CN116620017B - Hydrostatic traveling forklift truck traveling speed control method - Google Patents
Hydrostatic traveling forklift truck traveling speed control method Download PDFInfo
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- CN116620017B CN116620017B CN202310921878.8A CN202310921878A CN116620017B CN 116620017 B CN116620017 B CN 116620017B CN 202310921878 A CN202310921878 A CN 202310921878A CN 116620017 B CN116620017 B CN 116620017B
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- 230000002706 hydrostatic effect Effects 0.000 title claims abstract description 34
- 238000000034 method Methods 0.000 title claims abstract description 28
- 238000012546 transfer Methods 0.000 claims abstract description 51
- 230000001133 acceleration Effects 0.000 claims description 26
- 230000009467 reduction Effects 0.000 claims description 22
- 230000007423 decrease Effects 0.000 claims description 6
- 239000000446 fuel Substances 0.000 abstract description 5
- 238000005299 abrasion Methods 0.000 abstract description 4
- 238000006073 displacement reaction Methods 0.000 description 19
- 230000000875 corresponding effect Effects 0.000 description 11
- 230000008569 process Effects 0.000 description 5
- 230000000630 rising effect Effects 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000002411 adverse Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
- B60K31/00—Vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed, i.e. preventing speed from exceeding an arbitrarily established velocity or maintaining speed at a particular velocity, as selected by the vehicle operator
- B60K31/02—Vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed, i.e. preventing speed from exceeding an arbitrarily established velocity or maintaining speed at a particular velocity, as selected by the vehicle operator including electrically actuated servomechanism including an electric control system or a servomechanism in which the vehicle velocity affecting element is actuated electrically
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
- B60T13/74—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with electrical assistance or drive
Abstract
The application relates to the technical field of hydrostatic traveling forklift trucks, and discloses a hydrostatic traveling forklift truck traveling speed control method which comprises a speed control step when forklift trucks are shifted and switched, a speed control step when forklift trucks are accelerated and a speed control step when forklift trucks are decelerated. The application discloses a method for controlling the running speed of a hydrostatic running forklift truck, which solves the technical problems that the existing hydrostatic running forklift truck is damaged by a transfer case due to mismatching of a requested gear and an actual gear, an engine is easy to be directly braked and flamed out when braking, a brake pad is fast in abrasion, the fuel economy is poor and the like to a certain extent.
Description
Technical Field
The application relates to the technical field of hydrostatic traveling forklift trucks, in particular to a traveling speed control method of a hydrostatic traveling forklift truck.
Background
The hydrostatic traveling forklift truck replaces a traditional gearbox by a hydraulic pump and a traveling motor, and provides driving power for the whole forklift. Compared with the traditional forklift, the hydrostatic traveling forklift has the advantages that the transmission efficiency is greatly improved, the oil consumption can be saved, and therefore the hydrostatic traveling forklift has a wide application prospect. The speed control of the hydrostatic traveling forklift is an important point and a difficult point in the whole vehicle control, and the existing hydrostatic traveling forklift has a plurality of technical problems caused by defects in the aspect of speed control: in the existing hydrostatic traveling forklift truck, when shifting gears, the transfer case is not in a gear required by an operator due to the transfer case, in other words, the gear of the transfer case is inconsistent with that of a gear shifting handle, and at the moment, if the motor is controlled to travel at a high speed, the transfer case is easy to be toothed to cause gear damage, and the transfer case is seriously damaged; when the forklift is decelerating, the pump current needs to be reduced for reducing the displacement and flow of the pump so as to decelerate the motor, but when the pump current is reduced, the motor is in a pump working condition due to the inertia of the motor, the motor drives the pump to rotate so as to accelerate the pump, thereby driving the engine to increase in rotation speed, and when the rotation speed of the engine is increased to a certain value, the service life of the engine is reduced and damaged, particularly when the rotation speed of the engine exceeds the highest allowable rotation speed of the engine, the service life of the engine is easily reduced and damaged; when the pedal is stepped on to perform hydraulic braking, the speed of the vehicle is reduced, but at this time, the pump may have a lower vehicle speed and a relatively large pump current due to the deceleration according to the deceleration ramp of the reduced value of each program cycle, so that the pump drives the vehicle to move forward, but the braking prevents the vehicle from moving forward, and at this time, the situation is easy to cause: 1. the rotation speed of the engine is reduced, even the rotation speed is reduced below the lowest rotation speed, so that the vehicle is flamed out, namely, the engine is directly flamed out when the vehicle is braked; 2. the pump and the brake cause the brake pad to be worn too fast under the action of the brake, and the service life of the brake pad is influenced; the forklift belongs to a long-time operation vehicle, fuel economy is an important index for measuring forklift performance, but in the actual operation process, a hydraulic pump works in a low-efficiency area, the efficiency is low, the oil consumption is high, in addition, when the forklift accelerates, the current of the pump can reach the maximum value when the engine reaches the maximum rotation speed because the current of the pump is positively correlated with the rotation speed of the engine, the acceleration process of the vehicle is slower, the engine is in a high-rotation speed working condition under more working conditions, and the oil consumption is relatively larger.
