1. A kinematic pair consisting of two members in point or line contact is called a high pair.

2. The hinged four-bar mechanism that meets the conditions of crank existence is a crank rocker mechanism with the bar adjacent to the shortest bar as the frame and a double crank mechanism with the shortest bar as the frame.

3. In the cam mechanism, when the common motion law of the follower is uniform motion, rigid impact will occur.

4. When calculating the contact strength of spur gear, the contact stress at the pitch line is taken as the calculation basis, and the load is borne by the gear pair.

5. In order to make two pairs of spur gears mesh correctly, their modulus m and pressure angle must be equal respectively.

6. The bending stress of a pair of gears with different numbers of teeth is 6. Equal. The hardness of two wheels is different, so are their allowable bending stresses.

7. The main failure forms of V-belt drive are slipping and fatigue fracture.

8. When designing V-belt drive, choose the model of V-belt according to the calculated power Pc and the small wheel speed n 1.

9. The greater the pitch in the chain drive, the larger the size of each part in the chain, and the greater the movement unevenness of the chain drive.

10. When working, the shaft that only bears the bending moment but not the torque is called the spindle.

Second, multiple-choice questions (65438+ 0 points for each small question, a total of 5 points) Second, multiple-choice questions C B D B D

1. The undercutting phenomenon of involute standard gears occurs in.

A. When the modulus is large, B. When the modulus is small.

C. when the number of teeth is small, D. when the number of teeth is large

2. Among the following four kinds of rolling bearings, they must be used in pairs.

A. Deep groove ball bearings B. Tapered roller bearings

C. thrust ball bearings D. cylindrical roller bearings

3. Among the following four kinds of couplings, the ones that can compensate the relative displacement of two shafts, reduce impact and absorb vibration are.

A. Flanged coupling B. Toothed coupling

C. Universal coupling D. Elastic sleeve pin coupling

4. In the hinged four-bar mechanism, the relationship between the transmission angle and the pressure angle of the mechanism is as follows.

A.B. C. D。

5. For ordinary bolt connection, when the nut is tightened, the load on the bolt is.

A. tension B. torque C. pressure D. tension and torque

True or false (type "V" correctly and "X" wrongly. 65438+ 0 points for each small question, a total of 8 points) Third, judge to mention X X V X X X X X

1. In the hinged four-bar mechanism, when the sum of the lengths of the shortest bar and the longest bar is greater than the sum of the lengths of the other two bars, it is a double crank mechanism. ( )

2. In the cam mechanism, the greater the radius of the base circle, the greater the pressure angle. (

3. In Ping Jian connection, both sides of Ping Jian are working faces. ( )

4. The standard module of helical cylindrical gear is the big end module. ( )

5. The elastic sliding of the belt drive is caused by the overload of the drive. ( )

6. The stress cycle characteristic of bending stress of rotating shaft is fluctuating cyclic variable stress. ( )

7. The centripetal thrust bearing can bear radial and axial loads. ( )

8. Disc friction clutch transmits torque through friction torque generated between contact surfaces of driving and driven friction discs. (

4. Question and answer (3 points for each small question, 9 points in total)

1. Try to describe the basic law of tooth profile meshing.

2. Please describe the locking method of threaded connection.

3. Try to analyze the factors that affect the bearing capacity of belt drive? Fourth, question and answer.

1. The so-called basic law of tooth profile meshing means that the common normal of a pair of tooth profiles meshing at a plane contact point must intersect with the connecting line of two gears at the corresponding node C, and it is inversely proportional to the angle of the gears.

2. The locking methods of threaded connection can be divided into friction locking, mechanical locking and screw pair locking according to the working principle.

Friction locking includes: spring washer, double nut, oval self-locking nut and transverse cutting nut.

Mechanical locking includes: cotter pin and slot nut, stop washer, round nut stop washer and series of steel wires.

Anti-loosening of damaged thread pairs includes punching method, end welding method and bonding method.

