Industrial vehicles

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 Art

[0002] Conventionally, as a technology related to braking of an industrial vehicle, there is known an industrial vehicle including a traveling motor that generates regenerative braking force and a mechanical brake that operates by fluid pressure to generate mechanical braking force as a braking unit (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] <00​​​​​​​​​​​One aspect of the present invention is an industrial vehicle comprising a drive motor that generates regenerative braking force and a hydraulic service brake that generates mechanical braking force, comprising: a low-pressure path which is a hydraulic fluid path configured such that the hydraulic pressure for operating the service brake is a predetermined first hydraulic pressure; a high-pressure path which is a hydraulic fluid path configured such that the hydraulic pressure for operating the service brake is a predetermined second hydraulic pressure that is higher than the first hydraulic pressure; and a hydraulic switching unit that switches the hydraulic path so as to operate the service brake with the first hydraulic pressure when regenerative braking force is available and operate the service brake with the second hydraulic pressure when regenerative braking force is not available.

[0007] In an industrial vehicle according to one aspect of the present invention, in response to the switching of the hydraulic path by the hydraulic switching unit, the service brake operates with a first hydraulic pressure when regenerative braking force can be used, and operates with a second hydraulic pressure higher than the first hydraulic pressure when regenerative braking force cannot be used. As a result, the mechanical braking force increases in accordance with the second hydraulic pressure, and the braking force that is reduced when 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 regenerative braking force cannot be used.

[0008] 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 to bypass the pressure reducing valve, and has a normally-open solenoid valve that allows the flow of hydraulic fluid when not energized, and the hydraulic switching unit energizes the solenoid valve when regenerative braking force is available, and does not energize the solenoid valve when regenerative braking force is not available. For example, when regenerative braking force is available, the solenoid valve energized by the hydraulic switching unit closes, blocking the flow of hydraulic fluid in the high-pressure path, so that the hydraulic fluid is reduced in pressure through the pressure reducing valve in the low-pressure path. When regenerative braking force is not available, the normally-open solenoid valve opens because it is not energized by the hydraulic switching unit, allowing the flow of hydraulic fluid in the high-pressure path, so that the hydraulic fluid 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 at a first hydraulic pressure when regenerative braking force is available, and at a second hydraulic pressure higher than the first hydraulic pressure when regenerative braking force is not available.

[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 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 regenerative braking force is available and opens the solenoid valve when regenerative braking force is not available. For example, when regenerative braking force is available, the solenoid valve closed by the controller blocks the flow of hydraulic fluid in the high-pressure path, so the hydraulic fluid is reduced in pressure through the pressure reducing valve in the low-pressure path. When regenerative braking force is not available, the solenoid valve opened by the controller allows the flow of hydraulic fluid in the high-pressure path, so the hydraulic fluid 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 at a first hydraulic pressure when regenerative braking force is available, and at a second hydraulic pressure higher than the first hydraulic pressure when regenerative braking force is not available.

[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 fluid, and 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 fluid to the opposite direction to that of the first switching valve, and the hydraulic switching unit may have 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 regenerative braking force is available, and to operate the service brake using the second master cylinder when regenerative braking force is not available. For example, when regenerative braking force is available, the controller controls the first switching valve and the second switching valve so as to operate the service brake with the first hydraulic pressure using the first master cylinder. When regenerative braking force is not available, the controller controls the first switching valve and the second switching valve so as to operate the service brake 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 that is higher than the first hydraulic pressure when regenerative braking force is not available. [Effects of the Invention]

[0011] According to one aspect of the present invention, 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 regenerative braking force cannot be used. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram illustrating an industrial vehicle according to the first embodiment. [Figure 2] This figure shows an example of regenerative braking force and mechanical braking force when regenerative braking force can be used. [Figure 3] This figure shows an example of regenerative braking force and mechanical braking force when regenerative braking force cannot be used. [Figure 4] This is a flowchart showing an example of controller processing. [Figure 5] This is a schematic diagram illustrating an industrial vehicle according to the second embodiment. [Figure 6] This is a schematic diagram showing the state of the first and second switching valves when the service brake is operated using the first master cylinder. [Figure 7] This is a schematic diagram showing the state of the first and second switching valves when the service brake is operated using the second master cylinder. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant descriptions will be omitted.

