Assembly design method of improved Marler type lifting mechanism on load-carrying dumper

Abstract

The invention discloses a method for assembling and designing an improved Marler type lifting mechanism on a load-carrying dumper, which comprises the following steps of: improving the Marler type lifting mechanism which comprises a triangular arm, a lifting hydraulic cylinder and a pull rod; determining preliminary design parameters; establishing a coordinate system, determining the coordinate of a connecting pivot of the triangular arm and the container, and determining the coordinates of an oil cylinder fixed hinge pivot and a pull rod fixed hinge pivot; determining the stroke of the oil cylinder; and calculating the movement and stress of the Marler lifting mechanism, solving the maximum oil cylinder thrust Fmax and the maximum pull rod tension F1max, and respectively taking the maximum oil cylinder thrust Fmax and the maximum pull rod tension F1max as load bases for checking the strength of a hydraulic system and the pull rod. Compared with a traditional Marler lifting mechanism, the improved lifting mechanism has the advantages that the initial length of the hydraulic cylinder can be shortened on the premise that the lifting force coefficient is not increased, and the installation space needed by the mechanism is small.

Description

Technical Field

[0001] The invention belongs to the field of assembly of a load-carrying dump truck, and in particular relates to an assembly design method of an improved Mallery lifting mechanism on a load-carrying dump truck. Background Art

[0002] A dump truck is a vehicle that unloads goods by itself through hydraulic or mechanical lifting, also known as a dump truck. In recent years, the compound growth rate of the global dump truck market has exceeded 6%, and domestic sales have shown a high-speed growth trend, with annual sales of 230,000 vehicles, accounting for about 44% of the global market share. In recent years, due to the increase in infrastructure projects around the world and the support of national policies, the dump truck market has developed rapidly. The dump truck market is divided into road dump trucks and off-road dump trucks. Road transport trucks are mainly used for construction projects and the transportation of goods, while off-road dump trucks are mainly used in mines, coal mines, water conservancy, etc. Among them, road dump trucks occupy the main market in the world. With the country's increased investment in infrastructure and the advancement of urbanization, it is expected that the demand for road dump trucks will continue to grow. The lifting mechanism is an important mechanism of the dump truck. The actual maximum tipping force output by its unloading power system is the main factor affecting the working efficiency of the whole vehicle, and the safety of personnel and facilities. If it is not designed properly, the cylinder pressure or hinge support reaction force will be too large, causing local strength failure, and then causing early fracture of the vehicle structure. Therefore, the design quality of the lifting mechanism is directly related to the performance and overall layout of the dump truck.

[0003] The Mallery lifting mechanism has the advantages of labor saving, good oil pressure characteristics, gentle pressure change with lifting angle, and small maximum thrust of the cylinder, but its cylinder swing angle is large and the piston stroke is large. At present, the number of carriages using the Mallery structure is gradually increasing, so the following requirements need to be met:

[0004] 1) The lifting mechanism is used to flip the carriage, and the installation space cannot exceed the space between the bottom of the carriage and the main frame.

[0005] 2) The structure should be compact and reliable, and have good power transmission performance.

[0006] 3) After dumping, it can be reset.

[0007] 4) When at the maximum lifting angle, the lowest point of the rear panel of the vehicle compartment maintains a certain unloading height from the ground.

[0008] In the past, the main design and analysis methods for lifting mechanisms included mathematical analysis, ruler and compass drawing, and engineering test methods. However, the mathematical calculation formulas were relatively complex and were rarely used in actual engineering calculations. Although the drawing method was simple, it was rarely used in actual production due to the large errors caused by the limited accuracy of the tools. The test method was even less used in actual production due to its cost and long experimental cycle. In recent years, with the development of computer and CAE virtual prototype technology, more design methods for lifting mechanisms have been derived, such as CAD-based mathematical model analysis, C-based parametric analysis, and Creo-based virtual prototype analysis. At present, more and more dump trucks at home and abroad have begun to study and adopt lightweight design, and the materials are mainly aluminum alloy, high-strength steel, plastic and composite materials. In recent years, the domestic dump truck industry has developed rapidly, and the demand has increased year by year. With the changes in the market, resources and environment, objective requirements for lightweight and heavy-duty dump trucks have been put forward. Summary of the invention

[0009] Purpose of the invention: The purpose of the present invention is to provide an assembly design method for an improved Mallery lifting mechanism in a load-carrying dump truck. Compared with the traditional Mallery lifting mechanism, the improved lifting mechanism can shorten the initial length of the hydraulic cylinder without increasing the lifting force coefficient, and the installation space required by the mechanism is small. Based on the analysis of the mechanism motion and force, a multi-objective optimization mathematical model of the improved lifting mechanism is established to realize the actual motion of the mechanism, eliminate possible problems in the design in the bud, and shorten the development cycle of product design.

[0010] Technical solution: The assembly design method of an improved Mallery lifting mechanism on a load-carrying dump truck of the present invention comprises the following steps:

[0011] Step 1: Improve the Mallery lifting mechanism, including a triangular arm, a lifting hydraulic cylinder and a pull rod;

[0012] Step 2: Determine preliminary design parameters;

[0013] Step 3: Establish a coordinate system, determine the coordinates of the fulcrum connecting the triangular arm and the cargo box, and determine the coordinates of the fixed hinge fulcrum of the oil cylinder and the fixed hinge fulcrum of the pull rod;

[0014] Step 4: Determine the cylinder stroke;

[0015] Step 5: Calculate the movement and force of the Mallery lifting mechanism and find the maximum cylinder thrust F max and the maximum tie rod tension F 1max , and use this as the load basis for the hydraulic system and tie rod strength verification respectively.

