JPH11171497A - Dither controller of industrial vehicular solenoid valve and industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the spool amplitude of a solenoid valve at the time of dither control to a constant desired at all times without regard to any disturbance factors such as variations or the like in supply voltage and solenoid resistance, in a structure which exercises its current value control over the solenoid valve installed in this industrial vehicle with software. SOLUTION: A central processing unit determines a duty output central value Dcent to define the duty value (%) of a pulse width modulation signal being inputted into a transistor interposed between a battery and the solenoid valve, through feedback control. A duty reference value Dbase to be determined at the time of a reference state (each reference value of battery voltage and solenoid resistance) from the desired current value Iaim is found out (S220). A dither amplitude value Ddizz is computed after multiplying a dither amplitude reference value D [cnt] (cnt = 0, 1,..., 7) set up as a premise of the reference state to be determined from a count value cnt by a ratio (Dcent/Dbase) (S270). An duty output value Dout=Dcent+Ddizz on a sine-wave making the Dcent value a amplitude center is computed and commanded (S320 and S340).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industrial vehicle for performing dither control in which a spool is minutely vibrated in order to enhance responsiveness of an electromagnetic valve provided in an oil passage of a hydraulic cylinder for driving cargo handling equipment provided in the industrial vehicle. The present invention relates to a dither control device for an electromagnetic valve and an industrial vehicle.

[0002]

2. Description of the Related Art Conventionally, by controlling a solenoid valve provided on an oil passage of a lift cylinder or a tilt cylinder provided in a forklift to a controller, the fork is kept in a predetermined state independently of an operation of a cargo handling lever by an operator. There is disclosed a device for performing stop control for stopping at a speed and for controlling the speed of a mast (for example, Japanese Patent Application Laid-Open No. 7-61792).

The control of the current value of the solenoid valve by the controller is usually performed as follows. The controller instructs the solenoid drive circuit with a current command value (target current value) corresponding to the opening of the solenoid valve determined from the detection values from various sensors provided in the vehicle. When a switching element in a solenoid drive circuit provided between the battery and the solenoid valve is turned on and off based on a current command value, a current flowing through a solenoid of the solenoid valve is controlled.

[0004] By the way, the battery voltage greatly fluctuates between when the battery is fully charged and when the battery becomes almost empty. In addition, the solenoid resistance of the solenoid valve varies with an increase in the solenoid temperature due to an increase in oil temperature or heat generation due to the application of current.
Even if these fluctuations become disturbance factors and the switching element is turned on and off according to the current command value, a situation may occur in which the current flowing through the solenoid deviates from the target value. The deviation of the current value from the target value causes variation in the opening of the solenoid valve,
This may cause a malfunction in the cargo handling equipment. For this reason, conventionally, the current value control of the solenoid valve has been performed by feedback control.

Conventionally, feedback control has been performed by hardware. When using hardware, many circuits such as a triangular wave generation circuit, a duty generation circuit, a current detection circuit, and a feedback circuit are required. That is,
A triangular wave generation circuit for generating a triangular wave signal. A command value (voltage signal V) corresponding to the target current value input from the CPU
1) A duty generating circuit for generating a PWM signal having a duty value (%) corresponding to a command value by inputting a triangular wave signal. A current detection circuit for detecting the current flowing through the solenoid of the solenoid valve. Further, a signal (voltage; a (V1-V) that is proportional to the difference between the command value (voltage signal V1) output from the CPU and the current detection value (voltage signal V2) from the current detection circuit.
2)) is a feedback circuit for correcting the input voltage input to the duty generation circuit according to the detected current value.

In other words, when the CPU issues a command value corresponding to a target current value that needs to flow through the solenoid, the circuits that constitute the hardware are switched so that the current according to the command value flows through the solenoid. The duty value (%) of the PWM signal input to the element is corrected. Thus, even if there is a disturbance factor such as a change in the battery voltage or the solenoid resistance, a current according to the target current value flows through the solenoid.

However, in a configuration in which feedback control is performed by hardware, there are problems that the above-described many circuits are required, resulting in a complicated circuit configuration and an increase in the number of electronic components. This has also led to an increase in equipment costs.

[0008]

Therefore, the applicant of the present application has proposed that the feedback control be performed by software using a CPU in order to reduce the number of hardware circuits and simplify the hardware. That is, a current detection value from a current detection circuit that detects a solenoid current is input to the CPU. Then, the duty output value D which the CPU instructs to determine the duty value (%) of the PWM signal.
This is a method of correcting out based on program data so that the detected current value approaches the target current value.

As a control for improving the responsiveness of the solenoid valve, dither control for slightly vibrating the spool is generally performed. In hardware feedback control, if the CPU commands the current command value to draw a waveform that can cause the spool to vibrate minutely, the hardware corrects the current command value so that the current flows as the current command value The small amplitude of the spool is always kept constant regardless of disturbance factors. As the control, by correcting the target current value by the dither amplitude, a plurality of current command values which are to be on the waveform of the dither control are determined by an interrupt process, and are sequentially commanded.

In software feedback control, this method is also followed, and a current command value which is adjusted to the dither amplitude is added to the current command value to determine a plurality of current command values riding on the waveform of dither control by interrupt processing. Dither control can be performed by sequentially instructing this.

However, if the dither amplitude value, which is the amount of correction for the dither amplitude, is set to a constant value as in the case of feedback control by hardware, the solenoid is affected by disturbance factors such as the above-mentioned fluctuations in battery voltage and solenoid resistance. The amplitude of the current flowing through the device varies.

That is, as shown in FIG. 21, as the battery voltage increases and the solenoid resistance decreases, the amplitude of the solenoid current becomes excessively larger than the amplitude of the desired current waveform I, as indicated by the line A, and the spool is displaced. It becomes excessively large. Further, as the battery voltage becomes smaller and the solenoid resistance becomes larger, the amplitude of the solenoid current becomes too smaller than the amplitude of the desired current waveform I as shown by the line B, and the amplitude of the spool becomes too small.

If the amplitude of the spool is too large, the solenoid valve may open slightly when the valve should be closed, and the fluctuation of the opening of the solenoid valve due to dither control may affect the operation of the cargo handling equipment. This may cause problems such as slight vibration during the operation of the cargo handling equipment. Further, if the minute amplitude of the spool becomes too small, the effect of reducing the frictional resistance at the time of starting the spool becomes insufficient, and the responsiveness of the solenoid valve is reduced.

The present invention has been made in view of the above-mentioned problems, and a first object of the present invention is to provide a configuration in which the current value control of a solenoid valve provided in an industrial vehicle is performed by software. The amplitude of the oscillating solenoid valve spool can always be maintained at a desired constant regardless of disturbance factors such as fluctuations in power supply voltage and solenoid resistance, and can prevent problems caused by variations in spool amplitude. A dither control device and an industrial vehicle are provided. A second object is to make data used for feedback control available for dither control. A third object is to properly obtain the amplitude of the spool at least when the current is in a steady state by using the detected current value used in the feedback control. 4th
The object of the present invention is to obtain the spool amplitude properly in both the transient region and the steady region of the current by using the measured value of the disturbance factor used in the feedback control. A fifth object is to appropriately obtain the amplitude of the spool in both the transient region and the steady region of the current even in the feedforward control using the measured value of the disturbance factor. A sixth object is to determine a dither amplitude value by a simple calculation. A seventh object is to be able to determine a dither amplitude value by a simple calculation using a target current value and a current command value. An eighth object is to prevent the amplitude of the spool from becoming an abnormal value in the transient region of the current when determining the dither amplitude value using the target current value and the current command value. A ninth object is to determine a dither amplitude value by a simple calculation using a current command value and a current detection value. A tenth object is to obtain a current detection value almost in real time so as not to impair control responsiveness.

[0015]

According to the first aspect of the present invention, there is provided an electromagnetic valve provided on an oil passage of a hydraulic cylinder for driving cargo handling equipment, and a solenoid of the electromagnetic valve. Storage means for storing a target current value to be supplied to the solenoid, measurement means for measuring a measurement value necessary to obtain data used for control for setting a current flowing through the solenoid to a target current value, and Control for executing a correction process based on program data for correcting a current command value for controlling a flowing current using the data obtained from a measurement value of the measurement means so that the current command value can approach a target current value. Means, and dither control for micro-vibrating the spool of the solenoid valve, the dither amplitude value corresponding to the amplitude added to the current command value is measured so that a desired current amplitude is obtained. Together we determined using the data obtained using, and a dither control means for commanding the dither command value obtained by adding the dither amplitude value to the current command value.

According to a second aspect of the present invention, in the first aspect of the invention, the dither control means performs a predetermined cycle around the current command value every time the control means executes the correction process once. The gist is that a plurality of the dither command values are determined by an interrupt process and commanded in one cycle of the waveform so as to take a value on the waveform that is amplitude in the above.

According to a third aspect of the present invention, in order to achieve a second object, a current detecting means for detecting a current flowing through a solenoid of the solenoid valve is provided, and the control means is provided. Is a feedback control that corrects the current command value so that a difference between a current detection value determined from a detection signal of the current detection means and the target current value falls within an allowable range. The gist is that the control means determines the dither amplitude value using data obtained using the measurement value used in the feedback control.

According to a fourth aspect of the present invention, in order to achieve a third object, in the third aspect of the present invention, the measuring means is the current detecting means, and the dither controlling means is such that the controlling means The gist is that the dither amplitude value is determined using data obtained using the current detection value used in the feedback control.

According to a fifth aspect of the present invention, in order to achieve a fourth object, in the third aspect of the present invention, the measuring means measures a disturbance factor which affects a current flowing through the solenoid. The gist is that the dither control means determines the dither amplitude value using data obtained by using the measured value of the disturbance factor used in the feedback control by the control means.

According to a sixth aspect of the present invention, in order to achieve the fifth object, in the first or second aspect of the invention, the measuring means measures a disturbance factor which affects a current flowing through the solenoid. Is a disturbance factor measuring means,
The correction process performed by the control unit is feedforward control for instructing a current command value determined from a target current value in consideration of a disturbance factor using a measured value of the disturbance factor measurement unit, and the dither control unit includes: The gist of the invention is that the dither amplitude value is determined using data obtained by using the measured value of the disturbance factor measuring means.

According to a seventh aspect of the present invention, in order to achieve the sixth object, in the first aspect of the present invention, the dither control means is configured to control a current flowing through the solenoid. The dither amplitude reference value is set in advance so that the desired current amplitude is obtained under the assumption that the influencing disturbance factor is in the reference state, and the measured value is used to determine the dither amplitude value. The dither amplitude reference value is determined by correcting the dither amplitude reference value in accordance with the ratio between the data obtained as described above and reference data having the same dimension as the data determined under the assumption that the disturbance factor is in the reference state. It is the gist of that.

In order to achieve a seventh object, according to the invention described in claim 8, in the invention described in any one of claims 3 to 5, the dither control means controls the current flowing through the solenoid. The dither amplitude reference value is set in advance so that the desired current amplitude is obtained under the assumption that the influencing disturbance factor is in the reference state, and the target current value and the current command value are disturbed by the disturbance. The gist is that the dither amplitude value is determined by correcting the dither amplitude reference value according to the ratio compared in the same dimension under the assumption that the factor is in the reference state.

According to a ninth aspect of the present invention, in order to achieve the eighth object, in the invention of the eighth aspect, the control means performs feedback control of integral type control, and the dither control means performs the dither control. Determining means for determining whether or not the dither amplitude value obtained by correcting the amplitude reference value is within a predetermined range; and the determining means determines that the dither amplitude value is not within a predetermined range. In this case, there is provided amplitude value limiting means for limiting the dither amplitude value to an upper limit value or a lower limit value of a predetermined range.

In order to achieve the ninth object, in the invention according to claim 10, in the invention according to any one of claims 3 to 5, the dither control means may control a current flowing through the solenoid. The dither amplitude reference value is set in advance so that the desired current amplitude is obtained under the assumption that the influencing disturbance factor is in the reference state, and the current command value and the current detection value are determined by the disturbance. The gist is that the dither amplitude value is determined by correcting the dither amplitude reference value according to the ratio compared in the same dimension under the assumption that the factor is in the reference state.

