JPS6223866A - Rack and pinion type power steering device - Google Patents

Abstract

PURPOSE:To enable reduction of the size of the whole of a device and to reduce a cost, by a method wherein, through utilization of a swing level adapted to control switching of the control valve of a hydraulic type power steering, steering torque is detected as an electric amount through a strain gauge. CONSTITUTION:A titled device 1 transmits rotation of a handle 6 to a steering link 4 through a pinion 10 and a rack 5, and steers wheels 2 through a knuckle arm 3. The power of a motor 12 is transmitted to a rack 5 through a pinion 13, and exerts a steering auxiliary force. In which case, a swing lever 26, engagedly inserted in a ring part 28, is mounted on a pinion shaft 18, and the forward end thereof is coupled to a plunger 24 neutrally held by a neutral holding spring. A resistance wire strain gauge 27 is situated to a coupling part between the swing lever 26 and the plunger 24, a bridge circuit is formed with the gauge 27 and other three resistors, and the circuit is functioned as a steering torque detecting means.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a rack-and-pinion type power steering device that utilizes electric driving force, hydraulic driving force, or the like as power assist. [Prior Art] Generally, in a power steering device, a steering wheel steering torque is detected as a signal by some kind of detection means, and a power assist for the steering wheel torque is generated by a control means such as a power steering valve or a controller. For example, in a hydraulic power steering device, the steering torque is mechanically detected as a phase difference using a torsion bar, etc., and this is directly transmitted to the spool valve or rotary valve, which is the control means, to control the displacement of the valve. It is designed to distribute Hanika and Ryuse into power shillings to generate power assist l-&. On the other hand, electric or electrohydraulic power steering devices
In this case, the steering torque is detected as some kind of electrical signal.
The desired power assist is generated by sending this signal to a predetermined control device and electrically controlling the displacement groups of the electromagnetic switching valves that operate the rotation of the electric motor or the movement of the power cylinder. . As the steering torque detecting means in the latter case, examples of the conventional steering torque detecting means have been shown as typical ones. One method is to directly detect this torsion angle using a non-contact type element such as a magnetic sensor or an optical sensor, since the steering torque is proportional to the torsion angle of a torsion bar that rotates together with the steering shaft. Mat-other-
) is the displacement group of the torsion angle of the 1-1 shonbar with the neck j41
gear machine elliptical

