JP2011251628A - Control device of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control running quality of a vehicle without requiring a new actuator.SOLUTION: The vehicle 1 includes: front wheels 14 and 14 to which torque from an engine 10 is directly transmitted; and rear wheels 18 and 18 to which the torque from the engine 10 is transmitted through a coupling device 30. An actuator 31 varies a condition of the coupling device 30, and thereby a torque distribution of the front and rear wheels is changed. In the vehicle 1, a frequency of a PWM control output which is output to the actuator 31 of the coupling device 30 is changed to a lower frequency side than the frequency of the PWM control output when a change control of the torque distribution by the coupling device 30 is carried out, thereby applying vibration along a rotation direction of the rear wheels to the rear wheels 18 and 18.

Description

  The present invention relates to a control device that controls traveling characteristics of a vehicle. In particular, the present invention relates to an improved configuration for controlling the running characteristics of a vehicle by adjusting a frictional force between a road surface and a drive wheel (hereinafter sometimes referred to as a tire).

  Generally, in a vehicle that travels with a driving force transmitted from a driving source such as an internal combustion engine transmitted to a tire, even if the driving force from the driving source is the same, the frictional force between the tire and the road surface The running characteristics vary depending on (friction coefficient) and the like. For example, Patent Document 1 controls the running characteristics by adjusting the frictional force between the tire and the road surface by applying vibration (microvibration) to the tire with respect to a vehicle using an electric motor as a running drive source. Technology is shown.

Republished patent WO02 / 000463

  However, in the above-described conventional technology, it is necessary to newly install an actuator (for example, an electric motor) for applying vibration to the tire for each tire. For this reason, there is a concern that the manufacturing cost of the vehicle will rise significantly. In addition, a relatively large space for mounting the actuator is required in the lower part of the vehicle body, and there are problems that the degree of freedom in designing the vehicle is greatly hindered and the layout of the drive system is greatly restricted.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a vehicle control device capable of controlling the running characteristics of a vehicle without requiring a new actuator. .

  In the present invention, means for solving the above-described problems are configured as follows. That is, the present invention includes a main drive wheel to which torque from a drive source is directly transmitted and a slave drive wheel to which torque from the drive source is transmitted via a coupling device, and the coupling device is engaged by an actuator. The vehicle control device is configured to change the torque distribution of the main drive wheel and the slave drive wheel by changing the combined state, and the frequency of the signal output to the actuator is determined by the coupling device. By changing to a lower frequency side than the frequency of the signal when the torque distribution change control is performed, the slave drive wheels are given vibration along the rotation direction.

  In the above configuration, the driven drive (tire) is periodically driven or driven by changing the frequency of the signal output to the actuator of the coupling device to the low frequency side, so that the tire Vibration in the rotational direction is applied. Thereby, the frictional force (friction coefficient) in the front-rear direction of the tire can be reduced, the running resistance of the vehicle can be reduced, and as a result, the fuel consumption rate can be improved.

  In addition, since an actuator of an existing coupling device is used in a vehicle (four-wheel drive vehicle) and the tire is vibrated only by changing the frequency of the signal to this actuator, the vehicle can be operated without requiring a new actuator. Travel characteristics can be controlled. Therefore, the manufacturing cost of the vehicle will not increase significantly, and the degree of freedom in designing the vehicle will not be greatly hindered or the drive system layout will not be greatly restricted.

  In the present invention, when the signal is a pulse signal that periodically repeats ON / OFF of the voltage, and the frequency of the pulse signal is equal to or less than a threshold value based on the relationship between the frequency and the behavior of the vehicle. It is preferable to increase the OFF voltage of the pulse signal.

  According to the above configuration, since the voltage difference between the high voltage voltage and the low voltage voltage of the pulse signal is small, the various kinds of vehicles caused by lowering the frequency of the pulse signal output to the actuator are reduced. It is possible to suppress the adverse effects on the system and functions and the deterioration of ride comfort.

  According to the present invention, by applying vibration in the rotational direction to the driven wheel (tire), the frictional force in the front-rear direction of the tire can be reduced, and the running resistance of the vehicle can be reduced. As a result, the fuel consumption rate can be improved. Moreover, since the tire is vibrated using the actuator of the existing coupling device in the vehicle (four-wheel drive vehicle), the running characteristics of the vehicle can be controlled without requiring a new actuator.

