JP2017154682A - Control apparatus of four-wheel drive vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control apparatus of a four-wheel drive vehicle comprising a connection/disconnection mechanism and first and second clutches, in which stability in vehicle body is improved while ensuring accuracy in wheel speed.SOLUTION: There is provided an ECU 19 of a vehicle 1 calculating vehicle speed on the basis of rotation speed of rear wheels 4, 5, which comprises: front side and rear side connection/disconnection mechanisms 11, 15 connecting/disconnecting driving power transmission pathway for transmitting a part of driving power to be transmitted to front wheels 2, 3 to the rear wheels 4, 5; and first and second couplings 17, 18 which are respectively arranged on each of the driving power transmission pathway between the rear side connection/disconnection mechanism 15 and the right and left rear wheels 4, 5 and is capable of transmitting driving power while tolerating difference in rotation between the right and left rear wheels 4, 5. In a case where either of right and left rear wheels 4, 5 is locked, the first and second couplings 17, 18 are put into released state, whereas in a case where only front wheels 2, 3 are locked, the front side and rear side connection/disconnection mechanisms 11, 15 are put into released state and the first and second couplings 17, 18 are put into engaged state.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for a four-wheel drive vehicle.

  As a vehicle that can be switched between a two-wheel drive state and a four-wheel drive state, a so-called standby-type four-wheel drive vehicle that normally travels in a two-wheel drive state and automatically transmits drive torque to the driven wheels when the drive wheels idle. Is conventionally known.

  As such a standby type four-wheel drive vehicle, when switching to the four-wheel drive state, by engaging an electronically controlled coupling (for example, a multi-plate clutch) provided between the propeller shaft and the rear differential, An electronically controlled standby type that transmits drive torque to a driven wheel is well known.

  Incidentally, in a four-wheel drive vehicle based on an FF (front engine front drive) vehicle, the vehicle body speed is usually estimated based on the wheel speeds of the left and right rear wheels (driven wheels). For this reason, in an electronically controlled standby four-wheel drive vehicle, when an ABS (Antilock Brake System) is activated or when a braking slip occurs where the ABS is activated, the electronically controlled coupling is released to be in a two-wheel drive state. In many cases, a drop in the wheel speed generated in the brake slip wheel does not affect other wheels.

  For example, assuming that one of the front wheels (drive wheels) is locked, the rotation speed of the transfer ring gear, which is the average rotation speed of the left and right front wheels, is the rotation of the rear diff ring gear, which is the average rotation speed of the left and right rear wheels. Since the speed is smaller than the speed, differential rotation occurs in the coupling in the four-wheel drive state. Thus, when differential rotation occurs in the coupling, brake torque is applied to the rear differential ring gear and drive torque is applied to the transfer gear so that the rotation of the transfer ring gear and the rotation of the rear differential ring gear are synchronized. Thus, the rotational speed of the rear wheel detected by the sensor or the like is lower than the current rotational speed of the rear wheel that is actually desired to be detected. Therefore, in an electronically controlled standby type four-wheel drive vehicle, when the ABS is operated, the electronic control coupling is released and the two-wheel drive state is established. The sex is secured.

  Further, as a standby type four-wheel drive vehicle, a connection / disconnection mechanism for connecting / disconnecting a power transmission path for transmitting a part of the driving force transmitted to the drive wheel to the driven wheel, and between the connection / disconnection mechanism and the left and right driven wheels. There are also provided with first and second clutches respectively provided in the respective power transmission paths (see, for example, FIG. 10 of Patent Document 1). In such a four-wheel drive vehicle, in a two-wheel drive state, the connecting / disconnecting mechanism and the first and second clutches are released to stop the rotation of the propeller shaft and the like, thereby reducing friction loss and improving fuel efficiency. .

Japanese Patent No. 5254470

  By the way, in the electronically controlled standby type four-wheel drive vehicle, if the idea of setting the two-wheel drive state when the ABS is operated or the like is also applied to the four-wheel drive vehicle including the connection / disconnection mechanism and the first and second clutches, The accuracy of the wheel speed can be ensured by releasing the connecting / disconnecting mechanism and the first and second clutches in the two-wheel drive state when the ABS is operated.

