JP6675239B2 - forklift - Google Patents

Description

  The present invention relates to a forklift.

An industrial vehicle equipped with a working machine uses power generated by an internal combustion engine for moving the vehicle and driving the working machine. When the work machine is driven while the vehicle is stopped, it is necessary to cut off the power transmission to the drive system of the vehicle. An inching pedal is provided to shut off power transmission to the system.
Patent Document 1 discloses an invention in which the inching operation feeling at the time of depressing an inching pedal is improved by adjusting a timing at which a clutch is disengaged and a timing at which a braking force is applied to wheels at approximately the same time.

JP-A-2002-283888

  In the invention described in Patent Literature 1, the driving force may suddenly increase when the operation amount of the inching pedal is reduced.

  According to the first aspect of the present invention, the forklift is configured to connect the power transmission from the prime mover to the wheels based on the clutch hydraulic pressure in a connected state and a semi-connected state, based on the clutch hydraulic pressure. State, the clutch controlling between the disengaged state, and controlling the hydraulic output unit based on the operation amount of the inching pedal, the first characteristic until the inching pedal is operated from the non-operation position to the maximum operation position, the first characteristic, A hydraulic control unit that adjusts the clutch oil pressure with a second characteristic until the inching pedal is operated from the maximum operation position to the non-operation position, wherein the first characteristic is that the inching pedal is moved from the non-operation position to the intermediate operation position. Until the connection state is reached, the intermediate operation position is in the semi-connected state, and the first region beyond the intermediate operation position is in the semi-connected state. The clutch characteristic is a characteristic including at least a range in which the clutch oil pressure gradually decreases at a first rate of change toward the disconnection state, and the second characteristic is that the disconnection is performed until the inching pedal moves from the maximum operation position to the intermediate operation position. From the state, the clutch hydraulic pressure is gradually increased toward the half-connected state, and in a second region below the intermediate operation position, the range in which the clutch hydraulic pressure is gradually increased at the second rate of change from the half-connected state toward the connected state is set. It is a characteristic that includes at least.

  According to the present invention, when the operation amount of the inching pedal is reduced, the applied pressure to the clutch is continuously increased, so that the driving force can be gradually increased.

FIG. 2 is a side view of the forklift 1. FIG. 2 is a diagram showing a configuration of a cabin 6. FIG. 2 is a diagram illustrating a configuration of a drive system 3. It is a figure showing three inching characteristics. 5 is a flowchart illustrating an operation of the controller 20. FIG. 14 is a diagram illustrating a clutch oil pressure when the inching operation amount starts to increase in the second embodiment. FIG. 13 is a diagram illustrating a clutch oil pressure when the inching operation amount is reduced again after the inching operation amount starts to increase in the second embodiment. 10 is a flowchart illustrating an operation of a controller 20 according to the second embodiment.

(First Embodiment)
Hereinafter, a first embodiment of a forklift according to the present invention will be described with reference to FIGS.
(Constitution)
FIG. 1 is a side view of a forklift 1 according to a first embodiment of the present invention. The forklift 1 includes a mast frame 22 at a front portion of the vehicle body 2. The mast frame 22 is provided with a vertically movable fork 24. The vehicle body 2 includes a cabin 6 including a driver's seat 25, wheels 27 for moving the vehicle body 2, and a storage unit 28 in which the engine 30, the controller 20, and the like are stored.

  FIG. 2 is a diagram showing a configuration of the cabin 6. The cabin 6 includes, in addition to the driver's seat 25, a plurality of operating devices operated by an operator, that is, a steering wheel 61 used for instructing a steering angle, a forward / reverse lever 62 for instructing a traveling direction, and a tilt operation of the fork 24. , A lift lever 64 used to raise and lower the fork 24, an accelerator pedal 65 used to adjust the engine output, a brake pedal 66 used to adjust the braking force of the forklift 1, An inching pedal 67 and an inching characteristic selection switch 68 described later are provided.

Inputs to these operating devices by the operator are respectively detected by detectors described later, and input to the controller 20. The inching pedal 67 is mechanically connected to the brake pedal 66. When the inching pedal 67 is depressed by a predetermined operation amount or more, the brake pedal 66 is automatically depressed in conjunction with the inching pedal 67.
The inching characteristic selection switch 68 is a switch for the operator to select the operation characteristic of the forklift, and can be selected from three types of quick characteristic, standard characteristic, and mild characteristic.