It is a figure which shows typically schematic structure of the power train of the vehicle which concerns on embodiment of this invention. It is sectional drawing which shows schematic structure of a coupling apparatus. It is a figure which shows an example of the PWM control output output to an actuator from ECU in a four-wheel drive state. It is a figure which shows an example of the PWM control output for giving a vibration to a rear wheel. It is a figure which shows the relationship between the friction coefficient in the front-back direction when not giving a vibration to a tire, and a slip ratio. It is a figure which shows the modification of the PWM control output for giving a vibration to a rear wheel. It is a figure which shows an example of the output circuit of the PWM control output of FIG. It is a flowchart which shows an example of the procedure of the driving | running | working characteristic control of the vehicle performed by ECU.

  Embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a diagram schematically showing a schematic configuration of a power train of a vehicle 1 according to an embodiment of the present invention. In FIG. 1, a front wheel drive-based four-wheel drive vehicle is illustrated as the vehicle 1.

  As shown in FIG. 1, the vehicle 1 includes a drive source 10, a transmission 11, front wheels 14 and 14 that are main drive wheels, a propeller shaft 16, a coupling device 30, and a rear wheel that is a sub drive wheel. 18 and 18. Further, the vehicle 1 includes an electronic control unit (ECU) 100 for controlling the driving state, traveling state, and the like of the vehicle 1.

  The drive source 10 is, for example, an internal combustion engine such as a gasoline engine, a diesel engine, or an LPG engine, or an electric motor (motor), or a hybrid system that combines an engine and an electric motor (motor / generator) capable of power running / regenerative control. Applicable. Here, an example using an engine that includes an electronic throttle valve (not shown) and whose output can be electronically controlled as the drive source 10 will be described. For this reason, hereinafter, the drive source 10 is also simply referred to as the engine 10.

  A transmission 11 is connected to the output side of the engine 10. As the transmission 11, for example, various known transmissions such as a selection gear type transmission, a planetary gear type transmission, a belt type or a toroidal type continuously variable transmission can be applied. In this embodiment, the transmission 11 is configured as a trunk axle in which a transmission and a drive shaft are integrated, and a front differential gear 12 is built in the transaxle.

  The transmission 11 is connected to the left and right front drive shafts 13 and 13 via a front differential gear 12. The front drive shafts 13 and 13 are connected to left and right front wheels 14 and 14 which are main drive wheels (drive wheels to which torque from the engine 10 is directly transmitted), respectively.

  A propeller shaft 16 is connected to the output side of the transmission 11 via a transfer gear 15. The propeller shaft 16 is connected to the rear wheel side output shaft 32 via the coupling device 30. The rear wheel output shaft 32 is connected to the left and right rear drive shafts 17 and 17 via the rear differential gear 19. The rear drive shafts 17 and 17 are connected to left and right rear wheels 18 and 18, which are driven wheels (drive wheels to which torque from the engine 10 is transmitted via the coupling device 30), respectively.

  The coupling device 30 has a function of distributing and transmitting the torque of the engine 10 output via the transmission 11 between the front wheels 14 and 14 and the rear wheels 18 and 18. The coupling device 30 includes an actuator 31. Then, the transmission torque transmitted from the propeller shaft 16 to the rear wheel side output shaft 32 is controlled by changing the state of the coupling device 30 by the actuator 31. Thereby, in the vehicle 1, it is possible to switch between the two-wheel drive state and the four-wheel drive state, and to change the torque distribution of the front and rear wheels in the four-wheel drive state. Note that switching between the two-wheel drive state and the four-wheel drive state can be performed by the driver operating the operation switch 108 provided in the vicinity of the driver's seat.

  In this embodiment, an electronically controlled coupling that variably controls the torque distribution ratio of the front and rear wheels in accordance with a control command output from the ECU 100 to the actuator 31 is used as the coupling device 30. A schematic configuration of the coupling device (electronic control coupling) 30 will be briefly described with reference to FIG.

  As shown in FIG. 2, the coupling device 30 includes a bottomed cylindrical housing 33. The housing 33 is connected to the propeller shaft 16 (FIG. 1) via a connecting shaft 34 provided at the bottom thereof. When the rotation of the propeller shaft 16 is transmitted, the housing 33 rotates about the rotation center A1.

