  We report a theoretical study of the quantized spin pump in a traditional
two-parameter quantum pump device that is based on the helical edge states of a
quantum spin Hall insulator. By introducing two time-dependent magnetizations
out of phase as the pumping parameters, we found that when the Fermi energy
resides in the energy gap opened by magnetization, an integer number of charges
or spins can be pumped out in a pumping cycle and ascribed to the possible
topological interface state born in between the two pumping potentials. The
quantized pump current can be fully spin-polarized, spin-unpolarized, or pure
spin current while its direction can be abruptly reversed by some system
parameters such as the pumping phase and local gate voltage. Our findings may
shed light on generation of a quantized spin pump.
