JPH06104459B2 - Vehicle four-wheel steering system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a four-wheel steering system for a vehicle such as an automobile, and more specifically, a differential gear for connecting a front wheel steering mechanism and a rear wheel steering mechanism. The present invention relates to a four-wheel steering system using a three-mode motor operation control via the system.

[Prior Art] Conventionally, in a four-wheel steering system of a vehicle, in order to perform steering control of rear wheels in conjunction with steering of front wheels, hydraulic, mechanical, electric, or combined control of mechanical and electric types. Mechanisms have been proposed or used, but those devices have a complicated structure.

On the other hand, a four-wheel steering system has been proposed in which a differential gear device is used to connect the front wheel steering mechanism and the rear wheel steering mechanism, thereby suppressing the complication of the device (Japanese Patent Laid-Open No. 59-81272). And JP-A-60-197471).

A conventionally proposed four-wheel steering system of this type is shown in FIG.

In FIG. 6, reference numeral 101 denotes a steering shaft which is connected to a steering wheel (not shown) at one end side, and steering rotation of the steering shaft 101 in the A and B directions is performed by the pinion 10.
2 and through the rack 103, the rack bar 103 is converted into translation in the C and D directions, and the front wheels (not shown) can be steered in the right or left direction. The extension 104 of the steering shaft 101 is connected to a ring gear 107 of a differential gear unit 106 via a drive pinion gear 105. The first side gear 108 of the differential gear device 106 is a motor 112 via a worm 111 that meshes with a worm gear 110 attached to one end of a shaft 109.
Connected to the output shaft 113 of. The motor 112 is
Motor based on information about steering direction and front wheel steering angle
It is connected to a motor control mechanism 114 that controls the rotating direction and the rotating speed of 112 and always drives the motor by energization. The second side gear 115 of the differential gear unit 106 is connected to a rear wheel steering mechanism (not shown) via a shaft 116, and the E of the shaft 116 is connected to the rear wheel steering mechanism.
Alternatively, the rear wheel (not shown) is steered to the right or left by rotation in the F direction.

In this four-wheel steering system 117, the rotation speed of the ring gear 107 is N, the rotation speed of the shaft 109 is N1, and the rotation speed of the shaft 116 is
If N2, N2 = 2N-N1, and when the vehicle speed is lower than the predetermined value, the motor 112 is rotated so that the shaft 109 is rotated with N1> 2N, and the rear wheels are steered in the opposite direction to the front wheels. If the vehicle speed matches the predetermined value,
Drive the motor 112 so as to rotate the N1 = 2N and perform the two-wheel steering without turning the rear wheels. If the vehicle speed is higher than the predetermined value, the motor 109 is rotated so that the shaft 109 rotates at N1 <2N. 112 is driven to steer the rear wheels in the same phase as the front wheels.

[Problems of Prior Art] However, in the four-wheel steering system 117 as described above, the worm 1
Since the motor 112 and the side gear 108 of the differential gear unit 106 are connected via the 11 and the worm gear 110, not only electric power is always used during steering but also reverse rotation is transmitted from the worm gear 110 to the worm 111. Because it ’s difficult,
If the rotation of the motor 112 is not properly performed, for example, if the output of the motor power source (battery) mounted on the vehicle is reduced, N1 <2N may occur and only in-phase steering in the high-speed traveling mode may be performed. is there.

The present invention has been made in view of the above points, and an object thereof is to steer the rear wheels in three modes of antiphase, no phase, or the same phase with respect to the steering direction of the front wheels according to the vehicle speed. In addition, the structure is relatively simple and compact,
It is to provide a four-wheel steering device that can operate in a fail-safe manner.

