JP2001335299A - Hydraulic control device for braking industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic control device for braking which can effectively reduce the braking distance of a vehicle by the automatic braking control independent from a braking operation, and is suitable for the automatic braking control even with a factor of increasing the braking distance such as a slip of a braked wheel during the braking operation. SOLUTION: A control unit 26 actuates auxiliary brakes 32 and 32 provided on right and left wheels via a brake valve unit 31 when the slip of rear wheels (driving wheels) is detected. The brake valve unit 31 comprises a pressure reducing valve 70, a non-return valve 71, an accumulator 69, two solenoid valves 73 and 74, and a pressure sensor 75, and a hydraulic pressure source is formed of the accumulator 69 for accumulating the pressure oil fed from a pump 28 for cargo handling operation. When the slip is detected, one set of the solenoid valves 73 and 74 are opening/closing-controlled by the control unit 26 so that the detected hydraulic pressure by the pressure sensor 75 is the set value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a braking system of an industrial vehicle, which is used in an industrial vehicle such as a forklift and is used for controlling the hydraulic pressure of a brake system effective for reducing a braking distance. .

[0002]

2. Description of the Related Art In recent years, automobiles have adopted antilock brake system (ABS) control. For example, A
In the BS control, when lock of a driving wheel is detected at the time of operation of a brake pedal, control is performed to release the brake hydraulic pressure and reduce the brake force from a value corresponding to the brake operation force. Conventionally, ABS control and the like have not been adopted in industrial vehicles such as forklifts. However, it is desirable to employ automatic brake pressure adjustment control such as ABS control in order to realize stable cargo handling traveling.

For example, Japanese Patent Application Laid-Open No. 9-20229 discloses that
FIG. 10 discloses a brake system (hydraulic circuit) for a vehicle that can cope with ABS control. This brake system controls a brake hydraulic pressure according to operation of a brake pedal.

The brake system includes a master cylinder 102 for generating a hydraulic pressure according to an operation force of a brake pedal 101, a wheel cylinder 104 for operating a brake device 103, a variable displacement pump 105, an electric motor 106 for driving a pump, and an accumulator 107. , Check valve 10
8, a constant flow control valve 109, an electromagnetic variable throttle (linear solenoid) 110, two electromagnetic on-off valves 111 and 112, and the like.

[0005] The variable displacement pump 105 functions as a high pressure source for generating a brake oil pressure in the wheel cylinder 104. When the variable displacement pump 105 is normally generating an appropriate discharge pressure, the electromagnetic on-off valve 111 is in a shut-off state, and the electromagnetic on-off valve 112 is in a conductive state. Accumulator 10
7, a hydraulic pressure equal to the valve opening pressure of the check valve 108 is stored.

When the depression of the brake pedal 101 is detected by the switch 113, the capacity of the variable displacement pump 105 is increased, and when the discharge pressure reaches the opening pressure of the check valve 108, the displacement is made constant through the constant flow rate valve 109. A flow of hydraulic oil is supplied to the wheel cylinder 104 side. The ECU (electronic control unit) 114 detects the oil pressure of the master cylinder 102 and the oil pressure of the wheel cylinder 104 using two pressure sensors 11.
It grasps based on the detection value from 5,116. And
By comparing the detected oil pressure values, the electromagnetic variable throttle 110 located between the wheel cylinder 104 and the reservoir tank 117 is compared.
Is controlled so that the wheel cylinder pressure becomes a multiplied value of the master cylinder pressure and the amplification ratio stored in advance. For example, when a tire slip is detected, the electromagnetic variable throttle 1
10 is controlled so as to reduce the brake pressure.

[0007]

For example, in an industrial vehicle such as a forklift, the wheel load (wheel pressure) of the drive wheel changes depending on the cargo handling state such as the presence or absence of a load. In other words, in a loaded state in which a load is loaded on a fork, the center of gravity of the vehicle shifts forward, so that the wheel load of the rear wheel becomes relatively small. growing. Especially in reach-type forklifts, when the brake is operated, the driving wheel that is braked is the rear wheel, the load on the rear wheel is small, and when the mast device reaches out and the load is located ahead, the wheel weight of the rear wheel is even smaller. Become. For this reason, in a reach-type forklift or the like, particularly when a brake operation is performed on a wet road surface or a frozen road surface in a freezer warehouse in a loaded state, slipping of the drive wheels (rear wheels) is relatively likely to occur.

In order to prevent this, if the above-mentioned brake system is equipped and ABS control is adopted, the maximum braking force can be obtained in a range where the vehicle is not locked by controlling the brake hydraulic pressure to be released when a tire lock is detected. But,
When the drive wheel slips due to brake operation on a wet or frozen road surface, the coefficient of friction between the road surface and the tire is quite small, and the braking force applied to the drive wheel can be kept very low by ABS control, so braking on a dry road surface There has been a problem that the braking distance of the vehicle is longer than that at the time of operation. Especially when loading, the gross vehicle weight is heavy, the inertia force at the time of braking is large, and the braking distance tends to be long.Because the wheel weight of the tire is also small, the braking distance when braking on a wet road surface or frozen road surface is reduced. Elongation tended to be relatively long.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a brake operation which is effective even when there is a factor such as a slip of a braking wheel which increases a braking distance when the braking operation is performed. An object of the present invention is to provide a brake hydraulic control device for an industrial vehicle that can effectively shorten the braking distance of a vehicle by independent automatic brake control and that is suitable for hydraulic control for automatic brake control.

