JPS6114989B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a power steering system for a large vehicle, etc.
The present invention relates to a device for limiting steering force.

In a power steering system, the steering output is proportional to the magnitude of the steering resistance acting on the turning wheels and the steering angle. If the steering resistance increases significantly, the steering output would theoretically 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 control device (handle stopper) at the steering control angle (steering wheel rotation limit angle) or wheel turning limit angle. The operating range was until a part of the steering system came into contact with this stopper, in other words, the steering angle was limited. For this reason, the driver feels a sense of discomfort as the steering operation is suddenly restricted at the steering limit, and if the steering operation is restricted, the driver has no choice but to stop inputting to the steering wheel at that position, which reduces the power output. The control valve of the steering gear is returned to the neutral position, the power cylinder stops operating, and the steering output is also reduced.

However, with this limiting device, even within the normal steering operation range as described above, when the steering resistance suddenly increases, the torsion angle of the torsion bar is reduced even though the wheels are not actually turned. Furthermore, 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 increase the mechanical strength of each component of the steering system in advance. Even though it is a power steering device, even within the normal steering operation range, the wheel hits an obstacle and it is difficult to turn the wheel by operating the steering wheel. There is no need to provide sufficient output and the mechanical strength of each component to secure this output.If the steering output could be reliably limited in such a case, it would be possible to prevent damage to the steering system or prevent damage to the steering system. It is possible to reduce the weight by omitting the required material strength.

The present invention was proposed to solve this problem, and when the steering resistance increases abnormally during steering, the pressure oil to be supplied to the output drive unit such as the power cylinder is released to the tank side. This prevents unnecessary high pressure from being generated in the hydraulic system, and allows the driver to sense a larger input torque than normal steering resistance, thereby preventing damage to the steering system, reducing weight, and
It is an object of the present invention to provide a steering force limiting device for a power steering device that is designed to be downsized.

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

Regarding the embodiment shown in FIGS. 1 and 2, 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 a sector gear, and the steering wheel (not shown) is connected to the pitman arm.Finally, the sector gear 4 rotates (output) in proportion to the rotation (input) of the input shaft 3, and steers the steering wheel. do. 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 screwed into the inner peripheral surface of the piston 5 via a ball screw assembly,
It is connected to the input shaft 3 via a torsion bar 9 by pins 7 and 8.

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 appropriately connects the annular ports P, T, M ₁ and M ₂ and selectively supplies pressure fluid to the working chamber A or B defined within the cylinder housing 1. supply to.

Next, an annular groove 20 is cut into the sliding surface of the housing 2 and the screw shaft 6, which is located at a portion where the input shaft 3 and the screw shaft 6 overlap. 20 is communicated with the pump port P via a passage 21 so that high pressure oil from the control valve 17 is introduced.

As shown in FIGS. 3A and 3B, the input shaft 3 loosely inserted into the screw shaft 6 switches the control valve 17 while twisting the torsion bar 9 according to the input value. In order not to exceed a certain value, both sides of the input shaft 3 are cut off at a certain angle to form a symmetrical side wall part 2.
2a, 22b, and correspondingly, engaging side walls 23a, 23 are also formed on the inner periphery of the screw shaft 6.
b is formed, and the side wall portions 22a and 22b where the relative rotation difference between the two reaches a certain value are the engaging side walls 23.
a, 23b.

And the engagement side wall 23 of the screw shaft 6
Communication holes are symmetrically provided through a and 23b, into which plungers 25a and 25b are inserted, and the base ends of the plungers 25a and 25b are connected to a spring fitted to the outer periphery of the screw shaft 6. The elastic ring 26 presses its tip against the side wall portions 22a, 22 of the input shaft 3.
It is pressed into b.

Slits 27a, 27b are formed in the plungers 25a, 25b from the distal end toward the proximal end, and as shown in FIG.
When a protrudes toward the annular groove 20 side while pushing the elastic ring 26, the annular groove 2 passes through the slit 27a.
0 and a passage 28 in the screw shaft 6 communicate with each other.

Note that this passage 28 is a low pressure passage communicating with the tank side.

Further, just before the high pressure annular groove 20 and the low pressure passage 28 are communicated with each other by the plungers 25a and 25b, a torsion bar 9 is attached to the input shaft 3.
As is clear from FIGS. 4 and 5, a cylindrical elastic cylinder whose one end in the axial direction is connected to the screw shaft 6 by a pin 8 is used to apply a steering reaction force other than the above to make the driver understand the situation. The other free end of the body 30 is adapted to engage with 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.

That is, a notch groove 31 is formed at the tip of the cylindrical elastic body 30 into which the torsion bar 9 is inserted, and a protrusion 32 is provided at the tip of the input shaft 3. 22b is the plunger 25a, 25
b is pressed so that the annular groove 20 and the passage 28 can be engaged with each other at a certain interval in the shaft rotation direction so that they touch each other before they communicate with each other, and when the amount of twist of the torsion bar 9 reaches a certain value, It engages to increase the steering reaction force.

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 to the low 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 rate as 1a. Therefore, the planet gear 12a, which was only rotating on its axis, rotates and revolves in parallel with the other planet gears 12b, and as a result, the ring gear 14a is stopped at that position. That is, the control valve 17 is maintained in the switched state and 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, during such a steering operation, for example, when the steering wheel hits an obstacle and the vehicle cannot be steered, which tends to happen when the vehicle is stationary at a stop, unless the situation is known, The driver tries to turn the steering wheel even more strongly due to the increased steering resistance.

