Automatic steering apparatus

For automatic steering control by simultaneously turning a steering shaft and a steering wheel, an apparatus prevents automatic turning torque from being transmitted to the steering wheel when a driver operates the steering wheel and allows the steering wheel to turn freely. A V-shaped recess is formed on the side of the steering wheel, and a ball is provided on the side of the steering shaft. The ball is pushed by a spring toward the steering wheel and positioned within the V-shaped recess during automatic steering to connect the steering wheel with the steering shaft, thereby transmitting the turning torque. When torque which is equal to or exceeding a prescribed value is applied to the steering wheel, the ball is separated from the V-shaped recess to interrupt the transmission of the turning torque, and the steering wheel can be turned freely.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to an automatic steering apparatus, and more 
particularly to steering control when disturbance torque is applied during 
automatic steering. 
2. Description of the Related Art 
Automatic steering apparatuses have been proposed to run a vehicle along a 
desired running line. For example, Japanese Patent Laid-Open Publication 
No. Hei 5-50932 discloses a mechanism which calculates a steering pattern 
for avoiding a collision and turns a steering shaft to run a vehicle 
according to the steering pattern. And, if a driver steers a steering 
wheel to exceed a prescribed angle during the automatic steering, steering 
by the driver is restricted by an electric motor to secure running 
according to the steering pattern. 
Restriction of the driver's steering operation by the electric motor is 
not, however, preferable because a system becomes complicated and the 
driver suffers from an undesired load. Also, when the vehicle is turning 
by the automatic steering, the driver might hold the steering wheel to 
hold his or her position. In such cases, automatic turning of the steering 
wheel is not preferable. 
SUMMARY OF THE INVENTION 
In view of the above disadvantages involved in the related art, this 
invention has been achieved and aims to provide a user-friendly automatic 
steering apparatus which continuously guides a vehicle by automatic 
steering and does not apply an extra load to a driver even when the driver 
intentionally or unintentionally turns the steering wheel during automatic 
steering. 
To achieve the above object, the automatic steering apparatus according to 
this invention comprises turning means for automatically turning a 
steering shaft, and torque control means for interrupting the transmission 
of automatic turning torque to a steering wheel when torque equal to or 
exceeding a prescribed value other than the automatic turning torque is 
applied to the steering wheel during automatic turning. One aspect of the 
torque control means comprises a ball which is provided on one side of the 
steering shaft and the steering wheel, an elastic member for pushing the 
ball toward the other side, and a recess which is provided on the other 
side to fit to the ball; the ball is fitted into the recess to transmit 
the automatic turning torque from the steering shaft to the steering 
wheel, and the ball is separated from the recess when torque equal to or 
exceeding a prescribed value other than the automatic turning torque is 
applied to the steering wheel. 
The automatic steering apparatus according to this invention further 
comprises a first disk provided at the leading end of the steering shaft, 
and a second disk provided on the back of the steering wheel to oppose the 
first disk; the first disk is provided with projections and the second 
disk is provided with grooves to oppose the projections. The projections 
and the grooves are mutually engaged for manual steering to integrally 
turn the first disk and the second disk, and the projections are separated 
from the grooves for automatic steering. 
Another aspect of the automatic steering apparatus according to this 
invention further comprises electromagnetic drive means which are 
connected to the ball to push it against said recess; the electromagnetic 
drive means do not operate during automatic steering and the ball is 
pushed by the elastic member. The electromagnetic drive means operate 
during the manual driving and the ball is pushed against the recess by the 
electromagnetic drive means. 
Further, the automatic steering apparatus according to this invention 
comprises an automatic steering mechanism for turning the steering shaft, 
a clutch which connects the steering shaft with the steering wheel during 
manual turning and releases the steering shaft from the steering wheel 
during automatic steering, and a sub-clutch which connects the steering 
shaft with the steering wheel by a given elastic force during the 
automatic steering. One aspect of the sub-clutch comprises a spring which 
is provided on the side of the steering shaft, a ball which is connected 
to the spring and pushed toward the steering wheel, and a recess which is 
provided on the side of the steering wheel and receives the ball.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Embodiments of the invention will be described with reference to the 
accompanying drawings. 
First embodiment: 
The automatic turning mechanism of this embodiment is the same as a 
conventional unit and has a gear at the bottom end of a steering shaft 
which is turned by an electric motor to automatically turn the steering 
shaft. On the other hand, the steering wheel and the steering shaft are, 
unlike the conventional units, not mutually fixed and are structured so as 
to connect or separate as required. 
