JP6056889B2 - Four-wheel drive vehicle control system - Google Patents

Description

  The present invention relates to a control device for a four-wheel drive vehicle and a four-wheel drive vehicle that distribute engine output torque to main drive wheels and auxiliary drive wheels.

  As a four-wheel drive vehicle, it comprises an engine, a transmission, and a front wheel differential, and a power unit that is mounted on the front of the vehicle and drives the left and right front wheels, which are main drive wheels, includes a rear wheel drive transfer, There is a type in which a propeller shaft extending in the front-rear direction of the vehicle body is connected to the transfer, and a rear wheel differential device is provided at the rear end portion so that power can be transmitted to the left and right rear wheels as auxiliary drive wheels.

  A coupling with variable transmission torque, such as an electromagnetic type, may be arranged between the propeller shaft and the rear wheel differential. When the coupling is completely fastened, the front wheel and the rear wheel are connected. If the four-wheel drive state where torque is evenly transmitted and the coupling is completely released, the two-wheel drive state where the driving force is transmitted only to the front wheels is established, and the degree of engagement between the fully engaged and fully released couplings. If it controls to this, torque distribution with respect to a rear-wheel will be adjusted according to the fastening degree of a coupling.

  The transfer uses a pair of bevel gears that mesh with each other in order to transmit power from the differential case of the front wheel differential that extends in the vehicle width direction to the propeller shaft that extends in the vehicle longitudinal direction. For example, a bevel gear provided on the shaft center of the differential case and a bevel gear provided on the shaft center of the propeller shaft that always meshes with the bevel gear are used.

  By the way, the output torque of the engine is accompanied by fluctuating torque generated at a frequency caused by intermittent explosion in each cylinder. On the other hand, a torque transmission means such as a transmission, a front wheel differential, a transfer, a propeller shaft, a coupling, and a rear wheel differential has a resonance frequency against torsional vibration. Therefore, when the frequency of the variable torque matches the resonance frequency of the torque transmission means, the torsional vibration in the torque transmission means may increase.

  At this time, in the two-wheel drive state where the coupling is released and the output torque is transmitted only to the front wheels, the rear wheel torque transmission means from the pair of bevel gears to the rear wheels in the transfer rotates in a power non-transmission state. If the torsional vibration increases in this state, tooth surface separation (a state in which the meshing of the gears is released) tends to occur intermittently between the pair of bevel gears in the transfer of the rear wheel torque transmission means. Sound can be generated and cause in-vehicle noise.

  On the other hand, in the engine operating region where the rear wheel torque transmission means resonates, the degree of coupling is controlled to apply a load to the rear wheel torque transmission means and transmit a torque larger than the fluctuation torque to the rear wheels. By doing so, it is conceivable to prevent the rear wheel torque transmission means from rotating in a power non-transmission state. Thereby, even if the torsional vibration increases in the torque transmission means, it is possible to suppress the tooth surface separation between the pair of bevel gears in the transfer, and to suppress abnormal noise due to gearing.

  For example, Patent Document 1 discloses a four-wheel drive vehicle including an engine and a drive system such as a torque converter, a transmission, a front wheel differential, a transfer, a propeller shaft, a coupling, and a rear wheel differential. When the lock-up clutch of the torque converter is brought into a directly connected state, the backlash at each gear fitting portion of the drive system is reduced by increasing the torque distribution with respect to the rear wheel as the auxiliary drive wheel beyond a predetermined torque, It has been disclosed to eliminate rattling noise (abnormal noise due to gear rattling) when the lockup clutch is engaged.

JP 2009-208633 A

  By the way, because the turning radius of each wheel is different during turning, a difference between the front and rear wheels occurs. In the case of a four-wheel drive vehicle, increasing the torque distribution for the auxiliary drive wheels during turning will absorb the difference between the front and rear wheels. This makes it difficult to perform a tight corner braking phenomenon and deteriorates turning performance.

  The present invention has been made to solve the above-described problems in a four-wheel drive vehicle, and an object thereof is to provide a control device for a four-wheel drive vehicle that can suppress deterioration in turning performance.

  In order to solve the above problems, the present invention is configured as follows.

First, the invention according to claim 1 of the present application is provided with an engine, torque transmission means for transmitting the output torque of the engine to main drive wheels and auxiliary drive wheels, and the torque drive means, and the auxiliary drive wheels. A torque distribution adjusting means for adjusting the torque distributed to the vehicle, and a four-wheel drive vehicle control device comprising: a turning travel determination means for determining whether or not the four-wheel drive vehicle is turning. When the turning determination unit determines that the vehicle is turning, a torque distribution limiting unit that limits torque distribution to the auxiliary drive wheels, and an abnormal sound generation region in which the torque transmission unit is in an abnormal sound generation state. Noise reduction means for increasing the torque distribution to the auxiliary drive wheels by controlling the torque distribution adjustment means during engine operation at the engine so as to suppress the generation of noise. The noise reduction means increases the torque distribution to the auxiliary drive wheel as the torque fluctuation transmitted from the engine to the torque transmission means increases, and the torque distribution restriction means is turning by the turning travel determination means. If it is determined that there is a request to shift to an operating state in which the torque fluctuation increases, an increase in torque distribution to the auxiliary drive wheels by the noise reduction means is limited .

