JPS6143229B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a steering force control device for a power steering device, and in particular, the amount of oil supplied to the control valve of the power steering device is controlled according to the vehicle speed to increase the required steering force as the vehicle speed increases. The present invention relates to improvements in steering force control devices for automobiles, which are increasing in number.

A conventional steering force control device for a power steering device uses a bypass drain with a throttle valve that opens part of the amount of oil supplied from a pump with a constant discharge flow rate to the control valve of the power steering device as the vehicle speed increases. The structure is such that it drains from the passage.

Therefore, according to this conventional power steering device, as the vehicle speed increases, the bypass amount of pressure oil increases.
The steering characteristics change as shown in FIG. 1 as the vehicle speed increases.

That is, in FIG. 1, where the vertical axis represents input torque and the horizontal axis represents output torque, when driving at low speed, there is a gap between power steering characteristic curve a and manual steering characteristic curve b (steering characteristic of a manual steering system without power assistance). There is a difference in assist force P1 due to the supplied hydraulic pressure, and this assist force P1 enables light steering. By bypassing the amount of pressure oil corresponding to the increase in vehicle speed, the amount of oil supplied to the control valve decreases, and the assist force gradually decreases as shown in P2 and P3, and the characteristic curve becomes as shown in the figure. The slope changes as shown by broken lines c and d, and the slope of the broken line branching from the manual steering characteristic curve b gradually approaches the manual steering characteristic curve b. Therefore, during high-speed running, a steering force that is larger than the power steering characteristic during low-speed running when the assist force P1 is applied is required by the amount of decrease in the assist force, and steering stability is improved.

However, in this conventional device, in order to achieve high straight-line running performance in the micro-steering range that is frequently used during high-speed driving, that is, to increase the slope in the figure, the amount of bypass oil is significantly increased, and the characteristic curve is shown by the broken line d. It is necessary to approach the manual steering characteristic curve b. However, by doing this, if you want to further increase the steering amount, for example, if you want to obtain an output torque greater than the bending point of the broken line d, the required steering force will suddenly increase after the bending point. There are problems such as the increase in the steering force and the need for a steering force that is almost the same as manual steering characteristics.

The present invention advantageously solves the above-mentioned problems of the conventional art, and it is possible to obtain sufficient straight-line running performance in the micro-steering range that is frequently used especially when driving at high speeds, and to maintain the steering force not so large even when the amount of steering is large. It is an object of the present invention to provide a steering force control device for a power steering device.

Embodiments of the present invention will be described in detail below with reference to FIGS. 2 and 3. This power steering device includes a hydraulic control section and a hydraulic actuation section.

To explain the hydraulic control section of the power steering device, first, a stub shaft 2 is connected to the steering handle 1 via a steering shaft (not shown), and the rear end of a torsion shaft 3 is further connected to the stub shaft 2 with a pin. do. Next, the tip of the torsion shaft 3 is connected with a pin to the wormshaft 4, and the worm 4a at the tip of the wormshaft is screwed through the ball 5 into a ball circulation nut 6 that functions as a hydraulic piston.

On the other hand, the rear end of the wormshaft 4 extends rearward so as to surround the tips of the stub shaft 2 and the torsion shaft 3, thereby forming a valve body 4b. The valve body 4b is supported on the flange 8 by a thrust bearing 7, and the gap between the valve body 4b and the flange 8 is closed by a seal ring 9. Control valve housing 1 on the outside of valve body 4b
0 is fixed to the flange 8, and an intermediate bearing sleeve 11 is arranged inside the free end of the valve body 4b. This intermediate bearing sleeve 11 is supported in the axial and radial directions by a ball bearing 12 and a roller bearing 13, and rotates together with the valve body 4b.

Furthermore, two control valves 14 and 15 extending in a tangential direction to a circle around the axis of the wormshaft 4 are arranged on the valve body 4b, and these control valves 1
The pins 2a and 2b of the stub shaft 2 are engaged with the valve spools 14a and 15a of 4 and 15, respectively.

Further, the control valve housing 10 described above is provided with an inlet port 10a into which pressurized fluid from the pump 16 that discharges a constant flow of fluid flows in, and a drain port 10b which returns the fluid to the reservoir 17, and each of these ports 10a, 10b to the inflow chamber 10c and the discharge chamber 10d, and each chamber 1
0c and 10d are communicated with each other via control valves 14 and 15. Here, the control valves 14 and 15 are further communicated with annular grooves 4c and 4d provided on the outer periphery of the intermediate body 4b, and these annular grooves 4c and 4d are connected to the pressure chamber of the cylinder 20 via oil passages 18 and 19, respectively. 20a and 20b.

