JP2001304986A - Steering torque detector in cable type steering gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately detect steering torques in right and left directions inputted to a steering wheel in a steering torque detector of a cable type steering gear. SOLUTION: Pressing parts 19a and 19a set in a middle part of an arm member 19 are butted against magnetostrictive materials 25L and 25R arranged inside a pair of coils 24L and 24R respectively. Reaction forces of outer tubes 6o and 7o of a Bowden cable where a compressive force in an axial direction acts because of the steering torque and an initial load of a disc spring 17 are let to act on both ends of the arm member 19. Even when a direction of the steering torque inputted to the steering wheel is switched and a point of action of the reaction force of the compressive force in the axial direction of the outer tube 6o, 7o switches from one end to the other end of the arm member 19, the steering torque is detected on the basis of a difference of loads acting on both magnetostrictive materials 25L and 25R corresponding to the steering torque, so that an accuracy for detecting the steering torque is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cable-type steering device in which a steering wheel and a steering gear box are connected by a cable such as a Bowden cable, and more particularly to a steering torque detecting device.

[0002]

2. Description of the Related Art There has been proposed a cable type steering apparatus employing a flexible transmission means such as a Bowden cable instead of a steering shaft connecting a steering wheel and a steering gear box (Japanese Patent Laid-Open No. Hei 8-24).
No. 31). By employing such a cable-type steering device, not only can the position of the steering wheel relative to the position of the steering gear box be freely selected, but also the vibration of the steering gear box can be hardly transmitted to the steering wheel.

When an electric power steering device is combined with such a cable type steering device, it is necessary to detect a steering torque input to a steering wheel in order to control the operation of the assist motor. JP 2000
Japanese Patent No. 25623 discloses a steering torque detecting device using a magnetostrictive material. This circuit applies a reaction force of an axial compressive force acting on an outer tube with steering to a magnetostrictive material, and detects a change in inductance of a coil on an outer periphery of the magnetostrictive material due to a change in magnetic permeability of the magnetostrictive material. , And detects the axial compression force of the outer tube, which is proportional to the steering torque.

[0004]

By the way, in such a cable-type steering device, when the handle is operated to the right, tension is generated only in the inner cable of one Bowden cable, and when the handle is operated to the left, the inner cable of the other Bowden cable is formed. Tension occurs only in the cable. Therefore, when the steering wheel is operated to the right, the steering torque detecting device described in Japanese Patent Application Laid-Open No. 2000-25623 discloses a reaction force of the axial compression force of the outer tube corresponding to the one inner cable on the side where tension is generated. Is applied to one of the magnetostrictive members to detect the steering torque in the right direction, and when the steering wheel is operated to the left, the reaction force of the axial compression force of the other outer tube corresponding to the other inner cable on the side where tension is generated is determined. By acting on the other magnetostrictive material, the steering torque in the left direction is detected.

However, when the rightward steering torque and the leftward steering torque are detected using only the corresponding magnetostrictive materials as described above, the change in the input load due to variations in the characteristics of the magnetostrictive materials is detected. The amount of change in the output voltage of the coil with respect to the steering torque becomes inconsistent with the direction of the steering torque. There was a possibility that the detection accuracy was reduced differently.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a steering torque detecting device for a cable-type steering device capable of accurately detecting both left and right steering torques input to a steering wheel. I do.

[0007]

According to the first aspect of the present invention, a driving pulley connected to a steering wheel and rotating is connected to a steering gear box for turning wheels. And a pair of cables that connect the driving pulley and the driven pulley to transmit the steering torque, and each of the pair of cables includes an outer tube and an inner cable, and an end of the outer tube is driven. In a cable-type steering device that is supported by a drive pulley housing that houses a pulley and the inner cable is wound around the drive pulley, the reaction force of the axial compression force of the outer tube, which varies according to the magnitude of the tension of the inner cable, A pair of input sections on which this reaction force and an initial load in the same direction act are connected to the one An arm member is provided corresponding to the outer tube, and a pair of output portions are provided between the pair of input portions of the arm member so as to be separated from each other in a direction connecting the pair of input portions. A cable provided with a pair of load supporting portions for receiving a load from the portion, and detecting a steering torque input to the steering wheel based on a difference between loads transmitted from the pair of output portions to the corresponding load supporting portions. There has been proposed a steering torque detection device in a steering apparatus of the type.