Further, an invention according to claim 2, in the control apparatus for a four wheel drive vehicle according to claim 1, wherein the torque distribution limiting means, if it is determined that the turning traveling by the turning travel determining means When there is a migration request, the migration based on the migration request is restricted.

According to a third aspect of the present invention, in the control device for a four-wheel drive vehicle according to the first or second aspect , the transition request is made when the torque transmission means sets a lock-up clutch at a connection portion with the engine. A request for fastening a lock-up clutch in the case where the torque converter is provided, a request for switching from the spark ignition mode to the compression self-ignition mode when the engine can be switched between the spark ignition mode and the compression self-ignition mode, In the case where a drive motor for torque assist is provided, it is any one of a request to reduce assist torque by the drive motor or a request to stop torque assist.

According to a fourth aspect of the present invention, in the control device for a four-wheel drive vehicle according to any one of the first to third aspects, the turning travel determination means is configured to determine a turning degree of the four-wheel drive vehicle. The torque distribution limiting means increases the degree of limiting the torque distribution to the auxiliary drive wheels as the turning degree of the four-wheel drive vehicle detected by the turning travel determination means increases. Features.

  According to the invention of each claim of the present application, the following effects can be obtained by the above configuration.

First, according to the first aspect of the present invention, the torque distribution to the auxiliary drive wheels is limited during turning, so it is easy to absorb the difference in the rotational speed between the front and rear wheels, and the turning due to tight corner braking phenomenon. Sexual deterioration can be suppressed. Further, during turning, when there is a request to shift to an operating state in which torque fluctuation increases, an increase in torque distribution to the auxiliary drive wheels by the noise reduction means is restricted by the torque distribution restriction means. As a result, it is possible to suppress deterioration in turning performance during turning.

According to the second aspect of the present invention, the torque distribution to the auxiliary drive wheels is increased because the transition based on the transition request to the driving state in which the torque fluctuation increases is restricted during turning. There is no. As a result, an increase in torque fluctuation transmitted to the torque transmission means is suppressed, so that deterioration in turning performance can be suppressed and occurrence of abnormal noise in the torque transmission means can be suppressed.

Further, according to the invention described in claim 3 , the request for shifting to the operating state in which the torque fluctuation increases in the invention described in claim 1 or 2 is specifically specified. That is, when a lockup clutch is provided at the connection between the engine and the torque transmission means, the torque fluctuation transmitted from the engine to the torque transmission means increases as the degree of engagement of the lockup clutch increases. The request is a request for fastening a lockup clutch.

  In addition, when the engine can be switched between the spark ignition mode and the compression self-ignition mode, the combustion in the compression self-ignition mode is higher than that in the spark ignition mode in which combustion gradually grows by the propagation of flame from around the spark plug. Combustion starts from almost everywhere in the chamber and combustion grows rapidly. Therefore, in the compression self-ignition mode, the torque fluctuation accompanying the output torque becomes larger than in the spark ignition mode. Therefore, the transition request in this case is a request for switching from the spark ignition mode to the compression self-ignition mode.

  Further, in the case where the engine includes a drive motor for torque assist, the drive torque generated in the engine is reduced according to the torque assist by the drive motor, and accordingly, the torque fluctuation of the engine is reduced. Therefore, when the torque assist by the drive motor is reduced or stopped, the engine drive torque increases and the fluctuation torque increases accordingly. Therefore, the transition request in this case is the assist by the drive motor. A torque reduction request or a torque assist stop request.

According to the fourth aspect of the present invention, the greater the degree of turning, the greater the degree of restriction on torque distribution to the auxiliary drive wheels. Therefore, depending on the degree of turning, the torque distribution on the auxiliary drive wheels is appropriately restricted. Can be limited by amount. For example, when turning on a curve with a large curvature that tends to deteriorate turning performance, torque distribution to the auxiliary drive wheel is preferably limited, while when turning on a curve with a small curvature, torque distribution to the auxiliary drive wheel Is not overly restricted.

  That is, according to the control device for a four-wheel drive vehicle according to the present invention, torque distribution to the auxiliary drive wheels during turning traveling is limited by the torque distribution limiting means, so that deterioration in turning performance can be suppressed.

