JP2024072831A - Forklift mast height measurement device and operation diagnostic device - Google Patents

Abstract

[Problem] To provide a mast height measuring device 4 for a forklift that is inexpensive and simple in structure yet can accurately measure the mast height. [Solution] Correlation data showing the correlation between the discharge pressure and rotation speed of a hydraulic pump 26 that supplies hydraulic fluid to a lift cylinder 14, the stroke amount of a control valve 21 that controls the flow of hydraulic fluid in and out of the lift cylinder 14, and the flow rate of the hydraulic fluid flowing in and out of the lift cylinder 14 is recorded, and measurement data of the discharge pressure of the hydraulic pump 26, measurement data of the rotation speed of the hydraulic pump 26, and stroke measurement data of the control valve 21 are acquired, and the flow rate of the hydraulic fluid flowing in and out of the lift cylinder 14 is calculated from the values of the discharge pressure measurement data, rotation speed measurement data, and stroke measurement data by referring to the correlation data, and the mast height is calculated based on the flow rate of the hydraulic fluid. [Selected Figure] Figure 6

Description

The present invention relates to a mast height measuring device that measures the mast height of a forklift.

Conventionally, the following methods have been considered for measuring the height of a forklift mast.
(1) The stroke amount of the lift cylinder is measured using a stroke sensor.
(2) Measure the supply flow rate to the cylinder using a flow meter.
(3) Install a switch that turns ON/OFF when the mast reaches a specified height and measure the height.

However, in the method (1), it is necessary to sense a wide area of several meters, which makes it difficult to install the sensor, and the sensor may be expensive.
Method (2) also requires the installation of a new flow meter between the hydraulic circuits of the forklift, which is difficult in terms of space and requires an expensive sensor.
Method (3) alleviates problems in terms of installation and cost, but has the problem that it can only measure the height of the point where the switch is installed, and the height of the mast cannot be determined at intermediate points.

Japanese Patent Application Laid-Open No. 9-148941

On the other hand, as described in Patent Document 1, a method has been proposed for measuring mast height using equipment that is originally installed on the forklift, without using a dedicated sensor. In Patent Document 1, based on the principle that the rotation speed of the hydraulic pump motor that drives the mast to rise and fall is proportional to the oil flow rate that flows in and out of the mast cylinder, and thus the lifting distance of the mast per unit time (i.e., the lifting speed), a calculation is performed on the output value of the tachometer of the hydraulic pump motor that is originally installed to calculate the mast height.

However, the amount of oil flowing in and out of the mast cylinder varies depending on factors such as the load of the cargo and the amount of lift lever operation, so the mast height calculated using this method is extremely inaccurate and not suitable for practical use.

The present invention was first completed after identifying this problem, and its main objective is to provide a forklift mast height measuring device that is inexpensive and simple in construction yet can accurately measure mast height.

In other words, the forklift mast height measuring device of the present invention is characterized by having the following components:

(1) A correlation data storage unit that stores correlation data showing the correlation between the discharge pressure of a hydraulic pump that supplies working fluid to the lift cylinder, the rotation speed of the hydraulic pump, and the stroke amount of a control valve that controls the flow of working fluid in and out of the lift cylinder, and the flow rate of working fluid flowing in and out of the lift cylinder.

(2) A calculation unit that acquires discharge pressure measurement data having a value related to the discharge pressure of the hydraulic pump, rotation speed measurement data having a value related to the rotation speed of the hydraulic pump, and stroke measurement data having a value related to the stroke amount of the control valve, and calculates the flow rate of the working fluid flowing in and out of the lift cylinder from each of the values of the discharge pressure measurement data, rotation speed measurement data, and stroke measurement data by referring to the correlation data, and calculates the mast height based on the flow rate of the working fluid.

The above configuration not only makes it possible to measure mast height using existing sensors or inexpensive, easy-to-install sensors, but also makes it possible to calculate the flow rate of the working fluid flowing in and out of the lift cylinder using correlation data that takes into account the unique characteristics of the hydraulic pump and control valve installed in the actual machine, allowing for accurate measurement of mast height.