  Inside the housing 33, a cylindrical inner shaft 35 that rotates about the rotation center A1 is disposed. The inner shaft 35 is a rotating member that can be rotated when a clutch mechanism described later is engaged and cannot rotate when the clutch mechanism is released. One end portion (left end portion in FIG. 2) of the rear wheel side output shaft 32 that rotates about the rotation center A1 is spline fitted to the inner periphery of the inner shaft 35. For this reason, the inner shaft 35 and the rear wheel side output shaft 32 rotate integrally. A drive pinion gear 32a is provided at the other end (right end in FIG. 2) of the rear wheel side output shaft 32, and the drive pinion gear 32a meshes with the ring gear 19a of the rear differential gear 19 (see FIG. 1).

  On the outer peripheral side of the inner shaft 35, an annular rotor 36 that is rotatable about the rotation center A1 is disposed. The rotor 36 is screwed to the inner periphery of the housing 33 and fixed so as not to rotate by welding. For this reason, the housing 33 and the rotor 36 rotate integrally. An electromagnetic solenoid as the actuator 31 is provided on the outer peripheral side of the rotor 36. The actuator 31 includes an annular iron core 31a made of a magnetic material, and a coil 31b wound around the iron core 31a.

  A clutch mechanism is disposed between the housing 33 and the inner shaft 35. As a clutch mechanism, a pilot clutch 41 engaged / released by an actuator 31 and a main clutch 42 engaged / released in conjunction with the engagement / release operation of the pilot clutch 41 are provided.

  The pilot clutch 41 includes an armature 43, a clutch disk 41a, and a clutch plate 41b. The clutch disk 41 a and the clutch plate 41 b are disposed between the armature 43 and the rotor 36. The armature 43 and the clutch disk 41a are spline-fitted to the inner periphery of the housing 33. An annular cam 44 is mounted on the outer periphery of the inner shaft 35. The cam 44 is provided so as to be rotatable relative to the inner shaft 35. A clutch plate 41 b is splined to the outer periphery of the cam 44.

  The main clutch 42 includes a plurality of clutch disks 42a and a plurality of clutch plates 42b arranged alternately with the plurality of clutch disks 42a. The clutch disk 42 a is spline fitted to the inner periphery of the housing 33, and the clutch plate 42 b is spline fitted to the outer periphery of the inner shaft 35.

  An annular piston 45 is disposed between the main clutch 42 and the pilot clutch 41. The piston 45 is splined to the outer periphery of the inner shaft 35. On the opposite sides of the cam 44 and the piston 45, a plurality of concave portions 44a, 45a corresponding to the respective cam surfaces are formed. A plurality of balls 46 (only one is shown in FIG. 2) are provided between the cam 44 and the piston 45 so as to be fitted into the recesses 44a and 45a.

  Here, the operation of the coupling device 30 configured as described above will be described.

  First, when the actuator (electromagnetic solenoid) 31 is in a non-excited state (OFF state), both the pilot clutch 41 and the main clutch 42 are released. For this reason, the coupling device 30 is released. In this released state, the torque transmitted from the propeller shaft 16 to the housing 33 is not transmitted to the inner shaft 35 and the rear wheel side transmission shaft 32. Therefore, the vehicle 1 is in a two-wheel drive state.

  On the other hand, when the actuator (electromagnetic solenoid) 31 is in an excited state (ON state), a magnetic flux is generated around the electromagnetic solenoid, and the armature 43 is attracted to the rotor 36 side. Thereby, the clutch disk 41a of the pilot clutch 41 and the clutch plate 41b are engaged. That is, the pilot clutch 41 is engaged. As a result, torque transmitted from the propeller shaft 16 to the housing 33 is transmitted to the cam 44 via the pilot clutch 41.

  When torque is transmitted to the cam 44, the cam 44 and the piston 45 rotate relative to each other. Then, a force that pushes the ball 46 to the outside of the cam 44 and the recesses 44a and 45a of the piston 45 acts, and a thrust load is generated in such a direction that the cam 44 and the piston 45 are separated from each other in the axial direction. At this time, the cam 44 is received by the thrust bearing 47 and is prevented from moving to the rotor 36 side. Therefore, the piston 45 is pressed against the main clutch 42 by the thrust load, and the clutch disk 42a and the clutch plate 42b are engaged. That is, the engagement force of the pilot clutch 41 is amplified by the cam 44, the ball 46, and the piston 45 and transmitted to the main clutch 42. When the main clutch 42 is engaged, torque transmitted from the propeller shaft 16 to the housing 33 is transmitted to the inner shaft 35 and the rear wheel side output shaft 32 via the main clutch 42. Thereby, the vehicle 1 will be in a four-wheel drive state.