1 is a block diagram showing a schematic configuration of a four-wheel drive vehicle according to an embodiment of the present invention. It is a flowchart which shows torque distribution limitation control. It is a time chart which shows the action | operation of the four-wheel drive vehicle in the case of FIG. It is a figure which shows an example of the control map of a lockup clutch. It is a graph which shows the torsional vibration transmission characteristic of a torque transmission means, a torque fluctuation, and the distribution torque with respect to an auxiliary drive wheel. It is a flowchart which shows torque distribution limitation control in case abnormal noise reduction control is implemented. It is a time chart which shows the action | operation of the four-wheel drive vehicle in the case of FIG. It is a time chart which shows the other action | operation of the four-wheel drive vehicle in the case of FIG. It is a time chart which shows the relationship between a turning degree and torque distribution limitation control. It is a figure which shows an example of the control map of the engine which concerns on other embodiment. It is a figure which shows an example of the control map of the engine which concerns on further another embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a schematic configuration diagram of a four-wheel drive vehicle 10 according to an embodiment of the present invention. As shown in FIG. 1, in the first embodiment, the four-wheel drive vehicle 10 includes an engine 14, a transmission 16 that reduces the output torque of the engine 14 at a predetermined reduction ratio, and an output torque that is reduced by the transmission 16. Front wheel differential 20 for transmitting to the left and right front wheels 12F via the axle 18, a transfer 22 for extracting output torque transmitted from the front wheel differential 20 to the rear wheel 12R, and output torque from the transfer 22 to the left and right And a rear wheel differential device 26 that transmits the rear wheel 12R to the rear wheel 12R via an axle 24.

  The engine 14 is a multi-cylinder engine having a plurality of cylinders, and is, for example, an in-line four-cylinder engine in the present embodiment. That is, in the engine 14, explosions occur intermittently in each cylinder, and the output torque T generated in the engine 14 due to the explosion accompanies the fluctuation torque X. Specifically, since the engine 14 is a four-cylinder engine, the fluctuation torque X is generated at a frequency twice as high as the engine speed, and this is transmitted to the transfer 22 via the transmission 16 and the front wheel differential device 20. .

  The transfer 22 and the rear wheel differential device 26 are connected to each other via a propeller shaft 30 and a coupling 28 that extend in the longitudinal direction of the vehicle body. Specifically, the output shaft of the transfer 22 is connected to one end of the propeller shaft 30, the other end of the propeller shaft 30 is connected to the input shaft of the coupling 28, and the output shaft of the coupling 28 is the rear wheel differential. It is connected to the input shaft of the device 26.

  The transfer 22 is a pair of bevel gears (not shown) that mesh with each other in order to transmit power from the front wheel differential device 20 whose shaft center extends in the vehicle width direction to the propeller shaft 30 whose shaft center extends in the vehicle body longitudinal direction. Specifically, a bevel gear provided on the axis of the front wheel differential device 20 and a bevel gear provided on the axis of the propeller shaft 30 are used.

An electromagnetic coupling is used for the coupling 28, and the degree of fastening between the propeller shaft 30 and the rear wheel differential device 26 can be varied, and according to the degree of fastening of the coupling 28. , torque distribution T _R to be transmitted to the rear wheels 12R is adapted to be adjusted.

Specifically, if completely engaged coupling 28, the output torque T of the engine 14, equivalent to the distribution torque T _F, which is transmitted to the front wheels 12F, in the distribution torque T _R to be transmitted to the rear wheels 12R It becomes the four-wheel drive state distributed to. On the other hand, if the coupling 28 is completely released, the output torque T is in a two-wheel drive state in which the output torque T is transmitted only to the front wheels 12F. Further, if the coupling 28 to the fastening degree between the fully engaged and fully disengaged, distribution torque T _R to be transmitted to the rear wheels 12R in accordance with the engagement of the coupling 28 is adjusted. That is, by controlling the engagement of the coupling 28, the distribution torque _{T R} for the rear wheels 12R, can be adjusted between 0 and 50% of the output torque T of the engine 14.

In the present embodiment, the front wheel 12F is the main drive wheel, the rear wheel 12R is the auxiliary drive wheel, the transmission 16, the front wheel differential 20, the axle 18, the transfer 22, the propeller shaft 30, the coupling 28, and the rear wheel. The differential gear 26 and the axle 24 constitute a torque transmission means 50 for transmitting the output torque T of the engine 14 to the front wheels 12F and the rear wheels 12R, and the distribution torque T distributed to the rear wheels 12R by the coupling 28. Torque distribution adjusting means for adjusting _R is configured.

