JP3460681B2 - Brake control device for industrial vehicles - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake control device for industrial vehicles.

[0002]

2. Description of the Related Art Conventionally, as a brake control device for this type of reach-type forklift truck (hereinafter, simply referred to as a forklift), there is one disclosed in, for example, Japanese Patent Application Laid-Open No. 9-233604. FIG. 13 is a schematic configuration diagram of the forklift disclosed in the publication. The front wheel 72 of the forklift 71 is a driven wheel, and the rear wheel 73 is a driving wheel and a steering wheel. A foot pedal 75 is provided on the floor surface of the operator's cab 74, and a limit switch 75a is provided on the stepping side of the foot pedal 75. The forklift 71 employs a so-called deadman brake in which the driver depresses the foot pedal 75 to turn on the limit switch 75a and release the brake.

The brake control device 76 includes a foot pedal 7
When 5 is opened and the limit switch 75a is turned off, the deceleration is calculated using the number of rotations input from the encoder 77, and when the deceleration increases rapidly, the drive wheels (rear wheels 73) slip. Determine that And
If the regenerative braking torque or the power generation braking torque by the traveling electric motor 78 is reduced, and if the rotation speed detection value from the encoder 77 recovers to a value equivalent to the vehicle speed, it is determined that the slip has been recovered, and the regenerative braking torque or the power generation braking is performed again. Increase the torque.

[0004]

However, although the brake control device 76 determines whether or not the drive wheel (rear wheel 73) has slipped and performs the brake control, it does not prevent the slip by reducing the brake torque. Therefore, the improvement of the braking force cannot be expected so much. Therefore, for example, there is a problem that the braking distance becomes longer on a water-wet road surface on which slip easily occurs or on an icy road surface in a frozen warehouse as compared with a dry road surface.

Further, when the slip control is performed by detecting the slip, the start delay of the brake control may be the highest at the vehicle speed at the start of braking, so that the control delay may be short (for example, in terms of time). 0.1 seconds or less), the vehicle will progress considerably. Therefore, the brake control operation delay is a major cause of increasing the braking distance, and it is also important to enhance the operation response of the brake control in order to keep the braking distance short.

The present invention has been made to solve the above problems, and its purpose is to effectively reduce the braking distance even in a traveling state or a cargo handling state where the braking distance may be lengthened. An object of the present invention is to provide a brake control device for an industrial vehicle that can be kept short.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 is to brake the drive wheels when the main braking means for braking the front wheels or the rear wheels, which are the drive wheels, is activated. Determination means for determining whether it is necessary to assist, hydraulic auxiliary braking means for applying an auxiliary braking force to the wheels on the front and rear sides of the drive wheel, and for operating the auxiliary braking means When a preliminary current is supplied to the electromagnetic valve means for adjusting the hydraulic pressure to be output and the electromagnetic valve means before the determination by the determination means, and when it is determined that the braking assistance is required by the determination, the auxiliary braking means is provided. And a control means for supplying a current for operating the electromagnetic valve means to the electromagnetic valve means. It should be noted that it does not prevent that the preliminary current is the same as the energizing current value at the time of operating the auxiliary braking means.

According to this structure, when the determination means determines that the braking assistance is required when the main braking means is activated, the auxiliary braking means is activated and the wheels (driving wheels) on the front and rear sides opposite to the main braking side are activated. A supplementary braking force is applied to the wheels. As a result, the braking distance of the vehicle can be suppressed to be short even when the braking distance may be increased only by the main braking. Further, since the preliminary current is supplied to the electromagnetic valve means in advance before the determination by the determination means, the determination means determines that the braking assistance is required, and the control means commands the energization for operating the auxiliary braking means. At this time, since the preliminary current has already been applied to the electromagnetic valve means, the operation response of the auxiliary braking means is enhanced.
Therefore, it is effective in reducing the braking distance.

According to a second aspect of the present invention, in the first aspect of the present invention, the control means applies a current to the electromagnetic valve means before the determination by the determination means so as not to open the valve. Use as a summary.

According to this structure, before the determination by the determination means, a current that does not open the valve is pre-energized to the electromagnetic valve means, so that the determination result of the determination means results and the auxiliary braking means is operated. When commanding energization, the spool has already moved within the range where the valve does not open. As a result, after it is determined that the auxiliary braking is necessary, the hydraulic pressure output from the electromagnetic valve means immediately rises, and the operation response of the auxiliary braking means is enhanced.

According to a third aspect of the present invention, in the first aspect of the invention, there is provided detection means for detecting the braking operation of the operation means for operating the main braking means, and the control means is the detection means. When the operation means detects that the operating means has been braked, the solenoid valve means is energized with a current having a value corresponding to the valve opening range to start the hydraulic pressure output, and the hydraulic pressure is raised. After the start, when the determination means determines that the auxiliary braking is required, a current according to the target hydraulic pressure is supplied to the electromagnetic valve means, while the determination means determines that the auxiliary braking is not required, The gist is to stop the energization for raising the hydraulic pressure to the electromagnetic valve means. It should be noted that the current value corresponding to the valve opening range and the current value corresponding to the target hydraulic pressure are not the same.

According to this structure, when the detection means detects that the operating means has been braked, the control means supplies a current having a value corresponding to the valve opening range to the electromagnetic valve means. As a result, the rise of the hydraulic pressure output from the electromagnetic valve means is started. When the determination means determines that the auxiliary braking is required after starting the hydraulic pressure rise, the control means energizes the electromagnetic valve means with a current according to the target hydraulic pressure. At the time of this energization command, the electromagnetic valve means has already opened and the hydraulic pressure has risen, so that the operation response of the auxiliary braking means is enhanced. On the other hand, when the determination means determines that the auxiliary braking is not necessary, the control means stops the energization of the solenoid valve means for starting.

According to a fourth aspect of the present invention, in the invention according to the third aspect, the control means opens the electromagnetic valve means before the detection means detects the braking operation of the operation means. The point is to apply a current that does not occur in advance.

According to this structure, the control means supplies a current to the electromagnetic valve means in advance so that the solenoid valve means is not opened before the braking operation of the operation means is detected. As a result, since the spool has already moved within the range in which the valve is not opened when the braking operation of the operating means is detected, when the electromagnetic valve means is energized with a current corresponding to the valve opening range when the braking operation is detected, The hydraulic pressure output from the valve means immediately rises. Therefore, even if the time from when the braking operation is detected until the result is judged is very short,
The hydraulic pressure at the time when the determination result is issued and the current is commanded to flow according to the target hydraulic pressure can be made as high as possible, and the operation response of the auxiliary braking means is further enhanced.

The invention according to claim 5 is the invention according to claim 3 or 4.
In the invention described in (3), when the hydraulic pressure output from the electromagnetic valve means and rising, the brake of the auxiliary braking means is applied at the time point when the judgment result by the judgment means gives a command to energize the electromagnetic valve means. The gist is that it is set so as to reach a value corresponding to the idle operation range before the effect starts or the actual operation initial range where the brake starts to operate.

According to this structure, when the judgment result of the judgment means is issued and the solenoid valve means is instructed to be energized, the hydraulic pressure output from the electromagnetic valve means and rising is raised to the idle operation range of the auxiliary braking means. Or, it reaches a value corresponding to the initial operating range. That is, at this time point, the auxiliary braking means has been operated up to the stage before the braking has already started or has been activated until the braking has started. Therefore, the time required for the remaining starting up from the time when the energization command is issued to the target hydraulic pressure is shortened, and the operation response of the auxiliary braking means is effectively improved.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the hydraulic pressure that has risen at the time point when the determination result is given and commands the energization causes the actual braking operation of the brake of the auxiliary braking means to start. The gist is that the value is set to reach the value corresponding to the initial range.