  Then, by controlling the current supplied to the actuator 31 by the ECU 100, the engagement force of the main clutch 42 changes, and the engagement state of the coupling device 30 changes. Thereby, the transmission torque from the propeller shaft 16 to the rear wheel side output shaft 32 changes. That is, the torque distribution rate of the front and rear wheels is controlled by the current control of the actuator 31. As the current of the actuator 31 is increased, the engagement force of the main clutch 42 is increased, and the transmission torque from the propeller shaft 16 to the rear wheel side output shaft 32 is increased. When the current of the actuator 31 exceeds a predetermined value, torque is transmitted from the propeller shaft 16 to the rear wheel side output shaft 32 in a directly connected state.

  In this embodiment, the current supplied to the actuator 31 is controlled by PWM (Pulse Width Modulation) control. For example, a pulse signal (PWM control output) P <b> 1 as shown in FIG. 3 is sent from the ECU 100 to the actuator 31. The PWM control output P1 output to the actuator 31 is a pulse signal that periodically repeats ON / OFF of a predetermined voltage Von (for example, 12V), and its frequency F1 (= 1 / T1) is, for example, 0. 5 to 15 kHz. The magnitude of the current supplied to the actuator 31 is controlled by controlling the duty ratio D1 (= t1 / T1) of the PWM control output P1. The greater the duty ratio D1, that is, the greater the value of the pulse width t1 for the cycle T1, the greater the current of the actuator 31.

  The ECU 100 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory) and the like. The ROM stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU executes various arithmetic processes based on various control programs and maps stored in the ROM. The RAM is a memory that temporarily stores calculation results in the CPU, data input from various sensors, and the like.

  The ECU 100 includes wheel speed sensors 101 and 101 that detect the rotational speeds of the front wheels 14 and 14, wheel speed sensors 102 and 102 that detect the rotational speeds of the rear wheels 18 and 18, a yaw rate sensor 103 that detects the yaw rate of the vehicle 1, A steering angle sensor 104 that detects the steering angle of the steering, an outside air temperature sensor 105 that detects the outside air temperature of the vehicle 1, a crank position sensor 106 that detects the rotation speed of the engine 10, and a cooling water temperature sensor that detects the cooling water temperature of the engine 10. Various sensors including 107 are connected. The ECU 100 is connected to various switches including the operation switch 108 and the like for inputting a switching instruction between the two-wheel drive state and the four-wheel drive state. Then, the ECU 100 performs various controls of the traveling state of the vehicle 1 including the control of changing the torque distribution of the front and rear wheels by the coupling device 30 and the traveling characteristic control of the vehicle 1 described below based on signals from various sensors and various switches. Execute.

-Characteristic part of embodiment-
In this embodiment, the frequency of the pulse signal output to the actuator 31 of the coupling device 30 is changed to a lower frequency side than the frequency of the pulse signal when changing the torque distribution of the front and rear wheels by the coupling device 30 is controlled. As a result, vibration along the rotational direction is applied to the rear wheels 18 and 18 that are the driven wheels, thereby adjusting the frictional force (friction coefficient) between the rear wheels 18 and 18 and the road surface. The running characteristics of the vehicle 1 are controlled. The vibration means a vibration that affects the running resistance of the vehicle 1 as will be described later. Hereinafter, the running characteristic control of the vehicle 1 will be described in detail with reference to FIGS.

  First, a specific method for applying vibration to the rear wheels 18, 18 will be described.

  In this embodiment, the ECU 100 gives a PWM control output P2 having a waveform as shown in FIG. 4 to the actuator 31 of the coupling device 30 in order to give the rear wheels 18 and 18 vibration along the rotation direction. Output. That is, the ECU 100 uses the PWM control output P2 as shown in FIG. 4 for the coupling device 30 instead of the PWM control output (for example, see FIG. 3) for performing the change control of the torque distribution of the front and rear wheels by the coupling device 30. The data is sent to the actuator 31.