FIG. 3 is a diagram illustrating, among the devices stored in the storage unit 28, devices related to the driving of the forklift 1, that is, the configuration of the drive system 3 and devices that output operation commands to the drive system 3. The double line in FIG. 3 represents the transmission of the driving force, the solid line represents the transmission of the hydraulic pressure, and the broken line represents the transmission of the operation command.
The drive system 3 includes an engine 30, a torque converter 31, a transmission 32, a propeller shaft 33, a differential device 34, and a drive shaft 35.
The engine 30 generates power required for running the forklift 1 and for cargo handling. The power generated by the engine 30 is supplied to a torque converter 31 and a pump 41 for pumping hydraulic oil.

Torque converter 31 transmits the power generated by engine 30 to transmission 32 via a fluid.
The transmission 32 switches the gear train to the speed stage selected by the operator, increases or decreases the power of the engine 30 transmitted via the torque converter 31 according to the selected speed stage, and outputs the power to drive the propeller shaft. Drive rotationally. The transmission 32 determines the rotation direction of the propeller shaft 33 based on an operation input to the forward / reverse lever 62 by the operator.

  The transmission 32 includes a wet-type multi-plate forward clutch 321 and a wet-type multi-plate reverse clutch 322. The forward clutch 321 and the reverse clutch 322 are driven by hydraulic pressure (hereinafter, referred to as “clutch hydraulic pressure”) applied by the forward solenoid valve 42 and the reverse solenoid valve 43, respectively. The forward clutch 321 and the reverse clutch 322 are controlled according to the clutch oil pressure into three states: an engaged state, a half-clutch state (slip state), and a released state. That is, the forward clutch 321 and the reverse clutch 322 connect or disconnect the power transmission path from the engine 30 to the wheels 27 based on the applied clutch oil pressure. The state in which the power transmission path is connected is called a fastening state, and the state in which the power transmission path is disconnected is called an open state. When the clutch oil pressure increases rapidly, the clutch changes from the released state to the engaged state, and an impact is generated on the forklift 1. In the first embodiment, any one of the quick characteristic, the standard characteristic, and the mild characteristic can be selected by the inching characteristic selection switch 68. When the standard characteristic or the mild characteristic is selected, the sudden increase in the clutch oil pressure is performed. The increase is suppressed. The difference in characteristics will be described later.

The forward solenoid valve 42 adjusts the hydraulic pressure of the hydraulic oil supplied from the pump 41 and outputs the hydraulic fluid to the forward clutch 321 according to a command signal from the controller 20.
The reverse solenoid valve 43 adjusts the hydraulic pressure of the hydraulic oil supplied from the pump 41 and outputs the adjusted hydraulic oil to the reverse clutch 322 according to a command signal from the controller 20.
Propeller shaft 33 connects the output shaft of transmission 32 and the input shaft of differential device 34.
The differential device 34 transmits the rotation of the propeller shaft 33 to the left and right drive shafts 35. When it is necessary to generate a speed difference between the rotational speeds of the left and right drive shafts 35, such as when traveling on a curve, the speed difference is automatically given to enable smooth running. Wheels 27 are attached to the distal ends of the left and right drive shafts 35, respectively.

The braking device 5 includes a brake booster 51, a master cylinder 52, a drum brake 53, and a brake fluid pressure sensor 54.
The brake booster 51 is connected to the brake pedal 66, and reduces the force required to operate the brake pedal 66 using the negative suction pressure of the engine 30.
The master cylinder 52 generates a hydraulic pressure (hereinafter, referred to as “brake hydraulic pressure”) for operating the drum brake 53 according to the amount of depression of the brake pedal 66. The brake fluid pressure increases as the depression amount of the brake pedal 66 increases.
The drum brake 53 includes a drum that rotates together with the wheels 27 and a brake shoe to which a friction material is attached. A braking force is generated by pressing the brake shoe against the drum according to the brake fluid pressure. As the brake fluid pressure applied from the master cylinder 52 to the drum brake 53 increases, the pressing force of the brake shoe increases, so the braking force of the forklift 1 increases.

The brake fluid pressure sensor 54 detects a brake fluid pressure applied from the master cylinder 52 to the drum brake 53.
The accelerator pedal 65 is provided with an accelerator stroke sensor 65A that detects the amount of depression of the accelerator pedal 65 (hereinafter, referred to as "accelerator operation amount").
The inching pedal 67 is provided with an inching stroke sensor 67A that detects the amount of depression of the inching pedal 67 (hereinafter, referred to as “inching operation amount”). By operating the inching pedal 67, the clutch oil pressure of the engaged clutch (hereinafter referred to as “engaged clutch”) of the forward clutch 321 and the reverse clutch 322 is adjusted.

