Forklift safety speed limiting system and forklift

Abstract

This invention discloses a forklift safety speed limiting system, including a safety speed limiting switch, a gearbox control board, and a gear shift lever. The gear shift lever has first and second output ports, and the gearbox control board has first and second input ports. The second output port is electrically connected to the second input port through a first actuator, the first output port is electrically connected to the first input port through a second actuator, and the second output port is electrically connected to the first input port through a third actuator. The opening and closing of the safety speed limiting switch changes the on / off state of the first, second, and third actuators. The first and second actuators are normally closed, and the third actuator is normally open. When a low level is input to the second input port, the gearbox operates in a low gear; when a high level is input to the second input port, the gearbox operates in a high gear. This invention also discloses a forklift with a forklift safety speed limiting system. This invention does not require modification of the vehicle control program or gearbox control program for speed limiting, thus improving forklift safety.

Description

Technical Field

[0001] This invention relates to a speed limiting system, and more particularly to a forklift safety speed limiting system. Background Technology

[0002] Forklifts are mobile machines used in factories, docks, or storage yards. When a forklift is going downhill, its heavy weight and large inertia pose a significant safety hazard, especially when it is in a high gear. The risk is even greater when it is under heavy load. Therefore, when driving a forklift downhill, the speed should be reduced to a low speed to ensure safety.

[0003] In existing technologies, implementing forklift speed limits requires modifying the program. This not only requires OEMs to modify the entire vehicle program, but also necessitates communication with gearbox manufacturers and requesting them to modify the gearbox controller program in accordance with the control requirements transmitted by the OEM. Some gearbox manufacturers have to go through a cumbersome program modification application process to modify their controller program, which is slow and inefficient. Summary of the Invention

[0004] In view of the above-mentioned defects in the prior art, the present invention aims to provide a forklift safety speed limiting system that solves the problem of cumbersome modification required by modifying the whole vehicle program to achieve speed limiting, which necessitates coordination with the gearbox control program.

[0005] The technical solution of this invention is as follows: A forklift safety speed limiting system includes a safety speed limiting switch, a gearbox control board, and a gear lever. The gear lever has a first output port and a second output port. The gearbox control board has a first input port and a second input port. The second output port is electrically connected to the second input port through a first actuator. The first output port is electrically connected to the first input port through a second actuator. The second output port is electrically connected to the first input port through a third actuator. The opening and closing of the safety speed limiting switch is used to change the on / off state of the first actuator, the second actuator, and the third actuator. The first actuator and the second actuator are normally closed, and the third actuator is normally open. When the second input port receives a low level, the gearbox operates in a low gear; when the second input port receives a high level, the gearbox operates in a high gear.

[0006] Furthermore, the low-speed gear includes a first gear and a second gear. When the first input port is input with a high level and the second input port is input with a low level, the transmission executes the first gear. When the first input port is input with a low level and the second input port is input with a low level, the transmission executes the second gear.

[0007] Furthermore, the high-speed gear includes a third gear and a fourth gear. When the first input port is low and the second input port is high, the gearbox operates in the third gear. When the first input port is high and the second input port is high, the gearbox operates in the fourth gear.

[0008] Furthermore, it includes an alarm light circuit, wherein the opening and closing of the safety speed limit switch is used to control the on / off state of the alarm light circuit.

[0009] Furthermore, it includes a first driving unit, a fourth execution unit, and a second driving unit. The opening and closing of the safety speed limit switch is used to control the power supply of the first driving unit. When the first driving unit is energized, it is used to drive the first execution unit and the fourth execution unit to operate. The opening and closing of the safety speed limit switch and the opening and closing of the fourth execution unit are used to jointly control the power supply of the second driving unit. When the second driving unit is energized, it is used to drive the second execution unit and the third execution unit to operate. When the first driving unit is energized, the second driving unit is also energized.

