JPH10316000A - Steering wheel angle compensation device in power steering device and vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate a deviation in the corresponding relations of a steering wheel angle and a cut angle of a steering wheel by producing an idling condition of handling without causing inconveniences even when handling is done at a low speed so as to increase a chance of the compensation of a deviation. SOLUTION: When a CPU in a controller 26 detects a deviation between the current steering wheel angle detected by a steering wheel angle sensor 30 and the target steering wheel angle obtained from the tire cut angle R detected by a tire angle sensor 28, it opens a solenoid valve 22 at the time of handling to create an idling condition of handling so as to compensate the deviation. As an orbit roll 4 which discharges an oil amount which corresponds to a rotation amount of a steering wheel 2, the orbit roll of low slip type which increases the discharge efficiency in a steering wheel low speed rotation region is used. The opening of the solenoid valve 22 is inhibited only when vehicle speed detected by a vehicle speed sensor 35 is in a condition in which it is regarded as a vehicle stop condition, even if steering wheel rotation speed is low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering angle correcting device for a power steering device for correcting a deviation of a correspondence relationship between a steering wheel steering angle and a steering wheel turning angle in a vehicle such as a forklift equipped with a power steering device. And vehicles.

[0002]

2. Description of the Related Art Conventionally, as a power steering device,
2. Description of the Related Art An all-hydraulic power steering apparatus that supplies an amount of oil corresponding to an operation amount of a steering wheel to an actuator such as a steering cylinder to steer a steered wheel is known.

For example, in an industrial vehicle such as a forklift,
A knob is provided on the handle so that the handle can be operated by one hand with the other hand while performing the cargo handling operation. Therefore, the position of the knob may be used as a guide for determining whether or not the steered wheels are at the turning angle when the vehicle is traveling straight. However, the orbit roll efficiency (actual discharge amount / theoretical discharge amount) indicating the correspondence between the operation amount of the handle and the amount of oil discharged from the hydraulic oil supply device such as an orbit roll fluctuates with respect to the handle operation speed. Due to an oil leak or the like in a hydraulic system such as a steering cylinder, a deviation occurs in the correspondence between the knob position and the steering wheel turning angle.

[0004] For example, Japanese Patent Publication No. 3-30544, Japanese Patent Publication No. 4-24270, and Japanese Utility Model Publication No. 7-5364 disclose a steering wheel angle correction device for correcting a deviation of a steering wheel angle from a steering angle of a steered wheel. Have been.

FIG. 14 shows a steering wheel angle correcting device disclosed in Japanese Utility Model Publication No. 7-5364. The all-hydraulic power steering device 51 includes a steering unit 54 having a PS control valve 53 operated by a handle 52, a steering cylinder 55 for steering a steered wheel (not shown), a steering unit 54 and a steering cylinder 55. Hydraulic line 56 connecting the
57. The hydraulic lines 56 and 57 are
During steering according to the second operation direction, one of the lines serves as a supply line for supplying pressurized hydraulic oil from the hydraulic pump 58, and the other line serves as a return line for returning oil to the tank 59. In the middle of both hydraulic lines 56 and 57, an electromagnetic control valve 6 is provided.
0 is provided.

The controller 61 receives a handlebar rotation angle signal θabs from a handlebar position sensor 62 and a cylinder stroke signal s from a cylinder position sensor 63. The controller 61 outputs the steering wheel rotation angle signal θabs
From the signal s, the target cylinder stroke xg and the target cylinder stroke x
When the deviation from g exceeds an allowable value, the electromagnetic control valve 60 is opened.

When the electromagnetic control valve 60 is opened,
A portion of the hydraulic oil flows from one supply line of the hydraulic lines 56 and 57 to the other return line to the tank 59, the handle 52 idles, and the handle has a regular steering wheel angle corresponding to the steering angle of the steered wheels. Until the correction is made, the deviation of the steering wheel is corrected.

By the way, there are two types of orbit rolls, a standard type and a low slip type. FIG.
5 is a graph showing the orbit roll efficiency of each type of orbit roll with respect to the handle rotation speed. In the standard type, as shown by the line A, the orbit roll efficiency becomes sharply smaller than 100% due to oil leak in a low speed range of the handle rotation speed. On the other hand, the low-slip type has an orbit roll efficiency of 100% due to oil leak from the outside in the low-speed range of the handlebar rotation speed as indicated by the line B.
It grows rapidly from.

In the conventional device, a standard type orbit roll is used. Therefore, in order to prevent deterioration of the feeling that the steering wheel is hard to be turned when the steering wheel is rotated at a low speed, the steering wheel is displaced when the steering wheel rotation speed is low. The correction was not performed. That is, the detection value of the steering wheel position sensor 62 is differentiated by a differentiating circuit to generate a speed signal proportional to the steering wheel rotation speed. When it is determined from this speed signal that the steering wheel rotation speed is lower than the set value, the deviation of the steering wheel is determined. The correction was not performed.

[0010]

By the way, if the low slip type is used, the discharge rate of the oil amount exceeds 100% in the low speed range of the handlebar rotation speed, so that this kind of deterioration in the handle operation feeling is deteriorated. Since there is no fear of inviting the steering wheel, the correction is executed even when the steering wheel is operated at a low speed, and it can be expected that the chance of correcting the deviation of the steering wheel is effectively increased.

However, when the steering wheel is turned with the vehicle stopped, the tire is twisted due to a large frictional resistance between the tire and the road surface. When the tire is twisted, the electromagnetic control valve is opened to correct the steering wheel displacement. At this time, if the hydraulic pressure in the steering cylinder drops to a level that cannot counteract the torsional return force of the tire, the tire will return to twist. This may cause a problem that the execution of the shift correction increases the shift of the steering wheel.

FIG. 17 is an explanatory diagram for explaining such a phenomenon. In the same drawing, the steering wheel idles only when the knob 52a is operated in a direction in which the current knob position (open circle) approaches the target knob position (black circle) determined by the steering angle of the steered wheel in the shortest path. A control method for opening a solenoid valve for producing a valve will be described as an example.

First, as shown in FIG. 17 (a), when the steering wheel is operated in the direction of the arrow while the vehicle is stopped, the tire is twisted, and the target knob position when the tire is not twisted (hatched area is hatched). The apparent target knob position is located at a position rotated leftward by an angle corresponding to the twist of the tire from the circle). When the steering wheel is operated in the twisting direction (the direction of the arrow) of the tire from this state, the knob 52a
The solenoid valve is opened because the current knob position is in the direction approaching the target knob position. At this time, since the return speed of the torsion of the tire is high, even if the solenoid valve is closed when the deviation falls within the allowable value, the target knob position deviates from the current knob position as shown in FIG. It just passes by. When the handle is turned back from this state as shown in FIG. 17C, the solenoid valve is opened again because the direction is approaching again from the current knob position of the knob 52a to the target knob position. As a result, FIG.
As shown in FIG. 7 (d), the tire is cut in the direction of returning the twist, the target knob position is separated from the current knob position, and the deviation is increased. As shown in FIG. 17E, when the steering wheel is turned again from the state where the deviation has been enlarged, the enlarged deviation remains. In such a configuration using the low-slip type orbit roll, there is a case where the execution of the correction may cause a problem that the positional deviation of the knob 52a is enlarged.

[0014] Even when the low slip type is used, if the solenoid valve is opened while the handle is being operated at a low speed, the opening of the solenoid valve may rather increase the knob displacement. Had become. For this reason, even when the low-slip type is used, there has been a problem that when the handle operation speed is low, the knob displacement correction must be stopped as in the standard type.

Further, when the vehicle is turning, the angles formed by the arms of the links connected to the kingpin supporting the steered wheels are different between left and right, so that different moments act on the left and right steered wheels. For this reason, when the steering wheel is operated at a low speed during traveling turning, the solenoid valve opens, and if the hydraulic pressure enough to oppose the difference in the left and right moments of the steered wheels is no longer ensured in the steering cylinder, the steered wheels are cut off. Happens. Due to this notch phenomenon, the opening of the solenoid valve may rather increase the deviation.

FIG. 16 is an explanatory diagram for explaining a phenomenon in which the opening of the solenoid valve is rather increased due to the notch phenomenon, and the positional deviation of the knob is enlarged. As shown in FIG. 16A, a force (indicated by a white arrow in this drawing) acts on the tire due to a moment difference between the left and right steered wheels during traveling turning. As shown in FIG. 16B, when the handle is operated at a low speed in the direction in which the current knob position of the knob 52a approaches the target knob position (in the direction of the arrow in FIG. 16), the solenoid valve is opened. At this time, if the hydraulic pressure in the steering cylinder drops so as not to be able to oppose the cutting force acting on the steered wheels, FIG.
As shown in (5), the steered wheels are cut in the notch direction, the target knob position moves away from the current knob position, and the shift of the knob 52a increases. The notch force acting on the steered wheels is not as large as the return force of the twisted tire when the vehicle is stopped, but it has also been one of the causes of increasing the deviation due to the opening of the solenoid valve.