[0016] Furthermore, step 1 is specifically as follows: improving the Mallery lifting mechanism, including a triangular arm, a lifting hydraulic cylinder and a pull rod, wherein a hinge point between the lifting hydraulic cylinder and the triangular arm is below the top edge of the triangular arm.

[0017] Further, step 2 is specifically as follows: the preliminary design parameters include the factory-determined maximum total mass m α 、Loading mass m θ , total lifting mass m ω , Maximum lift angle θ max , where the lifting mass m ω = load mass + car mass; initially determine the lengths of the three sides of the triangular arm a, b, c and the length of the pull rod d, and the proportional relationship of the three sides is: a:b:c=1.5:3:4.

[0018] Furthermore, step 3 specifically includes the following steps:

[0019] Step 3.1, select the cargo box flip center O1 near the rear suspension rear support point above, center O 1 The projection O in the lower plane of the sub-beam is taken as the origin of the coordinate system, and the X-axis is along the lower plane of the sub-beam and points to the forward direction of the vehicle;

[0020] Step 3.2, determine the coordinates of the fulcrum A where the triangular arm is connected to the cargo box (x A ,y A ): Select x A Considering the layout space of the triangular arm, select a larger x A value to increase the lifting arm ON, select y A This is the maximum value allowed by the structure, as long as it does not interfere with the bottom of the cargo box;

[0021] Step 3.3, determine the coordinates of the cylinder fixed hinge point E and the tie rod fixed hinge point D (x E ,yE)、(x D ,yD) The coordinates of points E and D determine the cylinder force F and the rod force F 1 The position of the action line of the hinge point is set, and the distance between the two points is pulled apart under the premise that the hinge point installation structure allows, so that the (α+β) angle is reduced, so that F and F 1 Forming a larger combined force R.

[0022] Further, step 4 is specifically as follows: the cylinder stroke is the difference between the highest lifting position and the actual total length of the cylinder at the original position; the highest lifting position of the triangular arm is obtained by using a graphical method; the steps are as follows: 1 A rotates around the center O 1 Turn 50° to OA 1 , with A 1 D is the center of the circle and c is the radius. D is the center of the circle and BD is the radius. I Arc, two arcs intersect B1 Point A 1 , B 1 With a as the center and a and b as the radius, we can get the intersection point C. 1 , ΔA 1 B 1 C 1 This is the highest lifting position of the triangular arm. Connect EC 1 , that is, the maximum extension length of the cylinder piston rod is L = EC 1 -EC; obtain the coordinate values ​​of each hinge point in each direction from the drawing method, and then obtain the geometric dimensions of the pull rod and the triangular arm, and perform analytical calculation when the lifting angle θ is 0° and the maximum lifting angle θ max The maximum cylinder thrust and maximum rod pull force change between .

[0023] Furthermore, step 5 is specifically as follows:

[0024] Step 5.1, calculate the coordinates of the hinge point A between the triangular arm and the carriage and the coordinates of the center of mass of the lifting weight point G when the lifting angle is θ;

[0025] Step 5.2, calculate the tipping force R;

[0026] Step 5.3, calculate the cylinder thrust F;

[0027] Step 5.4: Calculate the tension F of the pull rod 1 ;

[0028] Step 5.5: Solve the force calculation formula of the cylinder and the tie rod at any lifting angle θ. When the lifting angle θ is between 0° and the maximum θ max When the change between max and the maximum tie rod tension F 1max , and use this as the load basis for the hydraulic system and tie rod strength verification respectively.

[0029] Furthermore, step 5.1 is specifically as follows:

[0030] Point A coordinates (x A , yA):

[0031] x A =x A0 cosθ-y A0 sinθ

[0032] y A =x A0 sinθ+y A0 cosθ

[0033] Where: (x A0 ,y A0 ) is A when θ=0° 0 Point coordinate value, lifting weight center of mass point G coordinate (xG ,y G ):

[0034] x 0 =x G0 cosθ-y G0 sinθ

[0035] y 0 =x G0 sinθ+y G0 cosθ

[0036] Where: (x G0 ,y G0 ) is G when θ=0° 0 Point coordinates;

[0037] Find the coordinates of point B (x E ,y E ), given: AB = c, DB = d, (x A ,y A ) and (x D ,y D ), so the coordinates of point B (x E ,y E ) can be solved from the following system of simultaneous equations, namely:

[0038] (x B -x D ) 2 +(y B -y D ) 2 =d 2

[0039] (x B -x A ) 2 +(y B -y A ) 2 =c 2

[0040] Find the coordinates of point B (x C ,y C ): Given: BC = a, AC = b, (x A ,y A ) and (x E ,y E ), so the coordinates of point C (x C ,y C ) is also solved in the following system of simultaneous equations, namely:

[0041] (x C -x B ) 2+(y C -y B ) 2 =a 2

[0042] (x C -x A ) 2 +(y C -y A ) 2 =b 2

[0043] Find the coordinate formula of the intersection point F of BD and CE (x F ,y F ), it is known that (x E ,y E ) and (x D ,y D ), then the equation of the line BD is:

[0044]

[0045] Given (xC, yC) and (x E ,y E ), then the equation of the straight line CE is:

[0046]

[0047] Solve the two equations together,

[0048] (y B -y D )x-(x B -x D )y+y(x B -x D )-x(y B -y D )=0

[0049] (y C -y E )x-(x C -x E )y+y(x C -x E )-x(y C -y E )=0

[0050] The coordinates of the intersection point F (x F ,y F ).