  Further, the four-wheel drive vehicle 10 includes an accelerator opening sensor 36 so as to detect an accelerator pedal depression amount (accelerator opening) by a driver, an engine rotation sensor 38 that detects the rotational speed of the engine 14, and left and right Left front wheel speed sensor 40L and right front wheel speed sensor 40R provided on each front wheel 12F, left rear wheel speed sensor 41L and right rear wheel speed sensor 41R respectively provided on left and right rear wheels 12R, engine 14 and cup And a control device 34 for controlling the operation of the ring 28 and the like.

  Various information such as a signal from the accelerator opening sensor 36, a signal from the engine rotation sensor 38, and each wheel speed sensor 40, 41 is input to the control device 34, and the control device 34 determines the engine based on the various information. 14 and the coupling 28 are controlled. The control device 34 is configured with a microcomputer as a main part.

  Based on the signal from the accelerator opening sensor 36, the control device 34 detects the driver's acceleration request, sets the target torque (engine load), and controls the engine 14 to output the target torque. .

Further, the control unit 34, an output torque T from the engine 14, so as to distribute to the distribution torque T _R for distribution torque T _F and the rear wheel 12R to the front wheels 12F, to control the engagement of the coupling 28. For example, when accelerating or when a slip is detected on the front wheel 12F based on signals from the wheel speed sensors 40, 41, control is made to a four-wheel drive state in which output torque T is distributed to the front wheels 12F and the rear wheels 12R. In steady running and / or coast running, control is performed to a two-wheel drive state in which the output torque T is transmitted only to the front wheels 12F.

  Note that the torque distribution for the rear wheel 12R may be controlled by an abnormal noise reduction control described later, and the torque distribution for the rear wheel 12R may be controlled by another factor.

Further, the control device 34 performs torque distribution restriction control for restricting torque distribution to the rear wheels 12R as auxiliary drive wheels when the four-wheel drive vehicle 10 is turning. Specifically, the control device 34 detects the turning degree of the four-wheel drive vehicle 10 based on signals from the wheel speed sensors 40 and 41. More specifically, the control device 34 calculates the turning radius R based on the signals from the wheel speed sensors 40 and 41, and calculates the curvature R- ¹ that is the reciprocal of the turning radius R as the turning degree. To do.

As the controller 34, when the curvature R ^-1 exceeds a predetermined threshold value S0, determines that the four-wheel-drive vehicle 10 is in turning, to limit the distribution torque T _R for the rear wheels 12R, The degree of fastening of the coupling 28 is controlled. Therefore, the control device 34 can detect the turning degree, and functions as a turning determination unit that can determine whether or not the four-wheel drive vehicle 10 is turning based on the turning degree. The threshold value S0 is, for example, a threshold value for determining whether or not the four-wheel drive vehicle 10 is turning, and is turning when the calculated curvature is small enough to be considered not turning. Is set to a value that can prevent erroneous determination.

Further, the control device 34, as the turning degree increases, to increase the degree of limitation distribution torque T _R for the rear wheel 12R, and controls the engagement of the coupling 28. Incidentally, limitations and can include instances when the four-wheel drive vehicle 10 has means to reduce than distribution torque T _R to be distributed to the rear wheels 12R and if not turning, the distribution torque T _R to zero It is. Therefore, the control device 34 functions as torque distribution limiting means.

  Next, the torque distribution restriction control performed in the control device 34 will be described with reference to the flowchart of FIG. 2 and the time chart of FIG. FIG. 2 is a flowchart showing the flow of torque distribution restriction control, and FIG. 3 is a time chart showing the operation of the four-wheel drive vehicle 10 in this case.

  As shown in FIG. 2, the control device 34 reads various information such as a signal from the accelerator opening sensor 36, a signal from the engine rotation sensor 38, and each wheel speed sensor 41, 42 (step S101).

Next, the control device 34 calculates the turning degree (curvature R ⁻¹ ) of the four-wheel drive vehicle 10 based on the signals from the wheel speed sensors 40 and 41 (step S102).

Next, based on the turning degree calculated in step S102, the control device 34 determines whether or not the four-wheel drive vehicle 10 is turning, that is, whether the curvature R- ¹ is greater than a predetermined threshold value S0. It is determined whether or not (step S103).

  If it is determined in step S103 that the four-wheel drive vehicle 10 is turning, the control device 34 performs torque distribution restriction control for restricting torque distribution to the rear wheels 12R (step S104).

At this time, as shown in FIG. 3, it is assumed that the four-wheel drive vehicle 10 has started turning at time t3, and the turning degree (curvature R ⁻¹ ) has exceeded the threshold value S0 between times t4 and t6. . At this time, even when a request for increasing torque distribution to the rear wheel 12R is made at time t5, for example, with an increase in the output torque T of the engine 14, the torque distribution to the rear wheel 12R is not increased. Then, turning degree (curvature ^{R -1)} is at time t6 after the below the threshold S0, distribution torque _{T R} for the rear wheel 12R is increased. That is, when the four-wheel drive vehicle 10 is turning, torque distribution to the rear wheels 12R is limited.