The present invention has been made in view of the above-mentioned problems, and a first object of the present invention is to prevent a tire from being twisted when the vehicle is stopped when a low-slip type hydraulic oil supply device is used. In the power steering device, it is possible to prevent a problem in which the execution of the steering wheel deviation correction increases the steering wheel deviation and to execute the steering wheel deviation correction without a problem even at a low rotation speed of the steering wheel, thereby increasing a chance of the deviation correction. An object of the present invention is to provide a steering wheel angle correction device and a vehicle. A second object is to make the detection data of the turning angle available for detecting a low-speed operation of the steering wheel. A third object is that when a low-slip type hydraulic oil supply device is used, not only the twisting of the tires at the time of stopping but also the turning of the steered wheels at the time of running turn, the execution of the correction of the steering wheel deviation is rather difficult. In other words, it is possible to prevent the problem of increasing the displacement of the steering wheel, perform the displacement correction of the steering wheel without any trouble even at a low rotation speed of the steering wheel, and increase the opportunity for the displacement correction. A fourth object is to reduce unnecessary idling of the steering wheel when correcting the deviation of the steering wheel. A fifth object, in addition to the second object, is to prevent a feeling of steering wheel operation from being deteriorated due to a notched phenomenon of a steered wheel. A sixth object is to use data used for steering wheel displacement correction for detecting the behavior of a steered wheel.

[0018]

According to the first aspect of the present invention, in order to achieve the first object, an oil amount is discharged in accordance with a rotation amount of a handle, and the oil amount is discharged in a low speed range of the handle rotation speed. In a power steering device including a low-slip type hydraulic oil supply device whose ratio increases, and an actuator driven by hydraulic oil discharged from the hydraulic oil supply device to steer a steered wheel, the power steering device includes: Correction means for returning a part of the discharged hydraulic oil to create an idling state of the steering wheel, low-speed steering detection means for detecting that the steering wheel rotation speed is lower than a predetermined value, and A stationary state detecting means for detecting a state in which the vehicle can be considered to be in a stopped state in which the road surface frictional resistance becomes greater than or equal to a predetermined value; Even if it is detected that the vehicle is at a low speed, if the stop state detecting means does not detect that the vehicle is in a state in which it can be regarded as a stopped state, the deviation of the correspondence between the steering wheel angle of the steering wheel and the steering angle of the steering wheel is detected. And control means for driving the correction means when the steering wheel is operated in the direction for correcting the deviation.

In order to achieve the second object, according to the second aspect of the present invention, in the first aspect, the low-speed steering detecting means includes a turning angle speed detecting means for detecting a turning angle velocity of the steered wheels. The gist of the invention is to indirectly detect that the handlebar rotation speed is low based on the turning angle speed detected by the turning angle speed detecting means.

In order to achieve the third object, according to the third aspect of the present invention, a low-slip type in which an amount of oil is discharged in accordance with the amount of rotation of the handle and the discharge ratio increases in a low-speed range of the handle rotation speed. A hydraulic oil supply device, and an actuator driven by the hydraulic oil discharged from the hydraulic oil supply device to steer the steered wheels. Correction means for recirculating the section to create an idling state of the steering wheel, and a steering wheel which is considered to have a possibility of widening a deviation of a correspondence relationship between a steering wheel angle of the steering wheel and a steering angle of the steering wheel when the correction means is driven. A wheel behavior detecting means for detecting a behavior, and detecting a deviation of a correspondence relationship between a steering wheel steering angle and a steering wheel steering angle, and operating the steering wheel in a direction to correct the deviation. Together with the driving of the correction means when it is, when the wheel behavior detecting means during the operation of the correction means detects the behavior of the steering wheel and a control means for stopping the driving of said correction means.

According to a fourth aspect of the present invention, in order to achieve a fourth object, in the third aspect of the invention, the control means includes a handle angle detecting means for detecting a handle angle of the handle based on a handle relative angle. Steering angle detection means for detecting the steering angle of the steered wheels, the steering wheel in a direction in which the current steering wheel angle detected by the steering wheel angle detection means approaches the target steering wheel angle determined by the steering wheel relative angle from the steering angle in the shortest path The gist is that the correction means is driven only when is operated.

According to a fifth aspect of the present invention, in order to achieve a third object, in the fourth aspect of the present invention, the wheel behavior detecting means includes a steering wheel which is turned in a direction opposite to a steering wheel operating direction. The gist of the present invention is to detect at least a second behavior among one behavior and a second behavior in which the steered wheel is turned more than a turning amount corresponding to a steering wheel operation amount.

According to a sixth aspect of the present invention, in order to achieve a fifth object, in the invention of the fifth aspect, the wheel behavior detecting means detects both the first behavior and the second behavior. That is the gist.

In order to achieve the sixth object, according to the invention described in claim 7, in the invention described in claim 5 or claim 6, the wheel behavior detecting means sets the target steering wheel angle closer to the steering wheel angle. In view of this, the gist is that the first behavior is performed, and the second behavior is detected based on the spread of the deviation.

According to an eighth aspect of the present invention, the vehicle is provided with the steering wheel angle correcting device according to any one of the first to seventh aspects. (Operation) Therefore, according to the first aspect of the present invention, the vehicle stop state detecting means detects a state in which the road surface frictional resistance at the time of steering of the steered wheels can be regarded as a stop state of the vehicle which is larger than a predetermined value. Further, the low-speed steering detecting means detects that the handlebar rotation speed is low, which is lower than a predetermined value. If the steering wheel rotation speed is not low, if the deviation of the correspondence between the steering wheel angle of the steering wheel and the steering angle of the steering wheel is detected,
The control means drives the correction means when the steering wheel is operated in the direction for correcting the deviation. As a result, part of the hydraulic oil discharged from the hydraulic oil supply device in response to the operation of the steering wheel is recirculated, and an idling state of the operation of the steering wheel is created, thereby correcting the deviation. On the other hand, even if the rotation speed of the steering wheel is low, if the vehicle cannot be regarded as being in a stopped state, the control means drives the correction means when the steering wheel is operated in a direction for correcting the deviation. The correction means is not driven only when it is detected that the steering wheel rotation speed is low and the vehicle can be regarded as stopped. In other words, the steering wheel is operated at low speed in a state where the vehicle can be regarded as stopped,
When there is a possibility that the tire is twisted, the driving of the correcting means is effectively prohibited. Therefore, it is possible to prevent a problem that the correction of the steering wheel displacement which may be caused by the twisting of the tire when the vehicle is stopped is rather increased and the deviation of the steering wheel is enlarged.
Therefore, even when the rotation speed of the steering wheel is low, opportunities for correcting the deviation of the steering wheel are increased.

According to the second aspect of the present invention, the low-speed steering detecting means indirectly detects that the steering wheel rotational speed is low from the turning angle speed of the steering wheel detected by the turning angle speed detecting means. That is, the detection data of the turning angle is used for detecting the low-speed operation of the steering wheel.

According to the third aspect of the present invention, when the deviation of the correspondence between the steering wheel angle of the steering wheel and the steering angle of the steered wheels is detected, when the steering wheel is operated in the direction to correct the deviation, the control means is activated. The correction means is driven. As a result, part of the hydraulic oil discharged from the hydraulic oil supply device in response to the operation of the steering wheel is recirculated, and an idling state of the operation of the steering wheel is created, thereby correcting the deviation. If the steering wheel behaves in such a manner that the deviation of the steered wheels may increase when the correction device is driven, the behavior is detected by the wheel behavior detecting device. The control means stops driving of the correction means when the behavior is detected by the wheel behavior detection means. For example, when the vehicle is stopped with the tire being twisted, the correcting means is driven, and if the turning of the steered wheels when the torsion of the tire returns is detected as a behavior that widens the deviation, the driving of the correcting means is immediately stopped. For this reason, it is possible to prevent a problem that the correction of the steering wheel displacement that may be caused by the twisting of the tire at the time of stopping the vehicle rather than increasing the deviation of the steering wheel is prevented.

Further, if the steering wheel is operated in a direction for correcting the deviation detected during the turning of the vehicle, the correcting means is driven by the control means. During this traveling turn, a force in the notch direction is applied to the steered wheels due to the difference in moments acting on the left and right steered wheels, and the behavior that the steered wheels may spread out due to the force in the notch direction when the drive means is driven. Then, immediately after this behavior is detected by the wheel behavior detecting means, the driving of the correcting means is stopped. For this reason, it is also possible to prevent a problem that the execution of the correction of the deviation of the steering wheel during the traveling turning increases the deviation of the steering wheel.

According to the fourth aspect of the invention, the control means detects the steering wheel angle of the steering wheel by the steering wheel relative angle by the steering wheel angle detecting means, and detects the turning angle of the steering wheel by the steering angle detecting means. Then, the correction means is driven when the steering wheel is operated in a direction in which the current steering wheel angle approaches the target steering wheel angle determined by the steering wheel relative angle from the current steering angle in the shortest path. That is, only the apparent deviation of the steering wheel is corrected in consideration of only the relative angle of the steering wheel, not the actual deviation of the steering wheel. Therefore, even when the steering wheel is displaced by one or more rotations, it is sufficient to correct the apparent deviation amount by less than one rotation, and when the steering wheel is displaced by more than half a rotation in less than one rotation, it is shifted by one rotation. The correction is performed with a correction amount smaller than the actual deviation amount.