[0051] Furthermore, step 5.2 is as follows: Calculate the tipping force R:

[0052] Take the carriage as a separate body and take the moment about the flip center O: ∑M o =0

[0053]

[0054] Where x A The horizontal coordinate of point A, Y A Refers to the vertical coordinate of point A, ON 1 is the coordinate origin O to N 1 distance.

[0055] Furthermore, step 5.3 is as follows: Calculate the cylinder thrust F: Take the triangular arm ABC as a separate body, and take the moment of point B: ΣM E =0

[0056]

[0057] In the formula, take the triangular arm ABC as the separated body, take the moment of point B, and get point N 2、 N 3， X A The horizontal coordinate of point A, Y A Refers to the ordinate of point A, BN 2 From point B to N 2 The distance, BN 3 From point B to N 3 distance.

[0058] Furthermore, step 5.4 is as follows: Calculate the rod tension F 1

[0059] Due to the tension force F 1 The three intersecting forces F, the cylinder thrust F, and the tipping force R are balanced, and the cylinder thrust F and the tipping force R are both known, so the pull rod tension F 1 It can be solved;

[0060] Take the triangular arm ABC as the separated body and take the moment of point C: ΣM C =0

[0061]

[0062] In the formula, the triangular arm A 0 B 0 C 0 For separation, 0 Take the moment of the point and get point N 4 、N 5 , where CN 4 From point C to N 4 Distance, CN 5 From point C to N 5 distance.

[0063] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: A new type of lifting mechanism is designed based on the traditional Mallery lifting mechanism. Compared with the traditional Mallery lifting mechanism, the improved lifting mechanism can shorten the initial length of the hydraulic cylinder without increasing the lifting force coefficient, and the installation space required by the mechanism is small. A multi-objective optimization mathematical model of the improved lifting mechanism is established based on the mechanism motion and force analysis to realize the real motion of the mechanism, eliminate the possible problems in the design in the bud, and shorten the development cycle of product design. By using the drawing method and the analytical method to design the Mallery lifting mechanism, and then using Pro / E to perform the motion simulation analysis of the mechanism, no complicated mathematical modeling and computer language programming are required, but based on the solid model, the design and motion analysis are integrated, and the actual assembly, interference detection and motion coordination verification of the mechanism are simulated on the computer in the most economical and intuitive way. The application of Pro / E software mechanism to simulate the mechanism motion can realize kinematic and dynamic analysis and assembly interference, and verification of motion coordination, through the specific practice of the motion simulation of the Mallery lifting mechanism. It not only reveals the characteristics, methods, objects and main application scope of motion simulation, but also demonstrates the guiding role of simulation motion analysis on mechanism design and special simulation measurement analysis. It has creative and important significance for obtaining comprehensive data on the relationship between the mechanism's motion position, speed and kinematic pairs, so that designers can modify model parameters directly on the computer in a targeted manner and quickly achieve the purpose of mechanism optimization. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a hydraulic cylinder direct push lifting mechanism;

[0065] Figure 2 It is a hydraulic cylinder forward push connecting rod amplification type (Mallery type) lifting mechanism;

[0066] Figure 3 It is a balanced lifting mechanism with a cylinder pushing forward and a lever;

[0067] Figure 4 It is a hydraulic cylinder push-back connecting rod amplification type (Garwood type) lifting mechanism;

[0068] Figure 5 This is a simplified diagram of the improved Mallery lifting mechanism;

[0069] Figure 6 This is the force analysis diagram of the Mallery lifting mechanism;

[0070] Figure 7 It is the analytical diagram of the motion and force of the Mallery lifting mechanism;

[0071] Figure 8 is the measurement result;

[0072] Fig. 9The dynamic curve of the object measured for the first time;

[0073] Fig.10 The dynamic curve 1 of the second measurement object;

[0074] Fig.11 Dynamic curve 2 for the second measurement object;

[0075] Fig.12 The required hydraulic oil thrust for the front and rear; 1 is the filter; 2 is the battery; 3 is the chassis; 4 is the lifting device; 5 is the cargo box.

[0076] Fig.13 It is a compound lifting mechanism;

[0077] Fig.14 It is a flow chart of the present invention;

[0078] Fig.15 is the input signal and actual displacement curve;

[0079] Fig.16 Enter the error value before improvement;

[0080] Fig.17 Enter the error value for the improvement. DETAILED DESCRIPTION

[0081] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0082] Improved and based on

[0083] Dump trucks currently widely use hydraulic lifting mechanisms. According to the connection method between the cylinder and the car floor, the commonly used lifting mechanisms can be divided into two categories: direct push type and connecting rod combination type.

