JPH0344033B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a four-wheel steering system for a vehicle.

[Prior art] In a vehicle such as an automobile, the rear wheels are steered along with the front wheels as the steering wheel is turned.4
Wheel steering systems are well known. In such a four-wheel steering system, the required characteristics of the rear wheel steering ratio, that is, the ratio of the rear wheel steering angle to the steering angle of the steering wheel, differ depending on the vehicle speed, etc. A vehicle equipped with a steering ratio changing device that changes the steering ratio of the rear wheels accordingly has been proposed (see Japanese Patent Laid-Open No. 59-26365).

The above-mentioned steering ratio changing device is a mechanical device interposed between the front wheel steering mechanism and the rear wheel steering mechanism linked to the steering mechanism, and is driven by a motor to change the steering ratio of the rear wheels. It is subject to change.
This configuration has the advantage that responsiveness to changes in vehicle speed and the like is increased and the steering ratio can be accurately controlled.

However, in the above steering ratio changing device,
If a failure occurs in the motor, electrical system, etc., the steering ratio will not be adjusted properly, which may disturb the steering feel of the driver and, in some cases, pose a risk of an accident.

In order to solve this problem, the above-mentioned Japanese Patent Application Laid-Open No.
According to Japanese Patent No. 26365, the above problem is solved by providing a steering ratio sensor that monitors the control state of the steering ratio and feeding back the signal of the sensor.
By the way, the four-wheel steering system requires responsiveness, especially in the medium and high speed range.

However, as mentioned above, there is a problem that constant feedback control reduces responsiveness, and to solve this problem, the motor has been designed to have multiple electromagnetic phases so that open control can be performed depending on the driving condition. It is conceivable to configure the motor with a stepped motor to ensure responsiveness.

However, when configured with a step motor,
Even if one of the multiple electromagnetic phases is disconnected, the motor will operate normally if the required torque is small, so even if a steering ratio sensor is installed as described above, failures can be detected early. There was a problem that I couldn't do it.

[Object of the Invention] In view of the above problems, the present invention provides a four-wheel steering system equipped with a steering ratio changing device including a motor as a drive source, in which a step motor is used as the motor as the drive source. In addition to ensuring good responsiveness, if an abnormality occurs in the motor itself or the motor drive source, it can be quickly detected.
The purpose is to increase the safety of wheel steering devices.

[Structure of the Invention] Therefore, the present invention employs a step motor as the motor for driving the steering ratio changing device, and also includes an abnormality detection method for monitoring whether or not the motor is normal in light of a control signal. The present invention is characterized in that it includes a steering ratio detecting means and a steering ratio detecting means for detecting the operating state of the steering ratio changing device.

[Effects of the Invention] According to the present invention, since a step motor is used, responsiveness can be ensured, and since failures are monitored by illuminating the control signals sent to the electromagnetic phases, even if one phase fails, it is possible to ensure responsiveness. Failures can be detected early. Furthermore, even if the motor is normal but the steering ratio changing device is out of order, or if a large load is generated on the rear wheels and the step motor loses synchronization, the abnormality detection means will still output normally, so it will be possible to detect the failure. Although it is difficult to determine, this malfunction and step-out can be reliably detected using the steering ratio sensor, thereby improving safety.

[Example] Next, an example of the present invention will be described based on the accompanying drawings.

As shown in FIG. 2, a steering mechanism A having a handle 1 is linked to a front wheel steering mechanism B that steers left and right front wheels 2R, 2L, and the front wheel steering mechanism B includes a long intermediate rod 3, a handle 1 Linked to a rear wheel steering mechanism E having a hydraulic power steering mechanism D via a steering ratio changing device C that changes the steering ratio of the left and right rear wheels 4R, 4L with respect to the steering angle of the vehicle and a bent control rod 5. has been done. By steering the steering wheel 1, the front wheels 2R, 2L are always steered at a constant steering ratio relative to the steering angle of the steering wheel 1, and the rear wheels 4R, 4L are controlled based on the vehicle speed signal from the vehicle speed sensor 6. The vehicle is steered at a steering ratio according to the vehicle speed calculated by means F.

That is, the front wheel steering mechanism B has a rack 10 that meshes with a pinion 8 provided at the lower end of the steering shaft 7 of the steering mechanism A, and
The relay rod 11 is moved laterally by the rotation of the relay rod 11, the knuckle arms 12R, 12L that support the front wheels 2R, 2L,
12L and both ends of the relay rod 11 are rotatably connected, and as the relay rod 11 is displaced, the front wheel 2
Tie rods 13R and 13L that steer R and 2L
It is composed of.

