JP4201362B2 - Power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power steering apparatus that operates a steering assist device such as a power cylinder disposed in a steering mechanism.
[0002]
[Prior art]
The power steering apparatus includes a torsion bar having one end connected to an input shaft connected to the steering wheel, the other end connected to an output shaft connected to the steering mechanism, and being twisted by the action of steering torque applied to the steering wheel, The steering assist device is operated by the relative angular displacement of the input shaft and the output shaft corresponding to the torsion bar torsion, and the steering torque applied to the steered wheels is reduced.
[0003]
Thus, the steering torque of the power steering apparatus using the torsion bar is uniquely determined by the torsional characteristics of the torsion bar in which the spring constant gradually increases linearly with respect to the torsion angle. For this reason, if a torsion bar with a large spring constant is used and the torsional characteristics of the torsion bar are set to be rigid, the neutral rigidity feeling during small turning can be improved, and straight running stability can be obtained during high-speed traveling. However, on the other hand, there is a disadvantage that the stationary steering torque at the time of large turning performed in garage entry, width adjustment, etc. becomes heavy, and using a torsion bar with a small spring constant, When the torsional characteristics are set softly, the stationary steering torque can be reduced, but on the other hand, there is a disadvantage that the feeling of neutral rigidity is lowered and the straight running stability is impaired during traveling at high speed.
[0004]
There is also known a power steering device that can eliminate such inconvenience by using an electronic control device, improve neutral rigidity, and reduce the stationary steering torque. Since the steering device uses an electronic control device, the structure is complicated, and further, since an electronic component is used, there is an inconvenience that the cost is increased.
[0005]
Further, in the power steering apparatus, the input shaft having the bar insertion hole is provided with a through hole that opens to the bar insertion hole, a curved recess is provided in the middle of the torsion bar, and the ball that engages with the curved recess is In a region where a pressure oil chamber that is inserted into the through-hole and further presses the ball against the curved recess is provided around the input shaft, and in a region where the steering torque applied to the input shaft is small, from the connecting portion with the output shaft The torsion bar is twisted with an effective length from the ball to the constrained portion, and after the steering torque exceeds a predetermined torque and the engagement with the curved concave portion of the ball is released, the torsion bar No. 61-41787 is the one that can improve the neutral rigidity as a whole and reduce the stationary steering torque. Which is incorporated herein by reference.
[0006]
Similarly, a through hole that opens to the bar insertion hole is provided in the output shaft having the bar insertion hole, a curved recess is provided in the middle of the torsion bar, and a torsional restraining pin that engages with the curved recess is provided in the through hole. In addition, a pressure oil chamber that presses the torsional restraining pin against the curved recess is provided on the outer periphery of the output shaft, and in a range where the steering torque applied to the input shaft is small, it is twisted from the connecting portion with the input shaft. After the torsion bar is twisted with an effective length from the restraining part to the restraining pin, and after the steering torque is increased beyond a predetermined torque and the engagement with the curved recess of the torsion restraining pin is released. The total length of the torsion bar becomes an effective length, and the overall rigidity can be improved, and the stationary steering torque can be reduced. It disclosed in Japanese.
[0007]
[Problems to be solved by the invention]
However, the power steering apparatus disclosed in Japanese Patent Publication No. 61-41787 and Japanese Patent Publication No. 53-41851 has a hydraulic oil chamber provided around the input shaft or the output shaft and introduced into the hydraulic oil chamber. Since the ball or pin is pressed and engaged with the middle part of the torsion bar by the hydraulic pump, the hydraulic pump supplies the hydraulic pressure to the pressure oil chamber, the seal member of the pressure oil chamber, and the pressure oil chamber separately from the ball or pin. In addition, many parts such as an oil supply / discharge passage and an oil tank are required, resulting in a complicated structure and high cost.
[0008]
The present invention has been made in view of such circumstances, and as a pressing means for pressing a torsional restraint that restrains torsion over the entire length of the torsion bar, an elastic body such as a flexible synthetic resin or spring is provided. It is an object of the present invention to provide a power steering apparatus that can reduce the number of parts and reduce the cost by inserting and holding the elastic body and the torsional restraint body in a holding hole.
