JPS6025299B2 - car steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steering device for an automobile, and an object of the present invention is to prevent a steering shaft from protruding toward a passenger compartment in the event of an automobile collision, thereby improving safety for occupants.

1 and 2 show a schematic configuration of a conventional steering device and its state at the time of a collision. 1 is a column that supports a steering shaft 6, and 3 is a torque that connects the steering shaft 6 and a gear box 4. with a rod,
The torque rod 3 is connected to the tip of the steering shaft 6 via a cross joint 2' at a crossing angle a.

5 is a steering wheel.

In the above, generally speaking, the intersection angle 0 in the installed state of the steering shaft 6 and the torque rod 3 is usually 24 to 2.
8o, therefore, the cross joint 2 of the conventional device
' is the maximum intersection angle (8max
)30 to 400 are used.

Further, as shown in the figure, the steering shaft 6 is supported by the column 1 up to the vicinity of its tip.
a connection point between the steering shaft 6 and the torque rod 3;
That is, the cross joint 2' is in a state extremely close to the tip of the column 1 (approximately 4 enemies). In order to ensure the safety of occupants in the event of a car collision, automobile safety standards were established in the United States, and subsequently, Japan, Europe, Australia, and other countries have adopted standards that are almost based on the American safety standards. Safety measures are being enacted and put into practice, and among these safety standards is a vehicle speed limit of 30 miles/h (approximately 50 miles/h in metric system).
) is regulated, and in order to satisfy this regulation, the front structure of the vehicle body must be buckled backwards by a predetermined stroke in a frontal collision at a speed of 50 m/h. Increasingly, strategies for absorbing collision energy are becoming commonly adopted.

In the event of a head-on collision at a speed of 50 m/h, the buckling deformation stroke of the front vehicle body structure required to keep the resultant acceleration of the occupants below the upper limit of the above regulations is approximately constant for vehicles with the same structure. Therefore, the amount of rearward displacement of the gear box of the steering device attached to the front structure of the vehicle body during a head-on collision at a vehicle speed of 50 m/h is almost constant for cars of the same structure. This is called the backward displacement allowance.

In the conventional configuration shown in FIG. 1 above, when a collision load of F is applied from the front to the gear box 4 part from the front as shown in FIG. Force r=Fcos(Q+8)・c
os8 and bending direction component force p=Fcos(Q18)・s
in8 works.

However, Q is the inclination angle of the steering shaft 6. In this case, assuming that the amount of protrusion of the steering shaft 6 from the front end support portion of the column 1 is 1', the bending moment of the steering shaft 6 is Fcos(P18)・sina・1'
However, since r is short, no moment that can bend the steering shaft 6 is generated, and the gear box 4 is displaced rearward up to the maximum crossing angle of 8max (approximately 40 degrees) of the cross joint 2'. However, here, the displacement angle from 8 to 8max is about 6 to 12 degrees (corresponding to about 24 to 5 degrees of rearward displacement of the gear box 4), which is not enough to absorb the collision load F, and the subsequent The collision load F is the same as when a saddle directly acts on the cross joint 2' (the cross joint cannot change its angle any further) (the allowable rearward displacement of the gear box 4 x varies depending on the vehicle structure, but is approximately 100~ 200 side), the axial component force r of the steering shaft 6 acts as Fcoso, and the FcosQ is generally larger than the contraction load R of a shock absorbing device (not shown) provided in the steering device ( FcosQ>R), the steering shaft 6 protrudes toward the interior of the vehicle (the amount of protrusion is represented by Y). That is, in a general steering device, in order to absorb the impact force of a so-called secondary collision in which an occupant collides with the steering wheel 5 during a collision, the steering shaft 6 is provided with a shock absorbing device that contracts through plastic deformation or the like and absorbs the collision energy. However, part of the amount of contraction of the shock absorbing device is absorbed by the protrusion of the steering shaft toward the passenger compartment, so that energy when an occupant collides with the steering wheel cannot be sufficiently absorbed.
This will significantly impair the effectiveness of the shock absorbing device, which is originally provided for the purpose of absorbing and mitigating the collision force between the occupant and the steering wheel 5.

The present invention is an attempt to solve the above problem, and as shown in FIG. When a load acts as an axial force on the torque rod 3 through the gearbox 4, the protruding portion at the tip of the steering shaft 6 bends due to the bending force perpendicular to the axial direction of the steering shaft 6, causing the steering shaft 6 to bend in the axial direction. The steering shaft 6 and torque are set such that the force is smaller than the contraction load of the shock absorber.

Maximum intersection angle 8 of cross joint 2 connecting with rod 3
max is configured to a large enough angle to absorb the cross angle change corresponding to the allowable rearward displacement of the gearbox 4 at the time of a collision and the cross angle change due to bending of the protrusion at the tip of the steering shaft 6. It is characterized by: That is, when a collision load of F acts on the gear box 4 as shown in FIG. 4A, torque is generated.