The forward / reverse lever 62 is provided with a forward / backward lever position detection sensor 62A that detects the position of the forward / backward lever 62.
When the inching pedal 67 is depressed, the clutch oil pressure is controlled according to the inching operation amount. As described above, the clutch oil pressure is the oil pressure applied to the engagement clutch (forward clutch 321 or reverse clutch 322), and the engagement clutch is controlled to three states of an engagement state, a half-clutch state, and a release state. Further, the brake fluid pressure changes according to the inching operation amount, and a braking force corresponding to the brake fluid pressure is generated. Note that the relationship between the inching operation amount and the clutch oil pressure of the engagement clutch differs depending on the inching characteristics set by operating the inching characteristics selection switch 68.

The controller 20 includes a CPU, a ROM, and a RAM, expands a program stored in the ROM into the RAM, and executes the program. Signals are input to the controller 20 from the above-described brake fluid pressure sensor 54, forward / backward lever position detection sensor 62A, accelerator stroke sensor 65A, inching stroke sensor 67A, and inching characteristic selection switch sensor 68A.
When the forward / reverse lever 62 is switched to the forward position, the controller 20 controls the forward solenoid valve 42 and the reverse solenoid valve 43 so that the forward clutch 321 is engaged and the reverse clutch 322 is released. On the other hand, when the forward / reverse lever 62 is switched to the reverse position, the controller 20 places the forward clutch 321 in the released state and the reverse clutch 322 in the engaged state. When the forward / reverse lever 62 is switched to the neutral position, the forward clutch 321 and the reverse clutch 322 are released.

The controller 20 sets the inching characteristic of the forklift 1 to one of the quick characteristic, the standard characteristic, and the mild characteristic based on the output of the inching characteristic selection switch sensor 68A.
The controller 20 controls the forward solenoid valve 42 or the reverse solenoid valve 43 according to the inching operation amount and the set inching characteristics, and controls the clutch oil pressure applied to the engagement clutch.

  The ROM of the controller 20 stores inching characteristics indicating the relationship between the inching operation amount and the target clutch oil pressure. In the present embodiment, there are three inching characteristics: a quick characteristic Tq, a standard characteristic Ts, and a mild characteristic Tm. The inching characteristics may be stored as a look-up table or as a function. The controller 20 determines which inching characteristic to use, then specifies a clutch hydraulic pressure uniquely determined from the inching operation amount and the inching characteristic, and sets a target clutch hydraulic pressure (hereinafter referred to as a “target clutch hydraulic pressure”). To be determined. Then, the controller 20 outputs an operation command to the forward solenoid valve 42 or the reverse solenoid valve 43 so that the clutch oil pressure becomes the target clutch oil pressure.

FIG. 4 is a diagram showing a quick characteristic Tq, a standard characteristic Ts, and a mild characteristic Tm, which are three inching characteristics. The horizontal axis in FIG. 4 represents the inching operation amount, and the vertical axis represents the clutch oil pressure. The right side in FIG. 4 shows that the inching operation amount is larger, that is, the inching pedal 67 is further depressed. In the state of the clutch oil pressure Pmax, the clutch selected by the forward / reverse lever 62 is engaged, and in the state of the clutch oil pressure P0, the forward clutch 321 and the reverse clutch 322 are released.
The white circles in FIG. 4 are used for describing characteristics, and are hereinafter referred to as “characteristic points”. When the characteristic points shown in FIG. 4 are specified in the form of (inching operation amount, clutch oil pressure), characteristic point A is (S4, Pmax), characteristic point B is (S4, P2), and characteristic point C is (S5, P5). P0), the characteristic point D is (S1, Pmax), and the characteristic point Z is (S0, Pmax).

  The quick characteristic Tq indicated by the solid line in FIG. 4 indicates that the clutch oil pressure is constant at Pmax in the section where the inching operation amount is S0 to S4, and the clutch oil pressure discontinuously decreases from Pmax to P2 when the inching operation amount reaches S4. That is, it decreases rapidly. Let the rate of change at this time be α. Then, in the section where the inching operation amount is S4 to S5, the clutch oil pressure continuously changes from P2 to P0 at a change rate Δ. That is, the quick characteristic Tq is represented by “ZABC” using characteristic points.

