ADVANCED TECHNICIANS COURSE BRAKE SYSTEM

BRAKE SYSTEM HINO

1. ADVANCED
TECHNICIAN'S COURSE
6. BRAKE SYSTEM
OVERSEAS SERVICE DEPARTMENT
HINO MOTORS, LTD

2. 1. Structure and Function
1) Brake systemService brake Braking control® Booster ®
Braking force
transmitting part
Hydraulic brake Master cylinderOil Not equipped OilWheel cylinder
Equipped with booster Vacuum servo or
(vacuum servo/air servo)Master cylinderOil air servo OilWheel cylinder
Air over hydraulic brakeBrake valveAir
Air servo + relay
valve OilWheel cylinder
Full air brake Brake valve
Air (relay valve), Air
brake chamber S cam

3. HYDRAULIC AIR BOOSTER
RESERVOIR
TANK
SAFETY
CYLINDER
MASTER
CYLINDER
AIR COMPRESSOR
WHEEL CYLINDER
BRAKE SHOE
AIR MASTER
AIR TANK
HYDRAULIC VACUUM BOOSTER
RESERVOIR
TANK
SAFETY
CYLINDER
MASTER
CYLINDER
VACUUM TANK
HYDROMASER
WHEEL CYLINDER
BRAKE SHOE

4. AIR OVER HYDRAULIC BOOSTER
AIR COMPRESSOR
AIR TANK
BRAKE MASTER
RESERVOIR TANK
BRAKE VALVE
BRAKE SHOE
WHEEL CYLINDER
AIR BRAKE
BRAKE SHOE
CAM SHAFT
RELAY VALVE
BRAKE VALVE
BRAKE CHAMBER
AIR COMPRESSOR
AIR TANK

5. (1)Brake valve

6. (2)Brake booster(air over type)
When Not Operating When Operating
PUSH ROD
To wheel
cylinder
POWER PISTON
HYDRAULIC PISTON
RETURN SPRING
RELAY VALVE

7. (3)Relay valve
From brake valve
To air cylinder
From air tank
When operating
When released
When pressure is balanced
Exhaust

8. (4)Air compressor
SUCTION DELIVERY UNLOADER
From
Pressure
regulatorTo air tank (Air dryer)

9. (5)Pressure regulator
Adjust screw
Spring
Piston
Valve
Filter
Rod

10. 2) Brake unit
(1)Brake types
Leading/trailing-shoe brake Two-leading-shoe brake
(single action type)
Two-leading-shoe brake
(dual action type)
Duo servo brake

11. 0
2
4
6
8
10
0.1 0.2 0.3 0.4 0.5
Disk brake
Duo servo
Two-leading-
shoe brake
Leading/trailing-
shoe brake
Drum
Friction coefficient
Brake efficacy coefficient

12. 2. Troubleshooting
1. Procedure for Investigating Service Brake Failure
1) Foreword
Maximum braking force
Friction force between the tires and the road surface

13. 2) Understanding and confirming trouble phenomena
(1) Running conditions when trouble occurred
(2) Braking conditions
(3) Load conditions
(4) Frequency of occurrence
(5) Other
What were the road conditions?

14. 3) Vehicle check prior to investigation of trouble
(1) Wheel check
(2) Brake pedal check
(3) Brake fluid check
(4) Air pressure check

15. 2. Riding Comfort
1) Outline
Brake pull
Left-and right-side braking action is unbalanced
Lock
Left wheel
Right wheel
Braking force(kg)
Angle of depressed pedal

16. 2) Trouble Causes Chart
Brake unit (lining)Tires
Brake pull
Use conditions
Brake unit
Piping
Lining friction coefficient
disparity
Left-and right-side difference
in vehicle weight
Severe use of brakes
Road conditions
Entry of foreign substance in
gap between drum and lining
Faulty drum degree of roundness
Excessive drum wear
Rusted or damaged drum
sliding surface
Faulty brake shoe operation
Brake shoe deformation
Faulty wheel cylinder and
piston operation
Broken or damaged return spring
Unequal air pressure
Unequal wear
Uneven tread pattern
Air pipe clogging
Oil pipe clogging
Faulty drum and lining gap
Faulty lining contact
Lining damage

17. 3) Causes of trouble
(1) Faulty lining contact
NormalFaulty
Edge contact Center contact