  However, it is not preferable to allow the differential of the left and right driven wheels to be unlimited by releasing the first and second clutches when the vehicle body falls into an unstable state, such as during deceleration.

  The present invention has been made in view of such points, and an object of the present invention is to ensure the accuracy of wheel speed in a control device for a four-wheel drive vehicle including a connection / disconnection mechanism and first and second clutches. However, it is to improve the stability of the vehicle body.

  In order to achieve the above object, in the control device for a four-wheel drive vehicle according to the present invention, when it is possible to ensure the accuracy of the wheel speed, only the connecting / disconnecting mechanism is released and the first and second clutches are disengaged. The fastening state is set.

  Specifically, the present invention provides a connection / disconnection mechanism for connecting / disconnecting a power transmission path for transmitting a part of the driving force transmitted to the main drive wheel to the sub drive wheel, the connection / disconnection mechanism, and the left and right sub drive wheels, And a first clutch and a second clutch that are capable of transmitting a driving force while allowing a difference in rotation between the left and right auxiliary drive wheels, and based on the rotation speed of the auxiliary drive wheels. It is intended for a control device for a four-wheel drive vehicle that calculates a vehicle speed.

  The control device releases the first and second clutches when either one of the left and right auxiliary driving wheels is locked, while when only the main driving wheel is locked, The connecting / disconnecting mechanism is set to a released state and the first and second clutches are set to an engaged state.

  According to this configuration, when either one of the left and right auxiliary driving wheels is locked, the first and second clutches are disengaged, so that the wheel speed of the auxiliary driving wheel lock wheel becomes the auxiliary driving wheel. The influence on the wheel speed of the non-locking wheel can be suppressed. As a result, the vehicle body speed can be accurately calculated based on the rotation speed of the auxiliary drive wheels.

  On the other hand, when only the main drive wheel is locked, the wheel speed of the lock wheel of the main drive wheel is changed to that of the sub drive wheel by setting the connecting / disconnecting mechanism to the released state and the first and second clutches to the engaged state. It is possible to accurately calculate the vehicle body speed based on the rotation speed of the auxiliary driving wheel while suppressing the influence on the wheel speed. In addition, by adjusting the transmission torque of the first and second clutches in the engaged state and limiting the rotational speed difference between the left and right auxiliary drive wheels, the effect of LSD (limited slip differential) is imparted. As a result, the vehicle body can be stabilized.

  As described above, the control device for a four-wheel drive vehicle according to the present invention can improve the stability of the vehicle body while ensuring the accuracy of the wheel speed.

1 is a diagram illustrating a schematic configuration of a vehicle according to an embodiment of the present invention. It is a figure which shows the flowchart of the process which ECU performs. It is a figure which shows the flowchart of the process which ECU performs. It is a figure which shows the flowchart of the process which ECU performs. It is a figure which shows schematic structure of the conventional electronically controlled standby type four-wheel drive vehicle.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a schematic configuration of a vehicle 1 according to the present embodiment. The vehicle 1 is an FF vehicle-based four-wheel drive vehicle. As shown in FIG. 1, the engine 6, left and right front wheels 2 and 3, left and right rear wheels 4 and 5, an automatic transmission 7, Front differential 8, transfer 9, propeller shaft 13, drive pinion 14, rear side connection / disconnection mechanism 15, intermediate shaft 16, first coupling 17, second coupling 18, ECU (Electronic Control) Unit) 19.

  The left and right front wheels 2 and 3 constitute main drive wheels that serve as drive wheels in both a two-wheel drive state (hereinafter also referred to as a 2WD state) and a four-wheel drive state (hereinafter also referred to as a 4WD state). . The left and right rear wheels 4 and 5 constitute driven wheels in the 2WD state, and constitute auxiliary driving wheels that serve as driving wheels in the 4WD state.