FIGS. 1A and 1B show a connected state of the steering shaft and the 
steering wheel. FIG. 1A shows a general structure in which a steering 
wheel 10 and a steering shaft 12 have disks 14 and 16 respectively, the 
disk 14 on the side of the steering wheel 10 has grooves 15, and the disk 
16 on the side of the steering shaft 12 has projections 17. The grooves 15 
and the projections 17 form a clutch. When a vehicle runs in manual drive, 
an actuator 24 moves the disk 16 in the direction of a to engage the 
projections 17 of the disk 16 with the grooves 15 of the disk 14, so that 
the steering wheel 10 and the steering shaft 12 are coupled. Thus, in the 
manual drive, steering operation by the driver is directly transmitted to 
the steering shaft 12 to control the vehicle as the driver desires. 
FIG. 2 shows a layout of the grooves 15 and the projections 17 in a 
schematic form. The grooves 15 are provided in the quantity of four each 
at an angle of 90 degrees with respect to the center of the disk 14, and 
the projections 17 are provided on the disk 16 in the quantity of four to 
oppose the four grooves 15. The grooves 15 and the projections 17 are 
mutually engaged to operate as a clutch. The number of the grooves 15 and 
the projections 17 may be less than four and can be formed in the number 
of more than four if necessary. Also, a V-shaped recess 18 is formed at 
the edge of the disk 14, and a ball 20 and a spring 22 for pushing the 
ball 20 toward the V-shaped recess 18 are provided on the disk 16 to 
oppose the V-shaped recess 18. The V-shaped recess 18, the ball 20 and the 
spring 22 function as a sub-clutch, and their engaged state will be 
described afterward. 
When the vehicle runs by automatic steering, the actuator 24 moves the disk 
16 in the direction of b to separate the projections 17 from the grooves 
15 as shown in FIG. 1A. The steering wheel 10 and the steering shaft 12 
are mutually connected by the sub-clutch or torque control means denoted 
by f in FIG. 1A. 
FIG. 1B shows an expanded view of the torque control means. As described 
above, the V-shaped recess 18 is formed on the side of the steering wheel 
10, and the ball 20 which is pushed by the spring 22 toward the steering 
wheel 10 is provided on the side of the steering shaft 12. When the ball 
20 is positioned in the V-shaped recess 18, a force to hold the ball 20 in 
the V-shaped recess 18 is applied by the spring 22, so that the steering 
wheel 10 and the steering shaft 12 are connected by means of the ball 20, 
and the steering wheel 10 is turned together with the steering shaft 12 by 
turning torque of the steering shaft 12. A connection force depends on an 
elastic force of the spring 22 and can be varied by varying the elastic 
force. 
Thus, in the automatic steering mode, the turning torque of the steering 
shaft 12 is transmitted to the steering wheel 10 by the engagement of the 
V-shaped recess 18 and the ball 20. And, the driver can easily know that 
the automatic steering is in progress because the steering wheel 10 is 
automatically turned. And, even when small disturbance torque is applied 
to the steering wheel 10, the steering wheel 10 can be turned continuously 
because the ball 20 is kept positioned in the V-shaped recess 18 by virtue 
of the pushing force of the spring 22. 
If the driver intentionally or unintentionally operates the steering wheel 
10 during automatic steering mode and torque equal to or exceeding a 
prescribed value is applied to the steering wheel 10, the ball 20 is 
separated from the V-shaped recess 18, despite the pushing force of the 
spring 22. Then, the ball 20 rolls on the flat face of the disk 14 so the 
automatic turning torque of the steering shaft 12 is not transmitted to 
the steering wheel 10, and the steering wheel 10 can be turned freely. In 
such a situation, the automatic steering is still continued because the 
steering shaft 12 itself is turned as desired by the turning mechanism. 
FIG. 3 shows a flowchart of the operation in this embodiment. First, it is 
judged whether or not the vehicle is in auto-drive (the automatic steering 
mode) (S101). When it is judged that the vehicle is in auto-drive, it is 
judged whether or not the driver has input a demand for shifting to manual 
drive (S102). This judgment is made by checking the operation of a 
manual/auto changeover switch provided near the driver's seat. When the 
driver does not operate a manual shifting switch and desires to continue 
the automatic steering, the actuator 24 moves the disk 16 (or the clutch) 
to the position b to separate the projections 17 of the disk 16 from the 
grooves 15 of the disk 14 and connects the steering wheel 10 and the 
steering shaft 12 by the ball 20 (S106). It has been described above that 
if torque equal to or exceeding the prescribed value is applied in this 
state, the ball 20 is separated from the V-shaped recess 18 and the 
turning torque of the steering shaft 12 is not transmitted to the steering 
wheel 10. 
