设$\stackrel{\rightharpoonup }{e_1},\stackrel{\rightharpoonup }{e_2}$为单位向量非零向量$\stackrel{\rightharpoonup }{b}=x\stackrel{\rightharpoonup }{e_1}+y\stackrel{\rightharpoonup }{e_2},x,y\in R$.若$\stackrel{\rightharpoonup }{e_1},\stackrel{\rightharpoonup }{e_2}$的夹角为${30}^{°}$,则$\frac{\left|x\right|}{\left|\stackrel{\rightharpoonup }{b}\right|}$的最大值等于.