1 is an overall schematic diagram of a forklift according to an embodiment of the present invention; 2 is an overall schematic diagram showing a circuit diagram of a hydraulic mechanism of the forklift and a mast height measuring device in the embodiment; FIG. FIG. 4 is a circuit diagram showing the movement of the control valve when the lift lever is operated to the lift side in the embodiment. FIG. 4 is a circuit diagram showing the movement of the control valve when the lift lever is operated to the lowering side in the embodiment. FIG. 2 is a functional block diagram of the mast height measuring device of the embodiment. 4 is a flowchart showing a mast height measurement procedure using the mast height measurement device of the embodiment. 5 is a flowchart showing a procedure for calculating a mast raising and lowering distance (mast moving distance) by the mast height measuring device of the embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
<Configuration>

As shown in Fig. 1, the forklift 1 according to this embodiment is equipped with a vehicle body 11 equipped with tires and capable of running, a platform (forks) 12 on which cargo is carried, and a mast 13 that supports the platform 12 so that it can be raised and lowered. In the figure, reference numeral 14 denotes a lift cylinder that extends and retracts the mast 13 to drive the platform 12 to rise and lower, reference numeral 15 denotes a tilt cylinder that tilts the mast, reference numeral 16 denotes a lift lever for operating the lift cylinder, and reference numeral 17 denotes a tilt lever for operating the tilt cylinder.

The forklift 1 also includes a hydraulic mechanism 2 for driving the lift cylinder 14 and tilt cylinder 15, and a mast height measuring device 4 for acquiring status data indicating the status of the hydraulic mechanism 2 and calculating the height of the mast 13 from the acquired data.

The hydraulic mechanism 2, as shown in the circuit diagram in FIG. 2, guides the working fluid (here, the working fluid is oil) discharged from the hydraulic pump 26 to the lift cylinder 14 and tilt cylinder 15 to operate them. Note that the following will refer specifically to the structure related to the lift cylinder 14.

In FIG. 2, the reference symbol indicates a control valve 21 that is linked to the operation of the lift lever 16, and in this case, it is a directional flow control type that has both directional switching and flow control functions.

When the lift lever 16 is operated to the stop position, as shown in Figure 2, the spool of this control valve 21 is in the stop position, all hydraulic oil discharged from the hydraulic pump 26 returns to the tank 22, and the flow of hydraulic fluid into and out of the lift cylinder 14 is prohibited, and the mast 13 is stopped.

When the lift lever 16 is operated in the upward direction, as shown in Figure 3, the spool of the control valve 21 moves in the upward direction according to the amount of operation, and hydraulic oil discharged from the hydraulic pump 26 flows into the lift cylinder 14 through the pilot valve 24, lifting the mast 13. When the mast 13 reaches the top, hydraulic oil can no longer flow into the lift cylinder 14 and returns to the tank 22 through the relief valve 28.

When the lift lever 16 is operated in the downward direction, as shown in Figure 4, the hydraulic pump 26 stops and the spool of the control valve 21 moves downward according to the amount of operation of the lift lever 16, and the hydraulic oil in the pump 26 and lift cylinder 14 returns to the tank 22 through the flow control valve 23, and the mast 13 descends. At this time, the pilot valve 24 between the lift cylinder 14 and the tank 22 is maintained open by the hydraulic oil passing through its orifice as the state of the pilot switching valve 25 switches, creating a pressure difference.

The hydraulic mechanism 2 is also provided with a number of sensors. Here, there are a rotation speed sensor 31 that measures the rotation speed of the electric motor 27 or the hydraulic pump 26, a discharge pressure sensor 32 that measures the discharge pressure of the hydraulic pump 26, a stroke sensor 33 that detects the stroke amount of the spool of the control valve 21, and a cylinder pressure sensor 34 that measures the pressure inside the lift cylinder 14.

The rotational speed sensor 31 may be, for example, an electromagnetic pickup type or a rotary encoder. The discharge pressure sensor 32 and the cylinder pressure sensor 34 may be, for example, pressure sensors such as strain gauge type or capacitance type. The stroke sensor 33 may be, for example, a magnetostrictive type or a Hall effect type.

The mast height measuring device 2 physically comprises a CPU, memory, I/O ports, A/D converter, etc., and functionally, as shown in Figure 5, the CPU and its peripheral devices work together in accordance with a program pre-stored in the memory, thereby fulfilling functions as a correlation data storage unit, calculation unit, etc.
Each part will be described in detail.

The correlation data storage unit holds and stores master data, which is multiple (here, three) pieces of correlation data that have been previously calculated and created through experiments, simulations, theoretical calculations, etc.

The first master data is in the form of a table that shows the correlation between the discharge pressure and rotation speed of the hydraulic pump 26 and the discharge flow rate, and is unique to the type of hydraulic pump 26.

