  Strong coupling effects on the upper critical fields $H_{c2}$ along the
c-axis in the noncentrosymmetric heavy fermion superconductors near quantum
criticality CeRhSi$_3$ and CeIrSi$_3$ are examined. For sufficiently large
spin-orbit interactions due to the lack of inversion symmetry, $H_{c2}$ is
mainly determined by the orbital depairing effects. From microscopic
calculations taking into account the strong spin fluctuations, we show that
$H_{c2}$ is extremely enhanced as the system approaches the quantum critical
point, resulting in $H_{c2}\sim 30$T even in the case with the low transition
temperature $T_c(H=0)\sim 1$K, which well explains the huge $H_{c2}$ observed
in the recent experiments. Our results reveal intrinsic and universal
properties common to strong coupling superconductivity caused by spin
fluctuations near quantum criticality.