[0010] Furthermore, the first driving unit, the first executing unit, and the fourth executing unit constitute a first control element, the second driving unit, the second executing unit, and the third executing unit constitute a second control element, the first control element and the second control element are relays, the first driving unit and the second driving unit are relay coils, and the first executing unit, the second executing unit, the third executing unit, and the fourth executing unit are relay contacts.

[0011] Furthermore, the device includes a first driving unit, a fourth execution unit, a second driving unit, and a fifth execution unit. The opening and closing of the safety speed limit switch is used to control the power supply to the first driving unit. When the first driving unit is energized, it drives the first execution unit and the fourth execution unit to operate. The opening and closing of the safety speed limit switch and the fourth execution unit are used to jointly control the power supply to the second driving unit. The opening and closing of the safety speed limit switch, the fourth execution unit, and the fifth execution unit are used to jointly control the power supply to the alarm light circuit. When the second driving unit is energized, it drives the second execution unit, the third execution unit, and the fifth execution unit to operate. When the first driving unit is energized, the second driving unit is also energized.

[0012] Furthermore, the first driving unit, the first executing unit, and the fourth executing unit constitute a first control element, and the second driving unit, the second executing unit, the third executing unit, and the fifth executing unit constitute a second control element. The first control element and the second control element are relays, the first driving unit and the second driving unit are relay coils, and the first executing unit, the second executing unit, the third executing unit, the fourth executing unit, and the fifth executing unit are relay contacts.

[0013] Furthermore, it includes a display, which is electrically connected to the transmission control board via a communication line, and the display is used to display the gear position executed by the transmission control board.

[0014] Another technical solution of the present invention is: a forklift having the above-mentioned forklift safety speed limiting system.

[0015] The advantages of this invention compared to the prior art are:

[0016] This invention controls the connection between the first and second output ports of the gear lever and the first and second input ports of the gear lever by adding a controlled actuator between the gearbox control board and the gear lever. By simply pressing a safety speed limit switch, the gear lever signal, which was originally in a high-speed gear, can be reduced to a low-speed gear signal, realizing a one-button gear limiting function. The control method is stable and reliable and does not require modification of the vehicle control program or the gearbox control program. This not only greatly improves the safety of the driver when driving the forklift, reduces driving risks, and reduces the occurrence of accidents, but also eliminates the need for the OEM manufacturer or gearbox manufacturer to modify the control program, making the process quick and efficient.

[0017] One-button operation is not only easy to use and highly reliable, but also effectively avoids accidental operation. Its simple structure and low cost, combined with an alarm circuit and display, allow for alerting personnel to maintain safety by alarming and displaying gear information during speed-limited conditions, further improving driving safety and facilitating operator monitoring. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the control principle of the forklift safety speed limiting system in Example 1.

[0019] Figure 2 This is a schematic diagram of the control principle of the forklift safety speed limiting system in Example 2. Detailed Implementation

[0020] The present invention will be further described below with reference to embodiments, but these are not intended to limit the scope of the invention.

[0021] Example 1, please refer to Figure 1As shown, the forklift safety speed limiting system of this embodiment includes a safety speed limiting switch 100 installed on the armrest box, a first control element, a gearbox control board 101, a gear lever 102, and a display 103.

[0022] The gear lever 102 is used to send gear position signals and includes four gear switches: 1, 2, 3, and 4. Its S-terminal is connected to the power supply. The gear lever 102 is provided with a first output port 102a and a second output port 102b. When the gear lever 102 is selected to a specific gear switch position, the first output port 102a and the second output port 102b will output corresponding high and low level combinations.

[0023] The gear shifting logic of gear lever 102 is:

[0024] When the lever 102 position switch is selected to position 1, the S terminal and the first output port 102a are connected, while the S terminal and the second output port 102b are not connected. That is, the first output port 102a outputs a high level, and the second output port 102b outputs a low level.

[0025] When the lever 102 position switch is selected to position 2, the S terminal and the first output port 102a and the second output port 102b are not conducting, that is, the first output port 102a and the second output port 102b both output a low level.