The second master data is in the form of a table that shows the correlation between the discharge pressure of the hydraulic pump 26 and the spool stroke amount of the control valve 21, and the flow rate ratio of the hydraulic fluid discharged from the pump to the circuit leading to the lift cylinder 14 and the circuit leading to the tank 22, and is specific to the type of control valve 21.

The third master data is in the form of a table that shows the correlation between the cylinder pressure and spool stroke amount, and the flow rate returning from the control valve 21 to the tank 22. This third master data also includes the flow control valve 23 shown in Figures 2 to 4 as a set. Therefore, this correlation data is specific to the control valve 21 if the flow control valve 23 is built into the control valve 21, and is specific to the set of the control valve 21 and the flow control valve 23 if the flow control valve 23 is outside the control valve 21 (built into the forklift vehicle).

Each master data is in table format here, and is obtained in advance by experiments, simulations, etc. for each type of hydraulic pump 26 or control valve 21, or for each type of forklift 1 on which it is mounted, and is recorded in the correlation data storage unit. Note that the relationships obtained by experiments or simulations may be expressed as formulas, and these formulas may be used as master data.

The calculation unit receives the measurement data output from each sensor, i.e., the rotation speed measurement data output from the rotation speed sensor 31, the discharge pressure measurement data output from the discharge pressure sensor 32, the stroke measurement data output from the stroke sensor 33, and the cylinder pressure measurement data output from the cylinder pressure sensor 34, at a predetermined sampling interval, calculates the flow rate of the working fluid flowing in and out of the lift cylinder 14 based on the values of each of these measurement data and each master data, calculates the height of the mast 13 based on this flow rate of the working fluid and specifications such as the cylinder volume and effective cross-sectional area that are pre-recorded in memory, and sequentially outputs this as a mast height measurement value.
<Mast height measurement procedure>

Next, the mast height measurement procedure will be specifically described with reference to FIG.
When the forklift 1 is started, the calculation unit first calculates an initial value of the mast height measurement value (step S1). In this embodiment, this initial value is, for example, the mast height measurement value measured and recorded when the forklift 1 finished the previous operation, and is stored in a mast height measurement data storage unit provided in a predetermined area of the memory. Alternatively, the lowest position of the mast 13 may be used as the initial value, or the initial value may be obtained by multiplying the elapsed time since the previous operation was completed by the natural descent speed per unit time (determined by the flow rate returning from the lift cylinder 14 to the tank 22 due to slight leakage from a valve, etc.) from the mast height measurement value at the previous operation completion.

Next, when a predetermined sampling time arrives (step S2), the calculation unit acquires the discharge pressure measurement data, rotation speed measurement data, and stroke measurement data (step S3).

Then, the calculation unit judges whether the mast height is a predetermined reference height (step S4). To make this judgment, a position sensor such as a limit switch attached to one or more locations on the mast 13 or lift cylinder 14 is used. This position sensor is designed to emit a signal when the mast 13 or lift cylinder 14 reaches the reference height.

It is also possible to determine the reference height from the values of each measurement data without using a position sensor. In this case, the reference height is preferably the highest or lowest position.

Whether the mast 13 is at its highest position is determined using the stroke measurement data and the discharge pressure measurement data. That is, the mast 13 is determined to be at its highest position when the value of the stroke measurement data (hereinafter referred to as the stroke measurement value) detects that the lift lever 16 is being operated to the up position, and the value of the discharge pressure measurement data (hereinafter referred to as the discharge pressure measurement value) detects that the discharge pressure of the hydraulic pump 26 is equal to the relief pressure of the relief valve 28 (or when this state continues for a certain period of time).

The mast 13 is determined to be at its lowest position by using the stroke measurement data and the cylinder pressure discharge pressure measurement data. That is, the mast 13 is determined to be at its lowest position when the stroke measurement value indicates that the lift lever 16 is being operated to the lowering side, and the cylinder pressure measurement data value (hereinafter referred to as the cylinder pressure measurement value) indicates that the pressure of the lift cylinder 14 is 0 or the pressure in the case of no load (pressure holding only the forks), or when the lift lever 16 has been operated to the lowering side for a certain period of time or more regardless of the cylinder pressure measurement value.
If the mast height is at the reference position, the mast height measurement value is set as the reference height, and this value is stored in the mast height measurement data storage unit (step S7).
Thereafter, if the forklift operation has not ended (step S8), the process returns to step S2.