According to the above structure, when a steering torque is input to the handle and the drive pulley rotates, the tension of one inner cable increases, the tension of the other inner cable decreases, and the inner cable on the side where the tension increases is provided. An axial compression force is generated in the outer tube that houses the cable, and the resultant force of the reaction force of the axial compression force and the initial load given in advance acts on the input portion of the arm member.

When an axial compressive force acts on one of the outer tubes by operating the handle to one of the left and right sides, a constant load corresponding to the initial load is applied from one output portion of the arm member close to the outer tube to the corresponding load supporting portion. When a load in which a load proportional to the reaction force of the axial compressive force is applied to the load of the above, and the axial compressive force acts on the other outer tube by operating the handle to the other left and right, from the one output portion, A load is applied to the corresponding load supporting portion by subtracting a load proportional to the reaction force of the axial compression force of the other outer tube from a constant load corresponding to the initial load.

Therefore, even if the handle is operated in either the left or right direction, the load transmitted from the one output portion of the arm member to the corresponding load supporting portion is the side on which the axial compressive force acts at that time. It will change according to the reaction force from the outer tube. As a result, if the steering torque is detected based on the difference between the loads acting on both load supporting portions, the difference in the load is calculated as the change in the steering torque regardless of whether the steering wheel is operated to the left or right. Since it has a proportional change, the detection accuracy of the steering torque is enhanced.

When the steering torque is not input to the steering wheel, the load transmitted from the pair of output portions of the arm member to the corresponding load supporting portion based on the initial load is the initial load acting on the pair of input portions. Are equal to the initial load, the difference between the loads is zero. If the initial loads acting on the pair of input units are not equal, the initial load, a fixed value determined according to the distance between the pair of input units and the distance between the pair of output units, The difference is also a fixed value determined according to the initial load, the distance between the pair of input units, and the distance between the pair of output units.

The magnetostrictive members 25L, 25R in the embodiment
Corresponds to the load supporting portion of the present invention.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

FIGS. 1 to 11 show an embodiment of the present invention. FIG. 1 is an overall perspective view of a cable-type steering device, FIG. 2 is an enlarged view taken along line 2-2 of FIG. 1, and FIG. 2 of FIG.
4 is a sectional view taken along line 4-4 of FIG. 2, FIG. 5 is an enlarged view of a main part of FIG. 2, FIG. 6 is a sectional view taken along line 6-6 of FIG. 1, and FIG. 8, FIG. 8 is a diagram showing the balance of the load acting on the arm member, FIG. 9 is a diagram showing the input and output waveforms of the steering torque detection circuit, and FIG. 10 is an explanatory diagram of the process of detecting the steering torque (left and right). FIG. 11 is an explanatory diagram of the process of calculating the steering torque (when the left and right initial loads are different).

As shown in FIG. 1, a drive pulley housing 3 provided in front of a steering wheel 1 of an automobile and a driven pulley housing 5 provided above a steering gear box 4.
Are connected by two Bowden cables 6 and 7. Tie rods 8L, 8R extending in the left-right direction of the vehicle body from both ends of the steering gear box 4
L and WR are connected to a knuckle (not shown).

As shown in FIGS. 2 to 4, a rotating shaft 10 fixed to a boss of the handle 1 is mounted on a drive pulley housing 3 fixed to the vehicle body 2 with three bolts 9 via a bearing 11. The rotating shaft 1
The drive pulley 12 is fixed to zero. The two Bowden cables 6 and 7 include outer tubes 6o and 7o and inner cables 6i and
7i. A single pulley groove 12a is spirally formed on the outer periphery of the driving pulley 12, and fixed grooves 12b, 12b are formed on both side surfaces of the pulley groove 12a.
And pin holes 12c connected to the fixing grooves 12b, 12b.
12c is formed. The inner cables 6i and 7i of the Bowden cables 6 and 7 respectively have pins 13 and 13 fixed to one ends thereof and pin holes 12c and 12
After being press-fitted into the drive pulley 12, the drive pulley 12 is wound around the pulley groove 12a from the fixed grooves 12b and 12b and pulled out in substantially the same direction from both ends in the diameter direction of the drive pulley 12.

A steering torque sensor TS for detecting the magnitude of the steering torque input to the steering wheel 1 by the driver is provided inside the drive pulley housing 3. Hereinafter, the structure of the steering torque sensor TS will be described.

