Vehicle power transmission control device

Abstract

To provide a driving force transmission control device for a vehicle capable of securing traveling stability and driving force when a four-wheel drive vehicle or the like travels on a bad road, as well as, miniaturizing the device by diverting existing components.SOLUTION: A driving force transmission control device for a vehicle comprises: a distribution mechanism 3 for distributing torque output from an engine 2 that is composed of a ring gear R to which torque is input from the engine 2 and which outputs the torque to a rear wheel 5 side, a carrier C which outputs the torque to a front wheel 4 side, and a sun gear S connected with a motor 9, and that limits a differential action of the differential mechanism; a lock mechanism 10 for limiting a differential action of the differential mechanism; and a controller 15. The controller 15 includes a driving force control unit configure to: cause the engine 2 to output a constant driving force of a required driving force required for a vehicle in a state where the differential action is limited; cause the motor 9 to output a remaining driving force other than the driving force output by the engine 2 of the required driving force; and control the remaining driving force so as to maintain a vehicle speed of the vehicle at a target vehicle speed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a driving force transmission control device that distributes and transmits torque output from a driving force source to left and right wheels, front and rear wheels, etc.

Background Art

[0002] In a four-wheel drive vehicle that distributes and transmits the driving torque output from an engine to the rear wheels and the front wheels, the rear wheels and the front wheels are mechanically connected. Therefore, in order to avoid the so-called tight corner braking phenomenon during cornering where a rotational speed difference occurs between the rear wheels and the front wheels, a differential mechanism is provided between the rear wheels and the front wheels to enable differential rotation of these wheels. On the other hand, when a differential mechanism is provided, if the grip force of one of the wheels decreases, such as when one wheel slips, a state called torque loss occurs where the driving torque of the other wheels decreases. In that case, the driving force of the entire vehicle decreases, and the running stability is impaired. In particular, when driving on a road with severe unevenness (rough road), a steep downhill, a snowy road, a slippery road surface, etc. (hereinafter, these are collectively referred to as bad roads), it is necessary for all wheels to have driving force. Therefore, usually, when a differential mechanism (center differential mechanism or center diff) that enables differential rotation between the rear wheel side and the front wheel side is provided, a differential limiting mechanism (diff lock mechanism) such as a clutch or a brake for limiting the differential action is provided.

[0003] One example of this is described in Patent Documents 1 and 2. The device described in Patent Document 1 distributes the drive torque input from the engine via the transmission to the front and rear wheels using a planetary gear mechanism, and transmits the torque from the planetary gear mechanism to the output shaft (or propeller shaft) on the front wheel side via a transfer consisting of a winding transmission mechanism or the like. The planetary gear mechanism uses, for example, a sun gear, a ring gear, and a carrier as rotating elements, and a clutch is provided between the ring gear and the output shaft of the transmission, with the ring gear being the input element. The output shaft (or propeller shaft) on the rear wheel side is connected to the sun gear, making the sun gear the first output element, and the carrier is further connected to the transfer, making it the second output element. Another clutch is provided between the output shaft of the transmission and the sun gear. Therefore, when the two clutches are engaged, the ring gear and sun gear are connected, integrating the entire planetary gear mechanism. This creates a state similar to the output shafts on the front and rear wheel sides being directly connected to the transmission's output shaft, resulting in a so-called direct-drive four-wheel drive system where the front and rear wheels do not rotate differentially. In this direct-drive four-wheel drive system, so-called torque loss, where one wheel slips or spins freely, reducing the torque on the other wheels, is avoided, resulting in improved off-road capability.