[0084] 1) Direct push lifting mechanism

[0085] The lifting mechanism in which the oil tank directly acts on the floor of the carriage is called a direct push lifting mechanism, or direct push lifting mechanism for short. According to the position of the lifting point under the floor of the carriage, this type of lifting mechanism can be divided into two types: the middle cylinder and the front cylinder.

[0086] The former has a cylinder supported in the middle of the car body, with a smaller cylinder stroke and a larger lifting force. Double-cylinder double-column cylinders are often used. The latter has a cylinder supported in the front of the car body, with a smaller lifting force and a larger cylinder stroke. It is generally used on heavy-duty dump trucks, and the cylinder usually uses a multi-stage telescopic cylinder.

[0087] 2) Connecting rod combined lifting mechanism

[0088] The oil cylinder and the car floor are connected by a connecting rod mechanism. This lifting structure is called a connecting rod combined lifting mechanism. Production practice shows that the connecting rod combined lifting mechanism has great advantages. In the past decade, this type of lifting mechanism has developed rapidly and has appeared in various forms.

[0089] According to the installation characteristics of the oil cylinder, the connecting rod combination lifting mechanism can be divided into various structural forms such as oil cylinder forward push (backward push) connecting rod amplification type, oil cylinder forward push (backward push) lever balance type, oil cylinder floating, etc. Figure 1 , 2 , 3, and 4. The key to the inspection is whether the hydraulic system can withstand the lifting force under the action of the lifting mass, whether the stroke of the hydraulic system can meet the maximum lifting angle of the car body, and the production and matching of the hydraulic system, especially the hydraulic cylinder.

[0090] Comparing the two, the latter has a simpler structural layout, a larger system, and a higher construction height. The advantages of the oil cylinder processing technology are single-stage cylinder and low processing precision, but good processing technology, better oil pressure characteristics, system sealing, fewer sealing links, less leakage, and longer service life. In summary, the present invention selects the oil cylinder forward push connecting rod combination mechanism (Mallery type lifting mechanism) with stable lifting performance, good hydraulic performance, and high reliability as the research object of the present invention.

[0091] First, in view of the shortcomings of the Mallery lifting mechanism, the lifting hydraulic cylinder provides power, and the carrier is lifted through the joint action of the triangular arm and the pull rod. The Mallery lifting mechanism currently used has a long initial length of the lifting cylinder, which cannot meet the needs of actual production and vehicle layout. To solve this problem, an improved Mallery lifting mechanism is proposed, which can reduce the initial length of the hydraulic cylinder without increasing the lifting force coefficient. Figure 5 As shown, it consists of triangular arm ABC, lifting hydraulic cylinder BE, and tie rod AD. The triangular arm ABC is different from the traditional Mallery lifting mechanism in that the hinge point B between the hydraulic cylinder and the triangular arm is below the AC side of the triangular arm. This lifting mechanism can shorten the installation length of the lifting hydraulic cylinder and reduce the installation space, thus broadening the scope of the lifting mechanism design.

[0092] The first step is to determine the maximum lifting angle. The maximum lifting angle of the carriage refers to the angle between the bottom of the cargo box and the plane of the frame when the cargo box is lifted to the design limit position. It depends on the size of the static repose angle of the commonly transported goods. Therefore, the basis for determining the maximum lifting angle of the carriage is the static repose angle of the commonly transported goods, that is, the designed maximum lifting angle of the carriage θ max It must be greater than the static repose angle of the cargo to ensure that the cargo in the cargo box is completely unloaded. In addition, when the car is lifted to the maximum lifting angle θ maxWhen the rear tailgate of the carriage hangs down to the lowest point, it must maintain a certain distance H from the ground, as shown in Table 1.

[0093] Table 1

[0094]

[0095] In order to avoid the motion interference between the car body and the rear end of the chassis longitudinal beam when dumping, ΔL must be greater than zero. When designing, the maximum lifting angle of the dump truck car body can generally be selected between 50° and 60°. The maximum lifting angle of the heavy-duty dustpan-type dump truck car body is generally 60° to 75°. This design selects a city domestic garbage dump truck. According to statistics, the average density of urban garbage is 488.85 kg / m 3 , here the maximum lifting angle is 50°. Referring to similar models, ΔL = 250㎜, the distance between the front tailgate of the car and the rear wall of the cab is C = 150㎜, and considering the front and rear overhang dimensions of the chassis, the front overhang is 1330㎜, and the rear overhang is 1200㎜. The graphical method can be used to verify that when the car is lifted to the maximum angle, the distance H between the rear tailgate of the car and the ground is greater than zero.

[0096] First, use the graphical method to determine the coordinates of each hinge point and the cylinder stroke L as the preliminary design parameters. Figure 6 This is the force analysis diagram of the Mallery lifting mechanism. Then, the function relationship between the coordinates and the lifting angle is accurately calculated by analytical method, so as to obtain the tipping force R, cylinder thrust F, and rod force F. 1 wait.

[0097] 1) Initially determine the original parameters

[0098] The original parameters include: factory-set maximum total mass m α 、Loading mass m θ , total lifting mass m ω , Maximum lift angle θ max etc., lifting mass m ω = load mass + car mass, m ω The initial size is set at 4000 kg.