18. (2) Lining damage
450~
500ºC

19. (3) Lining friction coefficient disparity
Temperature(ºC)
(µ)
Over-Recovery

20. (4) Faulty brake shoe operation
Wheel cylinder
Brake lining
Brake shoe
Return spring

21. (5)Rusted or damaged drum sliding face
(6)Excessive drum wear
Thermal crack Heat spot Scoring

22. 4) Use conditions
(1) Left-and right-side difference in vehicle weight
Left-and right-side difference in vehicle weight
Brake pull
Heavy wheel weight
Lock

23. (2) Severe use of brakes
Excessive use of brakes
Brake fade
Difference in µ value between the left-and right-side linings
Brake pull
Brake fade
Friction heat Vapor lock

24. < Reference >
12345678910
150
200
250
Water content (%)
Boiling point (ºC)
Brake Fluid Water Content and Boiling Point
(Effect of DOT-3-equivalent brake fluid)

25. 5) Grasping and confirming trouble phenomena
(1)Driving conditions
(2)Braking conditions
(3)Load conditions
(4)Frequency of occurrence
(5)Other

26. 3. Faulty Braking
1) Trouble phenomena
Big pedal stroke

27. 2) Trouble Causes Chart
Faulty braking
Control valve Air replenishment and air piping
Plugged (crushed) air pipe
Air leak
Faulty relay valve
function
Faulty brake booster
function
Air system freeze-up
Vapor lock
Overloading
Faulty pressure regulator
function
Faulty air compressor
function
Faulty brake valve
function
Fade
Severe use of brakes
Use conditions
Brake fluid-related causesCauses peculiar to
vacuum servo brake
Brake unit

28. Faulty braking
Insufficient pedal height
Large master cylinder push
rod play
Faulty master cylinder cap
Causes peculiar to
vacuum servo brake
Faulty hydromaster
Clogged air cleaner
Faulty vacuum check
valve
Faulty vacuum pump
Crushed or damaged
vacuum hose pipe
Vacuum system leakage
Faulty sliding of safety
cylinder piston
Large gap between drum
and lining
Using brake past lining use
limit
Faulty lining contact
Using lining with low friction
coefficient
Overheated lining
Soiled lining surface; presence
of foreign substance
Excessively smooth lining
surface
Excessively smooth drum
sliding surface
Rough drum sliding surface
Insufficient brake
fluid quantity
Fluid leak from
pipe hose
Fluid leak from
wheel cylinder
Entry of air into
fluid pressure
system
Brake booster
interior fluid
leak
Brake fluid-related causes
Brake unit

29. 3) Causes of trouble
(1) Air system
[Air compressor]
[Pressure regulator]
Idling : about 10 minutes
Full speed : about 3 minutes
7.08.5kg/cm²
8.5kg/cm²0

30. [Air leak]
Brake fluid piping
Regular supply
After operation

31. (2) Hydraulic system
[Oil leakage from piping]
Brake fluid piping
Brake air piping

32. [Faulty piston cup]
•Damaged or cracked cup lip or base.
•Rusted or damaged cylinder wall
•Swollen or contracted cup
•Invasion of foreign substance
piston
Piston cup

33. [Air entry]
•Air suction from the wheel cylinder
•Master cylinder secondary cup deterioration
•Bubbles produced by vapor lock
•Incomplete air bleeding work

34. (3) Control valve-related causes
[Brake booster function]Characte
-ristics
Booster reference
parts number Initial pressure (kg/cm²)Fluid pressure (kg/cm²)
Residual
pressure(mmHg)
A 44640-1211 0.4±0.15 157±7 Must be 0
44640-1242 0.4±0.15 157±7 At least 600
B 44640-1261 0.6±0.15 153±7 At least 600
44640-1291 0.6±0.15 153±7 Must be 0

35. 0.40.15
0.60.15
7
1577
1537
Relay valve signal pressure (kg/cm²)
Fluid pressure (kg/cm²)
A
B
Brake booster Characteristics Diagram

36. [Brake valve function]
5 10 15 200
1
2
3
4
5
6
7
0.2
0.15
151. 5
242
181. 5
3.4
0.3
7
5.4
0.4
41
Angle of depressed pedal(q)
Brake valve outlet pressure(kg/cm²)
(Tank pressure: 7kg/cm²)
Operating Characteristics Diagram

37. (4) Wheel unit
·Large gap between lining and drum
·Faulty lining contact
·Overheated lining
·Soiled lining surface; presence of foreign substance
·Excessively smooth lining surface
·Excessively smooth drum sliding surface
·Rough drum sliding surface
Center contact