[Means for Solving the Problems] According to the present invention, the above-mentioned object further includes a return mechanism for returning the rear wheel to the neutral position, and the one side gear and the output shaft of the motor are provided. The connection is performed by a power transmission mechanism capable of transmitting power in both directions from the one side gear to the motor output shaft and from the motor output shaft to the one side gear. When the vehicle speed is lower than the range, the motor is driven to rotate so that the steering position of the rear wheels is opposite to the steering phase of the front wheels, and when the vehicle speed matches the given range, the steering of the rear wheels is performed. In order to prohibit the above, the output shaft of the motor is made to idle so that the rotational force given to the ring gear is released to the motor side, and when the vehicle speed is higher than the given range, the steering phase of the rear wheels is changed to that of the front wheels. Rotational braking is applied to the motor so that it is in the same phase as the steering phase. As described above, this is achieved by the four-wheel steering system of the vehicle that constitutes the motor control mechanism.

[Operation and Effect] In the four-wheel steering system of the present invention, the steering information of the front wheels and the output of the rear-wheel steering control motor are transmitted to the rear-wheel steering mechanism via the differential gear unit to control the rear-wheel steering. Therefore, not only can the steering device be formed simple and compact, but the connection between the one side gear and the output shaft of the motor is
It is performed by a power transmission mechanism capable of transmitting power in both directions from the one side gear to the motor output shaft and from the motor output shaft to the one side gear, and the vehicle speed is higher than a given range. When it is low, the motor is energized to rotate the rear wheels so that the steering phase is opposite to the steering phase of the front wheels. When the vehicle speed matches the given range, the steering of the rear wheels is changed. In order to prohibit, when the output shaft is idling by turning off the power supply to the motor so that the rotational force given to the ring gear is released to the motor side, and the vehicle speed is higher than the given range, the steering phase of the rear wheels Since the motor control mechanism is configured to electrically apply rotational braking to the motor in order to make the front wheel in the same phase as the steering phase, the electric power is supplied only in the opposite phase to the front wheel steering direction according to the vehicle speed. It is a motor drive by energizing, and energizing when there is no phase And because the free, or at the time of the same phase may perform steering of the rear wheels 3 mode using a steering power of the front wheel. Moreover, since the four-wheel steering system of the present invention has the return mechanism for returning the rear wheels to the neutral position, when the motor is de-energized and its output shaft is allowed to idle as described above, the return mechanism works. , The rear wheels can be returned to the neutral position. Further, even when the rotational driving ability of the motor by the motor control mechanism is reduced or eliminated, the rear wheels can return to the neutral state without phase and be held in a fail-safe manner.

[Embodiment] Next, a four-wheel steering system according to a preferred embodiment of the present invention will be described with reference to the drawings.

1 to 5, reference numeral 1 denotes an interlocking shaft connected to the front wheel steering mechanism so as to transmit a part of the front wheel steering force of a front wheel steering mechanism (not shown) including a power steering mechanism. The interlocking shaft 1 is rotated in the G or H direction by a rotation angle proportional to the magnitude of the front wheel steering angle as the front wheels 51 (FIGS. 3 to 5) are steered to the right or left. Reference numeral 2 denotes a differential gear device, and a bevel gear 4 attached to one end of the interlocking shaft 1 meshes with a ring gear 3 which is a bevel gear integrated with a housing of the differential gear device 2.