  The front differential 8 has a differential case 8a and a differential gear portion 8b accommodated in the differential case 8a, and is configured to transmit power while appropriately applying differential rotation to the left and right front wheels 2 and 3. ing. The differential case 8 a is provided with a differential ring gear 8 c that meshes with the output gear 7 a of the automatic transmission 7, and a drive gear 8 d that meshes with the driven gear 10 a provided on the input shaft 10 of the transfer 9. As a result, the power output from the engine 6 is input to the transfer 9 via the automatic transmission 7 and the front differential 8.

  The transfer 9 includes an input shaft 10, a front side connection / disconnection mechanism 11, and a driven pinion 12 connected to a drive pinion 14 via a propeller shaft 13.

  The input shaft 10 is formed in a substantially cylindrical shape, and the front wheel axle 20 passes through the inside thereof. The driven gear 10 a described above is provided at the left end in the axial direction of the input shaft 10, while the drive gear 10 b is provided at the right end in the axial direction of the input shaft 10. The input shaft 10 rotates integrally with the differential case 8 a when the driven gear 10 a meshes with the drive gear 8 d of the front differential 8.

  The front side connecting / disconnecting mechanism 11 includes a rotating member 21, a sleeve 24, and a synchronizer ring 25. The rotating member 21 is formed in a substantially cylindrical shape, and the front wheel axle 20 and the input shaft 10 pass through the inside thereof. A transfer ring gear 23 that meshes with the driven pinion 12 is provided at the left end portion in the axial direction of the rotating member 21, while a driven gear 22 having substantially the same diameter as the drive gear 10 b is provided at the right end portion in the axial direction of the rotating member 21. Is provided. The sleeve 24 is formed in a substantially cylindrical shape, and inner peripheral teeth that can mesh with the drive gear 10 b and the driven gear 22 are formed on the inner peripheral side thereof. The sleeve 24 is configured to move in the axial direction by an actuator 24 a controlled by the ECU 19, and to take a position that engages only with the drive gear 10 b and a position that engages with the drive gear 10 b and the driven gear 22. The synchronizer ring 25 is a synchronization mechanism that synchronizes the inner peripheral teeth of the sleeve 24 and the driven gear 22 with each other.

  FIG. 1 shows a state in which the front side connection / disconnection mechanism 11 is released. In this state, the sleeve 24 meshes only with the drive gear 10 b and the connection between the input shaft 10 and the rotating member 21 is cut off, so that no power is transmitted from the transfer 9 to the propeller shaft 13. On the other hand, when the sleeve 24 is moved and the sleeve 24 meshes with the drive gear 10b and the driven gear 22, the front side connecting / disconnecting mechanism 11 is connected, and the input shaft 10 and the rotating member 21 are connected. Power is transmitted from 9 to the drive pinion 14 via the propeller shaft 13.

  The rear side connection / disconnection mechanism 15 is provided between the intermediate shaft 16 provided between the left and right rear wheel axles 31, 32 and the drive pinion 14, and selectively connects / disconnects the power transmission path between them. And includes a rotating member 26, a sleeve 29, and a synchronizer ring 30. The rotating member 26 is formed in a substantially cylindrical shape, and the intermediate shaft 16 passes through the inside thereof. A ring gear 27 that meshes with the drive pinion 14 is provided at the right end in the axial direction of the rotating member 26, while the input gear 16 a provided in the intermediate shaft 16 is substantially provided at the left end in the axial direction of the rotating member 26. A drive gear 28 having the same diameter is provided. The sleeve 29 is formed in a substantially cylindrical shape, and inner peripheral teeth that can mesh with the input gear 16 a and the drive gear 28 are formed on the inner peripheral side thereof. The sleeve 29 is configured to move in the axial direction by an actuator 29a controlled by the ECU 19 to take a position where only the input gear 16a is engaged, and a position where the input gear 16a and the drive gear 28 are engaged. The synchronizer ring 30 is a synchronization mechanism that synchronizes the inner peripheral teeth of the sleeve 29 and the drive gear 28 when they mesh with each other.