[0099] Initially determine the lengths of the three sides of the triangle arm, a, bc, and the length of the tie rod, d. When determining, we must consider the amplification effect of the triangle arm on the motion and properly control the piston stroke. For this reason, the general ratio of the three sides is approximately:

[0100] a:b:c=1.5:3:4

[0101] Therefore, the initial parameters of the triangular arm are: a = 340 mm, b = 680 mm, c = 900 mm. The length of the pull rod is 1924 mm.

[0102] 2) Establish coordinate system XOY

[0103] The cargo box flip center O1 is usually selected near the top of the rear suspension rear support point. 1 The projection O in the lower plane of the subframe is taken as the origin of the coordinate system. The X-axis is along the lower plane of the subframe and points to the forward direction of the vehicle.

[0104] 3) Determine the coordinates of the fulcrum A where the triangular arm is connected to the cargo box (x A ,y A )

[0105] Select x A The main consideration is to arrange the space of the triangle arm appropriately to avoid possible motion interference between the front end B of the triangle arm and the transmission and power take-off assembly. Under this premise, choose as large a x as possible. A value to increase the lift arm ON. Select y A The maximum value allowed by the structure, as long as it does not interfere with the bottom of the cargo box. The initial coordinates of point A are (2800, 250)

[0106] 4) Determine the coordinates (x E ,y E )、(x D ,y D ) The coordinates of points E and D determine the cylinder force F and the rod force F 1 The principle of determination is to keep the distance between the two points as far as possible under the premise that the hinge support installation structure allows. In this way, the (α+β) angle can be reduced as much as possible, so that F and F 1 A larger resultant force R is formed. The initial coordinates of points D and E are: (1700, 100) and (2000, -124)

[0107] 5) Determine the cylinder stroke L

[0108] The cylinder stroke is the difference between the maximum lifting position and the total length of the cylinder actually extended at the original position. To this end, the highest lifting position of the triangular arm needs to be drawn using a graphical method. The steps are as follows: 1 A rotates around the center O 1 Turn 50° to OA 1 . 1 D is the center of the circle and c is the radius. D is the center of the circle and BD is the radius. I Arc, two arcs intersect B 1 Point. 1 , B 1 With a as the center and a and b as the radius, we can get the intersection point C. 1 ΔA l B 1 C 1 This is the highest lifting position of the triangular arm. Connect EC 1, that is, the maximum extension length of the cylinder piston rod is L = EC 1 -EC.

[0109] Combined with the drawing method, the coordinate parameters of each hinge point of the lifting mechanism can be easily determined by using the trajectory method of the triangular arm template on the drawing to meet the motion conditions. The coordinate values ​​of each hinge point in each direction are obtained from the drawing method, and then the geometric dimensions of the pull rod and the triangular arm are obtained. This is used as the known conditions for the second stage design to perform analytical calculations when the lifting angle θ is between 0° and the maximum lifting angle θ max The maximum cylinder thrust and maximum rod pull force change between .

[0110] Finally, the analytical calculation of the movement and force of the Mallery lifting mechanism is carried out. Figure 7 The following is the analysis diagram of the movement and force of the Mallery lifting mechanism. The analysis steps are as follows: Find the coordinates of the hinge point A between the triangular arm and the car body and the coordinates of the center of mass of the lifting weight point G when the lifting angle is θ. The coordinates of point A (x A , yA):

[0111] x A =x A0 cosθ-y A0 sinθ

[0112] y A =x A0 sinθ+y A0 cosθ

[0113] Where: (x A0 ,y A0 ) is A when θ=0° 0 Point coordinate value. The coordinate of the lifting weight center of mass point G (x G ,y G ):

[0114] x 0 =x G0 cosθ-y G0 sinθ

[0115] y 0 =x G0 sinθ+y G0 cosθ

[0116] Where: (x G0 ,y G0 ) is G when θ=0° 0 Point coordinate value, G 0 The coordinates are (1800, 604).

[0117] 1. Find the coordinates of point B (x E ,y E), given: AB = c, DB = d, (x A ,y A ) and (x D ,y D ), so the coordinates of point B (x E ,y E ) can be solved from the following system of simultaneous equations. That is:

[0118] (x B -x D ) 2 +(y B -y D ) 2 =d 2

[0119] (x B -x A ) 2 +(y B -y A ) 2 =c 2

[0120] 2. Find the coordinates of point B (xC, yC) when the lift angle is θ

[0121] Given: BC = a, AC = b, (x A ,yA) and (x E , yE), so the coordinates of point C (xC, yC) can also be solved from the following system of simultaneous equations, namely:

[0122] (x C -x B ) 2 +(y C -y B ) 2 =a 2

[0123] (x C -x A ) 2 +(y C -y A ) 2 =b 2

[0124] 3. Find the coordinate formula of the intersection point F of BD and CE (x F ,y F ), it is known that (x E ,y E ) and (x D ,y D ), then the equation of the line BD is:

[0125]

[0126] Known (x C ,y C ) and (x E ,y E ), then the equation of the straight line CE is:

[0127]

[0128] Solve the two equations together,

[0129] (y B -y D )x-(x B -x D )y+y(x B -x D )-x(y B -y D )=0

[0130] (y C -y E )x-(x C -x E )y+y(x C -x E )-x(y C -y E )=0

[0131] The coordinates of the intersection point F (x F ,y F ).