[0009]
[Means for Solving the Problems]
The power steering apparatus according to the first aspect of the present invention has a bar insertion hole, and is inserted into the input shaft connected to the steering wheel, the output shaft connected to the steering mechanism, and the bar insertion hole. The input shaft and the output shaft are connected on the same axis, and the torsion bar that is twisted by the action of the steering torque applied to the steered wheel and the middle part of the torsion bar are engaged to restrain the torsion over the entire length of the torsion bar. A power steering device including a torsional restraining body, wherein the steering assist device is operated by a relative angular displacement of the input shaft and the output shaft according to torsion of the torsion bar, and the output shaft is inserted into the bar insertion hole. has an opening for holding hole, into the holding hole, the elastic body for pressing the inserted holding the twist restraint and該捩Re constraint on the outer peripheral surface of the torsion bar, further wherein holding the retaining member of the elastic member Held in the hole, front The torsion bar is in its intermediate portion, the torsion constraint is characterized in that it comprises a flat engagement surface for engaging.
[0010]
In the first invention, the torsional restraining body is pressed using the elastic body, and the torsional restraining body is engaged with the middle part of the torsion bar to restrain the torsion over the entire length of the torsion bar. In the region where the steering torque applied to the torsion bar is small, the torsion bar is twisted and the limited length from the connecting portion with the input shaft to the restraint portion by the torsion restraint is generated as an effective length. The torsional characteristics of the torsion bar can be made rigid. Accordingly, it is possible to improve the feeling of neutral rigidity at the time of small turning and to obtain straight running stability during traveling at high speed. Further, when the steering torque exceeds a predetermined torque, the torsional restraining body starts to move toward the inner and outer diameter sides of the holding hole against the force of the elastic body due to the steering torque, and the torsion bar restrains the torsional restraining body against the torsion bar. The force is gradually released, and subsequent torsion of the torsion bar is caused by the total length between the connecting portions of the input shaft and the output shaft as an effective length, and the torsion characteristics of the torsion bar can be softened. Therefore, the stationary steering torque during large turning can be reduced.
[0011]
Such torque characteristics can be obtained by using an elastic body inserted into and held in the holding hole of the output shaft together with the torsional restraint body and a retaining body for the elastic body separately from the torsional restraint body. Since the structure is simple and the elastic body can be incorporated together with the torsional restraint body, the assembling workability can be improved and the cost can be reduced as a whole. In addition, since a flat engagement surface is provided in the middle of the torsion bar, the torsion bar can be processed more easily than in the case where a curved recess is provided in the middle of the torsion bar. The cost of the entire steering device can be further reduced.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. 1 is a longitudinal sectional view of a hydraulic control valve portion of a power steering apparatus, FIG. 2 is a sectional view taken along line X-X with part of FIG. 1 omitted, and FIG. FIG. 3B is an operation explanatory diagram when the torsion bar is twisted, FIG. 4 is a torque characteristic diagram of the torsion bar and the spring body, FIG. 5 is a sectional view of the valve body and the valve spool portion, and FIG. It is a schematic diagram of a power steering device.
[0020]
As shown in FIG. 6, the power steering apparatus includes a pinion that meshes with a hollow input shaft 2 connected to a steering wheel 1 for steering, and a middle portion of a rack shaft 11 that extends in the left-right direction at the front portion of the vehicle body. 12, an output shaft 3 connected to the steering mechanism, a torsion bar 4 (see FIG. 1) that coaxially connects the input shaft 2 and the output shaft 3, and hydraulic control provided on the input shaft 2 and the output shaft 3 The steering wheel 1 includes a valve 5, a steering assist power cylinder S configured in the middle of the rack shaft 11, a hydraulic pump P serving as a hydraulic source, and an oil tank T serving as a drain destination. The hydraulic control valve 5 according to the operation of the hydraulic control valve 5, which will be described later, supplies the hydraulic pressure generated by the hydraulic pump P to the power cylinder S, while causing the return of the return oil from the power cylinder S to the oil tank T. The power cylinder S is generated by the supply hydraulic pressure. In addition the hydraulic force (steering assist force) to the rack shaft 11 are configured to assist the sliding of the rack shaft 11.
