Industrial vehicle

Abstract

To suppress decrease in brake force when regenerative brake force cannot be utilized in an industrial vehicle which can use both of regenerative brake force and mechanical brake force.SOLUTION: An industrial vehicle 1 comprises a travel motor 5 which generates regenerative brake force, and a hydraulic service brake 8d which generates mechanical brake force. The industrial vehicle 1 comprises: a low pressure path 11 which is a working fluid hydraulic path configured so that a hydraulic pressure for operating the service brake 8d becomes a prescribed first hydraulic pressure; a high pressure path 12 which is a working fluid hydraulic path configured so that the hydraulic pressure for operating the service brake 8d becomes a prescribed second hydraulic pressure higher than the first hydraulic pressure; and a hydraulic pressure switching part 10 which switches the hydraulic path so as to operate the service brake 8d with the first hydraulic pressure when the regenerative brake force can be utilized and to operate the service brake 8d with the second hydraulic pressure when the regenerative brake force cannot be utilized.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an industrial vehicle. [Background technology]

[0002] 2. Description of the Related Art Conventionally, as a technique relating to braking of industrial vehicles, there is known an industrial vehicle that includes, as a braking section, a travel motor that generates a regenerative braking force and a mechanical brake that is actuated by fluid pressure to generate a mechanical braking force (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-125603 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an industrial vehicle equipped with the above-mentioned brake unit, when regenerative braking force can be utilized, the regenerative braking force and the mechanical braking force are used together to obtain a predetermined overall braking force. In such an industrial vehicle, the output of the mechanical braking force is generally determined based on the combined use of the regenerative braking force and the mechanical braking force. However, when the regenerative braking force cannot be utilized, the overall braking force may be reduced compared to when the regenerative braking force and the mechanical braking force are used together.

[0005] An object of the present invention is to suppress a decrease in braking force when regenerative braking force cannot be used in an industrial vehicle capable of using both regenerative braking force and mechanical braking force. [Means for solving the problem]

[0006] One aspect of the present invention is an industrial vehicle equipped with a travel motor that generates a regenerative braking force and a hydraulic service brake that generates a mechanical braking force, and is equipped with a low-pressure path that is a hydraulic path for hydraulic oil configured so that the hydraulic pressure that operates the service brake is a predetermined first hydraulic pressure, a high-pressure path that is a hydraulic path for hydraulic oil configured so that the hydraulic pressure that operates the service brake is a predetermined second hydraulic pressure higher than the first hydraulic pressure, and a hydraulic switching unit that switches the hydraulic paths so that the service brake is operated with the first hydraulic pressure when the regenerative braking force can be used, and is operated with the second hydraulic pressure when the regenerative braking force cannot be used.

[0007] In an industrial vehicle according to one aspect of the present invention, in response to switching of the hydraulic path by the hydraulic pressure switching unit, the service brake operates with a first hydraulic pressure when the regenerative braking force can be used, and operates with a second hydraulic pressure higher than the first hydraulic pressure when the regenerative braking force cannot be used. This increases the mechanical braking force according to the second hydraulic pressure, making it possible to compensate for the reduced braking force when the regenerative braking force cannot be used. Therefore, in an industrial vehicle that can use both regenerative braking force and mechanical braking force, it is possible to suppress the reduction in braking force when the regenerative braking force cannot be used.

[0008] In one embodiment, the low pressure path has a pressure reducing valve, the high pressure path has a normally open solenoid valve that connects the upstream and downstream of the low pressure path so as to bypass the pressure reducing valve and allows the flow of hydraulic oil when not energized, and the hydraulic pressure switching unit may energize the solenoid valve when the regenerative braking force can be used, and may not energize the solenoid valve when the regenerative braking force cannot be used. For example, when the regenerative braking force can be used, the solenoid valve energized by the hydraulic pressure switching unit closes to block the flow of hydraulic oil in the high pressure path, so that the hydraulic oil is reduced in pressure through the pressure reducing valve in the low pressure path. When the regenerative braking force cannot be used, the normally open solenoid valve is not energized by the hydraulic pressure switching unit and opens to allow the flow of hydraulic oil in the high pressure path, so that the hydraulic oil bypasses the pressure reducing valve through the high pressure path. In this way, the hydraulic pressure path can be switched so that the service brake operates with a first hydraulic pressure when the regenerative braking force can be used, and operates with a second hydraulic pressure higher than the first hydraulic pressure when the regenerative braking force cannot be used.