  The PWM control output P2 in FIG. 4 is a pulse signal that periodically repeats ON / OFF of a predetermined voltage Von (for example, 12V), similarly to the PWM control output P1 in FIG. The frequency F2 (= 1 / T2) of the PWM control output P2 of FIG. 4 is significantly lower than the frequency F1 of the PWM control output P1 of FIG. 3 described above (F2 << F1), and the PWM control of FIG. It is set to about 1/100 to 1/1000 of the frequency F1 of the output P1. In other words, the period T2 of the PWM control output P2 in FIG. 4 is significantly larger than the period T1 of the PWM control output P1 in FIG. 3 (T1 << T2), and the period T1 of the PWM control output P1 in FIG. Is set to about 100 to 1000 times. The frequency F2 of the PWM control output P2 in FIG. 4 is set to 1 Hz, for example. The duty ratio D2 (= t2 / T2) of the PWM control output P2 in FIG. 4 is set to be the same as the duty ratio D1 of the PWM control output P1 in FIG.

  With such a change in the frequency of the PWM control output, the voltage ON state time during which the predetermined voltage Von is applied (t2 in FIG. 4) and the voltage OFF state time during which the predetermined voltage Von is not applied (T2-t2 in FIG. 4) 4 is significantly longer than the PWM control output P1 in FIG. Therefore, when the PWM control output P2 of FIG. 4 is output to the actuator 31 instead of the PWM control output P1 of FIG. 3, the rear wheels 18 and 18 exhibit the following behavior.

  First, during the voltage ON state, the coupling device 30 is in an engaged state, and the front wheels 14 and 14 and the rear wheels 18 and 18 are both driven. At this time, the front wheels 14 and 14 and the rear wheels 18 and 18 are driven at substantially the same rotational speed. On the other hand, during the voltage OFF state, the coupling device 30 is in the released state, and only the front wheels 14 and 14 are in the driving state. At this time, the rear wheels 18 and 18 are driven to rotate following the front wheels 14 and 14. Since the voltage ON state and the voltage OFF state are periodically repeated as shown in FIG. 4, the driving state and the driven state are periodically generated in the rear wheels 18 and 18. As a result, vibration (microvibration) along the rotation direction is applied to the rear wheels 18 and 18. In this case, since the duty ratio D2 of the PWM control output P2 in FIG. 4 is the same as the duty ratio D1 of the PWM control output P1 in FIG. 3, the torque distribution ratio of the front and rear wheels is not changed.

  Here, an operation when vibration is applied to the rear wheels (tires) 18 and 18 as described above will be described.

  Here, first, the correspondence relationship between the slip ratio of the tires 18 and 18 and the friction coefficient between the tires 18 and 18 and the road surface will be described. The correspondence relationship between the slip ratio of the tires 18 and 18 and the friction coefficient between the tires 18 and 18 and the road surface varies depending on the road surface condition. Further, as described above, it is possible to arbitrarily adjust the coefficient of friction between the tires 18 and 18 and the road surface by giving the tires 18 and 18 vibrations in the rotation direction (microvibrations). Are known. Specifically, when the tires 18 and 18 are vibrated in the rotational direction, the friction coefficient between the tires 18 and 18 and the road surface is arbitrarily adjusted by controlling the amplitude, frequency, phase, etc. of the vibrations. It is known to do. This principle is described in Patent Document 1 described above. For example, a friction model using a rubber block instead of the tires 18 and 18 can be expressed by the following vibration equation (1).

  In the vibration equation (1), Fn is a load in the vertical direction in which the rubber block contacts the road surface. Therefore, μ · Fn is a frictional force (μ is a friction coefficient of the road surface) acting on the rubber block sliding in a certain direction. M is the mass of the rubber block, and ω0 is the resonance frequency of the rubber block. By solving the vibration equation (1), the ratio μrel between the frictional force when the rubber block is not vibrated and the frictional force when the rubber block is vibrated is obtained by the following equation (2). .

  In this equation (2), μe is a friction coefficient when vibration is applied to the rubber block, μn is a friction coefficient when vibration is not applied to the rubber block, and K is a spring constant between the rubber block and the road surface. , C is a damping coefficient of the rubber block.