According to the eleventh aspect of the present invention, in order to achieve the tenth object, in the first aspect of the present invention, the control means includes a detecting means for inputting from the current detecting means. The signal is a signal having a predetermined period, and the control means performs an even number of times of sampling so that the detection signal is sampled twice or more per period per a predetermined period of a natural number times the predetermined period. Do
Detected value calculating means for calculating the current detected value by averaging the even number of sampled values is provided.

In the twelfth aspect of the present invention,
In the invention according to any one of the eleventh aspects, the industrial vehicle is provided with the dither control device for the solenoid valve according to any one of the first to eleventh aspects.

(Operation) Therefore, according to the first aspect of the present invention, the current value of the solenoid valve provided on the oil passage of the hydraulic cylinder for driving the cargo handling equipment is controlled by the control means. Control such as speed control and stop control is performed. Data necessary for control for setting the current flowing through the solenoid to the target current value is measured by the measuring means. The control means executes a correction process for correcting a current command value for controlling a current flowing through the solenoid using data obtained from the measurement value measured by the measurement means based on the program data. The dither control means determines a dither amplitude value using data obtained by using the measurement value of the measurement means, and instructs a dither command value determined by adding the dither amplitude value to the current command value determined by the control means. For this reason, regardless of disturbance factors such as fluctuations in the power supply voltage and the solenoid resistance, a current flows through the solenoid according to a target current value that has a desired current amplitude. As a result, the spool always vibrates minutely with a desired amplitude. Therefore, if the amplitude of the spool becomes too large, the valve will open slightly when it should be closed, or it will appear as vibration of the cargo handling equipment. A decrease in the responsiveness of the valve is prevented.

According to the second aspect of the present invention, the dither control means is configured such that each time the control means executes the correction processing once, the dither control means generates a waveform having a predetermined cycle centered on the current command value determined by the control means. The dither command value is determined and issued by a plurality of interrupt processes in one cycle of the waveform so as to take the value of. As a result, the current flowing through the solenoid oscillates at a desired current amplitude in a predetermined cycle.

According to the third aspect of the present invention, the current flowing through the solenoid of the solenoid valve is detected by the current detecting means. The control means executes feedback control for correcting the current command value so that the difference between the current detection value determined from the detection signal of the current detection means and the target current value falls within an allowable range.
The dither control means determines a dither amplitude value using data obtained using the measurement value used in the feedback control.

According to the fourth aspect of the present invention, the dither amplitude value is determined by the dither control value using data obtained by the control means using the current detection value used in the feedback control.

According to the fifth aspect of the present invention, the disturbance factor affecting the current flowing through the solenoid is measured by the disturbance factor measuring means. The dither amplitude value is determined by the dither control means using data obtained by using the measured value of the disturbance factor used in the feedback control by the control means.

According to the sixth aspect of the present invention, the disturbance factor affecting the current flowing through the solenoid is measured by the disturbance factor measuring means. The control means executes feedforward control in which a current command value in which a disturbance factor is taken into consideration is determined from a target current value to give a command by using a measured value of the disturbance factor measuring means. The dither amplitude value is determined by the dither control means using data obtained by using the measured value of the disturbance factor measuring means.

According to the seventh aspect of the present invention, the dither amplitude reference value is set in advance so that a desired current amplitude can be obtained under the assumption that the disturbance factor is in the reference state. The dither control means determines the dither amplitude reference according to the ratio of the data obtained using the measurement value of the measurement means to the reference data having the same dimension as the data determined under the assumption that the disturbance factor is in the reference state. The dither amplitude value is determined by correcting the value.

According to the eighth aspect of the present invention, the dither amplitude reference value is set in advance so as to obtain a desired current amplitude under the assumption that the disturbance factor is in the reference state. The dither control means, based on the assumption that the disturbance factor is in the reference state, determines the dither amplitude reference value according to the ratio of the target current value and the current command value used in the feedback control by the control means in the same dimension. Is corrected to determine the dither amplitude value.

According to the ninth aspect, the control means executes feedback control of integral control. The dither control means determines whether or not the dither amplitude value determined by correcting the dither amplitude reference value according to the ratio of the target current value and the current command value in the same dimension is within a predetermined range. . In the feedback control of the integral control, the current command value is determined to be smaller than the target current value in a transition region until the current reaches the target current value. Therefore, the ratio of the target current value to the current command value in the same dimension is determined. Will not accurately reflect the effects of disturbance factors. However, if the determination unit determines that the dither amplitude value is not within the predetermined range, the current is stabilized at the target current value because the dither amplitude value is limited to the upper limit value or the lower limit value so as to fall within the predetermined range. Until then, even in the transition region, the amplitude of the spool is prevented from being abnormally too large or too small.

According to the tenth aspect, the dither amplitude reference value is set in advance such that a desired current amplitude can be obtained under the assumption that the disturbance factor is in the reference state. The dither control means determines the dither amplitude reference value according to a ratio of the current command value and the current detection value used by the control means in the same dimension under the assumption that the disturbance factor is in the reference state. Correction determines the dither amplitude value.

According to the eleventh aspect of the present invention, the control means inputs a detection signal having a predetermined period of amplitude from the current detection means. The detection value calculating means provided in the control means performs a total of even number of samplings so as to perform sampling twice or more per one period per a fixed time which is a natural number multiple of the period of the detection signal. Are averaged to calculate a current detection value.

According to the twelfth aspect of the present invention, the industrial vehicle is provided with the dither control device according to any one of the first to eleventh aspects. An effect similar to that of the invention described in any one of 11 is obtained.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 11, a forklift 1 as an industrial vehicle has a lift cylinder 3 for raising and lowering a fork 2 as a cargo handling device and a mast 4 on which the fork 2 is supported so as to be able to move up and down. A tilt cylinder 5 as a hydraulic cylinder is provided. The operator's cab 6 is equipped with a lift lever 7 that operates to extend and retract the lift cylinder 3 and a tilt lever 8 that operates to extend and retract the tilt cylinder 5. A hydraulic circuit shown in FIG. 12 for driving the lift cylinder 3 and the tilt cylinder 5 is provided on the vehicle body 1 a of the forklift 1.

The hydraulic circuit is configured as follows. FIG.
As shown in FIG. 1, a hydraulic pump 11 that pumps up and discharges hydraulic oil from an oil tank 10 is driven by an engine 12 (shown in FIG. 11). Line 13 from hydraulic pump 11
Hydraulic oil discharged through the passage is pressurized to a predetermined pressure or more by the flow divider 14 and then divided into the hydraulic circuit for the cargo handling system and the steering valve 15 for the steering system.

A hydraulic oil supply line 16 through which the pressure oil diverted from the flow divider 14 to the cargo handling system passes is connected to a return line 17 returning to the oil tank 10, and is connected to a manual switching valve 18 for lift and a tilt valve for tilt. The manual switching valve 19 is arranged in series on the hydraulic oil supply pipe 16.

The lift manual switching valve 18 is a three-position switching valve, and can be switched to three states a, b, and c by operating the lift lever 7 ascending, neutral, and descending. When the lift manual switching valve 18 is switched between the three states, the line 20 connected to the bottom chamber 3a of the lift cylinder 3, and the branch line 16a and the return line 17 are switched to a communicating / blocking state. .

The discharge pressure of the hydraulic pump 11 is transmitted to a pressure transmission line 21 connected to the line 13. A pressure reducing valve 22 is provided on the pressure transmission pipe line 21 to adjust the hydraulic pressure on the downstream side thereof to a predetermined pilot set pressure.

The tilt manual switching valve 19 is a three-position switching valve, and can be switched between three states a, b, and c by operating the tilt lever 8 backward, neutral, and forward. When the tilt manual switching valve 19 is switched between the three states, the pipe 23a connected to the rod chamber 5a of the tilt cylinder 5 and the pipe 23b connected to the bottom chamber 5b are
The state of communication is switched between the branch line 16b and the discharge line 24 in a communication / cutoff state. The tilt cylinder 5 is driven to contract when the tilt lever 8 is tilted rearward (state a), and is driven to extend when the tilt lever 8 is tilted forward (state c).

In this embodiment, since the stop control and the speed control of the mast 4 are performed independently of the operation of the tilt lever 8,
An electromagnetic valve 25 is provided on the pipe 23a so as to be arranged in series with the tilt manual switching valve 19 in the tilt-type oil passage. The solenoid valve 25 is connected to the control valve 2 provided on the pipe 23a.
6 and a proportional solenoid valve 27 provided on the pressure transmission line 21 for adjusting the pilot pressure for driving the spool of the control valve 26. Tilt cylinder 5
The speed control and the stop control are performed by controlling the current value of the current flowing through the solenoid 25a of the solenoid valve 25.

The relief valve 28 is a manual switching valve 1 for lift.
8 is switched to the state a (up position), the pipe line 29 is set so that the oil passage of the lift system has a predetermined pressure (lift set pressure).
This is for allowing excess hydraulic oil to escape via the. Further, the relief valve 30 is configured such that the tilt manual switching valve 19 is a
When the mode is switched between the state (backward tilting position) and the state c (forward tilting position), extra oil is supplied via the pipe line 31 so that the tilt-type oil passage has a predetermined pressure (tilt setting pressure). This is for releasing hydraulic oil. Check valves 32 and 3
Reference numerals 3 and 34 are for preventing backflow of hydraulic oil, and a filter 35 is for removing dust in oil from flowing to the solenoid valve 25. The pipes 16b, 23a, 2
3b and 24 constitute a tilt type oil passage.

In this embodiment, the controller 40 shown in FIG. 8 controls the solenoid valve 25 by controlling the current value to control the opening thereof, thereby performing tilt control such as speed control and stop control of the mast 4. The forklift 1 includes a lift sensor 41 and a tilt angle sensor 4 as sensors for obtaining control information necessary for performing tilt control as a detection value.
2, a pressure sensor 43, a forward tilt switch 44, a backward tilt switch 45, and an operation switch 46 are provided. Note that these sensors 41 to 46 constitute detection means.

The lift sensor 41 is provided on the upper part of the outer mast 4a, and is turned on when the fork 2 is at a height higher than a predetermined height and turned off when the fork 2 is at a low height less than the predetermined height. It has become. The lift sensor 41 is, for example, a proximity sensor. The tilt angle sensor 42 is for detecting the attitude angle of the tilt cylinder 5 and indirectly detecting the tilt angle (tilt angle) of the mast 4, and outputs a detection signal corresponding to the tilt angle of the mast 4. It has become. The tilt angle sensor 42 includes, for example, a potentiometer. Further, the pressure sensor 43 is connected to the lift cylinder 3
And outputs a detection signal corresponding to the weight of the load (loaded load) loaded on the fork 2.

The forward tilt switch 44 is for detecting that the tilt lever 8 has been tilted forward, and the backward tilt switch 45 is for detecting that the tilt lever 8 has been tilted backward. Both switches 44 and 45 are, for example, micro switches. The operation switch 46 is provided on the knob 8a of the tilt lever 8, and is used by an operator to operate the tilt lever 8 when the fork 2 is to be automatically stopped in a horizontal posture.

Next, the electrical structure of the tilt control device provided in the forklift 1 will be described with reference to FIGS. The controller 40 includes the microcomputer 5
0, a solenoid drive circuit 51, a current detection circuit 52, and a low-pass filter (RC low-pass filter) 53. The microcomputer 50 constitutes a control means and a dither control means, and also has a central processing unit (hereinafter referred to as a CP) as a judgment means, an amplitude value limiting means and a detection value calculation means.
U), a read-only memory (RO) which constitutes control means and dither control means and serves as storage means.
M) 55, EEPROM (Electrical Erasable Pro)
grammable ROM) 56 and a readable and rewritable memory (RAM) 57. In addition, a measuring unit and a current detecting unit are configured by the current detecting circuit 52 and the low-pass filter 53. The CPU 54 includes a lift sensor 41, a forward tilt switch 44,
The backward tilt switch 45 and the operation switch 46 are connected via an input interface (not shown), and the tilt angle sensor 42 and the pressure sensor 43 are connected via an A / D conversion circuit (not shown) and the input interface. Connected. Output interface to CPU 54 (not shown)
The positive terminal of a battery 58 as a power supply and a first end of a solenoid 25a are connected to the solenoid drive circuit 51 connected through the solenoid. The second end of the solenoid 25a is connected to the current detection circuit 52, and the current flowing through the solenoid 25a is detected by the current detection circuit 52. The detection signal S2 output from the low-pass filter 53 that receives the detection signal (detection voltage) S1 detected by the current detection circuit 52 is C
It is input to PU54.