[0009] In one embodiment, the low pressure path has a pressure reducing valve, the high pressure path connects the upstream and downstream of the low pressure path so as to bypass the pressure reducing valve, and has a solenoid valve, and the hydraulic switching unit may have a controller that closes the solenoid valve when the regenerative braking force can be used, and opens the solenoid valve when the regenerative braking force cannot be used. For example, when the regenerative braking force can be used, the solenoid valve closed by the controller blocks the flow of hydraulic oil in the high pressure path, so that the hydraulic oil is reduced in pressure through the pressure reducing valve in the low pressure path. When the regenerative braking force cannot be used, the solenoid valve opened by the controller allows the flow of hydraulic oil in the high pressure path, so that the hydraulic oil bypasses the pressure reducing valve through the high pressure path. In this way, the hydraulic path can be switched so that the service brake operates with a first hydraulic pressure when the regenerative braking force can be used, and operates with a second hydraulic pressure higher than the first hydraulic pressure when the regenerative braking force cannot be used.

[0010] In one embodiment, the low pressure path includes a first master cylinder that generates a first hydraulic pressure and a first switching valve that switches whether or not to allow the flow of hydraulic oil, the high pressure path includes a second master cylinder that generates a second hydraulic pressure and a second switching valve that switches the flow of hydraulic oil to be reverse to that of the first switching valve, and the hydraulic pressure switching unit may include a controller that controls the first switching valve and the second switching valve so that the service brake is operated using the first master cylinder when the regenerative braking force can be used, and the service brake is operated using the second master cylinder when the regenerative braking force cannot be used. For example, when the regenerative braking force can be used, the controller controls the first switching valve and the second switching valve so that the service brake is operated with the first hydraulic pressure using the first master cylinder. When the regenerative braking force cannot be used, the controller controls the first switching valve and the second switching valve so that the service brake is operated with the second hydraulic pressure using the second master cylinder. In this way, the hydraulic path can be switched so that the service brake operates with a first hydraulic pressure when regenerative braking force is available, and operates with a second hydraulic pressure higher than the first hydraulic pressure when regenerative braking force is not available. Effect of the Invention

[0011] According to one aspect of the present invention, in an industrial vehicle capable of using both regenerative braking force and mechanical braking force, it is possible to suppress a decrease in braking force when regenerative braking force cannot be used. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram illustrating an industrial vehicle according to a first embodiment. [Diagram 2] 11A and 11B are diagrams illustrating an example of a regenerative braking force and a mechanical braking force in a case where the regenerative braking force can be utilized. [Diagram 3] 11A and 11B are diagrams illustrating an example of a regenerative braking force and a mechanical braking force in a case where the regenerative braking force cannot be utilized. [Figure 4] 10 is a flowchart illustrating an example of a process of a controller. [Diagram 5] FIG. 11 is a schematic configuration diagram illustrating an industrial vehicle according to a second embodiment. [Figure 6] FIG. 4 is a schematic diagram showing the states of a first changeover valve and a second changeover valve when a service brake is operated using a first master cylinder. [Figure 7] FIG. 4 is a schematic diagram showing the state of the first changeover valve and the second changeover valve when the service brake is operated by using the second master cylinder. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same or corresponding elements are designated by the same reference numerals, and duplicated description will be omitted.

[0014] 1 is a schematic configuration diagram illustrating an industrial vehicle according to a first embodiment. An example of the industrial vehicle 1 according to the present embodiment is an electric forklift.

[0015] 1, the industrial vehicle 1 includes front wheels 2, rear wheels 3, a battery 4, a traveling motor 5, a drive system 6, a hydraulic path 7, and a brake system 8. The industrial vehicle 1 is configured such that the driving force generated by the traveling motor 5 is transmitted to the drive wheels via the drive system 6.