  From the above two formulas (1) and (2), the friction between the tires 18 and 18 and the road surface by applying vibrations in the front-rear direction of the tires 18 and 18 to be controlled, specifically in the rotational direction. It can be seen that the coefficient can be adjusted arbitrarily. The ratio μrel is dependent on the frequency ω of the applied vibration, and the value of the ratio μrel tends to decrease as the frequency ω approaches the resonance frequency ω0. In addition, by applying vibration in the rotation direction of the tires 18 and 18, the relationship between the friction coefficient and the slip ratio in the front-rear direction of the tires 18 and 18 increases, for example, as shown by the broken line in FIG. It is known that the friction coefficient tends to increase with this. This is also described in Patent Document 1 described above.

  In this embodiment, in order to estimate whether or not the actual friction coefficient has become the target friction coefficient, the ECU 100 stores a map and data indicating the relationship between the slip ratio and the friction coefficient. And while estimating the slip ratio of the tires 18 and 18, an actual friction coefficient can be estimated from a map and data. Note that the slip ratio of each tire 18, 18 can be estimated based on signals from wheel speed sensors 102, 102 that detect the rotational speed of each tire 18, 18, and an estimation method thereof is disclosed in, for example, Japanese Patent Laid-Open No. 2002-2002. Since it is well known as described in Japanese Patent Application Laid-Open No. 274356, Japanese Patent Application Laid-Open No. 6-258196, and the like, detailed description thereof will be omitted.

  As described above, by applying vibration in the rotational direction to the tires 18 and 18, it is possible to adjust the friction coefficient in the front-rear direction between the tires 18 and 18 and the road surface. Here, when the case where vibration is applied to the tires 18 and 18 is compared with the case where the vibration is not applied, if the slip ratio in the front-rear direction is the same, the case where vibration is applied does not give vibration. In comparison, it is known that the friction coefficient in the front-rear direction of the tires 18 and 18 is small (see FIG. 5). This is described in Patent Document 1 described above.

  As described above, in this embodiment, the rear wheels (tires) 18 and 18 are periodically driven by changing the frequency of the PWM control output output to the actuator 31 of the coupling device 30 to the low frequency side. Thus, the tires 18 and 18 are imparted with vibrations in the rotational direction. Thereby, as shown in FIG. 5, the frictional force (friction coefficient) in the front-rear direction of the tires 18, 18 can be reduced, and the running resistance of the vehicle 1 can be reduced. As a result, the fuel consumption rate can be reduced. Improvements can be made. Strictly speaking, even when the PWM control output P1 of FIG. 3 is output to the actuator 31, vibrations in the rotational direction may occur in the rear wheels 18 and 18. However, even if the rear wheels 18 and 18 vibrate along the rotation direction, as described above, the PWM control output P1 in FIG. Never give.

  As described above, in the conventional technique, it is necessary to mount an actuator (for example, an electric motor) for applying vibration to the tire for each tire. However, in this embodiment, since the actuator 31 of the existing coupling device 30 is used in a four-wheel drive vehicle and the tires 18 and 18 are vibrated only by changing the frequency of the PWM control output to this actuator 31, The traveling characteristics of the vehicle 1 can be controlled without requiring a simple actuator. Therefore, the manufacturing cost of the vehicle 1 is not significantly increased, and the degree of freedom of design of the vehicle 1 is not greatly obstructed, and the layout of the drive system (drive train) is not greatly restricted. .

  By the way, as the frequency of the PWM control output output to the actuator 31 of the coupling device 30 is lowered, the vibration generated in the rear wheels 18 and 18 is increased, and accordingly, the behavior change of the vehicle 1 is also increased. For this reason, there is a concern that the various systems and functions of the vehicle 1 may be adversely affected or the ride quality may be deteriorated. Therefore, a PWM control output P3 as shown in FIG.

  The PWM control output P3 in FIG. 6 is a pulse signal having a frequency F2, a duty ratio D2, and a pulse width t2, similarly to the PWM control output P2 in FIG. However, unlike the PWM control output P2 in FIG. 4, the PWM control output P3 in FIG. 6 is a pulse signal in which a high voltage voltage Von (for example, 12V) and a low voltage voltage Va (for example, 8V) are periodically repeated. It is said that. That is, the low voltage voltage Va of the PWM control output P3 in FIG. 6 is higher than the OFF voltage (0 V) of the PWM control output P2 in FIG. Thus, in the PWM control output P3 of FIG. 6, the voltage difference (amplitude) between the high voltage voltage Von and the low voltage voltage Va is smaller than the PWM control output P2 of FIG. Accordingly, various systems and functions of the vehicle 1 caused by lowering the frequency of the PWM control output output to the actuator 31 by sending the PWM control output P3 of FIG. 6 to the actuator 31 of the coupling device 30. Can be prevented from adversely affecting the vehicle and causing deterioration in ride comfort.