In addition, in the figure, 21, 22, 23, and 24 are seal rings that function to partition the respective oil passages.

Further, a hydraulic operating section to which pressure oil is supplied based on the operation of the hydraulic control section is a gear housing 25 connected to the flange 8 on the opposite side of the control valve housing 10.
Equipped with. The ball circulation nut 6, which operates as a hydraulic piston in a cylinder 20 formed as a part of this gear housing 25, has a rattle gear 6a, which is housed in a casing 26 formed as the remainder of the gear housing 25. The sector gear 27 engages with a sector gear 27 which moves a steering linkage (not shown).

Here, the ball circulation nut 6 moves within the cylinder 20 by the rotation of the worm gear 4a, and functions to rotate the sector gear 27 that meshes with the rack gear 6a.

In the present invention, the apparatus configured as described above is further provided with a bypass oil passage connecting the inlet port 10a and the drain port 10b. This bypass oil passage includes an oil passage 28 provided in the valve body 4b, a gap between the bearing 7, a hole 29 provided in the flange 8, and a pipe 30.
Consists of. A vehicle speed response throttle valve 31 is provided in the middle of the pipe 30, and a steering amount response throttle valve 32 (see FIG. 3) is provided in the control valve 14. The vehicle speed responsive throttle valve 31 is connected to a vehicle speed sensor 33 and a control circuit 34, and functions to gradually open as the vehicle speed increases.

FIG. 3 shows a second enlarged view of the control valves 14 and 15.
It is a sectional view taken along the line - in the figure, and below is a control valve 1.
The configuration of the steering amount response throttle valve 32 will be explained together with 4 and 15.

The control valves 14 and 15 include sleeves 14b and 15b attached to a valve body 4b, and valve spools 14a and 15a that slide in the axial direction within the sleeves. By fitting the pins 2a and 2b of the stub shaft 2 into 14c and 15c, the control valves 14,
15 is associated with the steering handle 1.

In the neutral position of the handle 1, the sleeve 14
There are gaps 14d and 15d between the valve spools 14a and 15a, and these gaps 1
4d and 15d are respective ports 14 provided in the sleeves 14b and 15b at positions corresponding to the annular grooves 14e and 15e provided on the outer periphery of the spool, respectively.
They communicate with annular grooves 4c and 4d in FIG. 2 via f and 15f, respectively, and these annular grooves 4c and 4d communicate with port 15g of control valve 15 and port 14g of control valve 14, respectively.

Therefore, the pressure oil flowing from port 14f flows into oil path 1.
8 to the pressure chamber 20a, while the annular groove 4c, port 15g, groove 15h and gap 15
Return to the discharge chamber 10d via port 15
The pressure oil flowing from f flows into the pressure chamber 20b through the oil passage 19.
while the annular groove 4d and port 14g
The flow then flows to the groove 14h of the spool through the gap 14 between the sleeve 14b and the spool 14a.
i and returns to the discharge chamber 10d.

The steering amount responsive throttle valve 32 in the control valve 14 is formed adjacent to the annular groove 28a of the valve spool 14a, which constitutes a part of the oil passage 28, and the through hole 28b of the sleeve 14b.
The channel is formed so that it can be opened and closed by relative displacement with respect to b. Note that this steering amount responsive throttle valve 32
Of course, it is also possible to provide the control valve 15 within the control valve 15.

The displacement amount of the valve spool when the throttle valve 32 is closed is the gap 15d, 15i (or 14d, 14
i) is greater than or equal to the displacement of the valve spool when closed. This is to ensure that the vehicle speed responsive throttle valve 31 is useful until the valves 15d and 15i are closed.

In the figure, 14j and 15j are end plates for closing one end of the sleeve, 14k and 15k are communicating holes that allow pressure oil to flow, and 14 and 15 are end plates 14.
This is a restoring spring that is inserted between the valve spools 14a, 15a and the valve spools 14a, 15a to apply a restoring force to the spools 14a, 15a. Further, 35 and 36 are support plates and bolts that maintain the end plates 14j and 15j in predetermined positions, respectively.

The operation of the device as described above will be described below along with FIG. 4 showing the steering force characteristics of the present invention.