A pair of right and left U-shaped cutouts 3c, 3c which are opened on a joint surface 3b with the column cover 2 are formed on a wall surface 3a farthest from the rotary shaft 10 of the drive pulley housing 3, and these cutouts 3c, 3c are formed. The annular cable guides 14 made of an elastic material are fitted into 3c. Outer tubes 6o, 7o of two Bowden cables 6, 7
The cylindrical adjust nuts 16, into which the male threads 15, 15 formed at the ends of the cable guides are screwed, are connected to the cable guide 1.
4 and 14 extend into the drive pulley housing 3. Annular flanges 16a, 16a are formed on the outer peripheral surfaces of the adjust nuts 16, 16 extending inside the drive pulley housing 3, and these flanges 1
Washers 28, 2 supported on 6a, 16a and wall surface 3a
The coned disc springs 17, 17 are mounted between the steps 8 and 8.

A pair of circular openings are formed at both ends of one arm member 19 extending in a direction orthogonal to the inner cables 6i, 7i, and these openings are fitted to the ends of the adjustment nuts 16, 16 to form a flange. 16a, 16a. Adjust nuts 16, 16 are disc springs 17,
The elastic nut 17 urges the arm member 19 into contact with the adjusting nuts 16, 16 and the arm member 19.
To prevent backlash. When the arm member 19 is displaced by the reaction force of the axial compression force of the outer tubes 6o, 7o to be described later, the positions of the adjustment nuts 16, 16 integrated with the arm member 19 also slightly move. It is absorbed by the deformation of the elastic cable guides 14 supporting the nuts 16.

Referring to FIG. 5 together, it is apparent that
The substantially rectangular parallelepiped sensor unit 20 includes a sensor casing 21 forming an outer frame of the sensor unit 20, and a pair of bobbins 23L and 23R, a pair of coils 24L and 24R wound around the bobbins 23L and 23R, and a coil. 24
L, 24R, a pair of cylindrical magnetostrictive members 25
L and 25R are stored. The magnetostrictive materials 25L and 25R are:
It is composed of a substance whose magnetic permeability changes according to the load acting on it. The sensor casing 21 is integrally provided with a mounting portion 21a. The mounting portion 21a is fastened to the upper surface of the first support portion 3f protruding from the bottom surface 3d of the drive pulley housing 3 by two bolts 26, 26, The sensor unit 20 is fixed to the drive pulley housing 3.
In this state, one end of the pair of magnetostrictive materials 25L and 25R penetrates the sensor casing 21 and abuts against the pressing portions 19a and 19a provided on the arm member 19, and the other end penetrates the sensor casing 21 and the first support portion. Contact the side of 3f.

A pair of inner cable guides 27L, 27L is provided between the sensor casing 21 and a pair of second support portions 3g, 3g protruding from the bottom surface 3d of the drive pulley housing 3.
27R are arranged. Inner cable guide 27L,
27R is positioned by engaging and recessing the side walls of the second support portions 3g, 3g, and the upper surface is pressed by the mounting portion 21a of the sensor casing 21 to be prevented from falling off. Outer tube 6
Inner cables 6i, 7i extending from o, 7o pass through the inner cable guides 27L, 27R and are wound around the drive pulley 12.

As is apparent from FIG. 6, a driven pulley 34 is fixedly mounted on a driven shaft 5 rotatably supported by the driven pulley housing 5 via two ball bearings 31 and 32, and both inner cables 6i are provided. , 7i has a spiral pulley groove 34 formed on the outer periphery of the driven pulley 34 at the other end.
a, and is wound around fixing grooves 34b, 34b formed on the side surface of the driven pulley 34, and fixed by pins 35, 35. The other ends of the outer tubes 6o, 7o of both Bowden cables 6, 7 are fixed to the driven pulley housing 5 (see FIG. 1). A pinion 36 is provided at the tip of a rotating shaft 33 projecting from the driven pulley housing 5 into the steering gear box 4, and the pinion 36 is connected to the steering gear box 4.
And meshes with a rack 38 formed on a steering rod 37 supported movably in the left and right directions.

A power steering motor 39 as power assist means is supported by the driven pulley housing 5, and an output shaft 4 of the power steering motor 39 is provided.
The worm 41 provided on the rotation shaft 33 meshes with the worm wheel 42 provided on the rotating shaft 33. Therefore, the torque of the power steering motor 39 is transmitted to the rotating shaft 33 via the worm 41 and the worm wheel 42.

FIG. 7 shows a circuit for detecting the steering torque when the steering wheel is operated to the left. A resistor 53 and the coil 24L are provided between a 5-volt power supply line 51 and a pulse signal generating means 52. Are connected in series, and the sensor output VB is output from between the resistor 53 and the coil 24L.
(T) is extracted. The steering torque when the steering wheel is operated in the right direction is detected by a circuit having the same structure in which the left coil 24L in FIG. 7 is replaced with the right coil 24R.