  The PWM control output P3 as shown in FIG. 6 can be obtained by an output circuit 200 as shown in FIG. 7, for example. The output circuit 200 shown in FIG. 7 is a circuit including a power supply VBATT, resistors R1 and R2, transistors TR1 and TR2, diodes D1 and D2, and an electromagnetic solenoid SOL. The electromagnetic solenoid SOL corresponds to the actuator 31 described above. The power supply VBATT is, for example, an in-vehicle battery or a capacitor.

  Output instruction VH for high voltage output and output instruction VL for low voltage output are alternately output from ECU 100 to output circuit 200. When the output instruction VH for high voltage output is output, the voltage (for example, 12V) of the power supply VBATT is applied to the electromagnetic solenoid SOL as it is. On the other hand, when the output instruction VL for low voltage output is output, a voltage (for example, 8V) obtained by subtracting a voltage drop (for example, 4V) by the resistor R1 from the voltage of the power supply VBATT is applied to the electromagnetic solenoid SOL.

  Then, it is possible to obtain a PWM control output P3 as shown in FIG. 6 by appropriately setting periods for outputting the output instructions VH and VL from the ECU 100 to the output circuit 200. For example, the period for outputting the output instruction VH for high voltage output may be set to t2, and the period for outputting the output instruction VL for low voltage output may be set to (T2-t2).

  Note that the output circuit 200 can obtain the PWM control output P1 as shown in FIG. 3 and the PWM control output P2 as shown in FIG. That is, it is only necessary to output only the output instruction VH for high voltage output from the ECU 100 to the output circuit 200 in a predetermined period and a predetermined cycle. For example, if the period for outputting the output instruction VH for high voltage output is set to t1 and the cycle is set to T1, it is possible to obtain the PWM control output P1 as shown in FIG. Further, if the period for outputting the output instruction VH for high voltage output is set to t2 and the cycle is set to T2, the PWM control output P2 as shown in FIG. 4 can be obtained. Therefore, the output circuit 200 can easily switch the PWM control output P1 of FIG. 3, the PWM control output P2 of FIG. 4, and the PWM control output P3 of FIG.

  Next, the procedure of the driving characteristic control of the vehicle 1 to which the characteristic part of the embodiment as described above is applied will be described with reference to the flowchart of FIG.

  This flowchart relates to the travel characteristic control of the vehicle 1 executed by the ECU 100, and is repeatedly executed at predetermined time intervals when the vehicle 1 is in the four-wheel drive state. Whether or not the vehicle 1 is in the four-wheel drive state can be determined based on, for example, a signal from the operation switch 108 that inputs a switching instruction between the two-wheel drive state and the four-wheel drive state.

  First, in step ST1, the ECU 100 calculates an output instruction value of a PWM control output to be output to the actuator 31 of the coupling device 30. In this case, based on signals from various sensors that detect the traveling state of the vehicle 1, an output instruction for PWM control output during traveling in the four-wheel drive state (for example, PWM control output P1 as shown in FIG. 3). A value (duty ratio, etc.) is calculated.

  Next, in step ST2, the ECU 100 determines whether it is necessary to apply vibrations along the rotational direction to the rear wheels 18, 18. In other words, it is determined whether or not the frequency of the PWM control output to be output to the actuator 31 needs to be changed to the low frequency side. This determination can be made based on signals from various sensors that detect the running state of the vehicle 1. Here, as a case where it is necessary to give vibration to the rear wheels 18, 18, there is a case where it is no longer necessary to continue running in the four-wheel drive state. For example, there are a case where the vehicle travels straight in a steady state (a state where the vehicle travels with little acceleration / deceleration), and a case where the vehicle travels straight on a high μ road.

  If the determination in step ST <b> 2 is negative, the process proceeds to step ST <b> 6 and the ECU 100 outputs a PWM control output to the actuator 31. In this case, for example, a PWM control output P1 as shown in FIG.

