CN107986196B - Potential energy regeneration device for electric forklift - Google Patents

Abstract

The present invention discloses a potential energy regeneration device for an electric forklift, comprising a motor load system, a step-down conversion circuit, a main control module, a constant current control module and a power module; the constant current control module and the power module are electrically connected, and the motor load system, the step-down conversion circuit, the power module and the main control module are electrically connected and controlled by them; the present invention proposes a potential energy regeneration device for an electric forklift, which can greatly reduce the heat generated by load drop and realize energy regeneration.

Description

Potential energy regeneration device for electric forklift

Technical Field

The invention relates to the field of electric vehicles, and in particular to an energy-saving device for an electric forklift based on a battery and a supercapacitor.

Background technique

In recent years, the scale of my country's logistics industry has continued to grow rapidly. In 2015, the total social logistics volume in China reached 21.92 trillion yuan, an increase of 3.68 times compared with 2006, with an average annual growth of 15.58%. The total social logistics cost accounted for 16% of the national GDP. Among them, forklifts are the core handling equipment in the logistics industry. China's forklift industry has been growing at an average annual rate of 30% for more than ten consecutive years and has become the world's largest forklift production base. However, global warming and energy issues are becoming increasingly prominent, and high fuel prices have prompted the forklift industry to solve the current problem of high fuel consumption. In addition, since the lifting system is hydraulically driven, most of the lost potential energy is converted into throttling loss of the hydraulic system, which not only causes energy waste and reduces the continuous working time of the forklift, but also causes the hydraulic oil to heat up, damages the life of parts, and reduces system efficiency. Therefore, it is of great significance to recover the gravitational potential energy when the forklift cargo is lowered.

In addition, due to the working characteristics of forklifts, the lifting system requires frequent reciprocating motion, and the energy source needs to output a large current when lifting goods and accelerating the lifting. In electric forklifts, the instantaneous large current output has a large impact on the battery, seriously damaging the battery life. Therefore, in the energy management plan, it is necessary to reasonably match the energy output when lifting goods and accelerating the lifting to extend the battery life.

Regarding the potential energy recovery problem of electric forklifts, the existing technologies are as follows:

Taking Chinese patent 200610042603.3 as an example, the working state of the forklift lifting system is regulated and energy is recovered by controlling the working mode of the motor. This requires high-precision matching and response between the control system and the motor. The control system principle is complex and has high feasibility requirements.

Taking Chinese patent 201620398878.X as an example, partial potential energy recovery is achieved through three different forklift fork descent speed adjustment methods. The potential energy can be recovered when variable speed volumetric speed regulation exists, so the potential energy cannot be effectively recovered during throttling speed regulation, and the potential energy recovery efficiency is not high.

Taking Chinese patent 201510772125.0 as an example, the potential energy of the forklift lifting system is recovered by connecting an accumulator and a recovery oil circuit in the hydraulic system. Therefore, it is necessary to significantly change the overall hydraulic system oil circuit model of the forklift lifting system, which makes major changes to the forklift lifting system, is complex to operate, and has low interchangeability.

Taking Chinese patent 201620398878.X as an example, a newly designed reversing valve is used during the descent of the lifting system to use a battery to power the motor, so that the oil pump reverses during descent to drive the motor to reverse and generate electricity to recover part of the potential energy. This method has harsh implementation conditions and requires the purchase of a reversing valve specially made by the inventor/enterprise, and is not universal.

Summary of the invention

In view of the above technical problems, the present invention provides a potential energy regeneration device for an electric forklift.

In order to solve the above technical defects, the technical solution of the present invention is as follows:

A potential energy regeneration device for an electric forklift, comprising a motor load system, a step-down conversion circuit, a main control module, a constant current control module and a power module; the constant current control module and the power module are electrically connected, and the motor load system, the step-down conversion circuit, and the power module are electrically connected to the main control module and controlled thereby;

The motor load system includes a double-acting motor-generator, a double-acting oil pump-hydraulic motor, a cylinder, a third relay and auxiliary equipment, wherein the double-acting motor-generator is connected to the double-acting oil pump-hydraulic motor and the third relay, and the double-acting oil pump-hydraulic motor is connected to the cylinder and the auxiliary equipment;

The step-down conversion circuit includes an inductor, a second diode and a second MOS tube, the drain of the second MOS tube is connected to the motor load system, the source of the second MOS tube is connected to the inductor and the second diode, and the gate of the second MOS tube is connected to the main control module;

The main control module includes a controller, a first relay, a second relay, a first voltage detection module, and a second voltage detection module; the first relay, the second relay, the first voltage detection module, and the second voltage detection module are electrically connected to the controller and controlled by it; the controller receives a main switch signal, a lifting signal, and a lowering signal;

The power module includes a battery, a first diode, a first MOS tube, and a supercapacitor; the gate of the first MOS tube is connected to the constant current control module, the source of the first MOS tube is connected to the first diode, the drain of the first MOS tube is connected to the positive electrode of the battery, and the negative electrode of the battery is connected to the other end of the first diode and the supercapacitor motor load system.