Fcos (Q0a) acts on the steering shaft 6 as a vehicle-induced force of the steering wheel 3. At this time, the bending direction component force p of the steering shaft 6 is Fcos(Q18)・smo,
The axial component force r of the steering shaft 6 is Fcos(Q
+8)・coso, in order to prevent the steering shaft 6 from protruding toward the passenger compartment, the axial component force Fcos(Q18)・coso of the steering shaft 6 must be smaller than the contraction load R of the shock absorber, and the steering Shaft bending moment M=F・lcos(Q18)・sina
is the yield bending stress of the steering shaft 6. It is necessary that x section modulus is larger than Z. That is, Fcos(
Q+0)・cos8SR,. ．． 'a}, F・1・cos
(Q+0). sin820. The condition Z...(b} is required. Eliminate F from the above {phantom, other expressions. Z/1・t
anOSR...The relational expression of [c} is obtained. Note that the shrinkage load R is appropriately set depending on the device. Here is the yield bending stress.
and the section modulus Z is determined from the strength required for torque transmission during steering operation, where 1 is the distance from the tip of the column to the center of the cross joint, a' is the crossing angle of the cross joint in the installed state, and Q is the steering shaft 6. is the inclination angle of In addition, in order to prevent the cross joint 2 from changing its angle up to the maximum intersection angle of 8 max in the event of a collision and to prevent the force of Fcos 8 from acting in the axial direction of the steering shaft 6, the maximum intersection angle of the cross joint 2, 8 max, is set to the allowable rearward displacement of the gear box at the time of a collision. The structure is such that it can absorb the corresponding change in the crossing angle and the change in the crossing angle due to the bending angle 8 of the protruding portion at the tip of the steering shaft 6. From the above, by appropriately setting the above specifications (〇, Z, 1, 8) within the range of the above relational expression {c-, the protrusion from the column end support of the steering shaft to the center of the cross joint can be bent. , which prevents the steering shaft from protruding rearward.

Next, as shown in Figure 4, the intersection angle a' of the cross joint increases from the intersection angle 8 of the cross joint in the installed state to a' as the gear box 4 is displaced rearward at the time of collision, but as the intersection angle a increases, The axial component force r of the steering shaft 6 becomes small, and the rearward displacement of the gear box 4 acts mainly on the steering shaft 6 as a bending load.

According to the experimental results, the vehicle speed is approximately 50 m/h; the length from the tip support of the steering shaft 6 to the connection point with the torque rod is approximately 4 degrees, and the maximum crossing angle of the cross joint is 3.
In a frontal collision with a conventional structure of 9o, the stroke amount of the shock absorber is about 150yanagi, and the protrusion of the steering shaft 6 absorbs about 80ha (1/shaki top). The {c} formula R≧ of the present invention.

Based on Z/1・tana, when 1 is 120 degrees and the maximum crossing angle of cross joint 2 is 95 degrees (other conditions are almost the same as above), there is no rearward protrusion of steering shaft 6, and collision force F is It has been confirmed that it mainly acts in the direction of bending the steering shaft 6. As described above, according to the present invention, the length 1 from the column support at the tip of the steering shaft to the connection point with the torque rod, the yield bending stress 〇, the section modulus Z, and the relationship between the steering shaft and torque rod when the steering device is installed are as follows. Intersection angle 8 is RZOZ/1・tana (R:
The structure is configured so that the protrusion at the tip of the steering shaft can bend due to rearward displacement of the gearbox due to a collision, and the maximum crossing angle of the cross joint is set within the range of the rearward displacement of the gearbox during a collision. By configuring the angle at an angle that can absorb the change in cross angle corresponding to the capacity and the change in cross angle due to bending of the protruding portion at the tip of the steering shaft, the protruding portion at the tip of the steering shaft is not bent by the collision load during a collision. This prevents the operation of the shock absorbing device due to the steering shaft protruding toward the passenger compartment, and when an occupant hits the steering wheel, the impact force can be absorbed through the design value of the shock absorbing device. It can have a great effect on ensuring the safety of cars, and it does not require the addition of any new parts, has a simple structure, and has a low cost, so it can have a great practical effect.

[Brief explanation of drawings]

Figure 1 is a schematic side view showing the conventional configuration, Figure 2
C is an explanatory diagram sequentially showing the state of the object in Fig. 1 at the time of collision; Fig. 3 is a side view showing an embodiment of the present invention; It is an explanatory diagram. 1"""column, 2, 2'...cross joint, 3...
...torque rod, 4...gear box, 5...steering wheel, 6...steering shaft. Figure 2, Figure 4, Figure 4

Claims (1)

[Claims] 1. A steering shaft equipped with a shock absorbing device for occupants is fitted and supported by a column attached to a vehicle body member, and the tip of the steering shaft and one end of a torque rod are connected via a cross joint at an intersection angle of θ. In a steering device in which the other end of the torque rod is connected to a gearbox attached to the front structure of the vehicle body, the yield bending stress σ and section modulus Z of the steering shaft, and the distance l from the tip of the column to the center of the cross joint. R≧ with respect to the shrinkage load R of the shock absorbing device
It is set within the range of σZ/l・tan θ so that the part between the column tip of the steering shaft and the cross joint can bend due to rearward displacement of the gearbox due to a collision, and the maximum crossing angle of the cross joint θmax A steering device for an automobile, characterized in that the angle is configured to absorb a change in the cross angle corresponding to the permissible rearward displacement of the gearbox at the time of a collision and a change in the cross angle due to bending of the steering shaft.