  On the other hand, if the determination in step ST2 is affirmative, the process proceeds to step ST3, and the ECU 100 changes the frequency of the PWM control output to be output to the actuator 31 to the low frequency side. In this case, the frequency of the PWM control output to the actuator 31 is calculated based on signals from various sensors that detect the running state of the vehicle 1.

  Next, in step ST4, the ECU 100 determines whether or not the frequency of the PWM control output to the actuator 31 obtained in step ST3 is equal to or less than the threshold value Fth. This threshold value Fth is set based on the relationship between the frequency of the PWM control output to the actuator 31 and the behavior of the vehicle 1, and is stored in the ROM of the ECU 100. As described above, since the behavior change of the vehicle 1 increases as the frequency of the PWM control output output to the actuator 31 is lowered, the threshold value Fth is set from the viewpoint of suppressing the behavior change of the vehicle 1.

  If the determination in step ST <b> 4 is negative, the process proceeds to step ST <b> 6 and the ECU 100 outputs a PWM control output to the actuator 31. In this case, for example, a PWM control output P2 as shown in FIG.

  On the other hand, if the determination in step ST4 is affirmative, the process proceeds to step ST5, where the ECU 100 sets the low voltage during PWM control output to the actuator 31 to a voltage higher than 0 [V]. The low voltage voltage of the PWM control output is, for example, the low voltage voltage Va of the PWM control output P3 of FIG. 6 described above. Then, ECU 100 outputs a PWM control output to actuator 31 in step ST6. In this case, for example, a PWM control output P3 as shown in FIG.

  As described above, the PWM control output that is output to the actuator 31 of the coupling device 30 is changed according to the traveling state of the vehicle 1. By changing the PWM control output to be output to the actuator 31 of the coupling device 30 to the PWM control output P1 as shown in FIG. 3, the vehicle 1 can appropriately travel in the four-wheel drive state. Further, by changing the PWM control output that is output to the actuator 31 of the coupling device 30 to the PWM control output P2 as shown in FIG. 4, the running resistance of the vehicle 1 can be reduced, and the fuel consumption rate can be improved. Can be planned. Further, by changing the PWM control output to be output to the actuator 31 of the coupling device 30 to the PWM control output P3 as shown in FIG. 6, various systems and functions of the vehicle 1 are controlled while controlling the running characteristics of the vehicle 1. Can be prevented from adversely affecting the vehicle and causing deterioration in ride comfort.

-Other embodiments-
The present invention is not limited only to the above-described embodiments, and all modifications and applications within the scope of the claims and within the scope equivalent to the scope are possible.

  The above-described configuration of the electronically controlled coupling as the coupling device (see FIG. 2) is an example, and if it is possible to control the torque distribution ratio of the front and rear wheels by an actuator, a coupling device of another configuration may be used. It may be used. In the above embodiment, an example in which the actuator is an electromagnetic solenoid has been described. However, the actuator may be, for example, an electric motor, an electromagnetic clutch, or the like.

  In the above embodiment, an example in which the present invention is applied to a front wheel drive-based four-wheel drive vehicle in which the front wheels are the main drive wheels and the rear wheels are the sub drive wheels has been described. The present invention can also be applied to a four-wheel drive vehicle based on a rear wheel drive in which the front wheels are driven wheels.

  The present invention can be used in a four-wheel drive vehicle that changes the torque distribution of the front and rear wheels by changing the state of the coupling device by an actuator.

1 vehicle 10 engine (drive source)
18 Rear wheel (tire)
30 coupling device 31 actuator 100 ECU

Claims (2)

A main drive wheel to which torque from a drive source is directly transmitted and a slave drive wheel to which torque from the drive source is transmitted via a coupling device, and an engagement state of the coupling device is changed by an actuator. A vehicle control device configured to change the torque distribution between the main drive wheel and the sub drive wheel,
By changing the frequency of the signal output to the actuator to a lower frequency side than the frequency of the signal in the case of performing torque distribution change control by the coupling device, the rotational speed of the driven wheel is changed in the rotation direction. A vehicle control device characterized by applying vibration along the vehicle. The vehicle control device according to claim 1,
The signal is a pulse signal that periodically repeats ON / OFF of the voltage,
The vehicle control device characterized by increasing the OFF-time voltage of the pulse signal when the frequency of the pulse signal is not more than a threshold value based on the relationship between the frequency and the behavior of the vehicle.

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