Furthermore, one end of the first relay is connected to the source of the second MOS tube, and the other end is connected to the positive electrode of the battery; one end of the second relay is connected to the motor load system and the drain of the second MOS tube, and the other end is connected to the supercapacitor.

Furthermore, a first voltage detection module is connected between one end of the first relay and the battery, and a second voltage detection module is connected between the second relay and the supercapacitor.

Furthermore, the controller of the main control module controls the on and off of the first control relay, the second relay and the second MOS tube of the buck circuit through the feedback voltage signals of the first voltage detection module and the second voltage detection module and the forklift lifting signal, the lowering signal and the main switch signal.

Furthermore, the constant current control module can control the on-off of the first MOS tube when the first relay is disconnected and the second relay is closed, and enable the battery to charge the supercapacitor and control the charging current.

Furthermore, the third relay is controlled by a controller.

Furthermore, when the controller of the motor load system receives a lifting signal, the third relay is closed, and the double-acting motor-generator acts as a motor to drive the double-acting oil pump-hydraulic motor to rotate forward, thereby realizing load lifting; when the controller receives a descending signal, the third relay is closed, and the load decreases, driving the double-acting oil pump-hydraulic motor to reverse and become a hydraulic motor, thereby driving the double-acting motor-generator to reverse and generate electricity.

The present invention has the following advantages due to the adoption of the above technical solution:

1. The potential energy of load fall of traditional electric forklifts is wasted in the form of heat energy, which not only increases the operating load of key parts of the oil circuit, but also greatly increases the heat dissipation demand of the forklift cooling device, reducing the service life of the equipment. This device can recover and utilize most of the load potential energy, greatly reduce the heat generated by load fall, and realize energy recycling. It is suitable for most mid-to-high-end forklift products, with broad market prospects and significant energy-saving benefits.

2. By detecting the voltage signal of the dual energy source and receiving the lifting and lowering signals, the on and off of the relay is controlled to complete the energy source management when the forklift is working. The operation method is simple, the control program is simple, and no excessive hardware equipment is required. Most of the circuit design technologies are mature, so the circuit has strong operability and is easy to manufacture into an integrated module with a small volume and space, which is easy to place on the forklift. In addition, the control program does not have high requirements on the hardware's response speed, overload voltage, and current. The circuit cost is low and has good economic value.

3. Use a battery-supercapacitor energy storage solution, with the supercapacitor as the first storage device for recovering potential energy, and the battery as the second energy storage device for recovering potential energy when it is fully charged. Supercapacitors have high power density and are suitable for large current discharges, while batteries have high energy density and are suitable for long-term discharges. Therefore, comprehensive matching of the energy output of supercapacitors and batteries can maximize energy utilization and improve forklift efficiency. In addition, using supercapacitors as the energy source for lifting and starting and lifting acceleration of forklifts avoids the instantaneous large current output of the battery and can extend the battery life.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a block diagram of an overall circuit of the present invention;

FIG. 2 is a schematic diagram of a motor load system of the present invention.

Symbols in the figure: battery 1, first voltage detection module 2, constant current control module 3, first relay 4, first MOS tube 5, first diode 6, inductor 7, second diode 8, second MOS tube 9, second voltage detection module 10, supercapacitor 11, second relay 12, motor load system 13, controller 14, double-acting motor-generator B1, double-acting oil pump-hydraulic motor B2, cylinder B3, and third relay B4.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

As shown in Fig. 1, a potential energy regeneration device for an electric forklift includes a motor load system 13, a step-down conversion circuit, a main control module, a constant current control module 3 and a power module. The constant current control module 3 and the power module are electrically connected, and the motor load system 13, the step-down conversion circuit, and the power module are electrically connected to the main control module and controlled by it.