According to the fifth aspect of the present invention, the wheel behavior detecting means includes a first behavior in which the steered wheel is turned in a direction opposite to the steering wheel operating direction, and a steering wheel having a steering angle larger than the steering amount in accordance with the steering wheel operating amount. At least the second behavior
Detect behavior. For this reason, at the time of detecting the second behavior in which the steered wheels are turned more than the turning amount corresponding to the steering wheel operation amount, at least when the correcting means is driven and the idle state of the steering wheel is created, at least the correcting means is operated. Driving is stopped. Therefore, an increase in the deviation between the steering wheel angle and the target steering wheel angle due to the driving of the correcting means is at least suppressed.

According to the invention described in claim 6, the wheel behavior detecting means detects both the first behavior and the second behavior. The control means stops driving of the correction means when detecting either one of the first behavior and the second behavior. For this reason, the turning phenomenon of the steered wheels during the turning is reliably suppressed, and the feeling of the steering wheel operation during the turning is preferably maintained.

According to the seventh aspect of the present invention, the wheel behavior detecting means detects the first behavior when the target steering wheel angle approaches the steering wheel angle, and detects a deviation between the target steering wheel angle and the steering wheel angle. The second behavior is detected by spreading.

According to the invention described in claim 8, the vehicle is provided with the steering wheel angle correcting device according to any one of claims 1 to 7, so that the vehicle is provided with any one of claims 1 to 7 The same effect as the invention described in one aspect is obtained.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows a power steering device 1 mounted on a forklift F as a vehicle. A steering wheel (steering wheel) 2 that is rotated by an operator is provided with a knob 2a for improving the operability. The steering shaft 3 supporting the handle 2 is connected to an orbit roll 4 as a hydraulic oil supply device. The orbit roll 4 is a low-slip type in which the orbit roll efficiency exceeds 100% in a low speed range of the handle rotation speed.

A valve unit 5 constituting the orbit roll 4 has a supply pipe 7 through which hydraulic oil from a hydraulic pump (loading pump) 6 driven by an engine (not shown) is supplied and a drain tank 8. A discharge pipe 9 for discharging oil is connected. A relief valve 11 is interposed in a conduit 10 connecting the supply pipe 7 and the discharge pipe 9, and the relief valve 11 keeps a hydraulic pressure fed from the hydraulic pump 6 to the valve unit 5 at a constant pressure (set pressure). It has become so.

The valve unit 5 is driven directly by the steering shaft 3 and has a function of supplying an oil amount proportional to the rotation amount of the handle 2 to a steering cylinder 12 as an actuator described later. The valve unit 5 and the steering cylinder 12 are connected by two hydraulic lines 13 and 14. When the handlebar 2 is turned to the right, the hydraulic line 13 functions as a supply line for supplying hydraulic oil from the hydraulic pump 6 and the hydraulic line 1
4 functions as a return line for returning hydraulic oil to the hydraulic pump 6. When the handlebar 2 is turned to the left, the hydraulic line 14 functions as a feed line, and the hydraulic line 13 functions as a return line.

The steering cylinder 12 includes a hollow cylindrical cylinder tube 15 fixed to the vehicle body, a piston 16 reciprocally disposed therein, and a pair of left and right pistons extending from both ends of the cylinder tube 15. Rods 17a and 17b are provided. Each hydraulic line 1
Each of the cylinders 3 and 14 is communicated with each chamber of a cylinder tube 15 divided into two chambers by a piston 16.

Left and right steering wheels (rear wheels) 19, 19 are connected to the distal ends of the piston rods 17a, 17b via link mechanisms 18a, 18b. The wheels 19 are steered left and right about the kingpin 20.

The hydraulic lines 13 and 14 are connected by a bypass line 21, and an electromagnetic valve (electromagnetic switching valve) 22 and a throttle valve 23 are provided in the middle of the bypass line 21 as correction means. The solenoid valve 22 returns a part of the oil amount discharged from the valve unit 5 to the drain tank 8 through the bypass line 21 by opening the valve, and the displacement amount of the piston 16 in the steering cylinder 12 with respect to the operation amount of the steering wheel 2 This is for reducing the ratio to create an idling state of the steering wheel 2. By causing the steering wheel angle to catch up with a regular angle corresponding to the steering angle of the steered wheels 19 by the idling of the steering wheel operation, the deviation of the correspondence between the steering wheel angle and the steering angle is corrected.

The solenoid valve 22 is a normally closed type two-position switching valve. A spool (not shown) constituting the solenoid valve 22 is urged by a spring 24 toward the blocking position. The solenoid valve 22 is arranged at a shut-off position (the state shown in FIG. 1) for shutting off the bypass line 21 when the solenoid 25 is demagnetized, and is arranged at a communication position for making the bypass line 21 communicate when the solenoid 25 is excited. . Excitation and demagnetization of the solenoid 25 are controlled by a controller 26.
The solenoid valve 22 is normally kept in a shut-off state, and is opened when correcting the deviation of the correspondence between the steering wheel angle and the steering angle. The throttle valve 23 is for reducing the flow rate of the bypass line 21 so that the steering wheel 19 can be steered by operating the steering wheel even if the solenoid valve 22 remains open due to a failure or the like. .

The controller 26 includes an encoder (rotary encoder) 27 constituting a steering wheel angle detecting means.
And a tire angle sensor 28 that constitutes a low-speed steering detection unit, a turning angle speed detection unit, and a wheel behavior detection unit, and is a steering angle detection unit. The encoder 27 includes a disk 29 provided so as to be rotatable integrally with the steering shaft 3, and a handle angle sensor 30 including three sets of photocouplers for detecting light passing through slits of the disk 29. A detection signal from the steering wheel angle sensor 30 is input to the controller 26.

The steering angle sensor 30 includes a first transistor 31, a second transistor 32, and a correction transistor 3 which are phototransistors constituting the photocoupler.
3 (shown in FIG. 2). The first transistor 31 and the second transistor 32 are for detecting light passing through a total of 40 slits formed at equal intervals along the circumferential direction of the disk 29, and are turned on by one rotation of the handle 2. Outputting detection signals (digital signals) SS1 and SS2 shown in FIG. Each transistor 31, 32 has its own output signal SS
The rotation angle of the steering wheel 2 (hereinafter referred to as the steering wheel angle) is determined by detecting the edges of both signals SS1 and SS2.
Detection is possible at a resolution equivalent to 160 divisions of one rotation of the handle.

The correction transistor 33 is for detecting light passing through a position correcting slit formed at one peripheral portion of the disk 29. When the handle 2 is placed at the neutral position, the correction transistor 33 detects a light passing through the slit and outputs a detection signal (digital signal) SSC shown in FIG. The output signal SSC from the correction transistor 33 includes the signals SS1 and SS
It is used for calibration of a count value C, which will be described later, corresponding to a steering wheel angle obtained by counting edges of 2.

The tire angle sensor 28 comprises a potentiometer in this embodiment. The tire angle sensor 28 is fixed to the right end of the rear axle beam so that its detection axis can rotate integrally with a king pin 20 that supports the right steering wheel 19. The tire angle sensor 28 detects the turning angle of the steering wheel 19 by detecting the amount of rotation of the king pin 20, and outputs a tire turning angle signal R corresponding to the turning angle to the controller 26.

A front differential ring gear 34 for transmitting an output from an engine (neither is shown) to left and right front wheels as driving wheels is provided with a vehicle speed sensor 3 as a stopped state detecting means.
5 are provided. The vehicle speed sensor 35 outputs to the controller 26 a vehicle speed signal v having a frequency proportional to the rotation speed of the front differential ring gear 34, that is, the vehicle speed.

As shown in FIG. 2, the controller 26
Microcomputer 36, edge detection circuit 37, AD
It is provided with conversion circuits 38 and 39, an excitation / demagnetization drive circuit 40 constituting control means, and the like. Microcomputer 36
Are control means, low-speed steering detection means, turning angle speed detection means,
Central processing unit (CPU) 4 constituting wheel behavior detecting means
1, a read only memory (ROM) 42, a read / write rewritable memory (RAM) 43, a steering counter 44 constituting a steering wheel angle detecting means, a control cycle counter 45, a clock circuit 46, an input interface 47 and an output interface 48. ing.

The CPU 41 executes various arithmetic processes based on various program data stored in the ROM 42, and stores the arithmetic results in the RAM 43. The ROM 42 stores program data for the knob position correction control processing shown in the flowcharts of FIGS.

Each detection signal SS from the first transistor 31, the second transistor 32 and the correction transistor 33
1, SS2 and SSC are input to the CPU 41 via the input interface 47, and the edge detection circuit 3
7 is input. Edge detection circuit 37
Is for detecting the rising and falling edges of the detection signals SS1, SS2, SSC, and outputs the edge signals SE1, SE2, SEC when the edge is detected. Therefore, the CPU 41 alternately inputs the edge signals SE1 and SE2 each time the handle 2 rotates 1/160 (= 2.25 °).

The steering counter 44 is for counting the steering wheel angle θ of the steering wheel 2. Each time the CPU 41 inputs the edge signals SE1 and SE2, that is, every time the steering wheel 2 is rotated 1/160, the count value C of the steering counter 44 is changed by "1". Therefore, the steering counter 44 counts the position of the knob 2a (the steering wheel angle θ) at the steering wheel relative angle where one rotation is a count value C of “0 to 159”. In the steering counter 44, the count value C when the knob 2a is located at the neutral position (a normal knob position when the steered wheels 19 are in the straight traveling state) is set to "80", and the knob 2a is at the neutral position. The count value C is calibrated to “80” every time the edge signal SEC that detects the arrangement is input.