  On the other hand, as shown in FIG. 2, when it is determined in step S103 that the four-wheel drive vehicle 10 is not turning, the control device 34 does not limit the torque distribution to the rear wheels 12R. That is, torque distribution restriction control is not performed.

At this time, as shown in FIG. 3, when a request for increasing torque distribution to the rear wheel 12R occurs at time t1, the turning degree does not exceed the threshold value S0, and the four-wheel drive vehicle 10 is not turning. , torque distribution limit control is not performed, distribution torque T _R for the rear wheel 12R is increased.

  Thus, according to the present embodiment, during turning, torque distribution to the rear wheel 12R is limited. Therefore, it is easy to absorb the rotational speed difference between the front wheel 12F and the rear wheel 12R, and the tight corner brake It is possible to suppress the deterioration of turning performance due to the swinging phenomenon.

[Second Embodiment]
Next, a second embodiment will be described. In the second embodiment, the transmission 16 is an automatic transmission. As shown by a one-dot chain line in FIG. 1, the torque transmission means 50 includes a torque converter 15 having a lock-up clutch 151 at a connection portion between the engine 14 and the transmission 16, and the output torque T of the engine 14 is torque. It is transmitted to the transmission 16 through the converter 15.

  The lockup clutch 151 can change the degree of engagement between an input shaft (not shown) to which the output torque T of the engine 14 is input and an output shaft (not shown) output to the transmission 16. The torque transmitted from the engine 14 to the transmission 16 is adjusted according to the degree of engagement. That is, the torque transmission is variable from the torque transmission in the directly connected state when the lockup clutch 151 is completely engaged to the torque transmission at the fluid coupling by the torque converter 15 when the lockup clutch 151 is in the released state. it can.

  Note that, by shifting the degree of engagement of the lockup clutch 151 in the engagement direction, the damping effect of the variable torque X due to torque transmission at the fluid coupling of the torque converter 15 is reduced, and the variable torque X transmitted from the engine 14 to the transmission 16 is reduced. Will increase.

  FIG. 4 shows an example of a control map of the lockup clutch 151, and the degree of engagement of the lockup clutch 151 is controlled based on the control map. For example, the degree of engagement of the lock-up clutch 151 is controlled in the engagement direction in the low rotation and high load region, and is controlled in the release direction in the high rotation and low load region.

Moreover, in 2nd Embodiment, the control apparatus 34 performs noise reduction control which suppresses this noise at the time of the action | operation of the engine 14 into which the torque transmission means 50 will be in the noise generation state. Specifically, the torque transmission means 50 has a resonance frequency with respect to torsional vibration in the axial rotation direction. As shown in FIG. 5, in this embodiment, the torque transmission means 50 has resonance points P1 and P2 in the emergency area of the engine 14 lower than the idle speed N _{IDLE of the} engine 14, and the idle speed N There is a resonance point P3 in the normal range of the engine 14 _{equal to} or higher than _IDLE .

In the vicinity of the resonance point P3, fluctuation torque X with the output torque T of the engine 14 is to be increased by the resonance, this time, when the torque distribution T _R for the rear wheel 12R is smaller than the variation torque X is In the transfer 22, tooth surface separation occurs between the bevel gears, and abnormal noise (tooth noise) is generated. A region where the abnormal noise is generated from the torque transmitting means 50 will be referred to as an abnormal noise generation region A and will be described below.

The control device 34 stores an abnormal sound generation area A where the torque transmission means 50 is in an abnormal sound generation state. The abnormal noise generation area A is an operation area in which the frequency of the fluctuation torque X generated due to intermittent explosion in each cylinder coincides with the resonance frequency of the torque transmission means 50. In the abnormal noise generation region, the fluctuation torque X from the engine 14 is increased by resonance, and accordingly, the torsional vibration in the torque transmission means 50 is increased. At this time, when the torque distribution T _R for the rear wheel 12R is smaller than the variation torque X is the transfer 22, abnormal noise (rattling sound) generated tooth surface separation occurs between a pair of bevel gears There is a case.

Therefore, in order to suppress the generation of abnormal noise in the torque transmission means 50, the control device 34 performs abnormal noise reduction control when the engine 14 is operating in the abnormal noise generation region. Specifically, abnormal noise reduction control, the abnormal noise generation region, distribution torque T _R for the rear wheel 12R is fastened degree of coupling 28 to be larger than at least the variable torque X is controlled. That is, by increasing from fluctuating torque X a distribution torque T _R for the rear wheel 12R, the tooth surface separation between the pair of bevel gears in the transfer 22 is prevented from occurring due to the increased torsional vibration, Abnormal noise (gap sound) can be suppressed.