[0010]

According to a first aspect of the present invention, an operating means for operating a main braking means for braking a front wheel or a rear wheel, which is a driving wheel, is provided. When operated, it is determined that it is necessary to assist the braking of the drive wheel. When the brake is operated by a hydraulic auxiliary braking unit that applies an auxiliary braking force to the wheel opposite to the front and rear of the drive wheel. A hydraulic control device, wherein an input port to which pressure oil is input from a hydraulic pump, an output port to output pressure oil for operating the auxiliary braking means, and a braking force of the auxiliary braking means are preset. And a hydraulic circuit having electromagnetic valve means for performing hydraulic control for outputting a hydraulic pressure corresponding to the value from an output port.

According to this configuration, when it is determined that the braking of the drive wheels needs to be assisted when the operating means is braked, the electromagnetic valve means in the hydraulic circuit is controlled and the auxiliary braking means is controlled. A hydraulic pressure according to a preset value as the braking force is output from the output port. As a result, the hydraulic auxiliary braking means is actuated, and an auxiliary braking force is applied to the drive wheel on which main braking has been applied and the front and rear opposite wheels. For example, the braking distance when the vehicle slips due to the slip of the drive wheel is reduced.

According to a second aspect of the present invention, in the first aspect of the present invention, the driving wheel to which the braking by the main braking means is applied is one of a front wheel and a rear wheel of a cargo handling device mounted on a vehicle. The wheel on the side where the wheel load becomes smaller as the loading load is larger, and the wheel to which the auxiliary braking by the auxiliary braking means is applied is the wheel on the side where the wheel load becomes larger as the loading load on the cargo handling device is larger. The gist is that there is.

According to this configuration, when the loading load of the cargo handling device is large, the total weight of the vehicle is heavy, and the braking distance tends to be long due to inertia. Therefore, the braking distance tends to be long. However, since the auxiliary braking is applied to the wheel on the side where the wheel load increases (increases) due to the load, the braking distance can be effectively shortened even when the braking distance is likely to be long, such as during loading.

According to a third aspect of the present invention, there is provided the first or second aspect.
In the invention described in (1), the hydraulic circuit is provided with a pressure sensor that detects a hydraulic pressure output to the auxiliary braking means, and the electromagnetic valve means includes a pair of electromagnetic valves provided upstream and downstream of the output port. An on-off valve, wherein the pair of electromagnetic on-off valves includes a supply electromagnetic on-off valve for supplying pressure oil from a hydraulic pressure source to the output port side, and a discharge electromagnetic valve for discharging the pressure oil supplied to the output port side. The gist of the invention is that the opening / closing valve is controlled to be opened and closed so as to output a preset oil pressure from the output port based on a detection value of the pressure sensor when the auxiliary braking means is operated.

According to this configuration, since the pressure is controlled using a pair of the electromagnetic on-off valve and the pressure sensor, a complicated and expensive electromagnetic valve such as an electromagnetic proportional pressure regulating valve (such as a linear solenoid valve) can be used. It can be realized with a relatively simple configuration without using it.

The invention described in claim 4 is the first or second invention.
In the invention described in the above, the electromagnetic valve means includes an electromagnetic proportional pressure adjusting valve that adjusts a hydraulic pressure output to the auxiliary braking means, and the electromagnetic proportional pressure adjusting valve is operated when the auxiliary braking means is operated. The gist is that the current value is controlled so that a preset oil pressure is output from the output port.

According to this configuration, since the electromagnetic proportional pressure regulating valve is used, the number of components required for pressure regulation is relatively small, and the apparatus can be downsized. According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the industrial vehicle includes a cargo handling pump that supplies pressure oil for operating a cargo handling device provided in the vehicle. ,
An electric motor for driving the cargo pump; and a hydraulic oil supplied from the cargo pump to the input port of the hydraulic circuit.

According to this configuration, the cargo pump and the electric motor for the cargo handling device are diverted as the hydraulic supply source for operating the hydraulic auxiliary braking means. Therefore, the pump and the motor are provided exclusively for the auxiliary braking. It is not necessary, and it is difficult to increase the size of the industrial vehicle.

According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, in the industrial vehicle, a rear wheel as a driving wheel is braked by the main braking means, and The gist is a reach-type forklift in which auxiliary braking force is applied to front wheels by auxiliary braking means.

According to this configuration, in the reach type forklift equipped with the auxiliary braking means and the braking hydraulic control device, when it is determined that the main braking of the rear wheel needs to be assisted, the auxiliary braking force is applied to the front wheel. Is provided, and claims 1 to 5
The same operation as the invention described in any one of the above is obtained.

[0021]

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

As shown in FIGS. 5 and 6, a reach type forklift truck 10 (hereinafter referred to as a forklift) as an industrial vehicle is a three-wheeled vehicle having two front wheels and one rear wheel. A pair of left and right reach legs 12 extend forward from a front portion of the vehicle body (machine stand) 11. Left and right front wheels (driven wheels) 13
Are the reach rails 1 that constitute the left and right reach legs 12
Each is rotatably supported at the tip of 2a. The rear wheels shown in FIG. 6 are drive wheels 14 which also serve as steering wheels. The drive wheel 14 is offset to the left in the vehicle width direction, and an auxiliary wheel (caster) (not shown) is provided right next to the drive wheel 14 at a predetermined distance.

A driver's seat (driver's cab) 15 (shown in FIG. 5) of a standing type is provided in the rear right portion of the body 11. As shown in FIG. 6, an instrument panel 11A on the front side of the driver's seat 15 is provided with a cargo handling lever 16 and an accelerator lever 17, and a handle (steering) is provided on the upper surface of a storage box 11B standing on the left side of the driver's seat 15. Wheel 18 is provided.