Next, the operation of the embodiment of the present invention having the above configuration will be described.

When the steering wheel 1 is operated to the left to rotate the vehicle and the rotating shaft 10 is rotated in the X direction in FIG. 2, one of the Bowden cables 6 and 7 wound around the drive pulley 12 is pulled. When the other inner cable 6i is loosened, the drive pulley 12
Is transmitted to the driven pulley 34. As a result, FIG.
, The rotating shaft 33 of the driven pulley 34 rotates, and the steering torque is transmitted to the wheels WL, WR via the pinion 36, the rack 38, and the swirling rod 37 in the steering gear box 4. Conversely, when the handle 1 is operated to the right to rotate the rotating shaft 10 in the X 'direction in FIG. 2, the other inner cable 6i of the Bowden cables 6, 7 is pulled,
By loosening one inner cable 7i,
Since the rotation of the driving pulley 12 is transmitted to the driven pulley 34 in the opposite direction, the steering torque in the opposite direction is transmitted to the wheels WL and WR.

Now, the rotation shaft 10 is moved by the steering torque as shown in FIG.
When the outer tube 7 is rotated in the X direction, a tension proportional to the steering torque acts on the inner cable 7i.
An axial compression force proportional to the tension acts on o. The spring force of the disc spring 17 acts on the adjust nut 16. As a result, the reaction force in the opposite direction having the same magnitude as the axial compression force and the elastic force of the disc spring 17 are adjusted by the adjusting nut 1.
6 and acts on one end of the arm member 19, a load acts on the magnetostrictive material 25 </ b> L from one pressing portion 19 a provided in the middle of the arm member 19. At this time, since the other inner cable 6i is loosened and no tension is generated, only the elastic force of the disc spring 17 acts on the other end of the arm member 19 via the adjustment nut 16 and is provided in the middle of the arm member 19. A load acts on the magnetostrictive material 25R from the other pressing portion 19a.

The inductance L of the coil 24L of the steering torque sensor TS is given by the following equation.

L = k × μ ₀ × μ _T (P) × πr ² / (a × N ² ) where r is the radius of the coil 24L, a is the length of the coil 24L, and N is the number of turns of the coil 24L. , Μ ₀ is the magnetic permeability of vacuum, μ _T (P) is the relative magnetic permeability of the magnetostrictive material 25L that changes with the load P, and k is the Nagaoka coefficient. Nagaoka coefficient k is 2r /
It is determined from the conversion table using a as a parameter.

As is apparent from the above equation, when the load P acts, the relative permeability μ _T (P) of the magnetostrictive material 25L changes and the inductance L of the coil 24L changes. The load P acting on the magnetostrictive material 25L can be detected.

More specifically, when the pulse signal generating means 52 of the circuit shown in FIG. 7 outputs a rectangular wave VA (t) as shown in FIG. 9A, the coil 2 shown in FIG.
The falling portion of the 4L output voltage VB (t) is given by VB (t) = 5 × exp (−Rt / L). The bottom voltage VBL of the output voltage VB (t) increases when the inductance L of the coil 24L is large, and decreases when the inductance L of the coil 24L is small. The load P acting on the magnetostrictive material 25L can be calculated based on the output voltage VBL). The calculation of the load P acting on the left magnetostrictive material 25L has been described above.
Is also applied to the bottom voltage VBR of the right coil 24R (hereinafter referred to as the output voltage VBR of the coil 24R).
Can be calculated in the same manner.

FIG. 8 shows the balance of the load acting on the arm member 19. When the steering torque is not input to the steering wheel 1, initial loads F ₀ , F ₀ due to the resilient force of the disc springs 17, 17 act on the contact portions (input portions of the present invention) with the adjustment nuts 16, 16. And magnetostrictive materials 25L, 25R
The reaction forces P ₁ , P ₂ from the magnetostrictive materials 25L, 25R are applied to the abutting portions, ie, the pressing portions 19a, 19a (output portions of the present invention).
Acts. Here, a pair of outer tubes 6o, 7o
The distance between them (the distance between the input parts) is d ₀ , and the distance between the pair of magnetostrictive materials 25L, 25R (the distance between the output parts) is d. Hereinafter, a case where the initial loads F ₀ and F ₀ acting on both input sections are assumed to be equal will be considered.