  FIG. 1 shows a state where the rear side connection / disconnection mechanism 15 is released. In this state, the sleeve 29 meshes only with the input gear 16a, and the connection between the intermediate shaft 16 and the rotating member 26 is cut off, so that no power is transmitted from the drive pinion 14 to the intermediate shaft 16. On the other hand, when the sleeve 29 is moved and the sleeve 29 meshes with the input gear 16a and the drive gear 28, the rear side connecting / disconnecting mechanism 15 is connected, and the intermediate shaft 16 and the rotating member 26 are connected. Power is transmitted from 14 to the intermediate shaft 16.

  The first coupling (first clutch) 17 is provided between the intermediate shaft 16 and the left rear axle 31, while the second coupling (second clutch) 18 is provided between the intermediate shaft 16 and the right side axle 31. It is provided between the rear wheel axle 32. The first and second couplings 17 and 18 transmit torque between the rear side connecting / disconnecting mechanism 15 and the rear wheels 4 and 5, and change the driving force distribution of the left and right rear wheels 4 and 5. It is configured.

  The first and second couplings 17 and 18 are known electronically controlled couplings configured by, for example, a wet multi-plate clutch, and the transmission torque of the first and second couplings 17 and 18 is controlled by the ECU 19. Thus, the driving force transmitted to the left and right rear wheels 4, 5 is controlled. Specifically, when current is supplied to electromagnetic solenoids (not shown) that control the transmission torques of the first and second couplings 17 and 18, respectively, the first and first coupling forces are proportional to the current values. The two couplings 17 and 18 are fastened. As the transmission torque of the first and second couplings 17 and 18 increases, the driving force transmitted to the left and right rear wheels 4 and 5 increases.

  Thus, by controlling the transmission torque of the first coupling 17 and the transmission torque of the second coupling 18, the torque distribution of the left and right rear wheels 4, 5 can be continuously changed, and the front wheel 2 , 3 and the rear wheels 4 and 5 can be continuously changed in torque distribution. Note that by controlling the transmission torque of the first coupling 17 and the transmission torque of the second coupling 18, a difference in rotational speed between the left and right rear wheels 4, 5 can be allowed. Is not provided with a differential gear like the front differential 8, but since the difference in rotational speed between the left and right rear wheels 4 and 5 can be limited, the effect of LSD can be imparted.

  The ECU (control device) 19 includes, for example, a microcomputer including a CPU, a RAM, a ROM, an input / output interface, and the like, and a program stored in the ROM in advance by the CPU using a temporary storage function of the RAM. Various controls of the vehicle 1 are executed by performing signal processing according to the above. For example, the ECU 19 controls output of the engine 6, shift control of the automatic transmission 7, connection / disconnection control of the front-side connection / disconnection mechanism 11 and rear-side connection / disconnection mechanism 15, and torque capacity of the first and second couplings 17, 18. Execute control etc.

  The ECU 19 is configured to calculate the vehicle body speed based on the rotational speeds of the left and right rear wheels 4 and 5. For example, the ECU 19 normally calculates the vehicle body speed based on the rotational speed of the drive pinion 14 that is the average value of the rotational speeds of the left and right rear wheels 4 and 5 detected by the rotational speed sensor 33, while When any of the rear wheels 4 and 5 is locked, the vehicle body is detected from the rotational speed of the non-locked wheels based on signals from wheel speed sensors (not shown) attached to the rear wheels 4 and 5. Calculate the speed.

Further, the ECU 19 performs wheel brakes 2 _WB , 3 _WB provided on the wheels 2, 3, 4, 5 via a hydraulic brake control circuit (not shown) to execute ABS (Antilock Brake System) control and the like. , 4 _WB, 5 by controlling the _WB, adjusts the braking force generated in each wheel 2, 3, 4, 5 separately. For example, in the ABS control, wheel brakes 2 _WB , 3 _WB , 4 _WB , 5 _WB are used so that the slip ratios of the wheels 2, 3, 4 and 5 are within a predetermined target slip ratio range during braking. Thus, the braking force of the front wheels 2, 3 and the rear wheels 4, 5 is maintained, and the directional stability of the vehicle is improved.