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

[0015] As shown in Fig. 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 circuit 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 disposed at the front portion of the vehicle body of the industrial vehicle 1, and 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 vehicle body of the industrial vehicle 1 where a load handling device including a mast and forks is provided. The rear wheels 3 are wheels disposed at the rear portion of the vehicle body of the industrial vehicle 1, and for example, a pair of left and right steering wheels.

[0017] The battery 4 is a power source that outputs DC power. As the battery 4, for example, a secondary battery such as a lead-acid battery or a lithium-ion battery is used. 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, the battery charge rate and the battery temperature to the controller 20.

[0018] The traveling motor 5 is a motor generator for traveling of the industrial vehicle 1. The traveling motor 5 is, for example, a three-phase AC rotating electric motor. The traveling motor 5 generates a driving force in response to the power supply from the battery 4. When the regenerative braking force can be utilized, the traveling motor 5 generates a 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. <s

[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 gear for speed reduction 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 the hydraulic pressure generated by the operator's brake operation along the 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 includes a traveling motor 5 that generates regenerative braking force and a hydraulic service brake 8d that generates mechanical braking force.

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

[0022] When the brake pedal 8a is depressed, hydraulic pressure is generated by the piston rod and piston inside the master cylinder 8b pushing the hydraulic oil from the reservoir tank 8c. The hydraulic pressure generated in the master cylinder 8b is transmitted to the service brake 8d through the hydraulic oil along the hydraulic path 7, and the service brake 8d operates. Thereby, the front wheels 2 are braked.

[0023] In industrial vehicle 1, the output of regenerative braking force and mechanical braking force in relation to the force applied to the brake pedal 8a is predetermined so that when regenerative braking force is available, the regenerative braking force and mechanical braking force are used in combination to obtain a set braking force (a predetermined braking force) as a whole. Figure 2 shows an example of regenerative braking force and mechanical braking force when regenerative braking force is available. In Figure 2, the horizontal axis represents the force applied to the brake pedal 8a, and the vertical axis represents the total braking force in industrial vehicle 1. As shown in Figure 2, in industrial vehicle 1, when regenerative braking force is available, the braking force in relation to the force applied to the brake pedal 8a 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. As in the example in Figure 2, when the brake pedal 8a is first pressed, only the regenerative braking force Brc may be generated initially. When the brake pedal 8a is pressed with a force greater than the predetermined force, the mechanical braking force B1 and the regenerative braking force Brc may increase in accordance with the force applied.

[0024] The mechanical braking force B1 in Figure 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 regenerative braking force is available. The first hydraulic pressure is determined according to the hydraulic path 7 and the brake system 8. Therefore, for example, if regenerative braking force is not available, a greater brake pedal force is required to generate the same braking force as when regenerative braking force is available.

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

[0026] As a specific example, the industrial vehicle 1 in Figure 1 includes a hydraulic switching unit 10 comprising a low-pressure path 11, a high-pressure path 12, and a controller 20. The low-pressure path 11 is a hydraulic fluid path configured such that the hydraulic pressure used to operate the service brake 8d becomes the first hydraulic pressure. The high-pressure path 12 is a hydraulic fluid path configured such that the hydraulic pressure used to operate the service brake 8d becomes the second hydraulic pressure.

[0027] The low-pressure path 11 includes a pressure reducing valve 13. The pressure reducing valve 13 is a valve for reducing the hydraulic pressure in the master cylinder 8b that is generated in response to the depressing of the brake pedal 8a. The hydraulic fluid that has passed 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, bypassing the pressure reducing valve 13. The high-pressure path 12 has a solenoid valve 14. The solenoid valve 14 is a valve for switching the flow of hydraulic fluid through the high-pressure path 12, and is controlled, for example, by a controller 20.

[0029] When the solenoid valve 14 is closed, it blocks the flow of hydraulic fluid in the high-pressure path 12. When the solenoid valve 14 is closed, the hydraulic fluid flows through the low-pressure path 11, and the reduced pressure of the 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 fluid in the high-pressure path 12. When the solenoid valve 14 is open, the hydraulic pressure in the master cylinder 8b generated in response to the depressing of the brake pedal 8a is transmitted to the service brake 8d as a second hydraulic pressure.