[0016] The front wheels 2 are wheels arranged at the front of the body of the industrial vehicle 1, and are, for example, a pair of left and right drive wheels. When the industrial vehicle 1 is an electric forklift, the front wheels 2 correspond to the wheels on the side of the body of the industrial vehicle 1 on which a loading device including a mast and forks is provided. The rear wheels 3 are wheels arranged at the rear of the body of the industrial vehicle 1, and are, for example, a pair of left and right steering wheels.

[0017] The battery 4 is a power source that outputs DC power. For example, a secondary battery such as a lead-acid battery or a lithium-ion battery is used as the battery 4. The battery 4 supplies power for driving to the traveling motor 5 and receives regenerative power from the traveling motor 5. The battery 4 is connected to the controller 20 and transmits battery information including, for example, a battery charging rate and a battery temperature to the controller 20.

[0018] The traveling motor 5 is a motor generator for driving the industrial vehicle 1. The traveling motor 5 is, for example, a three-phase AC rotary motor. The traveling motor 5 generates driving force in response to power supply from the battery 4. When regenerative braking force can be utilized, the traveling motor 5 generates regenerative braking force based on a control signal from the controller 20. The traveling motor 5 is connected to the controller 20, and transmits motor information including, for example, the state of a motor rotation speed sensor to the controller 20.

[0019] A drive system 6 is interposed between the front wheels 2 and the traveling motor 5. The drive system 6 includes, for example, a speed reduction gear and a shaft. The front wheels 2 are driven or decelerated by the traveling motor 5 via the drive system 6.

[0020] The brake system 8 is a system for braking the wheels (here, the front wheels 2) of the industrial vehicle 1 by the brake operation of the operator of the industrial vehicle 1. The brake system 8 here transmits hydraulic pressure generated by the brake operation of the operator along a hydraulic path 7 to brake the front wheels 2. The brake system 8 has a brake pedal 8a, a master cylinder 8b, a reservoir tank 8c, and a service brake 8d. That is, the industrial vehicle 1 is equipped with a travel motor 5 that generates a regenerative braking force, and a hydraulic service brake 8d that generates a mechanical braking force.

[0021] The brake pedal 8a is a pedal that is depressed by an operator to apply the brakes. The master cylinder 8b generates hydraulic pressure for actuating a service brake 8d in response to depression of the brake pedal 8a. The service brake 8d is a hydraulic service brake that generates a mechanical braking force, and may be, for example, a drum brake.

[0022] When the brake pedal 8a is depressed, the piston rod and piston inside the master cylinder 8b push hydraulic oil from the reservoir tank 8c, generating hydraulic pressure. The hydraulic pressure generated in the master cylinder 8b is transmitted to the service brake 8d via the hydraulic oil along the hydraulic path 7, and the service brake 8d is actuated. As a result, the front wheels 2 are braked.

[0023] In the industrial vehicle 1, the output of the regenerative braking force and the output of the mechanical braking force are preset so that the regenerative braking force and the mechanical braking force are used together to obtain a set braking force (predetermined braking force) as a whole when the regenerative braking force can be used. FIG. 2 is a diagram showing an example of the regenerative braking force and the mechanical braking force when the regenerative braking force can be used. The horizontal axis of FIG. 2 is the pedal force of the brake pedal 8a, and the vertical axis is the overall braking force in the industrial vehicle 1. As shown in FIG. 2, in the industrial vehicle 1, the braking force is set so that the regenerative braking force Brc is added to the mechanical braking force B1 to obtain a set braking force B2 as a whole when the regenerative braking force can be used. As in the example of FIG. 2, when the brake pedal 8a starts to be depressed, only the regenerative braking force Brc may be generated first. When the brake pedal 8a is depressed with a predetermined pedal force or more, the mechanical braking force B1 and the regenerative braking force Brc may each increase according to the pedal force.