[7] Convert to curve displacement V, and this is 1 le.
The position μ is determined by the electric signal of steering torque detection and 1.
By a detection device such as a meter or a differential variable meter,
It is something to put out. (16 Problems to be Solved by the Invention)] (1) However, in the above-mentioned steering torque detection means that uses a magnetic sensor (optical sensor), the magnetic sensor is a semiconductor, so the temperature BS'4L'j Bamboo is not good 3. In addition, 1--- version version screw 41. Angle 1 Y 2 Steering 1 ~ Lux conversion μ C The electric value U to be detected is not necessarily proportional, but it is proportional to 4. This requires an electronic circuit unit.
This has the disadvantage that the number of parts is large and complex, and failures are more likely to occur. To y et al! I/, magnetic conductor, sen (Moon, it is easily affected by chips and dirt, and these 9) Disturbance countermeasures are required.In addition, the planetary operation mechanism mentioned above Although there is a proven track record of steering torque detection means using a steering torque detection means, the disadvantage is that the structure is extremely complicated and the cost is high. (2) Next, the above-mentioned steering torque detection device One of the problems when using this in a power steering system is the drift of the zero point due to temperature. If the zero point drifts, the steering force on the left and right sides of the steering wheel becomes unbalanced, and in extreme cases, This results in a phenomenon in which the wheels move even though no steering force is applied to the steering wheel.To prevent this phenomenon, there is a method of statistically correcting the drift of the zero point (Japanese Patent Laid-Open No. 6O-18451). )
. This method is based on the idea that the steering force applied to the steering wheel is random on the left and right sides, and that after a considerable amount of time, the average value will coincide with the zero point of the steering torque. However, if we assume, for example, that the circuit is operated in one direction, this idea of left and right randomness is unreasonable and becomes a practical problem. Further, even if a temperature compensation circuit is incorporated into such a detection device, since the sensor itself does not have self-temperature compensation, a complicated electronic circuit unit is required, which poses problems in terms of reliability and cost. -4~ The present invention solves these problems, eliminates the need for a complicated electronic circuit unit, and eliminates the temperature-related
An object of the present invention is to provide a rack-and-pinion electric or electrohydraulic power steering device having a steering torque detection means that can be achieved without using complicated electronic circuits. It is. [Means for Solving the Problems] In order to achieve this objective, the present invention integrates a pinion that meshes with a rack connected to a knuckle arm of a wheel via a steering wheel and rotates together with a steering handle. a plurality of bearings rotatably supporting the pinion shaft and fitted into elongated holes in the outer race; and a neutral retaining spring slidably disposed adjacent to the pinion shaft. and a swinging lever that is fitted into the pinion shaft and whose tip end is connected to the sylanger and swings in accordance with the rotational displacement of the pinion shaft. A resistance wire strain gauge, which is a means for detecting steering wheel steering torque, is provided at the connection with the plunger, and this resistance wire strain gauge constitutes a bridge circuit together with two other resistors, and the controller receiving the detection signal controls the front wheel steering drive. It is equipped with a controller that controls an electromagnetic control valve for operating the motor or power cylinder for the motor. [Operation] (1,)j: According to the above configuration, when the steering wheel is operated to rotate the pinion shaft in either direction while a load is applied to the wheel, the wheels, knuckle arm, The steering link and rack are in one fixed state,
Since the resistance of the rack is large, the pinion shaft moves in either direction along the axial direction of the rack in this direction of rotation by the distance between the elongated hole and the bearing. At this time, the swing lever also swings, but the swing lever is deformed by receiving a reaction force from the neutral holding spring of the plunger, and the amount of this deformation is detected as a voltage by the handle steering torque detection means. (2) Furthermore, since the torque detection means is a resistance wire strain gauge forming a bridge circuit, voltage changes caused by expansion of the strain gauge etc. due to temperature can be canceled. [Example] The present invention will be described below based on an example shown in the drawings. FIG. 1 to FIG. 5 relate to the first embodiment of the present invention.
In the figure, a wheel 2 is connected to a steering link 4 via a knuckle arm 3. A rack 5 integrally formed with the steering link 4 and a pinion 10 connected from the handle 6 via an input shaft 8 are engaged in a gear box 11. The rack and pinion type steering device 1 transmits rotation of a handle 6 to a steering link 4 via a gear mechanism consisting of a pinion 10 and a rack 5, and changes the direction of left and right wheels 2. A motor 12 is provided to dynamically assist the steering force of the rack and pinion type steering device 1, and a pinion 13 attached to the end of the output shaft of the motor 12 meshes with the rack 5 to cause the rack 5 to slide. It is designed to generate power assist. The forward/reverse rotation and output control of the motor 12 are performed by processing an electric signal detected by the steering wheel torque detection mechanism 15 with the controller 16. 2 is a longitudinal sectional view of the gear box 11 portion showing the meshing state of the rack 5 and the pinion 10 and the steering torque detection mechanism 15. FIG. 3 is a longitudinal sectional view taken along the line mm in FIG. FIG. 4 is a longitudinal sectional view taken along the TV-rV arrow in FIG. 2. In FIG. 2, a pinion shaft 18 integrally formed with the pinion 10 is rotatably supported by the gear box 1 through bearings 19 and 20 arranged before and after the pinion 10. As shown in FIG. 3, the bearings 19 and 20 are