On the other hand, if the mast height is not at the reference position, the calculation unit calculates the elevation distance of the mast 13 during the period from the previous sampling time to the current sampling time (step S5).
Then, the distance that is raised and lowered is added to the mast height measurement value stored in the mast height measurement data storage unit, and the calculated mast height measurement value is updated as a new mast height measurement value.
Thereafter, if the forklift operation has not ended (step S8), the process returns to step S2.

Next, step S5, that is, the mast raising/lowering distance calculation routine, will be described below with reference to FIG.
If it can be determined from the stroke measurement that the control valve 21 (or the lift lever 16) is in the stopped position (step S21), the calculation unit sets the lifting distance of the mast 13 to 0 (step S28) and maintains the mast height measurement at the previous value.

If it is determined from the stroke measurement that the control valve 21 (or the lift lever 16) is on the rising side (step S22), the calculation unit applies the discharge pressure measurement value and the rotation speed measurement value of the hydraulic pump 26 to the first master data and calculates the corresponding discharge flow rate _QP (step S23). At this time, if each measurement value is an intermediate value of the first master data, the calculation unit calculates the discharge flow rate _QP of the hydraulic pump 26 by interpolating using a known method.

The calculation unit also applies the discharge pressure measurement value and stroke measurement value of the hydraulic pump 26 to the second master data, and calculates a flow rate ratio α between the flow rate of the working fluid discharged from the hydraulic pump 26 flowing into the lift cylinder 14 and the flow rate returning to the tank 22 (step S24). Note that, as described above, when each measurement value is an intermediate value of the second master data, interpolation is performed. Here, α is the ratio of the flow rate QS _IN going to the lift cylinder 14 to the flow rate QT going to the tank 22, and can be expressed as α=QS _IN /QT.

Next, the calculation unit calculates the inflow flow rate _QSIN of the working fluid into the lift cylinder 14 based on the discharge flow rate _QP of the hydraulic pump 26 and the flow rate ratio α calculated in this manner (step S25).
Specifically, the inflow flow rate QS _IN is calculated based on the following equation (1).
_QSIN = _QP × (QSIN _{/ QSIN} + QT) = _QP × α / (α + 1) ... (1)

Next, the calculation unit calculates the stroke amount of the cylinder piston, that is, the lift distance _DM of the mast 13, based on the inflow flow rate QS _IN (step S26).
Specifically, the moving distance (ascent distance) _{D_M} is calculated based on, for example, the following formula (2).
D _M =Δt×Q S _IN /A (2)
where Δt is the sampling interval and A is the effective area of the cylinder.

Next, the calculation unit adds the ascending distance D _M to the mast height measurement value H _i-1 calculated at the time of the previous sampling as shown in equation (3) to obtain a new mast height measurement value H _i (step S27).
H _i = H _{i -1} + D _M ... (3)

On the other hand, if it can be determined from the stroke measurement that the control valve 21 (or the lift lever 16) is on the downward side (step S22), the calculation unit applies the cylinder pressure measurement value and the stroke measurement value to the third master data and calculates the flow rate QS _OUT of the working fluid returning from the lift cylinder 14 through the control valve 21 to the tank 22 (step S29).

Next, the calculation unit calculates the stroke amount of the cylinder piston, that is, the lowering distance D _M of the mast 13, based on this outflow flow rate QS _OUT (step S26).
Specifically, the lowering distance _{D_M} is calculated based on the following equation (4), for example.
D _M = Δt × Q S _OUT / A (4)
where Δt is the sampling interval and A is the effective area of the cylinder.

Next, the calculation unit subtracts the lowering distance D _M from the mast height measurement value H _(previous) calculated at the time of the previous sampling as shown in equation (3) to obtain a new mast height measurement value H _(present) (step S27).
H _{(this time)} = H _{(last time)} - D _M ... (5)
The calculation unit then outputs the mast height measurement value calculated in this manner, and displays it, for example, on a display device provided in the driver's seat of the forklift.
<Effects of this mast height measuring device 2>

The above configuration not only makes it possible to measure the mast height using existing sensors such as the RPM sensor 31, discharge pressure sensor 32, stroke sensor 33, etc., or inexpensive, easy-to-install sensors, but also ensures high measurement accuracy by calculating the flow rate of the working fluid flowing in and out of the lift cylinder 14 based on correlation data previously obtained through experiments, simulations, etc. for each type of hydraulic pump 26 or control valve 21, or for each type of forklift 1 on which it is mounted, and then calculating the mast height from that.