Further, the control device 34 stores a fluctuation torque map (not shown) in which the fluctuation torque X in the torque transmission means 50 is associated with each engine operating point (engine speed and load). In this fluctuation torque map, a fluctuation torque X including an increase in vibration due to resonance in the torque transmission means 50 is set in advance. In the noise reduction control, the control device 34 transfers the torque transmission means 50 from the fluctuation torque map to the torque transmission means 50. It reads the transmitted torque fluctuation X, as distributed to the rear wheels 12R large distribution torque T _R than said fluctuation torque X, controls the engagement of the coupling 28.

  That is, the control device 34 determines whether or not the engine 14 is operating in the abnormal noise generation area A based on the input signal from the engine rotation sensor 38, and the engine 14 is operating in the abnormal noise generation area A. If it is determined, abnormal noise reduction control is performed. Therefore, the control device 34 also functions as noise reduction means.

  Further, when the control device 34 determines that the four-wheel drive vehicle 10 is turning, there is a request for transition to an operation state in which torque fluctuation increases, that is, for example, the degree of engagement of the lock-up clutch 151. When there is a fastening request in the fastening direction, torque distribution restriction control is performed. In the torque distribution restriction control in this case, further increase in the torque distribution to the rear wheel 12R by the noise reduction control is restricted, and the transition based on the engagement request, that is, the engagement degree of the lockup clutch 151 in the engagement direction. Transitions based on fastening requests are limited. In the present embodiment, both the abnormal noise reduction control and the shift based on the shift request are limited, but only one of them may be limited.

  Next, the torque distribution restriction control performed in the control device 34 will be described with reference to the flowchart of FIG. 6 and the time charts of FIGS. 7a and 7b. FIG. 6 is a flowchart showing the flow of torque distribution restriction control when the noise reduction control is performed, and FIGS. 7a and 7b are time charts showing the operation of the four-wheel drive vehicle 10 in this case.

  As shown in FIG. 6, the control device 34 reads various information such as a signal from the accelerator opening sensor 36, a signal from the engine rotation sensor 38 and the wheel speed sensors 41 and 42 (step S <b> 201).

  Next, the control device 34 determines whether or not the engine 14 is operating in the abnormal sound generation area A (see FIG. 5) based on the signal from the engine rotation sensor 38 (step S202).

  If it is determined in step S202 that the engine 14 is operating in the abnormal noise generation area A, the control device 34 performs abnormal noise reduction control (step S203). On the other hand, if it is not determined in step S202 that the engine 14 is operating in the abnormal sound generation area A, the control device 34 performs torque distribution based on the flowchart (see FIG. 2) described in the first embodiment. The restriction control is performed or not performed (step S100).

When the abnormal noise reduction control is performed in step S203, the control device 34 calculates the turning degree (curvature R ⁻¹ ) of the four-wheel drive vehicle 10 based on the signals from the wheel speed sensors 40 and 41. (Step S204).

Next, based on the turning degree calculated in step S204, the control device 34 determines whether or not the four-wheel drive vehicle 10 is turning, that is, whether the curvature R- ¹ is greater than a predetermined threshold value S0. It is determined whether or not (step S205).

When it determines with curvature R- ¹ being larger than predetermined threshold value S0 in step S205, the control apparatus 34 implements torque distribution restriction | limiting control (step S206). On the other hand, when it is not determined in step S205 that the curvature R-1 is larger than the predetermined threshold value S0, the control device 34 does not perform the torque distribution restriction control (step S207).

  Next, when the torque distribution restriction control is performed in step S206, the control device 34 subsequently determines whether or not there is a request for shifting to an operating state in which the variable torque X increases (step S208). That is, in this embodiment, for example, it is determined whether or not there is an engagement request in the engagement direction of the engagement degree of the lockup clutch 151.

  When it is determined in step S208 that there is a request for shifting to an operating state in which the variable torque X increases, the control device 34 restricts the noise reduction control and requests to shift to an operating state in which the variable torque X increases. The transition based on is restricted (step S209). That is, an increase in the torque distribution to the rear wheel 12R by the abnormal noise reduction control is restricted, and a transition based on the fastening request in the fastening direction of the fastening degree of the lockup clutch 151 is restricted.

At this time, as shown in FIG. 7a, it is assumed that the four-wheel drive vehicle 10 starts turning at time t1, and the turning degree (curvature R ⁻¹ ) exceeds the threshold value S0 between times t2 and t5. At this time, the engine speed increases at time t3, and accordingly, an engagement request in the engagement direction of the lockup clutch 151 is generated based on the control map shown in FIG. Further, at time t4, the engine 14 starts operating in the abnormal sound generation region.