When the driver demands a shift from auto-drive to manual drive, it is 
judged whether or not a switch within the V-shaped recess 18 is turned ON 
(S103). The V-shaped recess switch is denoted by reference numeral 26 in 
FIG. 1B. When the ball 20 is positioned in the V-shaped recess 18, the 
V-shaped recess switch 26 is pushed upward in FIG. 1B, closing a contact 
and turning the switch ON. Thus, when the V-shaped recess switch 26 is 
OFF, the ball 20 is not positioned within the V-shaped recess 18, so that 
the driver is instructed by a displayed message or voice message to turn 
the steering wheel 10 to enter the ball 20 into the V-shaped recess 18 
(S107). This instruction is given to match the turning position of the 
steering wheel 10 with that of the steering shaft 12. If they do not 
match, when the automatic steering is shifted to the manual operation, a 
steering amount of the vehicle does not agree with a steering operating 
amount, and the manual drive cannot be made smoothly (this is called 
steering angle synchronization). When the driver turns the steering wheel 
10 according to an instruction to align the V-shaped recess 18 and the 
ball 20 and the ball 20 enters the V-shaped recess 18, the V-shaped recess 
switch 26 is turned ON. And, when it is detected that the switch 26 has 
been turned ON, the actuator 24 moves the disk 16 to the position a to 
engage the grooves 15 with the projections 17 (S104). Thus, the steering 
wheel 10 and the steering shaft 12 are connected to shift to manual drive, 
and the driver can control the vehicle by operating the steering wheel 10 
(S105). 
In the above embodiment, if the ball 20 is not in the V-shaped recess 18 
when the shift to the manual drive is demanded, the driver is instructed 
to operate the steering wheel 10 to synchronize the steering angles, 
though this process can be automated. 
FIG. 4 shows a processing flowchart for automatically synchronizing the 
steering angles. In the same way as the process shown in FIG. 3, it is 
first judged whether or not the vehicle is in auto-drive (S201). When it 
is judged that the vehicle is in auto-drive, it is next judged whether or 
not the driver has input a demand for shifting to the manual drive (S202). 
When the driver does not operate the manual shifting switch and desires to 
continue automatic steering, the actuator 24 moves the disk 16 (or the 
clutch) to the position b to separate the projections 17 of the disk 16 
from the grooves 15 of the disk 14 and connects the steering wheel 10 and 
the steering shaft 12 by the ball 20 (S207). As described above, if torque 
equal to or exceeding a prescribed value is applied in this state, the 
ball 20 is separated from the V-shaped recess 18 and the turning torque of 
the steering shaft 12 is not transmitted to the steering wheel 10. When 
the driver demands shifting from auto-drive to the manual drive, it is 
judged whether or not the switch within the V-shaped recess 18 has been 
turned ON (S203). And, when the V-shaped recess switch 26 has not been 
turned ON, the process is different from the one shown in FIG. 3, and a 
motor mounted on the steering wheel 10 is run to align the position of the 
V-shaped recess 18 with that of the ball 20 (S208). When the ball 20 
enters the V-shaped recess 18, the V-shaped recess switch 26 is turned ON 
as described above, and the motor which has detected the ON signal stops 
running (S204), then the actuator 24 moves the disk 16 (or the clutch) to 
the position a to shift to the manual drive (S205, S206). Thus, since the 
driver simply operates the manual shifting switch to perform the steering 
angle synchronization automatically, the operating load on the driver can 
be reduced. 
When the ball 20 is entered into the V-shaped recess 18 by running the 
motor, it is preferable that the motor is stopped and a message of the 
completion of the steering angle synchronization is given to the driver. 
Thus, the driver can make sure that a shift to the manual drive can be 
made. 
Second embodiment: 
In the first embodiment described above, the disks 14, 16 had respective 
grooves 15 and projections 17 to form the clutch. But, the disk 14 and the 
disk 16 can be formed flat without any projection or groove and the ball 
20 can be pushed firmly into the V-shaped recess 18 to connect the 
steering wheel 10 and the steering shaft 12. Such a structure is shown in 
FIGS. 5A, 5B. 