[0024] The mechanical braking force B1 in Fig. 2 is the mechanical braking force when the service brake 8d is operated with the first hydraulic pressure. The first hydraulic pressure is a predetermined hydraulic pressure that operates the service brake 8d when the regenerative braking force can be used. The first hydraulic pressure is determined according to the hydraulic path 7 and the brake system 8. Therefore, for example, when the regenerative braking force cannot be used, a larger brake pedal pressure is required to generate the same braking force as when the regenerative braking force can be used.

[0025] Therefore, the industrial vehicle 1 is provided with a hydraulic pressure switching unit 10 that switches the hydraulic pressure path depending on whether or not the regenerative braking force can be used. The hydraulic pressure switching unit 10 switches the hydraulic pressure path 7 so that the service brake 8d is operated with the above-mentioned first hydraulic pressure when the regenerative braking force can be used, and the service brake 8d is operated with a second hydraulic pressure higher than the first hydraulic pressure when the regenerative braking force cannot be used.

[0026] 1 includes a hydraulic pressure switching unit 10 including a low pressure path 11, a high pressure path 12, and a controller 20. The low pressure path 11 is a hydraulic path for hydraulic oil configured so that the hydraulic pressure for operating the service brake 8d is a first hydraulic pressure. The high pressure path 12 is a hydraulic path for hydraulic oil configured so that the hydraulic pressure for operating the service brake 8d is a second hydraulic pressure.

[0027] The low pressure path 11 has a pressure reducing valve 13. The pressure reducing valve 13 is a valve for reducing the hydraulic pressure in the master cylinder 8b generated in response to depression of the brake pedal 8a. The hydraulic oil passing through the low pressure path 11 is reduced to a first hydraulic pressure by the pressure reducing valve 13.

[0028] The high-pressure path 12 connects the upstream and downstream of the low-pressure path 11 so as to bypass the pressure reducing valve 13. The high-pressure path 12 has a solenoid valve 14. The solenoid valve 14 is a valve for switching between allowing and not allowing the flow of hydraulic oil through the high-pressure path 12, and is controlled by, for example, a controller 20.

[0029] When closed, the solenoid valve 14 blocks the flow of hydraulic oil through the high-pressure path 12. When the solenoid valve 14 is closed, the hydraulic oil flows through the low-pressure path 11, and the reduced first hydraulic pressure is transmitted to the service brake 8d.

[0030] The solenoid valve 14 does not have a pressure reducing function like the pressure reducing valve 13. When the solenoid valve 14 is open, it allows the flow of hydraulic oil through the high pressure path 12. When the solenoid valve 14 is open, the hydraulic pressure in the master cylinder 8b generated in response to depression of the brake pedal 8a is transmitted to the service brake 8d as a second hydraulic pressure.

[0031] FIG. 3 is a diagram showing an example of the regenerative braking force and the mechanical braking force when the regenerative braking force cannot be used. The horizontal axis of FIG. 3 is the depression force of the brake pedal 8a, and the vertical axis is the overall braking force in the industrial vehicle 1. As shown in FIG. 3, in the industrial vehicle 1, the output of the mechanical braking force relative to the depression force of the brake pedal 8a is set in advance so that the mechanical braking force B3 is obtained when the regenerative braking force cannot be used. In the example of FIG. 3, when the brake pedal 8a is depressed with a predetermined depression force or more, a mechanical braking force B3 larger than the mechanical braking force B1 is generated, and the two are set to increase according to the depression force. The hydraulic pressure that operates the service brake 8d so as to generate the mechanical braking force B3 exemplified in FIG. 3 is the second hydraulic pressure.

[0032] The controller 20 closes the solenoid valve 14 when the regenerative braking force can be used, and opens the solenoid valve 14 when the regenerative braking force cannot be used. The controller 20 is an electronic control unit that controls the brake system 8 of the industrial vehicle 1. The controller 20 has a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a CAN (Controller Area Network) communication circuit, and the like. For example, the controller 20 loads a program stored in the ROM into the RAM and executes the program loaded into the RAM by the CPU to realize various functions. The controller 20 may be composed of multiple electronic control units.