In addition, although the correlation data is in table format and some simple interpolation calculations may be necessary, the flow rate of the working fluid can basically be calculated simply by applying the values of each measurement data to the correlation data, which reduces the calculation load and ensures sufficient measurement speed and accuracy without using a high-performance (high-cost) CPU, for example.

Furthermore, in the above embodiment, the mast height is calculated by integrating the amount of working fluid flowing in and out of the cylinder, but any integral error that may occur during this calculation is reset by detecting the reference height, so that significant measurement errors due to accumulation of integral errors can be reliably avoided. As described above, an inexpensive sensor that can be easily installed, such as a limit switch, is used to detect this reference height, so that the configuration is not complicated and the price does not rise. Furthermore, if the reference height is set to the highest or lowest position of the mast 13, as described above, it is possible to avoid measurement errors due to accumulation of integral errors by utilizing the pump discharge pressure, etc., without using a dedicated sensor such as a limit switch.
<Other embodiments>
The present invention is not limited to the above-described embodiment.

In the above embodiment, the lift cylinder pressure was directly measured by a pressure sensor and the cylinder pressure measurement value was used to calculate the mast height during lowering, but there are cases where the cylinder pressure sensor is not installed, or where it is difficult to obtain the output data even if it is installed.

In such cases, for example, the lift cylinder pressure is proportional to the weight of the empty load, such as the mast weight or the carrier weight, plus the weight of the loaded luggage, so the weight of the luggage can be measured using a weight sensor installed on the carrier platform of the forklift, and the cylinder pressure measurement value can be indirectly calculated based on the value obtained by adding the measured weight to the empty load.

On the other hand, in the above embodiment, the cylinder pressure measurement value was not used when calculating the mast height during ascent. However, if the cylinder pressure measurement value is used, correlation data (fourth master data) between the discharge pressure of the hydraulic pump, the lift cylinder pressure, and the control valve spool stroke amount, and the inflow flow rate of the working fluid into the lift cylinder may be created and recorded in advance through experiments, simulations, etc., and the cylinder pressure measurement value, the discharge pressure measurement value of the hydraulic pump, and the stroke measurement value of the control valve may be fitted to the fourth master data to determine the inflow flow rate of the working fluid into the lift cylinder.
Also, the lift cylinder pressure may be calculated from the discharge pressure measurement value of the hydraulic pump and the stroke measurement value of the control valve when the lift is raised.

In the above embodiment, the mast height measuring device is attached to the forklift, but it may be provided separately from the forklift, with its functions being carried out by a mobile terminal used by the worker (driver), a computer used by the work manager, or a cloud computer. In that case, each sensor should be IoT-enabled so that the mast height measuring device can obtain each measurement data via a wireless line such as the Internet.

The data indicating the mast height measurement value calculated as described above (mast height measurement data) may be sent not only to the display device in the driver's seat of the forklift, but also to the mobile terminal or the computer of the work manager as mentioned above, and may be recorded in a log. It may also be notified by voice.

It is also possible to create and use correlation data using the weight of the load instead of the pressure inside the lift cylinder (cylinder pressure). Since the weight of the load has a one-to-one relationship with the cylinder pressure, the mast height can be calculated in the same way even if it is substituted.
The stroke measurement data can also be obtained from the amount of operation of the lift lever.
<Forklift operation diagnostic device>

Furthermore, the mast height measurement value thus obtained can be used to perform a forklift operation diagnosis. An example of this operation diagnosis will now be described.
Conventionally, in a forklift control device, the speed and the load weight are limited individually based on threshold values set for each mechanism, such as the weight of the load and the vehicle speed.

However, when actually operating a forklift, there are cases where multiple factors come together at the same time, creating a dangerous situation. For example, even with the same lift height, the degree of danger of the operation varies depending on the weight of the load, the vehicle speed, and the speed at which the mast is raised and lowered. Therefore, in the past, in actual work sites, forklift operators would use their own experience to judge the situation from the multiple factors mentioned above and avoid dangerous driving.

In the following, an example will be described in which the computing unit is provided with a function for automatically diagnosing the forklift operation based on multiple elements and visualizing the safety level. In other words, the mast height measurement device also functions as a forklift operation diagnosis device.
Specifically, the calculation unit calculates a safe operation index based on the luggage weight measurement value, the mast height measurement value, and the vehicle speed measurement value.

The luggage weight and mast height are measured as described above. Regarding vehicle speed, existing forklifts are equipped with a vehicle speed sensor, and the vehicle speed data output from this vehicle speed sensor is obtained. Alternatively, a rotation speed sensor may be attached to the axle, driving motor, etc. to obtain vehicle speed data.