[0004] A differential lock, which limits the differential action of the differential mechanism that distributes torque to the front and rear wheels, is usually performed when entering rough roads, but it is also preferable to lock the differential when encountering slippery surfaces such as snowy roads. Conversely, after passing over such surfaces, it is preferable to release the differential lock to avoid the tight corner braking phenomenon. Patent Document 2 describes a device that automatically performs such differential locking and release based on data reflecting road surface conditions, such as the rotation speed of the front and rear wheels. The inventions in Patent Documents 1 and 2 above can limit the differential action of the differential mechanism that distributes torque to the front and rear wheels, thereby ensuring driving torque for all front and rear wheels and improving off-road capability. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2001-260684 [Patent Document 2] Japanese Patent Publication No. 187623 / 1983 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, when driving on rough roads (especially roads with significant bumps or inclines), the driver's seating position may be unstable, making it difficult to operate the accelerator and brake pedals to control the driving force and vehicle speed, which can result in improper control of the driving force and vehicle speed. Therefore, a control system sometimes referred to as crawl control has been developed. This type of control (hereinafter referred to as crawl control) is initiated by the driver when driving on rough roads, and the engine output and braking force are automatically controlled to maintain the vehicle speed at a predetermined target low speed, thereby reducing the burden on the driver when driving on rough roads.

[0007] However, four-wheel drive vehicles equipped with crawl control typically have an engine to generate significant driving force. Therefore, even if crawl control controls engine output, the control response is not always high for an engine that burns fuel to produce torque. As a result, crawl control may not be able to stabilize the driving force or vehicle speed at the target value when driving on rough terrain.

[0008] Furthermore, the device described in Patent Document 2 has a first motor connected to the input side of the transmission in addition to the engine, and a second motor connected to the output shaft on the front wheel side. Although the motors have a smaller output torque compared to the engine, they have superior control response, so if these motors are used for driving, it is possible to subtly and quickly control the driving force when driving on rough roads with differential lock to stabilize the vehicle speed at the target speed. However, the first motor and the second motor described in Patent Document 2 are newly added to additionally control the driving force or regenerative braking force. Therefore, the configuration of the invention in Patent Document 2 may result in an increase in the number of components of the drive system or the vehicle as a whole, potentially making the vehicle larger and heavier.

[0009] This invention was made in view of the above-mentioned technical problems, and aims to provide a vehicle drive force transmission control device that ensures driving stability and driving force when four-wheel drive vehicles and the like travel on rough roads, and also enables miniaturization of the device by repurposing existing parts. [Means for solving the problem]

[0010] This invention provides a vehicle drive force transmission control device that, in order to achieve the above objective, comprises a distribution mechanism for distributing torque output from a drive force source to a first output side and a second output side, and a rotating machine for changing the torque distribution ratio to the first output side and the second output side by the distribution mechanism, wherein the distribution mechanism is composed of a differential mechanism that performs a differential action with a first rotating element to which torque is input from the drive force source and which outputs torque to the first output side, a second rotating element to which torque is output to the second output side, and a third rotating element to which the rotating machine is connected, and selectively connects at least two of the rotating elements of the first rotating element, the second rotating element and the third rotating element The invention further comprises a locking mechanism that limits the differential action of the differential mechanism, and a controller that controls the locking mechanism and controls the drive source and the rotating machine when the locking mechanism operates in a manner that limits the differential action of the differential mechanism, wherein the controller includes a drive force control unit that, while the differential action of the differential mechanism is limited by the locking mechanism, causes the drive source to output a certain amount of the required drive force required for the vehicle, and causes the rotating machine to output the remaining drive force other than the drive force output by the drive source, and controls the remaining drive force to maintain the vehicle speed at a predetermined target speed.

[0011] In this invention, the vehicle has a total of four wheels, including front wheels and rear wheels, the distribution mechanism is a center differential that distributes torque to the front wheels and the rear wheels, and the controller may further include a rough road determination unit that determines rough road conditions based on the difference in rotational speed between the front wheels and the rear wheels, and a lock instruction unit that operates the lock mechanism to limit the differential action of the differential mechanism when the rough road determination unit determines that the road is rough.

[0012] Alternatively, in this invention, the vehicle has a total of four wheels, including front and rear wheels, the distribution mechanism is a center differential that distributes torque to the front and rear wheels, the vehicle further has a manual lock operation unit that operates the lock mechanism to limit the differential action of the differential mechanism by manual operation, and the controller may further include a rough road determination unit that determines a rough road based on the difference in rotational speed between the front and rear wheels, and a lock notification unit that notifies the driver of the vehicle to operate the lock mechanism to limit the differential action of the differential mechanism when the rough road determination unit determines that the road is rough.