A mast device 19 as a cargo handling device mounted on the front side of the vehicle body 11 is provided movably in the front-rear direction along a pair of left and right reach legs 12. The mast device 19 is connected to a piston rod 20a of a reach cylinder (hydraulic cylinder) 20 disposed on the vehicle body 11,
By operating the reach lever of the cargo handling lever 16, hydraulic oil is supplied / discharged from the oil control valve 21, and the reach cylinder 20 is driven to expand and contract, so that the mast device 19 moves back and forth within a predetermined stroke range.

The mast device 19 includes a fork 22 and a lift cylinder 23. By operating a lift lever out of the cargo handling lever 16, the oil control valve 21 is operated.
When the hydraulic cylinder is supplied / discharged and the lift cylinder 23 is driven to expand and contract, the fork 22 moves up and down.

The forklift 10 is a battery car. A battery 24 is housed in the front of the vehicle body 11. A drive motor 25 for driving the drive wheels 14 is driven by a battery 24 as a power source, and is driven and controlled by a control unit 26 based on an operation of an accelerator lever 17. The control unit 26 has a built-in regenerative braking circuit for applying regenerative braking to the drive motor 25, and the regenerative brake is applied to the drive motor 25 when a switchback operation is performed in which the accelerator lever 17 is tilted in the direction opposite to the traveling direction. It is working. The main braking means is constituted by the control unit 26 for generating the regenerative brake and the drive motor 25. In this case, the accelerator lever 17 for performing the switchback operation which is the braking operation for applying the regenerative brake is the operating means. .

As shown in FIG. 5, a cargo handling motor 27 as an electric motor is disposed in the storage box 11B.
The cargo handling pump 27 as a hydraulic pump is driven by the cargo handling motor 27. The loading pump 28 is interposed on a hose 30 that connects an oil tank 29 and an oil control valve 21 (hereinafter, a control valve) disposed on the front right side of the vehicle body, and is pumped from the oil tank 29 through the hose 30. Control valve 21 with oil
To be discharged.

A brake control valve unit (hereinafter referred to as a brake valve unit) 31 as a braking hydraulic control device is disposed below the battery 24 and connected to the control valve 21 and the oil tank 29. The left and right front wheels 13 are equipped with auxiliary brake devices (drum brake devices) 32 as hydraulic auxiliary braking means, and the brake valve unit 31 is connected to the left and right auxiliary brake devices 32 through two hoses 33 and 34. Have been. A deadman type brake pedal 35 is provided on the floor of the driver's seat 15 and the brake pedal 3 is provided.
The brake is applied to the rear wheel 14 in a state where the depression of the step 5 is released, and also serves as a parking brake.

As shown in FIG. 4, the drive motor 25
The rear wheel (drive wheel) 14 is rotatably supported by a lower portion of a gear box 42 provided on the lower surface of the link member 40 so as to be relatively rotatable. Have been. A steering gear 41 formed at the upper end of the gear box 42 is operatively connected to the steering wheel 18, and the rear wheel 14 is connected to the steering wheel 1.
The steering is performed in response to the operation of No. 8.

The disk 4 is located above the drive motor 25.
A main brake device (disk brake device) 44 as main braking means for applying a brake to the drive motor 25 by pinching the brake motor 3 with a brake pad 44a is assembled. The main brake device 44 is mechanically connected to a brake pedal 35 as operation means via a link mechanism 45. On the upper surface of the drive motor 25, two rotation speed sensors 46 and 47 are provided at positions shifted by 90 degrees from each other. (Not shown) and outputs pulse signals 90 degrees out of phase. The control unit 26 detects the rotation direction by comparing the two pulse signals input from the two rotation speed sensors 46 and 47, and detects the rotation speed from the pulse count value per unit time of one of the pulse signals. A steering angle sensor 48 is provided near the steering gear 41. The steering angle sensor 48 detects the rotational position of the steering gear 41 and outputs a signal of a voltage value corresponding to the steering angle (tire angle) of the rear wheel 14. Output. The control unit 26 determines the steering angle of the rear wheel 14 from the voltage value of the input signal from the steering angle sensor 48. A brake switch 49 is provided below the brake pedal 35 to detect that the brake pedal 35 is at a brake operating position where the brake pedal 35 is not depressed.

FIG. 3 shows a cross section of the front wheel 13. Front wheel 13
Is a wheel 5 rotatably supported via a bearing 51 with respect to an axle 50 fixed to the reach rail 12a.
2 and a tire 53 fitted on the outer peripheral surface of the wheel 52 by a base band 53a. The auxiliary brake device 32 is mounted on the axle 50 and
Is arranged in the inner peripheral portion of the. On the inner side surface of the wheel 52, a large number of convex detection portions 52a are formed at a constant pitch in the circumferential direction.

On the lower surface of the reach rail 12a, a rotation speed sensor 54 is provided in a state covered by a guard member 55. The rotation speed sensor 54 is mounted and supported on a bracket 55a extending upward from the bottom of a guard member 55 fixed to the lower surface of the reach rail 12a, and is positioned in a position facing the detected portion 52a. In the present embodiment, the detected portion 52a is made of an iron-based metal, and the rotation speed sensor 54 is a magnetic sensor of a Hall element type, and outputs one pulse every time the detected portion 52a is detected. The control unit 26 calculates the rotation speed of the front wheel 13 by counting the number of input pulses per unit time from the rotation speed sensor 54.

FIG. 1 shows a hydraulic circuit and an electric circuit of the forklift 10. The lift lever 16A, the reach lever 16B, and the tilt lever (not shown) are mechanically connected to the control valve 21, and the operation of each of the three levers 16A, 16B indicates that the three cargo handling operation detection switches 61, 62. (One is omitted in the figure). When any one of the three switches 61 and 62 is in the detection state, the cargo handling motor 27 is driven by the control unit 26 and the hydraulic oil pumped up from the oil tank 29 by the cargo handling pump 28 is supplied to the pipeline (hose) 30. Is discharged to the control valve 21 through
Lift cylinder 2 according to the operation of levers 16A and 16B
3. The reach cylinder 20 and the tilt cylinder (not shown) are driven.

