Bosch Distributor Type Diesel Fuel Injection Pumps Yellow Book wrote:Page 55
Control modules for distributor injection pumps Mechanical torque-control modules
Cold-start compensation
The cold-start compensation device improves the diesel engine's cold-start response by advancing the start of delivery. This feature is controlled by a driver-operated cable or by an automatic temperature-sensitive control device (Fig 13).
Mechanical cold-start accelerator (KSB) on roller ring
Design
The KSB is mounted on the pump's housing. In this assembly, a shaft (Fig 12, Pos 12) connects the stop lever (Fig 13,
Pos 3) with an inner lever featuring an eccentrically mounted ball head (3). This lever engages with the roller ring. The stop lever's initial position is defined by the full-load stop and the leg spring (13). The control cable attached to the upper end of the stop lever serves as the link to the adjustment mechanism which is either manual or automatic.
The automatic adjuster is installed in a bracket on the distributor injection pump (Fig 13), while the manual adjustment cable terminates in the passenger compartment.
There also exists a version in which the adjuster intervenes through the timing plunger.
Operating concept
The only difference between the manual and automatic versions of the cold-start accelerator is the external control mechanisms. The key process is always the same. When the control cable is not tensioned, the leg spring presses the stop lever against its full-load stop. Both ball head and roller ring (6) remain in their initial positions. Tension on the control cable causes the stop lever, shaft and inside lever to turn with the ball head.
This rotation changes the position of the roller ring to advance the start of delivery. The ball head engages a vertical groove in the roller ring. This prevents the timing plunger from advancing the start of delivery further before a specified engine speed is reached
[1].
When the driver activates the cold-start acceleration device (KSB timing device), a position shift of approximately 2.5° camshaft (b)
[2] remains, regardless of the adjustment called for by the timing device (Fig 14a).
Fig 12
1 Lever
2 Adjustment window
3 Ball head
4 Vertical groove
5 Pump housing
6 Roller ring
7 Rollers in roller ring
8 Timing plunger
9 Pin
10 Sliding block
11 Timing spring
12 Shaft
13 Leg spring
Fig 13 Mechanical cold-start accelerator, adjuster with automatic control (cold position)
1 Retainer
2 Bowden cable
3 Stop lever
4 Leg spring
5 Control lever KSB
6 Adjuster dependent on coolant and ambient temperatures
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Control modules for distributor injection pumps Mechanical torque-control modules
In cold-start systems with automatic control, the actual increment depends on engine temperature and/or ambient temperature.
Automatic adjustment relies on a control mechanism in which a temperature-sensitive expansion element translates variations in engine temperature into linear motion.
This arrangement's special asset is that it provides the optimum start of delivery and start of injection for each individual temperature.
Various lever layouts and actuation mechanisms are available according to the mounting side and rotational direction encountered in individual installation environments.
Temperature-controller idle-speed increase (TLA)
The temperature-controlled idle-speed increase, which is combined with the automatic KSB, is also operated by the control mechanism (Fig 15). The ball pin in the extended KSB control lever presses against the rotational-speed control lever to lift it from the idle-speed stop screw when the engine is cold. This raises the idle speed to promote smoother engine operation. The KSB control lever rests against its full-load stop when the engine is warm. This allows the rotational-speed control lever to return to its own full-load stop, at which point the temperature-controlled idle-speed increase system is no longer active.
Hydraulic cold-start accelerator [3]
There are inherent limits on the use of strategies that shift the timing plunger to advance start of injection. Hydraulic start of lnjection advance applies speed-controlled pressure in the pump's inside chamber to
the timing plunger. The system employs a bypass valve in the pressure-control valve to modify the inner chamber's automatic pressure control, automatically increasing internal pressure to obtain additional advance extending beyond the standard advance curve.
Design
The hydraulic cold-start accelerator comprises a modified pressure-control valve (Fig. 17, Pos. 1), a KSB ball valve (7), an electrically heated expansion element (6) and a KSB control valve (9).
Fig 14 Effects of mechanical cold-start accelerator KSB
a Injection adjusted by timing device
b Minimum adjustment (approximately 2.5° camshaft)
[2]
Fig. 15 Mechanical cold-start accelerator (automatic) with temperature-controlled idle-speed increase
1 Rotational-speed control lever
2 Ball pin
3 Control lever KSB
4 Full-load stop
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Control modules for distributor injection pumps Mechanical torque-control modules
Operating concept
The fuel supplied by the supply pump (5) flows through the distributor injection pump's inner chamber and to the end of the timing plunger (11), which compresses the return spring (12) and shifts position in response to the inner chamber pressure to vary the start of injection. The pressure-control valve controls the pressure in the inner chamber, raising pressure for greater delivery quantity as engine speed increases (Fig. 16).
The throttle port in the pressure-control valve's plunger (Fig 17 Pos 3) supplies the added pressure that allows the KSB to provide the forward offset in start of injection advance (Fig 16, blue curve). This conveys an equal pressure to the spring side of the pressure-control valve. The KSB ball valve, with its higher pressure setting, regulates activation and deactivation (with the thermal element) while also serving as a safety release. An adjusting screw on the integrated KSB control valve is available for adjusting KSB operation to a specific engine speed. Pressure from the supply pump presses the KSB control-valve plunger (10) against a spring. A damping throttle inhibits pulsation against the control plunger. The KSB pressure curve is controlled by the timing edge on the control plunger and the opening
on the valve holder. The spring rate on the control valve and the control port configuration can be modified to match KSB functionality to the individual application. The ambient temperature will act on the expansion element to open the cold-start accelerator ball valve before starting the hot engine.
Fig 16 Hydraulic cold-start accelerator (operation)
1 Start of delivery advanced
Fig 17 Hydraulic cold-start accelerator
1 Pressure-control valve
2 Valve plunger
3 Throttled bore
4 Inner chamber pressure
5 Vane-type supply pump
6 Electrically heated expansion element
7 Ball valve KSB
8 Fuel drains without pressure
9 Adjustable KSB control valve
10 Control plunger
11 Timing device
12 Return spring