A pinion 14 is fixed to the front end of the intermediate rod 3, and the pinion 14 meshes with a rack 15 provided on the relay rod 11 to rotate the intermediate rod 3 in the same direction as the handle 1.
The steering ratio changing device C is configured to laterally displace the control rod 5 by a predetermined amount in accordance with the rotation angle of the intermediate rod 3, that is, the steering angle of the steering wheel 1, and the vehicle speed.

The rear wheel steering mechanism E includes a relay rod 16 that is laterally displaced integrally with the control rod 5;
Knuckle arm 17 that supports rear wheels 4R and 4L
R, 17L and the knuckle arms 17R, 17L
It consists of tie rods 18R and 18L which are rotatably connected to both ends of the relay rod 16.

The power steering mechanism D includes a power cylinder 20 that fits into the relay rod 16, is fixed to the relay rod 16 within the power cylinder 20, and has two hydraulic chambers 22,
A piston 21 divided into 23 sections, a control valve 24 that can be switched by the displacement of the control rod 5, a supply pipe 26, a control valve 24, and a control valve 24 for supplying oil in a reservoir tank 25.
An oil pump 2 that supplies oil to either hydraulic chamber 22 or 23 in the power cylinder 20 via 7 or 28.
9, and in addition, control valve 2
4 and a drain pipe 30 that communicates with the reservoir tank 25.
is provided.

The control valve 24 is connected to the supply pipe 26 and the pipe 2 when the control rod 5 is displaced to the right.
8. Connect the drain pipe 30 and the pipe 27, respectively, and when the control rod 5 moves to the left, the supply pipe 26 and the pipe 27, and the drain pipe 30 and the pipe 28
The pistons 21 are driven in the same direction as the control rod 5 by the hydraulic pressure of the oil pump 29 to assist in steering the rear wheels 4R and 4L. 31, 31 are springs that urge the piston 21 to the neutral position.

The control means F includes rear wheels 4R and 4 according to the vehicle speed.
The steering ratio of L, that is, the ratio of the steering angle of the rear wheels 4R, 4L to the steering angle of the steering wheel 1 is set in advance. That is, as shown in FIG. 7, first, in a low speed range, a negative steering ratio is set whose absolute value gradually decreases as the speed increases. Therefore, in a low speed range, for example, when the steering wheel 1 is turned to the right and the relay rod 11 of the front wheel steering mechanism B is displaced to the left, the steering ratio changing device C changes the control rod based on the signal from the control means F. 5 to the right, rear wheel 4
This means that R and 4L are steered to the left, that is, in the opposite phase to the direction of rotation of the steering wheel 1.

Furthermore, since the steering ratio approaches zero in the medium speed range, even if the steering wheel 1 is turned, the rear wheels 4R and 4L are not steered, resulting in essentially two-wheel steering.

Furthermore, in the high speed range, the steering ratio is positive, so
The steering ratio changing device C displaces the control rod 5 in the same direction (same phase) as the relay rod 11 of the front wheel steering device B. Note that 32 is a power source (battery), and 33 is an ignition switch.

Next, the structure of the steering ratio changing device C will be explained in detail.

As shown in FIG. 3, the steering ratio changing device C transmits the steering angle of the steering wheel 1 to a connecting rod 35 whose one end is connected to the control rod 5 via a ball joint 34. It has a steering angle transmitting section C1 that rotates the rod 35 by a predetermined angle corresponding to the steering angle of the steering wheel around the central axis _l1 of the control rod 5 using the ball joint 34 as a fulcrum, and a stepping motor 36 for driving. , the steering ratio changing lever 38 connected to the other end of the connecting rod 35 via the ball joint 37 is rotated around an axis _l2 perpendicular to the central axis _l1 of the control rod 5 in accordance with the vehicle speed. and a steering ratio changing section C2 that changes the steering ratio of the rear wheels 4R and 4L.
The detailed operating principle will be described later, but the rotation angle of the connecting rod 35, that is, the ball joint 37, around the axis _l1 corresponding to the steering angle of the steering wheel, and the steering ratio around the axis _l2 , which is controlled according to the vehicle speed. The control rod 5 is laterally displaced by a predetermined stroke in accordance with the rotation angle of the change lever 38.
In this embodiment, the stepping motor 36
Or an abnormality detection circuit 41 that can immediately detect a failure in the drive unit 40 or the like.
(FIG. 1) is built into the control means F.
This abnormality detection circuit 41 constitutes an abnormality detection means according to the present invention, and will be described in detail later. Reference numeral 39 designates a length adjustment portion of the connecting rod 35.