The brake valve unit 31 has a total of four ports: a pump port P as an input port, a tank port T, and two brake ports B1 and B2 as output ports. A supply pipe 63 branched from the middle of the pipe 30 is connected to the pump port P of the brake valve unit 31, and pressure oil from the cargo handling pump 28 is input to the pump port P through the supply pipe 63. The discharge line 64 connected to the tank port T is connected to the oil tank 29. The two brake ports B1 and B2 are connected to the wheel cylinders 67 and 67 of the left and right auxiliary brake devices 32 and 32 through two pipes (hoses) 33 and 34, respectively.
Connected to each other. Further, on the pipe 30, the downstream side of the branch point of the supply pipe 63 (the control valve 21
Side), a throttle valve 68 is provided.
When the valve is driven, a predetermined oil pressure is generated in the supply pipe 63 located upstream of the throttle valve 68 due to the presence of the throttle valve 68.

The brake valve unit 31 includes an accumulator 69, a pressure reducing valve 70, a check valve 71, and a pressure switch 7.
It is provided with two or two electromagnetic on-off valves (on / off valves) 73 and 74 and a pressure sensor 75. On the oil passage 76 connecting the pump port P and the tank port T, a pressure reducing valve 70, a check valve 71, and two electromagnetic on-off valves 73 and 74 are provided in series. The hydraulic circuit of the brake valve unit 31 includes a pressure accumulating function unit including an accumulator 69, a pressure reducing valve 70, a check valve 71, a pressure switch 72, and the like, and a hydraulic control unit including two electromagnetic on-off valves 73 and 74, a pressure sensor 75, and the like. Consists of

The accumulator function unit is a hydraulic circuit unit for accumulating hydraulic oil supplied from the pump port P in the accumulator 69 in order to use the accumulator 69 as a hydraulic source of the auxiliary brake device 32. Accumulator 69
Is connected to an oil passage 76 through an oil passage 77. The pressure reducing valve 70 reduces the pressure oil input from the pump port P to a predetermined pressure. The valve opening pressure of the check valve 71 is set so as to open until the accumulated pressure value (oil pressure) of the accumulator 69 reaches the set pressure. The pressure switch 72 is connected to the accumulator 6
9 to detect that the accumulated pressure value has reached the lower limit, and the detection signal is output to the control unit 26. When a detection signal is input from the pressure switch 72, the control unit 26 drives the cargo handling motor 27 in the same manner as when a detection signal is input from the cargo handling operation detection switches 61 and 62.

Next, the hydraulic control unit will be described. Oilway 7
6 is connected between the two electromagnetic on-off valves 73 and 74 through the oil passage 78 to the brake ports B1 and B2, and is connected to the pressure sensor 75 through the oil passage 79. The pressure is detected by a pressure sensor 75. Two solenoid on-off valves 7
The opening and closing of the solenoids 3 and 74 are controlled by the control unit 26 that controls the excitation and demagnetization of the solenoids 73A and 74A. The solenoid on-off valve 73 closes when the solenoid 73A is demagnetized and opens when energized. On the other hand, the solenoid on-off valve 74 is a solenoid 74
The valve opens when the A is demagnetized and closes when the A is excited. When the operation of the auxiliary brake device 32 is not necessary, the two solenoids 73
A, 74A are both demagnetized, and brake ports B1, B2
The electromagnetic on-off valve 73 is closed so that the hydraulic pressure of the accumulator 69 is not applied to the valve, and the electromagnetic on-off valve 74 is opened, so that the brake ports B1 and B2 communicate with the tank port T.

The control unit 26 is provided with a memory 26A. The memory 26A has a judgment program for judging whether or not the front wheel brake is necessary, and the wheel cylinder 6
The data of the set hydraulic pressure at the time of braking of No. 7 and the like are stored. The control unit 26 detects when the switchback operation of the accelerator lever 17 is detected based on the detection value of the accelerator sensor 80, or detects the operation of releasing the brake pedal 35 (that is, the braking operation) based on the detection signal of the brake switch 49. Then, execute the judgment program. When it is detected that the slip of the rear wheel 14 exceeds the threshold value based on the determination program, the auxiliary brake device 32 is operated. That is, the electromagnetic opening / closing valve 73 for supply is opened and the electromagnetic opening / closing valve 74 for discharging is closed, and the brake port B
The output hydraulic pressures of 1 and B2 are raised. If this state is left, an excessive braking force having a strength balanced with the accumulated pressure value of the accumulator 69 is applied to the front wheel 13. Therefore, by opening the electromagnetic on-off valve 74 for discharging and appropriately draining oil, the oil pressure detected by the pressure sensor 75 is detected. Are controlled to open and close both electromagnetic on-off valves 73 and 74 so that the pressure becomes the set hydraulic pressure. The braking force of the auxiliary brake device 32 is determined according to the hydraulic pressure introduced into the wheel cylinder 67.

In the present embodiment, the data of the set hydraulic pressure is a constant value, and when the rear wheel 14 slips beyond the threshold value during the braking operation, the braking distance of the forklift 10 does not become so long, The value of the set hydraulic pressure is set so as to provide an auxiliary braking force that does not cause load collapse. The braking force of the auxiliary brake device 32 may be varied according to the slip amount of the rear wheel 14 (the greater the slip amount of the rear wheel, the stronger the braking force of the front wheel).