Here, a predetermined operation evaluation function is stored in a predetermined area of the memory, and the calculation unit calculates a safe operation index by substituting the luggage weight measurement value, the mast height measurement value and the vehicle speed measurement value into this operation evaluation function.
This can be expressed by the following formula.
S = f(M, H, V)
Here, I is a safe operation index, f is an operation evaluation function, M is a measured luggage weight, H is a measured mast height, and V is a measured vehicle speed.

Furthermore, the calculation unit classifies the safe operation index S into a number of levels, for example, into the following three levels, depending on the value.
Level 1: A level stipulated in forklift safety regulations. Level 2: A level that exceeds level 1 but does not pose a problem with the structure of the forklift. Level 3: A level that exceeds level 2 and poses a high risk of the forklift tipping over.

The calculation unit sequentially records the thus calculated safe operation index and level in an operation index storage unit set in a predetermined area of the memory, together with the driver ID, time, etc.
At this time, in addition to the safe operation index, the luggage weight measurement value, the mast height measurement value and the vehicle speed measurement value may also be recorded in the operation index storage unit.

As described above, the operation status information including the safe operation index is displayed on a display device installed in the driver's seat of the forklift so that the operator can be notified immediately. This operation status information may also be sent to a terminal device or cloud computer used by the operation manager, recorded in a log, and used to manage the operation of the forklift by the worker.

With this configuration, the safety of forklift operation can be quantitatively and objectively evaluated from multiple sensing items, and dangerous lift heights can be diagnosed based on the weight of the load, and the operator can be alerted and a manager can be notified of dangerous conditions regarding driving speeds at dangerous heights, loading and unloading operation speeds, etc.
In addition, the safe operation index can be used to classify conditions that do not lead to accidents, and to perform energy saving diagnosis and evaluation of operator skills.

In addition, by adding the mast speed, which is the time-differentiated value of the mast height measurement, and the acceleration, which is the time-differentiated value of the vehicle speed, to the variables of the operation evaluation function, it is possible to add items such as danger diagnosis based on the mast operation speed and danger diagnosis based on sudden acceleration/deceleration of the forklift.
The mast height may also be measured, for example, by attaching a pulley-type winding gauge or a linear gauge to the mast raising and lowering cylinder.
To summarize the above, the following can be said:

(1) This forklift mast height measurement device comprises a correlation data storage unit which stores correlation data indicating a correlation between the discharge pressure of a hydraulic pump which supplies hydraulic fluid to a lift cylinder, the rotation speed of the hydraulic pump, a spool stroke amount of a control valve which controls the flow of hydraulic fluid into and out of the lift cylinder, and the flow rate of hydraulic fluid flowing in and out of the lift cylinder;
obtaining discharge pressure measurement data having a value related to a discharge pressure of the hydraulic pump, rotation speed measurement data having a value related to a rotation speed of the hydraulic pump, and stroke measurement data having a value related to a spool stroke amount of the control valve;
The present invention is characterized in that it is equipped with a calculation unit that calculates the flow rate of the working fluid flowing in and out of the lift cylinder from the values of the discharge pressure measurement data, rotation speed measurement data, and stroke measurement data by referring to the correlation data, and calculates the mast height based on the flow rate of the working fluid.

With this configuration, not only can the mast height be measured using existing sensors or inexpensive, easy-to-install sensors, but the flow rate of the working fluid flowing in and out of the lift cylinder can be calculated using correlation data that takes into account the unique characteristics of the hydraulic pump and control valve installed in the actual machine, allowing the mast height to be measured with high accuracy.

(2) The calculation unit determines whether the lift cylinder is rising based on the value of the stroke measurement data, and if it determines that the lift cylinder is rising, calculates the flow rate of the working fluid flowing into the lift cylinder by referring to the correlation data from the values of the discharge pressure measurement data, the rotation speed measurement data, and the stroke measurement data.
With this arrangement, it is possible to reliably determine when the mast is rising based on the stroke measurement data value, and the mast height can be calculated with high accuracy.

(3) as the correlation data, first master data representing a correlation between the discharge pressure and rotation speed of the hydraulic pump and a discharge flow rate of the hydraulic pump;
a second master data representing a correlation between the discharge pressure of the hydraulic pump and the spool stroke amount of the control valve, and a flow rate ratio of a flow rate supplied to a lift cylinder from the hydraulic pump via a control valve and a flow rate returning to a tank;
The calculation unit calculates the discharge flow rate of the hydraulic pump by referring to the first master data, and calculates the flow rate ratio by referring to the second master data, and calculates the flow rate of the working fluid flowing into the lift cylinder based on the hydraulic pump discharge flow rate and the flow rate ratio.