  In the vehicle 1 according to the present embodiment configured as described above, the front-side connection / disconnection mechanism 11 and the rear-side connection / disconnection mechanism 15 are connected together, and the first and second couplings are applied by applying a current. When the transmission torque of 17 and 18 is controlled to a value larger than 0, a 4WD state is reached in which power is transmitted to the front wheels 2 and 3 and the rear wheels 4 and 5. In this 4WD state, the transmission torque of the first and second couplings 17 and 18 is controlled, whereby the torque distribution between the front wheels 2 and 3 and the rear wheels 4 and 5 and the left and right rear wheels 4 and 5 are controlled. Torque distribution is adjusted as necessary.

  Further, in the vehicle 1, when one of the front side connection / disconnection mechanism 11 and the rear side connection / disconnection mechanism 15 is released, the vehicle 1 enters a 2WD state in which power is transmitted only to the front wheels 2 and 3. In particular, when both the front side connection / disconnection mechanism 11 and the rear side connection / disconnection mechanism 15 are released, in the 2WD state, the rotation member 21, the driven pinion 12, the propeller shaft 13, the drive pinion 14 and the like stop rotating, and the rotation is stopped. Is prevented and running resistance is reduced. Hereinafter, a state in which both the front-side disconnection mechanism 11 and the rear-side disconnection mechanism 15 are released is referred to as a disconnect, and a state in which the first and second couplings 17 and 18 of the disconnect are fastened. The state where the first and second couplings 17 and 18 of the disconnection are released is referred to as a 2WD state.

  Further, in the vehicle 1, even if the front side connection / disconnection mechanism 11 and the rear side connection / disconnection mechanism 15 are connected, when the first and second couplings 17 and 18 are released, the rear wheels 4 and 5 are powered. Is not transmitted, and a state similar to the 2WD state in which power is transmitted only to the front wheels 2 and 3 can be created. In such a 2WD state, the rotating member 21, the driven pinion 12, the propeller shaft 13, the drive pinion 14 and the like are rotated together, but the fuel consumption of the 2WD state is lowered. However, when switching from the 2WD state to the 4WD state, it is only necessary to connect the first and second couplings 17 and 18, and quick switching is possible. Hereinafter, a state in which the front side connection / disconnection mechanism 11 and the rear side connection / disconnection mechanism 15 are connected while the first and second couplings 17 and 18 are released is referred to as a 4WD standby state.

  Here, in order to make this embodiment easy to understand, conventional control of the vehicle 101 will be described with reference to FIG.

  A vehicle 101 shown in FIG. 5 is an FF vehicle-based four-wheel drive vehicle, and includes an engine (not shown), left and right front wheels 102 and 103, left and right rear wheels 104 and 105, and an automatic transmission (not shown). ), Front differential 108, transfer ring gear 123, driven pinion 112, propeller shaft 113, coupling 128, drive pinion 114, rear differential ring gear 125, rear differential 115, and ECU (not shown). It is equipped with.

  In this vehicle 101, the power output from the engine is input to the transfer ring gear 123 that rotates integrally with the differential case of the front differential 108 via the automatic transmission and the front differential 108, and then via the driven pinion 112. It is transmitted to the propeller shaft 113. The coupling 128 is a known electronically controlled coupling configured by, for example, a wet multi-plate clutch, and the driving force transmitted to the rear wheels 104 and 105 is controlled by controlling the transmission torque of the coupling 128 by the ECU. Be controlled. The power transmitted from the propeller shaft 113 to the drive pinion 114 via the coupling 128 is transmitted to the rear differential 115 via the rear differential ring gear 125 and then transmitted to the left and right rear wheels 104 and 105 while appropriately applying differential rotation. The

  In such a FF vehicle-based vehicle 101, the vehicle body speed is usually estimated based on the wheel speeds of the left and right rear wheels 104, 105. Therefore, when braking slip occurs when the ABS operates or when the ABS operates, By releasing the coupling 128 to the 2WD state, a drop in the wheel speed generated in the brake slip wheel is prevented from affecting other wheels.

