for switching the gear stage of the sub-transmission to a high-speed gear stage H or a low-speed gear stage L by operating a first mesh clutch device via a first shift fork shaft by a shift actuator in the transfer 24, a drive state switching control command signal S2-4 for switching the drive state of the transfer 24 to a two-wheel drive state or a four-wheel drive state by operating the second mesh clutch device via a second shift fork shaft by the shift actuator 84, and a drive state switching control command signal S2-5 for switching the drive state of the transfer 24 to a two-wheel drive state or a four-wheel drive state by operating the mesh clutch 38 by the electric motor 112. By engaging the mesh clutch 38, an ADD switching control command signal Sadd is output for switching the power transmission path between the front wheel differential gear device 30 and the front wheels 14 on and off, and a synchronization control command signal Ssync is output for quickly synchronizing the rotation of the front wheel axle 34R1 and the rotation of the front wheel axle 34R2 by the electric motor 114 when the mesh clutch 38 is engaged.

[0025] The drive state changing dial switch 170 is, for example, a dial-type switch that is provided near the driver and manually operated by the driver, and has three operating positions Pdial for instructing a change to any one of a two-wheel drive state in high-speed gear stage H (H-2WD), a four-wheel drive state in high-speed gear stage H (H-4WD), and a four-wheel drive state in low-speed gear stage L (L-4WD).

[0026] Fig. 2 is a flow chart for explaining the main part of the control operation of the electronic control device 130. In Fig. 2, first, in step S10 (hereinafter, step will be omitted) corresponding to the abnormal noise / vibration generation condition establishment determination unit 132, it is determined whether the temperature Toil of the lubricating oil in the transfer 24 and / or the front wheel differential gear device 30 detected by a temperature sensor (not shown) is equal to or lower than a predetermined determination temperature T1, or whether the viscosity V of the lubricating oil detected by a viscosity sensor (not shown) is equal to or higher than a predetermined determination viscosity V1. The determination temperature T1 and the determination viscosity V1 are boundary values ​​at which it is sensuously recognized that periodic vibration and abnormal noise due to the meshing forcing force of the front wheel differential gear device 30 occurs during two-wheel driving at low temperatures, and are values ​​previously obtained experimentally.

[0027] If the determination in S1 is negative, S1 is repeated, but if the determination is positive, in S2 corresponding to the two-wheel drive state determination unit 134, it is determined whether the four-wheel drive vehicle 10 has been switched to a two-wheel drive state (mode), for example, whether the drive state in the transferer 24 is in a two-wheel drive state or not. If the determination in S2 is negative, S1 and subsequent steps are repeated, but if the determination is positive, in S3 corresponding to the mesh clutch control unit 136, the mesh clutch 38 between the front wheel axle 34R1 connected to the front wheel differential gear device 30 and the front wheel axle 34R2 connected to the front wheels 14 is engaged to set the four-wheel drive state (mode).

[0028] As described above, according to this embodiment, when the temperature Toil of the lubricant in the transfer 24 and / or the front wheel differential gear device 30 becomes equal to or lower than a preset judgment temperature T1 and / or the viscosity V of the lubricant becomes equal to or higher than a preset judgment viscosity V1 during two-wheel driving, the mesh clutch 38 is engaged by the mesh clutch 38. In this manner, the front wheel differential gear device 30 is connected to one of the left and right front wheels 14R and 14L, thereby suppressing the generation of periodic vibrations and abnormal noises caused by the meshing forcing force of the front wheel differential gear device 30.

[0029] Although the embodiment of the present invention has been described in detail above with reference to the drawings, the present invention can be applied to other embodiments.

[0030] For example, in the above-described embodiment, the dog clutch 38 is provided on the front axle 34R side, but it may be provided on the front axle 34L side.

[0031] In addition, in the above-described embodiment, the electric motor 112 is used to switch the mesh clutch 38, but it may be configured so that switching is performed by an electromagnetic solenoid.

[0032] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of symbols]

[0033] 10: four-wheel drive vehicle, 12: engine, 14: front wheel L, 14R, 16L, 16R: rear wheels, 28: rear propeller shaft, 30: front wheel differential gear device, 34L: left front wheel axle, 34R1, 34R2: right front wheel axle, 38: mesh clutch, 110: ADD device, 130: electronic control device (control device), 132: abnormal noise / vibration generation condition establishment determination unit, 134: two-wheel drive state determination unit, 136: mesh clutch control unit

Claims

[Claim 1] A control device for a four-wheel drive vehicle of the type in which a part of the torque transmitted from the engine to the transfer is transmitted to the left and right rear wheels via a rear propeller shaft and a rear wheel differential gear device, and another part of the torque transmitted from the engine to the transfer is transmitted to the left and right front wheels via a front propeller shaft and a front wheel differential gear device, and a dog clutch is provided which releases the front wheel differential gear device from a drive shaft of one of the left and right front wheels during two-wheel driving, When the temperature of the lubricating oil in the transfer and the front wheel differential gear device is equal to or lower than a predetermined judgment temperature, or when the viscosity of the lubricating oil is equal to or higher than a predetermined judgment viscosity during two-wheel driving, the dog clutch is engaged. A control device for a four-wheel drive vehicle comprising:

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