[0033] The controller 20 may calculate a first pseudo vehicle speed based on the result obtained by the first vehicle speed sensor 9a and the theoretical tire diameter of the front wheels 2. The first pseudo vehicle speed is the vehicle speed of the industrial vehicle 1 estimated from the rotation speed of the front wheels 2. The theoretical tire diameter of the front wheels 2 means, for example, the tire diameter as a design value or a specification value of the front wheels 2. The controller 20 calculates the first pseudo vehicle speed from, for example, the rotation speed of the travel motor 5 obtained by the first vehicle speed sensor 9a, the reduction ratio of the drive system 6, and the theoretical tire diameter of the front wheels 2.

[0034] The controller 20 acquires the battery charging rate, for example, based on battery information from the battery 4. The controller 20 acquires the battery temperature, for example, based on battery information from the battery 4. The controller 20 acquires the state of the motor rotation speed sensor, for example, based on motor information from the travel motor 5. The controller 20 determines whether or not the regenerative braking force can be utilized, based on at least one of the battery charging rate, the battery temperature, and the state of the motor rotation speed sensor.

[0035] For example, when the battery charging rate is equal to or higher than a predetermined full charge threshold, the controller 20 determines that the regenerative braking force cannot be utilized because the battery 4 is in a fully charged state and cannot accept regenerative power. The controller 20 may determine that the regenerative braking force can be utilized when the battery charging rate is lower than a predetermined full charge threshold.

[0036] For example, when the battery temperature is equal to or higher than a predetermined high temperature threshold, or when the battery temperature is equal to or lower than a predetermined low temperature threshold, the controller 20 determines that the battery is exposed to high or low temperature, causing the battery protection function to function, and that the regenerative braking force cannot be utilized. The controller 20 may determine that the regenerative braking force can be utilized when the battery temperature is higher than the low temperature threshold and lower than the high temperature threshold.

[0037] The controller 20 may determine that the regenerative braking force cannot be utilized if an abnormality occurs in the motor rotation speed sensor based on the motor state.

[0038] The full charge threshold is a battery charge rate threshold for determining whether regenerative braking force cannot be used. The high temperature threshold and the low temperature threshold are battery temperature thresholds for determining whether regenerative braking force cannot be used. The full charge threshold, the high temperature threshold, and the low temperature threshold can be set in advance, for example, by testing or simulation of an actual vehicle.

[0039] Fig. 4 is a flowchart showing an example of the process of the controller. The process of the flowchart shown in Fig. 4 is executed repeatedly at predetermined calculation intervals while the industrial vehicle 1 is traveling, for example.

[0040] In S10, the controller 20 of the industrial vehicle 1 acquires the battery charging rate. The controller 20 acquires the battery charging rate based on battery information from the battery 4, for example.

[0041] In S11, the controller 20 acquires the battery temperature. The controller 20 acquires the battery temperature based on battery information from the battery 4, for example.

[0042] In S12, the controller 20 acquires the motor state. The controller 20 acquires the state of the motor rotation speed sensor based on motor information from the traveling motor 5, for example.

[0043] In S13, the controller 20 determines whether or not the regenerative braking force can be used. If it is determined that the regenerative braking force can be used (S13: YES), in S14, the controller 20 operates the service brake 8d at the first hydraulic pressure. The controller 20 closes, for example, the solenoid valve 14. As a result, the solenoid valve 14 blocks the flow of hydraulic oil in the high-pressure path 12, so that the hydraulic oil is reduced in pressure through the pressure reducing valve 13 in the low-pressure path 11, and the service brake 8d operates at the first hydraulic pressure. Thereafter, the controller 20 ends the processing of FIG. 4.

[0044] On the other hand, if it is determined that the regenerative braking force cannot be used (S13: NO), in S15, the controller 20 operates the service brake 8d at a second hydraulic pressure higher than the first hydraulic pressure. The controller 20 opens, for example, the solenoid valve 14. As a result, the solenoid valve 14 allows the hydraulic oil to flow through the high-pressure path 12, so that the hydraulic oil passes through the high-pressure path 12 and bypasses the pressure reducing valve 13, and the service brake 8d operates at the second hydraulic pressure. After that, the controller 20 ends the processing of FIG. 4.