5 is a vehicle speed sensor that detects the traveling speed J of the vehicle 50 (Fig. 3 etc.) and outputs a speed signal J, and 6 is a steering angle signal that detects the steering angle K (including direction and size) of the front wheels 51. Reference numeral 7 is a steering angle sensor that outputs K, and 7 is a motor control mechanism that controls rotational drive of a servo motor or a step motor 8 in accordance with the vehicle speed signal J and the steering angle signal K, as described later. DC for motor 8
The control using the servo is based on the J signal of the vehicle speed sensor 5, the steering angle of the steering angle signal, and the K signal of the steering direction.
Energization control is performed by the PWM circuit, the motor 8 is rotationally driven, and at the time of braking, the generated voltage generated by the idling of the motor 8 is regenerated, and the PWM circuit is short-circuit controlled based on the above both sensor signals to apply rotational braking to the motor 8. Hang In the case of the step motor 8, the motor 8 is driven by pulse number transmission control, and the holding torque when the rotation step of the motor 8 is stopped is used during braking. When the vehicle speed J is lower than a given first reference speed J1, the motor control mechanism 7 has a rotation direction and a rotation direction that makes the steering phase of the rear wheels 52 opposite to the steering phase of the front wheels 51. When the angle changes, the motor 8 is energized and driven to rotate, and the vehicle speed J
Is a given reference vehicle speed range J2 (however, if it corresponds to J1J2J3, electric power to the motor 8 is released so that the rotational force applied to the ring gear 3 is released to the motor 8 side in order to prohibit the steering of the rear wheels 52. When the supply is stopped and the output shaft 10 is idled, and the vehicle speed J is higher than the second given reference vehicle speed J3, the motor 8 is controlled to make the steering phase of the rear wheels 52 the same as the steering phase of the front wheels 51. The rotary braking servomotor is configured to apply dynamic braking, and the stepping motor is implemented to hold braking, where 9 is an encoder for detecting the amount of rotation of the motor 8 and 60 is a vehicle.
It is a power source for a motor drive battery and an alternator mounted on the 50.

A spur gear 11 is integrally attached to an output shaft 10 of the motor 8, and the spur gear 11 is another spur gear fixed to a shaft 13 integral with a first side gear 12 of the differential gear device 3.
It meshes with 14. The spur gears 11 and 14 form a power transmission mechanism capable of mutually transmitting power between the output shaft 10 of the motor 8 and the first side gear 12 of the differential gear device 3.

Reference numeral 18 is a second side gear that is concentric with the ring gear 3 and the first side gear 12, and the second side gear 18 is, like the first side gear 12, a second side gear that is rotated around an axis 15 orthogonal to the shaft 13. The two bevel gears 16 and 17 are meshed with each other and are connected to a rack bar 21 of a rear wheel steering mechanism including a rack and pinion device via a ball screw 20 in a shaft 19 fixed to the second side gear 18. Incidentally, 22 is a return mechanism for returning the rack bar 21 to the neutral position, the return mechanism 22 is supported at one end by a mounting portion 23 integrated with the vehicle body 50, and an elastic member 24 supported at the other end by the rack bar 21, 2
It consists of 5.

Next, the four-wheel steering system 30 of the vehicle 50 having the above structure
The operation of will be described.

In the following, only the case where the front wheels 51 are steered to the right will be described for the sake of simplicity. When the front wheel 51 is steered to the left, the rotational direction or translational direction of each member is reversed, and the other points are substantially the same.

When the front wheels 51 are steered to the right, as indicated by the broken line in FIG. 3,
The interlocking shaft 1 is rotated in the G direction in proportion to the rightward steering speed and the steering angle, and the ring gear 3 of the differential gear device 2 is rotated in the L direction.

The vehicle speed signal J from the vehicle speed sensor 5 is the predetermined first reference speed J1.
If it is lower than this, the control mechanism 7 rotationally drives the motor 8 as shown by the solid line in FIG.
Rotate in the direction. (The rotation direction indicated by the solid line in FIGS. 3 to 5 indicates the direction of rotation caused by the rotation driving force of the motor 8, and the rotation direction indicated by the broken line indicates the rotation direction caused by the rotation driving force from the interlocking shaft 1. With the rotation of the output shaft 10 in the M direction, the shaft 13 is rotated in the L direction via the spur gears 11 and 14. Here, the output shaft by the control mechanism 7
The rotation angle control of 10 is performed so that P1> 2P, where P is the rotation angle of the ring gear 3 from the neutral position defined by the return mechanism 20 and P1 is the rotation angle of the first side gear 12. Be seen. In this case, the second side gear 18 is rotated in the M direction through the Q direction rotation of the bevel gears 16 and 17, and the rack bar 21
Is translated in the R direction, and the rear wheel 52 is steered to the left. Therefore, the front wheels 51 and the rear wheels 52 are in opposite phases, and the vehicle 50 can be steered with a small turning radius. In the above, the time-dependent rotation angle change of the output shaft 10 of the motor 8 is determined by the time change of the steering angle signal K of the front wheels 51 from the steering angle sensor 6.