The motor load system 13 includes a double-acting motor-generator B1, a double-acting oil pump-hydraulic motor B2, a cylinder B3, a third relay B4 and ancillary equipment. As shown in FIG2 , the double-acting motor-generator B1 is connected to the double-acting oil pump-hydraulic motor B2 and the third relay B4, and the double-acting oil pump-hydraulic motor B2 is connected to the cylinder B3 and the ancillary equipment.

The step-down conversion circuit includes an inductor 7, a second diode 8 and a second MOS transistor 9, wherein the drain of the second MOS transistor 9 is connected to the motor load system 13, the source of the second MOS transistor 9 is connected to the inductor 7 and the second diode 8, and the gate of the second MOS transistor 9 is connected to the main control module. The third relay B4 is controlled by the main control module, that is, the controller 14 of the main control module. The controller 14 receives the main switch signal, the lifting signal, and the lowering signal. When the controller 14 receives the lifting signal, the third relay B4 is closed, and the double-acting motor-generator B1 drives the double-acting oil pump-hydraulic motor B2 to rotate forward as a motor to achieve load lifting; when the controller 14 receives the lowering signal, the third relay B4 is closed, and the load lowering drives the double-acting oil pump-hydraulic motor B2 to reverse and become a hydraulic motor, and drives the double-acting motor-generator B1 to reverse and generate electricity. The third relay B4 is controlled by the controller 14, and is turned on when the lifting/lowering signal is received, and is disconnected when it is in the standby signal.

The main control module includes a controller 14, a first relay 4, a second relay 12, a first voltage detection module 2, and a second voltage detection module 10; the first relay 4, the second relay 12, the first voltage detection module 2, and the second voltage detection module 10 are electrically connected to the controller 14 and controlled by it; the controller 14 receives a total switch signal, a lifting signal, and a lowering signal. One end of the first relay 4 is connected to the source of the second MOS tube 9, and the other end is connected to the positive electrode of the battery 1; one end of the second relay 12 is connected to the motor load system 13 and the drain of the second MOS tube 9, and the other end is connected to the super capacitor 11. The first voltage detection module 2 is connected between one end of the first relay 4 and the battery 1, and the second voltage detection module 10 is connected between the second relay 12 and the super capacitor 11.

The controller 14 of the main control module controls the on and off of the first control relay, the second relay 12 and the second MOS tube 9 of the step-down circuit through the feedback voltage signals of the first voltage detection module 2 and the second voltage detection module 10 and the forklift lifting signal, the lowering signal and the main switch signal.

The power module includes a battery 1, a first diode 6, a first MOS tube 5, and a super capacitor 11; the gate of the first MOS tube 5 is connected to the constant current control module 3, the source of the first MOS tube 5 is connected to the first diode 6, the drain of the first MOS tube 5 is connected to the positive electrode of the battery 1, the negative electrode of the battery 1 is connected to the other end of the first diode 6, and the super capacitor 11 is connected to the motor load system 13. The constant current control module 3 can control the on and off of the first MOS tube 5 when the first relay 4 is disconnected and the second relay 12 is closed, and enables the battery 1 to charge the super capacitor 11 and control the charging current.

In summary, when the controller 14 receives a lifting signal, i.e., a lifting start or acceleration signal, the controller 14 sends a signal based on the voltage signals fed back by the first voltage detection module 2 and the second voltage detection module 10, and when the voltage across the supercapacitor 11 is not less than 24V, to control the first relay 4 to disconnect and the second relay 12 to conduct, so that the supercapacitor 11 is in a power supply state, and the power supply is provided until the voltage of the supercapacitor 11 is lower than 20V. If the voltage across the supercapacitor 11 is originally less than 24V, the battery 1 is still used for power supply.

When the controller 14 does not receive a lifting signal or a lowering signal, the lifting system of the forklift is in a standby state, and the controller 14 controls the first relay 4 and the second relay 12 to be disconnected.

When the controller 14 receives the falling signal, according to the voltage signal fed back by the first voltage detection module 2 and the second voltage detection module 10, and when the voltage across the super capacitor 11 is not greater than 28V, the controller 14 sends a signal to control the first relay 4 to be disconnected and the second relay 12 to be turned on, so that the motor load system 13 charges the super capacitor 11. If the voltage across the super capacitor 11 is originally greater than 28V, the controller 14 controls the first relay 4 to be disconnected and the second relay 12 to be disconnected, and outputs a PWM signal to the second MOS tube 9, that is, outputs pulse width modulation to control the on and off of the semiconductor device second MOS tube 9, so that the motor load system 13 charges the battery 1. And according to the feedback signal of the first voltage detection module 2, the duty cycle of the PWM signal is adjusted so that the charging voltage is stabilized at 28.5V, and constant voltage charging is achieved.