Disclosure of Invention
The application aims to provide a running speed control method of a hydrostatic running forklift truck, which is used for solving the technical problems that a transfer case is damaged due to mismatching of a requested gear and an actual gear of the transfer case, an engine is easy to brake and stall by braking, a brake pad is fast in abrasion, the fuel economy is poor and the like in the existing hydrostatic running forklift truck due to the defect of speed control.
In order to achieve the above object, the present application provides a method for controlling the running speed of a hydrostatic traveling forklift, wherein the hydrostatic traveling forklift drives a hydraulic pump through an engine, the hydraulic pump drives a traveling motor, the traveling motor drives a transfer case, the transfer case distributes power to a front axle and a rear axle, the transfer case has a plurality of gears, the method comprises a speed control step when the forklift is shifted and switched, specifically: the gear signal of the gear shifting handle and the actual gear signal of the transfer case are fed back to the controller, the controller reads the rotating speed sensor signal of the traveling motor, judges whether the current vehicle is in a starting state or not, the controller judges whether the gear of the gear shifting handle is consistent with the actual gear of the transfer case or not, and when the controller judges that the vehicle is in the starting state and the gear of the gear shifting handle is inconsistent with the actual gear of the transfer case, the controller executes the following control logic: when the engine speed corresponding to the accelerator pedal is greater than a speed limit value, limiting the engine speed, limiting the maximum value of the hydraulic pump current at the same time, detecting the real-time speed of the traveling motor, and when the real-time speed of the traveling motor is greater than the speed limit value, reducing the request speed of the engine in each program cycle until the speed of the traveling motor is below the speed limit value, and maintaining the request speed of the engine; when the gear of the gear shifting handle is consistent with the actual gear of the transfer case through the control logic, the control logic is exited, the engine request rotating speed is restored to be the same as the engine rotating speed calculated by the accelerator pedal, and the limitation on the maximum value of the hydraulic pump current is canceled.
Preferably, the transfer case is provided with a first gear and a second gear, the transfer case is provided with a first gear switch sensor corresponding to the first gear and a second gear switch sensor corresponding to the second gear, and the first gear switch sensor and the second gear switch sensor are electrically connected with the controller; when the actual gear of the transfer case is the first gear, the first gear sensor feeds back a signal to the controller; and when the actual gear of the transfer case is the second gear, the second gear sensor feeds back a signal to the controller.
Preferably, the running motor is provided with a rotation speed sensor, and the rotation speed sensor is electrically connected with the controller, so that the rotation speed of the running motor is measured through the rotation speed sensor, and the rotation speed information of the running motor is fed back to the controller to assist the controller to calculate the real-time speed of the vehicle.
Preferably, the hydrostatic traveling forklift travel speed control method further includes a forklift acceleration speed control step, which includes: in the first acceleration stage, the engine is increased from a first rotating speed to a second rotating speed, and the hydraulic pump current and the engine rotating speed are in a linear proportional relation; and a second acceleration stage in which the engine continues to rise from the second rotation speed to the third rotation speed while the hydraulic pump current is kept at a maximum value.