[0132] 4. Calculate the tipping force R

[0133] Take the carriage as a separate body and take the moment about the flip center O: ∑M o =0

[0134]

[0135] 5. Calculate the cylinder thrust F

[0136] Take the triangular arm ABC as the separated body and take the moment of point B: ∑M E =0

[0137]

[0138] 6. Calculate the tension F of the pull rod 1

[0139] Due to the tension force F 1 The three intersecting forces F, the cylinder thrust F, and the tipping force R are balanced, and the cylinder thrust F and the tipping force R are both known, so the pull rod tension F 1 It can be solved.

[0140] Take the triangular arm ABC as the separated body and take the moment of point C: ∑M C =0

[0141]

[0142]

[0143] Take the above formula as the known conditions and substitute it into the force calculation formula of the cylinder and the tie rod when solving any lifting angle θ. max When the change between max and the maximum tie rod tension F 1max . And use this as the load basis for the hydraulic system and the tie rod strength check. If the calculation results cannot meet the design requirements, the parameters given by the drawing method should be adjusted and recalculated until a satisfactory result is obtained.

[0144] In practical applications, due to the maximum lifting force F max Maximum tension F of the pull rod 1max Both appear at the initial position of θ = 0°, so in the overall design, it is generally used as the encircling method to solve the maximum stroke of the cylinder, and the analytical method is used to calculate the maximum cylinder thrust F max and the maximum tension of the tie rod F 1max , and use the two methods in combination.

[0145] According to the above design calculation principle, the calculation formula is converted into C++ program code and compiled into executable software. The initial parameters of the mechanism calculation are input into the program interface, and the computer can provide real-time calculation results between 0° and θ max The coordinates and forces of each point at any angle between the two. If the initial force calculation parameters entered in the program interface are inappropriate, causing the triangular arm to interfere with the carriage or other mechanisms during the lifting process, the program will pop up a warning "error". The initial parameters need to be re-entered. The maximum thrust F of the cylinder is calculated max =97217.7N. Maximum stroke of the cylinder L max =843.21㎜.

[0146] Building the Model

[0147] The composite lifting mechanism comprises a cargo box, a vehicle frame and a lifting mechanism, wherein one end of the vehicle frame is connected to the rear end of the cargo box by a pin shaft, the lifting mechanism is installed in the middle of the vehicle frame, the top of the lifting mechanism is connected to the bottom of the cargo box by a pin shaft, and the bottom of the lifting mechanism is connected between the vehicle frames through a lower support assembly of an oil cylinder. The lifting mechanism comprises an oil cylinder, an oil tank for supplying oil to the oil cylinder, a triangular arm, a connecting shaft and a connecting rod, the bottom of the oil cylinder is rotatably connected to the lower support assembly of the oil cylinder, the connecting rod is arranged on both sides of the oil cylinder, the bottom of the connecting rod is connected to the lower support assembly of the oil cylinder by a pin shaft, the top of the connecting rod is connected to one end of the triangular arm by a pin shaft, the other end of the triangular arm is connected to the bottom of the cargo box by a pin shaft, the connecting shaft is arranged in the middle of the triangular arm and the two ends of the connecting shaft are rotatably connected to the triangular arm, and the top of the oil cylinder is fixedly connected to the connecting shaft.

[0148] Then use the existing data to build the corresponding model in Solidworks and import it into Pro / E.

[0149] Simulation Analysis

[0150] When performing motion simulation and analysis on the lifting mechanism, click the drop-down menu Mechanism → Mass Properties to set the mass properties of each entity in the mechanism. The main contents include: density, volume, mass, center of gravity and moment of inertia. Apply load and click the drop-down menu Mechanism → Gravity. The value and direction of gravity acceleration can be set. When motion analysis is necessary, damping elements can be set between each connecting axis and the friction surface of the two main bodies to establish the corresponding motion damping force. By clicking the drop-down menu Mechanism → Force / Torque → New, the external environment of the mechanism movement can be simulated. Its types are divided into "point force" and "main torque", that is, force and torque, like other vectors, also need to indicate "mode" and "direction". The function expression of the mode is divided into: constant - the magnitude of the force / torque is a constant; table - a series of query points are established in a table to fit the mode of the force / torque, with two options of "linear" and "spline fitting"; user defined - define the mode with a function expression to create external forces and external torques. Through various dynamic analyses of the mechanism, relevant information can be quickly obtained to improve the structural design. For the same mechanism model, by applying different elements, partially locking the mechanism or changing the constraints, various working conditions of the mechanism can be studied and analyzed. Click the menu Mechanism→Analyses command, the Analyses dialog box pops up, click "New", and then the Ana-lyses definition dialog box pops up. At this time, select different analysis types, and dialog boxes with different contents will be displayed. The analysis types of the mechanism are: kinematic analysis, dynamic analysis, static analysis, force balance analysis, and repeatable assembly analysis. For kinematic analysis of mechanisms that do not involve force, mass, and inertia, kinematic analysis and repeatable assembly analysis types can be used. In this example, dynamic analysis is selected, and a name is entered in the "Name" column or the system default is accepted. In the "Type" column, dynamic analysis is selected. In the "Motor" tab: Add the required motors as needed and set the start and end times for them. It should be noted that the start and end times cannot be specified for the servo motor in the dynamic analysis type, but only from start to end. Return the measurement result set. Click "Analysis Definition Name" in the result set, and the value of the measurement analysis will be displayed after the name of the measurement option. Click "Measurement Name" again, and the "Measurement" button in the upper left corner will return to normal from gray. Figure 8 Click the "Measure" button, and the "Graphics Tools" box will pop up, showing the dynamic curve of the specific measurement object, such as Fig. 9 or Fig.10As shown. In the "External Load" tab: specify the required external load for the mechanism, and switch the "Enable gravity, Enable all friction" option. The main simulation analysis objects of this lifting mechanism design are: the displacement, velocity and acceleration between the triangular arm assembly and the vehicle box floor hinge seat, the front end pin hole of the pull rod, and the coupling pin. Through simulation analysis and measurement, the precise parameters of the mechanism's motion process are understood. Compared with the original lifting mechanism, the improved optimized lifting mechanism and the transmission device angle gradually increase with the lifting process, so it has good lifting performance. The change in hydraulic oil pressure required in the mechanism of the car transporter using optimized lifting is shown below Fig.12 shown.