As shown in FIG. 6, the CPU 54 has a PWM port 59. When a duty output value Dout as a dither command value determined in a current value control process (FIG. 1) and a dither control process (FIG. 2), which will be described later, executed by the CPU 54 is written in the PWM port 59, the duty output value Dout Is a duty value (%) of 2 kHz P
A WM signal is generated and output (however, the Dout value is actually bit data).

The solenoid drive circuit 51 has a transistor 6 connected so that a PWM signal is input to the base.
0 is built in. The transistor 60 has a collector connected to the positive terminal of the battery 58 and an emitter connected to the first end of the solenoid 25a. When the transistor 60 is turned on and off based on the PWM signal, the current flowing through the solenoid 25a is duty-controlled.

The current detection circuit 52 includes a resistor R4 connected in series with the solenoid 25a, and outputs a detection signal S1 obtained by amplifying a voltage applied to both ends of the resistor R4 via an amplifier 61. The low-pass filter 53 is for removing a 2 kHz ripple from the detection signal S1. The band limit frequency (cutoff frequency) is set to, for example, 500 Hz. The CPU 54 detects the detection signal S
2 is input from the A / D port 62.

The CPU 54 is provided with a counter 63. The counter 63 is used for measuring an interrupt time when a dither control process described later is executed in the interrupt process.

The ROM 55 stores program data of the current value control process shown in FIG. 1 for determining the duty output center value Dcent as a current command value for determining the duty value (%) of the PWM signal. . The program data of the current value control processing is for performing feedback control for correcting the duty output center value Dcent so that a current detection value, which will be described later, determined from the detection signal S2 approaches the target current value. It is what is performed.

In the present embodiment, dither control is employed in which the spool of the solenoid valve 25 is minutely vibrated to reduce the frictional resistance at the start of the operation and improve the response. A duty output value D that allows the current flowing through the solenoid 25a to be minutely amplitude at, for example, 100 Hz for dither control.
out (%) command. Therefore, the duty output value Do
ut is the duty output center value Dce determined every 10 milliseconds
From nt, this value is determined as a value on a sine wave having an amplitude of 100 Hz with 8 times / 10 msec interrupt processing. The ROM 55 stores program data of a dither control process shown in FIG. 2 for executing this interrupt process. The writing of the duty output value Dout to the PWM port 59 by the CPU 54 is performed 8 times / 10 ms, so that the PWM port 59 corresponds to a value on a 100 Hz sine wave centered on the duty output center value Dcent. A PWM signal having a duty value (%) is output.

In this embodiment, the duty output value Dout
Is obtained by adding a correction for the dither amplitude to the duty output center value Dcent. That is, the equation Dout = Dcen
Calculated by t + Ddizz. Here, Ddizz is a dither amplitude value that takes a value on a sine wave corresponding to the correction amount for the amplitude for dither control. Since the Ddizz value takes a value on a sine wave, the Ddizz value changes depending on the number of times the interrupt processing is performed. The dither amplitude value Ddi is stored in the ROM 55.
In order to determine zz, the dither amplitude reference value D [cn shown in FIG.
t] is stored. This data indicates that the battery voltage VB is equal to the reference voltage Vbase (for example, 90 V when fully charged).
%), And a reference resistance value Rbase when the solenoid resistance Rsol of the solenoid valve 25 is at a reference temperature (for example, a resistance value at normal temperature).
It is set on the assumption that it is in the reference state.
The dither amplitude reference value D [cnt] is a dither amplitude value (%) required to obtain a current amplitude Idizz (see FIGS. 4 and 5) required for dither control, and a count value “ cnt ”. Therefore, when the battery voltage VB and the solenoid resistance Rsol deviate from the reference state, the dither amplitude reference value D [cnt] is appropriately corrected to determine the dither amplitude value Ddizz.

The dither amplitude reference value D [cnt] is generally D [cnt] = sin if the number of interrupts per cycle is “n”.
((Cnt / n) · 2π) (cnt = 0, 1, 2,..., N). In the present embodiment, the number of interrupts n per cycle n
= 8, D [0] = 0, D [1] = Dmax
/ √2, D [2] = Dmax, D [3] = Dmax / √2, D
[4] = 0, D [5] =-Dmax / √2, D [6] =-
Dmax, D [7] = − Dmax / √2 are stored as data. Here, Dmax is the amplitude of the duty value.

FIG. 5 is a graph showing the relationship between the target current value Iaim and the duty value (%). In this graph, a reference line L plots a duty output center value Dcent (%) necessary for flowing a current of the target current value Iaim when a reference state (battery voltage VB = Vbase and solenoid resistance Rsol = Rbase) is assumed. Line. Under the reference state, the amplitude of the duty value required to obtain the current amplitude Idizz required for dither control is Dmax (%) as can be seen from the reference line L.

As shown in the graph of FIG.
Duty output center value Dcent required to obtain aim
Shifts to a direction in which the inclination with respect to the reference line L increases as the battery voltage decreases and the solenoid resistance increases, and the inclination decreases with respect to the reference line L as the battery voltage increases and the solenoid resistance decreases. Shift in the following direction. For this reason, the duty value (%) of the amplitude required to obtain the current amplitude Idizz changes according to the change in the slope of the line Dcent. In the dither control process of FIG. 2, a process of correcting the dither amplitude reference value D [cnt] so as to obtain an appropriate dither amplitude value Ddizz in accordance with the degree of change from the reference state of the battery voltage VB and the solenoid resistance Rsol. I do.

In this embodiment, since the dither control is performed, the current detection circuit 52 outputs 2 kHz and 1 kHz as shown in FIG.
The detection signal S1 with the ripple of 00 Hz is output.
From the low-pass filter 53, the detection signal S1 is changed to 2 kHz.
7B with only the ripples of z removed.
A detection signal S2 that draws a sine wave of Hz is output. CP
U54 performs a filtering process to cut off a ripple of 100 Hz from the detection signal S2 input from the A / D port 63. That is, as shown in FIG. 7C, the CPU 54 executes an even number of samplings (four times at the black spot in FIG. 7 in this embodiment) in one cycle of the detection signal S2 in the interrupt processing, and performs one cycle worth of sampling. Each time an even number of sampled values are obtained, they are averaged to calculate the center of amplitude of the detection signal S2, and this is used as a current detection value Idet. It is sufficient that the number of samplings of the detection signal S2 per cycle be an even number of 2 or more. Also, the reason why the low-pass filter 53 does not remove the ripple of 100 Hz is that the delay of the signal when passing through the low-pass filter 53 is minimized,
This is because the current detection value Idet is obtained in a state close to real time with a minimum phase delay.

Next, each program data of the current value control processing and the dither control processing will be described. First, the current value control process will be described with reference to FIG. Step 10 is
This is a data reading process for reading necessary data.
In this process, the target current value Iaim, the current detection value Idet, and the previous duty output center value Dcent are read. here,
The target current value Iaim is a target current value to be passed through the solenoid 25a, and the sensors 41 to 46 are stored in the ROM 55 using data to be described later (for example, FIG. 9).
It is a value determined based on the detection signal (detection value) from.

In step 20, the target current value Iaim is "0
This is a process for determining whether or not "ampere".
Step 30 is a process for obtaining a difference ΔI between the target current value Iaim and the current detection value Idet. The difference ΔI is given by the equation Δ
It is calculated by I = Iaim-Idet.

Step 40 is a duty output center value D
This is the process of calculating cent. Duty output center value Dce
The nt is determined by correcting the previous duty output center value Dcent by a correction amount ΔI · G proportional to the difference ΔI, and the expression Dcent
= Dcent + G · ΔI. Here, the feedback control in the present embodiment corresponds to integral control in which a correction amount proportional to the difference ΔI is added to the previous duty output center value Dcent. The gain G is in a reference state (battery voltage VB = Vbase and solenoid resistance Rsol =
Rbase) is a gain determined from the transfer function of the integral control in consideration of the stability of the control system. The stability of the control system means that overshooting in the transient region of the current is suppressed and a design condition that can ensure high responsiveness is satisfied.

In step 50, the target current value Iaim is set to "0".
Ampere ", the duty output center value Dcent = 0
(%) Is set. Step 60 is a process of storing (storing) the current (current) duty output center value Dcent for use in the next process. This duty output center value Dcent is stored in a predetermined area of the RAM 57.

Next, the dither control processing will be described with reference to FIG. Step 210 is a data reading process for reading necessary data. In this process, the target current value Iaim and the duty output center value Dcent are read.

Step 220 is a process for obtaining the duty reference value Dbase from the target current value Iaim. The duty reference value Dbase is calculated by the formula Dbase = K · Iaim. Here, “K” is a conversion coefficient for converting the target current value Iaim into a duty value (%) under the assumption of the reference state, and is a value corresponding to the slope of the reference line L in FIG.

Step 230 is a process for determining whether or not the target current value Iaim is "0 amperes". Steps 240 to 260 are counter processes for determining a count value cnt for determining a dither amplitude reference value D [cnt] to be adopted. Step 240 is the counter 63
This is a process for determining whether or not the count value cnt of is equal to or greater than “7”. Step 250 is a process for incrementing the count value cnt when the count value cnt is less than “7”. Step 260 is a count value
This is processing for resetting the count value cnt to “0” when cnt is a value equal to or greater than “7”.

Step 270 is a process for calculating the dither amplitude value Ddizz. The dither amplitude value Ddizz is calculated by multiplying the dither amplitude reference value D [cnt] by the ratio “Dcent / Dbase” between the duty output center value Dcent and the duty reference value Dbase (Ddizz = D [cnt] · Dcent / Dbas).
e).

Steps 280 to 310 are processes for keeping the dither amplitude value Ddizz between the upper limit value and the lower limit value. Steps 280 and 290 are processing for keeping the dither amplitude value Ddizz below the upper limit, and steps 300 and 310 are processing for the dither amplitude value Ddi.
This is processing for keeping zz at or above the lower limit. The upper limit of the dither amplitude value Ddizz is as follows if the dither amplitude value Ddizz exceeds twice the dither reference value D [cnt] in step 280.
In step 290, the upper limit is determined to be “2D [cnt]”. The lower limit of the dither amplitude value Ddizz is that the dither amplitude value Ddizz is equal to the dither reference value D [cnt] in step 300.
If it is less than one-half, in step 310 the lower limit value is determined to be “D [cnt] / 2”.

In step 320, the duty output value Dou
This is a process for calculating t. The duty output value Dout is obtained by adding the dither amplitude value Ddizz to the duty output center value Dcent (Dout = Dcent + Ddizz). If a value inappropriate for control as the duty output value Dout, that is, a value outside the range of 0% to 100%, is calculated, 1
It is set so that when it exceeds 00%, it is corrected to "100%", and when it is less than 0%, it is corrected to "0%".

Step 330 is a process for setting the duty output value Dout = 0 when the target current value Iaim is "0 amperes". Step 340 is a process of writing the duty output value Dout to the PWM port 59.
This writing process corresponds to a dither command value command.

In the ROM 55, in addition to the program data of the current value control processing and the dither control processing, the tilt control of the mast 4 performed by the current value control of the solenoid valve 25, that is, the forward lean control, the automatic horizontal stop control, the backward lean Speed control,
Program data for shockless control or the like is stored. The CPU 54 determines which of the tilt controls should be executed based on the detection signals input from the sensors 41 to 46, and manages this as a tilt mode. Then, the target current value Iaim is determined according to the current tilt mode.

Next, the tilt control will be described. The forward leaning restriction control is to raise the forward leaning angle of the mast 4 from time to time so that when the mast 4 is tilted forward, the center of gravity of the vehicle is shifted too far and an unstable state such as the rear wheel is lifted is not caused. This is a control that regulates according to the height and the load. In the present embodiment, this control is performed only when the height sensor 41 is turned on and the height is high, and the maximum allowable forward inclination angle θk of the mast 4 is determined by using the map shown in FIG. I decide to decide. This map is stored in the EEPROM 57. Even when the tilt lever 8 is being tilted forward, the mast 4 is forcibly stopped at the maximum allowable forward tilt angle θk determined from the map when the load is high and the load is higher than Mo.