According to this structure, when the determination result is issued and the energization of the electromagnetic valve means is instructed, the hydraulic pressure output from the electromagnetic valve means and rising is actually actuated so that the brake of the auxiliary braking means starts to work. The value corresponding to the initial range has been reached.
That is, at this time, the auxiliary braking means is already operated until the braking starts. Therefore, the time required for the remaining starting up to the target hydraulic pressure is considerably shortened, and the operation response of the auxiliary braking means is more effectively improved. On the other hand, if the judgment result indicates that auxiliary braking is not required, the auxiliary brake will work even if the energization for raising the hydraulic pressure is stopped, but since the auxiliary brake only works for a moment, it has almost no effect on the vehicle speed. Without giving the driver a feeling of strangeness.

The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the determining means is:
The gist of the invention is to detect the slip of the wheel to which the braking force is applied by the main braking means and to determine that the auxiliary braking is necessary when the slip is detected.

According to this structure, the determining means detects the slip of the wheels (driving wheels) to which the braking force of the main braking means is applied, and when the slip is detected, it is determined that the auxiliary braking is necessary. Therefore, even if the drive wheel slips when the operating means is braked and the main braking means is operated, the auxiliary braking means is operated immediately after the slip occurs, and the wheels on the front and rear sides opposite to the slipped drive wheel (subordinate Auxiliary braking force is applied to both driving wheels and driving wheels. Therefore, the braking distance becomes relatively short even when the wheels slip during braking.

[0021]

[0022]

According to an eighth aspect of the present invention, in the invention according to any one of the first to seventh aspects, the industrial vehicle is one in which the driving wheels to which the braking force of the main braking means is applied are rear wheels.
The gist is that the wheel to which the braking force is applied by the auxiliary braking means is a front wheel, and the reach type forklift is equipped with a cargo handling device on the front side of the vehicle body so as to be movable back and forth.

According to this structure, in the reach type forklift, when it is determined that the braking force of the main braking means needs to be assisted when the operating means is braked, the auxiliary braking means is actuated immediately after the determination. A supplementary braking force is applied to the wheels on the front and rear sides of the main braked wheel. Therefore, when it is necessary to assist the main braking, the auxiliary braking force is applied to the wheels on the front and rear sides, and the auxiliary braking force is applied immediately after the determination, so that the braking distance is effective. Is shortened to.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS.

As shown in FIGS. 3 and 4, a reach-type forklift truck (hereinafter simply referred to as a forklift) 1 as an industrial vehicle is a three-wheel vehicle type having two front wheels and one rear wheel, and a vehicle body (machine). 2 is a battery vehicle that runs using the battery 3 housed in the front part of the vehicle 2 as a power source. A pair of left and right reach legs 4 extend forward from the vehicle body 2. The left and right front wheels 5 are driven wheels, and are rotatably supported by the tip ends of the respective reach rails 4a that form the left and right reach legs 4. The rear single wheel located on the rear side of the bottom portion of the vehicle body 2 is a rear wheel 6 that also serves as a drive wheel and a steering wheel, and the rear wheel 6 is offset to the left in the vehicle width direction. On the right side of the rear wheel 6, an auxiliary wheel (caster) 7 is provided at a position separated by a predetermined distance.

A standing seat type driver's seat (driver's cab) 8 is provided on the right rear portion of the vehicle body 2, and the rear side of the driver's cab 8 serves as an entrance / exit. An instrument panel 9 shown in FIG. 3 on the front side of the cab 8 is provided with a cargo handling lever 10 for a cargo handling operation and an accelerator lever 11 for a forward / backward movement operation. Storage box 1 standing upright next to the cab 8
A handle (steering wheel) 13 is provided on the upper surface of 2. As shown in FIG. 4, the storage box 12 accommodates a drive motor 14, a cargo handling motor 15, a cargo handling pump 16 and the like, and a front portion of the vehicle body 2 includes:
Oil tank 18, oil control valve (hereinafter,
Control valve) 19, brake control
A valve unit (hereinafter, brake control valve) 20 and the like are housed.

A mast device 21 as a cargo handling device is provided on the front side of the vehicle body 2. When the reach lever of the cargo handling lever 10 is operated, hydraulic oil is supplied and discharged through the control valve 19 so that the reach cylinder 22 is driven to expand and contract. Thus, the mast device 21 moves in the front-rear direction within the predetermined stroke range along the reach rail 4a. The mast device 21 includes a mast 23, a lift cylinder 24, and a fork 25. When the lift lever of the cargo handling lever 10 is operated, hydraulic oil is supplied and discharged through the control valve 19 and the lift cylinder 24 is expanded and contracted. , The fork 25 moves up and down in conjunction with the slide of the mast 23.

As shown in FIG. 4, the brake control valve 20 arranged below the floor surface of the operator's cab 8 uses the cargo handling pump 16 as a hydraulic pressure supply source similarly to the control valve 19. A hydraulic auxiliary brake device (front wheel brake device) 26 as an auxiliary braking means is attached to each of the left and right front wheels 5. The auxiliary brake device 26 is a drum brake device in this example. Left and right auxiliary braking device 26
Are connected to the brake control valve 20 via two pipes 27, respectively.

A front wheel rotation speed sensor 28 is attached to the lower surface of the reach leg 4. The front wheel rotation speed sensor 28 is, for example, a magnetic sensor, and detects the rotation speed of the front wheel 5 by detecting tooth portions formed on the wheel side surface of the front wheel 5 at a constant pitch in the circumferential direction.

FIG. 5 is a rear view showing the drive mechanism for the rear wheels (driving wheels). A main braking device (rear wheel braking device) 3 serving as a main braking device is provided above the drive motor 14.
1 is equipped. The main braking device 31 includes a disc 32 that rotates integrally with the rotary shaft 14 a of the drive motor 14.
Is composed of a pair of brake pads 31a to obtain a braking force. Main braking device 31
Is mechanically operatively connected to a brake pedal 34 via a link mechanism 33, and is a so-called deadman brake in which the brake is applied when the brake pedal 34 is not depressed. The brake pedal 34 that operates the main brake device 31 for operation constitutes an operating means.

On the upper part of the drive motor 14, there are two rotation speed sensors 35 each having a plurality of tooth portions (not shown) formed on the outer peripheral surface of the support portion of the disk 32 at a constant pitch in the circumferential direction as a detected portion. 36 is attached. The two rotation speed sensors 35 and 36 are arranged in parallel at positions 90 ° out of phase with each other, and output pulse signals 90 ° out of phase with each other.

The drive motor 14 is mounted on the upper surface of a link member 37 which constitutes a rear suspension mechanism, and a rear wheel is provided below a gear box 38 provided on the lower surface of the link member 37 so as to be relatively rotatable. The (driving wheel) 6 is rotatably supported. The steering gear 38a formed at the upper end of the gear box 38 is a handle 13
(See FIG. 3), the rear wheel 6 is steered according to the operation of the steering wheel 13. A steering angle sensor 39 is provided near the steering gear 38a, and the steering angle sensor 39 detects the rotational position of the steering gear 38a and outputs a signal of a voltage value corresponding to the steering angle (tire angle) of the rear wheels 6. Output. Further, a brake switch 40 is provided as a detecting means for detecting that the brake pedal 34 is in the brake operating position (depressing position).

FIG. 1 is a schematic configuration diagram (system configuration diagram) of a forklift. A brake switch 40, an accelerator sensor 43, a cargo handling operation detection switch 44, rotation speed sensors 35 and 36, a steering angle sensor 39, and a pressure switch 45 are electrically provided on the input side of a controller 41 as a control means provided in the forklift 1. It is connected to the. On the output side of the controller 41, two electromagnetic valves 46, 4 of the cargo handling motor 15 and the brake control valve 20 are provided.
7 and the motor drive circuit 48 are electrically connected. The motor drive circuit 48 has a built-in regenerative circuit 48a.