[0151] Simulation results display and analysis

[0152] The results of the analysis can be presented in a visual way, mainly including motion playback, analyzable interference inspection, motion envelope, etc. The results of motion simulation can be made into animations, or in the measurement system, the trend of the parameters that need to be tracked can be intuitively presented in the form of charts. If the results are not ideal, the model parameters can be directly modified in the design mode and the simulation analysis can be repeated to achieve the purpose of mechanism optimization. The new lifting mechanism has the advantage of a shorter initial length of the hydraulic cylinder, which can be used in mechanisms with smaller installation spaces, broadening the scope of the design of the lifting mechanism.

[0153] The application of pro / E software mechanism (Mechanism) to the mechanism motion simulation can realize the kinematic and dynamic analysis and the verification of assembly interference and motion coordination. Through the specific practice of the Mallery lifting mechanism motion simulation, it not only reveals the characteristics, methods, objects and main application scope of motion simulation, but also demonstrates the guiding role of simulation motion analysis in mechanism design. In particular, simulation measurement analysis has creative and important significance for obtaining comprehensive data on the relationship between the mechanism motion position, speed and kinematic pairs, so that designers can modify the model parameters directly on the computer in a targeted manner and quickly achieve the purpose of mechanism optimization.

Claims

1. An improved Mallery lifting mechanism assembly design method for a load-carrying dump truck, characterized in that: The steps include: Step 1: Improve the Mallery lifting mechanism, including a triangular arm, a lifting hydraulic cylinder and a pull rod; Step 2: Determine preliminary design parameters; Step 3: Establish a coordinate system, determine the coordinates of the fulcrum connecting the triangular arm and the cargo box, and determine the coordinates of the fixed hinge fulcrum of the oil cylinder and the fixed hinge fulcrum of the pull rod; Step 4: Determine the cylinder stroke; Step 5: Calculate the movement and force of the Mallery lifting mechanism and find the maximum cylinder thrust F max and the maximum tie rod tension F 1max , and use this as the load basis for the hydraulic system and tie rod strength verification respectively.

2. The assembly design method of an improved Mallery lifting mechanism on a load-carrying dump truck according to claim 1 is characterized in that: Step 1 specifically includes: improving the Mallery lifting mechanism, including a triangular arm, a lifting hydraulic cylinder and a pull rod, wherein the hinge point between the lifting hydraulic cylinder and the triangular arm is below the top edge of the triangular arm.

3. The assembly design method of an improved Mallery lifting mechanism on a load-carrying dump truck according to claim 1 is characterized in that: Step 2 is specifically as follows: the preliminary design parameters include the factory-determined maximum total mass m α 、Loading mass m θ , total lifting mass m ω , Maximum lift angle θ max , where the lifting mass m ω = load mass + car mass; initially determine the lengths of the three sides of the triangular arm a, b, c and the length of the pull rod d, and the proportional relationship of the three sides is: a:b:c=1.5:3:

4.

4. The assembly design method of an improved Mallery lifting mechanism on a load-carrying dump truck according to claim 1 is characterized in that: Step 3 specifically includes the following steps: Step 3.1, select the cargo box flip center O1 near the upper part of the rear support point of the rear suspension, take the projection O of the center O1 in the lower plane of the sub-beam as the origin of the coordinate system, and the X-axis is along the lower plane of the sub-beam and points to the forward direction of the vehicle; Step 3.2, determine the coordinates of the fulcrum A where the triangular arm is connected to the cargo box (x A ,y A ): Select x A Considering the layout space of the triangular arm, select a larger x A value to increase the lifting arm ON, select y A This is the maximum value allowed by the structure, as long as it does not interfere with the bottom of the cargo box; Step 3.3, determine the coordinates of the cylinder fixed hinge point E and the tie rod fixed hinge point D (x E ,y E )、(x D ,y D ) The coordinates of points E and D determine the positions of the lines of action of the cylinder force F and the pull rod force F1. Under the premise that the hinge mounting structure allows, the distance between the two points is increased to reduce the angle (α+β) so that F and F1 form a larger resultant force R.