It is assumed that the handle 1 is operated to the right and a reaction force f acts on the corresponding input portion of the arm member 19 from one outer tube 6o. The total load F acting on the input unit is the sum of the initial load F ₀ of the disc spring 17 and the reaction force f.

F = F ₀ + f (1) From the balance between the load acting on the two input sections and the reaction force of the load acting on the two output sections, the following equation is established: F ₀ + F = P ₁ + P ₂ (2) From the balance of the moment around one output section (point a), the following equation is established.

[0035] _{F 0 × (d 0/2} + d / 2) -P 2 × d -F × (d 0/2-d / 2) = 0 ... (3) is satisfied.

By solving equation (3) for P ₂ , the following equation is obtained: P ₂ = {F ₀ × (d ₀ + d)} / 2d − {F × (d ₀ −d)} / 2d (4) Solving equation (2) for P ₁ yields:

P ₁ = F ₀ + FP ₂ (5) By substituting equation (1) into equation (4), the following equation is obtained: P ₂ = F ₀ − {(d ₀ −d) / 2d} × f (6) By substituting the equations (6) and (1) into the equation (5), the following equation is obtained.

P ₁ = F ₀ + {(d ₀ + d) / 2d} × f (7) As shown in the right half of FIG. 10A, the steering torque T in the right direction (that is, from the outer tube 6o) Arm member 19
When the reaction force f) is increased to act on, the load P ₂ of the load P ₁ acting on the magnetostrictive material 25R based on the equation (7) increases from an initial reaction force F ₀ linearly, acting on the magnetostrictive material 25L ( 6) Linearly decreases from the initial reaction force F ₀ based on the equation (6).

Operate the steering wheel 1 to the left to move one of the outer
When the corresponding input portion of the arm member 19 is
When the force f acts, the load acting on the magnetostrictive material 25L
P_TwoAnd the load P acting on the magnetostrictive material 25R₁Is P_Two= F₀+ ｛(D₀+ D) / 2d｝ × f (8) P₁= F₀− ｛(D₀−d) / 2d｝ × f (9) The characteristics of equations (8) and (9) are shown in FIG.
The steering torque T in the left direction is shown in the left half of FIG.
(That is, from the outer tube 7o to the arm member 19,
When the reaction force f) used increases, it acts on the magnetostrictive material 25L.
Load P_TwoIs the initial reaction force F based on equation (8).₀From linear
And the load P acting on the magnetostrictive material 25R ₁Is the formula (9)
Reaction force F based on₀Linearly decreases from

When the loads P ₂ and P ₁ acting on the magnetostrictive materials 25L and 25R from the arm member 19 increase, the magnetostrictive materials 25L and 25R increase.
FIG. 10A showing the relationship between the loads P ₂ , P ₁ and the steering torque T because the magnetic permeability of the coils L, 25R decreases, and when the magnetic permeability decreases, the output voltages VBL, VBR of the coils 24L, 24R decrease. Is converted into a graph of FIG. 10B showing the relationship between the output voltages VBL and VBR and the steering torque T.

[0041] FIG 10 As is apparent from the graph of (B), the output voltage VBR of the coil 24R which corresponds to the load P ₁ acting on one of the magnetostrictive material 25R, the output voltage V ₀ corresponding to the initial reaction force F ₀ Is a downward-sloping polygonal line (solid line shown) with the vertical axis as the intercept. Load P ₁ acting on Fundamentals and became magnetostrictive material 25R of this polygonal line, since the changes in accordance with the steering torque T when even when operating the steering wheel 1 to the right has been operated to the left, the output voltage of the coil 24R The steering torque T in both the left and right directions can be detected only from VBR. Further, as apparent from the graph of FIG. 10 (B), the output voltage VBL of the coil 24L corresponding to the load P ₂ acting on the other magnetostrictive material 25L, vertical output voltage V ₀ corresponding to the initial reaction force F ₀ It is composed of a left-downward polygonal line (shown by a broken line) as an axis intercept. Magnetostrictive material 2 on which this broken line is based
Load P ₂ acting on the 5L, since also changes in accordance with the steering torque T when the case of operating the steering wheel 1 to the right has been operated to the left, the steering torque T of the left and right directions from only the output voltage VBL of the coil 24L Can be detected.