The brake switch 40 outputs a brake switch braking signal to the controller 41 when the brake operation is detected when the depression of the brake pedal 34 is released.
The accelerator sensor 43 detects the operation position of the accelerator lever 11, and outputs a signal of a voltage value corresponding to the operation amount for each of forward and reverse movements from the neutral position to the controller 41.

The controller 41 has an accelerator sensor 43.
The operation direction and the operation amount of the accelerator lever 11 are recognized based on the input signal value from, and the rotation direction command signal for instructing the motor rotation direction according to the operation direction and the motor output according to the operation amount are obtained. An output value command signal that commands the motor output value is output to the motor drive circuit 48. Further, the controller 41 sequentially detects the rotation direction of the rear wheel 6, that is, the vehicle traveling direction, by comparing the signal states (edge and level) of the respective pulse signals input from the two rotation speed sensors 35 and 36, and the accelerator lever When a signal indicating that the operation direction of 11 is opposite to the vehicle traveling direction (that is, a switchback operation) is input from the accelerator sensor 43, this is recognized as an accelerator braking signal. The controller 41 determines that the switchback is being performed while the accelerator braking signal is being input, and outputs the regeneration command signal to the motor drive circuit 48. The drive motor 14 is controlled in rotation direction and output based on the rotation direction command signal and the output value command signal input to the motor drive circuit 48, and the regenerative braking control is performed based on the regenerative command signal input to the motor drive circuit 48. To be done. The drive motor 14 that applies regenerative braking to the rear wheels 6 and the motor drive circuit 48 constitute the main braking means, and the accelerator lever 11 used for the switchback operation (braking operation) constitutes the operating means. Further, the rotation speed sensors 35, 36 for detecting a switchback operation (braking operation)
The accelerator sensor 43 constitutes a detecting means.

The cargo handling operation detection switch 44 detects that the cargo handling lever 10 has been operated, and is provided for each of the three levers 10a, 10b, 10c (see FIG. 2) (however, the lift lever 10a). The descending operation of is not detected). The controller 41 includes the cargo handling operation detection switch 4
When a signal indicating that the cargo handling lever 10 is operated is input from 4, the cargo handling motor 15 is driven. When the cargo handling motor 15 is driven, the cargo handling pump 16 is driven,
Hydraulic oil pumped from the oil tank 18 through the hose 50 passes through the hose 51 and the control valve 19
Is discharged. The hydraulic oil discharged from the control valve 19 is returned to the oil tank 18 through the hose 52.

A hose 53 branching from the hose 51 is connected to the brake control valve 20, and pressure oil from the cargo handling pump 16 is passed through the hose 53 to the brake control valve 20.
To be supplied to. The brake control valve 20 and the oil tank 18 are connected via a hose 54.

The pressure switch 45 is a pressure accumulation value (hydraulic pressure) of an accumulator 55 provided in the brake control valve 20.
Is detected to have reached the set lower limit value. The controller 41 also drives the cargo handling motor 15 when a detection signal is input from the pressure switch 45. The operation of the left and right auxiliary brake devices 26, 26 is controlled by the controller 41 performing excitation / demagnetization control (including current value control) on the two electromagnetic valves 46, 47 of the brake control valve 20.

Next, the hydraulic circuits of the cargo handling system and the braking system shown in FIG. 2 will be described. Material handling lever 10 (lift lever 10a, tilt lever 10b, reach lever 10
c) is mechanically connected to the control valve 19. When each of the levers 10a to 10c is operated, the cargo handling motor 15 is driven by the controller 41 based on the detection signal of the cargo handling operation detection switch 44 (see FIG. 1), and in response to the operation of each lever 10a, 10b, 10c. Corresponding ones of the lift cylinder 24, tilt cylinder 57, and reach cylinder 22 are driven.

The brake control valve 20 includes a pump port P, a tank port T and two brake ports B1 and B2.
It has a total of 4 ports. A hose 53 connected to the cargo handling pump 16 is connected to the pump port P, and a hose 54 connected to the oil tank 18 is connected to the tank port T. The two brake ports B1 and B2 are
The wheel cylinders 58, 58 of the left and right auxiliary brake devices 26, 26 are connected through two pipes 27, 27, respectively.

The brake control valve 20 includes a pressure reducing valve 59,
A check valve 60, an electromagnetic opening / closing valve (shut-off valve) 46, and an electromagnetic proportional pressure adjusting valve (linear solenoid valve) 47 are provided, and these valves 46, 47, 59, 60 are pump ports P.
And the brake ports B1 and B2 are connected in series on an oil passage 61. The pressure reducing valve 59 reduces the hydraulic pressure input from the pump port P. The check valve 60 provided on the oil passage 61 between the pressure reducing valve 59 and the shutoff valve 46 prevents the backflow of the working oil stored in the accumulator 55, and the accumulator 55 sets the set pressure (upper limit value). The valve opening pressure is set so that the valve is opened until () is reached.

The controller 41 includes a shutoff valve 46.
And each solenoid 46a, 47 of the linear solenoid valve 47
It is electrically connected to a. The shutoff valve 46 is
It is an on / off valve that is closed by the biasing force of the spring 46b when the solenoid 46a is demagnetized and opens when the solenoid 46a is excited. Further, the linear solenoid valve 47 is current value controlled by the controller 41,
The output hydraulic pressure (hydraulic pressure) is uniquely determined according to the current value input from the controller 41 to the solenoid 47a. The auxiliary brake device 26 operates by supplying hydraulic pressure to the wheel cylinders 58, and applies a braking force according to the hydraulic pressure value to the front wheels 5. The shutoff valve 46 and the linear solenoid valve 47 constitute an electromagnetic valve means.

The controller 41 has a built-in memory 41a. The memory 41a stores the auxiliary brake control program shown in FIG. 7 for controlling the operation of the auxiliary brake device 26, the map M shown in FIG. 6, and the like.
The auxiliary brake control program is used for the rear wheels 6 during vehicle braking.
When the slip of the vehicle is detected, the auxiliary brake devices 26, 26
Is operated to perform auxiliary brake control for applying an auxiliary braking force to the front wheels 5, 5.

The method of detecting the slip of the rear wheel 6 is as follows. The controller 41 obtains the rotation speed of the front wheel 5 based on the number of input pulses per unit time from the front wheel rotation speed sensor 28, and calculates the front wheel vehicle speed (driven wheel converted vehicle speed) Vf from the front wheel rotation speed and the front wheel radius. . Further, the controller 41 obtains the rotation speed of the rear wheel 6 based on the number of input pulses per unit time from the rear wheel rotation speed sensor 35, and based on the rear wheel rotation speed and the rear wheel radius, the rear wheel vehicle speed (driving wheel conversion). Vehicle speed)
Calculate Vr. Here, the forklift 1 is capable of in-situ turning around the center between the left and right front wheels 5, 5.
In the vicinity of the maximum steering angle when the steering wheel 13 is fully turned, there is a disadvantage that the rotation speed of the front wheel 5 on the turning inner wheel side becomes zero. Therefore, the rotation speed sensor 28 on the turning outer wheel side is used to obtain the front wheel vehicle speed Vf. The input signal is used with priority.
The controller 41 determines, based on the steering angle θ input from the steering angle sensor 39, which of the left and right front wheels 5 on the outer turning wheel side is located. It should be noted that, when the vehicle is traveling straight ahead (θ = 0), only the input signal from one of the left and right rotation speed sensors 28, which is predetermined, is used.