The slip detection of the rear wheel 14 employs a method of comparing the respective rotations of the front wheel 13 as a driven wheel and the rear wheel 14 as a driving wheel. That is, after calculating the front wheel vehicle speed VF calculated by multiplying the rotation speed (angular speed) of the front wheel 13 by the front wheel tire diameter (radius), and multiplying the rotation speed (angular speed) of the rear wheel 14 by the rear wheel tire diameter (radius). The slip of the rear wheel 14 is obtained by comparing the wheel speed Vr. However, considering that the turning radii of the front wheels 13 and the rear wheels 14 are different when the vehicle is turning, the correction coefficient (K (θ): steering angle θ) is added to the front wheel vehicle speed VF.
), The front vehicle speed VF is converted into a vehicle speed (= Vf · K (θ)) corresponding to the rear wheel position, and the converted vehicle speed Vf can be regarded as the vehicle speed at the rear wheel position. Vf
Is compared with the rear wheel speed Vr to detect slip. The forklift 10 has a maximum steering angle (minimum turning radius).
In the vicinity, the vehicle can turn around the front wheel 13 on the turning inner wheel side, and the front wheel 13 on the turning inner wheel side has a vehicle speed of “0”.
Therefore, the rotational speed of the front wheel 13 on the turning outer wheel side is used. Which of the left and right front wheels 13 is on the turning outer wheel side is determined from the detection value of the steering angle sensor 48. When the steering angle is 0 °, the vehicle travels on either the left or right front wheel speed.

The correction coefficient K corresponding to the steering angle θ is added to the front wheel vehicle speed VF calculated from the rotation speed of the front wheel 13 on the turning outer wheel side.
(Θ), the vehicle speed Vf corresponding to the rear wheel position,
When the slip amount (slip speed) ΔV (= Vf−Vr), which is a speed difference from the rear wheel vehicle speed Vr, exceeds a preset threshold value, it is determined that the rear wheel 14 is slipping. It should be noted that a slip ratio (= (Vf-Vr) / Vf) may be used for the slip determination instead of the slip amount.

Next, the structure of the brake valve unit 31 will be described. FIG. 2 shows the brake valve unit 31,
(A) is a front view, (b) is a side view, and (c) is a plan view. The brake valve unit 31 includes a rectangular parallelepiped valve body 81. An accumulator 69, a pressure reducing valve 70, a pressure switch 72, a pressure sensor 7
5 and two solenoid on-off valves 73 and 74 are assembled. The valve body 81 is provided with four ports: a pump port P, a tank port T, and two brake ports B1 and B2. Note that the check valve 71 is a valve body 81.
It is built in.

Next, the braking operation of the forklift 10 will be described. The accumulator 69 stores a hydraulic pressure equal to or higher than the lower limit. During operation of the forklift 10, the control unit 26 executes a predetermined determination program at predetermined time intervals.

When the accelerator lever 17 is switched back while the forklift 10 is running, a regenerative brake is applied to the drive motor 25 to apply a braking force to the rear wheels 14. When the depression of the brake pedal 35 is stopped, the main brake device 44 is operated, and a braking force is applied to the rear wheel 14. For example, if braking is applied on a wet road surface or a frozen road surface in a freezer warehouse, the rear wheel 14 slips. Especially when the forklift 10 is in a loaded state, the rear wheels 1
Since the wheel weight of No. 4 is relatively small, the frictional force between the rear wheel 14 and a wet road surface or a frozen road surface is considerably reduced.

The control unit 26 is triggered by the detection of the braking operation.
Executes the determination program, and when the slip of the rear wheel 14 exceeds the threshold value, the control unit 26 commands the operation of the auxiliary brake device 32. That is, both solenoids 73
A and 74A are excited, the electromagnetic on-off valve 73 is opened in the brake valve unit 31 and the electromagnetic on-off valve 74 is opened.
Closes. The two solenoid valves 73 and 74 are controlled to open and close so that the detected value of the pressure sensor 75 becomes the set oil pressure, and the output oil pressure of each of the brake ports B1 and B2 (that is, the oil pressure of the wheel cylinder 67) is adjusted to the set oil pressure. Is done. As a result, when the rear wheel 14 slips, the auxiliary brake devices 32, 32 are actuated, and a braking force is applied to the left and right front wheels 13, 13 to assist braking of the vehicle. At this time, the front wheels 13 and 13 are unlikely to slip because the weight of the front wheels 13 and 13 during loading is increased and only a relatively small braking force is applied. Therefore, even if the brake is operated on a wet road surface or a frozen road surface, the braking distance does not become much longer,
Due to the slip of the rear wheel 14 located offset from the center of the vehicle width, the rearward swinging of the rear portion of the vehicle body 11 in the left-right direction is unlikely to occur.

When the speed of the forklift 10 becomes low enough to stop or stop, or when the braking operation is released before the vehicle stops, the operation of the auxiliary brake device 32 is stopped. That is, the two solenoids 73A and 74A are both demagnetized by the control unit 26, and
Is closed, the electromagnetic on-off valve 74 opens, the pressure oil of the wheel cylinder 67 is discharged to the oil tank 29, and the operation of the auxiliary brake device 32 is stopped.

When the hydraulic pressure of the accumulator 69 decreases due to the operation of the auxiliary brake device 32 and the pressure switch 72 detects that the hydraulic pressure has fallen below the lower limit value, the cargo handling motor 27 is driven and the accumulator 69 supplies the lower limit value to the accumulator 69. Is supplied until the pressure reaches. Each time the lift lever 16A or the reach lever 16B is operated (except for lift lowering operation) and the cargo handling motor 27 is driven for cargo handling work, the accumulator 69 is supplied through the supply pipe 63.
The accumulator 69 has a check valve 71
Is closed and the pressure oil is accumulated until the set pressure is reached.