The steering angle transmission section C1 is connected to the control rod 5.
The rod 44 is supported by the vehicle body G coaxially with the center axis _l1 of the rod 44, and the bevel gear 42 at the tip is meshed with the bevel gear 43 at the rear end of the intermediate rod 3, and can freely slide on the vertical boss portion 45 of the rod 44. The steering angle transmission shaft 46 is rotatably and slidably connected to the connecting rod 35 via a spherical joint 47.

On the other hand, the steering ratio changing section C2 is provided with a stepping motor 36 for driving, a driving gear 49 fixed to an output shaft 48 of the stepping motor 36, and a sector gear 50 meshed with the driving gear 49. and a rotating shaft 52 of the arm 51.
is supported by the vehicle body G, and as shown in FIG. 4, springs 53, 53 are stretched between the arm 51 and the vehicle body G to bias the arm 51 to the neutral position. Further, stopper surfaces 54, 54 for regulating the swing angle of the arm 51 are formed on the vehicle body G.

Returning to FIG. 3, a U-shaped holder 55 is fixed to the rotation shaft 52, a pin 56 integrated with the steering ratio change lever 38 is pivotally attached to the holder 55, and a rotation A steering ratio sensor 57 is disposed on the small diameter portion of the shaft 52 to detect the rotation angle of the steering ratio change lever 38, that is, the steering ratio of the rear wheels 4R and 4L. This steering ratio sensor 57 constitutes steering ratio detection means according to the present invention.

Here, the operating principle of the steering ratio changing device CB will be explained based on FIGS. 8 and 9.

That is, as shown by the solid line O in FIG.
When l ₃ is facing in the direction that coincides with the central axis l ₁ of control rod 5, even if ball joint 37 is rotated by angle θ from reference position P by steering handle 1, the control rod will not move. 5 is not displaced in the lateral direction, and therefore the steering ratio of the rear wheels 4R and 4L is zero.

On the other hand, when the center line l ₃ of the pin 56 is inclined at an angle α with respect to the central axis l ₁ of the control rod 5, the rotation angle θ about the axis l ₃ of the ball joint 37 is controlled. Rod 5 is S=rtanαsinθ
, and the rear wheels 4R and 4L are steered at a predetermined steering ratio. Note that r is the distance between the ball joints 37 of the axis _l3 .

Next, the stepping motor 36 and its drive section 4
Let's explain about 0.

As shown in FIG. 5, the stepping motor 36 has four
The iron core portions 60, 60, .
Each phase coil 61, 61, . . . is wound thereon, and a rotor 62 magnetized to the S pole is fixed on the output shaft 48.

A plurality of convex portions 63, 6 are provided on the outer circumference of the rotor 62.
3, . . . are formed, and the spacing between the convex portions 63, 63, . . . is set smaller than the spacing between the iron core portions 60, 60, . By sequentially exciting each phase to the N pole or S pole, the rotor 62 can be rotated in a desired direction at a constant step angle, and by passing a holding current through the coil 61 of any one phase,
The rotor 62 can be locked at a predetermined angular position.

Next, control of the stepping motor 36 will be explained.

As shown in FIG. 1, the control means F includes the vehicle speed sensor 6.
An excitation signal for each phase is transmitted to the motor drive section 40 based on the vehicle speed signal from the motor drive section 40, and the motor drive section 40 rotates the output shaft 48 of the stepping motor 36 by a predetermined number of steps in a predetermined direction based on the excitation signal. At the same time, the output shaft 48 is locked at a predetermined angular position.

Further, in the motor driving section 40, it is detected whether each phase is excited in accordance with the excitation signal, and this is fed back to the control means F as a monitoring signal for each phase.