The automatic horizontal stop control means that the operation switch 46
When the tilt lever 8 is operated while pressing, the tilt angle is monitored, and the mast 4 is automatically stopped when the fork 2 is in the horizontal posture. The backward tilt speed control is a speed control that switches the backward tilt speed of the mast 4 stepwise (two steps in this embodiment) according to the lift, and limits the backward tilt speed of the mast 4 at a high lift. It is.

The shockless control is a control for reducing the impact when the mast 4 is stopped by previously decelerating the mast 4 before stopping it for the stop control. This shockless control is executed when the mast is stopped during forward leaning restriction control, automatic horizontal stop control, and backward lean manual operation. The EEPROM 57 stores, as necessary data for the shockless control, a deceleration start angle θo from the stop angle (specifically, the forward lean regulation angle θk, the horizontal set angle, the rearward lean end angle) θs of the mast 4 and the deceleration at that time. Data for determination is stored (see FIG. 9). In addition, EEPRO
The data of M57 can be individually set for each machine by operating a setting operation unit (not shown) in consideration of the type of vehicle, the type of vehicle, the variation in device accuracy, and the like.

The ROM 55 stores a target current value Iaim
Are set as shown in FIG. 9 according to various tilt modes. The target current value Iaim in the tilt mode in which the mast 4 is tilted at a constant speed when the tilt lever 8 is operated (forward tilt manual, rear tilt manual, forward tilt automatic horizontal, rearward tilt automatic horizontal) is basically controlled by a normal control. The maximum current value In of the current range to be used is set. However, the intermediate current value Im is set only at the time of high-elevation backward tilt because it is necessary to limit the mast backward tilt speed. Further, the target current value Iaim in the shockless mode has a constant gradient from the current value (normally In or Im) at the deceleration start angle θo to the valve closing current Iclose for closing the solenoid valve 25 at the stop angle θs. It is set to decrease. In the tilt-off mode in which the tilt lever 8 is not operated and in the tilt-inhibited mode in which the mast 4 is inhibited from tilting, the target current value Iaim is set to "0 amperes".

Next, the operation of the tilt control device will be described. When the key is turned on, the engine 12 is started, and the driving of the hydraulic pump 11 is started. After starting the engine, the oil pressure in the pressure transmission line 21 reaches the pilot set pressure. The hydraulic oil discharged from the hydraulic pump 11 is boosted to a predetermined pressure in the flow divider 14, and is then diverted to a cargo handling system and a steering system.

During key-on, the CPU 54 executes the current value control process shown in FIG. 1 every 10 milliseconds, for example. CPU5
Reference numeral 4 denotes a tilt mode (forward lean manual, backward lean manual, forward lean automatic horizontal, backward lean automatic horizontal, shock tilt) according to the control to be currently executed based on the input signals from the sensors 41 to 43 and the switches 44 to 46. And the target current value Iaim corresponding to the tilt mode is obtained.

The CPU 54 converts the detection signal S1 (FIG. 7 (b)) from the detection signal S1 (FIG. 7 (a)) detected by the current detection circuit 25a through the low-pass filter 53 from which the 2 kHz ripple has been removed. Input from the / D port 62. The CPU 54 responds to the input detection signal S2 in FIG.
As shown in (c), an even number (four times) of sampling is executed by interrupt processing in one cycle, and a filter processing is performed by averaging each time an even number of sampling values of one cycle is obtained, thereby obtaining a current detection value. Get Idet. Since the removal of the ripple of 100 Hz is performed by the filter processing, the current detection value Idet can be obtained in a state close to real time with a very small phase delay.

For example, when the tilt lever 8 is not operated, the target current value Iaim “0” in the tilt-off mode is set.
Ampere ". When the target current value Iaim = 0,
The CPU 54 sets the duty output center value Dcent = 0 (S50), stores the data in the RAM 57 (S60), and ends this program. And 8
D every time in the interrupt processing of the dither control processing every 10 milliseconds
out = 0 (%) is written to the PWM port 59 (S
330, S340). Thus, the target current value Iaim = 0
In the case of, the duty output value Dou is corrected without correcting the Dcent value.
Since t is forcibly set to 0%, it should be 0%, but Dcent is corrected and Dout> 0 is caused.
Is prevented from slightly opening.

When the tilt lever 8 is operated, the target current value Iaim is usually determined to be In or Im. The CPU 54 reads the various data Iaim, Idet, and the previous Dcent, and calculates the difference ΔI. In the first process at the start of the operation of the tilt lever 8, the current detection value I is set before the solenoid 25a is energized.
Since det is “0”, ΔI = Iaim is calculated (S
30). Then, the CPU 54 calculates the current duty output center value Dcent = Dcent + G · ΔI (S40), and stores it in a predetermined storage area of the RAM 57 for use in the next processing (S60).

In the first processing at the start of the operation of the tilt lever 8, the initial value Dcent of the duty output center value Dcent = G · Iaim is determined because Dcent = 0 in the previous operation. Hereinafter, in the current value control process executed every 10 milliseconds, feedback control (integration type) in which the correction amount (= G · ΔI) obtained by multiplying the difference D by the gain G by the difference ΔI (= Iaim−Idet) is added to the previous Dcent. Control), the duty output center value Dcent is sequentially determined every 10 milliseconds.

The CPU 54 executes the dither control processing (FIG. 2) every time the duty output center value Dcent is determined every 10 milliseconds.
Is executed eight times / 10 ms in the interrupt process. The dither control process is executed as follows based on FIG.

When the CPU 54 first reads the target current value Iaim and the duty output center value Dcent (S210),
From the target current value Iaim, the duty reference value Dbase = K · Ia
Calculate im. After the start of the operation of the tilt lever 8, the target current value Iaim is not "0 amperes".
4 performs counter processing of the counter 63 (S240 to S240).
260). In the first interrupt processing, the count value cnt of the counter 63 is "7", and the counter 63 is first reset (S260). And count value cnt
Is used as the dither amplitude reference value D [cnt] and the duty output center value Dcent, and the dither amplitude value Ddizz = D
“Cnt” · Dcent / Dbase is calculated (S270).
That is, an appropriate dither amplitude value Ddizz in which the dither amplitude reference value D [cnt] is corrected according to the battery voltage VB and the solenoid resistance Rsol at that time is determined.

The dither amplitude value Ddizz is D [cnt] / 2 ≦ Dd
If it is in the range of izz ≦ 2D [cnt] (S280, S30
0), the value is adopted. If the dither amplitude value Ddizz is a value of Ddizz> 2D [cnt] (S280), Ddiz
z is the upper limit 2D [cnt], and dither amplitude Ddizz is Ddizz.
If the value is <D [cnt] (S300), Ddizz is determined to be the lower limit D [cnt] / 2. When the dither amplitude value Ddizz is determined, it is changed to the duty output center value Dcent.
In addition, the duty output value Dout = Dcent + Ddizz is calculated (S320). And 0-10 if necessary
After being corrected to a value within the range of 0%, the duty output value D
out (%) is written to the PWM port 59.

When the first interrupt processing is completed,
Thereafter, the second and subsequent interrupt processes are sequentially performed at predetermined time intervals (1.25 milliseconds). In the second and subsequent interrupt processing, the count value cnt is sequentially set to cnt = 1, 2,..., 7, and the dither amplitude reference value D [cnt] (cnt = 1, 2,...) Determined according to the count value cnt …, 7) (Dcent / Dba
The dither amplitude value Ddizz is determined by multiplying by (se). Then, the dither amplitude value Ddizz is set to the duty output center value D.
and the duty output value Dout = Dcent + Ddizz (= Dcent + D [c
nt] · Dcent / Dbase (however, cnt = 1, 2, ...,
7)) is calculated. If Ddizz> 2D [cnt] or Ddizz <D [cnt], the duty output value Dout is determined by setting Ddizz as the upper limit 2D [cnt] or the lower limit D [cnt] / 2, respectively. The duty output value Dout (%) corrected to a value within the range of 0 to 100% as required at each time is written to the PWM port 59 every time.

Thus, the duty output center value Dcent is 1
The duty output value Dout determined by the dither control process is written to the PWM port 59 at a rate of 8/10 ms every time the determination is made every 0 milliseconds, so that the duty value (%) from the PWM port 59 becomes the Dcent value. , A PWM signal having a small amplitude at 100 Hz is output. When the transistor 60 is turned on and off based on the PWM signal, a current having a small amplitude at 100 Hz flows through the solenoid 25a.

In a steady state where the current flowing through the solenoid 25a has settled at the target current value Iaim, the duty output center value Dcent finally settles at the duty output center value Dcent according to disturbance factors such as fluctuations in the battery voltage and solenoid resistance at that time. Become. The line in which the duty output center value Dcent at this time is plotted against the target current value Iaim is shown in FIG.
As shown in the figure, the inclination shifts from the reference line L as the battery voltage decreases and the solenoid resistance increases, and the inclination decreases from the reference line L as the battery voltage increases and the solenoid resistance decreases. Shift to At this time, the dither amplitude value Ddizz for determining the amplitude of the current does not use the fixed reference value D [cnt] as it is,
An appropriate value that takes into account the disturbance factor obtained by multiplying the reference value D [cnt] by the ratio “Dcent / Dbase” is used as the dither amplitude value Ddizz using a Dcent value that takes a value reflecting the disturbance factor at that time. .

For example, as shown in FIG.
When the solenoid resistance is large, the ratio (Dcent / Dbase)> 1. Therefore, the duty value of the PWM signal is determined so as to draw the sine wave Sx in FIG. When the battery voltage is large and the solenoid resistance is small, the ratio (Dcent / Dbase) <1. Therefore, the PW is drawn so as to draw a sine wave Sy of FIG.
The duty value of the M signal is determined. For this reason, the current flowing through the solenoid 25a always oscillates at a required constant amplitude Idizz irrespective of disturbance factors due to fluctuations in battery voltage and solenoid resistance, and the spool of the solenoid valve 25 (specifically, the spool of the proportional solenoid valve 27) Micro-vibration always occurs at a constant amplitude (except when the valve is closed).

Therefore, the frictional resistance at the start of the operation of the spool of the solenoid valve 25 is reduced, the movement of the spool becomes smooth, and the responsiveness of the solenoid valve 25 is improved. Therefore, when the amplitude of the spool of the solenoid valve 25 becomes too small and the response of the solenoid valve 25 decreases, or when the amplitude of the spool of the solenoid valve 25 is too large to be opened, the solenoid valve 25 may be erroneously opened. The occurrence of a problem of opening the valve even slightly is prevented. As a result, the good responsiveness of the solenoid valve 25 ensures the good responsiveness of the mast 4 when the tilt lever is operated. In addition, problems such as minute vibration during the tilting operation of the mast 4 due to excessive amplitude of the spool of the solenoid valve 25 and minute displacement of the mast 4 when the tilting operation is stopped do not occur.

In the transient region of the current, the duty output center value Dcent takes a value smaller than the value that finally converges. In this case, the ratio (Dcent / Dbase) does not accurately reflect the influence of disturbance factors, and if the dither amplitude value Ddizz obtained using the ratio (Dcent / Dbase) is used, the current amplitude becomes excessive. Is worried. However, step 280
In step 310, the dither amplitude value Ddizz becomes D
If it is out of the range of [cnt] / 2 ≦ Ddizz ≦ 2D [cnt], the Ddizz value becomes the upper limit 2D [cnt] or the lower limit D [c
nt] / 2, so that the amplitude of the current is prevented from being abnormally large in the transient region of the current. Therefore,
The problem that the mast 4 rattles in the transition region of the current does not occur.

According to the above-described embodiment, the following effects can be obtained. (1) As for the dither amplitude value Ddizz, the ratio of the Dcent value and the Dbase value reflecting the disturbance factor due to the fluctuation of the battery voltage and the solenoid resistance is used to determine the disturbance factor. The spool of the solenoid valve 25 can be minutely vibrated at a required constant amplitude without being affected by factors. Therefore, the amplitude of the spool of the solenoid valve 25 is too small to deteriorate the responsiveness of the mast 4 at the time of starting, the minute vibration at the time of tilting of the mast 4 due to the too large amplitude of the spool, When the valve 25 is to be closed, the valve is opened very slightly, and problems such as the microscopic displacement of the mast 4 can be reliably prevented.