In this example, the correction coefficient K is taken into consideration that the front wheels 5 and the rear wheels 6 have different turning radii when the vehicle turns.
(Θ) (function of steering angle θ) is obtained according to the steering angle θ at that time, and the front wheel vehicle speed Vf is multiplied by the correction coefficient K (θ),
A vehicle speed V corresponding to the rear wheel position is obtained. This vehicle speed V corresponds to the rear wheel vehicle speed Vr when the rear wheels 6 are not slipping. Then, the controller 41 calculates the difference between the vehicle speed V and the rear wheel vehicle speed Vr as "slip speed" .DELTA.V (= V-Vr), and this slip speed .DELTA.V is a preset threshold value Vs.
When it exceeds, it is determined that the rear wheel 6 is slipping. The threshold value Vs is set to a value near the boundary where the friction coefficient between the rear wheel 6 and the road surface shifts from the static friction area to the dynamic friction area. For example, a value near 0.2 in terms of slip ratio is set. ing. The process of step 140 in FIG. 7 is a slip determination process for detecting the slip of the rear wheel 6. For slip determination, slip rate (= (V
It is also possible to use -Vr) / V).

When the rear wheel 6 slips and the slip speed ΔV exceeds the threshold value Vs during the brake operation, the controller 41 controls the brake control valve 20 to open to operate the auxiliary brake devices 26, 26. By applying an auxiliary braking force to the front wheels 5 and 5 in addition to the braking force of the rear wheels 6, the braking distance when the rear wheels 6 slip is shortened.

Further, since the operation delay of the auxiliary brake devices 26, 26 causes the braking distance to become long, as a measure for improving the operation response of the auxiliary brake devices 26, 26, the wheel cylinder is immediately input after the braking signal is input. The brake control valve 20 (solenoid valves 46, 47) is energized with a preparatory current of a predetermined value at which hydraulic pressure does not build up in 58. Specifically, by energizing the solenoid 46a to open the shut-off valve 46, the hydraulic pressure of the accumulator 55 is applied to the linear solenoid valve 47, and the solenoid 47a is energized with a predetermined value of electric current, so that the linear solenoid valve The spool of 47 is moved in advance to the position immediately before opening the valve. The process of step 120 in FIG. 7 is this preliminary energization process.

The map M in FIG. 6 is for determining the hydraulic pressure output from the linear solenoid valve 47 when the sliding speed ΔV exceeds a threshold value Vs which can be regarded as a slip of the rear wheel 6. The controller 41 has a sliding speed ΔV
The current value to be output to the solenoid 47a of the linear solenoid valve 47 is determined based on the hydraulic pressure (fluid pressure) determined by referring to the map M. When the slip velocity ΔV exceeds the threshold value Vs, the hydraulic pressure of the wheel cylinder 58 is set to the preset target hydraulic pressure “p”, and the slip velocity ΔV
Is set not to exceed the threshold value Vs, the hydraulic pressure is set to "0". When the hydraulic pressure value is "p", the current value Ip
Is energized, and when the hydraulic pressure value is "0", the preliminary current value Io is energized. The preliminary current Io is a minute current slightly smaller than the current value when the spool is located at the boundary between the valve closing and valve opening.

There are two reasons for supplying the preliminary current.
One is to substantially eliminate the movement time in the overlap region in which the spool of the linear solenoid valve 47 moves from the closed position to the valve open when not energized, and enhances the operation response of the auxiliary brake device 26. Another reason is that a minute current is supplied in advance to reduce a change in current when the solenoid 47a is supplied, and a rise delay of the current due to the inductance of the solenoid 47a is alleviated.

The target hydraulic pressure "p" suppresses the variation in the braking distance of the forklift 1 so that the braking distance of the forklift 1 does not change so much when the rear wheel 6 slips, compared to when the forklift 1 does not slip, and also causes the load collapse. It is set to a value that can provide an auxiliary braking force that does not result in sudden braking. The hydraulic pressure value (target hydraulic pressure) when the auxiliary brake device 26 is activated is not limited to the constant value p, but may be, for example, the slip speed Δ.
It is also possible to set at least one of V, vehicle speed V, baggage weight (load), and braking operation amount as a parameter so as to be variable according to the value of the parameter.

Next, the contents of the auxiliary brake control program will be described in detail with reference to the flowchart of FIG. First, in step (hereinafter referred to as “S”) 110, a brake switch braking signal indicating that the depression of the brake pedal 34 has been stopped from the brake switch 42 or an accelerator braking signal indicating that the accelerator lever 11 has been switched back is input. Judge whether or not. When inputting one of the braking signals, the main braking force is generated on the rear wheel 6. That is, when the brake switch braking signal is input, the main braking device 31 is mechanically actuated in conjunction with stopping the depression of the brake pedal 34, and the main braking force is applied to the rear wheels 6. On the other hand, when the accelerator braking signal is input, the drive motor 1
A regenerative brake is applied to 4 and a main braking force is applied to the rear wheels 6.

In S120, the brake control valve 20 is pre-energized. That is, the shutoff valve 46
Is opened by excitation, and the preliminary current Io is supplied to the linear solenoid valve 47 to the extent that the linear solenoid valve 47 is not opened.

In S130, the slip velocity ΔV is calculated. That is, first, the front wheel vehicle speed Vf is calculated based on the number of input pulses per unit time from the front wheel rotation speed sensor 28 on the outer wheel side of the turning which is determined according to the steering angle θ, and this is multiplied by the correction coefficient K (θ). A vehicle speed (driven wheel converted vehicle speed) V corresponding to the wheel position is calculated. Further, the rear wheel vehicle speed (driving wheel converted vehicle speed) Vr is calculated based on the number of input pulses per unit time from the rear wheel rotation speed sensor 35. Then, by taking the difference between them, the slip velocity ΔV = V-Vr is calculated.

In S140, slip determination is performed to determine whether the slip velocity ΔV exceeds the threshold value Vs. When the rear wheel 6 slips when ΔV> Vs holds, S15
When the rear wheels 6 are not slipping, the shift to 0 is made, and ΔV ≦ Vs is satisfied, the routine proceeds to S170.

In S150, the target hydraulic pressure value "p" at the time of slip detection is acquired by referring to the map M. S16
At 0, the operation of the auxiliary braking device 26 is commanded. That is, the current value Ip corresponding to the target hydraulic pressure value "p" obtained from the map M is supplied to the solenoid 47a of the linear solenoid valve 47. As a result, the brake control valve 20
Is supplied to the wheel cylinders 58, 58 to operate the auxiliary brake devices 26, 26, and the auxiliary braking force according to the hydraulic pressure value p is applied to the left and right front wheels 5, 5.

In S170, it is determined whether or not the vehicle is stopped. If the vehicle speed V becomes "0" or a stop vehicle speed Vc (> 0) that can be regarded as a stop, it is determined that the vehicle is stopped and S20
Move to 0. If the vehicle is not stopped, the process proceeds to S180.

In S180, it is determined whether the braking signal has been released. That is, it is determined whether the brake pedal 34 is stepped on again or the accelerator lever 11 is returned to the neutral position. If it is determined in S180 that the braking signal has been released, the process proceeds to S200.
If the braking signal is not released, the process proceeds to S190.

In S190, it is determined whether or not the auxiliary brake is being operated. If the auxiliary brake is operating, the process returns to S170, and if the auxiliary brake is not operating, S13
Return to 0.

In S200, the auxiliary braking device 2
6 and 26 are commanded to stop and the solenoids 46a and 47a of the solenoid valves 46 and 47 are de-energized. Therefore, when the accelerator lever 11 is operated in the direction opposite to the traveling direction or the brake operation for stopping the depression of the brake pedal 34 is performed while the forklift 1 is traveling, the controller 41 is operated.
Immediately after the input of the braking signal, the solenoids 46a and 47a are pre-energized to prepare for raising the hydraulic pressure of the wheel cylinders 58 and 58. As a result, the shut-off valve 46 opens, and the spool of the linear solenoid valve 47 waits at a position just before opening when the spool has almost finished moving in the overlap region.