With this configuration, the correlation data is separated into first master data specific to the hydraulic pump and second master data specific to the control valve, making it easy to obtain each master data through experiments, etc.

(4) The forklift mast height measurement device further includes a correlation data storage unit that stores correlation data indicating a correlation between the cylinder load acting on the lift cylinder, a spool stroke amount of a control valve that controls the flow of hydraulic fluid in and out of the lift cylinder, and a flow rate of hydraulic fluid flowing in and out of the lift cylinder;
obtaining cylinder pressure measurement data having a value related to a pressure in the lift cylinder and stroke measurement data having a value related to a spool stroke amount of the control valve;
The present invention is characterized in that it is equipped with a calculation unit that calculates the flow rate of the working fluid flowing in and out of the lift cylinder from each value of the cylinder pressure measurement data and stroke measurement data by referring to the correlation data, and calculates the mast height based on the flow rate of the working fluid.
With this arrangement, the mast height during lowering can be measured with high accuracy using cylinder pressure measurement data.

(5) The calculation unit determines whether the lift cylinder is descending based on the value of the stroke measurement data, and if it determines that the lift cylinder is descending, calculates the flow rate of the working fluid flowing out of the lift cylinder by referring to the correlation data from each value of the cylinder pressure measurement data and the stroke measurement data, and calculates the mast height based on the flow rate of the working fluid.
With this arrangement, it is possible to reliably determine when the mast is lowered based on the stroke measurement data value, and the mast height can be calculated with high accuracy.

(6) As the correlation data, a third master data is provided which represents a correlation between the pressure of the lift cylinder and the spool stroke amount of the control valve, and a flow rate of the working fluid supplied from the hydraulic pump to the lift cylinder via the control valve,
The calculation unit calculates a flow rate of the working fluid flowing out of the lift cylinder by referring to the third master data.
With this configuration, the third master data can be obtained through experiments, simulations, or the like, making it possible to measure the mast height with high accuracy.

(7) Specifically, it is preferable to obtain the cylinder pressure measurement data from a cylinder pressure sensor that measures the pressure of the lift cylinder or a weight sensor that measures the weight of the luggage loaded on the forklift.

(8) The forklift mast height measuring device further comprises a correlation data storage unit that stores correlation data indicating a correlation between the discharge pressure of a hydraulic pump that supplies hydraulic fluid to the lift cylinder, the pressure of the hydraulic fluid in the lift cylinder, and a spool stroke amount of a control valve that controls the flow of hydraulic fluid in and out of the lift cylinder, and the flow rate of the hydraulic fluid in and out of the lift cylinder;
Acquire discharge pressure measurement data having a value related to a discharge pressure of the hydraulic pump, cylinder pressure measurement data having a value related to a pressure in the lift cylinder, and stroke measurement data having a value related to a spool stroke amount of the control valve,
The present invention is characterized by having a calculation unit that calculates the flow rate of the working fluid flowing in and out of the lift cylinder from the values of the discharge pressure measurement data, cylinder pressure measurement data, and stroke measurement data by referring to the correlation data, and calculates the mast height based on the flow rate of the working fluid.
By using the cylinder pressure measurement data in this manner, the mast height during raising can be measured without using the discharge flow rate of the hydraulic pump.

(9) The calculation unit determines whether the lift cylinder is rising based on the value of the stroke measurement data, and if it determines that the lift cylinder is rising, calculates the flow rate of the working fluid flowing into the lift cylinder from the values of the discharge pressure measurement data, the cylinder load data, and the stroke measurement data by referring to the correlation data.
With this arrangement, it is possible to reliably determine when the mast is rising based on the stroke measurement data value, and the mast height can be calculated with high accuracy.

(10) During ascent, the calculation unit can also calculate the value of the cylinder pressure measurement data based on the values of the discharge pressure measurement data and the stroke measurement data.