[0045] According to the industrial vehicle 1 configured as described above, the service brake 8d operates with a first hydraulic pressure when the regenerative braking force can be used, and operates with a second hydraulic pressure higher than the first hydraulic pressure when the regenerative braking force cannot be used, in response to switching of the hydraulic path by the hydraulic pressure switching unit 10. As a result, as shown by the mechanical braking force B3 in Fig. 3, the mechanical braking force increases according to the second hydraulic pressure, and the braking force that is reduced when the regenerative braking force cannot be used can be compensated for. Therefore, in an industrial vehicle that can use both regenerative braking force and mechanical braking force, it is possible to suppress the reduction in braking force when the regenerative braking force cannot be used.

[0046] In a configuration in which mechanical braking force is generated in response to the brake pedal force according to the brake operation of the worker (occupant) as in the above-mentioned industrial vehicle 1, if the mechanical braking force remains the same when regenerative braking force cannot be used (same as when regenerative braking force is used in combination), the overall braking force must be made equal to the set braking force when regenerative braking force is used in combination, which may increase the operational burden on the worker. In this regard, according to the industrial vehicle 1, when regenerative braking force cannot be used, the mechanical braking force increases and the decrease in braking force is suppressed, thereby suppressing the increase in the operational burden on the worker.

[0047] In the industrial vehicle 1, the low pressure path 11 has a pressure reducing valve 13, and the high pressure path 12 connects the upstream and downstream of the low pressure path 11 so as to bypass the pressure reducing valve 13, and has a solenoid valve 14. The hydraulic switching unit 10 has a controller 20 that closes the solenoid valve 14 when the regenerative braking force can be used, and opens the solenoid valve 14 when the regenerative braking force cannot be used. As a result, for example, when the regenerative braking force can be used, the solenoid valve 14 closed by the controller 20 blocks the flow of hydraulic oil in the high pressure path 12, so that the hydraulic oil is reduced in pressure through the pressure reducing valve 13 in the low pressure path 11. When the regenerative braking force cannot be used, the solenoid valve 14 opened by the controller 20 allows the flow of hydraulic oil in the high pressure path 12, so that the hydraulic oil bypasses the pressure reducing valve 13 through the high pressure path 12. In this way, the hydraulic path 7 can be switched so that the service brake 8d operates at a first hydraulic pressure when regenerative braking force is available, and operates at a second hydraulic pressure higher than the first hydraulic pressure when regenerative braking force is not available.

[0048] [Variations] The present invention is not limited to the above-described embodiment. The present invention can be implemented in various forms including the above-described embodiment and various modifications and improvements based on the knowledge of those skilled in the art.

[0049] In the above embodiment, there is no particular limitation as to whether the solenoid valve 14 is normally open or not. For example, the solenoid valve 14 may be a normally open solenoid valve that allows the hydraulic oil in the high pressure path 12 to flow when not energized, and the hydraulic switching unit 10 may be configured to energize the solenoid valve 14 when the regenerative braking force can be used, and not energize the solenoid valve 14 when the regenerative braking force cannot be used. This function of energization may be realized without the controller 20, and for example, energization to the solenoid valve 14 may be realized by energization linked to regeneration using a physical electric circuit or the like. In this case, for example, when the regenerative braking force can be used, the solenoid valve 14 energized by the hydraulic switching unit 10 closes to block the flow of the hydraulic oil in the high pressure path 12, so that the hydraulic oil is reduced in pressure through the pressure reducing valve 13 in the low pressure path 11. On the other hand, when the regenerative braking force cannot be used, this means that a failure of the controller 20 or a failure of a physical electric circuit linked to regeneration occurs at the same time, and therefore energization to the solenoid valve 14 is not possible. As a result, the normally open solenoid valve 14 opens when the hydraulic pressure switching unit 10 is not energized, allowing the hydraulic oil to flow through the high pressure path 12, so that the hydraulic oil bypasses the pressure reducing valve 13 through the high pressure path 12. In this way, the hydraulic pressure path 7 can be switched so that the service brake 8d operates with a first hydraulic pressure when the regenerative braking force can be used, and operates with a second hydraulic pressure higher than the first hydraulic pressure when the regenerative braking force cannot be used. Note that, when using a physical electric circuit or the like linked to regeneration, the function of the controller 20 that closes the solenoid valve 14 when the regenerative braking force can be used and opens the solenoid valve 14 when the regenerative braking force cannot be used is not essential.