In FIG. 5A, the disk 14 and the disk 16 are flat and do not have grooves 15 
or projections 17 which are shown in FIGS. 1A, 1B. Torque control means 
denoted by g in FIG. 5A include an electromagnetic coil 28, a plunger 30 
and a spring 32 which are provided as a clutch in the disk 16, in addition 
to the V-shaped recess 18, the ball 20 and the spring 22. 
FIG. 5B is an expanded view of the torque control means g shown in FIG. 5A. 
In the same way as in FIGS. 1A, 1B, the ball 20 is pushed by the spring 22 
toward the V-shaped recess 18. In addition, the plunger 30 is provided 
below the ball 20 and pushed by the spring 32 toward the ball 20. The 
electromagnetic coil 28 is provided around the plunger 30, and the plunger 
30 can be pushed downward despite an elastic force of the spring 32 by 
flowing a current through the electromagnetic coil 28. In a state that no 
current is run through the electromagnetic coil 28, the plunger 30 is 
pushed upward by the elastic force of the spring 32, and the ball 20 is 
firmly pushed against the V-shaped recess 18. The pushing force of the 
plunger 30 against the ball 20 serves as a force for connecting the 
steering wheel 10 and the steering shaft 12, so that the steering wheel 10 
and the steering shaft 12 are turned together during manual drive. 
During automatic steering, on the other hand, a current is sent through the 
electromagnetic coil 28, and the plunger 30 is pushed downward against the 
elastic force of the spring 32. Thus, the ball 20 is positioned in the 
V-shaped recess 18 by the elastic force alone of the spring 20 in the same 
way as in the first embodiment, and separated from the V-shaped recess 18 
when torque equal to or exceeding a prescribed value is applied to the 
steering wheel 10, thereby allowing the steering wheel 10 to turn freely. 
FIG. 6 shows shapes of the disk 14 and the disk 16 in schematic form. By 
comparing with the shapes in the first embodiment shown in FIG. 2, it is 
apparent that these disks 14, 16 are different from those shown in FIG. 2. 
Specifically, these disks 14, 16 do not have the grooves 15 and the 
projections 17 which are shown in FIG. 2 but have V-shaped recess 18 and a 
ball 20 provided at mutually opposed positions. Also, the ball 20 is 
firmly pushed by an elastic force toward the V-shaped recess 18 to couple 
the disk 14 and the disk 16. Thus, the ball 20 functions as a clutch, and 
the steering wheel 10 can be freely turned when torque equal to or 
exceeding a prescribed value is applied during automatic steering. It is 
to be understood that to shift from automatic steering to manual steering 
in this embodiment, the driver must request alignment of the V-shaped 
recess 18 with the ball 20 or the steering wheel 10 is turned by the motor 
to synchronize the steering angles. 
In the above embodiments, the V-shaped recess 18 and the ball 20 were 
provided in the quantity of one respectively but can be provided in 
multiple numbers as required, and may be provided at positions to oppose 
at an angle of 180 degrees. 
In the above embodiments, when torque equal to or exceeding a prescribed 
value is applied to the steering wheel 10, the engagement of the V-shaped 
recess 18 and the ball 20 was released to allow the steering wheel 10 to 
turn freely. But, when the vehicle is provided with another sensor and an 
emergency situation of the vehicle is detected by this sensor, the 
steering operation by the driver during the automatic steering is judged 
to cope with the emergency situation. In such a case, the ball 20 is fixed 
in the V-shaped recess 18 to firmly couple the steering wheel 10 with the 
steering shaft 12, the automatic steering control is released, and the 
driver can then operate the steering wheel 10 with priority. To fix the 
ball 20 within the V-shaped recess 18, for example, the current flow 
through the electromagnetic coil 28 may be stopped to firmly push the ball 
20 into the V-shaped recess 18 by the plunger 30 in FIGS. 5A, 5B. 
Also, in the above embodiments, the V-shaped recess was provided on the 
side of the steering wheel and the ball on the side of the steering shaft, 
but the ball can be provided on the side of the steering wheel and the 
V-shaped recess on the side of the steering shaft. However, since the ball 
and the mechanism for pushing the ball are relatively complicated, the 
ball is preferably provided on the steering shaft. 
While there have been described that what are at present considered to be 
preferred embodiments of the invention, it is to be understood that 
various modifications may be made thereto, and it is intended that the 
appended claims cover all such modifications as fall within the true 
spirit and scope of the invention.