The CPU 41 executes the knob position correction control processing shown in FIGS. 6 and 7 at intervals of a predetermined time to (for example, 10 milliseconds) based on the clock signal from the clock circuit 46. However, when the edge signals SE1 and SE2 are input, the interrupt routine shown in FIG. 8 is executed with priority, and when the edge signal SEC is input, the calibration of the count value C of the steering counter 44 is executed by an interrupt process.

The control cycle counter 45 counts the number of executions of the knob position correction control processing, and each time the count value C of the steering counter 44 is changed, that is, each time the steering wheel 2 is rotated by 1/160. Is cleared. The count value C1 of the control cycle counter 45 is used to determine whether the steering operation is stopped.

The interrupt routine shown in FIG. 8 is for detecting the rotation direction (operating direction) of the steering wheel 2, counting the steering counter 44, clearing the control cycle counter 45, and determining whether to stop the steering wheel operation. is there. The operation direction of the handle 2 is determined by the signals SS1, SS2, SE1,
Using SE2, two-phase signal SS shifted by 90 °
1, SS2. That is, FIG.
As shown in FIG. 5, when the phase of the signal SS1 is delayed by 90 ° from the phase of the signal SS2, “right steering” is performed. When the phase of the signal SS1 is advanced by 90 ° from the phase of the signal SS2, “left steering” is performed. Is determined.

The tire angle signal R from the tire angle sensor 28 is supplied to an 8-bit AD value (0
To 255) to the CPU 41, and the CPU 41 takes in the inputted AD value as the tire turning angle R. In the present embodiment, the input value from the tire angle sensor 28 is such that the AD value = “128” is associated with the tire turning angle R = “0 °” when traveling straight, and the AD value <128 (that is, the R value is “ Negative)) when left steering (left turning angle), AD value> 128
Right steering (ie, right turning angle) when the R value is “positive”
Recognize.

The vehicle speed signal v from the vehicle speed sensor 35 is input via the AD conversion circuit 39. This signal is a pulse signal having a frequency proportional to the vehicle speed.
Numeral 1 counts the number of pulses per unit time of the pulse signal to obtain an 8-bit AD value (0 to 255) proportional to the vehicle speed. In addition, a control signal for exciting / demagnetizing the solenoid 25 is output from the CPU 41 to the exciting / demagnetizing drive circuit 40 connected to the output interface 48.

The map M1 shown in FIG. 4 is stored in the ROM 42. The map M1 is for obtaining a target steering wheel angle θg represented by a steering wheel relative angle, which is a target position for correcting the position of the knob 2a, from the tire turning angle R. The control target line L that associates the tire turning angle R with the target steering wheel angle θg is an ideal control line on the assumption that the orbit roll efficiency (actual discharge amount / theoretical discharge amount) is 100%. The steering wheel angle θ when the knob 2a is at the neutral position is set to “0 °”, and the steering wheel angle θ is detected in the range of “−180 ° to 180 °”. In the present embodiment, the count value C of the steering counter 44
From the target steering wheel angle θg
Of the target steering count value Cg
"0-159".

In the knob position correction control process, the CPU 41 calculates a deviation δ between the current steering wheel angle θ and the target steering wheel angle θg obtained from the tire turning angle R, and this deviation δ is set to an allowable value δo (for example, about 5 °) Execute the knob position correction so that it falls within the range. Here, the deviation amount δ means a deviation amount between the current knob position and the target knob position in the shortest path in FIG. 5, and is distinguished from a deviation Δθ (= | θ−θg |) described later. is there.

The knob position correction is performed only when the handle 2 is operated such that the current knob position approaches the target knob position by the shortest path as shown in FIG. That is, the steering wheel operation direction (hereinafter, referred to as the target direction) for executing the correction is different from the position 180 ° from the target knob position, and the correction is performed only when the operation direction of the steering wheel 2 matches the target direction. . Therefore, when the current knob position and the target knob position are in a positional relationship as shown in the figure, the correction is executed when the handle 2 is operated in the direction of the solid line arrow in the figure, and is corrected in the direction of the broken arrow in the figure. Is not performed when the handle 2 is operated.

In this embodiment, the tire angle sensor 2
.DELTA.R (= .vertline.R-R), which is the deviation between the current detection value R from the current detection value R8 and the detection value R1 before a predetermined time.
1 |), the steering wheel operating speed VH is indirectly determined.
In the present embodiment, since the low-slip type orbit roll 4 is used, even if the solenoid valve 2 is opened when the handle operation is at a low speed, there is no fear of impairing the feel of the handle operation. Even if the operation speed is low, the opening of the solenoid valve 22 is permitted in principle. However, in a state in which the vehicle can be regarded as a vehicle stop state at a predetermined vehicle speed or less where there is a possibility that a considerable amount of torsion may occur in the tire 19a due to frictional resistance with the road surface when turning the steered wheels 19, the steering wheel operating speed may be low. For example, opening of the solenoid valve 22 is prohibited.

In this embodiment, the vehicle speed "2 km / h" or less is set as a state in which the vehicle can be regarded as stopped, and when the steering wheel operating speed VH is less than 0.3 rps, the steering wheel operating speed is set to a low state. The tire turning angle speed ΔR is the set value ΔR corresponding to the steering wheel operating speed VH = 0.3 rps.
When the speed is less than min, it is determined that the steering operation speed is low.

The vehicle speed that determines the state in which the vehicle can be considered to be in the stopped state is a vehicle speed at which the frictional resistance with the road surface does not become large enough to generate a not-to-negligible torsion due to the knob position correction processing when turning the steered wheels 19. Often, "2km /
h "is not limited to the following, and if necessary, for example, 0 to 5 km
A value equal to or less than the set value within the range of / h can also be set. Further, the rotation speed at which the steering wheel operating speed is regarded as low is a value at which the hydraulic pressure enough to overcome the torsional return force generated on the tires of the steered wheels 19 in the state where the vehicle can be regarded as stopped can be secured in the steering cylinder 12. All right,
Not limited to less than "0.3 rps", for example, 1/5 to 1
A value less than the set value within the range of / 3 rps can also be set. In the present embodiment, measures are taken to prevent the steering wheel 19 from being cut due to a moment difference acting on the left and right steering wheels 19 by prohibiting the opening of the solenoid valve 22 during the turning.

Next, the operation of the power steering device 1 will be described. When operating the forklift F,
The operator operates the handle 2 while holding the knob 2a.
When the steering wheel 2 is operated and the steering shaft 3 is driven to rotate, an oil amount corresponding to the operation amount of the steering wheel 2 is supplied from the valve unit 5 to the steering cylinder 12, and the steering wheel 19 is operated according to the operation amount of the steering wheel 2. Steered. The knob 2a may deviate from the normal position due to a decrease in the orbit roll efficiency when the steering wheel operating speed is low or an oil leak in a hydraulic system such as the steering cylinder 12. Therefore, knob position correction control for correcting the position of the knob 2a to a normal position corresponding to the tire turning angle is performed. Hereinafter, the knob position correction control executed by the CPU 41 will be described with reference to the flowcharts shown in FIGS. It is assumed that the solenoid valve 22 is closed in the initial state.

While the engine of the forklift F is being driven, CP
U41 is a detection signal SS1, SS2, SSC from each of the transistors 31, 32, 33, an edge signal SE1, SE2, SEC from the edge detection circuit 37, a tire turning angle signal R from the tire angle sensor 28, a vehicle speed sensor. The vehicle speed signal v from the controller 35 is input.

The CPU 41 executes the knob position correction control processing shown in FIGS. 6 and 7 every predetermined time to (for example, 10 milliseconds). When the edge signals SE1 and SE2 are input during the execution of the knob position correction control processing, the interruption routine shown in FIG. 8 is preferentially executed, and the steering counter 44 counts data necessary for executing the knob position correction. In addition, a calculation process for determining an operation direction of the steering wheel 2, a steering wheel operation stop determination process, and a clearing process of the control cycle counter 45 are executed. Each time the knob position correction control process shown in FIGS. 6 and 7 is started, a count process for incrementing the count value C1 of the control cycle counter 45 is performed in step 10, and the count value C1 is controlled by the control cycle to.
"1" is added every (for example, 10 milliseconds).

First, the interrupt routine shown in FIG. 8 will be described. When receiving the edge signals SE1 and SE2, the CPU 41 executes the interrupt routine with priority. First, in step 810, detection processing of the steering wheel operation direction is performed.
The steering operation direction is determined by the signals SS1, SS2, SE1,
Using SE2, two-phase signal SS shifted by 90 °
1, SS2. That is, FIG.
As shown in FIG. 5, when the phase of the signal SS1 is delayed by 90 ° from the phase of the signal SS2, “right steering” is performed. When the phase of the signal SS1 is advanced by 90 ° from the phase of the signal SS2, “left steering” is performed. judge. The result of the determination of the steering operation direction is set in a steering direction flag. The steering direction flag is set to “0” when the steering operation direction is leftward, and “1” when the steering operation direction is rightward.

At step 820, the steering counter 44 is counted according to the result of the determination of the steering direction (operation direction). That is, when the steering direction is “rightward”, the count value C is incremented, and when the steering direction is “leftward”.
If, the count value C is decremented. However,
When incrementing the count value C = “159”, the count value C is set to “0”, and when decrementing the count value C = “0”, the count value C is set to “159”. In this way, the steering counter 44 displays the knob 2a at a steering wheel relative angle with 0 degree when the knob 2a is in the neutral position.
The count value C corresponding to the steering wheel angle θ representing the position is counted.