When the voltage of the supercapacitor 11 is detected to be greater than 28V under the descending signal for five consecutive times, when the lifting system of the forklift is in the standby state, the controller 14 controls the first relay 4 to be disconnected and the second relay 12 to be turned on, and outputs a PWM signal to the second MOS tube 9, so that the supercapacitor 11 charges the battery 1, and adjusts the duty cycle of the PWM signal according to the feedback signal of the first voltage detection module 2 to realize constant voltage charging, until the voltage of the supercapacitor 11 is no more than 24V or a lifting signal or a descending signal is received.

When the voltage of the supercapacitor 11 is detected to be lower than 24V for five consecutive times when the lifting signal is started or accelerated, when the lifting system of the forklift is in standby mode, the controller 14 controls the first relay 4 to be disconnected and the second relay 12 to be turned on, and the battery 1 charges the supercapacitor 1111 with a constant current of 5A through the constant current charging module.

The constant current control module 3, when the first relay 4 and the second relay 12 are both closed, determines the size of the charging current by judging the voltage drop condition of its internal sampling resistor, thereby controlling the on and off of the first MOS tube 5, completing the charging of the supercapacitor 11 by the battery 1, and controlling the charging current to be around 5A.

The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the concept of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims (5)

1. The potential energy regenerating device for the electric forklift is characterized by comprising a motor load system, a buck conversion circuit, a main control module, a constant current control module and a power supply module; the motor load system, the buck conversion circuit and the power supply module are electrically connected with the main control module and controlled by the main control module;

the motor load system comprises a double-acting motor-generator, a double-acting oil pump-hydraulic motor, an oil cylinder, a third relay and accessory equipment, wherein the double-acting motor-generator is connected with the double-acting oil pump-hydraulic motor and the third relay, and the double-acting oil pump-hydraulic motor is connected with the oil cylinder and the accessory equipment;

The buck conversion circuit comprises an inductor, a second diode and a second MOS tube, wherein the drain electrode of the second MOS tube is connected with the motor load system, the source electrode of the second MOS tube is connected with the inductor and the second diode, and the grid electrode of the second MOS tube is connected with the main control module;

The main control module comprises a controller, a first relay, a second relay, a first voltage detection module and a second voltage detection module; the first relay, the second relay, the first voltage detection module and the second voltage detection module are electrically connected with the controller and controlled by the controller; the controller receives a main switch signal, a lifting signal and a descending signal;

The power module comprises a storage battery, a first diode, a first MOS tube and a super capacitor; the grid electrode of the first MOS tube is connected with the constant current control module, the source electrode of the first MOS tube is connected with the first diode, the drain electrode of the first MOS tube is connected with the positive electrode of the storage battery, the negative electrode of the storage battery is connected with the other end of the first diode, and the super capacitor motor load system is connected;

When the motor load system receives a lifting signal, the third relay is closed, and the double-acting motor-generator is used as a motor to drive the double-acting oil pump-hydraulic motor to rotate positively, so that load lifting is realized; when the controller receives a descending signal, the third relay is closed, and the load descends to drive the double-acting oil pump-hydraulic motor to reversely rotate to become the hydraulic motor, and drive the double-acting motor-generator to reversely rotate to generate electricity; the third relay is controlled by a controller; turned on when the up/down signal is received and turned off when the standby signal is received.

2. The potential energy regenerating device for an electric forklift according to claim 1, wherein one end of the first relay is connected with a source electrode of the second MOS tube, the other end of the first relay is connected with a positive electrode of the storage battery, one end of the second relay is connected with a motor load system and a drain electrode of the second MOS tube, and the other end of the second relay is connected with the super capacitor.

3. The potential energy regenerating device for an electric forklift of claim 2, wherein a first voltage detection module is connected between one end of the first relay and the storage battery, and a second voltage detection module is connected between the second relay and the super capacitor.

4. The potential energy regeneration device for the electric forklift as claimed in claim 1, wherein the controller of the main control module controls the on-off of the first control relay, the second relay and the second MOS tube of the step-down circuit through the feedback voltage signals of the first voltage detection module and the second voltage detection module, the forklift lifting signal, the descending signal and the master switch signal.

5. The potential energy regenerating device for an electric forklift according to claim 1, wherein the constant current control module can control on-off of the first MOS transistor when the first relay is turned off and the second relay is turned on, and charge the super capacitor with the storage battery and control charging current.