(11) This forklift operation diagnosis device is also characterized in that it calculates an operation safety index, which indicates the safety of forklift operation, based on luggage weight data having a value related to the weight of luggage loaded on the forklift's platform, platform height data having a value related to the height of the platform, and vehicle speed data having a value related to the forklift's vehicle speed.
Such a system would enable a quantitative and objective evaluation of the safety of forklift operation, which is made up of multiple factors, and would enable diagnosis of dangerous lift heights according to the weight of the load, alerting the operator to driving speeds at dangerous heights, cargo handling operation speeds, etc., and notifying managers of dangerous conditions. In addition, the safe operation index would enable classification of conditions that do not lead to accidents, enabling energy saving diagnosis and evaluation of operator skills.

(12) If the operation safety index is calculated based on platform ascent/descent speed data having a value related to the platform ascent/descent speed and/or acceleration data having a value related to the forklift acceleration, it becomes possible to perform an even more detailed and accurate operation evaluation.

To enable an intuitive understanding of the safety of forklift operation, it is preferable to classify and output the safety of operation into multiple levels based on the value of the operation safety index.

According to the present invention, not only can mast height be measured using existing sensors or inexpensive, easy-to-install sensors, but the flow rate of the working fluid flowing in and out of the lift cylinder can be calculated using correlation data that takes into account the unique characteristics of the hydraulic pump and control valve installed in the actual machine, allowing for accurate measurement of mast height.

100... Mast height measuring device (operation diagnostic device)
1...Forklift 21...Control valve 14...Lift cylinder 26...Hydraulic pump

Claims (7)

A forklift operation diagnostic device that calculates an operation safety index indicating the safety of forklift operation based on baggage weight data having a value related to the weight of the baggage loaded on the platform of the forklift, platform height data having a value related to the height of the platform, and vehicle speed data having a value related to the vehicle speed of the forklift. The forklift operation diagnosis device according to claim 1, further calculating the operation safety index based on platform ascent/descent speed data having a value related to the platform ascent/descent speed and/or acceleration data having a value related to the acceleration of the forklift. The forklift operation diagnosis device according to claim 1 or 2, which classifies and outputs the operation safety into multiple levels based on the value of the operation safety index. Further equipped with a forklift mast height measuring device,
2. The forklift operation diagnosis device according to claim 1, further comprising a step of calculating a platform height based on the mast height calculated by the mast height measuring device. The mast height measuring device,
a correlation data storage unit that stores correlation data indicating a correlation between a discharge pressure of a hydraulic pump that supplies a working fluid to a lift cylinder, a rotation speed of the hydraulic pump, a spool stroke amount of a control valve that controls the inflow and outflow of the working fluid to the lift cylinder, and a flow rate of the working fluid flowing in and out of the lift cylinder;
obtaining discharge pressure measurement data having a value related to a discharge pressure of the hydraulic pump, rotation speed measurement data having a value related to a rotation speed of the hydraulic pump, and stroke measurement data having a value related to a spool stroke amount of the control valve;
and a calculation unit that calculates a flow rate of the working fluid flowing in and out of the lift cylinder from each of the discharge pressure measurement data, the rotation speed measurement data, and the stroke measurement data by referring to the correlation data, and calculates a mast height based on the flow rate of the working fluid. The mast height measuring device,
a correlation data storage unit that stores correlation data indicating a correlation between the pressure in the lift cylinder and a spool stroke amount of a control valve that controls the inflow and outflow of the working fluid to the lift cylinder, and a flow rate of the working fluid flowing in and out of the lift cylinder; acquiring cylinder pressure measurement data having a value related to the pressure in the lift cylinder and stroke measurement data having a value related to the spool stroke amount of the control valve,
and a calculation unit that calculates a flow rate of the working fluid flowing in and out of the lift cylinder from each value of the cylinder pressure measurement data and the stroke measurement data with reference to the correlation data, and calculates a mast height based on the flow rate of the working fluid. The mast height measuring device,
a correlation data storage unit that stores correlation data indicating a correlation between a discharge pressure of a hydraulic pump that supplies a working fluid to a lift cylinder, a pressure in the lift cylinder, a spool stroke amount of a control valve that controls the inflow and outflow of the working fluid to the lift cylinder, and a flow rate of the working fluid flowing in and out of the lift cylinder;
Acquiring discharge pressure measurement data having a value related to a discharge pressure of the hydraulic pump, cylinder pressure measurement data having a value related to a pressure in the lift cylinder, and stroke measurement data having a value related to a spool stroke amount of the control valve;
and a calculation unit that calculates a flow rate of the working fluid flowing in and out of the lift cylinder from each of the discharge pressure measurement data, the cylinder pressure measurement data, and the stroke measurement data by referring to the correlation data, and calculates a mast height based on the flow rate of the working fluid.