JPS6235946B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a power steering system for a large vehicle, etc.
The present invention relates to a device for limiting steering force.

(Prior art) In a power steering system, the steering output is proportional to the magnitude of the steering resistance acting on the turning vehicle and the steering angle. In fact, if the steering resistance increases significantly, the steering output will also theoretically tend to increase to infinity.

On the other hand, in order to limit the operating range of the power steering device, a suitable stopper has conventionally been generally provided as a steering force limiting device (handle stopper) at the steering limit angle (steering wheel rotation limit angle) or wheel turning limit angle. The operating range is until a part of the steering system comes into contact with this stopper, in other words, the steering angle is limited. Therefore, if the steering operation is restricted at the steering limit, the driver has no choice but to stop the input to the steering wheel at that position. Therefore, at this point, the control valve of the power steering device returns to the neutral position. When the engine returns to normal, the power cylinder stops operating and the steering output is also reduced.

(Problems to be Solved by the Invention) However, with this restriction device, as described above, the steering operation is suddenly restricted at the steering limit, giving the driver a sense of discomfort, resulting in problems with the steering feel. In addition, within the normal steering range, if steering resistance suddenly increases temporarily due to a wheel hitting an obstacle when stationary, the torsion angle of the torsion bar is increased even though the wheels are not actually turned. Since the steering input also increases, the steering output becomes abnormally large. Therefore, in order to cope with such a situation, it is necessary to ensure that the mechanical strength of each component of the steering system is sufficiently large. Even though it is a power steering device, it is designed to handle situations where it is difficult to turn the wheels by operating the steering wheel, even if the steering operation is within the normal range. There is no need to provide sufficient output to survive the situation and the mechanical strength of each component to ensure this output. If it can be restricted, damage to the steering system can be prevented or weight can be reduced by eliminating unnecessary material strength.

The present invention was proposed to solve this problem.

(Means for Solving the Problems) Therefore, the present invention is provided with a control valve that switches according to the input rotation, and selectively supplies pressure oil to the power cylinder connected to the wheel side via the control valve. In the power steering device, a part of the input shaft is inserted into the low pressure passage in the cylindrical screw shaft, and the two are connected by a torsion bar to allow a relative rotation difference. A stopper means is provided between the inner surface and the outer surface of the input shaft so as to come into contact with each other at a predetermined angle, and the other free end of the cylindrical elastic body, which is located on the inner surface of the screw shaft and has one axial end fixed to the screw shaft, is provided. A second engaging means that forms a first engaging means and is capable of engaging with the first engaging means with a certain gap in the shaft rotation direction is inserted into the screw shaft. It is provided on the shaft and is configured to be able to additionally apply an elastic reaction force to the input shaft prior to the stopper means by engaging and abutting the two when the input steering angle of the input shaft reaches a predetermined value.

(Function) By applying an additional elastic reaction force to the input shaft, the driver can sense in advance an input torque that is larger than the normal steering resistance, and prevents the driver from turning too much. Avoid unnecessary high pressure, prevent damage to the steering system, and reduce weight and size.

(Example) The present invention will be explained below with reference to Examples.

To describe the embodiment shown in FIGS. 1 to 5, 1 is a cylinder housing, 2 is a differential mechanism housing, and 3 is an input shaft connected to a handle (not shown). 4 is the sector gear,
The sector gear 4 is connected to a pitman arm of a steering wheel (not shown), and finally the sector gear 4 rotates (output) in proportion to the rotation (input) of the input shaft 3, thereby steering the steering wheel. A piston 5 that meshes with a sector gear 4 is disposed within the cylinder housing 1, and defines working chambers A and B on both sides. A cylindrical screw shaft 6 is threadedly engaged with the inner peripheral surface of the piston 5 via a ball screw assembly, and is connected to a torsion bar 9 by pins 7 and 8.
It is connected to the input shaft 3 via.