In step 830, the control cycle counter 4
It is determined whether or not the count value (control cycle count value) C1 of 5 is equal to or greater than a set value Co at which the steering operation can be regarded as stopped. The count value C1 of the control cycle counter 45 is cleared each time the interrupt routine is executed, that is, every time the handle 2 is operated by 1/160 rotation (2.25 °), and every time the knob position correction control process is executed. This value is incremented at intervals of the period to (for example, 10 milliseconds). For this reason, the count value C1 of the control cycle counter 45 represents a value corresponding to the time required for the handle 2 to be operated by 1/160 of a rotation, and the time when the count value C1 is equal to or more than the set value Co is determined. The operation is considered to be stopped.

If the count value C1 is equal to or greater than the set value Co, in step 840, "judgment of stopping the steering operation"
And set the steering stop determination flag to “1”. If the count value C1 is less than the set value Co, the steering stop determination flag becomes "0" which is reset at the start of the interrupt routine. Then, in step 850, the control cycle counter 45 is cleared.

As described above, during execution of the knob position correction control processing, the current steering wheel angle θ can be determined by looking at the count value C of the steering counter 44, and the current steering wheel operating direction can be determined by looking at the steering direction flag. By looking at the steering stop determination flag, it can be determined whether or not the steering operation is stopped.

Next, the knob position correction control processing shown in the flowcharts of FIGS. 6 and 7 will be described. First, in step 10, the control cycle counter 45 is incremented. In step 20, the steering wheel angle θ and the tire turning angles R and R1 are read. The steering angle θ is the steering counter 4
The count value C of 4 is read. As the tire turning angle R1, the data of the tire turning angle before the predetermined time n · to stored in the RAM 43 is read. Note that the current tire turning angle R is stored in a predetermined area of the RAM 43 every time for use as data of the tire turning angle R1 after a predetermined time n · to.

In step 30, the map M1 shown in FIG.
Is used to calculate the target steering wheel angle θg from the tire turning angle R. The target steering wheel angle θg is obtained as a target steering count value Cg corresponding to the count value C of the steering counter 44.

Steps 40 to 90 are processes for calculating a target direction which is a steering wheel operation direction which permits execution of the knob deviation correction. That is, it is determined which of the left and right directions is the shortest path from the current knob position to the target knob position.

Step 40 is a process for calculating the deviation Δθ = | θ−θg | between the current steering wheel angle θ and the target steering wheel angle θg. In processing, a deviation ΔC between the current count value C of the steering counter 44 and the target steering count value Cg is represented by ΔC = | C.
-Cg | is calculated.

Step 50 is a process for determining whether the deviation Δθ is equal to or greater than 180 ° or less than 180 °. Deviation Δθ ≦ 1
If it is 80 ° (that is, deviation ΔC ≦ 80), it is determined in step 60 whether or not θ <θg (that is, C <Cg) is satisfied. In step 60, if θ <θg is satisfied, the target direction is determined to be “rightward” (S70), and if θ <θg is not satisfied, the target direction is determined to be “leftward” (S9).
0). In addition, deviation Δθ> 180 ° (that is, deviation ΔC> 8)
0), in step 80, θ <θg
(That is, C <Cg) is determined. In step 80, if θ <θg is satisfied, the target direction is determined to be “leftward” (S90), and if θ <θg is not satisfied, the target direction is determined to be “rightward” (S70). The target direction is set in a target direction flag. The target direction flag is reset to “0” when the target direction is “left”, and is set to “1” when the target direction is “right”.

In step 100, the tire turning angular velocity ΔR
= | R-R1 |. In step 110, the shift amount δ between the current knob position and the target knob position is calculated. That is, when the deviation Δθ ≦ 180 ° (ΔC ≦ 80), the deviation amount δ = Δθ (processing deviation amount δc = ΔC), and when the deviation Δθ> 180 ° (ΔC> 80), the deviation amount δ = 360 ° −Δθ (Processing deviation amount δc = 160−Δ
C). Thus, the shift amount δ between the current knob position and the target knob position in the shortest path is obtained. This shift amount δ is treated as a shift amount Δc in processing.

Step 120 is a process for determining whether or not the steering operation is stopped. If "1" is set to the steering stop determination flag, it is determined that the steering operation is stopped. When the steering operation is stopped, a valve closing command for outputting a degaussing signal to the excitation / degaussing drive circuit 40 is executed in step 180. Therefore, the electromagnetic valve 22 is kept closed while the steering operation is stopped.

In the next step 130, it is determined whether or not the deviation amount δ is equal to or smaller than the allowable value δo. If the deviation amount δ is equal to or smaller than the allowable value δo, the process shifts to step 180 to execute a valve closing command. On the other hand, when the deviation amount δ exceeds the allowable value δo, the routine proceeds to step 140.

In step 140, the tire turning angular velocity ΔR
Is smaller than the set value ΔRmin. That is, the orbit roll efficiency of the orbit roll 4 is 10
It is indirectly determined from the tire turning angle ΔR that the steering wheel 2 is operated at a low speed (less than 0.3 rps in this embodiment) exceeding 0% and exceeding a predetermined value. Δ
If R <ΔRmin is not established, the routine proceeds to step 160, and if ΔR <ΔRmin is established, the routine proceeds to step 150.

In step 150, the vehicle speed is set to "2 km /
h "or less is determined. That is, from the value obtained by counting the number of pulses per unit time of the vehicle speed signal v which is a pulse signal having a frequency proportional to the vehicle speed input from the vehicle speed sensor 35, it is determined whether the vehicle speed is equal to or less than "2 km / h". to decide. "2km
If the vehicle speed exceeds "/ h", the routine proceeds to step 160. If the vehicle can be considered to be in a stopped state at a vehicle speed of "2 km / h" or less, the process proceeds to step 180 to execute a valve closing command.

In step 160, it is determined whether the steering direction matches the target direction. This determination is made based on whether or not both flag values of the steering direction flag and the target direction flag match. If the steering direction matches the target direction, the process proceeds to step 170 to issue a valve open command. If the steering direction does not match the target direction, the process proceeds to step 180 to issue a valve close command.

When the knob 2a deviates from the normal position by more than the allowable value, the tire turning angle speed is low (that is, ΔR <ΔRmin) and the vehicle can be regarded as stopped (vehicle speed is 2 km / h or less). ), The solenoid valve 22 is opened when the handle 2 is operated in a direction in which the knob 2a approaches the shortest path from the current position to the regular target position, except when the two conditions at the same time are satisfied. Position correction will be performed.

That is, when the steering wheel 2 is operated at a rotation speed equal to or higher than the medium speed at which the tire turning angle ΔR can be equal to or higher than ΔRmin, the target direction in which the generated deviation can be reduced regardless of whether the vehicle is stopped or running. Whenever the steering wheel is operated, the knob position correction is executed. Even if the solenoid valve 22 is opened in a state where the vehicle speed can be regarded as a vehicle stop state where the vehicle speed is less than “2 km / h”, if the operation speed of the steering wheel 2 is a rotation speed of 0.3 rps or more, the tire is not stored in the steering cylinder 12. The hydraulic pressure enough to overcome the torsional return force is secured, and the slippage of the handle at this time surely reduces the displacement of the knob 2a.

Even when the steering wheel 2 is operated at a low speed at which the tire turning angle ΔR is less than ΔRmin, the vehicle speed 2k
When the vehicle is traveling at m / h or more, the knob position is corrected when the steering wheel is operated in the target direction that can reduce the generated displacement. For this reason, the steering wheel 2 when traveling straight ahead
Even if the knob position gradually shifts during operation while fine-tuning the knob, if the shift exceeds the allowable value, the knob position correction is executed, and the knob 2a is correctly positioned substantially at the neutral position.

When the steering wheel 2 is slowly operated at a rotation speed of less than 0.3 rps and ΔR <ΔRmin is satisfied in a state where the vehicle can be regarded as a vehicle stopped state at a vehicle speed of 2 km / h or less, the generated deviation is corrected. Even if the handle 2 is operated in a possible target direction, the solenoid valve 22 is not closed.

When the steering wheel 2 is operated at a low speed in a state where the vehicle can be regarded as stopped, the knob position correction control as shown in FIG. 9 is performed. As shown in FIG. 9A, when the steering wheel 2 is operated with the vehicle stopped, the tire is twisted at an angle α due to a large frictional resistance of the contact surface of the tire. When the handle is operated in the direction of the arrow from the state in which this twist has occurred, the handle is operated in the direction in which the current knob position approaches the target knob position. However, since the opening of the solenoid valve 22 is prohibited, the amount of deviation is reduced. Steering of the steering wheel 2 is performed while keeping it (FIG. 9B). When the steering wheel is turned back from this state, since the current knob position is in a direction away from the target knob position, the shift amount is stored as it is (FIG. 9).
(C), (d)).

[0086] Even when the vehicle is stopped, the steering wheel 2 is kept at 0.3 rp.
When the rotation speed exceeds s, the solenoid valve 22 is opened even when the tire is twisted as shown in FIG. 9A. In this case, even if the solenoid valve 22 is opened, the hydraulic steering cylinder 12 only overcomes the torsion of the tire.
Therefore, the knob 2a is corrected to the target knob position as shown in FIG.