[0031] Figure 3 shows an example of regenerative braking force and mechanical braking force when regenerative braking force cannot be used. The horizontal axis in Figure 3 represents the force applied to the brake pedal 8a, and the vertical axis represents the total braking force in the industrial vehicle 1. As shown in Figure 3, in the industrial vehicle 1, the output of mechanical braking force in response to the force applied to the brake pedal 8a is pre-set so that mechanical braking force B3 is obtained when regenerative braking force cannot be used. In the example in Figure 3, when the brake pedal 8a is pressed with a force greater than a predetermined force, a mechanical braking force B3 greater than mechanical braking force B1 is generated, and each is set to increase in proportion to the force applied. The hydraulic pressure that operates the service brake 8d to generate the mechanical braking force B3 exemplified in Figure 3 is the second hydraulic pressure.

[0032] The controller 20 closes the solenoid valve 14 when regenerative braking force is available and opens the solenoid valve 14 when regenerative braking force is not available. The controller 20 is an electronic control unit that controls the brake system 8 of the industrial vehicle 1. The controller 20 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), CAN (Controller Area Network) communication circuit, etc. The controller 20 realizes various functions, for example, by loading a program stored in ROM into RAM and executing the program loaded into RAM with the CPU. 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 results obtained from the first vehicle speed sensor 9a and the theoretical tire diameter of the front wheel 2. The first pseudo-vehicle speed is the vehicle speed of the industrial vehicle 1 estimated from the rotational speed of the front wheel 2. The theoretical tire diameter of the front wheel 2 means, for example, the tire diameter of the front wheel 2 as a design value or specification value. For example, the controller 20 calculates the first pseudo-vehicle speed from the rotational speed of the drive 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 wheel 2.

[0034] The controller 20 obtains the battery charge rate based on battery information from the battery 4, for example. The controller 20 obtains the battery temperature based on battery information from the battery 4, for example. The controller 20 obtains the status of the motor speed sensor based on motor information from the drive motor 5, for example. The controller 20 determines whether regenerative braking force can be used based on at least one of the battery charge rate, battery temperature, and motor speed sensor status.

[0035] For example, if the battery charge level is above a predetermined full charge threshold, the controller 20 determines that regenerative braking cannot be used because the battery 4 is fully charged and cannot accept regenerative power. The controller 20 may also determine that regenerative braking can be used if the battery charge level is below a predetermined full charge threshold.

[0036] The controller 20 determines, for example, that if the battery temperature is above a predetermined high-temperature threshold, or below a predetermined low-temperature threshold, the battery is exposed to high or low temperatures, triggering a battery protection function, and therefore regenerative braking cannot be used. The controller 20 may also determine that regenerative braking can be used if the battery temperature is greater than the low-temperature threshold and less than the high-temperature threshold.

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

[0038] The full charge threshold is a battery charge level threshold used to determine when regenerative braking cannot be utilized. The high temperature threshold and low temperature threshold are battery temperature thresholds used to determine when regenerative braking cannot be utilized. The full charge threshold, high temperature threshold, and low temperature threshold can be preset, for example, through actual vehicle testing or simulation.

[0039] Figure 4 is a flowchart illustrating an example of controller processing. The processing shown in the flowchart in Figure 4 is repeatedly executed, for example, at predetermined calculation cycles while the industrial vehicle 1 is in motion.

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

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

[0042] In S12, the controller 20 acquires the motor status. For example, the controller 20 acquires the status of the motor rotation speed sensor based on motor information from the travel motor 5.

[0043] In S13, the controller 20 determines whether or not regenerative braking force can be used. If it is determined that 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 fluid in the high-pressure path 12, causing the hydraulic fluid to be 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. After that, the controller 20 completes the process shown in Figure 4.

[0044] On the other hand, if it is determined that 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 fluid to flow through the high-pressure path 12, so the hydraulic fluid passes through the high-pressure path 12, bypassing the pressure reducing valve 13, and the service brake 8d operates at the second hydraulic pressure. After that, the controller 20 completes the process shown in Figure 4.