[0013] In this invention, the target vehicle speed may be a predetermined constant vehicle speed.

[0014] In this invention, the target vehicle speed may be the vehicle speed determined from the amount of acceleration and deceleration performed by the driver of the vehicle.

[0015] In this invention, the driving force source may be an internal combustion engine, and the rotating machine may be an electric motor with a power generation function. [Effects of the Invention]

[0016] In the vehicle power transmission control device of this invention, a locking mechanism restricts and releases (allows) the differential action of the differential mechanism. When the differential action is permitted, the torque distribution ratio by the differential mechanism is controlled by the torque of the rotating machine. For example, increasing the torque of the rotating machine increases the distribution ratio to one output side and decreases the distribution ratio to the other output side, and conversely, decreasing the torque of the rotating machine decreases the distribution ratio to one output side and increases the distribution ratio to the other output side. In contrast, when the locking mechanism is activated and the differential action of the differential mechanism is restricted, the entire differential mechanism rotates as a single unit, so the torque output by the rotating machine is transmitted as driving force to the first output side and the second output side.

[0017] That is, the rotary machine together with the driving power source generates the driving torque for running. In that case, the driving power source outputs a certain driving power (so-called basic driving power) of the required driving power, and the rotary machine takes charge of and outputs the insufficient driving power (residual driving power). As a result, the rotary machine only needs to output a small driving power, enabling responsive driving force control or delicate vehicle speed control. Also, since the rotary machine is an existing component for controlling the torque distribution ratio by the distribution mechanism, it is possible to miniaturize the overall configuration of the device by diverting or sharing components.

[0018] Further, in this invention, if the distribution mechanism is configured as a center differential that distributes torque to the front and rear wheels and allows differential rotation of those wheels, it becomes easy to drive with a stable vehicle speed when running on so-called bad roads such as roads with severe unevenness or steep slopes, and the so-called bad road traversability can be improved.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic diagram showing the main part of an example of a vehicle that can be the subject of this invention. [Figure 2] It is a collinear diagram of the planetary gear mechanism constituting the distribution mechanism. (a) shows the operating state when running on a flat road without differential restriction, (b) shows the operating state when differential rotation occurs between the front and rear wheels on a bad road, and (c) shows the operating state when differential restriction is performed and driving power is output by the engine and the motor. [Figure 3] It is a block diagram for explaining the functional configuration of the ECU corresponding to the controller of this invention. [Figure 4] It is a flowchart for explaining an example of the control executed in this invention.

Modes for Carrying Out the Invention

[0020] Embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are merely examples of implementing the present invention and do not limit the present invention.

[0021] FIG. 1 schematically shows an example of a vehicle 1 equipped with a driving force transmission control device according to the present invention. The driving force transmission control device according to the present invention includes a distribution mechanism 3 that distributes the torque output from the driving force source 2 to a first output side and a second output side. The first output side and the second output side may be the front wheel 4 side and the rear wheel 5 side, or may be the right wheel and the left wheel. The example shown in FIG. 1 is an example configured to distribute and transmit torque to the front wheel 4 and the rear wheel 5. Therefore, the vehicle 1 shown here is a four-wheel drive vehicle, and the distribution mechanism 3 is a center differential.

[0022] The driving force source 2 may be any power unit that can output a driving force for traveling by appropriately burning fuel, and may be an internal combustion engine (ENG) using gasoline, light oil, hydrogen, or the like as fuel. Hereinafter, the driving force source 2 will be referred to as the engine 2. The engine 2 is configured to be able to electrically control the intake air amount and the fuel supply amount (injection amount). Therefore, its output can be controlled not only based on the operation by the driver (not shown) of the vehicle 1, but also, if necessary, without regard to the driver's operation.