[0026] When the lever 102 position switch is selected to position 3, the S terminal and the first output port 102a are not connected, while the S terminal and the second output port 102b are connected. That is, the first output port 102a outputs a low level, and the second output port 102b outputs a high level.

[0027] When the lever 102 position switch is selected to position 4, the S terminal and the first output port 102a and the second output port 102b are all turned on, that is, the first output port 102a and the second output port 102b both output a high level.

[0028] The transmission control board 101 receives signals from the first output port 102a and the second output port 102b of the gear lever 102, and it is equipped with a first input port 101b and a second input port 101b. Based on the high and low levels of the first and second input ports 101b, preset logic controls the upshifting and downshifting actions of the transmission. The connection between the first and second input ports 101b of the transmission control board 101 and the first and second output ports 102a and 102b of the gear lever 102 has been changed from a direct connection to a connection via the actuator of the first control element; the specific connection method will be detailed later. Furthermore, the transmission control board 101 also transmits the current gear position status of the transmission to the bus via bus communication.

[0029] Display 103 is used to read and display the current gear status from the bus.

[0030] The safety speed limit switch 100 is used to trigger the safe driving mode and limit the vehicle speed. One end of the safety speed limit switch 100 is connected to the vehicle power line, and the other end is connected to the first drive unit 104 of the first control element. The other end of the first drive unit 104 is connected to the ground wire.

[0031] The first control element is an intermediate relay, which includes a first drive unit 104, a first actuation unit 105, a second actuation unit 106, and a third actuation unit 107. The first drive unit 104 is the coil of the intermediate relay, and the first actuation unit 105, the second actuation unit 106, and the third actuation unit 107 are the contacts of the intermediate relay. When the first drive unit 104 is energized, it controls the operation of the first actuation unit 105, the second actuation unit 106, and the third actuation unit 107.

[0032] In this embodiment, the first actuator 105 is a normally closed contact, with its two ends connected to the second output port 102b of the gear lever 102 and the second input port 101b of the transmission control board 101, respectively. The second actuator 106 is a normally closed contact, with its two ends connected to the first output port 102a of the gear lever 102 and the first input port 101b of the transmission control board 101, respectively. The third actuator 107 is a normally open contact, with its two ends connected to the second output port 102b of the gear lever 102 and the first input port 101b of the transmission control board 101, respectively.

[0033] The control process of this forklift safety speed limiting system during actual use is explained below:

[0034] 1. In the initial state, the safety speed limit switch 100 is in an untriggered state, the first drive unit 104 is de-energized, and the first actuator 105, second actuator 106, and third actuator 107 do not operate. The first actuator 105 and second actuator 106 are in a closed state, and the third actuator 107 is in an open state. The vehicle is in an unsafe speed limit state, at which time:

[0035] When the gear lever 102 is shifted to 1st gear, the first output port 102a outputs a high level, which is then input to the first input port 101b after passing through the second actuator 106. The second output port 102b outputs a low level, which is then input to the second input port 101b after passing through the first actuator 105. The gearbox control board 101 then shifts to 1st gear.

[0036] When the gear lever 102 is shifted to 2nd gear, the first output port 102a outputs a low level, which is then input to the first input port 101b after passing through the second actuator 106. The second output port 102b outputs a low level, which is then input to the second input port 101b after passing through the first actuator 105. The gearbox control board 101 then shifts to 2nd gear.

[0037] When the gear lever 102 is shifted to 3rd gear, the first output port 102a outputs a low level, which is then input to the first input port 101b after passing through the second actuator 106. The second output port 102b outputs a high level, which is then input to the second input port 101b after passing through the first actuator 105. The gearbox control board 101 then shifts to 3rd gear.

[0038] When the gear lever 102 is shifted to 4th gear, the first output port 102a outputs a high level, which is then input to the first input port 101b after passing through the second actuator 106. The second output port 102b outputs a high level, which is then input to the second input port 101b after passing through the first actuator 105. The gearbox control board 101 then shifts to 4th gear.