[0045] In the industrial vehicle 1 configured as described above, the service brake 8d operates with a first hydraulic pressure when regenerative braking force is available, in response to the switching of the hydraulic path by the hydraulic switching unit 10, and operates with a second hydraulic pressure higher than the first hydraulic pressure when regenerative braking force is not available. As a result, the mechanical braking force increases in accordance with the second hydraulic pressure, as shown in the mechanical braking force B3 in Figure 3, and can compensate for the reduced braking force when regenerative braking force is not available. 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 regenerative braking force is not available.

[0046] Furthermore, in a configuration like the industrial vehicle 1 described above, where mechanical braking force is generated in response to the brake pedal pressure applied by the operator (occupant) in accordance with their brake operation, if the mechanical braking force remains unchanged (equivalent to when regenerative braking force is used in combination) when regenerative braking force cannot be utilized, there is a risk that the operator's operational burden will increase in order to maintain the overall braking force at the same level as the set braking force when regenerative braking force is used in combination. In this regard, with industrial vehicle 1, when regenerative braking force cannot be utilized, the mechanical braking force increases to suppress the decrease in braking force, thereby suppressing the increase in the operator's operational burden.

[0047] In 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 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 regenerative braking force is available and opens the solenoid valve 14 when regenerative braking force is not available. As a result, for example, when regenerative braking force is available, the solenoid valve 14 closed by the controller 20 blocks the flow of hydraulic fluid in the high-pressure path 12, so the hydraulic fluid is reduced in pressure by passing through the pressure reducing valve 13 in the low-pressure path 11. When regenerative braking force is not available, the solenoid valve 14 opened by the controller 20 allows the flow of hydraulic fluid in the high-pressure path 12, so the hydraulic fluid bypasses the pressure reducing valve 13 by passing through the high-pressure path 12. In this way, the hydraulic path 7 can be switched so that the service brake 8d 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.

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

[0049] In the above embodiment, there is no particular limitation on 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 flow of hydraulic fluid in the high-pressure path 12 when it is not energized, and the hydraulic switching unit 10 may be configured to energize the solenoid valve 14 when regenerative braking force is available, and not energize the solenoid valve 14 when regenerative braking force is not available. This energizing function may be realized without the controller 20, and for example, the presence or absence of energization to the solenoid valve 14 may be realized by energizing in conjunction with regeneration using a physical electrical circuit or the like. In this case, for example, when regenerative braking force is available, the solenoid valve 14 energized by the hydraulic switching unit 10 closes, blocking the flow of hydraulic fluid in the high-pressure path 12, so that the hydraulic fluid is depressurized through the pressure reducing valve 13 in the low-pressure path 11. On the other hand, when regenerative braking force is not available, this means that a failure of the controller 20 or a failure of a physical electrical circuit or the like linked to regeneration occurs, making it impossible to energize the solenoid valve 14. As a result, the normally open solenoid valve 14 opens because it is not energized by the hydraulic switching unit 10, allowing the hydraulic fluid to flow through the high-pressure path 12, thus bypassing 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 the first hydraulic pressure when regenerative braking force is available, and operates at the second hydraulic pressure, which is higher than the first hydraulic pressure, when regenerative braking force is not available. Note that when using a physical electrical circuit linked to regeneration, the function of the controller 20 to close the solenoid valve 14 when regenerative braking force is available and open the solenoid valve 14 when regenerative braking force is not available is not essential.

[0050] In the above embodiment, the hydraulic path 7 branches from one master cylinder 8b into a low-pressure path 11 and a high-pressure path 12, and the hydraulic switching unit 10 has a pressure reducing valve 13 for the low-pressure path 11 and a solenoid valve 14 for the high-pressure path 12, but is not limited to this example. Master cylinders that generate different hydraulic pressures may be provided in the low-pressure path and the high-pressure path, respectively. For example, Figure 5 is a schematic configuration diagram illustrating an industrial vehicle according to the second embodiment. In Figure 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 the first hydraulic pressure. The low-pressure side switching valve 16 is a switching valve that switches the flow of hydraulic fluid 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 fluid in the high-pressure path 12A. The hydraulic 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 regenerative braking force is available, and the service brake 8d is operated using the high-pressure master cylinder 17 when regenerative braking force is not available.