(2) The ratio (Dce
nt / Dbase) does not accurately reflect the influence of disturbance factors, the dither amplitude value Ddizz is kept within a predetermined range (D [cnt] / 2).
≦ Ddizz ≦ 2D [cnt]), it is possible to limit the abnormally large amplitude of the spool of the solenoid valve 25 even if the feedback control of the integral type control that easily realizes the stable control is adopted. Therefore, the mast 4 caused by the excessive amplitude of the spool in the transient region of the current.
Vibration can be prevented.

(3) Since the data of the duty output center value Dcent for determining the current value for feedback control is used to determine the dither amplitude value Ddizz, the data for determining only the dither amplitude value Ddizz is used. No acquisition process is required.

(4) The solenoid current can be controlled stably regardless of disturbance factors without providing a relatively expensive regulator between the battery 59 and the solenoid 25a. (5) Only the 2 kHz ripple is removed by the low-pass filter 53, and the 100 Hz ripple is removed by the filtering process by the CPU 54 so as to minimize the signal delay in the low-pass filter 53. It can be obtained in near real time. Therefore, a sufficiently responsive feedback control can be realized.

(6) Since the feedback control is performed by software by the CPU 54, the low-pass filter 53 is added, but the triangular wave generation circuit, the duty generation circuit, and the feedback circuit, which are necessary in the conventional device for performing feedback control by hardware, are provided. This can be omitted, and the hardware required for feedback control can be simplified.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, the battery voltage VB, which is one of the main disturbance factors causing fluctuations in the current flowing through the solenoid 25a, is measured and monitored, and the duty output center value Dcent and the dither Amplitude value Ddi
This is an example where zz is determined. Only the program data of the current value control process is different from that of the first embodiment, and other processes including the dither control process are the same as those of the first embodiment. The configuration of the device is the same as that of the first embodiment except that a circuit for detecting a battery voltage is added. Therefore, only the different parts will be described below.

FIG. 15 is a schematic diagram of the electric configuration. CPU5
A plus terminal of a battery 58 as a power supply is connected to the A / D port 64 of the fourth through a resistor Rb as a measuring means and a disturbance factor measuring means. The CPU 54 converts the battery voltage VB into a voltage signal obtained by reducing the voltage by the resistors Rb and Rc.
/ D port 64, and a battery voltage detection value Vbatt is obtained from this voltage signal.

As in the first embodiment, the ROM 55 has the configuration shown in FIG.
The data indicating the relationship between the dither amplitude reference value D [cnt] per cycle and the count value cnt shown in FIG. That is, D [0] = 0, D [1] = Dmax / √
2, D [2] = Dmax, D [3] = Dmax / √2, D
[4] = 0, D [5] =-Dmax / √2, D [6] =-
Dmax, D [7] =-Dmax / √2. However,
Dmax is the amplitude (%) of the duty value for dither control
It is.

The ROM 55 stores the program data of the current value control processing shown in FIG. 13 and the program data of the dither control processing shown in FIG. The dither control processing is executed by 8 times / 10 millisecond interrupt processing each time the current value control processing is performed. Further, the CPU 54 executes a filtering process for averaging the sampling values and calculating the current detection value Idet in order to obtain the amplitude center value of the detection signal S2 as in the first embodiment.

Hereinafter, each program data of the current value control processing and the dither control processing will be described. First, the current value control process will be described with reference to FIG. Step 51
0 is a data reading process for reading necessary data. In this process, the target current value Iaim and the current detection value Id
et, the battery voltage detection value Vbatt, and the previous duty output center value Dcent are read.

Step 520 is a process for determining whether or not the target current value Iaim is "0 amperes". Step 530 is processing for obtaining a difference ΔI between the target current value Iaim and the current detection value Idet. Difference ΔI
Is calculated by the formula ΔI = Iaim−Idet.

Steps 540 and 550 are processes for determining the lower limit of the gain, and steps 560 and 570 are processes for determining the upper limit of the gain. If the battery voltage detection value Vbatt exceeds twice the reference voltage Vbase in step 540,
In step 550, the lower limit is determined to be "Go / 2". If the battery voltage detection value Vbatt is less than の of the reference voltage Vbase in step 560, the upper limit of the gain is determined to be the upper limit value “2Go” in step 570.

Here, the feedback control in the present embodiment also corresponds to integral type control in which a correction amount proportional to the difference ΔI is added to the previous duty output center value Dcent, as in the first embodiment. The reference gain Go refers to a reference state (battery voltage VB = Vbase and solenoid resistance Rsol
= Rbase) is a gain (proportional constant) determined from the transfer function of the integral control in consideration of the stability of the control system. Note that the stability of the control system is to satisfy a design condition that suppresses overshoot in a transient region of current and ensures high responsiveness.

Step 580 is a process for calculating a gain G according to the battery voltage VB at that time. The gain G is obtained by correcting the reference gain Go according to the battery voltage detection value Vbatt, and the equation G = Go · Vbase /
Calculated by Vbatt. That is, the gain G is determined by correcting the reference gain Go in consideration of the battery voltage VB which is one of the main causes of the disturbance.

Step 590 is a process for calculating the duty output center value Dcent. Duty output center value D
cent is the correction amount G at the previous duty output center value Dcent.
· Determined by adding ΔI, the formula Dcent = Dcent + G · Δ
I.

In step 600, when the target current value Iaim is "0 amps", the duty output center value Dcent
= 0 (%). Step 610 includes:
This is a process of storing (storing) the current duty output center value Dcent for use in the next process. This duty output center value Dcent is stored in a predetermined area of the RAM 57.

Next, the dither control processing will be described with reference to FIG. Step 710 is a data reading process for reading necessary data. In this process, the target current value Iaim, the detected battery voltage value Vbatt, and the duty output center value Dcent are read.

Step 720 is a process for determining whether or not the target current value Iaim is "0 amperes". Steps 730 to 750 are counter processes for the count value cnt for determining the dither amplitude reference value, and are the same processes as S230 to S250 in the first embodiment.

Step 760 is a process for calculating the dither amplitude value Ddizz. The dither amplitude value Ddizz is obtained by multiplying the dither amplitude reference value D [cnt] by the ratio “Vbase / Vbatt” between the battery voltage detection value Vbatt and the reference voltage Vbase, and is obtained by the equation Ddizz = D [cnt] · Vbase / Vbatt. Is calculated.

In step 770, the duty output value Dou
This is a process for calculating t. The duty output value Dout is obtained by adding the dither amplitude value Ddizz to the duty output center value Dcent (Dout = Dcent + Ddizz).

Steps 780 to 810 are processes for keeping the calculated duty output value Dout within the range of 0 to 100%, and are not shown in the flowchart of FIG. 2 in the first embodiment. If Dout <0 in step 780, the Dout value is corrected to “0%” in step 790. Step 800
If Dout> 100%, the Dout value is corrected to “100%” in step 810. Step 7
The process of 90 also serves to set the duty output value Dout = 0 (%) when the target current value Iaim is “0 amperes”.

At step 820, the duty output value Dou
This is the process of writing t to the PWM port 59. Next, the operation of the tilt control device will be described.

During key-on, the CPU 54 executes a current value control process shown in FIG. 13 every 10 milliseconds, for example, to determine a duty output center value Dcent. The target current value Iaim is determined according to a tilt mode determined based on input signals from the sensors 41 to 46, and the current detection value Idet is determined by the CPU.
54 is obtained by a filtering process in which the detection signal S2 input from the A / D port 63 is sampled an even number of times and averaged. The CPU 54 receives a voltage signal proportional to the battery voltage VB from the A / D port 64 to obtain a battery voltage detection value Vbatt.

The CPU 54 reads necessary data Iaim, Idet, Vbatt, and the previous Dcent every 10 milliseconds. For example, when the tilt lever 8 is not operated, the duty output center value Dcent = 0 is stored in the RAM 57 every time in the current value control process (S600, S610), and the dither control process is performed eight times / 10 milliseconds. Dout = 0 (%) is written to the PWM port 59 every time in the loading process (S790, S820).

When the tilt lever 8 is operated, the target current value Iaim becomes a value other than 0 (S520), and feedback control for correcting the duty output center value Dcent so that the current detection value Idet approaches the target current value Iaim is performed. Will be At this time, the gain G used to determine the duty output center value Dcent is determined according to the battery voltage detection value Vbatt at that time in the processing of S540 to S580.

The gain G is specified as follows. In many cases where the battery voltage detection value Vbatt satisfies Vbase / 2 ≦ Vbatt ≦ 2Vbase, the gain G is calculated by the formula Go · Vbase / Vb.
It is calculated by att (S580). Vbatt> 2Vbase
When the condition is satisfied, the gain G is set to the lower limit value “Go / 2” (S540, S550). Also, Vbatt <Vbase
When / 2 is satisfied, the gain G is set to the upper limit value “2Go” (S560, S570).

When the gain G is determined, this gain G is used to add a correction amount G · ΔI proportional to the difference ΔI = Iaim−Idet to the previous Dcent each time, so that the present duty output center value Dcent = Dcent + G · ΔI Is determined by calculation (S590). This duty output center value D
The cent is stored in a predetermined storage area of the RAM 57 for use in the next processing (S610).

When the operation of the tilt lever 8 is started, 1
Every time the current value control process is performed every 0 milliseconds, the gain G determined from the battery voltage detection value Vbatt at that time is set to the previous Dcent.
(= Go · Vbase / Vbatt)
G · ΔI) feedback control of the integral type control is executed, and the duty output center value Dcent is successively determined.

The CPU 54 sets the duty output center value Dcent
Each time is determined, dither control processing (FIG. 14) is executed by interruption processing eight times in 10 milliseconds. Tilt lever 8
During the operation, the CPU 54 firstly sets the target current value Iaim, the detected battery voltage value Vbatt, and the duty output center value Dcent.
Is read (S710) and the counter processing (S730-S
750), the dither amplitude value Ddizz = D “cn” using the dither amplitude reference value D [cnt] corresponding to the count value cnt determined by 750).
t] · Vbase / Vbatt is calculated (S760).

At this time, in both the transient region and the steady region of the current, the ratio (Vbase / Vbatt) is a value expressing the effect of the battery voltage VB which is a main disturbance factor. Upper limit of dither amplitude value Ddizz like form
No processing is performed to limit the range to the lower limit. The duty output value Dout = Dcent + Ddizz is calculated using the dither amplitude value Ddizz thus determined (S770).

The duty output value Dout (%) corrected to a value within the range of 0 to 100% as required is P
The data is written to the WM port 59 (S780 to S82).
0). Thus, the duty value (%) from the PWM port 59 becomes 1 around the duty output center value Dcent (%).
A PWM signal having a small amplitude at 00 Hz is output. The ON time of the transistor 61 is controlled according to the duty value (%) of the PWM signal, and the current flows through the solenoid 25a with a small amplitude of 100 Hz.

Therefore, no matter how much the battery voltage VB deviates from the reference voltage Vbase at that time, the current always oscillates at an almost constant amplitude Idizz required for dither control, while the reference state (battery voltage VB = Vbase and At the time of the solenoid resistance Rsol = Rbase), it rises so as to take almost the same history as when the reference gain Go is adopted.

Therefore, the spool of the solenoid valve 25 constantly vibrates with a constant amplitude except when the valve is closed. Accordingly, when the amplitude of the spool of the solenoid valve 25 becomes too small and the responsiveness of the solenoid valve 25 decreases, or when the amplitude of the spool of the solenoid valve 25 is too large to be opened, the solenoid valve 25 may be mistakenly opened. The occurrence of the problem of opening the valve even slightly is reliably prevented. Accordingly, the responsiveness of the spool of the solenoid valve 25 is always good, and the responsiveness of the mast 4 at the start of the operation of the tilt lever 8 is always good, and the mast 4 is caused by an excessive amplitude of the spool of the solenoid valve 25. In addition, no slight rattling occurs during tilting.