[0039] Therefore, in this state, the gearbox control board 101 executes the gear exactly according to the position of the gear lever 102.

[0040] 2. When the vehicle is in a high gear, such as 3rd or 4th gear, if the driver needs to limit the speed for safety, simply press the safety speed limit switch 100. The first drive unit 104 is energized, the first actuator 105 and the second actuator 106 are disengaged, and the third actuator 107 is closed. Because the first actuator 105 is disengaged, the second input port 101b remains at a low level regardless of the output of the second output port 102b. Because the second actuator 106 is disengaged and the third actuator 107 is closed, the first input port 101b is disconnected from the first output port 102a and connected to the second output port 102b.

[0041] The gear lever 102 is controlled in each gear position as follows:

[0042] (1) If the gear lever 102 is in 4th gear and the safety speed limit switch 100 is pressed, the second output port 102b is at a high level and is connected to the first input port 101b. The first input port 101b of the transmission control board 101 is at a high level and the second input port 101b is at a low level, so that the actual signal received by the transmission control board 101 corresponds to the signal when the gear lever 102 is in 1st gear, and the vehicle speed will drop to the safe speed state within the range of 1st gear.

[0043] (2) If the gear lever 102 is in 3rd gear and the safety speed limit switch 100 is pressed, the second output port 102b is at a high level and connected to the first input port 101b. The first input port 101b of the transmission control board 101 is at a high level and the second input port 101b is at a low level, so that the actual signal received by the transmission control board 101 corresponds to the signal when the gear lever 102 is in 1st gear, and the vehicle speed will drop to the safe speed state within the range of 1st gear.

[0044] (3) If the gear lever 102 is in 2nd gear and the safety speed limit switch 100 is pressed, the second output port 102b is at a low level and is connected to the first input port 101b. The first input port 101b of the transmission control board 101 is at a low level and the second input port 101b is at a low level, so that the actual signal received by the transmission control board 101 corresponds to the signal when the gear lever 102 is in 2nd gear, and the vehicle speed will be controlled to a safe speed state within the range of 2nd gear.

[0045] (4) If the gear lever 102 is in 1st gear and the safety speed limit switch 100 is pressed, the second output port 102b is low level and connected to the first input port 101b. The first input port 101b of the transmission control board 101 is low level and the second input port 101b is low level, so that the actual signal received by the transmission control board 101 corresponds to the signal when the gear lever 102 is in 2nd gear, and the vehicle speed will be controlled to a safe speed state within the range of 2nd gear.

[0046] 3. When the vehicle does not require a safe speed limit, release the safe speed limit switch 100 to restore the gear logic to the initial state.

[0047] Example 2, please refer to Figure 2 As shown, the forklift safety speed limiting system of this embodiment includes a safety speed limiting switch 200 installed on the armrest box, a first control element, a second control element, a gearbox control board 201, a gear lever 202, a display 203, and an alarm light 204.

[0048] The gear lever 202 is used to send gear position signals, including four gear switches (1, 2, 3, and 4), and its S-terminal is connected to the power supply. The gear lever 202 is equipped with a first output port 202a and a second output port 202b. When the gear lever 202 is selected to a specific gear switch position, the first output port 202a and the second output port 202b will output corresponding high and low level combinations.

[0049] The gear shifting logic of the gear shift lever 202 is the same as that in Embodiment 1, and will not be described again.

[0050] The transmission control board 201 receives signals from the first output port 202a and the second output port 202b of the gear lever 202, and it is equipped with a first input port 201a and a second input port 201b. Based on the high and low levels of the first input port 201a and the second input port 201b, preset logic controls the upshifting and downshifting actions of the transmission. The connection between the first input port 201a and the second input port 201b of the transmission control board 201 and the first output port 202a and the second output port 202b of the gear lever 202 has been changed from a direct connection to a connection via the actuator of the first control element; the specific connection method will be detailed later. In addition, the transmission control board 201 also transmits the current gear position status of the transmission to the bus via bus communication.

[0051] Display 203 is used to read the current gear status from the bus and display it.

