detecting the time of hydraulic pressure setup as a return signal, this important
criterion is one of missile launch and control conditions.
The establishment of hydraulic pressure cannot be achieved by only improving
the starting power of gas generator. Hydraulic pressure is ultimately determined by
the load, so the rapid establishment of hydraulic pressure is to take measures on the
hydraulic load.
A loading valve is used in EHPU system, which is directly connected to the
outlet of hydraulic pump. The function of loading valve is mainly embodied in the
starting section of EHPU. When EHPU starts, the oil is fed into the oil inlet end of
loading valve. When the oil inlet pressure is lower than the set spring force, the
guide rod cannot drive the large valve core to move to the right. At this time, the oil
inlet and return routes are not fully connected. Oil enters the return routes through
the valve sleeve and the large spool, through the orifice throttling of the small spool,
and through the flow groove between the valve sleeve and the shell. Therefore,
when starting, the oil resistance is very large, which makes the valve inlet pressure
established quickly. When the pressure at the inlet end rises, the small spool is
attached to the left cap under the action of pressure, and the guide rod assembly
drives the large spool to move to the right under the action of pressure difference at
both ends. When the big spool moves to a certain distance, the valve opens, the
intake and return oil routes are fully connected, the resistance of the oil routes
decreases, the flow rate increases, the loading valve reaches a certain pressure at this
time, and the flow rate reaches the rated value.
The characteristic curve of the loading valve is shown in Fig. 9.56. Curve p 1 is
pressure–flow characteristic curve p 1 À Q before loading valve, curve p 2 is pressure–flow characteristic curve after loading valve, curve p 3 is flow characteristic
curve of pressure difference p 1 À p 2
ð
Þ , and Q before and after loading valve.
The working characteristic of the loading valve in the system is the differential
pressure–flow characteristic shown in curve p 3 . From the curve, when EHPU starts,
the pressure difference before and after loading valve is larger, the pressure before
loading valve is larger than that after loading valve, and the corresponding flow rate
Fig. 9.56 Characteristic
curve of loading valve
9.5 Starting Characteristics of Electronic and Hydraulic Power Unit
155
criterion is one of missile launch and control conditions.
The establishment of hydraulic pressure cannot be achieved by only improving
the starting power of gas generator. Hydraulic pressure is ultimately determined by
the load, so the rapid establishment of hydraulic pressure is to take measures on the
hydraulic load.
A loading valve is used in EHPU system, which is directly connected to the
outlet of hydraulic pump. The function of loading valve is mainly embodied in the
starting section of EHPU. When EHPU starts, the oil is fed into the oil inlet end of
loading valve. When the oil inlet pressure is lower than the set spring force, the
guide rod cannot drive the large valve core to move to the right. At this time, the oil
inlet and return routes are not fully connected. Oil enters the return routes through
the valve sleeve and the large spool, through the orifice throttling of the small spool,
and through the flow groove between the valve sleeve and the shell. Therefore,
when starting, the oil resistance is very large, which makes the valve inlet pressure
established quickly. When the pressure at the inlet end rises, the small spool is
attached to the left cap under the action of pressure, and the guide rod assembly
drives the large spool to move to the right under the action of pressure difference at
both ends. When the big spool moves to a certain distance, the valve opens, the
intake and return oil routes are fully connected, the resistance of the oil routes
decreases, the flow rate increases, the loading valve reaches a certain pressure at this
time, and the flow rate reaches the rated value.
The characteristic curve of the loading valve is shown in Fig. 9.56. Curve p 1 is
pressure–flow characteristic curve p 1 À Q before loading valve, curve p 2 is pressure–flow characteristic curve after loading valve, curve p 3 is flow characteristic
curve of pressure difference p 1 À p 2
ð
Þ , and Q before and after loading valve.
The working characteristic of the loading valve in the system is the differential
pressure–flow characteristic shown in curve p 3 . From the curve, when EHPU starts,
the pressure difference before and after loading valve is larger, the pressure before
loading valve is larger than that after loading valve, and the corresponding flow rate
Fig. 9.56 Characteristic
curve of loading valve
9.5 Starting Characteristics of Electronic and Hydraulic Power Unit
155