As shown in FIG. 5, the knob position correction is performed in the target direction in which the knob 2a approaches the target position by the shortest path (along the a1 direction when the current knob position is the solid line position, and in the a2 direction when the current knob position is the chain line position). It is executed only when the handle 2 is operated. Then, when the handle 2 is operated in the direction in which the knob 2a approaches the target position along the longest path (the direction x1 when the current knob position is the solid line position, and the direction x2 when the knob position is the chain line position), the knob position correction is not executed. The target direction differs depending on the area where the current knob position is divided into two areas at a position 180 ° from the target knob position, and the knob is only operated when the handle 2 is operated in a direction that can reduce the deviation amount δ. The position correction is executed, and the deviation is always reduced when the electromagnetic valve 22 is opened.

When the knob 2a is displaced by more than 180 °, for example, a correction for displacing by one rotation is made, and the deviation is corrected with an idling amount smaller than the actually displaced amount. Also,
When the knob 2a is displaced by one or more rotations, the idling amount of only the apparent deviation amount δ considering only the relative angle of the steering wheel is sufficient, so that the conventional device that performs correction in accordance with the absolute steering wheel angle following the deviated path can be used. In comparison, the idling amount of the steering wheel 2 required for the correction is small.

Further, since the orbit roll 4 of the low slip type is employed, a large amount of discharged oil is ensured even when the steering wheel 2 is operated at a low speed with the vehicle stopped, so that the steering wheels 19
, The good handle operation feeling can be ensured even if the knob position correction is executed while the vehicle is stopped. Further, since the orbit roll 4 is a low-slip type, even if the knob position correction is being performed when the steered wheels 19 reach the end, a greater resistance is transmitted from the steering wheel 2 as compared with the standard type. The operator immediately recognizes that the steered wheels 19 have reached the end.

As described in detail above, according to the present embodiment,
The following effects can be obtained. (1) When the steering wheel 2 is rotated at a low speed in a state where the vehicle speed can be regarded as a vehicle stopped state of 2 km / h or less, the opening of the solenoid valve 22 is prohibited. It is possible to surely prevent the deviation of the knob 2a that may be caused by the return of the twist of the tire when the tire 22 is opened. For this reason, even in the low-speed range of the steering wheel operating speed in which the correction of the steering wheel displacement is prohibited in the conventional device, the knob position correction can be performed except when the vehicle can be regarded as the vehicle stopped state, and the opportunity for the knob position correction is provided as compared with the conventional device. Can be increased.

(2) The low-slip type orbit roll 4 is employed. When the vehicle speed exceeds 2 km / h, the knob position is corrected even if the steering wheel operation speed is low. If the knob 2a is displaced even when finely adjusted to the left and right, the correction is executed, so that the knob 2a can be correctly placed almost at the neutral position even when traveling straight.

(3) Since the orbit roll 4 of the low slip type is employed, even if the steering wheel 2 is operated at a low speed while the vehicle is stopped, the steered wheels 19 can be almost surely turned by an angle commensurate with that.

(4) By adopting the low slip type orbit roll 4, the fact that the steered wheels 19 have reached the end can be confirmed by the heavy resistance transmitted from the steering wheel 2 even if the knob position correction happens to occur at that time. Can be grasped reliably.

(5) The discharge amount is such that the orbit roll efficiency of the orbit roll 4 is secured in the steering cylinder 12 to a hydraulic pressure sufficient to overcome the tire torsion return force of the steered wheels 19 when the solenoid valve 22 is opened. Is determined from the tire turning angle speed ΔR,
The detection value of the tire angle sensor 28 can be used for this determination.

(6) Since the knob shift is corrected in consideration of only the handle relative angle, even if the knob 2a actually shifts by one or more rotations, for example, a correction amount of an apparent shift smaller by one rotation is sufficient. Unnecessary idling can be reduced.

(7) Since the knob position correction is executed only when the steering wheel is operated in the target direction approaching the shortest path from the current knob position to the target knob position, the deviation can always be reduced when the correction is executed. In addition, when the actual deviation amount is less than one rotation and exceeds 180 °, the knob 2a is deviated by one rotation so that the correction amount is smaller than the actual deviation amount. The idling amount of the handle 2 during the position correction can be further reduced.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the steering wheel 19 caused by the return of the torsion of the tire is used.
This is an example in which the knob position correction is stopped when the behavior is detected to prevent the deviation from expanding. Since the configuration of the apparatus is exactly the same as that of the first embodiment, and only the program data of the knob position control processing is different, the same parts are denoted by the same reference numerals and description thereof will be omitted, and only different parts will be described in detail.

The ROM 42 stores the program data of the knob position control processing shown in FIGS. 10 and 11, and the program data of the same interrupt routine as that shown in FIG. In the knob position control process in this embodiment, a possible behavior of the tire when the solenoid valve 22 is opened in a state where the tire is twisted is detected, and when such a behavior of the tire is detected, the solenoid valve 22 is activated. By closing the valve, an increase in the deviation of the knob position is prevented. Therefore, the detection of the tire turning angle speed performed in the first embodiment is not performed.

In the flowchart shown in FIG. 10, steps 210 to 300 correspond to steps 10 to 90 and 110 in FIG. 6, respectively. However, in step 220, the reading of the data of the tire turning angle R1 read in step 20 of the first embodiment corresponding to this processing is not performed because it is unnecessary.
The process (S100) of calculating the steering wheel turning angle ΔR performed in the first embodiment is omitted because it is unnecessary.

In the flowchart shown in FIG. 11, steps 310, 320, 370
Steps 390 to 390 correspond to steps 120, 130, and 160 to 180 in FIG. 7, respectively, and the processing contents thereof are exactly the same.

Step 330 is a process for determining whether or not valve opening is prohibited. That is, when the behavior of the steering wheel 19 when the torsion of the tire returns is detected, the solenoid valve 22 is opened for a predetermined time (for example, several tens to several tens).
(00 milliseconds). The prohibition flag is set to “1” when the behavior of the steering wheel 19 when the torsion of the tire returns is detected, and the prohibition flag is set to “1”.
During this period, it is determined that valve open is prohibited.

Step 340 is a process for determining whether or not a valve open command is currently being issued. If "1" is set in the valve flag described in the first embodiment, it is determined that a valve open command is being issued.

Steps 350 and 360 are processes for detecting the behavior of the steered wheels 19 when the torsion of the tire returns. These processes are performed only when the electromagnetic valve 22 is opened. The behavior of the steering wheel 19 when the torsion of the tire returns is determined by a behavior in which the steering wheel 19 is turned in a direction opposite to the steering wheel operation direction (referred to as a first behavior), and an amount of the turning angle of the tire divided by the steering wheel operation amount. It appears as either a behavior that increases (referred to as a second behavior). Taking advantage of this, in step 350, since it is detected that the target steering wheel angle θg is changing in the direction opposite to the steering wheel operating direction, the first behavior of the steered wheels 19 is indirectly detected. . In step 360, since the deviation amount δ is detected to be wide, the second behavior of the steered wheels 19 is indirectly detected.

When the knob position correction processing is executed by the CPU 41, the following knob position control is performed. Each time the interrupt routine is executed, a flag value corresponding to the steering operation direction is set in the steering direction flag, and "1" is set in the steering stop determination flag while the steering operation is stopped. Each time the knob position control process is performed (every 10 milliseconds), the target direction flag becomes a flag value corresponding to the target direction. When the solenoid valve 22 is normally closed other than during the valve opening prohibition, the prohibition flag is in a reset state.

For example, when the knob 2a is displaced and the deviation δ exceeds the allowable value δo, and the handle 2 is operated in the direction corresponding to the target direction in this state, the solenoid valve 22 is opened to start the knob position correction. Is done. At this time, the valve flag is set to “1” by opening the solenoid valve 22. Therefore, in the next knob position control process, since the valve flag is “1”, it is determined in step 340 that the valve open command is being issued, and the process proceeds to step 350.

At step 350, the target steering wheel angle θg
Is changed in the direction opposite to the steering direction (handle operation direction). In the present embodiment, for example, data of the target steering wheel angle θg (set as θg 1) before the predetermined time n · to is read from the RAM 43, and the difference Δθg (= θg−θ) of the target steering wheel angle before and after the predetermined time n · to elapses.
g In principle, from the sign of 1), the target steering wheel angle θg
It is determined whether or not the change direction is opposite to the steering direction. That is, when Δθg> 0, the tire cuts to the right, Δθg
When <0, the tire is cut to the left. Where Δθ
The absolute value of g (= | θg−θg1 |) is equal to the predetermined time n · t
If a value corresponding to a change that cannot physically be operated by the steering wheel is taken during o, the count value C becomes “0” and “15”.
9 ”as if it had passed through the boundary with
The direction of the sign opposite to that described above from the sign of θg is defined as the tire cutting direction.