3. Initial tension Fo? Angle a? Friction coefficient f? Q is the mass per unit length of the belt? Velocity v

Verb (abbreviation of verb) analysis and judgment (total 12 points)

1. In the hinged four-bar mechanism, mm, mm and mm are known. Try to judge the type of this mechanism and give the basis for judgment. (6 points for this question) Question 5, 1 number

2. The developed two-stage helical cylindrical gear transmission is shown in the figure, and the I axis is the input shaft. As shown in the figure, the rotation direction of pinion 1 and the rotation direction of teeth of gears 1 and 2 are known. In order to offset part of the axial force on the intermediate shaft II, determine the tooth rotation direction of the helical gear 3 as far as possible, and mark the circumferential force and axial force on gears 2 and 3 in the figure. (6 points for this question) Questions 5, 3 Figure 5, analysis and judgment questions

1. Solution: The four bars of this four-bar mechanism satisfy the bar length condition.

Lab+Lad《 Lbc+Lcd

According to the title, the mechanism takes the adjacent side of the shortest bar as the frame, so it is a crank-rocker mechanism.

2. Solution:

1) 3rd gear right-handed.

2) The stress direction is as shown in the figure.

Six, calculation problems (36 points)

1. Calculate the degrees of freedom of the following mechanisms and indicate whether there are composite hinges, virtual constraints or local degrees of freedom (3 points for each small question, 6 points in total).

Title six. 1 chart

2. The known gear train is shown in Figure 2. ,, and then rotate clockwise. Find the number of revolutions and the direction of rotation of the bar system H (this question 10)

3. For the pressure vessel as shown in the figure, the vessel cover and the cylinder are connected by six ordinary bolts. According to the tightness requirements of the connection, the residual pre-tightening force of each bolt is f "=1.6f, and f is the working tension of a single bolt. If the yield limit N/mm2 of bolt material is selected, try to calculate the required bolt diameter when the safety factor S=2. (This is entitled 10) Questions 6 and 2. Questions 6 and 3.

4. Reverse installation of a pair of angular contact ball bearings (wide side reverse installation). Known: radial force, external axial force, direction as shown in the figure, try to find the axial force of two bearings. (Note: internal axial force). (This question 10)

Question 6, Figure 4, Calculation problem

1.a) solution: f = 3n-2pl-ph.

=3*5-2*7-0

= 1

This problem has a compound hinge.

Remarks: This topic consists of 5 components and 4 lower pairs.

B) solution: f = 3n-2pl-ph.

=3*4-2*5- 1

= 1

In this problem, the roller is a local degree of freedom.

2.

Solution: The planetary gear train consists of 5-3-6-4.

i54H=n5-nH/n4-nH =-Z3*Z4/Z5*Z6

Because 1-2-5 constitutes a fixed axis gear train.

I 12 = n 1/N2 = n 1/n5 = Z2/z 1

So n5 = 450 rpm.

Substitute n4 = 0 and n5 = 450r rpm into the above formula.

get

NH = 5.55r rpm

This shows that the rotation direction of the pull rod H is the same as that of the gear 1.

3.

Solution:

For a single bolt, Q = q'+f = 2.6f

Q*Z=S*P*A

2.6F*6=2*3. 14*D2/4

Get f = 2264.4 n.

[σ]= 300/2 = 150 N/mm

So d 1 is obtained from the formula, and d1=15.438+0 mm.

The diameter of the bolt is16mm.

You can change the subject.

Vii. Structural problems (10 score)

The following figure shows the combined structure of helical gear, shaft and bearing. Gears are lubricated with oil, and bearings are lubricated with grease. Write the serial number, list the design errors in the drawings, and point out the reasons for the design errors. (Note: No correction is required)

Question 7. Figure 7. Question 7

1. Without gaskets, the stroke system of the bearing cannot be adjusted.

2. The shoulder is too high to remove the bearing.

3. The gear is lubricated with oil, and the bearing is lubricated with grease, but there is no oil baffle.

4. The length of the shaft sleeve should be less than the length of the hub.

5. Two keyways on the same shaft should be arranged on the same bus.

6. The sleeve cannot fix the gear (over-positioning)

7. The sleeve should be lower than the bearing outer ring.

8. The bearing end cover should be sealed with the corresponding shaft section, and should not be in contact with the shaft, and there should be a gap.

9. The coupling has no axial fixed point, and the gap with the end cover is too small, so it is easy to contact.

10. There should be a gap between the top of the key and the hub.