[0050] In the above embodiment, the hydraulic path 7 branches from one master cylinder 8b into the low pressure path 11 and the high pressure path 12, and the hydraulic switching unit 10 has the pressure reducing valve 13 of the low pressure path 11 and the solenoid valve 14 of the high pressure path 12, but is not limited to this example. A master cylinder generating different hydraulic pressures may be provided in each of the low pressure path and the high pressure path. For example, FIG. 5 is a schematic configuration diagram illustrating an industrial vehicle according to a second embodiment. In FIG. 5, the hydraulic switching unit 10A includes a low pressure path 11A having a low pressure master cylinder (first master cylinder) 15 and a low pressure side switching valve (first switching valve) 16, and a high pressure path 12A having a high pressure master cylinder (second master cylinder) 17 and a high pressure side switching valve (second switching valve) 18. The low pressure master cylinder 15 is a master cylinder that generates a first hydraulic pressure. The low pressure side switching valve 16 is a switching valve that switches the flow of hydraulic oil in the low pressure path 11A. The high-pressure master cylinder 17 is a master cylinder that generates the second hydraulic pressure. The high-pressure side switching valve 18 is a switching valve that switches the flow of hydraulic oil in the high-pressure path 12A. The hydraulic pressure switching unit 10A also has a controller 20A that controls the low-pressure side switching valve 16 and the high-pressure side switching valve 18 so that the service brake 8d is operated using the low-pressure master cylinder 15 when the regenerative braking force can be used, and the service brake 8d is operated using the high-pressure master cylinder 17 when the regenerative braking force cannot be used.

[0051] For example, when the regenerative braking force can be used, the controller 20A controls the low-pressure side switching valve 16 and the high-pressure side switching valve 18 so as to operate the service brake 8d with the first hydraulic pressure using the low-pressure master cylinder 15. FIG. 6 is a schematic diagram showing the state of the first switching valve and the second switching valve when the service brake is operated using the first master cylinder. As shown in FIG. 5 and FIG. 6, when the regenerative braking force can be used, the controller 20A moves the spool 16a of the low-pressure side switching valve 16 to the first position P1 so as to circulate the hydraulic oil of the first hydraulic pressure generated in the low-pressure master cylinder 15 in the low-pressure path 11A to the hydraulic path 7 on the service brake 8d side. When the regenerative braking force can be used, the controller 20A moves the spool 18a of the high-pressure side switching valve 18 to the first position Q1 so as to circulate the hydraulic oil pushed out by the high-pressure master cylinder 17 in the high-pressure path 12A to the return path 9 on the reservoir tank 8c side. As a result, the low-pressure side switching valve 16 is switched to allow the flow of hydraulic oil in the low-pressure path 11A to the service brake 8d, and the high-pressure side switching valve 18 is switched to allow the flow of hydraulic oil in the high-pressure path 12A in the opposite direction to the low-pressure side switching valve 16, and the service brake 8d is operated using the low-pressure master cylinder 15.

[0052] On the other hand, when the regenerative braking force cannot be used, the controller 20A controls the low-pressure side switching valve 16 and the high-pressure side switching valve 18 so as to operate the service brake 8d with the second hydraulic pressure using the high-pressure master cylinder 17. FIG. 7 is a schematic diagram showing the state of the first switching valve and the second switching valve when the service brake is operated using the second master cylinder. As shown in FIG. 5 and FIG. 7, when the regenerative braking force cannot be used, the controller 20A moves the spool 16a of the low-pressure side switching valve 16 to the second position P2 so as to circulate the hydraulic oil pushed out by the low-pressure master cylinder 15 in the low-pressure path 11A to the return path 9 on the reservoir tank 8c side. When the regenerative braking force cannot be used, the controller 20A moves the spool 18a of the high-pressure side switching valve 18 to the second position Q2 so as to circulate the hydraulic oil of the second hydraulic pressure generated in the high-pressure master cylinder 17 in the high-pressure path 12A to the hydraulic path 7 on the service brake 8d side. As a result, the low-pressure side switching valve 16 is switched so as not to allow the hydraulic oil in the low-pressure path 11A to flow to the service brake 8d, and the high-pressure side switching valve 18 is switched so as to allow the flow of hydraulic oil in the high-pressure path 12A to be reversed from that of the low-pressure side switching valve 16, and the service brake 8d is operated using the high-pressure master cylinder 17.