Preferably, the first rotation speed is an idle rotation speed of the engine, or the first rotation speed is greater than the idle rotation speed of the engine.
Preferably, the hydrostatic traveling forklift running speed control method further comprises a speed control step when the forklift is decelerated, wherein the speed control step comprises a deceleration stage, and specifically comprises the following steps: when the engine request speed is smaller than the engine actual speed, taking the value of subtracting the engine request speed from the engine actual speed as a judgment basis to control the speed of the hydraulic pump to reduce the value every program cycle, and executing the following control logic: when the value obtained by subtracting the engine request speed from the engine actual speed is smaller than a first threshold value, the speed of the hydraulic pump is reduced to a first constant value every program cycle; when the value obtained by subtracting the engine request speed from the actual engine speed is larger than a first threshold value, the speed of the hydraulic pump is reduced by less than the first constant value every program cycle.
Preferably, in the deceleration phase, when the value of the engine actual rotation speed minus the engine requested rotation speed is greater than a first threshold value and gradually increases, the current reduction value of the hydraulic pump per program cycle is smaller than the first fixed value and gradually decreases.
Preferably, the speed control step during deceleration further comprises a pedal braking stage, specifically: when the engine request rotating speed is larger than the engine actual rotating speed, taking the value of subtracting the engine actual rotating speed from the engine request rotating speed as a judging basis to control the rotating speed of the hydraulic pump to reduce the value every program cycle, and executing the following control logic after the controller detects a braking signal: when the value obtained by subtracting the actual engine speed from the engine request speed is smaller than a second threshold value, the current of the hydraulic pump is reduced to a second constant value every program cycle; when the value of the engine request speed minus the engine actual speed is greater than the second threshold value and gradually increases, the speed of the hydraulic pump is reduced by a value greater than the second fixed value every program cycle.
Preferably, in the step-on pedal braking phase, when the difference of the engine request speed minus the engine actual speed is greater than a second threshold value and gradually increases, the current reduction value of the hydraulic pump is greater than the second constant value and gradually increases every program cycle.
Due to the adoption of the technical scheme, the application has at least the following technical effects:
1. when the controller judges that the gear of the gear shifting handle is inconsistent with the actual gear of the transfer case, certain control logic is executed on the basis that the motor rotation speed is influenced by the pump displacement, the engine rotation speed and the motor displacement, the purpose of limiting the motor rotation speed is achieved, the technical problem that the transfer case gear is damaged when the gear shifting handle is used for shifting gears due to the fact that the gear of the transfer case is inconsistent with the gear of the gear shifting handle is avoided as far as possible, the transfer case is guaranteed to have reliable service life, is not easy to damage, and reduces the probability of failure.
2. In the speed control step when the forklift is accelerated, when the rotating speed of the engine is small, the pump current rises to the maximum value, namely, in the acceleration process, the pump current reaches the maximum value in advance, namely, the pump current value reaches the maximum value at the corresponding rotating speed of the maximum torque point of the engine, so that the whole car reaches a larger speed near the maximum torque point of the engine, and the whole car is accelerated faster, thereby being beneficial to improving the working efficiency; when the pump current is reduced, the rotating speed of the engine is in a low rotating speed state, the change speed of the pump current can be slowed down according to the reverse dragging condition, excessive reverse dragging is prevented, the rotating speed of the engine is further prevented from being higher than the highest allowable rotating speed, the service life of the engine is ensured, and the probability of failure of the engine is effectively reduced.
3. The forklift belongs to a long-time operation vehicle, and fuel economy is an important index for measuring forklift performance. In the speed control step when the forklift is accelerated, the pump current is increased to the maximum in advance, so that the pump is in a high-efficiency zone for a long time, the efficiency is high, the oil consumption is low, the pump is in the high-efficiency zone, and the engine is also in a high-efficiency oil-saving zone when the engine rotating speed is low, and the oil consumption is further reduced.