[0023] The distribution mechanism 3 is composed of a differential mechanism that performs differential action using three rotating elements. This differential mechanism can be a planetary gear mechanism or a differential gear mechanism in which a pinion gear held inside the differential case meshes with a pair of left and right side gears. Figure 1 shows an example where the distribution mechanism 3 is composed of a single-pinion type planetary gear mechanism. Therefore, the distribution mechanism 3 shown in Figure 1 includes a sun gear S, a ring gear R which is an internal gear arranged concentrically with respect to the sun gear S, and a carrier C positioned between the sun gear S and the ring gear R, which rotates and holds the pinion gears meshing with the sun gear S and the ring gear R in a rotatable manner. In the example shown in Figure 1, torque is transmitted from the engine 2 to the ring gear R. Furthermore, a rear wheel output shaft 6, which outputs torque to the rear wheels 5, is connected to the ring gear R. The ring gear R corresponds to the first rotating element in this embodiment of the invention, and the torque output directed toward the rear wheel 5 corresponds to the output to the first output side in this embodiment of the invention.

[0024] Carrier C corresponds to the second rotating element in this embodiment of the invention and is configured to distribute and output torque from carrier C to the front wheel 4, which corresponds to the second output side. A transfer 8 is provided to transmit torque from carrier C to the front wheel output shaft 7. In the example shown in Figure 1, the transfer 8 is composed of a wrap-around transmission mechanism that transmits torque by a chain or belt, for example, a sprocket is attached to carrier C, and a transmission member wrapped around it is wrapped around another sprocket attached to the front wheel output shaft 7. The front wheel output shaft 7 is arranged parallel to the rotational center axis of the distribution mechanism 3.

[0025] The torque input to the ring gear R is distributed to the carrier C. A rotating machine 9 is connected to the sun gear S to control the distribution ratio between the torque distributed to the front wheel output shaft 7 via the carrier C and the torque distributed from the ring gear R to the rear wheel output shaft 6. Specifically, the rotating machine 9 is an electric motor or an electric motor with a power generation function (motor-generator), and hereafter the rotating machine 9 will be referred to as motor 9. This motor 9 is, for example, a permanent magnet type synchronous motor, and is connected to a power storage device (battery) (not shown) via an inverter, and its rotational speed and torque are controlled by the inverter, etc.

[0026] Furthermore, the distribution mechanism 3 is provided with a locking mechanism 10 that selectively limits its differential action. The locking mechanism 10 is a mechanism that limits differential rotation by connecting at least two rotating elements in the planetary gear mechanism that constitutes the distribution mechanism 3. A friction clutch is one example of this mechanism, and in the example shown in Figure 1, it is configured to selectively connect the ring gear R and the carrier C. The locking mechanism 10 can also be switched between engaged and disengaged states by hydraulic or electromagnetic force, and its control can be performed electrically.

[0027] Vehicle 1 is equipped with an accelerator pedal 11 for acceleration and deceleration, a brake pedal 12 for braking, and a steering mechanism (not shown), similar to a normal vehicle. Furthermore, a manual switch 13 is provided as a manual locking operation unit for switching the locking mechanism 10 between an engaged state (locked state) and a released state (unlocked state). In addition, although not specifically shown, various sensors are provided in Vehicle 1 to detect the amount of depression of the accelerator pedal 11, which represents the required driving force, the amount of depression or force of the brake pedal 12, and the rotational speed of the front wheels 4 and rear wheels 5. Furthermore, notification means 14 is provided in Vehicle 1 to inform the driver of the vehicle's driving status, such as when the locking mechanism 10 should be activated or when the road is rough, using images or sound.

[0028] Here, we will explain the torque distribution function of the distribution mechanism 3 described above, and the control of the torque distribution ratio by the motor 9. Figure 2 shows a collinear diagram of the planetary gear mechanism that constitutes the distribution mechanism 3. The collinear diagram is a diagram in which three lines are drawn parallel to each other: a line representing the sun gear S, a line representing the carrier C, and a line representing the ring gear R. The distance between the line representing the sun gear S and the line representing the carrier C is set to "1", and the distance between the line representing the carrier C and the line representing the ring gear R is set to the gear ratio of the planetary gear mechanism (the ratio of the number of teeth of the sun gear S to the number of teeth of the ring gear R). The position on these three lines, from a baseline perpendicular to these three lines, indicates the rotational speed of each rotating element.