[0021]
As shown in FIG. 1, the input shaft 2 has a bar insertion hole 21 penetrating in the axial direction, and the output shaft 3 is provided at one end portion, and one end portion of the input shaft 2 is freely fitted and supported. And a bar insertion hole 32 extending in the axial length direction from the fitting recess 31 to the other end where the pinion 12 is provided. The input shaft 2 and the output shaft 3 are rotatably supported in the cylindrical valve housing 50 via bearings 13, 14, and 15 around the coaxial shaft. The torsion bar 4 is inserted, one end of the torsion bar 4 is connected to the other end of the input shaft 2 by a knock pin 22, and the other end extends to the other end where the pinion 12 of the output shaft 3 is provided. And is connected to the end portion of the bar insertion hole 32 by spline fitting.
[0022]
As shown in FIG. 1, the hydraulic control valve 5 is rotatably fitted and supported in the valve body 50, and has a cylindrical valve body 51 that rotates together with the output shaft 3, and a relative rotatable insertion inside the valve body 51. And a valve spool 52 integrally formed on the outer periphery of the midway part of the input shaft 2.
[0023]
The output shaft 3 and the valve body 51 include an engagement recess 53 that is recessed from one end of the valve body 51 toward the other end, and a rotation restraining pin that protrudes radially outward from one end of the output shaft 3. It is configured to be able to rotate together by engaging with 33.
[0024]
As shown in FIG. 5, a plurality of oil grooves 51 a and 52 a extending in the axial length direction are arranged in parallel on the inner peripheral surface of the valve body 51 and the outer peripheral surface of the valve spool 52 in the circumferential direction. These are arranged in a staggered manner in the circumferential direction on the fitting circumference, and form a plurality of throttle portions that change the throttle area according to the relative angular displacement between adjacent oil grooves 51a, 52a. Yes.
[0025]
As shown in FIG. 5, the hydraulic pump P serving as an oil supply source is connected to either one of the oil grooves 51a and 52a (oil supply groove) through a pump port 50a passing through the valve housing 50 inward and outward and an oil supply hole 51b passing through the valve body 51. The oil grooves (distribution grooves) adjacent to both sides of the oil grooves 51a and 52a are connected to the oil supply holes 51c and 51d penetrating the valve body 51 and the valve housing 50 inside and outside. The two cylinder chambers SL and SR of the power cylinder S as the oil feeding destination are communicated with each other through the respective cylinder ports 50b and 50c penetrating therethrough. Further, an oil groove (oil drain groove) adjacent to the other side of these distribution grooves is communicated with an oil drain chamber 54 formed on one side of the valve body 51 through a hollow portion of the input shaft 2. The oil tank 54 is communicated with an oil tank T as a drainage destination through a tank port 50d penetrating the valve housing 50 in and out at a corresponding position in the oil chamber 54.
[0026]
The plurality of throttle portions arranged on the fitting periphery of the valve body 51 and the valve spool 52 are adjusted to neutral points so as to have equal throttle areas in a neutral state where the torsion bar 4 is not twisted. The pressure oil supplied from the hydraulic pump P to the oil supply groove through the pump port 50a at the neutral point is uniformly introduced into the distribution grooves adjacent to both sides, and further introduced into the drain oil groove adjacent to these other sides. Then, the oil is discharged to the oil tank T through the hollow portion of the input shaft 2, the oil discharge chamber 54, and the tank port 50d. At this time, no pressure difference is generated between the cylinder chambers SL and SR communicated with the distribution groove, and the power cylinder S does not generate any force.
[0027]
On the other hand, when a rotational torque (steering torque) for steering is applied to the steered wheels 1, a torsion bar is provided between the input shaft 2 and the output shaft 3, that is, between the valve spool 52 and the valve body 51. A relative angular displacement occurs in the direction of the steering torque with a twist of 4, and the aperture area of the apertures arranged on the fitting circumference of both changes. At this time, the pressure oil supplied to the oil supply groove is mainly introduced into one of the distribution grooves through the throttle portion on the side where the throttle area is increased, and communicated with the distribution groove via the cylinder port. A pressure difference is generated between one cylinder chamber SL (or SR) and the other cylinder chamber SR (or SL) communicated with the other distribution groove via a cylinder port. The oil pressure corresponding to the is generated.
[0028]
At this time, hydraulic oil is pushed out from the other cylinder chamber SR (or SL), flows back to the other distribution groove through the corresponding cylinder port, and passes through a throttle portion having an increased throttle area on one side of the distribution groove. The oil is introduced into the oil drain groove and discharged to the oil tank T through the hollow portion of the input shaft 2, the oil drain chamber 54, and the tank port 50 d.