As described in detail above, according to the present embodiment,
The following effects can be obtained. (1) At the time of regenerative braking of the drive motor 25 due to the switchback operation of the accelerator lever 17 or when the brake pedal 3
If the slippage exceeding the threshold value occurs on the rear wheel 14 during the operation of the main brake device 44 accompanying the depression release operation of No. 5, the auxiliary brake device 32 is operated by the control unit 26 and the braking force is applied to the front wheel 13. The forklift 10 is assisted in braking. For this reason, for example, even if a braking operation is performed on a wet road surface or a frozen road surface and the rear wheel 14 slips, the braking distance of the forklift 10 does not become so long, and the lateral force (side force) applied to the drive wheel 14 at the time of slipping. It is possible to minimize the butt swing phenomenon in which the rear portion of the vehicle body moves in the left-right direction due to skidding.

(2) The brake valve unit 31 employs a pressure control system for controlling the opening and closing of two electromagnetic on-off valves (on / off valves) 73 and 74 so that the oil pressure detected by the pressure sensor 75 becomes the set oil pressure. For this reason, the auxiliary brake device 32
The brake valve unit 31 for controlling the output oil pressure to the wheel cylinder 67 can be realized with a relatively simple configuration using two electromagnetic on-off valves 73 and 74 as electromagnetic valve means.

(3) Since the cargo handling motor 27 and the cargo handling pump 28 already provided in the forklift 10 are used as the hydraulic source of the auxiliary brake device 32, there is no need to add a dedicated pump or a dedicated motor. For this reason, it is possible to avoid an increase in the size of the forklift 10 due to the addition of this kind of dedicated parts and securing a space for disposing the dedicated parts. Further, not only when the pressure switch 72 is turned on, but the accumulation of hydraulic oil in the accumulator 69 progresses every time the cargo handling motor 27 is driven for the cargo handling operation, the hydraulic pressure lower limit of the accumulator 69 for turning on the pressure switch 72 is lowered. By setting to, the driving frequency of the cargo handling motor 27 for the purpose of only accumulating the hydraulic oil in the accumulator 69 can be reduced, and the power consumption of the battery 24 can be reduced.

(4) Although the cargo handling pump 28 is large and has a slight rise delay when it is driven, since the accumulator 69 stored in advance is used as the hydraulic pressure source of the brake valve unit 31, the auxiliary brake device 32 is used.
Quick operation response can be secured.

(Second Embodiment) Next, a second embodiment will be described with reference to FIGS. This embodiment is
This is an example in which the structure of the brake valve unit is different from that of the first embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Only different points will be described.

FIG. 7 shows a hydraulic circuit and an electric circuit of the forklift 10. In the figure, only the configuration of the brake valve unit 31 is different from that of the first embodiment, so only the hydraulic circuit configuration of the brake valve unit 31 will be described.

The brake valve unit 31 has a total of four ports: a pump port P as an input port, a tank port T, and two brake ports B1 and B2 as output ports. Pressure oil from the cargo handling pump 28 is input to the pump port P through the supply pipe 63. The hydraulic oil discharged from the tank port T is discharged to the oil tank 29 through the discharge line 64. The two brake ports B1, B2 are connected to the wheel cylinders 67, 67 of the left and right auxiliary brake devices 32, 32 through two pipes (hoses) 33, 34, respectively.

The brake valve unit 31 includes an accumulator 69, a pressure reducing valve 70, a check valve 71, and a pressure switch 7.
2. A shut-off valve (electromagnetic on-off valve) 82 and a linear solenoid valve 83 as an electromagnetic proportional pressure adjusting valve are provided.

The hydraulic circuit of the brake valve unit 31 includes a pressure accumulating function section including an accumulator 69, a pressure reducing valve 70, a check valve 71, a pressure switch 72, and the like, and a hydraulic control section including a shutoff valve 82, a linear solenoid valve 83, and the like. Consists of The pressure storage function unit has the same hydraulic circuit configuration as that of the first embodiment.

An oil passage 76 in which a pressure reducing valve 70, a check valve 71, a shut-off valve 82 and a linear solenoid valve 83 are provided in series is connected to a pump port P and brake ports B1, B
2 is connected.

The shut-off valve 82 has its solenoid 82
A is controlled to be opened and closed by the excitation and demagnetization control by the control unit 26, and is closed by the urging force of the spring when the solenoid 82A is demagnetized, and is opened when the solenoid 82A is excited.
The linear solenoid valve 83 is controlled by a current value (for example, duty control) by the control unit 26,
The opening is controlled in accordance with the value of the current flowing through the solenoid 83A, and is proportional to the value of the current flowing through the solenoid 83A when the shutoff valve 82 is opened and the introduced hydraulic pressure is applied to its input port through the oil passage 76. The output hydraulic pressure is output from the output port. The output port of the linear solenoid valve 83 is connected to the two brake ports B1 and B2, and the discharge port thereof is connected to the tank port T through a pipe 78.
Is connected to

The memory 26A of the control unit 26 stores a determination program similar to that of the first embodiment and data of a current command value to be output to the linear solenoid valve 83 when an auxiliary brake operation command is issued. When a current having a predetermined set value is passed through the solenoid 83A, a hydraulic pressure uniquely determined from the current value is output to the wheel cylinders 67, 67 through the brake ports B1, B2, and the auxiliary brake devices 32, 32 are driven with a predetermined braking force. Operate. The shut-off valve 82 serves to prevent oil leakage that occurs when oil pressure is still applied to the linear solenoid valve 83 and to prevent a decrease in oil pressure of the accumulator 69 due to the oil leakage. In particular, if the oil leakage from the linear solenoid valve 83 is sufficiently small, the shut-off valve 82 can be omitted.