[0029] Figure 2(a) shows the state in which the lock mechanism 10 is released and the distribution mechanism 3 is unlocked, and the vehicle is running on the driving force output by the engine 2. Torque Teg transmitted from the engine 2 acts on the ring gear R in the forward rotation direction. In this state, when the motor 9 is made to function as a motor and output torque in the forward rotation direction, torque Ts acts on the sun gear S in the forward rotation direction. Figure 2(a) shows the state in which the rotational speeds of the ring gear R and the sun gear S are the same, and the point where the line L1 connecting the points of these rotational speeds intersects with the vertical line representing the carrier C indicates the rotational speed of the carrier C, and this rotational speed is the same as the rotational speeds of the ring gear R and the sun gear S.

[0030] The torque relationship can be explained by considering the above straight line L1 as a lever with the sun gear S as the point of force application, the ring gear R as the fulcrum, and the carrier C as the point of application. A torque Tc appears on the carrier C, which is the torque Ts of the sun gear S increased according to the gear ratio of the planetary gear mechanism. This becomes the driving force of the front wheel 4. In response to this, a reaction force TRr acts on the ring gear R against the torque Tc that rotates the carrier C in the forward rotation direction. Therefore, the torque Tr of the ring gear R is the sum of the torque Teg from the engine 2 and the reaction force TRr mentioned above, and this becomes the driving force of the rear wheel 5. Consequently, by increasing or decreasing the torque of the motor 9, the torque Tc of the carrier C and the torque of the ring gear Tr, which are the torques that drive the front wheel 4, as well as their ratio (i.e., distribution ratio), change.

[0031] Figure 2(b) shows the rotational speeds of the sun gear S, ring gear R, and carrier C when differential rotation occurs between the front wheels 4 and rear wheels 5 while driving on rough terrain. The state where the front wheels 4 and rear wheels 5 maintain grip and no differential rotation occurs is shown by the straight line L1. When driving on rough terrain, for example, if the rear wheels 5 tend to slip or lock, the rotational speed of the ring gear R increases or decreases compared to the rotational speed when no differential rotation occurs, as shown by the dashed line L2 in Figure 2(b). Accordingly, the rotational speeds of the motor 9 and sun gear S increase or decrease. Also, for example, if the front wheels 4 tend to slip or lock, the rotational speed of the carrier C increases or decreases compared to the rotational speed when no differential rotation occurs, as shown by the dashed line L3 in Figure 2(b). Accordingly, the rotational speeds of the motor 9 and sun gear S increase or decrease. Therefore, when driving on rough roads with the differential action of the distribution mechanism 3 permitted, it is necessary to subtly and frequently control the rotational speed or torque of the engine 2 and motor 9 in order to maintain a constant vehicle speed.

[0032] Figure 2(c) shows the state in which the locking mechanism 10 described above is activated to limit the differential of the distribution mechanism 3. In this state, the entire planetary gear mechanism constituting the distribution mechanism 3 rotates as a single unit, and its operating state is represented by a straight line L1. In this state, the torque distribution ratio cannot be changed (controlled) by the motor 9, but the motor 9 can be operated as a driving force source for propulsion. Therefore, the torques Tmg and Teg of the engine 2 and motor 9 are evenly distributed to the carrier C and ring gear R (front wheel 4 side and rear wheel 5 side), and the sum of these torques becomes the torque Tc of the carrier C and the torque Tr of the ring gear R.

[0033] This embodiment of the invention is configured to control vehicle speed or driving torque when driving on rough roads by effectively utilizing the above-described functions of the distribution mechanism 3 and motor 9. The control when driving on rough roads includes rough road detection, notification of rough roads, differential limiting by the lock mechanism 10, and output control of the engine 2 and motor 9 to output the required driving force, and an electronic control unit (ECU) 15 is provided to perform this control. The ECU 15 corresponds to the controller in this embodiment of the invention and is mainly composed of a microcomputer consisting of computing elements (CPU), memory elements (RAM, ROM), interfaces, etc. It is configured to perform calculations according to a preset program using data obtained from the various sensors mentioned above and data that has been stored in advance, and to output the result of the calculation as a control command signal.