In this way, the reverse phase steering is performed by the motor steering by the motor output in FIG. 2 which shows the vehicle speed dependence of the steering angle or the steering angle ratio of the rear wheels 52 when the steering angle of the front wheels 51 is constant. It corresponds to the low vehicle speed range indicated by. In the low vehicle speed region I, the steering angle or the steering angle ratio of the rear wheels 52 depends on the vehicle speed J and is continuous as shown by the broken line (for right steering) 61 to the solid line (for left steering) 62 in FIG. The control device 7 controls the speed or size of the rotation of the motor 8 so as to change to.

The vehicle speed signal J from the vehicle speed sensor 5 is the reference speed range J2 (J1
J2J3: In the case of Fig. 2 J1 = J2 = J3 = 30Km / h), the output shaft 10 of the motor 8 has zero load (no load) when viewed from the output side, as shown in Fig. 4. Is set to the free rotation state. Accordingly, although the ring gear 3 is rotated in the L direction by the rotational force of the interlocking shaft 1 in the G direction, the shaft gear 13 and the first side gear 12 connected to the output shaft 10 via the spur gears 14 and 11 are Because it can be rotated with virtually no load,
The ring gear 3 rotates in the L direction via the bevel gear 16 in the G direction and the bevel gear 17 in the Q direction to rotate the first side gear.
The first side gear 12, the shaft 13 and the spur gear 14 are rotated in the L direction, and the output shaft 10 of the motor 8 is rotated in the M direction. During this time, the return mechanism 22 suppresses movement in the R and S directions, and the gear 18 and the shaft 19 on the rear wheel 52 side that receive a load against the steering from the road surface are not rotated. Therefore, the rear wheels 52 are not steered, are in the neutral position, and substantially two-wheel steering is performed.

Steering in this medium vehicle speed range J = J2 is indicated by reference numeral in FIG.
Corresponding to the region or vehicle speed indicated by II, the steering ratio is zero here.

When the vehicle speed signal J from the vehicle speed sensor 5 is higher than the second reference speed J3, as shown in FIG.
Since the motor 8 is braked to suppress or prevent the rotation of the output shaft 10 of the motor 8, the rotation of the shaft 13 and the side gear 12 connected to the output shaft 10 via the spur gears 14 and 11 is suppressed or prevented. It Therefore, the L direction rotation of the ring gear 3 accompanying the G direction rotation of the interlocking shaft 1 is transmitted to the second side gear 18 via the Q direction rotation of the bevel gear 16 and the G direction rotation of the bevel gear 17, and the side gear 18 and the shaft gear 18. 19 for L
Direction, rotate the rack bar 21 in the S direction,
The rear wheel 52 is steered to the left. That is, when the vehicle 50 is traveling at a high speed, the rear wheels 52 are steered in the same phase as the front wheels 51.
Here, the magnitude of the steering angle or the steering angle ratio is controlled by the control device 7 based on the vehicle speed signal J and the steering angle signal K.

The in-phase steering region of the rear wheels 52 due to a part of the front wheel steering force under the rotational braking control of the motor 8 corresponds to the high vehicle speed region indicated by reference numeral III in FIG. It should be noted that in the high vehicle speed region III, depending on the vehicle speed J, the steering speed or the steering angle ratio of the rear wheels 52 is continuously changed as shown by lines 61 and 62 so that the rotation speed or magnitude of the motor 8 by the control device 7 is changed. Braking control is performed.