The contents of the judgment program are the same as those of the first embodiment.
The determination program is executed at the time of the switch-back operation or the operation of releasing the depression of the brake pedal 35. When it is detected that the slip of the rear wheel 14 exceeds the threshold,
At the same time when the shut-off valve 82 is opened, a current having a set value is output to the linear solenoid valve 83, and the auxiliary brake device 32 is operated with a preset braking force.

Next, the structure of the brake valve unit 31 will be described. FIG. 8 shows the brake valve unit 31,
(A) is a front view, (b) is a side view, and (c) is a bottom view. The brake valve unit 31 has a valve body 84 having a rectangular parallelepiped shape.
A tank port T and two brake ports B1 and B2 are attached. An accumulator 69, a pressure reducing valve 70, a pressure switch 72, a shutoff valve 82, and a linear solenoid valve 83 are attached to the valve body 84. Compared to the first embodiment, the number of parts to be assembled is reduced and the size of the valve body 84 is reduced due to the absence of the pressure sensor 75.

As described in detail above, according to the present embodiment,
The same advantages (1), (3), and
In addition to (4), the following effects can be obtained. (5) Since the output oil pressure is uniquely determined by the use of the linear solenoid valve 83, the desired oil pressure can be obtained from the brake ports B1 and B2 without using the pressure sensor 75 used in the first embodiment. Hydraulic pressure can be taken out reliably. Therefore, the pressure sensor 75 can be eliminated, and the brake valve unit 31 can be made smaller than the configuration of the first embodiment.

The embodiment is not limited to the above embodiment, but may be modified as follows. The arrangement position of the brake valve unit 31 in the reach type forklift 10 can be appropriately changed. As shown in FIG. 9, for example, a space is secured below the driver's seat 15 by devising the structure of the rear suspension mechanism, and the brake valve unit 31 is arranged below the driver's seat 15 at the position shown in FIG. According to this configuration, the pipes (hoses) 33 and 34 extending from the brake valve unit 31 to the auxiliary brake device 32 avoid the bent paths bypassing the reach rail 12a as shown in FIG.
4 can be piped in a smooth path with little bending.

The auxiliary brake device 32 as auxiliary braking means may be always activated when a braking operation such as a switchback operation of the accelerator lever 17 or an operation of releasing the brake pedal 35 is performed. For example, when a slip exceeding the threshold value is detected on the rear wheel to which the main brake is applied during the braking operation, the braking force of the auxiliary brake device 32 is made stronger than the braking force in the normal state (when the rear wheel is not slipping) by the amount of the assistance. I do. With this configuration also, the braking distance of the vehicle can be shortened.

The condition for activating the auxiliary brake device is not limited to when the rear wheel (drive wheel) 14 slips. The auxiliary brake device can be operated to prevent the braking distance from becoming longer when other conditions for increasing the braking distance (for example, at a high vehicle speed) are satisfied, or to actively shorten the braking distance. .

For example, if the deceleration at the time of braking is smaller than a preset value, the auxiliary brake device is activated,
The configuration may be such that the auxiliary brake device is operated at the time of a brake operation during high-speed running. The auxiliary brake device may be operated for other purposes. In short, the auxiliary brake device can be widely used for the purpose of assisting the main brake device, and further when the automatic control requires additional brake.

The pump is not limited to a cargo handling pump. For example, a configuration may be adopted in which a dedicated pump for braking is provided, and pressure oil is supplied from the dedicated pump to the brake valve unit. ○ The front wheel is not limited to the driven wheel. For example, the present invention may be applied to a three-wheel drive (3WD) type reach-type forklift in which the front wheels are drive wheels. For example, the slip of the rear wheel is determined as slip when the deceleration of the rear wheel becomes a value that cannot be obtained by normal braking, and the auxiliary brake device is operated. Even when the present invention is applied to a 3WD type forklift, it is possible to suppress the braking distance from becoming long as much as possible.

The main braking by the main braking device may be applied to the front wheels, and the auxiliary braking by the auxiliary braking device may be applied to the rear wheels. For example, in the case of a forklift, when the load is empty, the weight of the front wheel is relatively small and the front wheel tends to slip, but when the front wheel slips, the auxiliary brake is applied to the rear wheel or it becomes stronger than the normal braking force Therefore, it is possible to prevent the braking distance from becoming long.

The auxiliary brake device is not limited to a drum brake device. For example, a hydraulic disc brake device may be employed. The brake hydraulic control device is a brake valve unit 31 in which a plurality of components such as various valves are integrally unitized. However, the pressure reducing valve 70 and the solenoid valves 73, 74, 82, and 83 are individually connected by piping. May be adopted.

The throttle valve 68 is connected to the control valve 21.
It may be built in. The rear wheel 14 is not limited to being located off center of the vehicle width. For example, a configuration in which there is one rear wheel (drive wheel) at the center of the vehicle width, or two rear wheels (drive wheels) on the left and right may be employed.

The industrial vehicles are not limited to reach type forklifts. The rear wheel may be a drive wheel and a main brake may be applied, and the forklift may not include the reach mechanism of the mast device, or may include a configuration in which an auxiliary brake device is provided on the front wheel of such a forklift. For example, it can be applied to an order picker type forklift. It can also be applied to unmanned forklifts.