[0034] Examples of input data include the rotational speed of the front wheels 4, the rotational speed of the rear wheels 5, the accelerator pedal opening (the amount the accelerator pedal 11 is pressed) or the resulting requested driving force, and the on / off signal of the manual switch 13. Pre-stored data includes the difference in rotational speed between the front wheels 4 and the rear wheels 5, a reference value for determining rough terrain based on the frequency of that difference in rotational speed, and a determination value for determining whether the determined rough terrain requires differential limiting by the locking mechanism 10. Furthermore, examples of output control command signals include signals for operating the locking mechanism 10, signals for controlling the output torque of the engine 2 and motor 9, and signals for instructing the content to be announced by the notification means 14.

[0035] The ECU 15 uses the input data and pre-stored data described above to determine if the road is rough. If the determination is correct, it either limits the differential of the distribution mechanism 3 using the lock mechanism 10, or notifies the driver that the lock mechanism 10 should be activated. When differential limiting is performed by the distribution mechanism 3, the ECU 15 is configured to control the rotational speed or output torque of the engine 2 or motor 9 necessary to maintain the target vehicle speed. In other words, as shown in Figure 3, the ECU 15 has a functional configuration comprising a rough road determination unit 15a, a lock instruction unit 15b, a lock notification unit 15c, and a drive force control unit 15d.

[0036] The rough road detection unit 15a determines whether the road surface currently being driven on is a rough road or not, based on the difference in rotational speed between the front wheels 4 and the rear wheels 5 and the frequency of occurrence of this difference in rotational speed. If the difference (absolute value) in rotational speed between the front wheels 4 and the rear wheels 5 exceeds a predetermined value, it is determined that a difference in rotation is occurring, and the number of times this determination is made within a predetermined unit of time is defined as the frequency of occurrence. As mentioned above, the determination of a rough road can be made by comparing the detected value with a pre-prepared reference value.

[0037] The lock instruction unit 15b is configured to output a control command signal to the lock mechanism 10 and operate it when the determined rough road is rough enough to require limiting the differential action of the distribution mechanism 3. The lock instruction unit 15b is a control unit that operates the lock mechanism 10 to limit the differential action of the distribution mechanism 3 without the driver's instruction, whereas the lock notification unit 15c is a control unit that notifies the driver to operate the lock mechanism 10 to limit the differential action of the distribution mechanism 3 when a rough road is determined to be present. Therefore, the lock notification unit 15c may be provided together with the lock instruction unit 15b, or it may be provided in place of the lock instruction unit 15b.

[0038] The drive force control unit 15d is configured to control the output of the engine 2 and motor 9 when driving on rough roads with the lock mechanism 10 activated to limit the differential of the distribution mechanism 3. One example of this control is to maintain the vehicle speed at a predetermined target speed, similar to the crawl control described above, or to maintain a target vehicle speed determined from the accelerator opening. In particular, the drive force control unit 15d limits the drive force that is sequentially changed in order to maintain the target vehicle speed to the torque of the motor 9, and maintains the drive force output by the engine 2 at a predetermined torque set by the control, thereby controlling the overall drive torque of the vehicle 1.

[0039] In other words, as shown in Figure 2(c) above, when the engine 2 and motor 9 output drive torque while the differential limiting of the distribution mechanism 3 is in effect, the torque on the front wheel 4 side and the torque on the rear wheel 5 side will be the sum of the torque from the engine 2 and the torque from the motor 9, respectively. Therefore, the torque from the engine 2 is set to a predetermined ratio of the required driving force determined from the accelerator opening or target vehicle speed, and any torque that is insufficient or excessive to reach the target vehicle speed is taken over by the motor 9, and its output torque is controlled by feedback control or the like.

[0040] An example of the control performed by the ECU15 described above will be explained with reference to Figure 4. Figure 4 is a flowchart for explaining the control performed in this embodiment of the invention, and the routine shown here is repeatedly executed when the vehicle 1 is moving. First, the difference in rotational speed between the front and rear wheels is determined (step S1). When the vehicle is driving straight without steering, there is almost no difference in rotational speed between the front wheels 4 and the rear wheels 5, and when the vehicle is turning, a difference in rotational speed corresponding to the turning radius occurs between the front wheels 4 and the rear wheels 5. Therefore, the determination in step S1 can be made by comparing a threshold corresponding to the steering angle or turning radius with the difference in rotational speed between the front and rear wheels.