Each of the two magnetostrictive materials 25L, 25R
The two steering torques T detected according to the change in the magnetic permeability are compared with each other.
By performing the comparison, the failure can be detected. Immediately
That is, for example, the actually detected output voltage V of the coil 24L
BL is V₁Is based on the graph of FIG.
V which is the output voltage VBR of the corresponding coil 24R _Two
Is calculated, and the calculated output voltage V_TwoIs actually detected
Output voltage V of the coil 24R_TwoDeviation from the threshold
If it exceeds, the occurrence of a failure can be detected. Reverse
In addition, the actually detected output voltage VBR of the coil 24R is
V_Two, The pair based on the graph of FIG.
V which is the output voltage VBL of the corresponding coil 24L₁Calculate
Then, the calculated output voltage V₁The carp actually detected
24L output voltage V₁Deviation exceeds threshold
In this case, the occurrence of a failure can be detected.

Now, when the steering wheel 1 is operated to the right,
Deviation P ₁ -P ₂ of a load P2 ₂ inputted to the load P ₁ and magnetostrictive material 25L to be inputted to the magnetostrictive material 25R from (6) and (7), is given by the following equation.

P ₁ −P ₂ = (d ₀ / d) × f (10) When the steering wheel 1 is operated to the left, the load P ₁ input to the magnetostrictive material 25R and the load P1 input to the magnetostrictive material 25L. Load P
Deviation P ₁ -P ₂ and _2, from (8) and (9), is given by the following equation.

P ₁ −P ₂ = (d ₀ / d) × (−f) (11) Here, the reaction force f of the axial compression force of the outer tube 7o when the handle 1 is operated to the left is Assuming that it is detected as a negative value, the expression (10) and (1)
Equation (1) can be summarized into the following equation, which is the same as equation (10).

[0046] A straight line _{P 1 -P 2 = (d 0} / d) × f ... (12) (12) Equation characteristics slope passing through the origin is _{d 0 / d, P 1 -P} 2 is anti It will be proportional to the force f. Therefore, if the deviation between the output voltage VBR of the coil 24R and the output voltage VBL of the coil 24L is calculated, the magnitude of the steering torque T can be known from the absolute value of the deviation, and the sign of the deviation indicates the magnitude of the steering torque T. You can know the direction.
Moreover, since (d ₀ / d), which is the slope of the equation (12), is a constant larger than 1, when a small steering torque T is input to the steering wheel 1, the steering torque T is changed to (d ₀ / d).
d) The detection accuracy can be increased by performing the detection twice as large.

The characteristics of the left and right magnetostrictive materials 25L and 25R vary, and the characteristics of VBR and VBR shown in FIG.
Even when the BL characteristics are not symmetrical with respect to the vertical axis, the output voltage VBR of the coil 24R shown in FIG.
And the output voltage VBL of the coil 24L has a characteristic of a straight line across the steering torque T in both the left and right directions, so that the steering torque T can be easily and accurately detected.

In the above description, it is assumed that the initial loads F ₀ , F ₀ input to both ends of the arm member 19 are equal.
(6) to (9) of the first term is a constant value F _0.
In practice, however, does not match the left and right initial load of the variations in characteristics of the disc springs 17, 17 may one initial load other initial load becomes F ₀₀ at F _0. When the side initial load acting reaction force f from one of the outer tube 6o by operating the handle 1 to the right and F _00, the load P ₁ acting on the load P ₂ and magnetostrictive material 25R acting on the magnetostrictive material 25L is , A = (F ₀ + F ₀₀ ) / 2 (13) B = (d ₀ / 2d) × (F ₀ −F ₀₀ ) (14) where P ₂ = A + B − {(d ₀ −d) / 2d} × f (15) P ₁ = A−B + {(d ₀ + d) / 2d} × f (16)

[0049] The load P ₁ acting on the load P ₂ and magnetostrictive material 25R acting on the magnetostrictive material 25L in the case of the handle 1 to the _{left, P 2 = A + B +} {(d 0 + d) / 2d} × f ... (17) P ₁ = AB − {(d ₀ −d) / 2d} × f (18) In equations (13) and (14), F
_{Assuming that 00} = F ₀ , A = F ₀ and B = 0, and (15)
Equations (18) to (18) correspond to the equations (6) to (9).