The standard characteristic Ts indicated by a broken line in FIG. 4 indicates that the clutch oil pressure is constant at Pmax in the section where the inching operation amount is S0 to S1, and the clutch oil pressure changes from Pmax to P2 in the section where the inching operation amount is S1 to S4. It changes continuously, and in the section where the inching operation amount is S4 to S5, the clutch oil pressure continuously changes from P2 to P0 at a change rate Δ. That is, when the standard characteristic Ts is represented by using characteristic points, it is "ZDBC". However, as described later, in the present embodiment, the quick characteristic Tq is always used until the inching operation amount reaches S4. Therefore, when the standard characteristic Ts is selected, the inching operation amount changes from S0 to S5 to S0. The inching characteristic at this time is represented by "ZABBCBDZ" using characteristic points.
The mild characteristic Tm indicated by a dashed line in FIG. 4 indicates that the clutch oil pressure continuously changes from Pmax to P2 at the rate of change γ in the section where the inching operation amount is S0 to S4, and the clutch hydraulic pressure changes in the section where the inching operation amount is S4 to S5. The oil pressure continuously changes from P2 to P0 at a change rate Δ. That is, the mild characteristic Tm is represented by “ZBC” using characteristic points. However, as described later, in the present embodiment, the quick characteristic Tq is always used until the inching operation amount reaches S4. Therefore, when the mild characteristic Tm is selected, the inching operation amount changes from S0 to S5 to S0. The inching characteristic at this time is represented by “ZABBCZ” using characteristic points.

When the inching operation amount reaches S4 in the quick characteristic Tq, the inching operation amount and the clutch oil pressure are conceptually negatively infinitely correlated. The change rate at this time is α as described above. In the section where the inching operation amount of the standard characteristic Ts is S1 to S4, there is a negative correlation between the inching operation amount and the clutch oil pressure. As described above, the change rate is β. In the section where the inching operation amount of the mild characteristic Tm is S0 to S4, there is a negative correlation between the inching operation amount and the clutch oil pressure. The change rate at this time is γ as described above. Common to the three characteristics, in the section where the inching operation amount is S4 to S5, there is a negative correlation between the inching operation amount and the clutch oil pressure. The change rate at this time is Δ as described above.
At this time, when these rates of change are evaluated by absolute values, there is a relationship of | Δ | <| γ | <| β | << | α |.

  The controller 20 determines the clutch oil pressure for the inching operation amount according to the inching characteristic selected by the inching characteristic selection switch 68. In this embodiment, the quick characteristic Tq is always used until the inching operation amount reaches S4, and when the inching operation amount decreases after the inching operation amount exceeds S4, the inching characteristic selected by the inching characteristic selection switch 68. Use

(flowchart)
The operation of the program for realizing the operation of the controller 20 described above will be described.
FIG. 5 is a flowchart showing the operation of a program for determining the target clutch hydraulic pressure by the controller 20. The subject of execution of this program described below is the CPU of the controller 20. The “flag” appearing in the flowchart described below is data for managing whether or not the inching operation amount has reached S4, and is set to ON (1) when the inching operation amount exceeds S4. When the inching operation amount becomes S0, it is set to off (zero). In FIG. 5, "inching operation amount" is described as "operation amount".
In step S301, it is determined whether or not the inching operation amount is S0. If it is determined that the inching operation amount is S0, the process proceeds to step S320, the flag is set to off (zero), and the process proceeds to step S310. In step S310, the quick characteristic Tq described with reference to FIG. 4 is set as the inching characteristic. Proceed to step S307. When the quick characteristic Tq is set, in step S307, the clutch oil pressure is determined according to the detected inching operation amount. In both the process of increasing and decreasing the inching operation amount, the clutch oil pressure determined from the inching operation amount has the same value. Further, in the first embodiment, the quick characteristic Tq is set to the inching characteristic and the inching operation amount is reduced from zero to the maximum value S5 regardless of whether the standard characteristic or the mild characteristic is selected. The clutch oil pressure is determined.