[0041] If the result of the judgment in step S1 is "no", the routine in Figure 4 is terminated without any particular control. Conversely, if the result of the judgment in step S1 is "yes", it is determined whether the differential frequency (occurrence frequency) of a predetermined differential amount (differential rotation speed) is greater than a predetermined reference value (step S2). Since differential rotation of the front and rear wheels also occurs when vehicle 1 is turning, step S2 takes into account such driving conditions of vehicle 1 when making a judgment, or a reference value is adopted.

[0042] If the result of the judgment in step S2 is "no", the routine in Figure 4 is terminated without any further control. Conversely, if the result of the judgment in step S2 is "yes", a determination of whether the road is rough is made (step S3). As mentioned above, rough roads include roads with many bumps and dips (rough roads), steep downhill slopes, snowy roads, and slippery surfaces. Even if a determination of rough road is made in step S3, the degree of unevenness, the degree of incline, and the duration or distance of the unevenness vary, so it is determined whether it is necessary to switch to a state where the distribution mechanism 3 performs differential limiting (CDL switching) (step S4).

[0043] If the result of the judgment in step S4 is "yes", the lock mechanism 10 is activated and the distribution mechanism 3 is switched to a state of differential limiting (CDL) (step S5). Then, the driving force control when driving with differential limiting of the distribution mechanism 3 (driving force control in CDL mode) is performed (step S6). This control is performed by the driving force control unit 15d described above, which maintains the output of the engine 2 at a constant value and outputs so-called residual driving force from the motor 9 to satisfy the required driving force, and changes the magnitude of this residual driving force from the motor 9 in order to maintain the target vehicle speed. In other words, the vehicle speed is controlled by the motor 9.

[0044] Although the maximum torque that motor 9 can output is smaller than that of engine 2, its control response is superior to that of engine 2. Therefore, by using motor 9 to control the driving force for maintaining vehicle speed, it becomes possible to finely adjust the vehicle speed and control it to the target speed. In other words, the burden on the driver to maintain vehicle speed on rough roads can be reduced. Furthermore, motor 9 is an existing component provided to control the torque distribution ratio by the distribution mechanism 3, and since this is used to control the driving force when driving on rough roads, there is no need to add any new components to perform the control according to this invention, and therefore the overall configuration of the device can be made smaller.

[0045] Next, it is determined whether the driver has selected to release the differential limiting of the distribution mechanism 3 (CDL OFF) (step S7). This operation can be performed, for example, by the manual switch 13 mentioned above. If the result of the determination in step S7 is "no", the process returns to step S6 and continues with the driving force control in differential limiting mode. Conversely, if the result of the determination in step S7 is "yes", the routine shown in Figure 4 is terminated.

[0046] On the other hand, if the result of the judgment in step S4 described above is "no", it is determined whether or not the driver was instructed to switch the distribution mechanism 3 to the differential limiting state (CDL) (step S8). Even on rough roads, there are road conditions in which differential limiting of the distribution mechanism 3 should always be performed, and road conditions in which, considering the driver's driving skills, it is preferable to perform differential limiting of the distribution mechanism 3 and the accompanying driving force control. In the latter case, it is determined to be "no" in step S4 and "yes" in step S8.

[0047] If the result of the judgment in step S8 is "yes," the notification means 14 notifies the driver that the lock mechanism 10 will be activated to limit the differential of the distribution mechanism 3. The driver then operates the manual switch 13 (step S9), and the lock mechanism 10 switches to the engaged state (locked state) (step S5). Subsequently, the process proceeds to steps S6 and S7 in order, and the control described above is performed. In other words, in this embodiment of the invention, in addition to the configuration in which the differential of the distribution mechanism 3 and the associated driving force control are performed automatically when a rough road is determined, the differential of the distribution mechanism 3 and the associated driving force control can also be performed by the driver's manual operation. If the result of the judgment in step S8 is "no," the routine in Figure 4 is terminated without any particular control.

