Most match oil engine cylinder block cylinder line

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Diesel engine cylinder block cylinder liner hole stop hole finishing modular machine tool

Abstract: our B4125 (and b4130) four cylinder diesel engine cylinder block has high requirements for cylinder liner hole dimensional accuracy, roughness, stop hole depth and position, so we must be firm, especially the stop hole depth tolerance is difficult to control. At present, the introduction of foreign equipment is often used to solve this problem. The successful development of this machine tool provides a reliable technical guarantee for the processing of B4125 (b4130) diesel engine cylinder block of our company

key words: cylinder liner hole; Lip hole; Finishing eccentric mechanism; Machining contents and accuracy requirements of modular machine tool

1 workpiece

1.1 machining contents

b4125 diesel engine cylinder block assembly (b4125.02.021) 4 cylinder liner mounting holes and the depth of 4 cylinder liner upper end stop holes

step 1: semi finish boring 2 and 4 (1 and 3) cylinder holes to size

step 2: finish turning 2 and 4 (1 and 3) cylinder lip to depth 06

step 3: fine boring 2- φ 144+0.040,2- φ 141+0.040

machining 1 and 3 cylinder holes after workpiece shift

positioning datum is process hole 2- φ 26+0.0250

1.2 machining dimensions and accuracy (see Figure 1)

Figure 1 workpiece process diagram

main technical requirements

1 φ 144+0.040 pairs φ 141+0.040 coaxiality less than φ 0.03

2. The perpendicularity of a-C center line to surface B is less than φ 0.05

3. φ The coaxiality of 152+0.160 to a center is less than φ 0.1

4. seam surface φ. 05 the total runout of a-C center is less than φ 0.05

2 technical scheme analysis

2.1 machine tool scheme

according to the characteristics of the workpiece, the machine tool adopts vertical two-axis two station, as shown in Figure 2. Two single shaft eccentric boring heads, one vertical three guide rail hydraulic precision slide, one displacement precision workbench, one set of open fixture, one set of PC controlled variable frequency speed regulation electrical system and one set of separate hydraulic station drive hydraulic system are configured. In the automatic working cycle (see Figure 3), two cylinder liner holes and stop holes are machined at one time by two tool bars. First, feed downward from the upper end to semi finish machining. Use the positioning block on the boring head to directly position with the top surface of the cylinder block, so as to ensure that the tolerance from the end surface of the stop hole to the top surface of the cylinder block is 0.05mm. At the same time, in order not to apply the feed force of the sliding table to the workpiece during positioning, a buffer floating mechanism is set on the boring head. After positioning, the eccentric mechanism of the boring head acts to make a group of semi finishing tools exit the cutting position. At the same time, the finishing edge cutting tools feed laterally. The finishing boring cutter turns to the finishing position of the cylinder hole, and then the boring head returns upward. The finishing tools finish the cylinder bore. After the first two cylinder liner holes are machined, shift the workbench to move the hole distance of one cylinder, repeat the above contents, and complete the machining of the other two cylinder liner holes, stop holes and end faces. The machine tool slide is a vertical three guide rail slide. The slide seat is integrated with the column, the middle guide rail is guided, and the guide rails on both sides are limited, which greatly improves the strength and rigidity of the slide. In addition, a compressed air nozzle is set at the positioning position between the boring head positioning block and the workpiece to purge the positioning position before positioning to ensure accurate positioning. All machine tools adopt machine clamping knives

Fig. 2 machine tool diagram

Fig. 3 machine tool work cycle diagram

before determining the above machine tool scheme, we also considered that the tool feeding mechanism uses the inclined push-pull tool block for horizontal cutting. After comparison, we believe that the eccentric mechanism has many advantages. The tool body and the tool bar are rigidly connected without relative movement, and will not be stuck by iron chips or mechanism. The positioning accuracy of the tool is very high. For example, after the eccentric mechanism is equipped with a numerical control system, it can process multiple (more than two) holes and chamfers with different diameters at one time by controlling the eccentric angle and tool distribution