If it is determined in step S301 that the inching operation amount is not S0, the process proceeds to step S302. In step S302, the characteristic selected by the inching characteristic selection switch 68 is determined, and if it is determined that the operator has selected the quick characteristic Tq, the process proceeds to step S310, where it is determined that the operator has selected other than the quick characteristic Tq. Then, the process proceeds to step S303.
In step S303, it is determined whether or not the inching operation amount is equal to or more than S4. If it is determined that the inching operation amount is equal to or more than S4, the flag is set to ON (1) in step S309, and the process proceeds to step S310. If it is determined that the inching operation amount is less than S4, the process proceeds to step S304.
In step S304, it is determined whether or not the flag is on (1). If it is determined that the flag is on, the process proceeds to step S305. If it is determined that the flag is off, the process proceeds to step S310.
In step S305, it is determined based on the signal from the inching characteristic selection switch 68 whether the operator has selected the standard characteristic or the mild characteristic. When it is determined that the operator has selected the standard characteristic Ts, the process proceeds to step S306, and when it is determined that the operator has selected the mild characteristic Tm, the process proceeds to step S308.

In step S306, the standard characteristic Ts is set as the inching characteristic, and in step S308, the mild characteristic Tm is set as the inching characteristic, and the process proceeds to step S307.
In step S307, the clutch hydraulic pressure corresponding to the inching operation amount is specified with reference to the set inching characteristics, and this is determined as the target clutch hydraulic pressure. Thus, the flowchart illustrated in FIG. 5 ends.
Step S310 is processing for setting the quick characteristic Tq as the inching characteristic, and is executed in the following cases.
(1) The operation is performed when the operator selects the quick characteristic Tq with the inching characteristic selection switch 68 and it is determined in step S302 that the quick characteristic Tq is selected.
(2) If the inching operation amount is equal to or larger than S4 and the determination in step S303 is affirmative, the process is executed after the flag is set to 1 in step S309.
(3) When the inching operation amount is less than S4 and the flag is not 1, the processing is executed when step S304 is negatively determined.
(4) Executed after resetting the flag to 0 in step S320 when the inching operation amount is zero.

In the forklift 1 of such an embodiment, the following smooth operation can be performed by the depression amount of the inching pedal 67.
For example, when the empty forklift 1 loads a load, the accelerator pedal 65 is depressed to advance toward the load. When the forklift 1 approaches the load, the operator depresses the inching pedal 67 to reduce the transmission of torque to the wheels 27. When the forklift 1 further approaches the load, the operator further depresses the inching pedal 67. When the inching pedal 67 is depressed by a predetermined amount or more, the brake pedal 66 is depressed in conjunction therewith, and a braking force is generated. When the fork is correctly inserted into the pallet, the inching pedal 67 is fully depressed (inching operation amount S5), and the forklift 1 is stopped. At this time, the accelerator pedal is depressed, and the fork operation lever is raised to lift the fork, that is, the load. Then, the forward / reverse lever is operated to reverse.

  Next, the operator releases the inching pedal 67 and transmits the torque output by the engine 30 to the wheels 27. At this time, if the inching characteristic selection switch 68 has selected the standard characteristic Ts or the mild characteristic Tm by the operator, even if the inching pedal 67 is rapidly released by the operator, the broken line in FIG. The clutch oil pressure with respect to the inching operation amount increases smoothly so as to trace the indicated inching characteristics. That is, when the inching pedal 67 is rapidly released and released, the clutch transmission torque does not increase sharply when the inching operation amount becomes equal to or less than S4, and the impact is reduced in the operation from the stop to the start of traveling. In other words, the change rate of the clutch oil pressure is smaller in the standard characteristic Ts and the mild characteristic Tm than in the quick characteristic Tq.