Further, in this embodiment, the steering angle ratio between the front wheels 51 and the rear wheels 52 is controlled by using the J signal of the vehicle speed sensor 5 as a parameter to set the rear wheel steering angle in response to the vehicle speed, but the K signal of the steering angle sensor 6 is used. Alternatively, the three-mode sensitive rear wheel steering may be performed using the steering angle or the combined information of the vehicle speed and the steering angle as a parameter.

Further, when a rotor having a coreless structure is used as the motor 8, the magnetic sticking of the magnet attraction is eliminated and the weight is reduced, so that the idling efficiency at the time of non-energization can be increased, and the front wheel steering at the time of non-phase mode can be performed. The load can be lightened.

In the four-wheel steering system 30 according to the embodiment of the present invention described above, since the front wheel steering mechanism and the rear wheel steering mechanism are connected by the differential gear unit 2, the steering system has a simple and compact structure, and the manufacturing cost is low. Not only can be suppressed to a low value, but also by combining with the electric motor control mechanism 7, the vehicle speed sensitive steering angle control can be performed so that the steering angle of the rear wheels 52 is opposite phase, no phase or the same phase. It can be done relatively easily as it varies continuously. Moreover, in the four-wheel steering system 30, since the idling of the motor 8 and the holding braking are used to perform the non-phase or in-phase steering of the rear wheels 52, the power source 60 does not operate normally. Even in some cases, it is possible to enter two-wheel steering in fail safe.

[Brief description of drawings]

FIG. 1 is an explanatory view of a four-wheel steering system according to a preferred embodiment of the present invention, and FIG. 2 is a steering angle of a four-wheel steering system of FIG. FIGS. 3 to 5 show the operation according to the vehicle speed of the steering device shown in FIG. 1 for the case where the vehicle speed is low, medium, and high. FIG. 6 is a detailed operation explanatory view, and FIG. 6 is a sectional explanatory view of a conventionally proposed four-wheel steering system. 1 ... Interlocking shaft, 2 ... Differential gear device, 7 ... Motor control mechanism, 8 ... Motor, 10 ... Output shaft, 11,14 ... Spur gear, 13,19 ... Shaft, 21 ... Rear wheel steering rack bar, 50 …… vehicle, 51 …… front wheel, 52 …… rear wheel.

Claims (1)

[Claims] 1. A front wheel steering mechanism at one end side for transmitting a rotation corresponding to a steering direction and a steering angle of a front gear to a differential gear unit (2) and a ring gear (3) of the front gear. (4) which is connected to the other end and meshes with the ring gear (3) of the differential gear device (2) on the other end side.
Is attached to one of the two side gears (12, 18) of the differential gear unit (2) concentric with the ring gear (3).
A motor (8) having an output shaft (10) connected to 2), and a motor control mechanism (7) for controlling the rotational drive of the motor (8) according to the vehicle speed (J) and the steering direction (K) of the front wheels. , The other side gear (1) is connected to the other side gear (18) of the two side gears (12, 18).
8) The rear wheel steering mechanism (21) that controls the steering direction and steering angle of the rear wheels according to the direction and magnitude of the rotation transmitted to 8), and the return mechanism that returns the rear wheels (52) to the neutral position ( 22), the one side gear (12) and the output shaft (10) of the motor (8) are connected from the one side gear (12) to the motor output shaft (10), and This is performed by a power transmission mechanism (11, 14) capable of transmitting power in both directions from the motor output shaft (10) to the one side gear (12), and the motor control mechanism (7) controls the vehicle speed ( When J) is lower than the given range, the motor (8) is rotationally driven to make the steering phase of the rear wheels (52) opposite to the steering phase of the front wheels (51), and the vehicle speed ( When J) is in the given range, the ring gear (3) is used to prohibit the steering of the rear wheels (52).
When the vehicle speed is higher than the given range, the steering phase of the rear wheels is changed so that the output shaft (10) of the motor (8) idles so that the rotational force applied to the motor (8) is released. A four-wheel steering system for a vehicle configured to apply rotational braking to a motor so as to have the same phase as the steering phase of front wheels.