At this time, since the four-wheel drive vehicle 10 is turning, until the time t5, the noise reduction control is restricted, and the shift of the degree of engagement of the lockup clutch 151 in the engagement direction is limited. In other words, never the distribution torque T _R for the rear wheel 12R is increased during cornering. After time t5 when the turning degree (curvature R ⁻¹ ) is lower than the threshold value S0, a transition is made based on the noise reduction control and the engagement request of the engagement degree of the lockup clutch 151 in the engagement direction.

On the other hand, as shown in FIG. 7b, when the engine 14 starts accelerating at time t11 and the engine 14 starts operating in the abnormal noise generation area A at time t12, the abnormal noise reduction control is performed and with distribution torque T _R for wheel 12R is increased, engagement of the lock-up clutch 151 is controlled to the fastening direction based on the control map. In this case, the transition to the fastening direction of the fastening degree of noise reduction control and the lock-up clutch 151, even distribution torque T _R for the rear wheel 12R is increased, the turning property since four-wheel drive vehicle 10 is not in the turning Deterioration is not a problem. 7a and 7b, the lockup clutch engagement request indicates that the larger the vertical axis is, the higher the engagement request for the lockup clutch 151 is, and the smaller the vertical axis is, the lower the engagement request for the lockup clutch 151 is. .

  Thus, according to the present embodiment, during a turn, when there is a request to shift to an operating state where torque fluctuation increases, an increase in torque distribution to the rear wheel 12R by the noise reduction control is a torque. Limited by allocation limitation control. As a result, it is possible to suppress deterioration in turning performance during turning.

Further, during turning, the transition based on the transition request to the operating state in which the variable torque X increases is restricted, that is, the transition of the degree of engagement of the lockup clutch 151 in the fastening direction is restricted. increase in distribution torque T _R for with rear wheel 12R to be limited. As a result, an increase in the fluctuation torque X transmitted to the torque transmitting means 50 is suppressed, so that deterioration in turning performance can be suppressed and occurrence of abnormal noise in the torque transmitting means 50 can be suppressed.

FIG. 8 shows the degree of torque distribution restriction for the rear wheel 12R by the torque distribution restriction control for the degree of turning. In a state where the engine 14 is operating in the abnormal sound generation area A, the vehicle turns with the first turning degree S1 from time t21 to t22, and the second with a curvature R ⁻¹ larger than the first turning degree S1 from time t23 to t24. It is assumed that the vehicle is turning with the turning degree S2.

When the vehicle is turning in the first turning degree S1, torque distribution limiting means, the distribution torque T _R to the rear wheels 12R and limited by the first limiting amount D1, when the vehicle is turning in the second turning degree, the rear wheels the distribution torque _{T R} to 12R than the first limit amount D1 for limiting a large second limit amount D2. That is, the greater the degree of turning, the greater the amount of restriction by torque distribution restriction control. Further, as shown by a dotted line in the figure, during cornering, may the distribution torque T _R for the rear wheel 12R to zero.

Thus, as the turning degree is large, the degree of limitation distribution torque T _R for the rear wheel 12R is increased, in accordance with the turning degree, can limit the distribution torque T _R for the rear wheel 12R with the appropriate restriction amount. For example, when a turning resistance to turning the large curve of curvature which tends to deteriorate while the distribution torque T _R for the rear wheel 12R is preferably limited, for the rear wheels 12R in the case of turning a small curve旋曲rate never distribution torque T _R is unduly limited.

  In the above-described embodiment, the request for shifting to the operating state in which the variable torque X increases has been described by taking, as an example, the request for shifting the engagement degree of the lockup clutch 151 in the engagement direction or the request for increasing the output torque T of the engine 14. However, the present invention is not limited to this. For example, in an engine configured to be switchable between a spark ignition mode and a compression self-ignition mode, an example of the control map shown in FIG. Good.

  That is, compared to the spark ignition mode in which combustion gradually grows by the propagation of flame from around the spark plug, in the compression ignition mode, combustion starts almost simultaneously from almost everywhere in the combustion chamber, and the combustion grows rapidly. . For this reason, in the compression ignition mode, the torque fluctuation accompanying the output torque is larger than in the spark ignition mode. Therefore, the transition request is a request for switching from the spark ignition mode to the compression self-ignition mode.

  The compression self-ignition mode may be further divided into a non-premixed compression self-ignition mode (CI) and a premixed compression self-ignition mode (HCCI). In this case, the fluctuation torque X is larger in the order of HCCI, CI, and spark ignition mode (SI). Therefore, the transition request to the operation state in which the fluctuation torque X increases is a switching request from SI to CI or HCCI, or This is a switching request from CI to HCCI.