According to the first embodiment, the following operation and effect can be obtained.
(1) The forklift 1 is configured to output a clutch oil pressure based on the operation amount of the inching pedal 67, that is, the forward solenoid valve 42 and the reverse solenoid valve 43, and the motor 30 to the wheels 27 based on the clutch oil pressure. The hydraulic output unit is controlled based on the operation amount of the inching pedal 67 and the forward clutch 321 and the reverse clutch 322 for controlling the power transmission between the connected state, the half-connected state, and the disconnected state. ) From the maximum operation position (S5) to the first characteristic, and the second characteristic from the maximum operation position (S5) to the non-operation position (S0) until the inching pedal is operated to the non-operation position (S0). A controller, that is, a controller 20 is provided. The first characteristic is that the inching pedal 67 is in a connected state from the non-operation position (S0) to the intermediate operation position (S4), a semi-connected state when the inching pedal 67 is in the intermediate operation position (S4), and a state exceeding the intermediate operation position (S4). In one region (the region where the inching operation amount is larger than S4), the characteristic includes at least a range in which the clutch oil pressure gradually decreases at the first rate of change Δ from the semi-connected state to the disconnected state. The second characteristic is that the clutch oil pressure is gradually increased from the disconnected state to the semi-connected state until the inching pedal 67 is changed from the maximum operation position (S5) to the intermediate operation position (S4), and the inching pedal 67 falls below the intermediate operation position (S4). In the second region (the region where the inching operation amount is smaller than S4), the characteristic includes at least a range in which the clutch oil pressure gradually increases at the second rate of change from the semi-connected state to the connected state.
When the inching pedal 67 is moved to the maximum operation position (S5) and then falls below the intermediate operation position (S4), the clutch oil pressure gradually increases from the semi-connected state to the connected state, and the forklift is suddenly connected to the forklift. 1 can be suppressed from occurring. When an impact is applied to the forklift 1, the traveling performance of the forklift 1 is deteriorated, and not only is the physical and mental burden on an operator who is riding the forklift 1, but also the forklift 1 passes through the mast frame 22 and the fork 24. The load on the fork 24 is also impacted. In that case, the cargo may collapse or be damaged. However, according to the engagement device 10 described in the present embodiment, such a problem can be suppressed.

(2) The first characteristic includes a characteristic that, at the intermediate operation position (S4), the first clutch hydraulic pressure (Pmax) in the connected state is rapidly reduced to the second clutch hydraulic pressure (P4) in the semi-connected state. The second characteristic is that, after the second clutch oil pressure (P4) is displaced from the maximum operation position (S5) to the intermediate operation position (S4) and becomes a semi-connected state, and then toward the first clutch oil pressure (Pmax). Includes escalating characteristics.
Therefore, when the inching operation amount is increased, the clutch oil pressure can be rapidly reduced while providing a dead zone, and a semi-connected state can be achieved. Further, when the inching operation amount is reduced, the clutch hydraulic pressure is gradually increased from the semi-connected state to smoothly transition to the connected state, and it is possible to suppress the generation of an impact on the forklift 1.

(3) A plurality of second change rates β and γ are provided, and an inching characteristic selection switch 68A for selecting one of the plurality of second change rates is further provided. The controller 20 controls the pressure of the clutch oil pressure in the second region based on the second characteristic having any rate of change selected by the inching characteristic selection switch 68A.
Therefore, the operator can select the inching characteristic of the second area according to the work content and the load.

(Modification)
The above-described first embodiment may be modified as follows.
(1) The forklift 1 does not include the inching characteristic selection switch 68. When the inching operation amount increases, the inching characteristic is equivalent to the quick characteristic. When the inching operation amount falls below S4, either the standard characteristic Ts or the mild characteristic Tm is used. The characteristics may be set so as to be as follows.
(2) Four or more characteristics may be set to be selectable by the inching characteristic selection switch 68.
(3) The controller 20 may change the inching characteristics based on whether the inching operation amount has reached S5. In this case, the characteristics of the inching operation amounts S4 to S5 of the standard characteristic Ts and the mild characteristic Tm are defined similarly to the quick characteristic Tq. The controller 20 selects the quick characteristic until the inching operation amount reaches S5, regardless of the setting of the inching characteristic selection switch 68, and sets the inching characteristic selection switch 68 when the inching operation amount reaches S5. One of the inching characteristics is selected based on this. Thereafter, when the inching operation amount becomes S0, the quick characteristic Tq is selected again.

(Second embodiment)
A second embodiment of the engagement device according to the present invention will be described with reference to FIGS. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and the differences will be mainly described. The points that are not particularly described are the same as in the first embodiment. In the present embodiment, the clutch oil pressure determined by the controller 20 is different from that of the first embodiment mainly when the inching operation amount starts increasing while the inching operation amount of the inching pedal 67 is decreasing. .
(Constitution)
The hardware configuration of the forklift 1 according to the second embodiment is the same as that of the first embodiment. The operation of the program stored in the ROM of the controller 20 is different from that of the first embodiment.

(Operation of controller 20)
The controller 20 determines whether the standard characteristic Ts or the mild characteristic Tm has been selected by the inching characteristic selection switch 68 and the inching operation amount has reached S4 and the inching operation amount is in the section of S0 to S4. The target clutch oil pressure is determined as follows. That is, when the inching operation amount is reduced or maintained from S4, the clutch oil pressure corresponding to the inching operation amount in the selected characteristic is set as the target clutch oil pressure, as in the first embodiment. However, even if the inching operation amount starts increasing, the target clutch oil pressure is not decreased, and the target clutch oil pressure at the time when the inching operation amount starts increasing is maintained until the inching operation amount reaches S4. Further, when the inching operation amount decreases again after it starts increasing, the target clutch hydraulic pressure is set to Pmax.