When the rotation of the steering wheel continues 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. As it becomes larger, the cutout groove 31 of the cylindrical elastic body 30 and the protrusion 32 of the input shaft 3 engage with each other, and in addition to the torsional reaction force of the torsion bar 9, the reaction force that twists the cylindrical elastic body 30 is also applied to the input shaft 3. Feedback is sent to the steering wheel side through the steering wheel, giving the driver a feeling that is different from the normal state.

On the other hand, due to an increase in the relative rotational difference between the input shaft 3 and the screw shaft 6, the side wall portion 2 of the input shaft 3 may shift as shown in FIG.
2a approaches the engaging side wall 23a of the screw shaft 6 while pressing the plunger 25a.

As a result, after the torsion bar 9 has been twisted to such an extent that a reaction force of the cylindrical elastic body 30 begins to be generated, the high-pressure annular groove 20 and the low-pressure passage 28 communicate with each other via the slit 27a of the plunger 25a.

Therefore, the pump port P of the control valve 17
One of the working ports M1 or M2, which was in communication only with the working port _M1 or _M2 , becomes low pressure as the pump port P, which had been at high pressure until then, becomes low pressure through the annular groove ₂₀ . Schilling working chamber A or B on the high pressure side communicating via _M2
lower the pressure. As a result, the pressure difference between the left and right working chambers A and B of the piston 5 is eliminated, the driving force due to the pressure oil disappears, the so-called power steering device function is lost, and the piston 5 becomes the same as a manual steering mechanism.

In other words, when it is necessary to apply an input that exceeds the normal range, it can be assumed that the wheels are unable to steer due to some reason, and even in such a state, steering can be performed dynamically. Therefore, the problem of unnecessary high pressure being generated in the hydraulic system in such a case, causing damage to each component and a decrease in durability, can be solved by the present invention. This can be solved by limiting the steering output to .

It should be noted that by shifting to the above-mentioned manual steering (as a result of not being able to obtain hydraulic assistance from the piston 5), the driver will definitely know that there is an abnormality because the steering wheel becomes extremely heavy.

When the input shaft 3 rotates in the opposite direction to the above explanation (counterclockwise in FIG. 3), the other plunger 25b is protruded and lowers the pressure in the annular groove 20, and similarly to the above, the piston 5 is rotated. By eliminating the pressure difference between the left and right working chambers A and B, it is possible to limit the steering output.

As explained above, according to the present invention, when the steering input exceeds a certain value and the torsion amount of the torsion bar increases significantly, that is, when steering resistance exceeding the normal operating range is applied, this It is possible to reliably prevent the steering output from increasing indefinitely in response to the increase in steering output, thereby avoiding damage to the steering system and hydraulic system, while eliminating the need to provide unnecessary material strength to each component. , 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 A and B are sectional views taken along the - line in Fig. 1, and Fig. 4 is a partially enlarged view of Fig. 1. Cross section, 5th
The figure 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, 20... Annular groove, 21
...High pressure passage, 22a, 22b...Side wall portion, 23
a, 23b...Engagement side wall, 24a, 24b...Communication hole, 25a, 25b...Plunger, 26...
Elastic ring, 27a, 27b...Slit, 28
...Low pressure passage, 30...Cylindrical elastic body.

Claims (1)

[Scope of Claims] 1. A power steering system comprising a control valve that switches and operates in response to human rotation, and selectively supplies pressure oil to a power cylinder connected to the wheel side via the control valve. In the device, a part of the input shaft is inserted into the bottom pressure passage in the cylindrical screw shaft, and the two are connected by a torsion bar to allow a relative rotation difference. An annular groove is formed on the outer circumferential surface of the screw shaft, and the annular groove is communicated with the high pressure side pump port of the control valve, and the screw shaft is passed through and is in pressure contact with the input shaft, and the screw shaft and the input shaft are connected to each other. Two plungers that press and move according to the relative rotational difference between the input shaft and the screw shaft are arranged symmetrically in the rotational direction, and the relative rotational difference between the input shaft and the screw shaft, which is proportional to the human force value, exceeds a certain level. The steering force control of the power steering device reduces the steering output by letting the high pressure oil in the annular groove escape into the low pressure passage in the screw shaft through a slit formed in the plunger that is pushed out through the input shaft. Device. 2. In a power steering device that is equipped with a control valve that performs switching operations in response to input rotation, and that selectively supplies pressure oil to power cylinders connected to the wheel side via the control valve, a cylindrical A part of the input shaft is inserted into the low pressure passage inside the screw shaft, and connected with a torsion bar to allow for the relative rotation difference between the two. A groove is formed, and this annular groove communicates with the high pressure side pump port of the control valve, and also penetrates the screw shaft and comes into pressure contact with the input shaft, and corresponds to the relative rotation difference between the screw shaft and the input shaft. Two plungers that press and move are arranged symmetrically in the rotational direction, and when the relative rotation difference between the input shaft and the screw shaft, which is proportional to the human force value, reaches a certain level or more, the input shaft The high-pressure oil in the annular groove is released to the low-pressure passage in the screw shaft through the slit formed in the plunger, which is pushed out through the screw shaft, reducing the steering output. A first engaging means is formed on the other free end of the cylindrical elastic body having one end fixed, and a second engaging means is provided on the input shaft inserted into the screw shaft, so that the input shaft is connected to the plunger. These first and second engaging means are engaged at a certain interval in the rotational direction so that they are in contact with each other before pressing the torsion bar, and when the torsion bar reaches a certain amount of torsion, an elastic reaction force is applied to the input shaft. A steering force control device for a power steering device configured to provide a steering force control device for a power steering device.