Then, the rear wheel 6 is judged by the slip judgment (S140).
When the slip is detected (ΔV> Vs), a current Ip corresponding to the target hydraulic pressure p is supplied to the solenoid 47a, and the auxiliary brake devices 26, 26 are operated. Even if the slip of the rear wheel 6 is not detected by the slip determination, the slip determination is repeatedly executed during the braking until the vehicle is stopped or the braking signal is released, and if the slip of the rear wheel 6 is detected during the braking, that time is detected. Then, the current Ip is applied to the solenoid 47a,
The auxiliary braking devices 26, 26 are activated.

FIG. 8 is a graph comparing the rising response of hydraulic pressure, where the horizontal axis is the time and the vertical axis is the hydraulic pressure value. In the graph, the line X indicated by the chain line is “without pre-energization” and the line Y indicated by solid line is “when pre-energized” in the present embodiment.

When the pre-energization is not performed, even if the energization is started at the time of slip determination, the hydraulic pressure starts rising after a delay of the time during which the spool of the linear solenoid valve 47 moves in the overlap region. On the other hand, when there is preliminary energization, the hydraulic pressure rises immediately after the slip determination. That is, the responsiveness of the auxiliary braking device 26 can be accelerated by the moving time of the overlap region.

As can be seen from the graph of FIG. 8, the rising speed (slope) of the hydraulic pressure is relatively slow (slow slope) until reaching the hydraulic pressure value po, and becomes steep after passing the hydraulic pressure value po. . Therefore, at the rising line of the hydraulic pressure, there is a bending point A that bends at the hydraulic pressure po. The hydraulic pressure exhibits such rising behavior for the following reason.

FIG. 9 schematically shows a drum brake device used as the auxiliary brake device 26.
A certain amount of hydraulic pressure is required until the wheel cylinder 58 overcomes the biasing force of the spring 62 and starts moving, and this hydraulic pressure corresponds to the hydraulic pressure value pi in the graph of FIG. The wheel cylinder 58 starts to move by overcoming the urging force of the spring 62, and the lining 6 fixed to the outer peripheral surface of the shoe 63.
The brake does not work until 4 expands and moves the distance B until it hits the drum inner peripheral surface 65. The hydraulic pressure at which the lining 64 comes into contact with the inner peripheral surface 65 of the drum to start braking is the hydraulic pressure value po in the graph of FIG. 8, and the rising speed of the hydraulic pressure becomes relatively gentle until the hydraulic pressure po is reached. Since there is almost no physical movement amount from the break point A where the lining 64 hits the drum inner peripheral surface 65, the target hydraulic pressure "p"
Stand up on a steep slope.

Therefore, when the brake operation is performed while the forklift 1 is running and the braking signal is input, the preliminary current process (S120) is performed, the shutoff valve 46 is excited and opened, and the linear solenoid valve 47 is opened. The preliminary current Io is supplied to move the overlap region to a position where the spool is not closed in advance. When it is determined that the slip occurs in the subsequent determination process (S140),
As shown in the graph, the hydraulic pressure rises from that judgment. Therefore, the auxiliary braking devices 26, 26 are actuated with almost no response delay after the slip detection of the rear wheels 6, and the auxiliary braking force is immediately applied to the front wheels 5, 5. Therefore, the braking distance of the vehicle is shortened.

For example, even if the rear wheel 6 whose reach is reduced in the loaded state and the wheel load is reduced is located on a wet road surface or an icy road surface and the rear wheel 6 slips, it is determined to be slip. Almost at the same time, the auxiliary braking devices 26, 26 are actuated, and the auxiliary braking is applied to the front wheels 5, 5 whose wheel weight is large, so that the braking distance can be kept short. In addition, the rear wheel 6 which is displaced to the left from the center of the vehicle width
Since a side force acts on the vehicle, a back swinging phenomenon occurs in which the rear part of the vehicle body flows in the direction of the arrow in Fig. 4 when slipping.
Since the auxiliary braking force applied to the front wheels 5 and 5 acts in a direction to cancel the turning moment of the vehicle body due to the side force,
The amount of swinging at the rear of the vehicle body can be kept small.

Therefore, according to this embodiment, the following effects can be obtained. (1) Even if the rear wheel 6 slips when the accelerator lever 17 or the brake pedal 34 performs a brake operation on a wet road surface or an icy road surface, the auxiliary brake device 26,
Since 26 is actuated and the auxiliary braking force is applied to the front wheels 5 and 5, the braking distance of the forklift 1 can be suppressed to be short, and the amount of swinging of the vehicle body due to the slip of the rear wheels 6 can be suppressed to be small.

(2) Pre-energization processing is executed almost at the same time as the braking signal is input, the shut-off valve 46 is opened, and the spool of the linear solenoid valve 47 is moved to a position in the overlap region immediately before opening. Since it is kept on standby, the auxiliary brake devices 26, 26 are activated immediately after the slip of the rear wheel 6 is judged, and the operation responsiveness thereof can be enhanced. Therefore, after the rear wheel 6 slips, the auxiliary brake is applied with almost no response delay, the delay of the auxiliary brake at the time of high vehicle speed when the slip starts can be reduced, and the braking distance can be effectively shortened.

(3) Since the preliminary energization is executed only when the brake operation is performed, the power consumption by the preliminary energization can be small. (4) Since the accumulator 55 is used as the hydraulic pressure source of the brake control valve 20, there is no concern about the delay in the rise of the hydraulic pressure when starting the electric motor, which is a problem in the system in which the electric hydraulic pump is used as the direct hydraulic pressure source. Brake device 2
It is possible to improve the operational response of 6, 26.

(Second Embodiment) Next, a second embodiment will be described. This embodiment is an example in which the operation response of the auxiliary brake device is further improved, and is characterized by a method of supplying a preliminary current. The same components as those in the first embodiment are designated by the same reference numerals, detailed description thereof will be omitted, and only different points will be described.

The structure of the forklift 1 is the same as that of the first embodiment (FIGS. 1 to 5), and the auxiliary brake devices 26, 26 attached to the front wheels 5, 5 and the hydraulic system for controlling the operation of the auxiliary brake devices 26, 26. And various electric circuits. Only the processing contents executed by the controller 41 differ from the first embodiment. Hereinafter, the processing content of the controller 41 will be described in detail.

The controller 41 energizes the solenoid 47a of the linear solenoid valve 47 with a preliminary current (small current) Io when the forklift 1 is keyed on. This current value Io is the same value as in the first embodiment. During operation of the forklift 1, a small current Io is constantly applied to the solenoid 47a, and the spool of the linear solenoid valve 47 is held at a position just before opening the valve, which has almost moved in the overlap region.

In the first embodiment described above, although the movement time for the spool to move in the overlap area can be almost eliminated,
The hydraulic pressure must be raised from "0" from the time of slip determination, and the expanded lining 64 causes the drum inner peripheral surface 65 to rise.
The auxiliary brake device 26 is used for the time required to rise to the hydraulic pressure "po" at which the brake actually starts to work.
Will be delayed. In particular, in the range of the hydraulic pressure "0" to "po", the rising speed of the hydraulic pressure is relatively slow, so that it takes a long time to rise, which is a major cause of the delay in the operation of the auxiliary brake device 26.

Therefore, in this embodiment, in the process of rising the hydraulic pressure after the slip determination, the rising speed is in the slow region (0
~ Po) can be reduced as much as possible, the start timing of the hydraulic pressure is set before the slip determination. Specifically, the hydraulic pressure starts to rise at the same time as the input of the braking signal. That is, when a braking signal is input, the shut-off valve 46 is excited to open the valve, and the solenoid 47a is actuated at a current level (a current value I corresponding to the target hydraulic pressure "p" in this example).
energize p). That is, in the present embodiment, the preliminary energization before the determination (preliminary current energization processing) includes the energization processing of the minute current Io which is constantly energized during the vehicle operation and the startup processing of energizing the current value Ip from the time when the braking operation is detected. It is done in two stages.