38. (5) Use conditions
[Overloading]
Pressurizing force (P)
Friction Coefficient (µ)
Braking force (F)

39. 4. Premature Brake Lining Wear
1) Outline
Basic causes
of lining wear
Frequent use
of brakes
G.V.W.
Vehicle's initial
braking velocity

40. 2) Trouble Causes Chart
Premature Brake Lining Wear
Causes other
than brake drag
Brake dragCauses peculiar to vacuum
servo brakes
Premature wear on all wheels
Little play in master
cylinder servo brakes
Swelling of master
cylinder piston cup
Faulty master cylinder
piston return
Faulty hydromaster
return
Faulty safety cylinder
piston return
Unsuitable lining material
Faulty brake cooling
Foreign substance on
friction surface
Excessive use of brakes
Excessive use of brakes
at high speeds
Overloading
Faulty brake pedal play
Faulty brake valve return
Faulty relay valve return
Faulty brake booster
return

41. Premature wear on
specific wheel(s)
Premature Brake Lining Wear
Drum sliding surface roughness
Excessive drum wear
Different materials used
between axles
Reduced drum/lining gap
Wheel bearing play
Fault brake shoe return
Faulty wheel cylinder piston
return
Bent or damaged brake shoe
return spring
Eccentric drum
Brake dragCauses other
than brake drag

42. 3) Causes of trouble
Use conditions
of the brakes
Premature Brake
Lining Wear
1.Lining temperature
2.
3.
4.
5.
100 200 300
2
4
6
8
10
12
14
x10
-7
Temperature (ºC)
Wear rate(cm³/kg•m)

43. 4) Premature wear on all wheels due to brake drag
(1) Faulty brake pedal free play
(2)Faulty brake valve return
Pedal height
Pedal angle

44. (4) Faulty check valve functioning
(3) Faulty brake booster return
•Faulty sliding of air piston and air cylinder
•Bent or damaged air piston return spring
•Faulty sliding of oil piston and cylinder
•Faulty check valve functioning
Check valve
Air piston
Oil piston
Return spring

45. 5) Premature wear on all wheels due to cause other than brake drag
(1) Unsuitable lining material
(2) Foreign substance on friction surface
Wear
Grabbing

46. (3) Excessive use of brakes at high speeds
W = Gross vehicle weight
V = Vehicle speed
g = acceleration of gravity (9.8mm/sec²)2
V×
g
W
×
2
1
=energy Kinetic
30507090
0.5
1.0
5.0
10.0
x10
-3
Initial speed(km/H)
Wear volume

47. (4) Overloading
Load
Wear volume
Increasing of
lining temperature

48. (5) Premature wear on specific wheels
Drum sliding surface roughness
Excessive drum wear
Different materials used between axles
Reduced drum/lining gap
Wheel bearing play
Fault brake shoe return
Faulty wheel cylinder piston return
Bent or damaged brake shoe return spring
Eccentric drum
Brake drag
Causes other
than brake drag

49. 5. Brake Judder
1) Trouble phenomena
Abnormal vibration

50. 2) Trouble Causes Chart
Lining
High
-
speed brake judder
Other causes
Drum rubout factors
Faulty hub installation face flatness
Foreign substance on hub
installation face
Excessively tightened hub nut
Eccentric drum
Faulty installation on hub
Foreign substance on hub
installation face
Faulty hub installation face flatness
Faulty contact
Large friction coefficient
Hub bearing play
Suspension system resonance
Amplification factors
DrumDisk wheel

51. 3) Mechanism by which high-speed judder occurs
Fluctuating brake torque is produced
Brake vibration resonates in tire
rotating direction and is amplified
Vibration is transmitted to the cab
Drum sliding face rubout

52. 4) Confirming extent of judder
(1) Speed
(2) Cold or warm
(3) Steering or Cab
(4) laden or at normal times
(5) Front or Rear

53. 5) Causes of trouble
High-Speed brake judder
1. Vibration of the front drum sliding faces
2.
3.
4.
5.
Vibration of the front drum sliding faces
less than 0.1mm
0.15 mm
Medium-duty vehicle
Heavy-duty vehicle

54. [Measuring drum runout]
Lining
Magnet stand
Lining wear inspection hole
Sliding face : about 2mm

55. [Causes of drum runout]
[1] Faulty disk wheel, drum, or hub installation face
[2] Excessively tightened hub nut
[3] Faulty installation on hub
Matching face
Improved flatness accuracy