For example, from the state shown in FIG.
Is operated in the direction of the arrow to open the solenoid valve 22, the first behavior in which the steered wheels 19 are turned in the direction opposite to the steering wheel operating direction due to the return of the torsion of the tire will be exhibited. At this time, if it is determined in step 350 that the target steering wheel angle θg has changed in the direction opposite to the steering direction,
The prohibition flag is set to "1", and the routine proceeds to step 390, where a valve close command is executed. Thereafter, the prohibition flag is kept at "1" for a predetermined time (for example, several tens to several hundreds of milliseconds). Commanded. Then, when the prohibition flag is reset to “0” after a lapse of a predetermined time, the process proceeds from step 340 to step 350, where the process of detecting the first behavior of the steered wheels 19 is performed again. Until the behavior due to the return of the torsion is no longer detected, the presence or absence of the first behavior of the steered wheels 19 is checked every predetermined time (for example, 100 milliseconds). Then, until the twist of the tire is lost and the first behavior of the steered wheels 19 is no longer detected in step 350, the solenoid valve 22 is kept in the valve-open prohibition state, and the valve is opened to confirm the presence or absence of the first behavior. With the exception of this, the valve is kept almost closed.

After the solenoid valve 22 is opened, step 35
If the first behavior is not detected at 0, the next step 360
Is performed. In step 360, it is determined whether or not the shift amount δ is wide. That is, first, the data of the deviation amount δ (set as δ1) before the predetermined time n · to is RA
When the sign of the difference .DELTA..delta. (= .Delta .-. Delta.1) before and after the elapse of the predetermined time n.to is read from M43 and the sign is positive,
It is determined that the deviation amount δ is widening.

For example, when the handle 2 is operated in the direction of the arrow (rightward) in FIG. 17 when the current position and the target position of the knob 2a are in the same state as in FIG. 17C, the solenoid valve 22 is opened. At this time, the second behavior in which the steered wheels 19 are cut much more than the steering wheel operation amount due to the return of the twisted tire, and the target knob position moves in the steering direction faster than the current knob position and the deviation amount δ spreads. Will show. If this second behavior is detected in step 360 by the determination that the deviation amount δ is widening, the prohibition flag is set to “1”, and the routine proceeds to step 390, where a valve close command is issued. Thereafter, for a predetermined time (for example, several tens to several hundreds)
(Milliseconds), it is determined in step 330 that the valve is being prohibited, so the valve close command is continuously issued. Then, when the prohibition flag is reset again after the lapse of the predetermined time, the process of step 360 is performed again. Hereinafter, the presence or absence of the second behavior of the steered wheels 19 is checked at predetermined time intervals until the second behavior of the steered wheels 19 due to the return of the torsion of the tire is no longer detected in Step 360. And the twist of the tire is gone,
Until the second behavior of the steered wheels 19 is no longer detected in step 360, the opening of the solenoid valve 22 is effectively prohibited. Therefore, the deviation amount δ is substantially kept, and is hardly enlarged.

Further, during traveling turning, an external force in the notch direction acts on the steered wheels 19 due to a difference in moment acting between the left and right steered wheels 19. For example, in a state where a cutting force in a direction indicated by a white arrow shown in FIG. 12A is applied to the steering wheel 19, the handle 2 is moved in the target direction in which the current knob position approaches the target knob position as shown in FIG. It is assumed that the solenoid valve 22 is opened by operating slowly. At this time, if the hydraulic pressure enough to overcome the notch force acting on the steered wheels 19 is not secured in the steering cylinder 12, the first behavior in which the steered wheels 19 move in the direction opposite to the steering direction immediately after the solenoid valve 22 is opened is detected. And the solenoid valve 22 is closed immediately. For this reason, as shown in FIG. 12C, even if the handle 2 is operated in the target direction, the deviation amount δ hardly spreads and is held.

Further, for example, in the state where the cutting force indicated by the white arrow shown in FIG.
When the solenoid valve 22 is opened due to the slow operation in the target direction indicated by the solid line arrow in (b), unless the hydraulic pressure enough to overcome the cutting force is secured in the steering cylinder 12, the solenoid valve 22 is opened. Immediately after that, the second behavior in which the steered wheels 19 move in the direction opposite to the steering direction is detected, and the solenoid valve 22 is closed immediately. For this reason, as shown in FIG. 12C, even if the handle 2 is operated in the target direction, the deviation amount δ hardly spreads and is held.

As described above, even if the electromagnetic valve 22 is opened due to the low-speed operation of the steering wheel 2 during the traveling turn, the electromagnetic valve 22 is closed immediately when the turning phenomenon of the steered wheels 19 starts to occur. It does not cause deterioration of the feeling of the steering wheel operation during the turning.

Further, even during such a traveling turn,
By operating the handle 2 at a certain operation speed, the electromagnetic valve 22 is operated.
If the hydraulic pressure enough to overcome the cutting force of the steered wheels 19 is secured in the steering cylinder 12 even when the valve is opened,
Since the first behavior and the second behavior of the steered wheel 19 are not detected,
The solenoid valve 22 is kept open. Therefore, at this time, the deviation amount δ decreases with the operation of the steering wheel.

As described above in detail, according to the second embodiment, the behavior of the steering wheel 19 when the torsion of the tire returns when the solenoid valve 22 is opened is detected. The solenoid valve 22 is immediately closed at the first time, so that it is possible to prevent a problem that the execution of the knob position correction in the vehicle stopped state in which the tires of the steered wheels 19 are twisted and the amount of positional shift of the knob 2a is increased. . Therefore, even when the steering wheel is operated at a low speed, the knob position correction can be performed to increase the opportunity.

Further, not only is it possible to prevent the deviation amount from being increased by executing the knob position correction when the vehicle is stopped, but also to prevent the
9 can be substantially prevented from increasing due to the cutting force acting on the knob 9 when the knob position is corrected. Further, when either the first behavior or the second behavior appearing at the time of the cut-off phenomenon is detected, the solenoid valve 22 is closed, so that the cut-off phenomenon is substantially prevented, and a sense of discomfort is generated between the steering operation and the turning change of the vehicle body. It is also possible to prevent the feeling of the steering wheel operation from deteriorating during the turning operation. In addition, since the detection of the first behavior and the second behavior is detected using the data of the steering wheel angle and the target steering wheel angle for calculating the deviation amount, the data used for the deviation correction of the steering wheel is used to detect the behavior of the steering wheel 19. Available to In addition, other effects described in the first embodiment can be similarly obtained.

The present invention is not limited to the above embodiment, but can be embodied as follows without departing from the spirit of the invention. (N) In the first embodiment, the set value Δrmin set for comparison with the tire turning angle speed ΔR for judging that the steering operation is low is selectively used when the valve is opened and when the valve is closed. You may. For example, when the valve is closed, the set value ΔRmin = r1 is adopted, and when the valve is opened, the set value ΔRmin = r2 is adopted (however, r1 and r2 are appropriate values satisfying r1> r2). Despite the same handle operation speed, the tire turning angle speed Δ when the valve is closed and when the valve is open
The intermittent time during which the knob position correction is intermittently stopped by changing R can be shortened or eliminated.

(R) In the first embodiment, the steering wheel rotation speed is determined from the change per unit time of the count value C of the steering counter 44, or the steering wheel rotation speed is detected using the counter C1 of the control cycle counter 45, The steering wheel rotation speed is low (that is, the orbit roll 4
Of the steering wheel 12 when the solenoid valve 22 opens so that the hydraulic pressure of the steering cylinder 12 cannot overcome the external force acting on the steered wheels 19 (tire twist return force or cutting force). The configuration may be such that the rotation angle is directly detected from the detection value of the rotary encoder 27. In the configuration of the second embodiment in which the steering wheel rotation speed is indirectly detected based on the tire turning angle speed, the solenoid valve 22 is intermittently stopped by erroneously detecting that the steering wheel is idling as a low speed operation of the steering wheel. Although there is a danger, according to this configuration, it is possible to correctly detect that the steering wheel operation is slow even during idling of the steering wheel.

(M) In the second embodiment, the opening of the solenoid valve may be prohibited until the handle is turned next time. According to this configuration, the steered wheels 19 are provided every predetermined time.
It is not necessary to check for the presence or absence of the behavior of the solenoid valve 22. The deviation amount δ is little by little with each opening of the solenoid valve 22 for examining the behavior of the steered wheels.
Can be prevented from expanding.

(P) In the second embodiment, the solenoid valve 22 may be closed only when the second behavior in which the target knob position departs from the current knob position is detected. According to this configuration, it is inevitable that the feeling of the steering wheel operation is deteriorated when the steered wheels 19 perform the first behavior, but at least enlargement of the deviation can be prevented.

(Q) The actuator used in the power steering device is not limited to a hydraulic cylinder. (T) The present invention may be applied for the purpose of correcting the position of a handle without a knob.

(S) Industrial vehicles other than forklifts equipped with a power steering device, and also automobiles (passenger cars)
The present invention can be widely applied to such vehicles. The invention grasped from the embodiment and not described in the claims will be described below together with its effects.

(A) In the invention described in claim 1 or 2, the steering angle detecting means for detecting the steering angle of the steering wheel by the steering wheel relative angle and the steering angle detecting means for detecting the steering angle of the steering wheel. When the deviation between the target steering wheel angle and the steering wheel angle calculated from the steering angle relative to the steering wheel angle exceeds a permissible value, the control means operates the steering wheel in the operating direction to bring the steering wheel angle closer to the target steering wheel angle. Sometimes, the correction means is driven. According to this configuration,
Unnecessary idling of the steering wheel at the time of steering wheel deviation correction can be reduced as compared with the case where the steering wheel deviation correction is performed based on the steering wheel absolute angle. The rotary encoder 27, the CPU 41 and the steering counter 44 constitute a steering wheel angle detecting means, and the tire angle sensor 28 constitutes a steering angle detecting means.