  In addition, as an example of a control map shown in FIG. 10 as a request to shift to an operating state in which the fluctuation torque X increases, a torque assist by the drive motor is requested to be reduced or torque assist is stopped in an engine having a torque assist drive motor. It may be a request. That is, since the drive torque generated in the engine is reduced according to the torque assist by the drive motor, the torque fluctuation of the engine is reduced accordingly. Therefore, the transition request is a request for reducing torque assist by the drive motor or a request for stopping torque assist.

  In the above embodiment, a four-wheel drive vehicle is described in which the front wheel 12F is the main drive wheel and the rear wheel 12R is the auxiliary drive wheel. However, the rear wheel 12R is the main drive wheel and the front wheel 12F is the auxiliary drive wheel. The same can be applied to the four-wheel drive vehicle.

  In the above embodiment, the turning degree of the four-wheel drive vehicle is calculated based on the signals detected by the wheel speed sensors 40 and 41. However, instead of or in addition to this, a steering angle sensor (not shown). Thus, the steering angle of the steering wheel may be detected to determine whether or not the four-wheel drive vehicle is turning.

  By determining whether the four-wheel drive vehicle is turning or not based on the steering angle detected by the steering angle sensor, before the four-wheel drive vehicle actually starts turning, It is easy to detect the driver's intention to turn, and as a result, the control response can be improved. Also. You may make it detect whether the four-wheel drive vehicle is turning while using G sensor.

  Various modifications and changes may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

  As described above, according to the control device for a four-wheel drive vehicle according to the present invention, since the torque distribution with respect to the auxiliary drive wheel during turning can be restricted by the torque distribution restriction means, deterioration of turning performance can be suppressed. There is a possibility of being suitably used in the field of various manufacturing technologies.

DESCRIPTION OF SYMBOLS 10 Four-wheel drive vehicle 12F Front wheel 12R Rear wheel 40L Left front wheel speed sensor 40R Right front wheel speed sensor 41L Left rear wheel speed sensor 41R Right rear wheel speed sensor 14 Engine 15 Torque converter 151 Lockup clutch 16 Transmission 20 Front wheel differential 22 transfer 26 rear wheel differential device 28 coupling 30 propeller shaft 34 the control device 36 accelerator position sensor 38 engine speed sensor 50 torque transmitting means T output torque T _R distribution torque X fluctuation torque

Claims (4)

An engine, torque transmission means for transmitting the output torque of the engine to the main drive wheel and the auxiliary drive wheel, and torque distribution adjustment means provided in the torque transmission means for adjusting the torque distributed to the auxiliary drive wheel; A four-wheel drive vehicle control device comprising:
Turning determination unit for determining whether or not the four-wheel drive vehicle is turning;
Torque distribution limiting means for limiting torque distribution to the auxiliary drive wheels when the turning determination means determines that the vehicle is turning .
When the engine is operating in an abnormal noise generation region where the torque transmission means is in an abnormal noise generation state, the torque distribution adjustment for the auxiliary drive wheels is increased so as to suppress the generation of abnormal noise by controlling the torque distribution adjustment means. Abnormal noise reduction means
With
The abnormal noise reduction means increases the torque distribution to the auxiliary drive wheels as the torque fluctuation transmitted from the engine to the torque transmission means increases.
When the torque distribution limiting means has made a request to shift to an operating state in which the torque fluctuation increases when it is determined by the turning determination means that the vehicle is turning, the auxiliary drive by the noise reduction means is performed. A control device for a four-wheel drive vehicle, characterized by limiting an increase in torque distribution to wheels. The torque distribution restriction means restricts the transition based on the transition request when the transition request is made when it is determined by the turning travel determination means that the vehicle is turning.
The control device for a four-wheel drive vehicle according to claim 1 . The migration request is
An engagement request for a lockup clutch when the torque transmission means includes a torque converter having a lockup clutch at a connection portion with the engine;
A request to switch from the spark ignition mode to the compression self-ignition mode when the engine is switchable between the spark ignition mode and the compression self-ignition mode;
A request to reduce assist torque by the drive motor or a request to stop torque assist when the engine includes a drive motor for torque assist;
Any one of
The control device for a four-wheel drive vehicle according to claim 1 or 2 . The turning travel determination means can detect the turning degree of the four-wheel drive vehicle, and the torque distribution restriction means increases the turning degree of the four-wheel drive vehicle detected by the turning travel determination means. Increase the degree of limiting torque distribution for the auxiliary drive wheels,
The control device for a four-wheel drive vehicle according to any one of claims 1 to 3 .

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