[0029]
Thus, a holding hole 34 having a circular cross section that penetrates in the radial direction and opens into the bar insertion hole 32 is formed at one end portion of the output shaft 3 of the power steering apparatus configured as described above with a phase difference of 180 degrees. The torsion bar 6 is engaged with the middle part of the torsion bar 4 to restrain the torsion bar 4 torsion over the entire length thereof, and the torsion bar 4 is connected to the torsion bar 4. The elastic body 7 that presses against the outer peripheral surface and the retaining body 8 that prevents the elastic body 7 from coming out of the holding hole 34 are inserted and held, respectively.
[0030]
As shown in FIG. 1, the torsion bar 4 includes a connecting portion 4c connected to the other end portion of the input shaft 2 to the intermediate portion 4b, and a connecting portion 4a connected to the other end portion of the output shaft 3 to the intermediate portion 4b. The spring constant is greatly changed with the middle portion 4b as a boundary. Further, two flat engaging surfaces 41 with which the torsional restraining bodies 6 are engaged are provided on the outer peripheral surface of the midway portion 4b with a phase difference of 180 degrees.
[0031]
Each of the torsional restraining bodies 6... Uses a cylindrical pin movable within the holding hole 34..., And has one end engaged with the engaging surface 41. The elastic bodies 7 are made of a flexible synthetic resin cylindrical member so that bending is allowed in the holding hole 34. The elastic body 7 may be made of synthetic resin, rubber, or a spring body such as a coil spring or a disc spring.
[0032]
Further, the retaining member is formed by using a circular end face pin, and is fixed to the outer opening of the holding hole by press-fitting to prevent the elastic body from coming out of the holding hole.
[0033]
As described above, the torsional restraining body 6 that engages the midway part of the torsion bar 4 is between the connecting part 4a with the output shaft 3 of the torsion bar 4 and the restraining part 4b (the engaging surface 41 part) by the torsional restraining body 6. In this state, the torsion bar 4 is twisted from the connecting portion 4c to the input shaft 2 to the restraining portion (engagement surface 41 portion) by the twist restraining body 6 as shown in FIG. Is generated as an effective length L1. When the torsion bar 4 is twisted, the torsional restraining body 6 engaged with the engagement surface 41 is pressed toward the elastic body 7 by the component force F of the twisting force, and this pressing force increases the twisting force. It increases with. Therefore, when the torsional force applied to the torsion bar 4 increases and the component force F exceeds the pressing force by the elastic body 7, the torsional restraining body 6 moves outside the holding hole 34 against the force of the elastic body 7. As shown in FIG. 3B, the engagement position with the engagement surface 41 moves to the end thereof. During this time, the restraint of the torsion bar 4 by the torsional restraining body 6 is gradually released, and the torsion bar 4 twists the effective length of the substantially entire length between the connecting portions 4c and 4a between the input shaft 2 and the output shaft 3. Occurs as L0.
[0034]
Thus, the torsion bar 4 is twisted approximately halfway until the steering torque exceeds a predetermined torque, that is, while the component force F applied to the torsional restraining body 6 is below the force of the elastic body 7. When the length is generated as the effective length L1 and has a large spring constant and a torsional torque exceeding the predetermined torque is applied, the substantially full length is generated as the effective length L0 and at the same time the spring constant is extremely It is configured to decrease.
[0035]
The relative angular displacement between the input shaft 2 and the output shaft 3 connected via the torsion bar 4 increases the steering torque until the steering torque applied to the input shaft 2 reaches the predetermined torque. Accordingly, the steering assist force generated by the power cylinder S according to the relative angular displacement gradually increases in a region where the steering torque is small, and the steering torque increases. It will increase rapidly in the area.
[0036]
Therefore, during small turning with a generally small steering torque applied to the steering wheel 1, the steering assistance by the power cylinder S is hardly performed, and the neutral rigidity feeling of the steering wheel 1 can be improved, and straight running stability can be obtained during traveling at high speed. On the contrary, during large turning, the power cylinder S generates a large steering assist force, so that the burden on the driver can be effectively reduced, and stationary steering during large turning is possible. Torque can be reduced. In addition, the torsional restraining body 6 may be provided with two, or may be one or two or more. In these cases, the engagement surface 41 and the holding hole 34 are provided corresponding to the number of the twist restraining bodies 6.