The outer races 19A and 20A of the bearing 19.20 are fitted into the elongated hole 11a formed in the gear box 11 with a gap dimension a in the left-right direction, and the inner races 19B and 20B of the bearing 19.20 are fitted into the elongated hole 11a formed in the gear box 11 with a gap dimension a. is inserted into. The steering torque detection mechanism 15 includes a swing lever 26 and a resistance line strain gauge 27, which is an example of a handle steering torque detection means. It consists of a support part 29 and a drive part 30 which are formed through and project on opposite sides. The ring portion 28 is fitted onto the pinion shaft 18, and a support pin 29a formed in a spherical shape at the tip of the support portion 29 is supported by a hole 32a of a collar 32 press-fitted into the valve block body 25. . Further, a tip portion 30a formed in a spherical shape at the tip of the drive portion 30 is fitted into a pin hole 24a formed perpendicularly to the pinion shaft 18. As shown in FIGS. 4 and 5, the strain gauges 27 are attached to both left and right side surfaces of the drive section 30 of the swing lever 26. Next, the operation of the first embodiment of the present invention will be explained. . When the wheel 2 is under load, the handle 6
When the pinion shaft 18 is rotated in either direction, the wheel 2, knuckle arm 3, steering link 4, and rack 5 are in one fixed state, and the resistance of the rack 5 is large, so that the pinion shaft 18 is rotated in this direction. Along the axial direction of the rack 5, the pinion shaft 18 moves in either direction by a gap dimension a between it and a bearing 19.20 provided in the gear box 11-. Along with this movement, the swing lever 26 moves the support pin 29
The plunger 24 is moved in the same direction as the pinion shaft 18 using a as a fulcrum, and the plunger 24 is moved against the spring force of the neutral holding spring 34. At this time, the swing lever 26 is deformed by the reaction force of the neutral holding spring 34 via the plunger 24, and the amount of this deformation is expressed as a change in the resistance value of the strain gauge 27 attached to the drive section 30 of the swing lever 26. This changed acid is detected as a voltage. Incidentally, the steering torque is proportional to the reaction force that the pinion 10 receives from the rack 5, and this reaction force is applied to the swing lever 26.
is proportional to the amount of deformation, that is, the amount of strain of the strain gauge 27. Therefore, a voltage approximately proportional to the steering torque can be obtained by the strain gauge 27, which is the steering torque detection means. In this way, the voltage change is detected by the strain gauge 27 to determine the rotational direction of the motor 12, and the power assist 1- is generated in either direction. In FIG.
Although the drive unit 6 was attached to both the left and right sides of the drive unit 30, it can also be attached to both the left and right sides of the leaf spring 5 attached to the swing lever 26 as shown in FIG. In FIG. 6, when the swing lever 26 moves, the leaf spring 51 attached to it deforms, and its left and right surfaces (the seventh
The resistance value of the strain gauges 53 and 54 attached to the strain gauges 53 and 8) changes, and this change ψ is measured as a voltage. At this time, if a bridge circuit is configured using the strain gauges 53, 54 as shown in FIG. There will be no change. However, in reality, the rate of change in resistance of the strain gauges 53 and 54 due to temperature is still not completely the same, so a voltage change occurs due to temperature, and this voltage change causes a subtle left-right imbalance in the steering force. I will let you do it. Next, a circuit configuration for compensating for this voltage change (i.e. zero point drift) using the temperature sensor 55 is shown in FIG. 1-0. This temperature sensor 55 may be of any type as long as its resistance and temperature are approximately proportional as shown in FIG. 11, and its proportionality constant (temperature coefficient of resistance) is assumed to be K. In Figure 11, R4-
R7 is a resistor for connecting the amplification factor of the operational amplifier ■C1, and R
3. VR is a resistance for setting the zero point of the steering torque in advance. The problem is to select a resistance temperature coefficient K that cancels out the voltage drift of the bridge circuit, but if the voltage drift rate per 1 degree of temperature change is ε, then the value of K is approximately = 4ε. -Rt/Rg...given by formula (1). Here, Rg is the resistance value of the strain gauge 54A, Rt is the resistance value of the temperature sensor 55, and Rg<<Rt;, K<<
Set to 1. Although the temperature sensor 55 is depicted here as a single resistor, it is of course possible to combine it with an ordinary resistor in order to obtain the required K. In addition, in FIG. 10, the temperature sensor is a strain gauge 54. Although it is attached to part A,
Other strain gauges 53A, 5 depending on the sign of the voltage drift rate f
It is possible that it may be attached to parts 3B and 54A. Note that Figures 7 to 11 are for the case of a 4-piece gauge, but
The calculation formula for K is different for the two-piece gauge shown in Figures 15 to 17 and the one-piece gauge shown in Figures 15 to 17, but
Temperature compensation is possible with the circuit shown in FIG. That is, it is sufficient to replace the other two resistors with fixed resistors r4 and r2, or replace the other three resistors with fixed resistors r1, r2, and r. FIG. 18 is a schematic diagram of a rack-and-pinion power steering system [1] in which hydraulic driving force is applied to power assist 1 instead of electric driving force in the first embodiment in which electric driving force is used as power assist force. This embodiment differs from the first embodiment in that the power assist means is different. In FIG. 18, an electric signal detected by a steering torque detection mechanism 15 equipped with a strain gauge 27, a piezoelectric element 38, etc. is input to a controller 16, and by controlling an electric control valve 40, the electric signal is attached to the rack 5. supplying hydraulic pressure to the power cylinder 23 through the conduit 41,
This provides power assist to the steering link 4. In addition, in FIG. 18, 43 is a hydraulic pump, and 45 is an oil tank. [Effects of the Invention] As described above, according to the present invention, the existing swing lever provided for switching the control valve of conventional hydraulic power steering is utilized, and the steering torque is determined by the strain gauge. Since it is detected as an electrical quantity, a complicated electronic circuit is not required, and the entire device can be made smaller and the cost of the entire device can be reduced. Furthermore, since a resistance wire strain gauge constituting the bridge circuit is provided as the steering wheel steering torque detecting means, it is possible to prevent zero point drift due to temperature without using a complicated electronic circuit unit.