  More specifically, assuming that the rotation speeds of the left and right front wheels 102 and 103 are vfl and vfr, respectively, the rotation speed of the transfer ring gear 123, which is an average value of the rotation speeds of the left and right front wheels 102 and 103, is vtfrig = (vfl + vfr) / 2. It becomes. Similarly, assuming that the rotation speeds of the left and right rear wheels 104 and 105 are vrl and vrr, respectively, the rotation speed of the rear diffring gear 125, which is an average value of the rotation speeds of the left and right rear wheels 104 and 105, is vrdrig = (vrl + vrr) / 2.

  Here, assuming that the left front wheel 102 is locked, the rotational speed of the transfer gear 123 is vtfrig = (0 + vfr) / 2 <the rotational speed of the rear diffring gear 125 vrdrig = (vrl + vrr) / 2. A differential rotation occurs at 128. In this way, when differential rotation occurs in the coupling 128, the rear differential gear 125 has brake torque and the transfer ring gear 123 has drive torque so that the rotation of the transfer ring gear 123 and the rotation of the rear differential ring gear 125 are synchronized. Since these are respectively applied, the rotational speed of the rear wheels 104 and 105 detected by the sensor or the like is lower than the current rotational speed of the rear wheels 104 and 105 that are actually desired to be detected. Therefore, in the conventional vehicle 101, the accuracy of the wheel speed, which is the basis for calculating the vehicle body speed, is ensured by releasing the coupling 128 to the 2WD state when the ABS is operated.

  If the concept of setting the 2WD state during the operation of the ABS is also applied to the vehicle 1 of the present embodiment, the front and rear side disconnection mechanisms 11 and 15 and the first and By releasing the second couplings 17 and 18 to the 2WD state, the accuracy of the wheel speed can be ensured. However, when the vehicle body is in an unstable state, such as during deceleration, it is not preferable to release the first and second couplings 17 and 18 to allow unlimited differential between the left and right rear wheels 4 and 5.

  Therefore, in the vehicle 1 of the present embodiment, when it is possible to ensure the accuracy of the wheel speed, only the front side and rear side connection / disconnection mechanisms 11 and 15 are released, and the first and second couplings are set. 17 and 18 are set in a fastening state. Specifically, when any one of the left and right rear wheels 4 and 5 is locked, the ECU 19 releases the first and second couplings 17 and 18 while only the front wheels 2 and 3 are locked. In this case, the front side and rear side connection / disconnection mechanisms 11 and 15 are set in a released state, and the first and second couplings 17 and 18 are set in a fastening state.

  Thereby, when either one of the left and right rear wheels 4 and 5 is locked, the first and second couplings 17 and 18 are brought into a released state, whereby the rear wheels 4 and 5 are locked (for example, left The vehicle body speed can be accurately calculated while suppressing the wheel speed of the rear wheel 4) from affecting the wheel speed of the non-locking wheel (for example, the right rear wheel 5).

  On the other hand, when only the front wheels 2 and 3 are locked, the front and rear connection / disconnection mechanisms 11 and 15 are released, and the first and second couplings 17 and 18 are brought into a fastening state, whereby the front wheels 2 and 3 are engaged. The vehicle speed is accurately calculated based on the rotational speeds of the rear wheels 4 and 5 while suppressing the wheel speed of the lock wheel 3 (for example, the left front wheel 2) from affecting the wheel speeds of the rear wheels 4 and 5. can do. In addition, by adjusting the transmission torque of the first and second couplings 17 and 18 in the engaged state to limit the difference in rotational speed between the left and right rear wheels 4 and 5, an effect similar to LSD can be obtained. Since it is given, the vehicle body can be stabilized.

  Next, the control procedure of the present embodiment executed by the ECU 19 will be described with reference to the flowcharts of FIGS. Note that FIGS. 2 to 4 show one flowchart divided for convenience of drawing, and that each flowchart is continuous with a circled symbol in these drawings. .

  First, in step S1, the ECU 19 determines whether any of the front wheels 2 and 3 is in a locked state. Specifically, the ECU 19 determines whether or not the rotational speed of any of the front wheels 2 and 3 is 0 based on signals from wheel speed sensors (not shown) attached to the front wheels 2 and 3. If the determination in step S1 is yes, that is, if either of the front wheels 2 and 3 is in the locked state, the process proceeds to step S2.