FIG. 11A shows graphs of equations (15) to (18). FIG. 11A is the same as FIG.
As Compared clear and, although the graph of showing (6) to (9) in FIG. 10 (A) ordinate intercept coincides with all F _0, shown in FIG. 11 (A) (15 ) Formula-(1)
The graph of equation 8) has two vertical intercepts, A + B and AB. The magnitude relation of A + B and AB is F ₀ and F ₀₀
The example shown in the figure is a case where F ₀ > F ₀₀ . In this case, when the steering torque T is changed to the left or right to increase or decrease the load P ₁ acting on the magnetostrictive material 25R, to increase or decrease even load P ₂ acting simultaneously magnetostrictive material 25L,
The output voltage VB of the load P ₁ of the magnetostrictive material 25R coil 24R
Graph was converted into R (solid line reference in FIG. 11 (B)), the output voltage VBL of the load P ₂ coil 24L of magnetostrictive material 25L
The steering torque T can be detected using only one of the graphs (see the broken line in FIG. 11 (B)) converted into the steering torque T.

The provision of the pair of magnetostrictive members 25L, 25R makes it possible to detect a failure by comparing the output voltages VBL, VBR of the coils 24L, 24R. For example, when the actual output voltage VBL of the detected coil 24L is V _1, and calculates V ₂ is the output voltage VBR of the coil 24R corresponding based on the graph in FIG. 11 (B), and the calculated output it can be deviations in comparison with the output voltage V ₂ of the actually detected coil 24R voltage V ₂ detects the occurrence of a failure when exceeding the threshold.
Conversely, the actually detected output voltage VBR of the coil 24R
There when in V _2, calculate the V ₁ is the output voltage VBL of the corresponding coil 24L based on the graph in FIG. 11 (B), the calculation actually detected coil 24L output voltages V ₁ and it is possible to detect the occurrence of a failure if the difference compared to the output voltages V ₁ exceeds the threshold value.

[0052] When the handle 1 is calculated from the magnetostrictive material load P ₁ and deviation of the load P ₂ of magnetostrictive material 25L of 25R when it is operated to the right (15) and (16), is as follows , P ₁ −P ₂ = − (d ₀ / d) × (F ₀ −F ₀₀ ) + (d ₀ / d) × f (19) Load of the magnetostrictive material 25R when the handle 1 is operated to the left When calculated from P ₁ and the deviation of the load P ₂ of magnetostrictive material 25L (17) and equation (18), the following equation.

P ₁ −P ₂ = − (d ₀ / d) × (F ₀ −F ₀₀ ) + (d ₀ / d) × (−f) (20) Here, the steering wheel 1 was operated to the left. If the reaction force f of the axial compression force of the outer tube 7o in this case is itself detected as a negative value, the expression (19) and (2)
Equation (0) can be summarized into the following equation, which is the same as equation (19).

P₁−P_Two=-(D₀/ D) × (F₀-F₀₀) + (D₀/ D) × f (21) The characteristic of equation (21) has a vertical axis intercept of − (d₀/ D) × (F
₀-F₀₀) And the slope is d ₀/ D, P₁−P_Two
Is proportional to the change in the reaction force f. Follow
Output voltage VBR of coil 24R and output voltage of coil 24L.
If the deviation from the force voltage VBL is calculated, the characteristic of the equation (21) can be obtained.
From which the magnitude and direction of the steering torque T can be determined.
You. Moreover, it is the inclination of the equation (21) shown in FIG.
(D₀/ D) is a constant greater than 1, so the hand
When a small steering torque T is input to
If the rudder torque T is (d₀/ D) For detection by magnifying twice
Thus, the detection accuracy can be improved.

Even when the characteristics of the left and right magnetostrictive materials 25L and 25R vary, the coil 2 shown in FIG.
4R output voltage VBR and coil 24L output voltage VBL
Since the characteristic of the deviation from this is a straight line across the steering torque T in both the left and right directions, the steering torque T can be detected simply and precisely.

Thus, the steering torque T of the steering wheel 1 is obtained.
Is detected, the steering torque T is negated, and an assist torque is generated in the power steering motor 39 so as to maintain the tension of the Bowden cables 6 and 7 at a constant level, thereby obtaining suitable power steering assist characteristics. be able to.

Thus, the steering torque T is detected by changing the magnetic permeability of the magnetostrictive members 25L, 25R by the reaction force of the axial compressive force acting on the outer tubes 6o, 7o with the operation of the handle 1. The steering torque sensor TS can be configured with a simple structure having a small number of parts and no moving parts, and it is possible to reliably detect the steering torque T with high reliability. Further, since the load obtained by amplifying the reaction force by the arm member 19 is applied to the magnetostrictive members 25L and 25R, high detection accuracy can be secured even when the steering torque T is small. Also, since the inner cables 6i, 7i do not pass through the insides of the coils 24L, 24R, the magnetostrictive material 25
The change in the magnetic permeability with respect to the change in the load acting on the L and 25R becomes large, so that even when the steering torque T is small, not only high detection accuracy can be ensured, but also the magnetostrictive material 25
The shape of L and 25R can be simplified from a cylindrical shape to a cylindrical shape, so that downsizing and cost reduction can be achieved.