  FIGS. 6 and 7 are diagrams showing the target clutch hydraulic pressure determined by the controller 20 in the second embodiment. Each of the drawings is a modification of FIG. 4 in the first embodiment. The characteristic points A to D and Z are the same as in the first embodiment. When the characteristic points E to J are specified in the form of (inching operation amount, clutch oil pressure), the characteristic point E is (S2, P3), the characteristic point F is (S4, P3), the characteristic point G is (S2, P4), The characteristic point H is (S4, P4), the characteristic point I is (S3, P3), and the characteristic point J is (S3, Pmax).

  FIG. 6 is a diagram showing the target clutch hydraulic pressure when the inching operation amount has started to increase. The target clutch oil pressure determined by the controller 20 when the inching operation amount changes to S0-S4-S5-S4-S2-S4-S5 when the mild characteristic Tm is selected by the inching characteristic selection switch 68 is shown. The characteristic point in No. 6 is “ZABCBCEFBC”. That is, even if the inching operation amount increases at the characteristic point E, the target clutch oil pressure is kept at P3 until the inching operation amount S4. The same applies to the case where the standard characteristic Ts is selected by the inching characteristic selection switch 68. If the inching operation amount changes in the same manner, when the inching operation amount increases at the characteristic point G, the target clutch is moved up to the inching operation amount S4. The oil pressure is constant at P4.

  FIG. 7 is a diagram illustrating a target clutch hydraulic pressure when the inching operation amount is reduced again after the inching operation amount starts increasing. However, FIG. 7 shows only the case of the mild characteristic Tm. When the inching operation amount changes to S0-S4-S5-S4-S2-S9-S0 when the mild characteristic Tm is selected by the inching characteristic selection switch 68, the target clutch oil pressure determined by the controller 20 is set to the value shown in FIG. Expressed in terms of characteristic points, it is "ZABBCEIJZ". That is, when the inching operation amount increases at the characteristic point E, the target clutch oil pressure is set to P3 until the inching operation amount S9 that continues to increase, and when the inching operation amount decreases, the target clutch oil pressure is set to Pmax.

(flowchart)
The operation of the program for realizing the operation of the controller 20 described above will be described.
FIG. 8 is a flowchart illustrating an operation of a program in which the controller 20 determines the target clutch hydraulic pressure in the second embodiment. The same processes as those in the first embodiment are denoted by the same step numbers, and description thereof is omitted. The subject of execution of this program described below is the CPU of the controller 20. In FIG. 8, “inching operation amount” is described as “operation amount” as in FIG. 5.

Until steps S306, S308, and S310, that is, until the characteristics are determined, it is the same as in the first embodiment. After steps S306, S308, and S310, the process proceeds to step S330.
In step S330, it is determined whether the inching operation amount is smaller than S4 and the flag is on (1). If it is determined that both conditions are satisfied, the process proceeds to step S331. If it is determined that at least one of the conditions is not satisfied, the process proceeds to step S307.
In step S331, it is determined whether or not the inching operation amount is greater than the immediately preceding inching operation amount. This is because when the inching operation amount continues to decrease, the clutch oil pressure is determined as in the first embodiment. If it is determined that it has increased, the process proceeds to step S332, and if it is determined that it has not increased, that is, it has decreased or has not changed, the process proceeds to step S307.

In step S332, the immediately preceding target clutch oil pressure (hereinafter, referred to as "oil pressure Pz") is stored, and the flow advances to step S333.
In step S333, the stored hydraulic pressure Pz is determined as the target clutch hydraulic pressure, and the flow advances to step S334.
In step S334, it is determined whether or not the inching operation amount is equal to or more than S4. This is because when the inching operation amount is equal to or more than S4, the target clutch hydraulic pressure is determined as in the first embodiment. If it is determined that it is equal to or more than S4, the process proceeds to step S307, and if it is determined that it is less than S4, the process proceeds to step S335.

In step S335, it is determined whether or not the increased inching operation amount has started to decrease. If it is determined that the amount has decreased, the process proceeds to step S336. If it is determined that the increase is maintained or the inching operation amount has not changed, the process returns to step S333.
In step S336, Pmax, which is the maximum clutch oil pressure, is determined as the target clutch oil pressure, and the flowchart in FIG. 8 ends.