4. In the forklift deceleration stage, the engine request rotating speed is smaller than the engine actual rotating speed, the value of subtracting the engine request rotating speed from the engine actual rotating speed is used as a judgment basis to control the rotating speed of the hydraulic pump to be a program cycle reduction value, and the magnitude of each program cycle reduction value is controlled according to a certain control logic, so that adverse effects on the service life of the engine due to excessive engine acceleration are avoided; in the pedal braking stage, the engine request rotating speed is larger than the engine actual rotating speed, the value of the engine request rotating speed minus the engine actual rotating speed is used as a judgment basis to control the rotating speed of the hydraulic pump to be a program cycle reduction value, and the magnitude of each program cycle reduction value is controlled according to certain control logic, so that the pedal is prevented from being stepped on and off to directly put the engine on and off, the excessively rapid abrasion of a brake pad is avoided, and the service life of the brake pad is ensured.
Drawings
FIG. 1 is a graph showing the relationship between the engine speed and the hydraulic pump current and the traveling motor current, respectively, when the hydrostatic forklift truck is accelerated.
Detailed Description
The application provides a hydrostatic traveling forklift running speed control method, wherein a hydrostatic transmission system of the hydrostatic traveling forklift is characterized in that the hydrostatic traveling forklift drives a hydraulic pump (hereinafter referred to as a hydraulic pump or a pump) through an engine, the hydraulic pump drives a traveling motor (hereinafter referred to as a traveling motor or a motor), the traveling motor drives a transfer case, the transfer case distributes power to a front axle and a rear axle, the system is supplied with oil from an oil tank and returns oil to the oil tank, the transfer case is provided with a plurality of gears, and the control method comprises the speed control steps when the forklift is shifted and switched, and comprises the following steps:
the gear signal of the gear shifting handle and the actual gear signal of the transfer case are fed back to the controller, the controller reads the rotating speed sensor signal of the traveling motor, judges whether the current vehicle is in a starting state or not, the controller judges whether the gear of the gear shifting handle is consistent with the actual gear of the transfer case or not, and when the controller judges that the vehicle is in the starting state and the gear of the gear shifting handle is inconsistent with the actual gear of the transfer case, the controller executes the following control logic: when the engine speed corresponding to the accelerator pedal is greater than a speed limit value, limiting the engine speed, limiting the maximum value of the hydraulic pump current at the same time, detecting the real-time speed of the traveling motor by a speed sensor of the traveling motor, and when the real-time speed of the traveling motor is greater than the speed limit value, reducing the request speed of the engine in each program cycle until the speed of the traveling motor is below the speed limit value, and maintaining the request speed of the engine;
when the gear of the gear shifting handle is consistent with the actual gear of the transfer case through the control logic, the control logic is exited, the engine request rotating speed is restored to be the same as the engine rotating speed calculated by an accelerator pedal (the accelerator pedal is calculated, a cab accelerator pedal signal is fed back to a controller, the controller calculates the operation intention and the target running speed of an operator according to the analog quantity signal of the accelerator pedal and the real-time rotating speed of the engine, the controller corresponds the target running speed to a pump current, the controller gives the hydraulic pump current according to the pump current, the hydraulic pump is increased to the pump current according to the set stepping value), and the limitation on the maximum value of the hydraulic pump current is canceled.
Specifically, the transfer case may be provided with sensors corresponding to different gear positions, where the sensors are used to acquire a gear signal of the transfer case and feed the signal back to the controller. In specific implementation, the transfer case is provided with a first gear and a second gear, a first gear switch sensor corresponding to the first gear and a second gear switch sensor corresponding to the second gear are arranged on the transfer case, and the first gear switch sensor and the second gear switch sensor are electrically connected with the controller; when the transfer case is actually in the first gear, the first gear sensor corresponding to the first gear feeds back a signal to the controller, and the second gear sensor corresponding to the second gear does not feed back the signal; when the transfer case is actually in the second gear, the first gear sensor does not feed back, and the second gear sensor feeds back a signal to the controller. During gear shifting, a gear switched by a gear shifting handle operated by an operator and a gear where the transfer case is located, which is measured by a transfer case sensor, are respectively fed back to a controller, and the controller judges whether the two gears are consistent according to an input signal. When the controller judges that the vehicle is in a starting state according to the real-time rotating speed of the traveling motor and judges that the gear of the gear shifting handle is inconsistent with the actual gear of the transfer case according to the feedback of the gear shifting handle and the transfer case, the control logic is executed, and the motor rotating speed is influenced by the pump displacement, the engine rotating speed and the motor displacement and depends on the current engine rotating speed, so that the aim of limiting the motor rotating speed can be achieved through the control logic, the technical problem that the gear of the transfer case is damaged when the gear shifting handle is inconsistent with the gear of the gear shifting handle when the gear shifting handle is cut is avoided as much as possible, the transfer case is guaranteed to have reliable service life, is not easy to damage, and the probability of failure is reduced. In specific implementation, the running motor is provided with a rotating speed sensor, the rotating speed sensor is electrically connected with the controller, the rotating speed of the running motor is measured through the rotating speed sensor, and the rotating speed information of the running motor is fed back to the controller to assist the controller in calculating the real-time speed of the vehicle. Specifically, after the rotating speed information of the walking motor is fed back to the controller by the rotating speed sensor, the controller can calculate the real-time vehicle speed according to the rotating speed and parameters such as the speed reduction ratio of the transfer case, the axle speed ratio of the forklift, the wheel diameter and the like.