FIG. 11 is a graph comparing the rising characteristics of hydraulic pressure. In this graph, line X is "no pre-energization", line Y is "always energization (micro-current application)", line Z
Represents the "always energized + start-up process" in this embodiment. In order to eliminate the region in which the rising speed is slow, it is necessary to raise at least the hydraulic pressure value po (break point A) at which the lining 64 contacts the drum inner peripheral surface 65 at the time of determination.

In the present embodiment, when the slip determination result is issued and the command for the auxiliary brake is issued (at the time of the determination in the same graph), the hydraulic pressure just slightly exceeds the break point A and the actual braking operation starts. The value ps within the range is set. However, the set hydraulic pressure ps to be reached at the time of slip determination (energization command) is effective in the actual operation initial region belonging to the lower half region of the actual operation region, but is not limited to this and the lining 64 is expanded. From the beginning to the time when it hits the inner surface 65 of the drum.
<Ps ≦ po) may be satisfied, and even in this case, it is possible to reduce the region where the rising speed is slow, which is effective. The actual operating range here does not mean that the target hydraulic pressure p is the upper limit, but the entire range in which the maximum hydraulic pressure pmax (maximum auxiliary brake capacity) is effective, and therefore the actual operating initial stage. The range refers to a range from po to (po + pmax) / 2.

In this example, the set hydraulic pressure ps is set in the actual operation initial region to increase the hydraulic pressure to the extent that the brake is applied a little at the time of slip determination, but this is for the following reason.

(1) This is because the hydraulic responsiveness at the time of slip determination can be made as high as possible to improve the operation response of the auxiliary brake. Moreover, the hydraulic pressure po at the break point A, which has finished the empty working range where the rising speed of the hydraulic pressure is slow, has already been reached, and since there is almost no physical movement from the break point A, the target hydraulic pressure "p" is immediately reached. Stand up to. (2) When the non-slip judgment is made and the command to stop the energization of the start-up is issued, the brake is already in effect, but the time from the input of the braking signal to the judgment result is very short and the auxiliary brake is applied. Because it does not affect the speed of the vehicle in a moment,
The human sense does not notice that the brakes are applied.

As described in the reason (2), since the auxiliary brake is applied only for a moment during non-slip, the set hydraulic pressure ps
May be the actual final operating range or the target hydraulic pressure “p”. Further, the target current value at the time of energization for start-up is not limited to the current value Ip corresponding to the target hydraulic pressure "p", and if the set hydraulic pressure ps can be obtained at the time of the normal energization command after the slip determination, the start-up energization The timing can be set as appropriate in consideration of the timing between the command timing and the determination timing. Further, the start-up energization start timing is not limited to be the same as the braking operation detection, and may be appropriately set such that it is slightly delayed from the braking operation detection time for timing.

Further, the controller 41 stores the map M shown in FIG. 6 and the auxiliary brake control program shown in FIG. 10 in the memory 41a. Next, the contents of the auxiliary brake control program will be described in detail with reference to the flowchart of FIG.

First, in S310, a brake switch braking signal indicating that the depression operation of the brake pedal 34 is stopped from the brake switch 42, or the accelerator lever 11 is pressed.
It is determined whether or not an accelerator braking signal indicating that the switch back operation has been performed is input. When any one of the braking signals is input, the main braking device 31 is actuated or the drive motor 14 is regeneratively braked to apply the main braking force to the rear wheels 6.

In step S320, the brake control valve 20 is commanded to start up and energize (startup process). That is, the shut-off valve 46 is opened by excitation, and the linear solenoid valve 47 is supplied with a current Ip of a predetermined value corresponding to a hydraulic pressure value (for example, a target hydraulic pressure "p") in a braking range.

In S330, the slip velocity ΔV is calculated. This calculation process is S in the first embodiment.
This is the same as the processing content of 130. In S340,
It is determined whether the slip velocity ΔV exceeds the threshold value Vs. When the rear wheel 6 slips when ΔV> Vs holds, S35
When the rear wheel 6 is not slipping, the shift to 0 is made, and ΔV ≦ Vs is satisfied, the routine proceeds to S370.

In S350, the target hydraulic pressure value "p" is acquired by referring to the map M. In S360, the operation of the auxiliary brake device 26 is instructed. That is, the solenoid 47a of the linear solenoid valve 47 is energized with a current value Ip corresponding to the target hydraulic pressure value "p" obtained from the map M. As shown in FIG. 11, the hydraulic pressure at the time when the slip determination result is generated and the auxiliary brake operation command is issued by the startup energization process in S320, the hydraulic pressure p at which the brake is already applied is p.
It has risen to s, and hydraulic pressure rise by the auxiliary brake operation command starts from point S. Therefore, it suffices to increase the remaining amount of hydraulic pressure from point S to the target hydraulic pressure "p". As a result, the hydraulic pressure output from the brake control valve 20 to the wheel cylinder 58 immediately reaches the target hydraulic pressure value "p", and the auxiliary braking device 26 immediately generates the auxiliary braking force corresponding to the hydraulic pressure value "p". , 5 are added.

In S370, the stop of the energization of the current Ip by the start-up energization process is instructed. As shown in FIG. 11, when the slip determination result is obtained by the startup energization process (S320) (the auxiliary brake operation command time)
At this point, the hydraulic pressure has already risen to the level at which the brake is applied, and the current flow decreases from the current Ip to the minute current Io due to the stop of the current flow, and the hydraulic pressure drops from the hydraulic pressure ps at point S to "0". At this time, since the time from when the braking signal is input to when the slip determination result is obtained is very short, the auxiliary brake takes a moment, but it does not affect the speed of the vehicle. Therefore, the human sense does not notice that the brake is applied.

In S380, it is determined whether or not the vehicle is stopped. That is, when the vehicle speed V becomes "0" or the stop vehicle speed Vc (> 0) which can be regarded as a stop, it is determined that the vehicle is stopped, and the process proceeds to S410. If the vehicle is not stopped, S
Move to 390.

In S390, it is determined whether the braking signal has been released. That is, it is determined whether the brake pedal 34 is stepped on again or the accelerator lever 11 is returned to the neutral position. Then, if it is determined in S390 that the braking signal is released, the process proceeds to S410.
If the braking signal is not released, the process proceeds to S400.

In S400, it is determined whether or not the auxiliary brake is in operation. If the auxiliary brake is operating, the process returns to S380, and if the auxiliary brake is not operating, S33
Return to 0.

In S410, the auxiliary brake device 2
6 and 26 are commanded to stop and the solenoids 46a and 47a of the solenoid valves 46 and 47 are de-energized. However, what is stopped here is only the start-up energization, and the solenoid 47a
The energization of the minute electric current Io is maintained.

After the brake operation is started, the slip judgment (S3
Even if the slip of the rear wheels 6 is not detected in 40), the start-up energization process (S320), the slip determination process (S340), and the start-up energization stop process (S370) are performed during braking until the vehicle is stopped or the braking signal is released. ) Is repeatedly executed. Therefore, regardless of whether the braking operation is started immediately or during braking, the hydraulic pressure has already risen to a value at which the braking is effective when the slip of the rear wheel 6 is detected. The auxiliary braking force is immediately applied to the front wheels 5 and 5 with almost no response delay.

For example, when the rear wheel 6 which reaches out due to a load condition and the wheel load is small is located on a wet road surface or an icy road surface and the rear wheel 6 slips, the auxiliary brake devices 26, 26 are used. The braking distance can be suppressed to be relatively short by activating. Further, the tail swing amount that the rear portion of the vehicle body flows in the direction of the arrow in FIG. 4 due to the slip of the rear wheel 6 is suppressed to be small.

Here, the effect of the operation response of the auxiliary brake device 26 will be described. As shown in the graph of FIG. 11, when the pre-energization is not performed (line X), the hydraulic pressure rises with a delay of the spool overlap region movement time from the determination,
Moreover, since it passes through a region where the rising speed is slow, it takes time before the auxiliary brake actually starts to operate, and the operation delay of the auxiliary brake device 26 from the time of determination is relatively large.