The present invention may be applied to an industrial vehicle such as an engine vehicle. Even in the case of an engine vehicle, the braking distance can be reduced as compared with the related art by applying the auxiliary brake to the wheel on the side opposite to the main brake side and the wheel on the opposite side. In the case of an engine vehicle, the cargo handling pump is constantly driven by the power of the engine during the operation of the vehicle. Therefore, even if the accumulator is abolished, quick operation response of the auxiliary brake device can be obtained.

The technical ideas other than the claims that can be grasped from the above embodiments are described below. In any one of the first to sixth aspects of the present invention, the hydraulic circuit includes a pressure accumulator for accumulating 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 oil pressure through the electromagnetic valve means and immediately output, so that, for example, the industrial vehicle is a battery vehicle and the cargo handling pump is electrically operated. Even when the motor is driven only when necessary by the motor, quick operation response of the auxiliary braking means can be obtained.

[0074]

According to the present invention, when it is necessary to assist the braking of a wheel subjected to main braking, the vehicle is braked by an automatic brake control for applying an auxiliary braking force to the wheel opposite to the front and rear wheels. The distance can be effectively reduced, and the output hydraulic pressure to the auxiliary braking means can be well controlled by the electromagnetic valve means of the hydraulic circuit so that the required auxiliary braking force can be obtained.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit of an auxiliary brake system according to a first embodiment.

2 (a) is a front view, FIG. 2 (b) is a side view, and FIG. 2 (c) is a plan view.

FIG. 3 is a schematic front sectional view of a front wheel.

FIG. 4 is a rear view of a drive mechanism for a rear wheel.

FIG. 5 is a cross-sectional plan view of the reach type forklift.

FIG. 6 is a side view of the same.

FIG. 7 is a hydraulic circuit of an auxiliary brake system according to a second embodiment.

8 (a) is a front view, FIG. 8 (b) is a side view, and FIG. 8 (c) is a bottom view.

FIG. 9 is a cross-sectional plan view of another example of a reach-type forklift.

FIG. 10 is a hydraulic circuit showing a conventional brake system.

[Explanation of symbols]

10 ... Reach type forklift as an industrial vehicle, 13
... front wheel, 14 ... drive wheel (rear wheel), 17 ... accelerator lever as operating means, 19 ... mast device as cargo handling device, 25 ... drive motor as main braking means, 27 ...
A loading motor as an electric motor, 28 a loading pump as a hydraulic pump, 31 a brake valve unit as a braking hydraulic control device, 32 an auxiliary brake device as auxiliary braking means, 35 a brake pedal as operating means 44, a disk brake device as a main braking means, 72, a pressure sensor, 73, a supply electromagnetic on-off valve constituting electromagnetic valve means, 74, a discharge electromagnetic on-off valve constituting electromagnetic valve means, 82, electromagnetic Shut-off valve that constitutes the valve means, 83: The solenoid valve means which constitutes the electromagnetic valve means and a linear solenoid valve as an electromagnetic proportional pressure regulating valve, P: Pump port as an input port, B1, B2 ... Brake as an output port port.

Claims (6)

[Claims] 1. When a braking operation is performed on an operating means for operating a main braking means for braking a front wheel or a rear wheel which is a driving wheel, when it is determined that the braking of the driving wheel needs to be assisted, A braking hydraulic control device for operating a hydraulic auxiliary braking means for applying an auxiliary braking force to wheels opposite to front and rear sides of a driving wheel, comprising: an input port to which hydraulic oil is input from a hydraulic pump; A hydraulic pressure having an output port for outputting pressure oil for operating the braking means, and an electromagnetic valve means for performing hydraulic control for outputting a hydraulic pressure according to a preset value as a braking force of the auxiliary braking means from the output port A hydraulic control device for braking in an industrial vehicle provided with a circuit. 2. The drive wheel to which braking by the main braking means is applied is a wheel of a front wheel and a rear wheel, the wheel load of which is smaller as the loading load of a cargo handling device mounted on a vehicle is larger, The hydraulic control system for braking in an industrial vehicle according to claim 1, wherein the wheels to which auxiliary braking by the auxiliary braking unit is applied are wheels on the side where the wheel load increases as the loading load of the cargo handling device increases. 3. The hydraulic circuit is provided with a pressure sensor for detecting a hydraulic pressure output to the auxiliary braking means, and the electromagnetic valve means is provided with a pair of electromagnetic switches provided upstream and downstream of the output port. A pair of electromagnetic on-off valves for supplying pressure oil from a hydraulic pressure source to the output port side, and a discharge electromagnetic on-off valve for discharging the pressure oil supplied to the output port side. 3. The industrial vehicle according to claim 1, wherein the industrial vehicle comprises a valve, and is controlled to output a preset hydraulic pressure from the output port based on a detection value of the pressure sensor when the auxiliary braking unit is operated. 4. Hydraulic control device for braking in 4. The electromagnetic valve means includes an electromagnetic proportional pressure adjusting valve for adjusting a hydraulic pressure to be output to the auxiliary braking means. The electromagnetic proportional pressure adjusting valve is provided in advance when the auxiliary braking means is operated. The hydraulic pressure control device for braking in an industrial vehicle according to claim 1 or 2, wherein current value control is performed so that the set hydraulic pressure is output from the output port. 5. An industrial vehicle, comprising: a cargo handling pump for supplying pressure oil for operating a cargo handling device provided on the vehicle; and an electric motor for driving the cargo handling pump; The hydraulic control device for braking in an industrial vehicle according to any one of claims 1 to 4, wherein the port is supplied with hydraulic oil from the cargo handling pump. 6. The industrial vehicle is a reach-type forklift wherein a rear wheel, which is a driving wheel, is braked by the main braking unit, and an auxiliary braking force is applied to a front wheel by the auxiliary braking unit. The brake hydraulic control device for an industrial vehicle according to any one of claims 1 to 5.