  In the next step S2, the ECU 19 determines whether any of the rear wheels 4, 5 is locked. If the determination in step S2 is YES, that is, if either of the front wheels 2 and 3 is in the locked state and any of the rear wheels 4 and 5 is in the locked state, the process proceeds to step S3.

  In the next step S3, the ECU 19 determines whether or not the vehicle 1 is in the 4WD state, that is, the front side connecting / disconnecting mechanism 11 and the rear side connecting / disconnecting mechanism 15 are connected together, and the first and second couplings 17, 18 are connected. It is determined whether or not a current is applied to. If the determination in step S3 is YES, the process proceeds to step S4, where the ECU 19 stops applying current to the first and second couplings 17 and 18, and the first and second couplings 17 and 18 are stopped. Is released, and then END. As a result, the vehicle 1 enters the 4WD standby state, and it is possible to prevent the wheel speeds of the lock wheels of the rear wheels 4 and 5 from affecting the wheel speeds of the non-lock wheels.

  On the other hand, if the determination in step S3 is no, the process proceeds to step S5. If the determination in step S3 is NO, the vehicle 1 is in any of the 4WD standby state, the 2WD # d state, and the 2WD state. In step S5, the ECU 19 determines whether or not the vehicle 1 is in the 4WD standby state. .

  If the determination in step S5 is YES, END is performed as it is. Because, in the 4WD standby state, the first and second couplings 17 and 18 are already in the released state, so that the wheel speed of the lock wheels of the rear wheels 4 and 5 affects the wheel speed of the non-lock wheels. Because there is no. On the other hand, if the determination in step S5 is no, the process proceeds to step S6.

  In the next step S6, the ECU 19 determines whether or not the vehicle 1 is in the 2WD # d state. If the determination in step S6 is YES, the wheel speed of the lock wheels of the rear wheels 4 and 5 may affect the wheel speed of the non-lock wheels, so the process proceeds to step S7, where the ECU 19 Then, application of current to the second couplings 17 and 18 is stopped, the first and second couplings 17 and 18 are released, and then END is performed. On the other hand, when the determination in step S6 is NO, since the 2WD state is set, END is performed as it is.

  On the other hand, if the determination in step S2 is NO, that is, if either of the front wheels 2 and 3 is locked but the rear wheels 4 and 5 are both unlocked, the process proceeds to step S8.

  In the next step S8, the ECU 19 determines whether or not the vehicle 1 is in the 4WD state. If the determination in step S8 is YES, the process proceeds to step S9, and after the ECU 19 instructs disconnection, the process proceeds to step S10. As a result, both the front side connecting / disconnecting mechanism 11 and the rear side connecting / disconnecting mechanism 15 are released, so that the wheel speeds of the lock wheels of the front wheels 2 and 3 are prevented from affecting the wheel speeds of the rear wheels 4 and 5. The vehicle body speed can be accurately calculated. Specifically, the vehicle body speed can be calculated based on the rotational speed of the drive pinion 14 that is an average value of the rotational speeds of the left and right rear wheels 4 and 5 detected by the rotational speed sensor 33.

  In the next step S10, the ECU 19 continues to apply current to the first and second couplings 17 and 18 to maintain the fastening state of the first and second couplings 17 and 18, and then performs END. As a result, the differential between the left and right rear wheels 4 and 5 is limited, and an effect like LSD is imparted, so that the vehicle body can be stabilized. On the other hand, if the determination in step S8 is no, the process proceeds to step S11.

  In the next step S11, the ECU 19 determines whether or not the vehicle 1 is in the 4WD standby state. If the determination in step S11 is YES, the process proceeds to step S9 and step S10, and the ECU 19 instructs disconnection in the same way as in the 4WD state, and then supplies current to the first and second couplings 17 and 18. And then END. As a result, it is possible to suppress the influence of the wheel speeds of the lock wheels of the front wheels 2 and 3 on the wheel speeds of the rear wheels 4 and 5 and to stabilize the vehicle body.