[0051] For example, when regenerative braking force is available, the controller 20A controls the low-pressure side switching valve 16 and the high-pressure side switching valve 18 so that the service brake 8d is operated with the first hydraulic pressure using the low-pressure master cylinder 15. Figure 6 is a schematic configuration diagram showing the state of the first and second switching valves when the service brake is operated using the first master cylinder. As shown in Figures 5 and 6, when regenerative braking force is available, the controller 20A moves the spool 16a of the low-pressure side switching valve 16 to the first position P1 so that the hydraulic fluid of the first hydraulic pressure generated in the low-pressure master cylinder 15 in the low-pressure path 11A flows to the hydraulic path 7 on the service brake 8d side. When regenerative braking force is available, the controller 20A moves the spool 18a of the high-pressure side switching valve 18 to the first position Q1 so that the hydraulic fluid pushed out by the high-pressure master cylinder 17 in the high-pressure path 12A flows 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 hydraulic fluid from the low-pressure path 11A to flow to the service brake 8d, and the high-pressure side switching valve 18 is switched to allow the hydraulic fluid from the high-pressure path 12A to flow in the opposite direction to that of the low-pressure side switching valve 16, so that the service brake 8d is operated using the low-pressure master cylinder 15.

[0052] On the other hand, if 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. Figure 7 is a schematic configuration diagram showing the state of the first and second switching valves when the service brake is operated using the second master cylinder. As shown in Figures 5 and 7, if 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 allow the hydraulic fluid pushed out by the low-pressure master cylinder 15 in the low-pressure path 11A to flow to the return path 9 on the reservoir tank 8c side. If 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 allow the hydraulic fluid of the second hydraulic pressure generated by the high-pressure master cylinder 17 in the high-pressure path 12A to flow to the hydraulic path 7 on the service brake 8d side. As a result, the low-pressure side switching valve 16 is switched so that it does not allow the hydraulic fluid in the low-pressure path 11A to flow to the service brake 8d, and the high-pressure side switching valve 18 is switched so that the flow of hydraulic fluid in the high-pressure path 12A is reversed compared to 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 shown in Figures 5 to 7, the hydraulic path 7 can be switched so that the service brake 8d 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.

[0054] In the above embodiment, the service brake 8d was configured to brake the front wheel 2, but it may also brake the rear wheel 3 in addition to or instead of the front wheel 2.

[0055] In the above embodiment, an electric forklift was shown as the industrial vehicle 1 on which the industrial vehicle braking control device 100 is installed, but the invention is not limited to this example. For example, the industrial vehicle may be other industrial vehicles such as a towing vehicle, transport vehicle, or towing tractor. [Explanation of Symbols]

[0056] 1...Industrial vehicle, 5...Traction motor, 7...Hydraulic path, 8d...Service brake, 10,10A...Hydraulic switching section, 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 comprising a drive motor that generates regenerative braking force and a hydraulic service brake that generates mechanical braking force, A low-pressure path is a hydraulic fluid path for hydraulic fluid configured such that the hydraulic pressure used to operate the service brake becomes a predetermined first hydraulic pressure, A high-pressure path is a hydraulic path for hydraulic fluid configured such that the hydraulic pressure used to operate the service brake becomes a predetermined second hydraulic pressure that is higher than the first hydraulic pressure, An industrial vehicle comprising: a hydraulic switching unit that switches the hydraulic path so as to operate the service brake with the first hydraulic pressure when the regenerative braking force is available, and operate the service brake with the second hydraulic pressure when the regenerative braking force is unavailable.

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 fluid when not energized. The industrial vehicle according to claim 1, wherein the hydraulic switching unit energizes the solenoid valve when the regenerative braking force can be used, and does not energize the solenoid valve when the regenerative braking force cannot be used.

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. The industrial vehicle according to claim 1 or 2, wherein the hydraulic switching unit has 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.

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 fluid. 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 the hydraulic fluid to the opposite direction to that of the first switching valve. 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 unavailable.

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