Further, since the rising history of the current is almost the same as when the reference gain Go is employed when the current is always in the reference state, the overshoot of the current causes the mast 4 to move when the tilt lever 8 is operated. There is no shock to occur and there is no fear of collapse. Also, assume that the solenoid resistance is at the resistance value at normal temperature,
Dither amplitude value Ddizz without considering variation of solenoid resistance
However, if the fluctuation of the solenoid resistance is small compared to the fluctuation of the battery voltage VB, the spool of the solenoid valve 25 can always be minutely vibrated with a required amplitude with almost no problem. Even if the disturbance factor due to the change in the solenoid resistance is not taken into account, the current according to the target current value Iaim flows through the solenoid 25a by the feedback control by the CPU 54, so that the mast 4 is always driven regardless of the change in the solenoid resistance. Tilt at a constant speed as set. For this reason, even when the mast 4 is tilted up and down, the tilting speed is then limited as set, and in this case, there is no fear of collapse of the load.

Further, when the battery voltage detection value Vbatt takes an excessively large or small value, the gain G is set to the upper limit value (= 2V
base) and the lower limit (= Vbase / 2). Therefore, for example, even if the battery voltage detection value Vbatt is detected to be excessively large or small due to a detection abnormality or the like,
A situation in which, for example, the rising slope of the current is abnormally large or small is avoided.

According to the embodiment described above, the following effects can be obtained. (1) Since the dither amplitude value Ddizz is also determined in consideration of the battery voltage detection value Vbatt, the spool of the solenoid valve 25 is always slightly vibrated at a required substantially constant amplitude regardless of the battery voltage at that time. Can be. Therefore, it is possible to reliably prevent the responsiveness of the solenoid valve 25 from deteriorating due to an excessively small amplitude of the spool and to prevent the solenoid valve 25 from being slightly opened when it should be closed due to an excessively large amplitude of the spool. Therefore, the amplitude of the spool of the solenoid valve 25 is too small to deteriorate the responsiveness of the mast 4 at the time of starting, the minute vibration at the time of tilting of the mast 4 due to the too large amplitude of the spool, When the valve 25 is to be closed, the valve is opened very slightly, and problems such as the microscopic displacement of the mast 4 can be reliably prevented.

(2) Since the ratio Vbase / Vbatt is a value expressing the effect of the battery voltage always regarded as a disturbance factor irrespective of the transient region and the steady region of the current, the dither amplitude value D
In the first embodiment in which dizz is limited to the range between the upper limit and the lower limit, the processing required in the first embodiment can be omitted, and the amplitude accuracy of the spool in the transient region of the current can be increased.

(3) Since the data of the battery voltage detection value Vbatt for determining the current value in the feedback control is used to determine the dither amplitude value Ddizz, the data for determining only the dither amplitude value Ddizz is used. No acquisition process is required.

(4) Since the gain G is determined by correcting the reference gain Go in consideration of the battery voltage detection value Vbatt, the solenoid current is always set at the set rising rate regardless of the fluctuation of the battery voltage VB. Can be launched. Accordingly, there is no fear of collapse of the load which may be caused by a shock when the mast 4 starts to move due to overshoot in a current transient region, and further, the responsiveness of the mast 4 is deteriorated due to a low battery voltage. Not even.

(5) Although the solenoid resistance, which is one of the disturbance factors, is not taken into account, the feedback control is performed in consideration of the disturbance factor due to the fluctuation of the solenoid resistance.
A current of the target current value Iaim can be passed through the solenoid 25a. Therefore, for example, the rearward tilting speed of the mast 4 at the time of high-elevation rearward tilt is reliably limited as set, and the shock at the end stop of the mast 4 at the time of high-elevation rearward tilt can be suppressed to a small degree. It can almost certainly be prevented.

(6) When the battery voltage detection value Vbatt is detected to be too large or too small, the gain G is limited to the upper limit value or the lower limit value. It is possible to prevent an abnormal current from flowing.

In addition, similarly to the first embodiment, the effect that a relatively expensive regulator is not required, the effect of improving the responsiveness of feedback control by adopting filter processing, the CPU 5
4, the hardware part required for feedback control by adopting software feedback control can be simplified.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS. This embodiment is an example applied to feedforward control using a battery voltage detection value Vbatt. Only the program data of the current value control process is different from that of the second embodiment, and the other data including the program data of the dither control process is the same as that of the second embodiment. Also, the configuration of the device is the same as that of the first embodiment except that a part of the circuit is omitted because current detection is unnecessary. For this reason, hereinafter, the same reference numerals are used for the common parts, and the description thereof is omitted.

As shown in FIG. 17, since the current detection is unnecessary because of the feedforward control, the current detection circuit 52 and the low-pass filter 53 are omitted from the controller 40 of the second embodiment. That is, the second end of the solenoid 25a whose first end is connected to the emitter of the transistor 60 built in the solenoid drive circuit 51 is grounded. The CPU 54 detects a battery voltage detection value Vba from a voltage signal input from the A / D port 64 via a resistor Rb as a measuring means and a disturbance factor measuring means.
get tt. The CPU 54 controls the ON time of the transistor 61 by using the data D necessary to determine the duty value (%) of the PWM signal output from the PWM port 59.
Cent and Dout are determined based on the program data of the current value control processing (FIG. 16) and the dither control processing (FIG. 14) stored in the ROM 55.

The program data of the current control process will be described with reference to FIG. Step 910 is a data reading process for reading necessary data. Target current value Iai
m and the battery voltage detection value Vbatt are read.

Step 920 is a process for calculating the duty output center value Dcent. Formula Dcent = (Iaim · Rb
ase / Vbatt) × 100. here,
Rbase is a reference resistance value (in this embodiment, a solenoid resistance value at normal temperature) and is a constant. Target current value Iaim
In this case, the duty value (%) may be determined so that an average voltage equal to Iaim · Rbase can be applied. Therefore, the duty output center value Dcent is expressed by the above equation using the battery voltage detection value Vbatt. It is. If the Dcent value calculated by the above equation is not in the range of 0 to 100%, the Dcent corrected so that the lower limit is 0% and the upper limit is 100% is adopted. In this embodiment, the voltage Iaim · Rbase in the above equation corresponds to the reference data.

The control of the current value of the solenoid valve 25 by the controller 40 is performed as follows in accordance with the flowcharts of FIGS. In the current value control process executed every 10 milliseconds, first, the target current value Iaim and the battery voltage detection value Vbatt are read (S910), and the duty output center value Dcent = (Iaim · Rbase / Vbatt) × 100 is calculated (S920). ).

In the dither control process executed eight times / 10 ms, the duty output value Dout (= Dcent + D) determined using the duty output center value Dcent is used.
[Cnt] · Vbase / Vbatt) is written to the PWM port 59. As a result, the current always flowing through the solenoid 25a is adjusted so as to flow almost in accordance with the target current value Iaim while oscillating at an almost constant amplitude Idizz required for dither control regardless of the fluctuation of the battery voltage.

Further, since the circuits 52 and 53 for current detection are not required, the configuration of the hardware can be further simplified as compared with the above embodiments. In addition, since a correction process for feedback control is not required, the load on the CPU 54 can be reduced as compared with the above embodiments. Also, since the data of the battery voltage detection value Vbatt used to determine the duty output center value Dcent for feedforward control is used to determine the dither amplitude value Ddizz, only the dither amplitude value Ddizz is determined. No data acquisition processing is required. In addition, the effect of eliminating the need for the regulator described in each of the above embodiments can be similarly obtained.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIGS. This embodiment is a modification of the first embodiment. In the first embodiment, the duty output center value Dcent is used as data for determining the dither amplitude value Ddizz, but in this embodiment, the current detection value Idet is used. Only some data such as program data of the dither control process is different from the first embodiment, and other data including the program data of the current value control process is the same as the first embodiment.
The configuration of the device is the same as that of the first embodiment. Therefore, only the different parts will be described below.

The ROM 55 stores the program data of the current value control process shown in FIG. 1 and the program data of the dither control process shown in FIGS. 19 and 20. FIG. 18 is a graph showing a relationship between the current detection value Idet and the duty output center value Dcent. The reference line M in the graph indicates a reference state (battery voltage VB = Vbase and solenoid resistance Rsol
= Rbase), when a PWM signal having a duty value that is centered around the duty output center value Dcent is instructed, the current detection value Ide that should be detected by the CPU 54
It is a line in which t (hereinafter referred to as a current reference detection value Ibase) is plotted.

The line on which the current detection value Idet that should be obtained with respect to the duty output center value Dcent is plotted is
As the battery voltage decreases and the solenoid resistance increases, the slope shifts from the reference line M to a greater direction as indicated by the X-ray in the same figure, and as the battery voltage increases and the solenoid resistance decreases, the Y line in the same figure decreases. As shown in FIG. For example, if the reference state is Dcent = Dz, Idet = Iz should be obtained, but if it is shifted like an X-ray according to the disturbance factor at that time, Idet = Iz
If det = Ix and shift like Y line, Idet = Iy is obtained. That is, the current detection value Idet depends on the disturbance factor.
Shifts with respect to the current reference detection value Ibase, and the ratio (Ibase
/ Idet) is a value reflecting the disturbance factor. Using this, the dither amplitude value Ddizz = D [cnt] · Ibase / Id
The dither amplitude value D [cnt] is multiplied by the ratio (Ibase / Idet) to correct the dither amplitude reference value D [cnt] as in the equation of et to obtain the dither amplitude value Ddizz in which the disturbance factor is considered. 19 and program data of the dither control processing shown in FIG.

Hereinafter, the program data of the dither control processing will be described with reference to FIGS. 19 and 20. Step 1010 is a data reading process for reading necessary data. The target current value Iaim, the current detection value Idet, and the current and previous duty output center values Dcent are read.

Step 1020 is a process for calculating the current reference detection value Ibase from the previous duty output center value Dcent. Here, the current reference detection value Ibase is the same as the previous D
When the duty value (%) of the PWM signal is determined based on the cent, the current detection value that should be detected under the assumption that the PWM signal is in the reference state (battery voltage VB = Vbase and solenoid resistance Rsol = Rbase) This is a value corresponding to Idet. The current reference detection value Ibase is given by the formula Ibase = h · Dcent
Is calculated by “H” is a conversion coefficient for converting Dcent into Ibase, and is a value corresponding to the slope of the reference line M in FIG.

Steps 1030 to 1060 are:
This is processing corresponding to S230 to S260 in the first embodiment. Steps 1070 to 1110 are processing for determining the dither amplitude value Ddizz. Steps 1070 and 1080 are processing for keeping the dither amplitude value Ddizz at or above the lower limit, and steps 1090 and 1100.
Is a process for keeping the dither amplitude value Ddizz below the upper limit.

Step 1070 is a process for determining whether or not the current detection value Idet exceeds twice the current reference detection value Ibase. If the condition Idet> 2Ibase is satisfied, the dither amplitude value Ddizz is set to the lower limit value in step 1080. "D
[Cnt] / 2 ". Also, step 1090 includes:
In the process of determining whether or not the current detection value Idet is less than 1/2 of the current reference detection value Ibase, the condition Idet <Ibas
If e / 2 is satisfied, the dither amplitude value Ddizz is determined to be the upper limit value “2D [cnt]” in step 1100.

Step 1110 is a process for calculating the dither amplitude value Ddizz when the current detection value Idet satisfies Ibase / 2 ≦ Idet ≦ 2Ibase. Dither amplitude value Ddi
zz is obtained by multiplying the dither amplitude reference value D [cnt] by the ratio “Ibase / Idet” between the current detection value Idet and the current reference detection value, and is calculated by the equation Ddizz = D [cnt] · Ibase / Idet. .

At step 1120, the duty output value D
This is the process of calculating out. The duty output value Dout is
It is obtained by adding the dither amplitude value Ddizz to the duty output center value Dcent (Dout = Dcent + Ddizz).

Steps 1130 to 1160 are:
This is a process for keeping the calculated duty output value Dout within the range of 0 to 100%.
This is processing corresponding to the processing of 780 to S810. In the process of step 1140, the target current value Iaim is "0 amperes".
In this case, the duty output value Dout = 0 (%) is also set. Step 1170 is a process of writing the duty output value Dout to the PWM port 59.