A planetary gear mechanism is used as the differential gear mechanism C, and a rotatable disk 10 is sandwiched between the input shaft 3 and the screw shaft 6.
Sun gears 11a and 11b are carved symmetrically, respectively, and a plurality of planet gears 12 mesh with the sun gears 11a and 11b.
a and 12b are arranged symmetrically on both sides of the disk 10 by pins 13. Each planet gear 12a, 1
2b is one ring gear 14 which is similarly engaged with the ring gears 14a and 14b and is rotatably supported.
a is connected to a spool 16 of a control valve 17 via a rod 15, and the other ring gear 14b is fixed to the differential mechanism housing 2. As the spool 16 moves, the control valve 17 connects the current ports P, T, M ₁ , M ₂ as appropriate, and selectively supplies pressure fluid to the working chamber A or B divided within the cylinder housing 1. supply

As shown in FIG. 3, the input shaft 3 loosely inserted into the screw shaft 6 rotates the control valve 1 while twisting the torsion bar 9 according to the input value.
However, in order to prevent the amount of twist from exceeding a certain value, both sides of the input shaft 3 are cut off at a certain angle to form symmetrical side wall parts 22a,
22b, and correspondingly, engagement side walls 23a, 23b are also formed on the inner periphery of the screw shaft 6. When the relative rotational difference between the two reaches a certain value, the side walls 22a, 22b are closed. Engagement side wall 23a,
23b.

Immediately before the side walls 22a, 22b come into contact with the engagement side walls 23a, 23b due to this twisting of the input shaft 3, an elastic steering reaction force other than the torsion bar 9 is applied to the input shaft 3 to grasp the situation exerted on the driver. As is clear from FIGS. 4 and 5, the other free end of the cylindrical elastic body 30, whose one end in the axial direction is connected to the screw shaft 6 by the pin 8, is attached to the tip of the input shaft 3.
When the relative rotational difference between the input shaft 3 and the screw shaft 6 reaches a constant value, the input shaft 3 and the screw shaft 6 engage with each other.

That is, a notch groove 31 (first engagement means) is formed at the tip of the cylindrical elastic body 30 into which the torsion bar 9 is inserted, while a protrusion 32 (second engagement means) is provided at the tip of the input shaft 3. As described above, the side wall portions 22a and 22b are connected to the engaging side wall 23.
They are engaged with each other with a certain gap in the shaft rotation direction so that they come into contact with each other before they come into contact with a and 23b, and when the amount of twist of the torsion bar 9 reaches a certain level, they engage and the steering reaction force is reduced. weight.

When the input shaft 3 is rotated by turning the steering wheel, the sector gear 4 connected to the steering wheel before turning is fixed due to ground resistance, so the piston 5 meshing with the sector gear 4 and the screw shaft 6 is stationary, and one sun gear 1
1b is also fixed like the ring gear 14b.
Therefore, the rotation of the sun gear 11a of the input shaft 3 causes the planet gear 12a to rotate to the disk 1.
The other planet gear 12b connected via 0
Since it cannot revolve, it rotates at that position without revolving, and rotates the ring gear 14a to rotate the spool 16.
to migrate. The control valve 17 switched in this way directs pressure oil from the hydraulic pump to the piston 5.
The fluid is supplied to one of the working chambers A or B, which are partitioned by the same, and at the same time, the other is communicated with the low pressure tank side. In this way, a pressure difference is created between both ends of the piston 5, simultaneously communicating the other end to the lower pressure tank side. In this way, a pressure difference is created between both ends of the piston 5, and at the same time, the rotational force (steering force) of the input shaft 3 is transmitted to the other screw shaft 6 while twisting the torsion bar 9, so that the sun gear 11b is Sun gear 1 with slight phase delay
It starts rotating at the same rotation speed as 1a. therefore,
The planet gear 12a, which had been performing only rotational motion, rotates and revolves in parallel with the other planet gears 12b, and as a result, the ring gear 14a is stopped at that position. In other words, the control valve 17
is maintained in the switched state, and thereafter continues to supply pressure fluid into the working chambers A and B until the input shaft 3 stops.

As the screw shaft 6 rotates, the piston 5 that is engaged with it moves by a pitch proportional amount, but this movement is performed smoothly by the pressure oil supplied to the working chamber A or B. A person can rotate the sector gear 4 with extremely little force and turn the steered wheels. While the input shaft 3 is rotating, the piston 5 is moved and follows the pitch by an amount proportional to the pitch.