[Brief explanation of drawings]

1 to 5 relate to the first embodiment of the present invention, FIG. 1 is a schematic diagram of a rack and pinion type power steering device using electric driving force as power assist, and FIG. 2 is a diagram showing a rack and pinion type power steering device. A vertical cross-sectional view of the gear box portion showing the meshing state and the steering torque detection mechanism, FIG. 3 is a vertical cross-sectional view taken along the mm--m arrow in FIG. 2, and FIG.
FIG. 5 is a partially enlarged view of the one shown in FIG. 4, and FIG.
6, FIGS. 7 and 8 are left and right side views of the leaf spring 51 in FIG. 6, and FIG. 9 is a bridge circuit constructed by the strain gauges in FIGS. 7 and 8. figure,
Fig. 10 is a diagram in which a compensation circuit using a temperature sensor is added to Fig. 9, and Fig. 11 is a diagram showing the characteristics of the temperature sensor in Fig. 10.
Figures 12 to 14 and Figures 15 to 17 show other embodiments, and figures corresponding to Figures 7 to 9 above show racks using hydraulic driving force as power assist. FIG. 1 is a schematic diagram of an and pinion type power steering device. 1... Rack and pinion type power steering device, 2... Wheels, 3... Knuckle arm,
4... Steering link, 5... Rack, 6...
Steering handle, 10... Pinion, 1, 1 a.
...Elongated hole 12...Motor, 15...Steering torque detection mechanism, 18...Pinion shaft, 19.20...Bearing, 19
A, 20A... Outer race, 23... Power cylinder, 24... Plunger, 26... Rocking lever, 27
．． 38... Strain gauge serving as a steering wheel steering torque detection means, 53.54... Strain gauge, rl, r2, r3... Fixed resistance.

Claims (2)

[Claims] (1) A pinion shaft that integrally forms a pinion that meshes with a rack connected to the knuckle arm of the wheel via a steering link and rotates together with the steering handle, and an outer race that rotatably supports the pinion shaft. a plurality of bearings fitted into elongated holes; a plunger slidably disposed close to the pinion shaft and held neutrally by a neutral holding spring; a swinging lever connected to the pinion shaft and swinging in accordance with the rotational displacement of the pinion shaft, and a resistance line strain gauge serving as a handle steering torque detecting means is provided at a connecting portion between the swinging lever and the plunger; This resistance wire strain gauge constitutes a bridge circuit together with three other resistors, and controls an electromagnetic control valve for operating the front wheel steering motor or power cylinder associated with the rack based on the detected value of the steering wheel steering torque. A rack and pinion type power steering device characterized by being provided with a controller for controlling the device. (2) The rack and pinion type power steering device according to claim 1, characterized in that all the other three resistors are also resistance wire strain gauges.