[0048] Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be modified as appropriate. For example, the distribution mechanism may be configured as a torque vectoring mechanism that distributes and transmits torque to the left and right wheels and appropriately controls the distribution ratio. In addition, road information from the navigation system or road information obtained from VICS may be added to determine whether there is a rough road or whether it is necessary to limit the differential of the distribution mechanism. [Explanation of symbols]

[0049] 1 vehicle 2. Power source (engine) 3 Distribution mechanism 4 Front wheels 5 Rear wheels 6. Rear wheel output axle 7 Front wheel output axle 8 Transfer 9. Rotating Machines (Motors) 10 Locking mechanism 11. Accelerator pedal 12 Brake pedal 13 Manual switch 14 Notification means 15. Electronic control units (ECUs, controllers) 15a Rough Road Detection Unit 15b Lock indicator 15c Rock Announcement Department 15d Drive Force Control Unit C Carrier R Ring Gear S Sangiya

Claims

1. A vehicle drive force transmission control device comprising a distribution mechanism that distributes torque output by a drive force source to a first output side and a second output side, and a rotating machine that changes the torque distribution ratio to the first output side and the second output side by the distribution mechanism, The distribution mechanism is composed of a differential mechanism that performs a differential action using a first rotating element that receives torque from the driving force source and outputs torque to the first output side, a second rotating element that outputs torque to the second output side, and a third rotating element to which the rotating machine is connected. A locking mechanism that selectively connects at least two of the first, second, and third rotating elements to limit the differential action of the differential mechanism, The system further comprises a controller that controls the locking mechanism and controls the drive source and the rotating machine when the locking mechanism operates in such a manner as to limit the differential action of the differential mechanism, The aforementioned controller, The vehicle is equipped with a drive force control unit that, while the differential action of the differential mechanism is limited by the locking mechanism, outputs a certain amount of the required driving force from the drive force source, and outputs the remaining driving force other than the driving force output by the drive force source from the rotating machine, and controls the remaining driving force to maintain the vehicle speed at a predetermined target speed. A vehicle power transmission control device characterized by the following features.

2. A vehicle drive force transmission control device according to claim 1, The aforementioned vehicle is equipped with a total of four wheels, including front and rear wheels. The distribution mechanism is a center differential that distributes torque to the front wheels and the rear wheels. The aforementioned controller, A rough road determination unit that determines rough road conditions based on the difference in rotational speed between the front wheel and the rear wheel, The system further includes a lock instruction unit that activates the lock mechanism to limit the differential action of the differential mechanism when the rough road detection unit determines that the road is rough. A vehicle power transmission control device characterized by the following features.

3. A vehicle drive force transmission control device according to claim 1, The aforementioned vehicle is equipped with a total of four wheels, including front and rear wheels. The distribution mechanism is a center differential that distributes torque to the front wheels and the rear wheels. The vehicle further includes a manual locking operation unit that, by manual operation, operates the locking mechanism to limit the differential action of the differential mechanism. The aforementioned controller, A rough road determination unit that determines rough road conditions based on the difference in rotational speed between the front wheel and the rear wheel, The system further includes a lock notification unit that, when the rough road detection unit determines that the road is rough, activates the lock mechanism to restrict the differential action of the differential mechanism and notifies the driver of the vehicle. A vehicle power transmission control device characterized by the following features.

4. A vehicle drive force transmission control device according to any one of claims 1 to 3, The aforementioned target vehicle speed is a predetermined constant vehicle speed. A vehicle power transmission control device characterized by the following features.

5. A vehicle drive force transmission control device according to any one of claims 1 to 3, The aforementioned target vehicle speed is the vehicle speed determined from the amount of acceleration and deceleration performed by the driver of the vehicle. A vehicle power transmission control device characterized by the following features.

6. A vehicle drive force transmission control device according to any one of claims 1 to 3, The aforementioned power source is an internal combustion engine, The aforementioned rotating machine is an electric motor with a power generation function. A vehicle power transmission control device characterized by the following features.

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