When the input shaft 3 is stopped, the sun gear 11a is also stopped, but the other sun gear 11
b rotates by an amount equivalent to the amount of twist applied to the torsion bar 9 and then stops. Since the planet gears 12a and 12b continue to rotate for a short time until they stop, the ring gear 14a, which has been stopped until now, rotates in the opposite direction and stops at the initial position. That is, the ring gear 14a rotates by an amount equivalent to the amount of twist of the torsion bar 9 applied when the input shaft 3 rotates, and the spool 16 also returns to the neutral position accordingly.

However, if the steered wheels hit an obstacle and the vehicle is unable to steer, which tends to happen during such steering operations, for example, when the vehicle is stationary when the vehicle is stopped, unless the situation is known, The driver tries to turn the steering wheel even more strongly due to the increased steering resistance.

When the steering wheel continues to rotate beyond the normal steering range, that is, when the input operation amount (steering angle) increases, the amount of twist of the torsion bar 9 is proportional to this unit input value, so the amount of twist increases. When the notch groove 31 of the cylindrical elastic body 30 and the protrusion 32 of the input shaft 3 become larger and engage with each other, in addition to the torsion reaction force of the torsion bar 9, the notch groove 31 of the cylindrical elastic body 30 and the protrusion 32 of the input shaft 3 engage with each other. In addition to the torsional reaction force of the torsion bar 9, the reaction force that twists the cylindrical elastic body 30 is also fed back to the handlebar side via the input shaft 3, so that the driver is not aware of the normal state. Gives a different feel.

In other words, when it is necessary to apply an input that exceeds the normal range, either the steering wheel has just exceeded the normal steering range and is approaching its steering limit, or the wheels are It can be assumed that the vehicle is in a situation where it is impossible to steer the vehicle, and there is no need to use power to steer the vehicle even in such a state. High pressure may occur, leading to damage to various components and reduced durability, but such conditions can be detected and notified to the driver as a large input torque compared to normal steering resistance. This allows the driver to avoid such a situation.

In addition, when the input shaft 3 is rotated in the opposite direction to the above explanation (rotating counterclockwise in FIGS. 3 and 5), or when the steering wheel approaches its steering limit, Similarly to the above, by applying an elastic reaction force above a predetermined rotation angle of the input shaft, it is possible to make the driver perceive a larger input torque than the normal steering resistance, and a warning signal is generated. can do.

(Effects of the Invention) As explained above, according to the present invention, when the steering input exceeds a certain value and the amount of torsion bar torsion increases significantly, that is, the steering resistance that exceeds the normal operating range acts. In some cases, the driver can be alerted to such a state, and as a result, the driver can prevent the steering output from increasing indefinitely by stopping the steering operation, and the steering system, hydraulic pressure, etc. Damage to the system can be avoided, and there is no need to provide unnecessary material strength to each component, so the overall weight and size can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the present invention, FIG. 2 is a sectional view taken along the line - in FIG. 1, FIG. 3 is a sectional view taken along the line - in FIG. FIG. 5 is a sectional view taken along the line -- in FIG. 4. 3...Input shaft, 5...Piston,
6... Screw shaft, 9... Torsion bar, 17... Control valve, 21... High pressure passage, 2
2a, 22b... side wall portion, 23a, 23b... engaging side wall, 30... cylindrical elastic body, 31... notch groove,
32... Protrusion.

Claims (1)

[Claims] 1. In a power steering device that is equipped with a control valve that switches and operates in response to input rotation, and that selectively supplies pressure oil to a power cylinder connected to a wheel side via the control valve, a cylindrical screw A part of the input shaft is inserted into the low-pressure passage inside the screw shaft, and the two are connected by a torsion bar to allow for a relative rotation difference.A part of the input shaft is inserted at a predetermined angle between the inner surface of the screw shaft and the outer surface of the input shaft. A first engaging means is provided at the other free end of the cylindrical elastic body, which is located on the inner surface of the screw shaft and has one end in the axial direction fixed to the screw shaft, and a first engaging means is provided in the inner surface of the screw shaft. A second engaging means capable of engaging with the first engaging means with a predetermined gap is provided on the input shaft inserted into the screw shaft, and the input steering angle of the input shaft is set to a predetermined value. 1. A steering force limiting device for a power steering device, characterized in that the steering force limiting device for a power steering device is configured to be able to additionally apply an elastic reaction force to the input shaft prior to the stopper means by engaging and abutting the two when reaching the stopper means.