When the vehicle is running at low speed, the vehicle speed responsive throttle valve 31 is closed and the pressure oil from the inlet port 10a is not bypassed to the reservoir 17, so the control valve functions similarly to a conventional power steering device. That is,
For example, when the steering handle 1 is rotated clockwise, the pin 2a of the stub shaft 2 moves the valve spool 14a to the right in FIG. 3, and the pin 2b moves the valve spool 15a to the right in the same figure. Move it to the left. For this reason, the control valve 14
The gaps 14d and 14i of the control valve 15 are wide open, and the gaps 15d and 15i of the control valve 15 are narrowed. Therefore, more pressure oil is supplied to the port 14f and the annular groove 4c than to the other ports 15f and the annular groove 4d, and this pressure oil is supplied from the oil passage 18 to the pressure chamber 20a.
and presses the nut 6 to the left in FIG. This pressing force assists the wormshaft 4 in clockwise rotation, while the pressure chamber 2
The fluid in 0b flows into the control valve 14 through the oil passage 19 and the annular groove 4d, and returns to the reservoir 17 through the gap 14i and the discharge chamber 10d.

Here, if the steering input torque is extremely small, each gap 14d, 14i and 15d, 1
Since the amount of change in 5i is small, the pressure chamber 20
The pressure difference between a and 20b is extremely small and requires almost the same steering input torque as in normal manual steering. However, as the input torque increases, the pressure difference increases, so the assist force also increases, and when the steering input torque is extremely large, one of the gaps is completely closed, and the other gap is closed. Since the steering wheel is in a completely open state, the steering input torque at that time becomes a value smaller by the maximum assist force than in the case of manual steering. Of course, when the steering wheel is rotated counterclockwise, the control valves 14 and 15 act in the opposite manner to that described above, and the nut 6 is pushed to the right in FIG.

As described above, the hydraulic control section according to the present invention also functions in the same way as the conventional one when driving at low speeds, but when the vehicle speed transitions from low speed to high speed, the vehicle speed responsive throttle valve 31 is gradually opened and the pressure from the pump 16 is reduced. A portion of the pressure oil is bypassed to the reservoir 17 via the oil passage 28, the communication hole 29, and the pipe 30. For this reason, the amount of oil supplied to the control valve of the hydraulic control unit decreases, and this amount of decrease increases as the vehicle speed increases, so the assist force also decreases as the vehicle speed increases, and the steering input torque becomes a manual steering state. Gradually approach.

Furthermore, when the valve spool and the control sleeve move relative to each other in connection with an increase in the steering input torque, and the opening area of the throttle valve 32 decreases below a predetermined amount, there is a gap between the pressure chambers 20a and 20b based on the decrease in the amount of bypass oil. A pressure difference begins to occur, and the steering characteristics transition to curves C and D in FIG. 4 as shown in range F.

If the steering handle 1 is operated further, the valve spool moves from its neutral position until the control valve gaps 15d and 15i (or gaps 14d and 14i) close (the amount of displacement δ _s ), the characteristic curve branches into a curve C or D depending on whether the steering variable-responsive throttle valve 32 is still open or closed at the same time.

That is, in the former case, if the stroke at which the steering amount response throttle valve 32 closes is δ _v , then in the case of δ _v > δ _s , by operating the steering wheel 1 clockwise, each valve spool will close the gap. While opening gaps 14d and 14i, gaps 15d and 1
5i, and thus, for example, gaps 15d and 15i are closed. However, even when such gaps are closed, the pressure valve 32 is not completely closed, and the bypass of the pressure oil continues. Therefore, the assist force at that time is lowered by the bypass of the pressure oil, and the steering characteristic curve C has a relatively large slope. As a result, excellent running stability during high-speed running can be obtained regardless of the magnitude of the steering amount.

In the latter case, that is, when δ _v =δ _s , the throttle valve 32 is closed when the gap 15d or 15i is closed, so that the slope of the characteristic curve D is smaller than that of the curve C. In either case, if the assist force increases to the maximum value of the pump discharge pressure, the characteristic line B will be reached.

In the present invention, since the steering amount responsive throttle valve is provided, a sudden increase in steering input torque can be prevented even if the maximum opening of the vehicle speed responsive throttle valve is increased. By increasing the opening and reducing the torsional rigidity of the torsion shaft accordingly, the steering force response curve at low speeds can be lowered without changing the steering characteristic curve at high speeds, which improves the steering performance at low speeds. Operation can be made easier.

In this way, there is also the effect of being able to arbitrarily change the steering force characteristics during low-speed running.