[0037]
Further, in the above embodiment, the torsion bar 4 is configured such that the spring constant is greatly different depending on the shape and length at the middle part 4b by changing the shape of one end side and the other end side with respect to the middle part 4b. When the restraint by the torsional restraint 6 is released, the other end connected to the output shaft 3 is configured to be twisted easily. -The material may be made different and the spring constant may be made different so that the other end connected to the output shaft 3 is easily twisted. When a certain degree of rigidity is desired from the small turning to the large turning, the spring constants on the one end side and the other end side are made the same with respect to the midway portion 4b so that the substantially entire length is effective. It may be configured such that when L ₀ is set, only a decrease in spring constant due to an increase in length occurs.
[0038]
Further, in the above embodiment, the retaining body 8 is fixed by press-fitting into the holding hole 34. However, the retaining body 8 may be tightened to the holding hole 34, or a substantially C-shaped retaining ring may be used. The wheel may be fitted to the outer periphery of the output shaft 3, and the structure is not particularly limited.
[0039]
Further, the power steering apparatus of the present invention is configured to include the hydraulic control valve 5, and further includes detection means for detecting the relative angular displacement amount of the input shaft 2 and the output shaft 3, and the detection result of the detection means Even if the electric motor that operates based on the above is an electric power steering apparatus that is arranged in the middle of the steering mechanism, it can be configured in the same manner, and similar effects can be expected.
[0040]
【The invention's effect】
As described in detail above, according to the power steering apparatus of the first invention, the torsional restraining body can be engaged with the middle part of the torsion bar to restrain the torsion over the entire length of the torsion bar. Improves the feeling of neutral rigidity during turning, provides straight-line stability during high-speed driving, reduces light steering torque during large turning, and provides a bar on the output shaft. A holding hole is provided in the insertion hole, and a torsional restraining body and an elastic body that presses the torsional restraining body against the outer peripheral surface of the torsion bar are inserted and held in the holding hole, and a retaining body for the elastic body is provided. Since the torsion bar is restrained from twisting over the entire length, the number of parts is small, the structure is simple, and the elastic body can be incorporated together with the torsion restraining body, so that the assembly workability can be improved as a whole. Can reduce the cost . In addition, since a flat engagement surface is provided in the middle of the torsion bar, the torsion bar can be processed more easily than in the case where a curved recess is provided in the middle of the torsion bar. The cost of the entire steering device can be further reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a hydraulic control valve portion of a power steering apparatus according to the present invention.
FIG. 2 is a cross-sectional view taken along line XX in which a part of FIG. 1 is omitted.
FIGS. 3A and 3B show a twist restraining portion of a torsion bar of a power steering apparatus according to the present invention, in which FIG. 3A is an enlarged sectional view thereof, and FIG. 3B is an operation explanatory diagram when the torsion bar is twisted. .
FIG. 4 is a torque characteristic diagram of a torsion bar and a spring body of the power steering apparatus according to the present invention.
FIG. 5 is a cross-sectional view of a valve body and a valve spool portion of the power steering apparatus according to the present invention.
FIG. 6 is a schematic diagram of a power steering apparatus according to the present invention.
[Explanation of symbols]
2 Input shaft 21 Bar insertion hole 3 Output shaft 32 Bar insertion hole 34 Holding hole 4 Torsion bar 41 Engagement surface 6 Torsional restraint body 7 Elastic body 8 Retaining body

Claims (1)

An input shaft that has a bar insertion hole and is connected to the steering wheel, an output shaft that has a bar insertion hole and is connected to the steering mechanism, and is inserted into each of the bar insertion holes to coaxially connect the input shaft and the output shaft. A torsion bar that is twisted by the action of steering torque applied to the steered wheel, and a torsional restraining body that engages a midway portion of the torsion bar and restrains torsion over the entire length of the torsion bar, In the power steering apparatus in which the steering assist device is operated by the relative angular displacement of the input shaft and the output shaft according to torsion, the output shaft has a holding hole that opens to the bar insertion hole, and the holding hole The torsional restraining body and an elastic body that presses the torsional restraining body against the outer peripheral surface of the torsion bar are inserted and held therein, and a retaining body of the elastic body is held in the holding hole. The middle part , Power steering device, characterized in that said torsional constraint is provided with a flat engagement surface for engaging.

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