  On the other hand, if the determination in step S11 is NO, the vehicle is in the 2WD # d state or the 2WD state and is not affected by the lock wheels of the front wheels 2 and 3, so the process proceeds to step S10 and the ECU 19 performs the first and second cups. A current is applied to the rings 17 and 18, and then END is performed. As a result, the differential between the left and right rear wheels 4 and 5 is limited, and the vehicle body is stabilized.

  On the other hand, if the determination in step S1 is NO, that is, if both the front wheels 2 and 3 are in the unlocked state, the process proceeds to step S12. In the next step S12, the ECU 19 determines whether any of the rear wheels 4 and 5 is locked. If the determination in step S12 is YES, that is, if only one of the left and right rear wheels 4 and 5 is in the locked state, the process proceeds to step S13.

  In the next step S13, the ECU 19 determines whether or not the vehicle 1 is in the 4WD state. If the determination in step S13 is YES, the process proceeds to step S14, where the ECU 19 stops applying current to the first and second couplings 17 and 18, and the first and second couplings 17 and 18 are stopped. Is released, and then END. As a result, the vehicle 1 enters the 4WD standby state, and it is possible to prevent the wheel speeds of the lock wheels of the rear wheels 4 and 5 from affecting the wheel speeds of the non-lock wheels.

  On the other hand, when the determination in step S13 is NO, the process proceeds to step S15, and the ECU 19 determines whether or not the vehicle 1 is in the 4WD standby state. If the determination in step S15 is YES, since the first and second couplings 17 and 18 have already been released, the wheel speeds of the lock wheels of the rear wheels 4 and 5 are the wheel speeds of the non-lock wheels. END as it is.

  On the other hand, when the determination in step S15 is NO, the process proceeds to step S16, and the ECU 19 determines whether or not the vehicle 1 is in the 2WD # d state. If the determination in step S16 is YES, the wheel speed of the lock wheels of the rear wheels 4 and 5 may affect the wheel speed of the non-lock wheels, so the process proceeds to step S17, where the ECU 19 Then, application of current to the second couplings 17 and 18 is stopped, the first and second couplings 17 and 18 are released, and then END is performed. On the other hand, when the determination in step S16 is NO, since the 2WD state is set, END is performed as it is.

  If the determination in step S12 is NO, that is, if the front wheels 2 and 3 and the rear wheels 4 and 5 are all in the unlocked state, the present invention is not applied in the first place, so END is performed as it is.

(Other embodiments)
The present invention is not limited to the embodiments, and can be implemented in various other forms without departing from the spirit or main features thereof.

  In the above embodiment, when only the front wheels 2 and 3 are locked, both the front side and rear side connecting / disconnecting mechanisms 11 and 15 are in the released state. The connection / disconnection mechanism 15 may be in a released state.

  As described above, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  According to the present invention, the stability of the vehicle body can be improved while ensuring the accuracy of the wheel speed. Therefore, the present invention is applied to a control device for a four-wheel drive vehicle including a connection / disconnection mechanism and first and second clutches. Very beneficial.

1 Vehicle 2 Front wheel (main drive wheel)
3 Front wheels (main drive wheels)
4 Rear wheels (sub-drive wheels)
5 Rear wheels (sub drive wheels)
11 Front side connection / disconnection mechanism 15 Rear side connection / disconnection mechanism 17 First coupling (first clutch)
18 Second coupling (second clutch)
19 ECU (control device)

Claims (1)

A connection / disconnection mechanism for connecting / disconnecting a power transmission path for transmitting a part of the driving force transmitted to the main drive wheel to the sub drive wheel, and a power transmission path between the connection / disconnection mechanism and the left and right sub drive wheels, respectively. A four-wheel drive vehicle that includes a first clutch and a second clutch that are provided and capable of transmitting a driving force while allowing a difference in rotation between the left and right auxiliary drive wheels, and that calculates a vehicle body speed based on the rotation speed of the auxiliary drive wheels A control device of
When one of the left and right auxiliary drive wheels is locked, the first and second clutches are released, while when only the main drive wheel is locked, the connection / disconnection mechanism is released. And the control apparatus of the four-wheel drive vehicle characterized by making a 1st and 2nd clutch into a fastening state.

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