According to the above-described second embodiment, the following operation and effect can be obtained in addition to the operation and effect of the first embodiment.
(4) The controller 20 reduces the operation amount of the inching pedal 67 from the operation amount in the first region (the region where the inching operation amount is larger than S4) to the operation amount in the second region (the region where the inching operation amount is smaller than S4). When the inching operation amount changes to increase in the second region, the clutch oil pressure at the time when the inching operation amount changes from decrease to increase is maintained until the inching pedal 67 reaches the intermediate operation position (S4).
Therefore, in the first region where the inching operation amount is less than S4, the driving force can be held by depressing the inching pedal 67, and stable traveling can be performed. Further, it is possible to suppress a change in the driving force when the inching operation amount reaches S4.

(5) When the inching pedal 67 decreases the operation amount in the first region from the operation amount in the first region to the operation amount in the second region, and thereafter, the operation amount changes to increase in the second region and further decreases, the clutch hydraulic pressure Is the first clutch hydraulic pressure (Pmax).
Therefore, even when the standard characteristic Ts and the mild characteristic Tm are selected, the maximum clutch oil pressure (Pmax) can be obtained without returning the inching operation amount to zero. Further, when the inching operation amount is less than S4, the target clutch oil pressure is continuously increased, so that a change in the driving force can be suppressed.

The above-described embodiments and modifications may be combined with each other.
Although various embodiments and modified examples have been described above, the present invention is not limited to these contents. Other embodiments that can be considered within the scope of the technical concept of the present invention are also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Forklift 10 ... Engagement device 20 ... Controller 30 ... Engine 30A ... Output shaft 67 ... Inching pedal 68 ... Inching characteristic selection switch 321 ... Forward clutch 322 ... Reverse clutch

Claims (5)

A hydraulic output unit that outputs clutch hydraulic pressure based on the operation amount of the inching pedal,
Based on the clutch oil pressure, a clutch that controls power transmission from the prime mover to the wheels between a connected state, a semi-connected state, and a disconnected state,
The hydraulic output unit is controlled based on the operation amount of the inching pedal, and the first characteristic is maintained until the inching pedal is operated from the non-operation position to the maximum operation position, and the inching pedal is operated from the maximum operation position to the non-operation position. And a hydraulic control unit for adjusting the clutch hydraulic pressure with the second characteristic until
The first characteristic is that the inching pedal is in the connected state from the non-operating position to the intermediate operating position, the semi-connected state when the inching pedal is in the intermediate operating position, and the semi-connected state in the first region beyond the intermediate operating position. A characteristic including at least a range in which the clutch oil pressure gradually decreases at the first rate of change toward the disconnected state;
The second characteristic is that the clutch hydraulic pressure is gradually increased from the disengaged state toward the semi-connected state until the inching pedal is moved from the maximum operation position to the intermediate operation position, and a second region below the intermediate operation position. A forklift having a characteristic including at least a range in which the clutch oil pressure gradually increases at a second rate of change from the semi-connected state to the connected state. The forklift according to claim 1,
The first characteristic includes a characteristic that, in the intermediate operation position, abruptly decreases from the first clutch hydraulic pressure in the connected state to the second clutch hydraulic pressure in the half-connected state,
The second characteristic is a forklift including a characteristic that after the second clutch oil pressure which is displaced from the maximum operation position to the intermediate operation position and becomes the semi-connected state, gradually increases toward the first clutch oil pressure. . The forklift according to claim 2,
A plurality of the second change rates are provided;
An inching characteristic selection unit that selects any one of the plurality of second change rates;
A forklift for controlling the pressure of the clutch oil in the second region based on the second characteristic having one of the rates of change selected by the inching characteristic selector. The forklift according to claim 2,
The hydraulic control unit,
When the inching pedal decreases from the operation amount in the first area to the operation amount in the second area, and then, when the operation amount turns to increase in the second area, the inching pedal reaches the intermediate operation position until the inching pedal reaches the intermediate operation position. Is a forklift for maintaining the clutch oil pressure when the operation amount changes from a decrease to an increase. The forklift according to claim 2,
The hydraulic control unit,
When the inching pedal decreases from the operation amount in the first region to the operation amount in the second region, and thereafter, the operation amount changes to increase and further decreases in the second region, the clutch oil pressure is reduced to the first amount. Forklift with clutch hydraulic pressure.

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