5. The assembly design method of an improved Mallery lifting mechanism on a load-carrying dump truck according to claim 1 is characterized in that: Step 4 is as follows: the cylinder stroke is the difference between the actual total length of the cylinder at the highest lifting position and the original position; use the drawing method to draw the highest lifting position of the triangular arm; the steps are as follows: rotate O1A 50° around the rotation center O1 to OA1, draw an arc with A1 as the center and c as the radius, and draw B with D as the center and BD as the radius. I The two arcs intersect at point B1. With A1 and B1 as the center and a and b as the radius, arcs are drawn to get the intersection point C1. ΔA1B1C1 is the highest lifting position of the triangular arm. Connect EC1, that is, the maximum extension length of the cylinder piston rod is L = EC1-EC. The coordinate values ​​of each hinge point in each direction are obtained from the drawing method, and then the geometric dimensions of the pull rod and the triangular arm are obtained. The analytical calculation is performed when the lifting angle θ is 0° and the maximum lifting angle θ max The maximum cylinder thrust and maximum rod pull force change between .

6. The assembly design method of the improved Mallery lifting mechanism on a load-carrying dump truck according to claim 1 is characterized in that: Step 5 is as follows: Step 5.1, calculate the coordinates of the hinge point A between the triangular arm and the carriage and the coordinates of the center of mass of the lifting weight point G when the lifting angle is θ; Step 5.2, calculate the tipping force R; Step 5.3, calculate the cylinder thrust F; Step 5.4, calculate the tension F1 of the pull rod; Step 5.5, solve the force calculation formula of the cylinder and the tie rod at any lifting angle θ. When the lifting angle θ is between 0° and the maximum θ max When the change between max and the maximum tie rod tension F 1max , and use this as the load basis for the strength verification of the hydraulic system and the tie rod respectively.

7. The assembly design method of the improved Mallery lifting mechanism on a load-carrying dump truck according to claim 6 is characterized in that: Step 5.1 is as follows: Point A coordinates (x A ,y A ): x A =x A0 cosθ-y A0 sinθ y A =x A0 sinθ+y A0 cosθ Where: (x A0 ,y A0 ) is the coordinate value of point A0 when θ=0°, and the coordinate of point G, the center of mass of the lifting weight (x G ,y G ): x0=x G0 cosθ-y G0 sinθ y0=x G0 sinθ+y G0 cosθ Where: (x G0 ,y G0 ) is the coordinate value of point G0 when θ=0°; Find the coordinates of point B (x E ,y E ), given: AB = c, DB = d, (x A ,y A ) and (x D ,y D ), so the coordinates of point B (x E ,y E ) is solved from the following system of simultaneous equations, namely: (x B -x D ) 2 +(y B -y D ) 2 =d 2 (x B -x A ) 2 +(and B -and A ) 2 =c 2 Find the coordinates of point B (x C ,y C ): Given: BC = a, AC = b, (x A ,y A ) and (x E ,y E ), so the coordinates of point C (x C ,y C ) is also solved in the following system of simultaneous equations, namely: (x C -x B ) 2 +(and C -and B ) 2 =a 2 (x C -x A ) 2 +(y C -y A ) 2 =b 2 Find the coordinate formula of the intersection point F of BD and CE (x F ,y F ), it is known that (x E ,y E ) and (x D ,y D ), then the equation of the line BD is: Known (x C ,y C ) and (x E ,y E ), then the equation of the straight line CE is: Solve the two equations together, (and B -and D )x-(x B -x D )y+y(x B -x D )-x(y B -and D )=0 (and C -and E )x-(x C -x E )y+y(x C -x E )-x(y C -and E )=0 The coordinates of the intersection point F (x F ,y F ).

8. The assembly design method of the improved Mallery lifting mechanism on a load-carrying dump truck according to claim 6 is characterized in that: Step 5.2 is as follows: Calculate the tipping force R: Take the carriage as a separate body and take the moment about the flip center O: ∑M O =0 Where, X A The horizontal coordinate of point A, Y A Refers to the vertical coordinate of point A, ON1 is the distance from the coordinate origin O to N1.

9. The assembly design method of the improved Mallery lifting mechanism on a load-carrying dump truck according to claim 6 is characterized in that: Step 5.3 is as follows: To calculate the cylinder thrust F: Take the triangular arm ABC as a separate body, and take the moment of point B: ∑M E =0 In the formula, take the triangular arm ABC as the separated body, take the moment of point B, and get point N 2、 N 3， X A The horizontal coordinate of point A, Y A BN2 is the distance from point B to N2, and BN3 is the distance from point B to N3.

10. The assembly design method of the improved Mallery lifting mechanism on a load-carrying dump truck according to claim 6, characterized in that: Step 5.4 is as follows: Calculate the pull rod force F1 Since the three intersecting forces of the tie rod force F1, the cylinder thrust F and the overturning force R are balanced, and the cylinder thrust F and the overturning force R are both known, the tie rod force F1 can be solved; Take the triangular arm ABC as the separated body and take the moment of point C: ΣM C =0 In the formula, the triangular arm A0B0C0 is a separated body, and the moment of point B0 is taken to obtain points N4 and N5, where CN4 is the distance from point C to N4, and CN5 is the distance from point C to N5.

Images