[0052] The safety speed limiter switch 200 is used to trigger the safe driving mode and limit the vehicle speed. One end of the safety speed limiter switch 200 is connected to the vehicle power line, and the other end is connected to the first drive unit 205 of the first control element. The other end of the first drive unit 205 is connected to the ground wire. The safety speed limiter switch 200 is also connected to the fourth actuator 210, which is connected to the second drive unit 206 and the fifth actuator 211 respectively. The other end of the second drive unit 206 is connected to the ground wire, and the fifth actuator 211 is connected to the warning light 204. The safety speed limiter switch 200, the fourth actuator 210, the fifth actuator 211, and the warning light 204 constitute an alarm circuit.

[0053] The first control element is an intermediate relay, which includes a first drive unit 205, a first actuation unit 207, and a fourth actuation unit 210. The first drive unit 205 is the coil of the intermediate relay, and the first actuation unit 207 and the fourth actuation unit 210 are the contacts of the intermediate relay. When the first drive unit 205 is energized, it controls the operation of the first actuation unit 207 and the fourth actuation unit 210.

[0054] The second control element is also an intermediate relay, which includes a second drive unit 206, a second actuation unit 208, a third actuation unit 209, and a fifth actuation unit 211. The second drive unit 206 is the coil of the intermediate relay, and the second actuation units 208, 209, and 211 are the contacts of the intermediate relay. When the first drive unit 205 is energized, it controls the operation of the second actuation unit 208, 209, and 211.

[0055] In this embodiment, the first actuator 207 is a normally closed contact, with its two ends connected to the second output port 202b of the gear lever 202 and the second input port 201b of the transmission control board 201, respectively. The second actuator 208 is a normally closed contact, with its two ends connected to the first output port 202a of the gear lever 202 and the first input port 201a of the transmission control board 201, respectively. The third actuator 209 is a normally open contact, with its two ends connected to the second output port 202b of the gear lever 202 and the first input port 201a of the transmission control board 201, respectively. The fourth actuator 210 and the fifth actuator 211 are normally open contacts.

[0056] The control process of this forklift safety speed limiting system during actual use is explained below:

[0057] 1. In the initial state, the safety speed limit switch 200 is in an untriggered state, the first drive unit 205 and the second drive unit 206 are de-energized, and the first actuator 207, the second actuator 208, the third actuator 209, the fourth actuator 210, and the fifth actuator 211 do not operate. The first actuator 207 and the second actuator 208 are in a closed state, while the third actuator 209, the fourth actuator 210, and the fifth actuator 211 are in a disconnected state. The vehicle is in an unsafe speed limit state, at which time:

[0058] When the gear lever 202 is shifted to 1st gear, the first output port 202a outputs a high level, which passes through the second actuator 208 and is then input to the first input port 201a. The second output port 202b outputs a low level, which passes through the first actuator 207 and is then input to the second input port 201b. The gearbox control board 201 then shifts to 1st gear.

[0059] When the gear lever 202 is shifted to 2nd gear, the first output port 202a outputs a low level, which passes through the second actuator 208 and is then input to the first input port 201a. The second output port 202b outputs a low level, which passes through the first actuator 207 and is then input to the second input port 201b. The gearbox control board 201 then shifts to 2nd gear.

[0060] When the gear lever 202 is shifted to 3rd gear, the first output port 202a outputs a low level, which passes through the second actuator 208 and is then input to the first input port 201a. The second output port 202b outputs a high level, which passes through the first actuator 207 and is then input to the second input port 201b. The gearbox control board 201 then shifts to 3rd gear.

[0061] When the gear lever 202 is shifted to 4th gear, the first output port 202a outputs a high level, which is then input to the first input port 201a after passing through the second actuator 208. The second output port 202b outputs a high level, which is then input to the second input port 201b after passing through the first actuator 207. The gearbox control board 201 then shifts to 4th gear.

[0062] Therefore, in this state, the gearbox control board 201 executes the gear exactly according to the position of the gear lever 202.