Next, the operation of the tilt control device will be described. The target current value Iaim is determined according to a tilt mode determined based on input signals from the sensors 41 to 46, and the current detection value Idet is obtained by a filtering process executed by the CPU 54. The CPU 54 executes the current value control process shown in FIG. 1 every 10 milliseconds, for example, and determines the duty output center value Dcent.

The CPU 54 calculates the duty output center value Dcent.
Each time is determined, the dither control process shown in FIG. 19 is executed by an interrupt process at a rate of 8/10 ms. First, necessary data Iaim, Idet, and the current and previous Dcent are read. After the start of the operation of the tilt lever 8, the target current value Iaim is 0.
It becomes a value other than.

The CPU 54 calculates the current reference detection value Ibase = h · Dcent using the previous Dcent. The dither amplitude value Ddizz is determined using the dither amplitude reference value D [cnt] corresponding to the count value cnt determined in the counter processing (S1040 to S1060). That is, at this time, the current detection value I
Det is considered, and when Idet> 2Ibase, Ddizz = D
[Cnt] / 2, and when Idet <Ibase / 2, Ddi
It is determined that zz = 2D [cnt] / 2. When the Idet value does not satisfy these two conditions, that is, Ibase / 2 ≦ Idet ≦ 2
When Ibase is satisfied, Ddizz = D “cnt] · Ibase /
Idet is calculated (S1070 to S1110).

The duty output value Dout = Dcent + Ddizz is calculated using the dither amplitude value Ddizz thus determined (S1120). And 0-100 if necessary
Duty output value Dout corrected to a value within the range of%
(%) Is written to the PWM port 59 (S1130)
To S1170).

In this way, a PWM signal is output from the PWM port 59 so that the duty value (%) slightly swings at 100 Hz around the duty output center value Dcent (%), and the current is minutely swinged at 100 Hz to the solenoid 25a. Will flow.

The ratio (Ibase / Ide) used in this embodiment
Since t) takes a value that accurately expresses a disturbance factor on the basis of the actually measured current, the amplitude accuracy of the spool can be improved. Also, the data Idet used in the feedback control to determine the dither amplitude value Ddizz, the previous Dcen
Since t is used, there is no need to perform a data acquisition process only for determining the dither amplitude value Ddizz. Other, first
The effects (1) and (4) to (6) described in the effects of the embodiment can be similarly obtained.

(Fifth Embodiment) In the second and third embodiments, the battery voltage is measured as a main disturbance factor, and only the battery voltage is reflected in the determination of the Dcent value and the Ddizz value. Reflects the solenoid resistance, which is one of the main factors of the disturbance factor, in the determination of the Dcent value and the Ddizz value. The CPU 54 calculates the solenoid resistance using the data used in the feedback control and the feedforward control. Therefore, in this embodiment, the CPU
54 constitutes a disturbance factor measuring means.

The solenoid resistance value Rsol is calculated by the following equation using the previous battery voltage detection value Vbatt, current detection value Idet, and duty output center value Dcent. Rsol = (Dcent / 10
0) Calculated by Vbatt / Idet. This solenoid resistance value Rsol is considered when determining the current duty output center value Dcent in the same manner as the battery voltage detection value Vbatt. That is, when both the battery voltage detection value Vbatt and the solenoid resistance value Rsol are considered as disturbance factors, the correction coefficient α is α = (Vbase / Vbatt) · (Rsol / Rb
ase) = β · (Rsol / Vbatt). Where V
base is a reference voltage, Rbase is a reference resistance value, β is β =
Vbase / Rbase is a constant.

When considering the solenoid resistance in the second embodiment, first, the solenoid resistance value Rsol = (Dcent / 10
0) .Vbatt / Idet is calculated, and the gain G may be calculated in the current value control process by the equation G = Go · β · (Rsol / Vbatt). Also, the dither amplitude value D
dizz is calculated by the formula Ddizz = D [cnt] · β · (Rsol / Vbatt)
Is calculated by

When the solenoid resistance is also considered in the third embodiment, first, the solenoid resistance Rsol = (Dcent
/ 100) · Vbatt / Idet, and calculates the duty output center value Dcent in the current value control processing by the formula Dcent = Ddef ·
What is necessary is just to calculate by (beta) * (Rsol / Vbatt). In the dither control processing, the dither amplitude value Ddizz is calculated by the equation Ddizz.
= D [cnt] · β · (Rsol / Vbatt)

According to these configurations, it is possible to cope with two main disturbance factors, that is, the battery voltage and the fluctuation of the solenoid resistance, to ensure the stability in the transient region of the current, and to reduce the noise caused by the overshoot of the current. Can be further reduced, and the responsiveness of the mast 4 can be prevented from deteriorating due to a delay in rising of the current which can occur due to an increase in the solenoid resistance value due to an increase in the solenoid temperature.

The dither amplitude value Ddi of the dither control processing
When determining zz, the dither amplitude value Ddizz (= D [cnt] · β · (Rsol / Vbatt)) is determined in consideration of disturbance factors of both the battery voltage detection value Vbatt and the solenoid resistance value Rsol. A change in the amplitude of the spool of the solenoid valve 25, which may occur due to an increase in the solenoid resistance value due to a rise in the solenoid temperature, can be prevented, and the spool of the solenoid valve 25 can be more minutely vibrated with the required amplitude.

In particular, since the solenoid resistance is a disturbance factor that changes during key-on, the mast 4 can be operated stably and responsively during key-on by taking into account the fluctuation of the solenoid resistance.

The present invention is not limited to the above embodiments, and may be implemented as follows, for example. (N) The data used to obtain the dither amplitude value may be any data as long as it reflects the influence of the disturbance factor. For example, a converted value Icent obtained by converting the duty output center value Dcent into a current value under the assumption of a reference state
By multiplying the ratio (Icent / Iaim) with the target current value Iaim by the dither amplitude reference value D [cnt], the dither amplitude value Ddizz can be calculated by the formula Ddizz = D [cnt] · (Icent / Iaim). it can. In the fourth embodiment, a converted value Ddet obtained by converting the current detection value Idet into a duty value under the assumption of a reference state, and a duty output center value Dcent
And the ratio (Dcent / Ddet) to the dither amplitude reference value D [cnt]
And the dither amplitude value Ddizz is calculated by the formula Ddizz = D [cn
t] · Dcent / Ddet. Further, data other than the data used to determine the current command value can be adopted. For example, in the first and fourth embodiments, a device configuration capable of measuring the battery voltage detection value Vbatt and the solenoid resistance Rsol is used, and the dither amplitude is set. Value Ddiz
Vbatt or Rsol data may be used to determine z.

(M) In the second and third embodiments,
A disturbance factor other than the battery voltage and the solenoid resistance value may be measured, and the duty output center value Dcent as a current command value may be corrected according to the measured value.

(K) In the second and third embodiments,
The disturbance factor may be measured indirectly instead of directly. For example, a method of measuring the oil temperature around the solenoid using a detector such as a temperature sensor and indirectly measuring the solenoid resistance value from the solenoid temperature estimated from the detected temperature can be adopted.

(G) The number of interruptions of the dither control process for one current value control process can be set as appropriate. For example, two interrupts may be performed only to instruct the maximum value (Dmax) and the minimum value (-Dmax) of the dither amplitude. Further, the dither control may be a process of instructing a waveform of two or more cycles per current value control process.

(F) The method of controlling the current value by the CPU 54 is not limited to the PWM control. Any configuration that can control the current flowing through the solenoid based on the output signal from the CPU may be used.

(H) The number of times the detection signal S2 is sampled is not limited to an even number in one cycle. Sampling is performed a total of even number of times so that sampling is performed twice or more per cycle in a fixed time obtained by multiplying the cycle of dither control (for example, 100 Hz) by a natural number, and an average of the even number of sampling values is used as a current detection value It can also be calculated. For example, sampling may be performed six times per two cycles, and the average of the six values may be used as the current detection value.

(P) The cut-off frequency of the low-pass filter 53 is set so as to remove ripples of 100 Hz, and the current detection value Idet of a constant voltage is supplied from the A / D port 62.
May be input. There is no particular problem when employing control in which the delay time of a signal passing through a low-pass filter is within an allowable range. In this configuration, C
Filter processing by the PU 54 is eliminated, and the burden on the CPU 54 can be reduced.

(R) The method of controlling the current value by the CPU 54 is not limited to the PWM control. Any configuration that can control the current flowing through the solenoid based on the output signal from the CPU may be used.

(Q) The feedback control is not limited to the integral control in which the previous Dcent value is corrected by the correction amount proportional to the difference ΔI. It is also possible to adopt a control method in which a current command value converted from the target current value Iaim is initially commanded, and correction is performed, for example, by a fixed amount so as to reduce the difference ΔI.

(U) The solenoid valve 25 is not limited to the pilot control type, but may be a direct acting type, for example. (S) In each of the embodiments, the solenoid valve is provided in series with the manual switching valve that is switched by lever operation.
Instead of such a manual switching valve, in a forklift equipped with an electromagnetic switching valve which is controlled by a controller upon detecting the operation of a cargo handling lever (for example, JP-A-7-61792), an electromagnetic switching valve or another electromagnetic valve is used. (For example, a solenoid valve for adjusting the speed in Japanese Patent Application Laid-Open No. 7-61792) may be implemented in the current value control.

(T) The control may be carried out in controlling the current value of a solenoid valve provided in the oil passage of the lift cylinder. Of course, the present invention may be implemented in controlling the current value of a solenoid valve provided in an oil passage of another hydraulic cylinder such as a reach cylinder in a reach type forklift or a side cylinder that slides a fork in the vehicle width direction. Similarly, in these configurations, it can be expected that the responsiveness of the solenoid valve is ensured and that the adverse effect on the opening due to the excessive amplitude of the spool is prevented.

(V) Not limited to engine forklifts
It may be implemented in a battery forklift. (W) Industrial vehicles other than forklifts may be used. For example, the present invention can be implemented in current value control of a solenoid valve provided in an oil passage of a hydraulic cylinder in a power shovel or a high work vehicle. Here, the cargo handling equipment in the present invention is defined as a concept including a shovel and a work table for handling earth and sand, workers, and the like.

The technical ideas (inventions) other than the claimed invention, which are grasped from the above embodiments and modifications, will be described below together with their effects. (A) In the invention according to claim 5 or claim 6, the reference state of the disturbance factor is a state where at least a voltage of a power supply for supplying a current to the solenoid is at a reference voltage,
The disturbance factor measuring means includes a power supply voltage measuring means for measuring a voltage of the power supply as the disturbance factor. According to this configuration, an appropriate dither amplitude can be obtained both in the transient region and the steady region of the current even by the fluctuation of the power supply voltage.

(B) In the invention according to claim 5 or claim 6, the reference state of the disturbance factor is a state in which at least the resistance of the solenoid is equal to a reference resistance value, and the disturbance factor measuring means includes the solenoid. Resistance value measuring means for measuring the resistance value as the disturbance factor. According to this configuration, an appropriate dither amplitude can be obtained in both the transient region and the steady region of the current regardless of the fluctuation of the solenoid resistance value.

(C) In the invention according to any one of claims 3 to 5, the control means may control the current command value with a correction amount proportional to a difference between the current detection value and the target current value. The proportional constant for determining the correction amount is a gain determined from the transfer function of the integral control in consideration of the stability of the control system. According to this configuration, stable current value control can be realized.

(D) In (c), the control means corrects the gain by using data obtained from the measurement value of the measurement means. According to this configuration, the transient characteristics of the current can be stabilized.

(E) In the invention according to any one of claims 1 to 10, the detection signal inputted by the control means from the current detection means is a signal having a predetermined period of amplitude, and Detection value calculation means for calculating the amplitude center of the current as the current detection value. According to this configuration, the amplitude center value of the detection signal can be obtained by a simple process.

(F) In the invention according to any one of claims 1 to 12, since the solenoid valve drives the cargo handling equipment independently of the operation of the operation unit, the solenoid valve is disposed on the oil passage of the hydraulic cylinder. It is provided in series with a manual switching valve that is switched according to the operation of the operation unit. According to this configuration,
The stable operation of the cargo handling equipment can be ensured, and even if the manual switching valve sticks (sticks), the sticking can be eliminated depending on the level of the force for operating the operation unit, and the occurrence of problems due to the sticking of the valve can be reduced. In each of the above embodiments, the tilt lever 8 constitutes an operation unit, and the tilt manual switching valve 19 constitutes a manual switching valve.