The application discloses a hydrostatic traveling forklift running speed control method which also comprises a forklift speed control step when accelerating, and comprises the following steps:
in the first acceleration stage, the engine is increased from a first rotating speed to a second rotating speed, and the hydraulic pump current and the engine rotating speed are in a linear proportional relation; and a second acceleration stage in which the engine continues to rise from the second rotation speed to the third rotation speed while the hydraulic pump current is kept at a maximum value.
The first acceleration stage is a stage in which the hydraulic pump and the engine accelerate simultaneously, the hydraulic pump current and the engine speed are in a linear proportional relationship, at the moment, the hydraulic pump output flow is the product of the engine speed and the hydraulic pump discharge capacity, the hydraulic pump discharge capacity and the hydraulic pump current are in a linear proportional relationship, the hydraulic pump output flow rises, the vehicle speed starts to accelerate from 0, the pump current of the hydraulic pump reaches the maximum value at the tail end of the first acceleration stage, and the rotation speed of the pump current is always kept at the maximum value along with the rising of the engine speed; moreover, as can be understood by those skilled in the art, in the acceleration process of the forklift truck, when the rotation speed of the engine is small, the pump current rises to the maximum value, namely, in the acceleration process, the pump current reaches the maximum value in advance, namely, the pump current value reaches the maximum value at the corresponding rotation speed of the maximum torque point of the engine, so that the whole truck reaches a larger speed near the maximum torque point of the engine, the whole truck accelerates faster, thereby being beneficial to improving the working efficiency, and in addition, the pump is beneficial to being in a high-efficiency interval for a long time, the efficiency is high, the oil consumption is low, and the rotation speed of the engine is low when the pump is in the high-efficiency interval, so that the engine is also in a high-efficiency oil-saving interval, the oil consumption is further reduced, and the fuel economy of the forklift truck is improved; when the pump current is reduced, the rotating speed of the engine is in a low rotating speed state, the change speed of the pump current is slowed down according to the reverse dragging condition, excessive reverse dragging is prevented, and then the rotating speed of the engine is prevented from being higher than the highest allowable rotating speed, so that the service life of the engine is effectively ensured, and the damage of the engine is avoided. Taking 2400rpm as an example of the highest allowable rotation speed of the engine, when the engine request rotation speed is 2200rpm, the engine is reversely dragged by 500rpm when the pump current is reduced, the engine is reversely dragged to 2700rpm which is higher than the highest allowable rotation speed of the engine, but in the application, when the pump current is reduced, the engine is at a lower rotation speed, such as 1400rpm, even if the engine is reversely dragged by 500rpm, the engine can only be reversely dragged to 1900rpm and cannot be higher than 2400rpm which is the highest allowable rotation speed, so that the engine has a good protection effect, and the probability of the engine failure is effectively reduced.
Further, in the first acceleration stage, the current of the traveling motor can be increased, and the current and the flow of the traveling motor are in a linear proportional relationship, so that the reduction of the displacement of the traveling motor and the increase of the vehicle speed are realized. Of course, in the second acceleration stage, the current of the travel motor may be increased, and the current and the flow rate of the travel motor may be in a linear proportional relationship, so that the reduction of the travel motor displacement and the increase of the vehicle speed may be realized. By controlling the motor displacement reduction in the first acceleration stage and the second acceleration stage, the engine speed increase and the travel motor displacement reduction are parallel, the current displacement of the motor can be calculated according to the motor current, and the motor flow can be calculated according to the current displacement and the rotation speed of the motor (the rotation speed of the motor is detected by a rotation speed sensor arranged on the travel motor). When the current of the motor rises initially, the motor displacement proportional solenoid valve gives an initial minimum current value, the minimum current value is dead zone current, at the moment, the motor is maximum displacement, the rotating speed of the engine rises, the flow of the motor rises, the current of the motor rises along with the rising, the motor displacement is reduced along with the rising, and the speed of the vehicle is accelerated. Typically the control current of the motor is generally dependent on the opening of the foot pedal, but this approach tends to cause hydraulic system flooding due to the rapid acceleration of the forklift. Therefore, in the speed control step during acceleration, the motor flow is used for controlling the motor displacement by utilizing the linear proportional relation between the current and the flow of the motor, and when the rotating speed of the motor is increased, the current is slowly increased basically without overflowing a hydraulic system.
Further, the first rotational speed is an idle rotational speed of the engine, or the first rotational speed is greater than the idle rotational speed of the engine. I.e. in the first acceleration phase, the engine may start to accelerate from idle speed or from a rotational speed above idle speed.
Referring to fig. 1, the present application schematically shows a pump current of a hydraulic pump and a motor current variation of a travel motor for accelerating an engine from a first rotational speed according to a speed control step when a forklift is accelerated. Specifically, during the first acceleration phase, the engine is ramped up from a first speed of 1150rpm to a second speed of 1350rpm (of course, the engine may also be ramped up from an idle speed at 1050rpm to 1350 rpm), and the hydraulic pump current is ramped up from 640mA to 1640mA; in the second acceleration stage, the engine is increased from the second rotational speed 1350rpm to a third rotational speed 2200rpm; in the second acceleration stage, the current of the walking motor rises from 400mA to 1200mA, the current and the flow of the walking motor are in linear proportional relation, the displacement of the walking motor is reduced, and the vehicle speed rises rapidly. Taking the output of a hydraulic pump as an example, the flow rate of 50L/min is taken as the conventional method: engine speed 2000rpm, pump displacement 25cc,2000 x 25/1000 about 50L/min; the application comprises the following steps: the engine is 1350rpm, the pump displacement 37cc,1350 x 37/1000 is about 50L/min, it can be seen that the same flow is output, the conventional method is 25cc, the engine speed is 2000rpm, the application is 37cc,1350 rpm, the pump displacement is bigger, the engine speed is smaller, so the pump is in the high-efficiency interval, the engine speed is low, and the pump is also in the high-efficiency oil-saving interval. The present application schematically shows that in the second acceleration phase, with the pump current and the motor current respectively kept at maximum, the engine speed rises from 1700rpm to 2200rpm, no higher than the usual design with the maximum allowable engine speed of 2400rpm, avoiding that the engine speed exceeds the maximum allowable speed and is detrimental to the service life.
The application discloses a hydrostatic traveling forklift running speed control method, which also comprises a speed control step when forklift is decelerated, and comprises a deceleration stage, specifically: the engine request speed is greater than the engine actual speed, the value of the engine actual speed minus the engine request speed is taken as a judgment basis to control the speed of the hydraulic pump to decrease by a value every program cycle, and the following control logic is executed: when the value obtained by subtracting the engine request speed from the engine actual speed is smaller than a first threshold value, the speed of the hydraulic pump is reduced to a first constant value every program cycle; when the value of the actual engine speed minus the requested engine speed is greater than a first threshold value and gradually increases, the value of the decrease in the speed of the hydraulic pump per program cycle is smaller than the first fixed value. Those skilled in the art will appreciate that, during the deceleration phase of the forklift, when the pump current begins to decrease, the engine speed increases due to the higher vehicle speed, for example: when the foot pedal is released, the engine speed is required to be reduced from 2200rpm to 1100rpm, the engine speed is not reduced, but is increased to 2600rpm, after the condition is maintained for a period of time (after the vehicle speed is reduced to a certain value), the engine speed starts to be reduced, and the phenomenon leads to the engine speed exceeding the maximum engine speed, and the service life of the engine is reduced and damaged. Therefore, in the application, in the forklift deceleration stage, the value of the actual rotation speed of the engine minus the required rotation speed of the engine is taken as a judgment basis to control the rotation speed of the hydraulic pump to be reduced by each program cycle, and the magnitude of each program cycle reduction value is controlled according to the control logic, especially when the value of the actual rotation speed of the engine minus the required rotation speed of the engine is larger than a first threshold value, the rotation speed of the hydraulic pump is smaller than a first fixed value, and when the value of the actual rotation speed of the engine minus the required rotation speed of the engine is larger, the rotation speed of the hydraulic pump is smaller than the program cycle reduction value, so that the rotation speed of the engine is quickly reduced, and the adverse influence on the service life of the engine caused by excessive rising speed of the engine is avoided. The specific size of the first threshold is not limited in the present application, and for example, the first threshold may be set to 100rpm.
The speed control step during deceleration also comprises a pedal braking stage, and specifically comprises the following steps: when the engine request rotating speed is larger than the engine actual rotating speed, taking the value of subtracting the engine actual rotating speed from the engine request rotating speed as a judgment basis to control the current of the hydraulic pump to reduce the value every program cycle, and executing the following control logic after the controller detects a braking signal: when the value obtained by subtracting the actual engine speed from the engine request speed is smaller than a second threshold value, the current reduction value of the hydraulic pump is a fixed value every program cycle; when the value of the engine request speed minus the engine actual speed is greater than the second threshold value and gradually increases, the current of the hydraulic pump gradually increases by a program cycle reduction value. As will be appreciated by those skilled in the art, when the foot pedal hydraulic brake is depressed, the hydraulic pump is controlled in accordance with the control logic to reduce the current per program cycle: when the value obtained by subtracting the actual rotation speed of the engine from the engine request rotation speed is smaller than a second threshold value, the current reduction value of the hydraulic pump is a second fixed value every program cycle, so that the pump is decelerated according to a normal braking slope; when the value of the engine request speed minus the engine actual speed is larger than a second threshold value, the current per program cycle reduction value of the hydraulic pump is larger than the second fixed value, and when the difference value of the engine request speed minus the engine actual speed is larger than the second threshold value and gradually increases, the current per program cycle reduction value of the hydraulic pump is gradually increased, so that the reduction rate of the pump current is increased, the pump current is rapidly reduced when the pedal is stepped on for braking, the phenomenon that the hydraulic pump drives the vehicle to advance and then brake to prevent the vehicle from advancing during braking is avoided, the phenomenon that the engine is directly stepped on and off due to the pedal is avoided, the excessively rapid abrasion of a brake pad is also avoided, and the service life of the brake pad is ensured. The specific size of the second threshold is not limited in the present application, and for example, the second threshold may be set to 100rpm.
The technical solution protected by the present application is not limited to the above embodiments, and it should be noted that, the combination of the technical solution of any one embodiment with the technical solution of the other embodiment or embodiments is within the scope of the present application. While the application has been described in detail in the foregoing general description and specific examples, it will be apparent to those skilled in the art that modifications and improvements can be made thereto. Accordingly, such modifications or improvements may be made without departing from the spirit of the application and are intended to be within the scope of the application as claimed.
Claims (9)
1. The method for controlling the running speed of the hydrostatic traveling forklift truck is characterized by comprising the following steps of speed control when the forklift truck is shifted and switched, namely:
the gear signal of the gear shifting handle and the actual gear signal of the transfer case are fed back to the controller, the controller reads the rotating speed sensor signal of the traveling motor, judges whether the current vehicle is in a starting state or not, the controller judges whether the gear of the gear shifting handle is consistent with the actual gear of the transfer case or not, and when the controller judges that the vehicle is in the starting state and the gear of the gear shifting handle is inconsistent with the actual gear of the transfer case, the controller executes the following control logic: when the engine speed corresponding to the accelerator pedal is greater than a speed limit value, limiting the engine speed, limiting the maximum value of the hydraulic pump current at the same time, detecting the real-time speed of the traveling motor, and when the real-time speed of the traveling motor is greater than the speed limit value, reducing the request speed of the engine in each program cycle until the speed of the traveling motor is below the speed limit value, and maintaining the request speed of the engine;
when the gear of the gear shifting handle is consistent with the actual gear of the transfer case through the control logic, the control logic is exited, the engine request rotating speed is restored to be the same as the engine rotating speed calculated by the accelerator pedal, and the limitation on the maximum value of the hydraulic pump current is canceled.
2. The hydrostatic traveling forklift speed control method according to claim 1, wherein the transfer case has a first gear and a second gear, the transfer case is provided with a first gear switch sensor corresponding to the first gear and a second gear switch sensor corresponding to the second gear, the first gear switch sensor and the second gear switch sensor being electrically connected with the controller; when the actual gear of the transfer case is the first gear, the first gear sensor feeds back a signal to the controller; and when the actual gear of the transfer case is the second gear, the second gear sensor feeds back a signal to the controller.
3. The hydrostatic traveling forklift speed control method according to claim 1, wherein the traveling motor is mounted with a rotation speed sensor electrically connected to the controller such that the rotation speed of the traveling motor is measured by the rotation speed sensor and rotation speed information of the traveling motor is fed back to the controller to assist the controller in calculating a real-time vehicle speed.
4. The hydrostatic traveling forklift speed control method according to claim 1, further comprising a speed control step at acceleration of the forklift, comprising:
in the first acceleration stage, the engine is increased from a first rotating speed to a second rotating speed, and the hydraulic pump current and the engine rotating speed are in a linear proportional relation;
and a second acceleration stage in which the engine continues to rise from the second rotation speed to the third rotation speed while the hydraulic pump current is kept at a maximum value.
5. The method of claim 4, wherein the first rotational speed is an idle rotational speed of the engine or the first rotational speed is greater than the idle rotational speed of the engine.
6. The method for controlling the running speed of the hydrostatic traveling forklift according to claim 1, further comprising a speed control step when the forklift is decelerating, comprising a deceleration stage, specifically:
when the engine request speed is smaller than the engine actual speed, taking the value of subtracting the engine request speed from the engine actual speed as a judgment basis to control the current of the hydraulic pump to reduce the value every program cycle, and executing the following control logic: when the value obtained by subtracting the engine request speed from the engine actual speed is smaller than a first threshold value, the current reduction value of the hydraulic pump is a first fixed value every program cycle; when the value of the actual engine speed minus the requested engine speed is greater than a first threshold value, the current of the hydraulic pump is reduced by less than the first constant value every program cycle.
7. The hydrostatic traveling forklift speed control method according to claim 6, wherein, in the deceleration stage, when a value of an actual engine speed minus a requested engine speed is larger than a first threshold value and gradually increases, a current reduction value of the hydraulic pump per program cycle is smaller than the first fixed value and gradually decreases.
8. The method according to claim 6, wherein the speed control step during deceleration of the forklift further comprises a pedal braking phase, in particular:
when the engine request rotating speed is larger than the engine actual rotating speed, taking the value of subtracting the engine actual rotating speed from the engine request rotating speed as a judgment basis to control the current of the hydraulic pump to reduce the value every program cycle, and executing the following control logic after the controller detects a braking signal: when the value obtained by subtracting the actual engine speed from the engine request speed is smaller than a second threshold value, the current of the hydraulic pump is reduced to a second constant value every program cycle; when the difference of the engine request speed minus the engine actual speed is greater than a second threshold value, the current of the hydraulic pump per program cycle decreases by a value greater than the second constant value.
9. The hydrostatic traveling forklift speed control method according to claim 8, wherein, in the step-on pedal braking phase, when a difference of an engine request speed minus an engine actual speed is larger than a second threshold value and gradually increases, a current reduction value of the hydraulic pump per program cycle is larger than the second constant value and gradually increases.
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