[0063] 2. When the vehicle is in a high gear, such as 3rd or 4th gear, if the driver needs to limit the speed for safety, simply press the safety speed limit switch 200. This energizes the first drive unit 205, disconnects the first actuator 207, closes the fourth actuator 210, energizes the second drive unit 206, disconnects the second actuator 208, and closes the third and fifth actuators 209 and 211. Because the first actuator 207 is disconnected, the second input port 201b remains at a low level regardless of the output of the second output port 202b. Since the second actuator 208 is disconnected and the third actuator 209 is closed, the first input port 201a is disconnected from the first output port 202a and connected to the second output port 202b. Because the safety speed limit switch 200, the fourth actuator 210, and the fifth actuator 211 are all closed, the alarm circuit is activated, energizing the warning light 204, providing a driving warning.

[0064] The gear lever 202 is controlled in each gear position as follows:

[0065] (1) If the gear lever 202 is in 4th gear and the safety speed limit switch 200 is pressed, the second output port 202b is at a high level and is connected to the first input port 201a. The first input port 201a of the transmission control board 201 is at a high level and the second input port 201b is at a low level, so that the actual signal received by the transmission control board 201 corresponds to the signal when the gear lever 202 is in 1st gear, and the vehicle speed will drop to the safe speed state within the range of 1st gear.

[0066] (2) If the gear lever 202 is in 3rd gear and the safety speed limit switch 200 is pressed, the second output port 202b is at a high level and connected to the first input port 201a. The first input port 201a of the gearbox control board 201 is at a high level and the second input port 201b is at a low level, so that the actual signal received by the gearbox control board 201 corresponds to the signal when the gear lever 202 is in 1st gear, and the vehicle speed will drop to the safe speed state within the range of 1st gear.

[0067] (3) If the gear lever 202 is in 2nd gear and the safety speed limit switch 200 is pressed, the second output port 202b is at a low level and is connected to the first input port 201a. The first input port 201a of the transmission control board 201 is at a low level and the second input port 201b is at a low level, so that the actual signal received by the transmission control board 201 corresponds to the signal when the gear lever 202 is in 2nd gear, and the vehicle speed will be controlled to a safe speed state within the range of 2nd gear.

[0068] (4) If the gear lever 202 is in 1st gear and the safety speed limit switch 200 is pressed, the second output port 202b is low level and connected to the first input port 201a. The first input port 201a of the transmission control board 201 is low level and the second input port 201b is low level, so that the actual signal received by the transmission control board 201 corresponds to the signal when the gear lever 202 is in 2nd gear, and the vehicle speed will be controlled to a safe speed state within the range of 2nd gear.

[0069] 3. When the vehicle does not require a safe speed limit, releasing the safety speed limit switch 200 will restore the gear logic to its initial state.

Claims

1. A forklift truck safety speed limiting system characterised in that, The system includes a safety speed limit switch, a transmission control board, a gear shift lever, a first drive unit, a fourth actuator, and a second drive unit. The gear shift lever has a first output port and a second output port. The transmission control board has a first input port and a second input port. The second output port is electrically connected to the second input port via the first actuator. The first output port is electrically connected to the first input port via the second actuator. The second output port is electrically connected to the first input port via the third actuator. The opening and closing of the safety speed limit switch is used to change the on / off state of the first actuator, the second actuator, and the third actuator. The first actuator and the second actuator are normally closed, and the third actuator is normally open. When the second input port receives a low level, the transmission operates in a low gear; when the second input port receives a high level, the transmission operates in a high gear. The opening and closing of the safety speed limit switch is used to control the power supply to the first drive unit. When the first drive unit is energized, it drives the first actuator and the fourth actuator to operate. The opening and closing of the safety speed limit switch and the fourth actuator are used to jointly control the power supply to the second drive unit. When the second drive unit is energized, it drives the second actuator and the third actuator to operate. When the first drive unit is energized, the second drive unit is also energized. The first drive unit, the first actuator, and the fourth actuator constitute a first control element. The second drive unit, the second actuator, and the third actuator constitute a second control element. The first control element and the second control element are relays. The first drive unit and the second drive unit are coils of the relays. The first actuator, the second actuator, the third actuator, and the fourth actuator are contacts of the relays.