[0053] According to the second embodiment of Figures 5 to 7, the hydraulic path 7 can be switched so that the service brake 8d operates at a first hydraulic pressure when the regenerative braking force can be used, and the service brake 8d operates at a second hydraulic pressure higher than the first hydraulic pressure when the regenerative braking force cannot be used.

[0054] In the above embodiment, the service brake 8d is configured to brake the front wheels 2. However, the service brake 8d may brake the rear wheels 3 in addition to or instead of the front wheels 2.

[0055] In the above embodiment, an electric forklift is shown as the industrial vehicle 1 equipped with the braking control device 100 for the industrial vehicle, but the present invention is not limited to this example. For example, the industrial vehicle may be other industrial vehicles such as a towing vehicle, a transport vehicle, and a towing tractor. [Explanation of symbols]

[0056] 1...industrial vehicle, 5...travel motor, 7...hydraulic path, 8d...service brake, 10,10A...hydraulic switching unit, 11,11A...low pressure path, 12,12A...high pressure path, 13...pressure reducing valve, 14...solenoid valve, 15...low pressure master cylinder (first master cylinder), 16...low pressure side switching valve (first switching valve), 17...high pressure master cylinder (second master cylinder), 18...high pressure side switching valve (second switching valve), 20,20A...controller.

Claims

1. An industrial vehicle equipped with a travel motor that generates a regenerative braking force and a hydraulic service brake that generates a mechanical braking force, a low-pressure path that is a hydraulic path for hydraulic oil configured so that a hydraulic pressure for operating the service brake is a predetermined first hydraulic pressure; a high-pressure path that is a hydraulic path for hydraulic oil configured so that a hydraulic pressure for operating the service brake is a predetermined second hydraulic pressure higher than the first hydraulic pressure; and a hydraulic switching unit that switches the hydraulic path so that the service brake is operated with the first hydraulic pressure when the regenerative braking force can be utilized, and the service brake is operated with the second hydraulic pressure when the regenerative braking force cannot be utilized.

2. the low pressure path has a pressure reducing valve; the high-pressure path connects the upstream and downstream of the low-pressure path so as to bypass the pressure reducing valve, and has a normally-open solenoid valve that allows the flow of hydraulic oil when not energized; 2. The industrial vehicle according to claim 1, wherein the hydraulic pressure switching unit energizes the solenoid valve when the regenerative braking force is available, and does not energize the solenoid valve when the regenerative braking force is unavailable.

3. the low pressure path has a pressure reducing valve; the high-pressure path connects the upstream and downstream of the low-pressure path so as to bypass the pressure reducing valve, and has a solenoid valve; 3. The industrial vehicle according to claim 1, wherein the hydraulic pressure switching unit has a controller that closes the solenoid valve when the regenerative braking force is available and opens the solenoid valve when the regenerative braking force is unavailable.

4. The low pressure path includes a first master cylinder that generates the first hydraulic pressure and a first switching valve that switches whether or not to allow the flow of hydraulic oil, The high pressure path includes a second master cylinder that generates the second hydraulic pressure, and a second switching valve that switches the flow of hydraulic oil to be reverse to that of the first switching valve, 2. The industrial vehicle according to claim 1, wherein the hydraulic switching unit has a controller that controls the first switching valve and the second switching valve so as to operate the service brake using the first master cylinder when the regenerative braking force is available, and to operate the service brake using the second master cylinder when the regenerative braking force is not available.

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