FIG. 5 is an enlarged sectional view showing another embodiment,
The aforementioned oil passage 28 is connected to the annular grooves 28A, 28B of the valve spools 14a, 15a and the hole 28 provided in the valve body 4b.
C, and a through hole 28D provided in each sleeve 14b, 15b, and annular grooves 28A, 28
The width of B is set by a distance δ in one direction from the width of the through hole 28D.
In addition to increasing the size by _t , the annular grooves 28A, 28
B and the adjacent edge of the through hole 28D make the throttle valve 3
2A and 32B are formed.

Here, when the steering handle 1 is rotated clockwise, for example, the valve spool 14a moves to the right in the figure, and the valve spool 15a moves to the left. In the neutral position of the valve spools 14a, 15a, the annular grooves 28A, 28B are aligned with the through hole 28D as shown, so that the throttle valve 32B reduces its opening area as soon as the movement of the spool 15a begins. However, the throttle valve 32A has a distance δ _t on its closing side that is equal to or greater than the amount of movement of the valve spool 15a until the throttle valve 32B is completely closed. Closing is not performed, and the bypass amount of pressure oil is determined only by the opening area of the throttle 32B.

Furthermore, when the steering handle 1 is rotated counterclockwise, the actions of the throttle valves 32A and 32B are reversed, and the amount of bypass oil is determined by the opening area of the throttle valve 32A.

Therefore, the throttling effect of the bypass oil passage is provided by the aforementioned vehicle speed response throttle valve 31 and the throttle valve 32A or 32B, and the function of the hydraulic control section is adjusted based on the vehicle speed and the amount of steering as in the above example. be done.

As described above, according to the present invention, optimum steering force can always be obtained regardless of the vehicle speed. In addition, this makes it possible to reduce the torsional rigidity of the torsion shaft in relation to the maximum opening of the vehicle speed response throttle valve, making it easier to operate the steering wheel when driving at low speeds, and at the same time improving steering stability when driving at high speeds. . In addition, since the steering amount responsive throttle valve is formed in the bypass oil passage by the valve spool and sleeve, there is no increase in the number of parts, making the device compact and extremely easy to process. . Furthermore, when a steering amount responsive throttle valve is formed in each control valve, each valve spool can have the same structure, which reduces the number of parts and facilitates production management. In addition, by changing the timing at which the steering amount response throttle valve closes,
In particular, it is possible to appropriately select the steering characteristic in a region where the amount of steering is large during high-speed running.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between input torque and output torque in a conventional device, Fig. 2 is a sectional view showing an embodiment of the present invention, and Fig. 3 is an enlarged view of the control valve of Fig. 2. 4 is a diagram showing the relationship between input torque and output torque in the device of the present invention, and FIG. 5 is an enlarged sectional view showing another embodiment of the control valve. DESCRIPTION OF SYMBOLS 1... Steering shaft, 2... Stub shaft, 3... Torsion shaft, 4... Worm shaft, 10a... Inlet port, 10b... Drain port, 14, 15... Control valve, 14a, 15a... Valve spool, 14b, 15b... Sleeve ,14d,1
4i, 15d, 15i... Gap, 18, 19... Oil passage, 28, 29, 30... Pipe of communication hole of oil passage (bypass oil passage), 31... Vehicle speed responsive throttle valve, 32,
32A, 32B...Steering amount response throttle valve.

Claims (1)

[Scope of Claims] 1. A worm shaft that moves a steering linkage via a steering gear, a stub shaft that is connected to a steering handle, a torsion shaft that connects these two shafts, and an oil passage that works in cooperation with the stub shaft. In a power steering device comprising: a control valve for switching the control valve; an inlet port for supplying pressurized oil to the control valve; and a drain port for discharging the oil, the inlet port and the drain port are connected to each other by a bypass oil passage. A vehicle speed responsive throttle valve that opens as the vehicle speed increases and a steering amount responsive throttle valve that closes as the torsion of the torsion shaft increases are arranged in series in this bypass oil passage. A steering force control device for a power steering device, characterized in that: 2. A steering force control device for a power steering device according to claim 1, wherein the steering amount responsive throttle valve is constituted by a valve spool of a control valve and a sleeve. 3. The amount of displacement of the valve spool when the opening of the steering amount responsive throttle valve closes is equal to or greater than the amount of displacement of the valve spool when any of the gaps between the valve spool and the sleeve closes. A steering force control device for a power steering device according to any one of claims 1 to 2.