When the pre-energization (micro-current application) is applied (line Y), the spool has moved to the position just before the valve is opened, which has almost finished moving in the overlap area at the time of determination, and therefore immediately after the determination. Although the hydraulic pressure rises, as in the first embodiment, the hydraulic pressure rises from "0" and passes through a region where the rising speed is slow. Therefore, it takes some time from the time of determination until the auxiliary brake works.

On the other hand, "always energized + startup process"
In the present embodiment which adopts, as shown by the line Z, the spool is waiting at the position just before the valve is opened, which has almost finished moving in the overlap area, before the braking operation is detected. The rise of hydraulic pressure is started.
At the time of slip determination, the hydraulic pressure has already risen until the brake has begun to operate, exceeding the break point A, so it is sufficient to rise by the remaining half of the hydraulic pressure up to the target hydraulic pressure "p".
When an auxiliary brake operation command is issued during the determination, the target hydraulic pressure "p" is instantly reached. Therefore, the auxiliary brake device 26
The actuation response of is much higher than that of the first embodiment. In the present embodiment, the responsiveness of the auxiliary brake device 26 is accelerated by about 0.1 seconds as compared with the case without the pre-energization. About 0.1 seconds is about 5% when the total braking time is about 2 seconds, but it is possible to avoid the delay in auxiliary brake operation when the vehicle speed is the highest at the start of braking, so it is quite effective in shortening the braking distance. .

As described in detail above, according to this embodiment,
In addition to the same effects (1) and (4) as those of the first embodiment, the following effects can be obtained. (5) Solenoid 47a during operation of forklift 1
Preliminary energization, in which a small current is constantly applied, and start-up processing, which starts the energization when a braking signal is input, are adopted. Therefore, when the judgment result comes out and the target current is commanded, it has already risen to the current value at which the brake starts to operate,
Instantly rises to the target current. Therefore, the target braking force can be applied to the front wheels 5 and 5 instantly after the determination. Therefore, the auxiliary brakes are applied to the front wheels 5 and 5 immediately after the slip occurs, and the braking distance can be effectively shortened with almost no braking delay.

(6) At the time of judgment, the hydraulic pressure has risen by the time the brakes start to work, and since the hydraulic pressure po at the break point, which is the end point of the slow rising region, has already passed, it is necessary to rise to the target pressure. The time is very short. In addition, when the judgment is made, the hydraulic pressure rises to the value until the brake starts to work, but when it is judged as non-slip and the power supply is stopped, the brake is applied only for a moment and it does not affect the vehicle speed, so the driver feels uncomfortable. I don't feel it.

(7) While the forklift 1 is in operation, pre-energization is always performed to the solenoid 47a to the extent that the spool does not open, but since it is a minute current, power consumption is relatively small.

The embodiment is not limited to the above, and may be implemented in the following modes, for example. The determination process for determining whether or not it is necessary to assist the braking of the driving wheels (the determination target of the determination unit) is not limited to slip determination. For example, the setting may be such that the auxiliary brake device is activated when the vehicle speed is high, and the determination processing may be vehicle speed determination that determines whether or not the vehicle speed is high. Also,
The auxiliary brake device may be set to operate when the load is heavy, and the determination process may be load determination that determines whether or not the load is heavy. Further, the determination processing may be performed using two or more of the three parameters of slip, vehicle speed, and load as parameters to determine whether or not the auxiliary brake is required. However, it is preferable that one of the parameters includes slip. Even when these determination processes are adopted, the braking distance of the vehicle can be shortened and the variation in the braking distance can be reduced.

With the control method adopted in the second embodiment, the pre-energization (the application of the minute current) before the input of the braking signal is abolished, and only the start-up process from the input of the braking signal is executed as shown in FIG. Good. Also in this case, when the determination is made, the hydraulic pressure has already risen to the region where the hydraulic pressure is generated (for example, the operation preparation region (0 <hydraulic pressure pi) or the empty operating region (pi <hydraulic pressure ≦ po) before the start of the operation), so the auxiliary The responsiveness of the braking device 26 is enhanced, which is effective in shortening the braking distance. Also, depending on the characteristics of the auxiliary brake device, the hydraulic pressure (> po) at which the brake is applied at the time of determination can be increased even by the startup process alone. With this configuration, power consumption can be suppressed by eliminating the pre-energization while the vehicle is operating, which is useful for saving battery power.

○ In the second embodiment, the set hydraulic pressure p
s is not limited to the empty operation area or the actual operation initial area. For example, it may be a value within the range of 0 <ps ≦ pi. Even in this case, since the spool of the linear solenoid valve 47 is in the valve opening range and the hydraulic pressure has already been generated at the time of determination, it is possible to enhance the operation responsiveness of the auxiliary brake device 26 as compared with the configuration of the first embodiment. it can. Further, the target current value in the startup energization process can be appropriately set to a current value corresponding to the valve opening range of the linear solenoid valve (however, the current value is equal to or more than the current value corresponding to the set hydraulic pressure ps).

In the second embodiment, the pre-energization to the extent that the spool to the linear solenoid valve 47 does not open is not limited to being constant during vehicle operation. For example, in the low vehicle speed range where the vehicle speed is below a certain value, the auxiliary brake device shall not be activated, and in the vehicle speed range where the vehicle speed may exceed the certain value and the auxiliary brake may be applied, pre-energization to the extent that the spool does not open To execute. According to this configuration, the power consumption can be reduced and the battery power can be saved as compared with the case where the backup current is always supplied.

In the second embodiment, at the time of determination, the hydraulic pressure may be stable in a steady state rather than in a transitional period during which it is rising. In this case, if the target current value of the start-up process is set to a value corresponding to the idle operation range or the actual operation initial range of the auxiliary braking device 26, whether the auxiliary braking is applied or not
Since it takes a very short time with a weak force, it does not affect the vehicle speed and there is no particular problem.

In the second embodiment, when it takes time to obtain the determination processing result after the braking signal is input,
It is also possible to set the timing to intentionally delay the current start-up command timing from the braking signal input time so that the predetermined hydraulic pressure rises at the determination time.

In the first embodiment, it is possible to employ a configuration in which the linear solenoid valve 47 is pre-energized at all times during operation of the forklift 1. In each embodiment, the determination process of whether or not the auxiliary braking is necessary, such as the slip determination, is not limited to be performed when the braking operation is detected, and may be performed at least when the main braking device is operated. For example, the determination process may be executed at all times during vehicle driving (key-on) (however,
The operation command of the auxiliary braking device is limited to when braking operation is detected).

The electromagnetic valve means is composed of two electromagnetic valves 46, 4
It is not limited to be composed of 7. For example, the shut-off valve 46 may be eliminated and only the linear solenoid valve 47 may be provided, and preliminary energization may be performed only by applying a minute current to the linear solenoid valve 47. Further, the hydraulic circuit of the brake control valve may be changed, and the electromagnetic valve means may be a combination of a plurality of electromagnetic on-off valves.

The hydraulic power source for supplying pressure oil to the brake control valve is not limited to the cargo handling pump. For example, a dedicated pump and electric motor dedicated to the brake valve unit may be used. In this case, the brake control valve 20 may have a structure in which the hydraulic pressure is supplied by sequentially rotating a pump dedicated to the valve, for example, instead of the structure in which the hydraulic pressure is accumulated by the accumulator.

A brake device of any type can be adopted as the auxiliary brake device 26 and the main brake device 31.
For example, a disc brake device can be used as the auxiliary brake device 26. A drum brake device can be adopted as the main brake device 31.