Although the embodiments of the present invention have been described in detail, various design changes can be made without departing from the gist of the present invention.

For example, in the embodiment, the steering device for assisting the driver's steering force with the power steering motor 39 has been described. However, the present invention does not use the power steering motor 24 but uses the Bowden cables 6 and 7.
The present invention can also be applied to a steering device that performs manual steering only with a load transmitted via the steering wheel.

In the embodiment, the coils 24L, 24R and the magnetostrictive members 24L,
Although 25R is used, any detection unit can be adopted as long as it can detect the loads P ₁ and P ₂ of the output unit of the arm member 19.

[0061]

As described above, according to the first aspect of the present invention, when an axial compressive force acts on one of the outer tubes by operating the handle to the left or right, the arm member close to the outer tube is moved. A load is applied from one output part to the corresponding load support part by adding a constant load corresponding to the initial load and a load proportional to the reaction force of the axial compressive force. When an axial compressive force acts on the outer tube, a load proportional to the reaction force of the axial compressive force of the other outer tube from a constant load corresponding to the initial load to the corresponding load supporting portion from the one output portion. Is applied.

Therefore, even if the handle is operated in either the left or right direction, the load transmitted from the one output portion of the arm member to the corresponding load support portion is the one on the side where the axial compressive force acts at that time. It will change according to the reaction force from the outer tube. As a result, if the steering torque is detected based on the difference between the loads acting on both load supporting portions, the difference in the load is calculated as the change in the steering torque regardless of whether the steering wheel is operated to the left or right. Since it has a proportional change, the detection accuracy of the steering torque is enhanced.

[Brief description of the drawings]

FIG. 1 is an overall perspective view of a cable steering device.

FIG. 2 is an enlarged view taken on line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 2;

FIG. 5 is an enlarged view of a main part of FIG. 2;

FIG. 6 is a sectional view taken along line 6-6 of FIG. 1;

FIG. 7 is a diagram showing a steering torque detection circuit.

FIG. 8 is a view showing the balance of loads acting on arm members.

FIG. 9 is a diagram showing an input waveform and an output waveform of the steering torque detection circuit.

FIG. 10 is an explanatory diagram of a process for detecting a steering torque (when left and right initial loads are equal);

FIG. 11 is an explanatory diagram of a process of calculating a steering torque (when left and right initial loads are different).

[Explanation of symbols]

 1 Handle 3 Drive Pulley Housing 4 Steering Gear Box 6 Bowden Cable (Cable) 7 Bowden Cable (Cable) 6o, 7o Outer Tube 6i, 7i Inner Cable 12 Drive Pulley 19 Arm Member 25L, 25R Magnetostrictive Material (Load Support) 34 Follower Pulley T Steering torque WL, WR Wheel

Claims (1)

[Claims] 1. A drive pulley (12) connected to a handle (1) for rotation, and a driven pulley (34) connected to a steering gear box (4) for turning wheels (WL, WR) and rotating. , A pair of cables (6, 7) for connecting the drive pulley (12) and the driven pulley (34) and transmitting the steering torque (T), and the pair of cables (6, 7) are respectively provided with the outer tube (6o). , 7o)
And inner cables (6i, 7i),
An end of the outer tube (6o, 7o) is supported by a drive pulley housing (3) accommodating the drive pulley (12), and an inner cable (6i, 7i) is wound around the drive pulley (12). In the pair, a reaction force of the axial compression force of the outer tube (6o, 7o), which varies according to the magnitude of the tension of the inner cable (6i, 7i), and an initial load in the same direction as the reaction force are applied. Is connected to the pair of outer tubes (6o,
7o), an arm member (19) is provided, and a pair of output portions are provided between the pair of input portions of the arm member (19) in a direction connecting the pair of input portions, and
The driving pulley housing (3) is provided with a pair of load supporting portions (25L, 25R) for receiving the load from the pair of output portions, and the corresponding load supporting portions (25L, 2R) are provided from the pair of output portions.
5R) based on the difference in load transmitted to the steering wheel (1)
A steering torque detecting device for a cable type steering device, wherein a steering torque (T) input to the steering wheel is detected.