2. The forklift safety speed limiting system according to claim 1, characterized in that, The low-speed gear includes a first gear and a second gear. When the first input port is at a high level and the second input port is at a low level, the transmission operates in the first gear. When the first input port is at a low level and the second input port is at a low level, the transmission operates in the second gear.

3. The forklift safety speed limiting system according to claim 1, characterized in that, The high-speed gears include a third gear and a fourth gear. When the first input port is low and the second input port is high, the transmission operates in the third gear. When the first input port is high and the second input port is high, the transmission operates in the fourth gear.

4. The forklift safety speed limiting system according to claim 1, characterized in that, It includes an alarm light circuit, and the opening and closing of the safety speed limit switch is used to control the on / off state of the alarm light circuit.

5. The forklift safety speed limiting system according to claim 1, characterized in that, The system includes a display, which is electrically connected to the transmission control board via a communication line. The display is used to show the gear position executed by the transmission control board.

6. A forklift safety speed limiting system, characterized in that, The system includes a safety speed limit switch, a transmission control board, a gear shift lever, a first drive unit, a fourth actuator, a second drive unit, and a fifth actuator. The gear shift lever has a first output port and a second output port. The transmission control board has a first input port and a second input port. The second output port is electrically connected to the second input port through the first actuator. The first output port is electrically connected to the first input port through the second actuator. The second output port is electrically connected to the first input port through the third actuator. The opening and closing of the safety speed limit switch is used to change the on / off state of the first actuator, the second actuator, and the third actuator. The first actuator and the second actuator are normally closed, and the third actuator is normally open. When the second input port receives a low level, the transmission operates in a low gear; when the second input port receives a high level, the transmission operates in a high gear. The opening and closing of the safety speed limit switch is used to control the power supply of the first drive unit. When the first drive unit is energized, it drives the first execution unit and the fourth execution unit to operate. The opening and closing of the safety speed limit switch and the fourth execution unit are used to jointly control the power supply of the second drive unit. The opening and closing of the safety speed limit switch, the fourth execution unit, and the fifth execution unit are used to jointly control the on / off state of the alarm light circuit. When the second drive unit is energized, it drives the second execution unit, the third execution unit, and the fifth execution unit to operate. When the first drive unit is energized, the second drive unit is also energized. The first drive unit, the first execution unit, and the fourth execution unit constitute a first control element. The second drive unit, the second execution unit, the third execution unit, and the fifth execution unit constitute a second control element. The first control element and the second control element are relays. The first drive unit and the second drive unit are relay coils. The first execution unit, the second execution unit, the third execution unit, the fourth execution unit, and the fifth execution unit are relay contacts.

7. The forklift safety speed limiting system according to claim 6, characterized in that, The low-speed gear includes a first gear and a second gear. When the first input port is at a high level and the second input port is at a low level, the transmission operates in the first gear. When the first input port is at a low level and the second input port is at a low level, the transmission operates in the second gear.

8. The forklift safety speed limiting system according to claim 6, characterized in that, The high-speed gears include a third gear and a fourth gear. When the first input port is low and the second input port is high, the transmission operates in the third gear. When the first input port is high and the second input port is high, the transmission operates in the fourth gear.

9. The forklift safety speed limiting system according to claim 6, characterized in that, It includes an alarm light circuit, and the opening and closing of the safety speed limit switch is used to control the on / off state of the alarm light circuit.

10. The forklift safety speed limiting system according to claim 6, characterized in that, The system includes a display, which is electrically connected to the transmission control board via a communication line. The display is used to show the gear position executed by the transmission control board.

11. A forklift, characterized in that, Includes the forklift safety speed limiting system as described in any one of claims 1 to 10.

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