2.2 table of cutting parameters and cutting parameters of spindle for tool auxiliary tool design (motor speed adjustable)

- cutting amount of upper cylinder hole and lower cylinder hole stop semi fine boring fine boring semi fine boring fine boring semi fine boring fine cutting speed v

m/min80 ~ 90100 ~ 11380 ~ 90100 ~ 11380 ~ 90100 ~ 113 spindle speed n

r/min170 ~ 190210 ~ 245170 ~ 190210 ~ 245170 ~ 190210 ~ 245 vertical sliding table per

minute feed mm- boring per revolution

feed mm0.26 ~ 0.290.11 ~ 0.130.26 ~ 0.290.11 ~ 0.130.26 ~ 0.29-

when the tool advances from top to bottom During feeding, three boring cutters D, e and f perform semi fine boring (see Figure 4). When the boring cutter f reaches the depth position of the stop hole, the eccentric mechanism acts, and the boring cutter a boring the stop end face. At the same time, the semi fine boring cutter retreats. The fine boring cutters a, B and C feed to the fine boring hole size, and the cutters feed from bottom to top for fine boring. See the table for cutting parameters. The cutting speed V adopts variable frequency speed regulation and can be adjusted within a certain range. The feed rate is controlled by the hydraulic system and the speed regulating valve

Figure 4 Schematic diagram of boring process

2.3 fixture scheme

the perpendicularity of the centerline of the cylinder liner hole of the workpiece to the common center of the crankshaft bearing hole is required to be 0.08mm. If the positioning method of crankshaft bearing hole positioning, bottom leveling and auxiliary support is adopted, the design datum of the workpiece coincides with the fixture positioning datum, which can better ensure the positional requirements of the cylinder liner hole of the part, but the fixture structure is complex, The clearance between the crankshaft bearing hole and the positioning mandrel must also be eliminated with an expandable mandrel. In addition, there are high requirements for leveling, auxiliary support and clamping mechanism. Considering that the crankshaft bearing hole is accurately bored by positioning the bottom surface and two pin holes, which can ensure that the center line of the crankshaft bearing hole is 0.04mm parallel to the bottom surface, the machine tool adopts bottom surface and two pin positioning to ensure that the center line of the cylinder liner hole is 0.04mm vertical to the bottom surface, which can meet the verticality requirements. At this time, the fixture is positioned with one side and two pins, which makes the structure simple, the workpiece loading and unloading convenient, and greatly reduces the complexity of the electrical and hydraulic systems of the machine tool. Therefore, the fixture of the machine tool adopts the form of clamping with one side and two pins on the top surface

3 eccentric boring head design

boring head is the key component of this machine tool. In the development, we have absorbed the advanced technology of the same type of boring head at home and abroad, combined with the processing requirements and characteristics of the B4125 cylinder block of our company, and adopted the boring head of single shaft eccentric mechanism. Through single head or multi shaft combination, we can complete the semi precision boring, precision boring, boring turning, chamfering and other multi process processing of cylinder liner holes of single cylinder and multi cylinder diesel engines

3.1 main structural features

(1) the center of the cutter bar shaft deviates from the rotation center of the spindle. The eccentricity is used to control the diameter and size of semi fine boring and fine boring and to bore the end surface of the stop hole. The boring and turning stop are in the same station, ensuring that the stop surface is perpendicular to the center line of the upper and lower cylinder holes

(2) when machining the stop, use the positioning block on the boring head to directly position with the top surface of the cylinder block, better control the depth from the stop end face to the top surface of the cylinder block, and set a positioning buffer (floating) device to avoid the over stroke interference of the machine tool slide during positioning

(3) the boring head is designed as a single shaft boring head, which is centrally driven by one gearbox and one motor, which is conducive to manufacturing, installation and adjustment. The front support of the main shaft adopts the structure of double row short cylindrical roller bearing and thrust ball bearing, which makes the radial and axial rigidity good and the precision high

(4) the rear support of the tool bar shaft adopts sliding bearing and the hydraulic plastic is used to tension the sliding sleeve to eliminate its clearance and improve the anti vibration ability of the tool bar