(G) In the invention according to any one of the first to twelfth aspects, the control means is provided on the vehicle to obtain a detection value necessary for controlling the operation of the cargo handling equipment. The target current value to be used in the correction process is determined according to the detection value from the detection means. According to this configuration, the operation of the cargo handling equipment can be stably controlled when the target current value is determined according to the detected value necessary for controlling the operation of the cargo handling equipment and the drive control of the cargo handling equipment is performed. In each of the above embodiments, the elevation sensor 41, the tilt angle sensor 42, the pressure sensor 43, the forward tilt switch 44, the backward tilt switch 45, and the operation switch 46 constitute a detecting unit.

(H) In the invention according to any one of the first to twelfth aspects, the current command value commanded by the control means is determined by turning on a switching means provided between a power supply and the solenoid. This is for determining the duty value of the PWM signal for controlling the time. According to this configuration, current value control of the solenoid valve by duty control can be realized.

(I) In the invention according to any one of the first to twelfth aspects, the hydraulic cylinder is for tilting a mast that supports the cargo handling equipment so as to be able to move up and down. According to this configuration, the tilting operation of the mast is stabilized.

[0187]

As described in detail above, claims 1 and 2 have been described.
According to the invention described in claim 12, the data obtained by using the measured value of the measuring means used in determining the current command value for controlling the current flowing through the solenoid of the solenoid valve to be the target current value is obtained. Since the dither amplitude value is used to determine the dither amplitude value, the current can be made to oscillate at a desired current amplitude by dither control irrespective of disturbance factors that affect the current, such as fluctuations in the power supply voltage and the solenoid resistance. Therefore, since the spool of the solenoid valve can always be minutely vibrated at a desired amplitude, the fluctuation of the spool amplitude such as a decrease in the responsiveness of the solenoid valve due to an excessively small amplitude of the spool and an adverse effect on the opening due to the excessive amplitude of the spool. Can be prevented. As a result, the effect of the dither control can be sufficiently exerted, the responsiveness of the cargo handling equipment can be maintained well, and the stability of the operation of the cargo handling equipment can be maintained.

According to the third and twelfth aspects of the present invention, the dither amplitude value is determined using the data obtained using the measured values used in the feedback control. Can be used for

According to the fourth and twelfth aspects of the present invention, the detected current value used in the feedback control can be used for dither control, and at least when the current is in a steady state, the spool is always driven with a desired amplitude. Micro vibration can be performed.

According to the fifth and twelfth aspects of the invention, the measured value of the disturbance factor used in the feedback control can be used for dither control, and when the current is in either the transient region or the steady region. Also, the micro-vibration of the spool can always be performed at a desired amplitude.

According to the sixth and twelfth aspects of the present invention, the measured value of the disturbance factor used in the feedforward control can be used for dither control, and the current is in either the transient region or the steady region. In some cases, the spool can always be minutely vibrated at a desired amplitude.

According to the seventh and twelfth aspects of the present invention, when determining the dither amplitude value, the data obtained by using the measured value of the measuring means and the assumption that the disturbance factor is in the reference state are used. Since the dither amplitude reference value set to obtain the desired current amplitude under the assumption that the disturbance factor is in the reference state is corrected in accordance with the ratio of the data determined by and the reference data of the same dimension, The dither amplitude value can be determined by a simple calculation.

According to the eighth and twelfth aspects of the present invention, when determining the dither amplitude value, the target current value and the current command value used in the feedback control under the assumption that a disturbance factor is in a reference state. The dither amplitude reference value set to obtain the desired current amplitude under the assumption that the disturbance factor is in the reference state is corrected according to the ratio of comparing the same current with the target current value. The dither amplitude value can be determined by a simple calculation using the current command value.

According to the ninth and twelfth aspects, the dither amplitude reference value is corrected in accordance with the ratio of the target current value and the current command value used in the feedback control of the integral control in the same dimension. When the dither amplitude value is not within the predetermined range, the dither amplitude value is limited to the upper limit value or the lower limit value of the range.
It is possible to prevent the spool from excessively oscillating in the transient region of the current.

According to the tenth and twelfth aspects of the present invention, when determining the dither amplitude value, the current command value and the current detection value used in the feedback control under the assumption that a disturbance factor is in a reference state. The dither amplitude reference value set to obtain the desired current amplitude under the assumption that the disturbance factor is in the reference state is corrected according to the ratio obtained by comparing the current command value with the current command value. The dither amplitude value can be determined by a simple calculation using the detected current value, and the spool can always be slightly vibrated at a desired amplitude regardless of whether the current is in the transient region or the steady region.

According to the eleventh and twelfth aspects of the present invention, sampling is performed at least twice per one cycle of the detection signal from the current detection means per natural period times a natural number times the cycle of the detection signal. In this case, sampling is performed an even number of times in total, and a current detection value is calculated by averaging the even number of sampling values. Therefore, a current detection value can be obtained almost in real time, and control response is not impaired.

[Brief description of the drawings]

FIG. 1 is a flowchart of a current value control process according to a first embodiment.

FIG. 2 is a flowchart of dither control processing.

FIG. 3 is a graph illustrating a dither amplitude reference value.

FIG. 4 is a graph showing a time change of a solenoid current.

FIG. 5 is a graph showing a relationship between a current value and a duty value.

FIG. 6 is an electric circuit diagram of a current value control device for the solenoid valve.

FIG. 7 is a signal waveform diagram for explaining a method of obtaining a detected current value of a solenoid.

FIG. 8 is an electric configuration block diagram of a tilt control device.

FIG. 9 is a graph showing a relationship between a tilt angle and a target current value.

FIG. 10 is a map diagram for obtaining a maximum allowable forward tilt angle from a lift and a load.

FIG. 11 is a side view of a forklift.

FIG. 12 is a hydraulic control circuit diagram of a forklift.

FIG. 13 is a flowchart of a current value control process according to the second embodiment.

FIG. 14 is a flowchart of dither control processing.

FIG. 15 is an electric circuit diagram of the current value control device for the solenoid valve.

FIG. 16 is a flowchart of a current value control process according to the third embodiment.

FIG. 17 is an electric circuit diagram of the current value control device for the solenoid valve.

FIG. 18 is a graph showing a relationship between a current detection value and a duty output center value in the fourth embodiment.

FIG. 19 is a flowchart of dither control processing.

FIG. 20 is also a flowchart.

FIG. 21 is a graph showing a time change of a solenoid current according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Forklift as an industrial vehicle, 2 ... Fork as cargo handling equipment, 4 ... Mast, 5 ... Tilt cylinder as hydraulic cylinder, 25 ... Solenoid valve, 25a ... Solenoid, 52 ... Electric current which comprises measuring means and current detecting means A detection circuit, 53... A low-pass filter constituting measurement means and current detection means, 54... Constituting a control means and dither control means, and a CPU as judgment means, amplitude value limiting means and detection value calculation means, 55. ROM as storage means and 5
8 ... Battery as power source, Iaim ... Target current value, Idet
... Current detection value, Dcent: Duty output center value as current command value, Dout: Duty output value as dither command value, Ddizz: Dither amplitude value, D [cnt]: Dither amplitude reference value, Idizz: Current amplitude, Rb ... resistance as measuring means and disturbance factor measuring means.

Claims (12)

[Claims] 1. An electromagnetic valve provided on an oil passage of a hydraulic cylinder for driving cargo handling equipment, storage means for storing a target current value to be passed to a solenoid of the solenoid valve, and a current flowing to the solenoid being a target current value. Measuring means for measuring a measurement value necessary to obtain data used for control for controlling the current, and a current command value for controlling a current flowing through the solenoid so that the current can be made closer to a target current value. Control means for executing a correction process for correcting using the data obtained from the measurement value of the measurement means based on the program data; andfor dither control for microvibrating the spool of the solenoid valve, the current command value The dither amplitude value for the added amplitude is
Dither control means for determining a dither command value obtained by adding the dither amplitude value to the current command value while determining using data obtained by using the measured value so as to obtain a desired current amplitude. Dither control device for solenoid valves in industrial vehicles. 2. The method according to claim 1, wherein each time the control unit executes the correction process once, the dither control unit takes one cycle of the waveform so as to take a value on the waveform that is amplitude at a predetermined cycle around the current command value. 2. The dither control device for an electromagnetic valve in an industrial vehicle according to claim 1, wherein a plurality of the dither instruction values are determined by an interruption process to issue the instruction. 3. A current detection means for detecting a current flowing through a solenoid of the solenoid valve, wherein the correction processing executed by the control means includes a current detection value determined from a detection signal of the current detection means and the target current. Feedback control for correcting the current command value so that a difference from the current value falls within an allowable range, wherein the dither control means uses the data obtained using the measurement value used in the feedback control to perform the dither control. 3. The dither control apparatus for an electromagnetic valve in an industrial vehicle according to claim 1, wherein the amplitude value is determined. 4. The measurement means is the current detection means, and the dither control means determines the dither amplitude value using data obtained by the control means using the current detection value used in feedback control. The dither control device for an electromagnetic valve in an industrial vehicle according to claim 3. 5. A disturbance factor measuring unit for measuring a disturbance factor affecting a current flowing through the solenoid, and the dither control unit measures the disturbance factor used in the feedback control by the control unit. The dither control device for an electromagnetic valve in an industrial vehicle according to claim 3, wherein the dither amplitude value is determined using data obtained using the values. 6. The measuring means is a disturbance factor measuring means for measuring a disturbance factor affecting a current flowing through the solenoid, and the correction processing executed by the control means uses a measured value of the disturbance factor measuring means. Feed-forward control for instructing a current command value determined from a target current value in consideration of a disturbance factor, wherein the dither control means uses the data obtained using the measured value of the disturbance factor measurement means to perform the dither control. 3. The dither control apparatus for an electromagnetic valve in an industrial vehicle according to claim 1, wherein the amplitude value is determined. 7. The dither control means sets a dither amplitude reference value in advance so as to obtain the desired current amplitude under the assumption that a disturbance factor affecting the current flowing through the solenoid is in a reference state. And data obtained using the measurements to determine the dither amplitude value;
The dither amplitude value is determined by correcting the dither amplitude reference value according to a ratio between the data determined under the assumption that the disturbance factor is in a reference state and reference data of the same dimension. A dither control device for an electromagnetic valve in an industrial vehicle according to claim 6. 8. The dither control means sets a dither amplitude reference value in advance so as to obtain the desired current amplitude under the assumption that a disturbance factor affecting the current flowing through the solenoid is in a reference state. The dither amplitude reference value is corrected by correcting the dither amplitude reference value according to a ratio obtained by comparing the target current value and the current command value in the same dimension under the assumption that the disturbance factor is in a reference state. The dither control device for an electromagnetic valve in an industrial vehicle according to any one of claims 3 to 5, wherein the value is determined. 9. The control means performs feedback control of integral control, and the dither control means determines whether or not the dither amplitude value obtained by correcting the dither amplitude reference value is within a predetermined range. Determining means for determining, and amplitude value limiting means for limiting the dither amplitude value to an upper limit or a lower limit of the predetermined range when the dither amplitude value is determined not to be within the predetermined range. Claim 8 comprising:
A dither control device for an electromagnetic valve in an industrial vehicle according to Claim 1. 10. The dither control means sets a dither amplitude reference value in advance so as to obtain the desired current amplitude under the assumption that a disturbance factor affecting the current flowing through the solenoid is in a reference state. The dither amplitude reference value is corrected by correcting the dither amplitude reference value according to a ratio in which the current command value and the current detection value are compared in the same dimension under the assumption that the disturbance factor is in a reference state. The dither control device for an electromagnetic valve in an industrial vehicle according to any one of claims 3 to 5, wherein the value is determined. 11. A detection signal input from said current detection means by said control means is a signal having a predetermined period of amplitude,
The control means performs a total of even number of samplings on the detection signal so as to be sampled twice or more per period in a certain period of a natural number times a predetermined period, and averages the even number of sampling values. 11. A detection value calculation means for calculating the current detection value.
The dither control device for an electromagnetic valve in an industrial vehicle according to any one of the preceding claims. 12. An industrial vehicle comprising the electromagnetic valve dither control device according to claim 1. Description: