Transmission control device for forklift

Abstract

This transmission control device for a forklift may eliminate a torque converter provided in a conventional transmission and an inching pedal provided in a forklift, and electronically implement functions performed by the torque converter and the inching pedal by controlling a proportional control valve connected to a clutch. According to the present invention, the removal of the torque converter provided in a conventional transmission and the inching pedal provided in a forklift improves fuel efficiency and enhances performance, and further reduces shift shock during gear shifting.

Description

Forklift transmission control device

[0001] The present invention relates to a transmission control device, and more specifically, to a transmission control device for a forklift that removes the torque converter and inching pedal provided in a conventional transmission and the inching pedal provided in a forklift, and electronically replaces the functions performed by the torque converter and the inching pedal by controlling a proportional control valve connected to a clutch.

[0002] Generally, since the engine's rotation direction is constant and the output is fixed, a transmission is essential to change the driving direction or driving speed.

[0003] Forward and backward driving of such engine-driven forklifts, the engine's output is transmitted to the drive shaft through a torque converter, transmission, and drive accelerator to operate the wheels.

[0004] A torque converter is an important device located between the engine and the transmission in a vehicle. It serves to transmit the engine's rotational force to the transmission and operates by utilizing fluid power to smoothly transfer force between the engine and the transmission.

[0005] However, since torque converters transmit power through fluid, slip (loss due to friction) can occur compared to mechanical connections, and there is a problem of reduced fuel efficiency as the engine's output is not fully transmitted to the wheels and some is lost.

[0006] Torque converters consist of various components such as fluid pumps, turbines, and stators, which increases the weight and complexity of the transmission system and leads to increased manufacturing costs.

[0007] Since torque converters transmit power using fluid rather than mechanical connections, the response during gear shifting may be relatively slow. Furthermore, if the fluid (oil) deteriorates or leaks, power transmission efficiency decreases, which can lead to performance degradation and damage.

[0008] The present invention aims to provide a transmission control device for a forklift that eliminates the torque converter and inching pedal provided in a conventional transmission and electronically replaces the functions performed by the torque converter and inching pedal by controlling a proportional control valve connected to a clutch.

[0009] A transmission control device for a forklift according to the features of the present invention for achieving the above objective is,

[0010] A dual clutch transmission comprising a first clutch of a first clutch pack and a second clutch of a second clutch pack, each comprising an input shaft connected to the engine of a forklift to transmit rotational power and multiple clutch discs that connect or disconnect the power of the input shaft to the wheel through an output shaft; and a control unit that controls the speed of the forklift by controlling a first proportional control valve that supplies hydraulic pressure to the first clutch pack when a brake pedal signal of an electrical signal generated when the brake pedal is pressed is received and a mast signal of an electrical signal generated by the operation of a mast operating lever is received, thereby adjusting the hydraulic pressure of the first clutch pack according to a clutch contact ratio of a different ratio—the clutch contact ratio is the coupling strength between the clutch disc and the gear formed on the same axis as the clutch pack—the control unit may allow the coupling strength between the clutch disc and the gear formed on the same axis as the clutch pack to vary according to the hydraulic pressure corresponding to the ratio of the clutch contact ratio.

[0011] The control unit can sequentially form the above-mentioned preset clutch contact ratio from a high value to a low value for the power transmission ratio.

[0012] The power shaft connected to the output shaft may further include a 3-stage clutch of a 3-stage clutch pack that transmits the power of the engine transmitted through the output shaft to the wheel on one side and changes the gear ratio of the dual clutch transmission.

[0013] With the above-described configuration, the present invention eliminates the torque converter equipped in a conventional transmission and the inching pedal equipped in a forklift, thereby enabling fuel efficiency savings and performance improvement, and has the effect of reducing shock during gear shifting.

[0014] FIG. 1 is a diagram showing the configuration of a forklift equipped with a dual clutch transmission according to an embodiment of the present invention.

[0015] FIG. 2 is a diagram showing the configuration of a transmission control device according to an embodiment of the present invention.

[0016] FIG. 3 is a diagram showing an electronic control method for processing the slip state of a clutch disc in a transmission control device according to an embodiment of the present invention.

[0017] FIG. 4 is a diagram showing a transmission electronic control method in a forklift without an inching pedal according to an embodiment of the present invention.

[0018] FIG. 5 is a diagram showing an electronic control method for preventing starting shock in a transmission control device according to an embodiment of the present invention.

[0019] The present invention is susceptible to various modifications and may have various embodiments; specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the invention to specific embodiments, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention. Similar reference numerals have been used for similar components in the description of each drawing.

[0020] Terms such as first, second, A, B, etc., may be used to describe various components, but said components shall not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0021] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0022] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0023] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0024] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding of the present invention, the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0025] Hereinafter, a transmission control device for a forklift according to an embodiment of the present invention will be described with reference to the attached drawings.

[0026] FIG. 1 is a diagram showing the configuration of a forklift equipped with a dual clutch transmission according to an embodiment of the present invention.

[0027] A transmission control device for a forklift can remove the torque converter and inching pedal provided in a conventional transmission and the inching pedal provided in the forklift, and electronically replace the functions performed by the torque converter and inching pedal by controlling a proportional control valve connected to a clutch.

[0028] A forklift (10) equipped with a dual clutch transmission according to an embodiment of the present invention may include a first clutch (120), a second clutch (130) of the dual clutch transmission (100), an output gear (140), a transmission output shaft (141), a third clutch (150), a power shaft (160), and a drive shaft (161).

[0029] The dual clutch transmission (100) may be composed of an input shaft (110) connected to the engine (20) of the forklift (10) to transmit rotational power, a first clutch (120) of a first clutch pack (123) composed of multiple clutch discs that connect or disconnect the power of the input shaft (110) to the wheel (30) through the output shaft (141), and a second clutch (130) of a second clutch pack (133).

[0030] The first clutch (120) may include a first clutch gear (121), a first clutch shaft (122), a first clutch pack (123), a reverse gear (124), and a first idle gear (125).

[0031] The first clutch (120) may include a first clutch gear (121), a first clutch shaft (122), a first clutch pack (123), a reverse gear (124), and a first idle gear (125).

[0032] The 2nd stage clutch (130) may include a 2nd stage clutch gear (131) fixed around the input shaft (110), a 2nd stage clutch shaft (132), a 2nd stage clutch pack (133), a forward gear (134), and a 2nd stage idler gear (135).

[0033] The input shaft (110) can be connected to the engine (20) of the forklift (10) to transmit rotational power.

[0034] The second clutch gear (131) is fixed around the input shaft (110) and can rotate according to the rotation of the input shaft (110).

[0035] The second-stage clutch shaft (132) is located on the same axis as the input shaft (110), is inserted into the second-stage clutch pack (133), and can have a forward gear (134) and a second-stage idler gear (135) installed around one side. The second-stage idler gear (135) can change the direction of rotation of the gear.

[0036] The 2-stage clutch pack (133) is coupled around the 2-stage clutch shaft (132) to connect the 2-stage clutch gear (131) and the forward gear (134) to the 2-stage clutch shaft (132).

[0037] The two-stage clutch pack (133) is divided into two spaces based on a central partition and forms a hydraulic piston device having a first and second piston in each of the two spaces, and each clutch disc is formed with a plurality of friction discs and steel plate discs alternately arranged on one surface of the first and second pistons.

[0038] The clutch disc can be formed by alternately arranging a disc-shaped friction disc with an open center and a steel plate disc, and forming a splined shaft in which multiple grooves and tooth-shaped protrusions are formed at regular intervals along the edge of the inner surface of the open center of the friction disc.

[0039] The second clutch gear (131) and the forward gear (134) form a splined gear with grooves formed at regular intervals along the outer edge that mesh with the protrusions of the splined shaft. The second clutch gear (131) and the forward gear (134) can be inserted into the open area in the center of the friction disc and the steel plate disc.

[0040] When hydraulic pressure is supplied to the first piston, the first piston moves to the left, moving the friction disc and the steel plate disc to the left, and the protrusion of the spline shaft of the friction disc engages with the groove of the spline gear of the second clutch gear (131), so that the second clutch gear (131) and the second clutch pack (133) can be connected.

[0041] When hydraulic pressure is supplied to the second piston, the second piston moves to the right, moving the friction disc and the steel plate disc to the right, and the projection of the spline shaft of the friction disc engages with the groove of the spline gear of the forward gear (134), so that the forward gear (134) and the two-stage clutch pack (133) can be connected.

[0042] When the hydraulic pressure is discharged, the first piston returns to its original position by the compression spring, and the projection of the spline shaft of the friction disc separates from the groove of the spline gear of the second clutch gear (131), so that the second clutch gear (131) and the second clutch pack (133) can be released.

[0043] When the hydraulic pressure is discharged, the second piston returns to its original position by the compression spring, and the projection of the spline shaft of the friction disc separates from the groove of the spline gear of the forward gear (134), so that the forward gear (134) and the two-stage clutch pack (133) can be released.

[0044] The 2nd stage clutch pack (133) can be connected to the 2nd stage clutch gear (131) and / or the forward gear (134) by pressurizing the internal clutch disc when hydraulic pressure is supplied.

[0045] The first stage clutch shaft (122) can be installed parallel to the second stage clutch shaft (132). The first stage clutch shaft (122) is inserted into the first clutch pack, and a reverse gear (124) and a first stage idler gear (125) are installed around one side, while a first stage clutch gear (121) is installed around the other side. The first stage idler gear (125) can change the direction of rotation of the gear.

[0046] The first stage clutch gear (121) is installed around the first stage clutch shaft (122) and can be engaged with the second stage clutch gear (131).

[0047] The reverse gear (124) can be rotatably installed around the first stage clutch shaft (122).

[0048] The first idler gear (125) is fixed around the first clutch shaft (122) and can be located on one side of the reverse gear (124).

[0049] The first clutch pack (123) is positioned around the first clutch shaft (122) to connect the first clutch gear (121) and / or the reverse gear (124) to the first clutch shaft (122).

[0050] Since the first stage clutch pack (123) has the same structure as the second stage clutch pack (133) described above, the space is separated into two sides based on the central partition, and a hydraulic piston device is formed in each of the two spaces, each having a first and second piston, and a clutch disc is formed in each of the first and second pistons, with a plurality of friction discs and steel plate discs alternately arranged on one side of each.

[0051] The clutch disc can be formed by alternately arranging a disc-shaped friction disc with an open center and a steel plate disc, and forming a splined shaft in which multiple grooves and tooth-shaped protrusions are formed at regular intervals along the edge of the inner surface of the open center of the friction disc.

[0052] The first stage clutch gear (121) and the reverse gear (124) form a splined gear with grooves formed at regular intervals along the outer circumference that mesh with the protrusions of the splined shaft. The first stage clutch gear (121) and the reverse gear (124) can be inserted into the open area in the center of the friction disc and the steel plate disc.

[0053] When hydraulic pressure is supplied to the first piston, the first piston moves to the left, moving the friction disc and the steel plate disc to the left, and the protrusion of the spline shaft of the friction disc engages with the groove of the spline gear of the first clutch gear (121), so that the first clutch gear (121) and the first clutch pack (123) can be connected.

[0054] When hydraulic pressure is supplied to the second piston, the second piston moves to the right, moving the friction disc and the steel plate disc to the right, and the projection of the spline shaft of the friction disc engages with the groove of the spline gear of the reverse gear (124), so that the reverse gear (124) and the first stage clutch pack (123) can be connected.

[0055] When the hydraulic pressure is discharged, the first piston returns to its original position by the compression spring, and the projection of the spline shaft of the friction disc is separated from the groove of the spline gear of the first clutch gear (121), so that the first clutch gear (121) and the first clutch pack (123) can be released.

[0056] When the hydraulic pressure is discharged, the second piston returns to its original position by the compression spring, and the projection of the spline shaft of the friction disc separates from the groove of the spline gear of the reverse gear (124), so that the reverse gear (124) and the first stage clutch pack (123) can be released.

[0057] The first stage clutch pack (123) can be connected to the first stage clutch gear (121) and / or reverse gear (124) by pressurizing the internal clutch disc when hydraulic pressure is supplied.

[0058] The output gear (140) can receive power by meshing with the forward gear (134) and the reverse gear (124). One end of the transmission output shaft (141) is connected to the output gear (140), and the other end is connected to the power shaft (160), so that the power transmitted from the output gear (140) can be transmitted to the power shaft (160).

[0059] When driving in forward 1st gear, the 2nd gear clutch pack (133) is connected to the forward clutch gear, and the 1st gear clutch pack (123) can be connected to the 1st gear clutch gear (121).

[0060] When rotational power is input, power is transmitted to the input shaft (110), 2nd stage clutch gear (131), 1st stage clutch gear (121), 1st stage clutch pack (123), 1st stage clutch shaft (122), 2nd stage clutch pack (133), forward gear (134), output gear (140), and transmission output shaft (141) to drive the 1st stage forward.

[0061] When driving in forward 2nd gear, the 2nd gear clutch pack (133) is connected to the 2nd gear clutch gear (131) and the forward gear (134), and the 1st gear clutch pack (123) is disconnected from the 1st gear clutch gear (121) and the reverse gear (124). When rotational power is input, power is transmitted to the input shaft (110), the 2nd gear clutch gear (131), the 2nd gear clutch shaft (132), the forward gear (134), the output gear (140), and the transmission output shaft (141) to drive forward 2nd gear.

[0062] When driving in reverse gear 1, the 2nd gear clutch pack (133) is disconnected from the 2nd gear clutch gear (131) and the forward gear (134), and the 1st gear clutch pack (123) can be connected to the 1st gear clutch gear (121) and the reverse gear (124). When rotational power is input, power is transmitted to the input shaft (110), 2nd gear clutch gear (131), 1st gear clutch gear (121), 1st gear clutch pack (123), 1st gear clutch shaft (122), reverse gear (124), output gear (140), and transmission output shaft (141) to drive in reverse gear 1.

[0063] When driving in reverse 2nd gear, the 2nd gear clutch pack (133) is connected to the 2nd gear clutch gear (131), and the 1st gear clutch pack (123) can be connected to the reverse gear (124). When rotational power is input, power is transmitted to the input shaft (110), 2nd gear clutch gear (131), 2nd gear clutch pack (133), 2nd gear clutch shaft (132), 2nd gear idler gear (135), 1st gear idler gear (125), 1st gear clutch shaft (122), 1st gear clutch pack (123), reverse gear (124), output gear (140), and transmission output shaft (141) to drive in reverse 1st gear.

[0064] The power shaft (160) connected to the output shaft (141) may include a 3-stage clutch (150) equipped with a 3-stage clutch pack (152) that transmits power from the engine (20) transmitted through the output shaft (141) to the wheel (30) on one side and changes the gear ratio of the dual clutch transmission (100). The gear ratio may be a value representing the ratio of rotational speed and torque between two gears meshed together.

[0065] One end of the power shaft (160) is vertically engaged with a gear, and both ends are connected to the wheel (30) by a drive shaft (161).

[0066] FIG. 2 is a diagram showing the configuration of a transmission control device according to an embodiment of the present invention.

[0067] A transmission control unit (TCU, Transmission Control Unit) (170) according to an embodiment of the present invention may include an input RPM (revoltions per minute) sensor (171), an output RPM sensor (172), a first proportional control valve (173), a second proportional control valve (174), a third proportional control valve (175), a storage unit (176), and a control unit (177).

[0068] The input RPM sensor (171) is installed on the input shaft (110) of the transmission and can measure the rotational speed of the engine (20) entering the transmission from the engine (20) (S101). The input RPM sensor (171) is located on the input shaft (110) inside the transmission and can detect the speed generated when the engine (20) rotates and convert it into an electrical signal.

[0069] The output RPM sensor (172) is installed on the output shaft (141) of the transmission and can measure the number of rotations of the output shaft (141) transmitted from the transmission to the wheel (30) (S102). The output RPM sensor (172) is used to determine the speed and driving status of the forklift (10) by measuring the number of rotations of the output shaft (141).

[0070] The first proportional control valve (173), the second proportional control valve (174), and the third proportional control valve (175) may be solenoid valves, and may further be equipped with a hydraulic pump (not shown) that supplies hydraulic pressure to each.

[0071] One side of the first proportional control valve (173) may be connected to the first stage clutch pack (123), and the other side may be connected to the storage unit (176).

[0072] The first proportional control valve (173) can supply oil stored in the storage unit (176) to the first stage clutch pack (123) at a constant hydraulic pressure according to the control of the control unit (177).

[0073] When hydraulic pressure is supplied to the hydraulic piston device of the first stage clutch pack (123), the clutch disc is moved in one direction by the piston so that the spline shaft of the clutch disc can be engaged with the spline gear of the first stage clutch gear (121) and / or the spline gear of the reverse gear (124).

[0074] One side of the second proportional control valve (174) may be connected to the two-stage clutch pack (133), and the other side may be connected to the storage unit (176).

[0075] The second proportional control valve (174) can supply oil stored in the storage unit (176) to the two-stage clutch pack (133) at a constant hydraulic pressure according to the control of the control unit (177).

[0076] When hydraulic pressure is supplied to the hydraulic piston device of the 2nd stage clutch pack (133), the clutch disc is moved in one direction by the piston so that the spline shaft of the clutch disc can be engaged with the spline gear of the 2nd stage clutch gear (131) and / or the spline gear of the forward gear (134).

[0077] One side of the third proportional control valve (175) may be connected to the 3rd stage clutch pack (152), and the other side may be connected to the storage unit (176).

[0078] The third proportional control valve (175) can supply oil stored in the storage unit (176) to the 3rd stage clutch pack (152) at a constant hydraulic pressure according to the control of the control unit (177).

[0079] The first proportional control valve (173), the second proportional control valve (174), and the third proportional control valve (175) control the hydraulic pressure supplied to the clutch pack to provide the pressure required for clutch operation, and the hydraulic pressure is transmitted to the clutch according to the control of the control unit (177) to compress or release the clutch disc of the clutch pack. When the hydraulic pressure increases, the clutch engages more strongly, and when the hydraulic pressure decreases, the clutch disengages or slips.

[0080] The storage unit (176) stores the oil supplied by the 1st stage clutch pack (123), 2nd stage clutch pack (133), and 3rd stage clutch pack (152).

[0081] When the control unit (177) receives a brake pedal signal, which is an electrical signal generated when the brake pedal (180) is pressed, and receives a mast signal, which is an electrical signal generated by the operation of the mast operating lever (181), it controls the first proportional control valve (173) that supplies hydraulic pressure to the first clutch pack (123) to control the hydraulic pressure of the first clutch pack (123) according to clutch contact rates of different ratios, thereby controlling the speed of the forklift (10). Here, the clutch contact rate may be the coupling strength between the clutch disc and the gear formed on the same axis as the clutch pack.

[0082] The control unit (177) can change the coupling strength between the gears formed on the same axis as the clutch pack and the clutch disc according to the hydraulic pressure corresponding to the ratio of the clutch contact rate.

[0083] The control unit (177) can control the first proportional control valve (173) to adjust the amount of hydraulic pressure supplied to the hydraulic piston device installed inside the first stage clutch pack (123) according to the clutch contact rate (70% -> 50% -> 30%).

[0084] The control unit (177) can change the coupling strength between the clutch disc of the first stage clutch pack (123) and the first stage clutch gear (121) or reverse gear (124) according to the controlled hydraulic pressure.

[0085] For example, assuming the clutch contact rate is 50%, the control unit (177) controls the first proportional control valve (173) to introduce 50% of the amount of oil into the piston, and the spline shafts of 5 of the friction discs among the total friction discs (10) can be coupled to the spline gear of the first clutch gear (121) or the spline gear of the reverse gear (124).

[0086] For example, assuming the clutch contact rate is 30%, the control unit (177) controls the first proportional control valve (173) to introduce 30% of the amount of oil into the piston, and the spline shafts of three of the total friction discs (10) can be coupled to the spline gear of the first clutch gear (121) or the spline gear of the reverse gear (124).

[0087] The control unit (177) can control the first proportional control valve (173) to sequentially apply the clutch contact rate (70% -> 50% -> 30%) in order from high value to low value.

[0088] FIG. 3 is a diagram showing an electronic control method for processing the slip state of a clutch disc in a transmission control device according to an embodiment of the present invention.

[0089] The forklift (10) has a preset maximum load capacity. The maximum load of the forklift (10) may occur in the following situations, which may cause the engine (20) to turn off.

[0090] The maximum load of the forklift (10) may be when handling a load exceeding the load limit, when the hydraulic system is overloaded, when transporting heavy loads on a ramp, when the engine (20) overheats or there is a problem with the cooling system, etc.

[0091] After checking the maximum load of the forklift (10) (S100), the electronic control method for handling the slip state of the clutch disc in the transmission control unit (170) is described as follows.

[0092] The control unit (177) can determine whether the clutch disc is slipping by using the rotational speed of the engine (20) and the rotational speed of the transmission output shaft (141). Slipping may mean that the clutch is slipping or failing to properly transmit power if the clutch disc is worn out or not properly engaged.

[0093] The control unit (177) receives the Input RPM from the Input RPM sensor (171) and the Output RPM from the Output RPM sensor (172), calculates the difference between the Input RPM and the Output RPM, and determines whether the calculated difference is greater than or equal to a preset threshold value to determine the slip state of the clutch disc (S103). The threshold value may be a reference value indicating the slip state of the clutch disc, which is a state in which abnormal friction occurs on the clutch disc and may cause strain on the engine (20). The threshold value is preset in advance.

[0094] For example, the control unit (177) can determine that slip of the clutch disc has occurred when the Input RPM is 1900 and the Output RPM is 100, the difference between the Input RPM and the Output RPM is 1800, and the preset threshold value is 500 RPM.

[0095] In another embodiment, the control unit (177) can determine the slip state of the clutch disc by determining whether the calculated difference value is greater than or equal to a preset threshold value and whether this state exceeds a preset slip holding time (e.g., 2 to 3 seconds, etc.).

[0096] For example, if the Input RPM is 1800 and the Output RPM is 100 and the preset threshold is 500 RPM, the control unit (177) determines that the difference between the Output RPM and the Input RPM exceeds the threshold, and counts time from the point at which this state is determined to determine whether the state exceeds the preset slip holding time. If the state exceeds the preset slip holding time, the control unit (177) can determine that the clutch disc is in a slip state.

[0097] In another embodiment, the control unit (177) calculates the difference value obtained by subtracting the input RPM from the output RPM, and if the calculated difference value is greater than or equal to a preset threshold value and this state exceeds a preset slip holding time, it receives oil temperature information from a temperature sensor (not shown), and if the received temperature information exceeds a preset reference temperature (determining that the friction heat temperature of the clutch disc is high), it can determine that the clutch disc is in a slip state. The temperature sensor is installed on one side of the clutch pack to measure the temperature of the oil inside the clutch pack.

[0098] If the clutch disc remains in a slip state for a long time, the engine (20) may stop.

[0099] The control unit (177) can detect a situation where the clutch needs to be released (e.g., shifting, stopping, neutral, etc.) when it is determined that the clutch disc is in a slip state.

[0100] The control unit (177) monitors the state of the forklift (10) (e.g., speed, gear position, brake state, etc.) and, when it determines that the clutch disc is in a slip state, can transmit a command to release the clutch pressure at an appropriate time by controlling a proportional control valve that supplies hydraulic pressure to the clutch connecting the input shaft (110) (S104). The clutch pressure releases the clutch holding the input shaft (110).

[0101] The control unit (177) controls the proportional control valve to reduce the hydraulic pressure, thereby releasing the hydraulic pressure applied to the clutch from the transmission, and thus preventing the clutch from transmitting power (S105). This process causes the clutch to disconnect the connection between the engine (20) and the transmission, and the forklift (10) is in a neutral state.

[0102] The control unit (177) can execute a parking mode (142) when the forklift (10) is in a neutral state. The parking mode (142) controls a proportional control valve under the control of the control unit (177) to cut off the supply of hydraulic fluid, performs a clutch release function that disconnects the engine (20) and the transmission, and activates the service brakes coupled inside both wheels (30) to prevent the forklift (10) from moving (S106). In this state, the forklift (10) does not roll even if the engine (20) is in an idle state.

[0103] If the control unit (177) determines that there is no slip of the clutch disc, it can control it with a preset maximum load (S107).

[0104] The existing forklift (10) is equipped with an inching pedal and a mast operating lever (181). The inching pedal and mast operating lever (181) used in the forklift (10) are important components that control the movement of the forklift (10) and the loading and unloading of goods. Each component and its method of operation is described as follows.

[0105] When the inching pedal of the forklift (10) is pressed, the driving speed of the forklift (10) can be finely adjusted. The more the inching pedal is pressed, the more the power of the forklift (10) is cut off and the forklift (10) stops. When the pedal is pressed less, only some of the power of the forklift (10) is cut off and the speed is reduced. When the inching pedal is slowly released, the forklift (10) can drive again.

[0106] The inching pedal is mainly used when the forklift (10) needs to move at a very low speed when lifting or lowering a load, and very precise positional movement can be achieved by adjusting the inching pedal little by little.

[0107] The mast operating lever (181) is a lift lever that moves the mast up and down to raise or lower the fork, and a tilt lever that tilts the mast forward and backward to adjust the angle of the fork. The fork is a mechanism for carrying goods, and the mast is attached to one end.

[0108] The forklift (10) of the present invention has no torque converter and no inching pedal, and a mast operating lever (181) is formed. With reference to FIG. 4 below, the transmission will be explained in detail in place of the inching pedal removed from the forklift (10).

[0109] FIG. 4 is a diagram showing a transmission electronic control method in a forklift without an inching pedal according to an embodiment of the present invention.

[0110] The first stage clutch (120) is engaged to start the forklift (10) and proceed (S200).

[0111] The control unit (177) determines whether the brake pedal signal of the electrical signal generated when the brake pedal (180) is pressed is received (S201), and if the brake pedal signal is received, it can determine whether the mast signal of the electrical signal generated by the operation of the mast operating lever (181) is received (S202).

[0112] The control unit (177) can recognize the driving state when the brake pedal signal is not received.

[0113] When a mast signal is received, the control unit (177) controls the first proportional control valve (173) to supply hydraulic pressure to the first stage clutch pack (123), and accordingly, the first stage of the clutch can be driven (forward / reverse). At this time, the control unit (177) controls the first proportional control valve (173) to control the clutch contact rate inside the first stage clutch pack (123) and can control the speed of the forklift (10) (S203).

[0114] The control unit (177) can precisely control the power transmission of the forklift (10) by sequentially adjusting the clutch contact rate in the order of preset clutch contact rates (70% -> 50% -> 30%). To this end, the control unit (177) controls the first proportional control valve (173) to regulate the hydraulic pressure transmitted to the clutch actuator (not shown) and can finely control the degree of engagement of the gear formed on the same axis as the clutch disc and the clutch pack. As a result, the forklift (10) is made to start, accelerate, and decelerate smoothly and efficiently.

[0115] Specifically, at a 70% clutch contact rate, the control unit (177) controls the first proportional control valve (173) to increase the hydraulic pressure transmitted to the clutch actuator (not shown) so that the clutch disc is strongly coupled to the gear formed on the same axis as the clutch pack, and 70% of the engine power can be transmitted to the transmission.

[0116] In the 50% clutch contact rate, the control unit (177) controls the first proportional control valve (173) to adjust the hydraulic pressure transmitted to the clutch actuator (not shown) to an intermediate level so that the clutch disc is engaged to a gear formed on the same axis as the clutch pack at an intermediate level, and 50% of the engine power can be transmitted to the transmission. In this state, although part of the clutch disc is not engaged to the gear, part of the engine power is transmitted to the transmission and the forklift (10) is accelerated.

[0117] In the case of a 30% clutch contact rate, the control unit (177) controls the first proportional control valve (173) to lower the hydraulic pressure transmitted to the clutch actuator (not shown) so that the clutch disc is weakly engaged with the gear formed on the same axis as the clutch pack, and 30% of the engine power can be transmitted to the transmission. In this state, since the clutch disc is weakly engaged with the gear, the input shaft (110) rotates slower than the engine (20), and slight slip may occur, and the forklift (10) can move smoothly and slowly.

[0118] Next, the control unit (177) controls the first proportional control valve (173) to cut off the hydraulic pressure transmitted to the clutch actuator (not shown), thereby disengaging the clutch disc from the gear formed on the same axis as the clutch pack, and the transmission becomes neutral, in which engine power is not transmitted to the transmission.

[0119] In a conventional forklift (10), power is transmitted to the engine (20) when the brake is applied, causing clutch slip, and if clutch slip continues, the engine (20) may be turned off.

[0120] However, the forklift (10) of the present invention can prevent the engine (20) from turning off because the transmission is in a neutral state even when the brake is applied and the engine (20) is operated.

[0121] When the control unit (177) receives the Output RPM from the Output RPM sensor (172), it can see that the Output RPM is 0 (forklift stopped state) (S204).

[0122] When the clutch disc is disengaged from the gear from 100% clutch contact rate to 0% clutch contact rate, the forklift (10) stops abruptly, and the forklift (10) is unable to perform precision work at low speed.

[0123] Due to the nature of the work, the forklift (10) performs precision work such as lifting or moving objects with its forks while maintaining a very low speed, such as 1 km or 1.5 km, and this role is performed by the inching pedal equipped in the conventional forklift (10).

[0124] Inching operation refers to a state in which the power of the forklift (10) is cut off by pressing the inching pedal while pressing the brake pedal (180) when the forklift (10) is lifting an object by inserting the forks into it or lowering and removing an object by the forks, and the forklift (10) is moving at a low speed. The inching pedal performs the function of slowly disengaging the clutch to slowly cut off the power.

[0125] In the present invention, an electronic control method is applied to finely adjust the speed of the forklift using a clutch contact ratio by utilizing a proportional control valve, replacing the role of the inching pedal and inching operation. When the brake is applied while the forklift (10) is in a state where the clutch disc is slightly attached to a gear formed on the same axis as the clutch pack (moving at a low speed), the forklift (10) can be easily stopped.

[0126] Receiving the aforementioned brake signal and mast signal may mean performing an incoming operation by slowly engaging the clutch.

[0127] The control unit (177) determines whether it receives an accelerator signal from the accelerator pedal sensor (184) mounted on the accelerator (S205), and if it receives an accelerator signal, it controls the first proportional control valve (173) to supply hydraulic pressure to the first stage clutch pack (123), thereby enabling the first stage clutch (120) to be driven (S206).

[0128] If the brake pedal signal and the mast signal are not received, the first stage clutch (120) can be engaged and driven to start the forklift (10).

[0129] When the control unit (177) determines that a mast signal is not received, it controls the first proportional control valve (173) to cut off the supply of hydraulic pressure to the first stage clutch pack (123), thereby disengaging the clutch disc from the gear formed on the same axis as the clutch pack from 100% clutch contact rate to 0% clutch contact rate, and the transmission becomes neutral (clutch first stage non-contact) (S207).

[0130] FIG. 5 is a diagram showing an electronic control method for preventing starting shock in a transmission control device according to an embodiment of the present invention.

[0131] The forklift (10) may be equipped with a forward lever (182) as a gear selection device, and the forward operation of the forklift (10) can be performed by operating the forward lever (182) (S300).

[0132] When the position of the forward lever (182) is detected by the gear selection position sensor (183), the control unit (177) controls the first proportional control valve (173) to supply hydraulic pressure to the first clutch pack (123), and the first clutch pack (123) is connected to the first clutch gear (121), and controls the second proportional control valve (174) to supply hydraulic pressure to the second clutch pack (133), and the second clutch pack (133) is connected to the forward gear (134).

[0133] When rotational power of the engine (20) is input, power is transmitted to the input shaft (110), 2nd stage clutch gear (131), 1st stage clutch gear (121), 1st stage clutch pack (123), 1st stage clutch shaft (122), 2nd stage clutch pack (133), forward gear (134), output gear (140), and transmission output shaft (141) to drive the 1st stage forward (1st stage forward drive). That is, power can be transmitted so that the forklift (10) can move forward.

[0134] The control unit (177) determines whether it receives an accelerator signal from an accelerator pedal sensor (184) mounted on the accelerator, and if it does not receive an accelerator signal, it controls the first proportional control valve (173) to supply hydraulic pressure to the first clutch pack (123) and can control the power transmission of the forklift (10) by adjusting to a preset clutch contact rate (30%, 50%, 70%, etc.) (S301).

[0135] The control unit (177) can cause the forklift (10) to sway due to the starting shock if the clutch is suddenly engaged from a 0% clutch contact rate to a 100% clutch contact rate while the engine (20) is rotating. To prevent this problem, the forklift (10) of the present invention can start smoothly and slowly as the clutch contact time increases by adjusting the clutch contact rate.

[0136] The control unit (177) receives a rotational speed from a speed sensor located on one side of the power shaft (160) or wheel (30) (or receives the number of rotations of the output shaft (141) from the output RPM sensor (172)), and can calculate the current speed of the forklift (10) by processing the received rotational speed or the received number of rotations.

[0137] The control unit (177) determines whether the current speed is within the error range of the legal allowance (S302), and if the current speed is within the error range of the legal allowance, maintains the first-stage clutch contact (S303), and if it is outside the error range of the legal allowance, can increase or decrease the first-stage clutch contact rate (S304). The legal allowance may be 1.6 km / h.

[0138] The control unit (177) determines whether it receives an accelerator signal from the accelerator pedal sensor (184) mounted on the accelerator (S305), and if it receives an accelerator signal, it maintains the first-stage clutch contact (S306) and increases the forklift speed (S305), and if it does not receive an accelerator signal, it maintains the first-stage clutch contact (S308) and can maintain the forklift speed (1.6 km / h) as is (S309).

[0139] The technical features disclosed in each embodiment of the present invention are not limited to that embodiment only, and as long as they are not mutually incompatible, the technical features disclosed in each embodiment may be combined and applied to different embodiments.

[0140] Therefore, in each embodiment, the technical features are described primarily, but as long as the technical features are not mutually incompatible, they may be combined and applied together.

[0141] The present invention is not limited to the embodiments described above and the attached drawings, and various modifications and variations may be possible from the perspective of those skilled in the art to which the present invention belongs. Accordingly, the scope of the present invention should be defined not only by the claims of this specification but also by equivalents thereof.

Claims

1. A dual clutch transmission comprising an input shaft connected to the engine of a forklift to transmit rotational power, a first-stage clutch of a first-stage clutch pack composed of multiple clutch discs that connect or disconnect the power of the input shaft to the wheels through an output shaft, and a second-stage clutch of a second-stage clutch pack; and The system further includes a control unit that controls the speed of the forklift by controlling a first proportional control valve that supplies hydraulic pressure to the first clutch pack when a brake pedal signal, which is an electrical signal generated when the brake pedal is pressed, is received and a mast signal, which is an electrical signal generated by the operation of the mast operating lever, is received, thereby adjusting the hydraulic pressure of the first clutch pack according to clutch contact ratios of different ratios—the clutch contact ratio is the coupling strength between the clutch disc and the gear formed on the same axis as the clutch pack—and The above control unit determines that the coupling strength between the gears formed on the same axis as the clutch pack and the clutch disc varies according to the hydraulic pressure corresponding to the ratio of the clutch contact rate. Transmission control device for forklifts.

2. In Paragraph 1, The control unit above forms the clutch contact rates of different ratios sequentially from a high value to a low value. Transmission control device for forklifts.

3. In Paragraph 1, A transmission control device for a forklift, comprising a power shaft connected to the output shaft, which transmits the power of the engine transmitted through the output shaft to the wheel on one side, and further including a 3-stage clutch of a 3-stage clutch pack in which the gear ratio of the dual clutch transmission is converted.

4. In Paragraph 1, An Input RPM (Revoltions Per Minute) sensor installed on the input shaft to measure the rotational speed of the engine entering the dual clutch transmission from the engine; and It further includes an Output RPM sensor installed on the output shaft to measure the rotational speed of the output shaft transmitted from the dual clutch transmission to the wheel, The above control unit is, A transmission control device for a forklift that determines whether the clutch disc slips using the rotational speed of the engine and the rotational speed of the output shaft.

5. In Paragraph 4, The above control unit is, A transmission control device for a forklift that receives an Input RPM from an Input RPM sensor and an Output RPM from an Output RPM sensor, calculates the difference between the Input RPM and the Output RPM, and determines whether the calculated difference is greater than or equal to a preset threshold value to determine the slip state of the clutch disc.

6. In Paragraph 4, A transmission control device for a forklift that receives an Input RPM from an Input RPM sensor and an Output RPM from an Output RPM sensor, calculates the difference between the Input RPM and the Output RPM, and determines whether the calculated difference is greater than or equal to a preset threshold value and whether this state exceeds a preset slip holding time to determine the slip state of the clutch disc.

7. In Paragraph 5 or 6, The above control unit is, A transmission control device for a forklift that, when the clutch disc is determined to be in a slip state, controls a proportional control valve that supplies hydraulic pressure to the clutch connecting the input shaft to transmit a command to release the clutch pressure at an appropriate time, and disconnects the connection between the engine and the dual clutch transmission by the clutch so that the forklift becomes neutral.

8. In Paragraph 1, The above control unit is, It determines whether an accelerator signal is received from an accelerator pedal sensor mounted on the accelerator, and if the accelerator signal is not received, controls the first proportional control valve to supply hydraulic pressure to the first stage clutch pack and controls the power transmission of the forklift by adjusting to a preset clutch contact rate. A transmission control device for a forklift that receives a rotational speed from a speed sensor located on one side of a power shaft connected to the output shaft or a wheel, processes the received rotational speed to calculate the current speed of the forklift, determines whether the calculated current speed is within the error range of a legally permissible value, maintains a first-stage clutch contact if the current speed is within the error range of a legally permissible value, and increases or decreases the first-stage clutch contact rate if it is outside the error range of a legally permissible value.

9. In Paragraph 4, The above control unit is, It determines whether an accelerator signal is received from an accelerator pedal sensor mounted on the accelerator, and if the accelerator signal is not received, controls the first proportional control valve to supply hydraulic pressure to the first stage clutch pack and controls the power transmission of the forklift by adjusting to a preset clutch contact rate. A transmission control device for a forklift that receives the rotational speed of an output shaft from the output RPM sensor, processes the received rotational speed to calculate the current speed of the forklift, determines whether the calculated current speed is within the error range of a legally permissible value, maintains first-stage clutch contact if the current speed is within the error range of a legally permissible value, and increases or decreases the first-stage clutch contact rate if the current speed is outside the error range of a legally permissible value.

10. In Paragraph 8 or 9, The above control unit is, A transmission control device for a forklift that determines whether an accelerator signal is received from the accelerator pedal sensor, and if the accelerator signal is received, maintains 1st gear clutch contact and increases the forklift speed, and if the accelerator signal is not received, maintains 1st gear clutch contact and maintains the forklift speed (1.6 km / h) as is.

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