(5) the feed motion transmission mechanism of boring lathe end face and cylinder diameter adopts the clearance elimination structure to ensure the transmission accuracy

3.2 boring head action

as shown in Figure 5, the motor torque drives the pulley 2 through the toothed belt, and the pulley 2 drives the main shaft 5 through the flat key. At the same time, the pulley 2 drives the flange 8, the internal spline of the flange 8 drives the spline shaft 3, the large spiral angle spline at the front end of the spline shaft drives the spiral spline flange 4, and the spiral spline flange 4 drives the eccentric shaft 7 to rotate synchronously with the main shaft 5 through the key. When the positioning stopper 10 is positioned on the top surface of the cylinder block, the push rod 1 (pushed by the oil cylinder) drives the spline shaft 3 to move axially, and the helical spline at the front end of the shaft 3 drives the eccentric shaft 7 to rotate through the helical spline flange 4. Since the shaft 7 is installed in the eccentric hole of the main shaft 5, the rotation of the shaft 7 in the eccentric hole of the main shaft 5 will increase (decrease) the radial dimension of the tool, complete the boring of the end surface of the stop hole, and replace one group of tools with another group of tools to process holes with different diameters

Figure 5 boring head structure

1 Push rod 2 Pulley 3 Spline shaft 4 Spiral spline helps transform and upgrade the plastic industry flange 5 Spindle

6 Spring 7 Eccentric spindle 8 Internal spline flange 9 Front end cover 10 Positioning stopper

3.3 eccentric working principle

as shown in Figure 6, O is the rotation center of main shaft 5 (i.e. tool rotation center), O ′ and the difference between electronic universal testing machine and similar products is not only that the price advantage is eccentric shaft 7 rotation center, the distance between them is eccentric distance e, and the distance from tool tip d to eccentric shaft 7 rotation center O ′ is R (this value is a constant value in the processing process), The distance from the tool tip d to the rotation center O of the main shaft 5 is R (this value changes continuously with the rotation of the eccentric shaft 7 in the eccentric hole of the main shaft 5, so as to realize horizontal tool walking and tool changing). from Δ O ′ od cosine theorem,

when ∠ ro ′ o = 0 °, R min Rmin = r-e

when ∠ ro ′ o = 180 °, R Max has its own characteristics and practical conditions. Rmax = R + e

the maximum stroke is Lmax = Rmax Rmin = 2e

when turning with Rmin and Rmax as radius, the annular area between the two circles is the range that can be machined on the end face. At the beginning of the work feed, the radius from the tool tip to the spindle rotation center is P1, and at the end of the work feed is P2, then the eccentric shaft angle during the work feed is: φ=θ 2- θ 1。 Considering the characteristics of this machine tool, set θ 1=0°, θ 2=150°, θ The diameter at two places is the diameter of fine boring and the dwell diameter of turning end face cutter. θ 2 = 150 ° is not the maximum diameter. Therefore, when the tool is worn, the θ 2 to compensate the tool wear. θ 1 = 0 ° is semi finished diameter. It is not difficult to see from the figure that as long as the corner is controlled at θ 1 to θ 2, a series of diameter positions of the tool can appear, and multi diameter boring, chamfering, etc. can be realized

Figure 6 eccentric diagram

4 conclusion

at present, the machine tool has been manufactured, debugged and put into use, which can ensure the accuracy requirements of the workpiece. Foreign machine tools of the same type set the finish milling of the top surface of the cylinder block, the finish boring of the cylinder liner hole and the stop hole on the same machine tool, which can more effectively control the depth of the stop hole. Due to the large size of the cylinder block, the design of the machine tool is huge and complex. Therefore, we separate milling and boring. The machine tool is simpler than the former, but it improves the parallelism requirements of the top and bottom surfaces of the cylinder block milled in the previous process. The requirements can also be ensured after calculation. If the machine tool is equipped with a numerical control system, it can greatly improve the machining accuracy and automation, which will be subject to the transformation of the machine tool in the future. (end)

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