The forklift 1 is not limited to the structure in which the front wheels 5 are the driven wheels and the rear wheels 6 are the driving wheels. For example, the front wheels may be driving wheels and the rear wheels may be driven wheels. In this case, the front wheels are equipped with the main braking device and the rear wheels are equipped with the auxiliary braking device. Further, it may be a three-wheel drive forklift in which both the front wheels 5 and the rear wheels 6 are drive wheels. In this case, in the slip determination, the acceleration (deceleration) of the rear wheel 6 is obtained, the slip is determined when the acceleration exceeds a threshold value that can be regarded as the slip, and the auxiliary brake device 26 is operated when the determination result is the slip. Activate.

○ Industrial vehicles are reach type forklifts 1
However, the present invention is not limited to this, and can be applied to other types of forklifts such as a counterbalance type and an order picking type. It can also be applied to unmanned forklifts. In addition, when the wheel on which the main braking is applied slips, the auxiliary braking force may be applied to the wheels on the front and rear sides of the wheel on which the main braking is applied, in an industrial vehicle other than the forklift.

The technical ideas other than the claims that can be understood from the embodiment and the other examples will be described below. (1) In the invention of claim 2, the control means includes a detection means for detecting a braking operation of an operation means for operating the main braking means, and the control means has a braking operation of the operation means by the detection means. Is detected, a current is applied to the electromagnetic valve means to such an extent that the spool does not open. According to this configuration, the pre-energization is performed only when the operating means is braked, so that the power consumption due to the pre-energization can be suppressed to be small.

(2) In the invention of claim 1 or 2, the determining means is a drive wheel when the operating means for operating the main braking means for braking the front wheel or the rear wheel, which is the drive wheel, is braked. It is determined whether or not it is necessary to assist the braking of.

(3) In any one of claims 1 to 8 , the hydraulic source of the electromagnetic valve means is a pressure accumulator (55) for accumulating the pressure oil input from the hydraulic pump. According to this configuration, the pressure accumulator serves as a hydraulic pressure source, and the accumulated pressure oil is adjusted to a predetermined hydraulic pressure through the electromagnetic valve means and is immediately output, so that, for example, an industrial vehicle is a battery vehicle and a cargo handling pump is an electric vehicle. Even if the motor is driven only when necessary, the quick response of the auxiliary braking means can be obtained.

(4) In the invention according to any one of claims 1 to 8 , the electromagnetic valve means is an electromagnetic proportional pressure adjusting valve (4) for adjusting the hydraulic pressure output to the auxiliary braking means.
7), and the current value is controlled by the control means.

(5) In claim 4, the control means always supplies a current to the electromagnetic valve means to such an extent that the spool does not open while the industrial vehicle is in a key-on operation.

[0116]

As described in detail above, according to the invention described in claims 1 to 8 , when it is judged that the auxiliary braking is necessary at the time of braking, the auxiliary braking means is actuated so as to be opposite to the front and rear wheels. Since the auxiliary braking force is applied to the wheels on the side, the braking distance can be kept short, and the pre-energization of the electromagnetic valve means before the determination can enhance the operation response of the auxiliary braking means, thus reducing the braking distance of the vehicle. Can be kept short.

According to the invention described in claims 4 to 8 , the solenoid valve means is energized before the braking operation so that the solenoid valve means is not opened, and when the braking operation is detected, the solenoid valve means is opened. Since the corresponding energization is started to start the hydraulic pressure before the determination,
The operation response of the auxiliary braking means can be further enhanced, and the braking distance of the vehicle can be more effectively suppressed to be short.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a forklift according to a first embodiment.

FIG. 2 is a hydraulic circuit diagram of a cargo handling system and a brake system.

FIG. 3 is a side view of the forklift.

FIG. 4 is a plan sectional view of a forklift.

FIG. 5 is a rear view showing the drive mechanism for the rear wheels.

FIG. 6 is a map used for auxiliary brake control.

FIG. 7 is a flowchart showing an auxiliary brake control program.

FIG. 8 is a graph showing rising characteristics of hydraulic pressure.

FIG. 9 is a schematic diagram showing an auxiliary brake device.

FIG. 10 is a flowchart showing an auxiliary brake control program in the second embodiment.

FIG. 11 is a graph showing rising characteristics of hydraulic pressure.

FIG. 12 is a graph showing rising characteristics of hydraulic pressure in another example.

FIG. 13 is a side view of a conventional forklift truck.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reach type forklift truck as an industrial vehicle, 5 ... Front wheel, 6 ... Rear wheel (driving wheel), 11 ... Accelerator lever as an operating means, 14 ... Drive motor constituting main braking means, 20 ... Brake control device Comprising brake control valve, 21 ... Mast device as cargo handling device,
26 ... Auxiliary braking device as auxiliary braking means, 31 ...
Disc brake device as main braking means, 34 ... Brake pedal as operating means, 35, 36 ... Rotation speed sensor constituting detection means, 40 ... Brake switch as detection means, 41 ... Controller as determination means and control means , 43 ... An accelerator sensor which constitutes a detecting means,
46 ... Shut-off valve constituting electromagnetic valve means, 47 ...
A linear solenoid valve that constitutes electromagnetic valve means, 48 ... A motor drive circuit that constitutes main braking means.

Claims (8)

(57) [Claims] 1. A determination means for determining whether or not it is necessary to assist braking of a driving wheel when a main braking means for braking a front wheel or a rear wheel, which is a driving wheel, is activated; Hydraulic auxiliary braking means for applying an auxiliary braking force to the opposite wheel, electromagnetic valve means for adjusting hydraulic pressure output to the auxiliary braking means for operation, and before the determination by the determination means, And a control means for supplying a current for operating the auxiliary braking means to the electromagnetic valve means when a preliminary current is supplied to the electromagnetic valve means and the braking assistance is determined to be required by the determination. Brake control device for industrial vehicles. 2. The brake control device for an industrial vehicle according to claim 1, wherein the control means energizes the electromagnetic valve means with a current that does not open before the determination by the determination means. 3. A detection means for detecting a braking operation of an operating means for operating the main braking means, wherein the control means detects the braking operation of the operating means by the detecting means. When the solenoid valve means is energized with a current having a value corresponding to the valve opening range to start the output of the hydraulic pressure, and after the start of the hydraulic pressure is started, the determination means determines that auxiliary braking is required, When a current corresponding to the target hydraulic pressure is applied to the electromagnetic valve means, and when the determination means determines that auxiliary braking is not required, the energization for raising the hydraulic pressure to the electromagnetic valve means is stopped. The brake control device for an industrial vehicle according to claim 1. 4. The industrial vehicle according to claim 3, wherein the control means applies a current to the electromagnetic valve means in advance so that the electromagnetic valve means is not opened before the detection means detects the braking operation of the operation means. Brake control device in. 5. The brake of the auxiliary braking means is activated when the hydraulic pressure output from the electromagnetic valve means and rising is commanded to energize the electromagnetic valve means when the determination result of the determination means is present. The brake control device for an industrial vehicle according to claim 3 or 4, which is set so as to reach a value corresponding to an empty operation range before starting or an actual operation initial range where braking starts to work. 6. The hydraulic pressure that has risen at the time when the determination result is issued and a command for energization is issued so that the hydraulic pressure rises to a value corresponding to an actual operation initial range in which the brake of the auxiliary braking means starts to work. The brake control device in the industrial vehicle according to 5. 7. The determination means detects a slip of a wheel to which a braking force is applied by the main braking means, and when the slip is detected, it is determined that auxiliary braking is necessary.
The brake control device in the industrial vehicle as described in any one of Claims 6-6. 8. An industrial vehicle is braked by the main braking means.
The driving wheel to which force is applied is the rear wheel, and the auxiliary braking means is used.
The wheel to which the braking force is applied is the front wheel, and
Reach type with a stand mounted on the front side of the car body so that it can move back and forth.
The brake control device for an industrial vehicle according to any one of claims 1 to 7, which is an forklift .