56. 5) Drum runout measuring procedure and measures
[1]Measure drum runout

57. 5) Drum runout measuring procedure and measures
[1]Measure drum runout
0.1 or
less
Replace with a low µ lining
Greater than 0.1

58. 5) Drum runout measuring procedure and measures
[1]Measure drum runout
0.1 or
less
Replace with a low µ lining
[2]Measure disk wheel rubout
With tireWithout tire
20 ~ 25mm
30 ~35mm
Greater than 0.1

59. 5) Drum runout measuring procedure and measures
[1]Measure drum runout
Greater than 0.1
0.1 or
less
Replace with a low µ lining
[2]Measure disk wheel rubout
0.1 or
less
Check disk wheel installation face
With tireWithout tire
20 ~25mm
30 ~35mm

60. 5) Drum runout measuring procedure and measures
[1]Measure drum runout
0.1 or
less
Replace with a low µ lining
[2]Measure disk wheel rubout
0.1 or
less
Check disk wheel installation face
Normal Abnormal
Repair
Install a high-accuracy disk wheel
Greater than 0.1
Greater than 0.1

61. 5) Drum runout measuring procedure and measures
[1]Measure drum runout
0.1 or
less
Replace with a low µ lining
[2]Measure disk wheel rubout
0.1 or
less
Check disk wheel installation face
Install a high-accuracy disk wheel
Greater than 0.1
Greater than 0.1
[3]Repair the hub and drum assembly rubout
Normal Abnormal
Repair

62. 5) Drum runout measuring procedure and measures
[1]Measure drum runout
0.1 or
less
Replace with a low µ lining
[2]Measure disk wheel rubout
0.1 or
less
Check disk wheel installation face
Install a high-accuracy disk wheel
Greater than 0.1
Greater than 0.1
[3]Repair the hub and drum assembly rubout
Normal Abnormal
Repair
Change the hub
and drum phase

63. 5) Drum runout measuring procedure and measures
[1]Measure drum runout
0.1 or
less
Replace with a low µ lining
[2]Measure disk wheel rubout
0.1 or
less
Check disk wheel installation face
Install a high-accuracy disk wheel
Greater than 0.1
Greater than 0.1
[3]Repair the hub and drum assembly rubout
Normal Abnormal
Repair
Change the hub
and drum phase
Cannot be adjusted

64. Install a high-accuracy disk wheel
[3]Repair the hub and drum assembly rubout
Change the hub
and drum phase
Cannot be adjusted
Grindthedrumslidingfaces
withthehubanddrum
assembledorwiththehub,
drum,anddiskwheel
assembled

65. [3]Repair the hub and drum assembly rubout
Change the hub
and drum phase
Cannot be adjusted
Grindthedrumslidingfaces
withthehubanddrum
assembledorwiththehub,
drum,anddiskwheel
assembled
[4]Measure the disk wheel assembly rubout

66. [3]Repair the hub and drum assembly rubout
Change the hub
and drum phase
Cannot be adjusted
[4]Measure the disk wheel assembly rubout
0.1 or
less
Test drive
Greater than 0.1
Grindthedrumslidingfaces
withthehubanddrum
assembledorwiththehub,
drum,anddiskwheel
assembled

67. [3]Repair the hub and drum assembly rubout
Change the hub
and drum phase
Cannot be adjusted
[4]Measure the disk wheel assembly rubout
0.1 or
less
Test drive
Replace with a high-accuracy disk wheel
Greater than 0.1
Grindthedrumslidingfaces
withthehubanddrum
assembledorwiththehub,
drum,anddiskwheel
assembled

68. Unsatisfied
[3]Repair the hub and drum assembly rubout
Change the hub
and drum phase
Cannot be adjusted
[4]Measure the disk wheel assembly rubout
0.1 or
less
Test drive
Replace with a high-accuracy disk wheel
Greater than 0.1
Grindthedrumslidingfaces
withthehubanddrum
assembledorwiththehub,
drum,anddiskwheel
assembled

69. Replace the lining with a low µ lining
Unsatisfied
[3]Repair the hub and drum assembly rubout
Change the hub
and drum phase
Cannot be adjusted
[4]Measure the disk wheel assembly rubout
0.1 or
less
Test drive
Replace with a high-accuracy disk wheel
Greater than 0.1
Grindthedrumslidingfaces
withthehubanddrum
assembledorwiththehub,
drum,anddiskwheel
assembled