Then, within the control means F, the abnormality detection circuit 41 compares the excitation signal with the monitoring signal, and if there is a coil 61 that is not excited even though the excitation signal is being transmitted, the power supply 32 and the motor are immediately activated. The electromagnetic switch 64 between the drive parts 40 is turned off, and the driving of the stepping motor 36 is stopped.
When the electromagnetic switch 64 is turned off, the steering ratio change lever 38 is returned to the neutral position by the springs 53, 53 shown in FIG. 4, and thereafter, the steering of the rear wheels 4R, 4L is stopped. At this time, it is preferable to configure the system so that the failure of the stepping motor 36 is notified to the driver using a buzzer, a lamp, etc. provided on the instrument panel.

In this way, in this embodiment, the motor drive unit 40
When an abnormality is detected, the steering ratio change lever 38
Since the steering ratio changing device C is immediately returned to the neutral position, the safety of a vehicle equipped with this type of steering ratio changing device C can be improved.

Next, the circuit configuration of the motor drive section 40 will be explained.

As shown in FIG. 6, the motor drive unit 40 includes switching transistors Tr1 to Tr4 that turn on and off the excitation of each phase.
One end of the coil 61 of each phase is connected to the collectors of Tr1 to Tr4, the emitters are grounded, and the excitation signal is supplied to the base. Moreover, the other end of the coil 61 of each phase is connected to the power supply 32.
and each transistor Tr1 to Tr
A diode 65 and a resistor 66 are provided in parallel with the coil 61 between the coil 61 and the power source 32, and a resistor 67 is provided between the coil 61 and the ground between the transistors Tr1 to Tr.
It is inserted in parallel with 4.

Therefore, for example, when an excitation signal is supplied to Tr1, Tr1 is turned on, current flows from the power supply 32 to the ground via the A-phase coil 61 and the transistor Tr1, and the A-phase coil 61 is excited. At this time, a low-level signal L is output as the A-phase monitoring signal. On the other hand, when the excitation signal is not supplied to Tr1, the A phase is not excited and a high level signal H is output as the A phase monitoring signal. Note that excitation of each phase other than the A phase is turned on and off in the same manner.

Then, by comparing the above-mentioned excitation signal and the monitoring signal, it is possible to determine whether there is an abnormality in the motor drive unit 40 as described below. Here, the A-phase abnormality will be described as a representative example.

() When the A-phase monitoring signal is H even though the excitation signal is supplied to Tr1.

In this case, it can be determined that Tr1 is open (faulty).

() When the A-phase monitoring signal is L even though the excitation signal is not supplied to Tr1.

In this case, it can be determined that a problem has occurred, such as a disconnection of the A-phase coil 61, a disconnection of the coupler (not shown) connecting the motor drive section 40 and the power source 32, or a short circuit (failure) of Tr1.

If the above-mentioned abnormality () or () is detected, the driving of the stepping motor 36 is stopped as described above.

It goes without saying that the present invention is not limited to the above embodiments, and that various design changes can be made within the framework of the claims.
For example, the steering ratio of the rear wheels 4R and 4L may be changed in response to the lateral acceleration of the vehicle, the front wheel steering angle, etc., or may be effected by a changeover switch provided on the instrument panel. Further, the present invention can also be applied to a four-wheel steering system configured such that the rear wheel steering mechanism is electronically controlled via a steering ratio changing device independently of the front wheel steering mechanism.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the procedure for changing the steering ratio of the rear wheels and detecting abnormalities in the motor, Figure 2 is an explanatory diagram showing the overall configuration of the four-wheel steering system, and Figure 3 is the details of the steering ratio changing system. Explanatory drawings, Fig. 4 is a - arrow view of Fig. 3, Fig. 5 is an explanatory drawing showing the internal structure of the motor, Fig. 6 is a circuit diagram of the motor drive section, Fig. 7 is a steering angle of the steering wheel and rear wheel rotation. The diagrams illustrating the relationship with the steering angle, FIGS. 8 and 9, are diagrams of the operating principle of the steering ratio changing device. A... Steering mechanism, B... Front wheel steering mechanism, C... Steering ratio changing device, E... Rear wheel steering mechanism, 36... Stepping motor (motor), 4
1... Abnormality detection circuit (abnormality detection means).

Claims (1)

[Scope of Claims] 1. A four-wheel steering device for a vehicle equipped with a steering change device that changes a steering ratio of rear wheels with respect to a steering angle, wherein the steering ratio change device uses a step motor as a drive means. and a steering ratio detecting means for detecting the operating state of the steering ratio changing device. A four-wheel steering system for vehicles that