(B) Claim 1, Claim 2 or (A)
In the invention described in (1), the stop state detecting means detects the stop state from a vehicle speed. According to this configuration, the stop state of the vehicle can be detected from the vehicle speed.

(C) In the invention according to any one of claims 1 to 8 and any one of (a) and (b),
The correction unit is a valve unit that is provided on an oil passage for recirculating a part of the hydraulic oil discharged from the hydraulic oil supply device and that is driven to open when the control unit executes the correction. According to this configuration, the idling state of the steering wheel can be easily created by simple control of opening / closing control of the valve means by the control means. Note that the electromagnetic valve 22 constitutes valve means.

(D) Claims 1 to 8 and (a)
In the invention described in any one of (c) to (c), the hydraulic drive unit is a hydraulic cylinder. (E) In the invention according to any one of claims 1 to 8 and (A) to (D), the handle is provided with a knob, and the control means determines that the knob is normal. The driving of the correction means is controlled so as to be arranged at the position of. According to this configuration, the position of the knob can be corrected to a regular position corresponding to the turning angle of the steered wheel, and the position of the knob can be used as a guide for determining the turning angle of the steered wheel.

(F) In the invention described in claim 8, the vehicle is an industrial vehicle. According to this configuration, the same effect as that of the invention described in claim 8 can be obtained in an industrial vehicle.

[0127]

As described in detail above, according to the first and eighth aspects of the present invention, the correcting means is not driven when the steering operation is slow and the vehicle can be regarded as stopped. Therefore, it is possible to prevent a problem in which the correction of the steering wheel is performed due to the twisting of the tires of the steered wheels when the vehicle is stopped and the deviation of the steering wheel is increased, thereby increasing opportunities for correcting the deviation of the steering wheel.

According to the second and eighth aspects of the present invention, since the steering wheel rotation speed is indirectly detected from the tire turning angle speed, the detection data of the steering angle can be used for detecting the low-speed operation of the steering wheel.

According to the third and eighth aspects of the present invention, the driving of the correcting means is stopped when the behavior of the steered wheels which may increase the deviation when the correcting means is driven is stopped. Not only the torsion of the tires on the steered wheels,
It is possible to prevent an increase in the deviation at the time of correcting the deviation of the steering wheel due to the turning phenomenon of the steered wheels during the traveling turning, and thus it is possible to increase opportunities for correcting the deviation of the steering wheel.

According to the fourth and eighth aspects of the present invention, the shift of the steering wheel is corrected based on the relative angle of the steering wheel, so that the shift of the steering wheel is corrected based on the absolute angle of the steering wheel. Unnecessary idling at the time of deviation correction can be reduced.

According to the fifth and eighth aspects of the present invention, the first behavior in which the steered wheels move backward in the steering wheel operating direction,
Since at least the second behavior is detected among the second behaviors in which the steered wheels turn faster than the speed corresponding to the steering wheel operating speed, it is possible to at least prevent the deviation from increasing due to the deviation correction of the steering wheel.

According to the sixth and eighth aspects of the present invention, the first behavior and the second behavior of the steered wheels are both detected, and if any one of them is detected, the driving of the correction means is stopped. It is possible to prevent the feeling of the steering wheel operation from being deteriorated due to the notched phenomenon of the steered wheels.

According to the seventh and eighth aspects of the present invention, the first behavior is detected when the target steering wheel angle approaches the steering wheel angle, and the second behavior is detected when the deviation increases. In addition, data used for steering wheel deviation correction can be used for detecting the behavior of the steered wheels.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a power steering device according to a first embodiment.

FIG. 2 is an electric configuration block diagram of a steering wheel angle correction device.

FIG. 3 is a time chart of an output signal from an encoder.

FIG. 4 is a graph showing a map.

FIG. 5 is an explanatory diagram of knob position correction control.

FIG. 6 is a flowchart of a knob position correction control process.

FIG. 7 is also a flowchart.

FIG. 8 is a flowchart of an interrupt routine.

FIG. 9 is an explanatory diagram for explaining knob position correction when the vehicle is stopped.

FIG. 10 is a flowchart of a knob position correction control process according to the second embodiment.

FIG. 11 is also a flowchart.

FIG. 12 is an explanatory diagram for explaining knob position correction during traveling turning.

FIG. 13 is an explanatory view of the same.

FIG. 14 is a schematic view of a steering device according to a conventional technique.

FIG. 15 is a graph showing efficiency characteristics of each type of orbit roll.

FIG. 16 is an explanatory diagram illustrating correction of a deviation of a steering wheel during traveling turning.

FIG. 17 is an explanatory diagram illustrating correction of steering wheel displacement when the vehicle is stopped.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Power steering device, 2 ... Handle, 2a ... Knob, 4 ... Orbit roll as hydraulic oil supply device, 1
2 ... Steering cylinder as actuator, 1
9: Steered wheels, 22: Solenoid valve as correction means, 27: Rotary encoder constituting steering wheel angle detection means, 28
... A tire angle sensor as steering angle detecting means and low speed steering detecting means, turning angle speed detecting means and wheel behavior detecting means, 35... A vehicle speed sensor as stationary state detecting means,
41: CPU constituting control means, low-speed steering detecting means, turning angle speed detecting means, wheel behavior detecting means, 42: ROM,
44 ... steering counter constituting steering wheel angle detecting means, 4
0: Excitation / demagnetization drive circuit constituting control means, θ: steering wheel angle, R: tire turning angle as turning angle, θg: target steering wheel angle, δ: shift amount as shift, F: forklift as vehicle.

Claims (8)

[Claims] 1. A low-slip type hydraulic oil supply device that discharges an oil amount according to a rotation amount of a handle, and increases a discharge ratio in a low speed region of the handle rotation speed, and discharges the oil from the hydraulic oil supply device. A power steering device comprising: an actuator driven by the operating oil to steer the steered wheels; and a correction means for returning a part of the operating oil discharged from the operating oil supply device to create an idling state of the steering wheel. A low-speed steering detecting means for detecting that the steering wheel rotation speed is lower than a predetermined value, and a stop for detecting a state in which the vehicle can be regarded as a stopped state in which the road surface frictional resistance during steering of the steered wheels becomes larger than a predetermined value. Even if the low-speed steering detecting means detects that the handlebar rotation speed is low, the vehicle is stopped by the stationary state detecting means. If it is not detected that the state can be regarded as a state that can be considered as a state, when a deviation of the correspondence relationship between the steering wheel angle of the steering wheel and the steering angle of the steered wheel is detected, the correction is performed when the steering wheel is operated in a direction to correct the deviation. A steering angle correction device in a power steering device, comprising: a control unit that drives the unit. 2. The steering control device according to claim 1, wherein the low-speed steering detecting unit includes a turning angle speed detecting unit that detects a turning angle speed of the steering wheel, and a steering wheel rotation speed is low based on the turning angle speed detected by the turning angle speed detecting unit. The steering angle correction device in the power steering device according to claim 1, wherein the steering angle correction device detects indirectly. 3. A low-slip type hydraulic oil supply device that discharges an oil amount according to a rotation amount of a handle and increases a discharge ratio in a low speed range of the handle rotation speed, and discharges the oil from the hydraulic oil supply device. A power steering device having an actuator driven by the operating oil to steer the steered wheels, wherein a correction means for returning a part of the operating oil discharged from the operating oil supply device to create an idling state of the steering wheel. Wheel behavior detection means for detecting the behavior of the steering wheel which is considered to be likely to widen the deviation of the correspondence between the steering wheel angle of the steering wheel and the steering angle of the steering wheel when the correction means is driven; A deviation of the correspondence relationship with the steering angle of the steered wheels is detected, and when the steering wheel is operated in a direction to correct the deviation, the correcting means is driven, and A steering angle correction device in a power steering device, comprising: control means for stopping driving of the correction means when the wheel behavior detection means detects the behavior of a steered wheel when the correction means is driven. 4. The steering device according to claim 1, wherein the control unit detects a handle angle of the handle based on a handle relative angle.
Steering angle detecting means for detecting the steering angle of the steered wheels, and the steering wheel is moved in a direction in which the current steering wheel angle detected by the steering wheel angle detecting means approaches a target steering wheel angle determined by the steering wheel relative angle from the steering angle in the shortest path. 4. The steering wheel angle correction device in a power steering device according to claim 3, wherein the correction unit is driven only when operated. 5. The wheel behavior detecting means includes: a first behavior in which the steered wheels are turned in a direction opposite to a steering wheel operation direction; and a second behavior in which the steered wheels are steered more than a steering amount corresponding to a steering wheel operation amount. The steering angle correction device for a power steering device according to claim 4, wherein at least the second behavior is detected. 6. The steering wheel angle correction device for a power steering device according to claim 5, wherein the wheel behavior detecting means detects both the first behavior and the second behavior. 7. The wheel behavior detecting means performs the first behavior when the target steering wheel angle approaches the steering wheel angle, and detects the second behavior when the deviation increases. Item 7. A steering wheel angle correcting device in the power steering device according to Item 6. 8. A vehicle comprising the steering wheel angle correction device according to claim 1. Description: